Ionis Pharmaceuticals Inc: Form 10-K for the period ended Dec 31, 2025

Overview

For three decades, we have invented medicines that bring better futures to people with serious diseases. As a pioneer in RNA-targeted medicines with a deep understanding of disease biology and an industry-leading drug discovery technology, we are driven to deliver innovative, life-changing advances for patients.

In the last year, we delivered on our strategy to create accelerating value for all our stakeholders. With two independent commercial launches now underway, we transitioned into a fully integrated commercial-stage biotechnology company. We currently have seven marketed medicines to treat serious diseases: TRYNGOLZA (olezarsen), DAWNZERA (donidalorsen), WAINUA (eplontersen), SPINRAZA (nusinersen), QALSODY (tofersen), TEGSEDI (inotersen) and WAYLIVRA (volanesorsen).

Marketed Medicines

• TRYNGOLZA is approved in the United States, or U.S., as an adjunct to diet to reduce triglycerides in adults with familial chylomicronemia syndrome, or FCS, and is approved in the European Union, or EU, for patients with genetically confirmed FCS. TRYNGOLZA is also approved in Canada. TRYNGOLZA is the first-ever FDA-approved treatment that significantly and substantially reduces triglyceride levels in adults with FCS and provides clinically meaningful reduction in acute pancreatitis, or AP, events when used with an appropriate diet (≤20 grams of fat per day). We are independently commercializing TRYNGOLZA in the U.S.
• DAWNZERA is approved in the U.S. for prophylaxis to prevent attacks of hereditary angioedema, or HAE, in adult and pediatric patients 12 years of age and older and is approved in the EU for the routine prevention of recurrent attacks of HAE in the same age group. DAWNZERA is the first and only approved RNA-targeted prophylactic therapy for HAE. DAWNZERA has the potential to offer durable efficacy, a favorable safety and tolerability profile, and the longest available dosing interval. We are also independently commercializing DAWNZERA in the U.S.
• WAINUA is approved in the U.S., EU, China and numerous other countries for the treatment of the polyneuropathy of hereditary transthyretin-medicated amyloidosis, or ATTRv-PN, in adults. WAINUA is the only approved medicine for the treatment of ATTRv-PN that can be self-administered via an auto-injector. We and AstraZeneca are co-developing WAINUA globally and co-commercializing WAINUA in the U.S. AstraZeneca has exclusive rights to commercialize WAINUA outside of the U.S.
• SPINRAZA is a global market leader for the treatment of patients with spinal muscular atrophy, or SMA. Our partner, Biogen, is responsible for commercializing SPINRAZA worldwide.
• QALSODY is approved in the U.S., EU, China and Japan for the treatment of amyotrophic lateral sclerosis, or ALS, in adults who have a mutation in the superoxide dismutase 1, or SOD1, gene, or SOD1-ALS. QALSODY received accelerated approval from the U.S. Food and Drug Administration, or FDA, and marketing authorization under exceptional circumstances from the European Medicines Agency, or EMA. QALSODY was the first treatment approved to target a genetic cause of ALS. Our partner, Biogen, is responsible for commercializing QALSODY worldwide.
• TEGSEDI is approved in the EU, Canada and Brazil for the treatment of ATTRv-PN in adults. We currently sell TEGSEDI in Europe through our distribution agreement with Swedish Orphan Biovitrum AB, or Sobi. We and Sobi terminated our agreement for TEGSEDI in North America, after which we discontinued TEGSEDI in North America. In Latin America, PTC Therapeutics International Limited, or PTC, is commercializing TEGSEDI in Brazil and is pursuing access in additional Latin American countries through its exclusive license agreement with us.
• WAYLIVRA is approved in the EU and Brazil as an adjunct to diet in adult patients with genetically confirmed FCS and at high risk for acute, potentially fatal pancreatitis, in whom response to diet and triglyceride lowering therapy has been inadequate. We sell WAYLIVRA in Europe through our distribution agreement with Sobi. In Latin America, PTC is commercializing WAYLIVRA in Brazil for two indications, FCS and familial partial lipodystrophy, or FPL, and is pursuing access in additional Latin American countries through its exclusive license agreement with us.

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In addition to our currently marketed medicines, we are also positioned to independently launch two medicines in 2026, assuming regulatory approval. The FDA recently granted priority review of olezarsen for the treatment of severe hypertriglyceridemia, or sHTG, with an action date of June 30, 2026 under the Prescription Drug User Fee Act, or PDUFA. We are on track to launch olezarsen following anticipated approval. We also submitted the NDA for zilganersen in January 2026 and plan to launch zilganersen in the second half of 2026 for the treatment of Alexander disease, or AxD. We also have a rich innovative late- and mid-stage pipeline across our focus areas of neurology, cardiometabolic diseases and select areas of high patient needs. We currently have three wholly owned medicines in late-stage development, including obudanersen (formerly ION582) for Angelman syndrome, or AS, which we advanced into a Phase 3 study in the second quarter of 2025. Additionally, we have six partnered medicines in late-stage development. We also have additional medicines in early and mid-stage development. We delivered multiple positive data readouts in the last year from our late- and mid-stage pipeline, including positive data for olezarsen in sHTG, zilganersen in AxD, bepirovirsen in chronic hepatitis B, or CHB, obudanersen in AS and sapablursen in polycythemia vera, or PV. And we further advanced our next-generation technologies for RNA-targeted medicines, including advancing our first program using our mesyl phosphoramidate, or MsPA, backbone into clinical development.

We earned revenues of $944 million in 2025 and ended 2025 with a cash, cash equivalents and short-term investment balance of $2.7 billion that enables our continued investments to support ongoing and planned launches and to advance our wholly owned medicines in development. Our key recent achievements, combined with our independent and partnered product launches anticipated over the next two years, position us well to help millions of patients with serious diseases and deliver increasing product and royalty revenue.

Our Marketed Medicines – Bringing Value to Patients Today

TRYNGOLZA (apoC-III) – TRYNGOLZA (olezarsen) injection is an APOC-III-directed antisense medicine indicated as an adjunct to diet to reduce triglycerides in adults with familial chylomicronemia syndrome, or FCS. TRYNGOLZA lowers the body’s production of apolipoprotein C-III, or apoC-III, a protein produced in the liver that is a key regulator of triglyceride metabolism. TRYNGOLZA was approved by the FDA in December 2024 and is the first-ever FDA-approved treatment that significantly and substantially reduces triglyceride levels in adults with FCS and provides clinically meaningful reduction in AP events when used with an appropriate diet (≤20 grams of fat per day). TRYNGOLZA was also approved in the EU in September 2025 as an adjunct to diet in adult patients for the treatment of genetically confirmed FCS in September 2025. TRYNGOLA was also approved in Canada in December 2025. Our partner, Sobi, is responsible for commercializing TRYNGOLZA in countries outside of the U.S., Canada and China.

FCS is a rare, genetic, potentially life-threatening form of sHTG that prevents the body from breaking down fats and severely impairs the body’s ability to remove triglycerides from the bloodstream due to an impaired function of the enzyme lipoprotein lipase, or LPL. While healthy levels for adults are below 150 mg/dL, people with FCS often have triglyceride levels of more than 880 mg/dL and often have a history of pancreatitis. Those living with FCS have a high risk of potentially fatal AP, which is a painful inflammation of the pancreas, and chronic health issues such as fatigue and severe, recurrent abdominal pain. People living with FCS can also experience psychological and financial stress, which can significantly impact their quality of life. FCS is estimated to impact up to approximately 3,000 people in the U.S., the vast majority of whom remain undiagnosed.

TRYNGOLZA approval was based on positive data from the placebo-controlled Phase 3 Balance study in adult patients with genetically identified FCS and fasting triglyceride levels ≥880 mg/dL. In the Balance study, TRYNGOLZA demonstrated a statistically significant reduction in triglyceride levels, a substantial and clinically meaningful reduction in AP events, and a favorable safety and tolerability profile.

Prior to approval, TRYNGOLZA was granted Priority Review, Fast Track, Orphan Drug and Breakthrough Therapy designations for the treatment of FCS.

We are also developing olezarsen to treat severe hypertriglyceridemia, or sHTG. See the “olezarsen” description under the section titled, Our Innovative Late-Stage Pipeline of Ionis-Owned Investigational Medicines, below for further information on our development program for sHTG.

DAWNZERA (PKK) – DAWNZERA (donidalorsen) is a prekallikrein, or PKK, -directed antisense oligonucleotide indicated for prophylaxis to prevent attacks of hereditary angioedema, or HAE, in adult and pediatric patients 12 years of age and older. PKK plays an important role in the activation of inflammatory mediators associated with acute attacks of HAE and by reducing the production of PKK, DAWNZERA works to prevent HAE attacks. DAWNZERA was approved in the U.S. in August 2025 and in the EU in January 2026. Our partner, Otsuka Pharmaceutical Co., Ltd., or Otsuka, is responsible for commercializing DAWNZERA in Europe and Asia.

HAE is a rare and potentially life-threatening genetic condition that involves recurrent attacks of severe swelling (angioedema) in various parts of the body, including the hands, feet, genitals, stomach, face and/or throat. HAE is estimated to affect approximately 20,000 people in the U.S. and Europe.

DAWNZERA approval was based on the positive data from the placebo-controlled Phase 3 OASIS-HAE study, the Phase 3 OASISplus study and the Phase 2 study, including an OLE study, in patients with HAE. The OASIS-HAE study met its primary endpoint with a statistically significant reduction in the rate of HAE attacks and demonstrated clinically significant improvement in quality of life as measured by the Angioedema Quality of Life Questionnaire, or AE-QoL, in patients treated every four weeks and patients treated every eight weeks. The OASISplus study includes an OLE cohort and a prospective switch cohort to assess patients switching from currently available long-term prophylactic treatments to DAWNZERA. Positive results from a February 2024 data cut from the ongoing OLE cohort showed that HAE attack rates continued to improve over time and extended treatment resulted in further improved quality of life measures and high levels of disease control. In the OASISplus switch cohort, patients followed a pre-defined specific protocol to transition from their prior therapy to DAWNZERA. Results showed that patients were able to switch to DAWNZERA from prior prophylactic treatment without an increase in breakthrough attacks. Switching to DAWNZERA also reduced mean HAE attack rate and led to continued improvement in quality-of-life measures compared to baseline with prior prophylactic treatment. The majority of patients surveyed reported a preference for DAWNZERA over their previous treatment. In all of these studies, DAWNZERA demonstrated a favorable safety and tolerability profile.

The FDA and EMA granted Orphan Drug designation to DAWNZERA.

WAINUA (TTR) – WAINUA (eplontersen) injection is a transthyretin-directed antisense oligonucleotide indicated for the treatment of the polyneuropathy of hereditary transthyretin-medicated amyloidosis, or ATTRv-PN, in adults. WAINUA causes degradation of mutant and wild-type TTR mRNA through binding to the TTR mRNA, which results in a reduction of serum TTR protein and TTR protein deposits in tissues. WAINUA was approved in the U.S. in December 2023 and in the EU in March 2025. WAINUA is also approved in other markets, including the UK, Canada and China, with additional regulatory reviews underway. We and AstraZeneca are co-commercializing WAINUA in the U.S. and AstraZeneca has exclusive rest of world commercialization rights.

ATTRv-PN is a debilitating disease that leads to peripheral nerve damage with motor disability within five years of diagnosis and, without treatment, is generally fatal within a decade. ATTR is caused by the accumulation of liver-derived misfolded TTR protein in tissues, such as the heart and the peripheral nerves, causing organ damage and failure. ATTR then causes complications, leading to cardiovascular, neurological and renal diseases such as heart failure and chronic kidney disease. There are both hereditary (ATTRv) and non-hereditary (wild-type) forms of ATTR. ATTR has several phenotypes including ATTR-cardiomyopathy, or ATTR-CM, which predominantly impacts the heart, potentially leading to heart failure, and ATTR-polyneuropathy, which predominantly affects the peripheral nervous system and mixed phenotype, where patients experience symptoms of both. Worldwide, there are an estimated 10,000 – 40,000 patients with ATTRv-PN. See the “Eplontersen” description under the section titled, Our Innovative Late-Stage Pipeline of Partnered Investigational Medicines, below for further information on our development program for ATTR-CM.

FDA approval was based on the interim analysis of the open-label Phase 3 NEURO-TTRansform study in patients with ATTRv-PN. The study compared WAINUA to the historical placebo arm from the TEGSEDI (inotersen) NEURO-TTR Phase 3 study. In the interim analysis, WAINUA demonstrated a statistically significant and clinically meaningful change from baseline for the co-primary endpoints of serum TTR concentration and Neuropathy Impairment Score +7, or mNIS+7. Additionally, WAINUA demonstrated a favorable safety and tolerability profile in the NEURO-TTRansform study.

The FDA granted Orphan Drug designation to WAINUA for the treatment of ATTR.

SPINRAZA (SMN) – SPINRAZA (nusinersen) injection for intrathecal use is a survival motor neuron-2, or SMN2, directed antisense medicine indicated for the treatment of SMA in pediatric and adult patients. SPINRAZA targets the root cause of SMA by increasing the production of functional survival motor neuron, or SMN, protein. SPINRAZA is a global market leader for the treatment of patients with SMA. Higher dose SPINRAZA was approved in EU and Japan in 2025 and is currently under review in the U.S. with a PDUFA action date of April 3, 2026. Our partner, Biogen, is responsible for commercializing SPINRAZA worldwide.

SMA is characterized by loss of motor neurons in the spinal cord and lower brain stem. People with SMA have a deletion or defect in their SMN1 gene and rely on their SMN2 gene to produce functional SMN protein, which motor neurons need to maintain motor function and muscle strength. However, in untreated people the SMN2 gene can only produce approximately 10% of the SMN protein critical for motor neurons, resulting in severe and progressive loss of motor function and strength. The rate and severity of degeneration varies depending on the amount of functional SMN protein a patient can produce. Type 1, or infantile-onset, SMA is the most severe form of the disease. Type 1 SMA patients produce very little SMN protein and often progress to death or permanent ventilation by the age of 2. Patients with Type 2 or Type 3, or later-onset, SMA produce more SMN protein, but also suffer from a progressive loss of muscle strength and function and a reduced life expectancy.

SPINRAZA approval was based on efficacy and safety data from multiple clinical studies, including two randomized, placebo-controlled Phase 3 studies, ENDEAR, in patients with infantile-onset SMA, and CHERISH, in patients with later-onset SMA as well as from SHINE, an open-label extension, or OLE, study for patients with SMA who participated in prior SPINRAZA studies. Additionally, Biogen conducted the Phase 2 NURTURE study, an open-label study investigating the benefit of SPINRAZA when administered before symptom onset in patients genetically diagnosed with SMA that showed that early and sustained treatment with SPINRAZA helped participants to maintain and/or make progressive gains in motor function with most children achieving motor milestones within age-appropriate timelines and no major motor milestones were lost. SPINRAZA demonstrated a favorable safety and tolerability profile in the studies.

Biogen continues to expand the body of evidence supporting SPINRAZA’s durable efficacy and well-established safety profile to address the remaining needs of SMA patients of all ages through additional studies. These include the Phase 2/3 DEVOTE study, which evaluated a higher dose of SPINRAZA compared to the currently approved dose, the Phase 4 RESPOND study, evaluating the benefit of SPINRAZA in infants and children with a suboptimal clinical response to the gene therapy, onasemnogene abeparvovec and the Phase 3b ASCEND study evaluating the clinical outcomes and assessing the safety of a higher dose of SPINRAZA in children, teens and adults with later-onset SMA following treatment with risdiplam. The positive data generated from the DEVOTE study were the basis of the EU and Japan approvals and the regulatory submission in the U.S., which has an action date of April 23, 2026.

QALSODY (SOD1) – QALSODY (tofersen) injection for intrathecal use is an antisense medicine indicated for the treatment of ALS, in adults who have SOD1-ALS. QALSODY inhibits the production of SOD1 protein. QALSODY was granted accelerated approval in April 2023 based on reduction in plasma neurofilament light chain protein, or NfL, observed in patients treated with QALSODY. Continued approval for this indication may be contingent upon verification of clinical benefit in confirmatory trial(s). In May 2024, QALSODY was also approved in the EU under exceptional circumstances. Additionally, QALSODY was approved in China and Japan. Our partner, Biogen, is responsible for commercializing QALSODY worldwide.

SOD1-ALS is a rare, fatal, neurodegenerative disorder caused by a mutation in the SOD1 gene leading to a progressive loss of motor neurons. As a result, people with SOD1-ALS experience increasing muscle weakness, loss of movement, difficulty breathing and swallowing and eventually succumb to the disease. Mutations in the SOD1 gene are responsible for approximately 2% of the estimated 168,000 people who have ALS globally (SOD1-ALS). More than 15% of people with ALS are thought to have a genetic form of the disease; however, they may not have a known family history of the disease.

Biogen is also evaluating tofersen for treatment of presymptomatic individuals who have a SOD1 genetic mutation.

The QALSODY regulatory submissions included results from a Phase 1 study in healthy volunteers, a Phase 1/2 study evaluating ascending dose levels, the Phase 3 VALOR study, and the Phase 3 OLE study, as well as 12-month integrated results from the Phase 3 VALOR study and the Phase 3 OLE study. The 12-month integrated data show that earlier initiation of QALSODY, compared to delayed initiation, slowed declines in clinical function, respiratory function, muscle strength and quality of life and build on the results previously observed in the initial readout. The 12-month data compare patients with early initiation of QALSODY (at the start of VALOR) to those who had a delayed initiation of QALSODY (six months later, in the OLE). Additionally, QALSODY demonstrated a favorable safety and tolerability profile in the VALOR study.

The FDA and EMA granted QALSODY Orphan Drug designation for the treatment of ALS.

TEGSEDI (TTR) – TEGSEDI (inotersen) injection is a transthyretin-directed antisense oligonucleotide medicine indicated for the treatment of ATTRv-PN in adults. TEGSEDI prevents the production of TTR protein, reducing the amount of amyloid buildup that damages organs and tissues. We currently sell TEGSEDI in Europe through our distribution agreement with Sobi. In Latin America, PTC is commercializing TEGSEDI in Brazil and is pursuing access in additional Latin American countries through its exclusive license agreement with us.

TEGSEDI approvals were based on efficacy and safety data from the Phase 3 NEURO-TTR study in patients with ATTRv-PN.

WAYLIVRA (apoC-III) – WAYLIVRA (volanesorsen) injection is an antisense oligonucleotide medicine indicated as an adjunct to diet in adult patients with genetically confirmed FCS and at high risk for acute, potentially fatal pancreatitis, in whom response to diet and triglyceride lowering therapy has been inadequate. WAYLIVRA reduces triglyceride levels by inhibiting the production of apoC-III, a protein that is a key regulator of triglyceride levels. WAYLIVRA received conditional marketing authorization in May 2019 from the European Commission, or EC. We sell WAYLIVRA in Europe through our distribution agreement with Sobi. In Latin America, WAYLIVRA is approved for two indications, FCS and FPL. PTC is commercializing WAYLIVRA in Brazil and is pursuing access in additional Latin American countries through its exclusive license agreement with us.

WAYLIVRA’s conditional marketing authorization in the EU for FCS and approval in Brazil for FCS were based on efficacy and safety data from the Phase 3 APPROACH study and supported by results from the Phase 3 COMPASS study. WAYLIVRA’s approval in Brazil for FPL was based on efficacy and safety data from the Phase 3 BROADEN study in patients with FPL.

Our Innovative Late-Stage Pipeline of Ionis-Owned Investigational Medicines

As a pioneer in RNA-targeted therapeutics, we continue to drive innovation with a leading pipeline in neurology, cardiology and select diseases of high unmet need. The table below lists Ionis-owned medicines currently in late-stage development, which Ionis plans to commercialize in the U.S. independently.

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Ionis is commercializing TRYNGOLZA (olezarsen) for the treatment of FCS in the U.S. Sobi is responsible for commercializing olezarsen in countries outside of the U.S., Canada and China and Theratechnologies is responsible for commercializing olezarsen in Canada

Olezarsen (apoC-III) – Olezarsen is an investigational RNA-targeted medicine that we are evaluating for people with sHTG. Olezarsen is designed to lower the body’s production of apoC-III, a protein produced in the liver that regulates triglyceride metabolism in the blood. sHTG is a disease categorized by triglyceride levels of 500 mg/dL and above. It develops due to primary (genetic) and secondary causes including diet and lifestyle, other medical conditions and certain medications. More than three million people are currently estimated to live with sHTG in the U.S. People living with sHTG are at risk of potentially life-threatening acute pancreatitis, or AP, (a painful inflammation of the pancreas) and atherosclerotic cardiovascular disease, or ASCVD. Reducing the risk of pancreatitis is a critically important reason to treat sHTG. Olezarsen is currently under review by the FDA. The agency has granted olezarsen priority review and set a PDUFA action date of June 30, 2026.

Our regulatory submission is based on the positive data from the broad development program for olezarsen that includes three Phase 3 studies supporting development for the treatment of sHTG: CORE, CORE2 and ESSENCE. The CORE and CORE2 studies met the primary endpoint across doses, with olezarsen demonstrating an up to 72% (p<0.001) placebo-adjusted mean reduction in fasting triglyceride levels at six months. The reductions were sustained through 12 months. Additionally at 12 months, 86% of olezarsen-treated patients achieved triglyceride levels less than 500 mg/dL, below the risk threshold for acute pancreatitis. Olezarsen also demonstrated a highly statistically significant 85% reduction in adjudicated acute pancreatitis events at 12 months (p<0.001). These results were based on a total of 22 events in 17 patients in the placebo group, compared to seven events in five patients in the olezarsen group. In an overall pooled analysis of the number of patients needed to treat, NNT, treating 20 patients with olezarsen is estimated to prevent one acute pancreatitis event over one year. In the highest risk group, patients with triglyceride levels greater than or equal to 880 mg/dL and a history of acute pancreatitis, treating four patients is estimated to prevent one event over one year. Olezarsen demonstrated favorable safety and tolerability at both dose levels in the studies.

The FDA granted Breakthrough Therapy designation to olezarsen as an adjunct to diet to reduce triglyceride (TG) levels in adults with severe hypertriglyceridemia.

As discussed above under “TRYNGOLZA” in the section titled, Our Marketed Medicines – Bringing Value to Patients Today, olezarsen is approved for the treatment of FCS.

Zilganersen (GFAP) – Zilganersen (formerly ION373) is an investigational RNA-targeted medicine we designed to inhibit the production of glial fibrillary acidic protein, or GFAP, that accumulates because of disease-causing variants in the GFAP gene. We are developing zilganersen as a potential treatment for people with genetically confirmed Alexander disease, or AxD. AxD is an ultra-rare, progressive and often fatal type of leukodystrophy, which are a group of genetic disorders that affect the brain’s white matter. AxD is estimated to occur in approximately one in one million to one in three million people worldwide and usually leads to death within 14 - 25 years after symptom onset. AxD can present throughout life as loss of independence and lack of ability to control muscles for swallowing, airway protection and purposeful movements. The impact of AxD can vary depending on factors like age of onset. Diagnosing AxD is based on a combination of clinical presentation, brain magnetic resonance imaging, or MRI, findings and genetic testing. There are no medicines approved for people with AxD, and current treatments focus on managing the symptoms of AxD. In January 2026, we submitted the zilganersen New Drug Application, or NDA, to the U.S. FDA. Additionally, we established an expanded access program, or EAP, for zilganersen in the U.S. for individuals aged two and older living with AxD, subject to certain inclusion and exclusion criteria.

Our regulatory submission of zilganersen is based on the positive data from the pivotal Phase 1-3 study we conducted in patients with AxD. Zilganersen 50 mg demonstrated statistically significant and clinically meaningful stabilization on the primary endpoint of gait speed as assessed by the 10-Meter Walk Test, or 10MWT, compared to control at week 61 (mean difference 33.3%, p=0.0412). Zilganersen also demonstrated consistent benefit in key secondary endpoints. In addition to achieving the primary endpoint, zilganersen demonstrated consistent favorable trends across key secondary endpoints, indicating evidence of slowed disease progression, stabilization or improvement. Key secondary endpoints include change from baseline in patients' self-identified Most Bothersome Symptom, or MBS, Score, Patient Global Impression of Severity, or PGIS, Score, Patient Global Impression of Change, or PGIC, Score and Clinician Global Impression of Change, or CGIC, Score. Zilganersen demonstrated favorable safety and tolerability in the study.

The FDA and EMA granted Orphan Drug designation to zilganersen. Additionally, the FDA granted Breakthrough Therapy, Fast Track and Rare Pediatric designations to zilganersen.

Obudanersen (UBE3A) – Obudanersen (formerly ION582) is an investigational RNA-targeted medicine we designed to inhibit the expression of the UBE3A antisense transcript, or UBE3A-ATS, and increase production of UBE3A protein, for the potential treatment of AS. AS is a rare, genetic neurological disease caused by the loss of function of the maternally inherited UBE3A gene. AS typically presents in infancy and is characterized by intellectual disability, balance issues, motor impairment, and debilitating seizures. Some patients are unable to walk or speak. Some symptoms can be managed with existing drugs; however, there are no approved disease modifying therapies.

We are conducting the ongoing placebo-controlled Phase 3 REVEAL study of obudanersen designed to assess the efficacy, safety and tolerability of obudanersen administered intrathecally in children and adults with AS who have a maternal UBE3A gene deletion or mutation. We are also conducting the ongoing open label Phase 1/2 study, HALOS, of obudanersen in patients with AS. In 2024, we presented positive results from the completed multiple ascending dose, or MAD, portion of the HALOS study in people with AS demonstrating consistent and encouraging clinical improvement on measures assessing all functional domains including communication, cognition and motor function. Obudanersen showed favorable safety and tolerability at all dose levels in the study. In 2025, we also presented positive 12- and 18-month long-term extension data from the HALOS study, which supports continued development.

The FDA and EMA granted Orphan Drug designations to obudanersen. Additionally, the FDA granted Breakthrough Therapy, Fast Track and Rare Pediatric designations to obudanersen.

Our Innovative Late-Stage Pipeline of Partnered Investigational Medicines

In addition to our Ionis-owned investigational medicines, we also have numerous potentially transformational partnered medicines in clinical development. The table below lists our partnered medicines in late-stage development. For further information on our collaboration agreements, refer to the section titled, Collaborative Arrangements.

Bepirovirsen (HBV) (GSK3228836) – Bepirovirsen is an investigational RNA-targeted medicine we designed to inhibit the production of viral proteins associated with hepatitis B virus, or HBV that can lead to CHB, potentially allowing a person’s immune system to regain control. Bepirovirsen inhibits the replication of viral DNA in the body, suppresses the level of hepatitis B surface antigen, or HBsAg, in the blood and stimulates the immune system to increase the chances of a durable and sustained response. CHB is a viral infection that can cause both acute and chronic liver disease. CHB occurs when the immune system is unable to clear the virus, resulting in long-lasting infection. It affects more than 250 million people and causes approximately 1.1 million deaths each year, largely due to complications such as cirrhosis and liver cancer. Many patients often require lifelong antiviral therapy for viral suppression; making functional cure a critical goal in disease management. Our partner, GSK, is responsible for ongoing development and commercialization of bepirovirsen worldwide.

In January 2026, we and GSK announced positive topline results from the B-Well 1 and B-Well 2 pivotal Phase 3 studies of bepirovirsen in patients with CHB. The B-Well studies met their primary endpoint of a statistically significant and clinically meaningful functional cure rate. Functional cure rates were significantly higher with bepirovirsen plus standard of care compared with standard of care alone. Results were statistically significant across all ranked endpoints, including in patients with baseline surface antigen (HBsAg) ≤1000 IU/ml where an even greater effect was demonstrated. The studies demonstrated an acceptable safety and tolerability profile consistent with what was reported in other studies.

The FDA, Center for Drug Evaluation, or CDE, of National Medical Products Administration, or NMPA, of China and Japanese Ministry of Health, Labour and Welfare, or MHLW, granted bepirovirsen Fast Track designation, Breakthrough Therapy designation and SENKU (formerly known as SAKIGAKE) designation, respectively, for the treatment of patients with CHB.

Eplontersen (TTR) – Eplontersen is an investigational RNA-targeted medicine designed to degrade mutant and wild-type TTR mRNA through binding to the TTR mRNA, which results in a reduction of serum TTR protein and TTR protein deposits in tissues. Eplontersen is currently being evaluated in patients with hereditary or wild-type transthyretin-mediated amyloid cardiomyopathy, or ATTR-CM. ATTR-CM is a progressive and fatal disease caused by the accumulation of misfolded TTR protein in the cardiac muscle. Patients experience ongoing debilitating heart damage resulting in progressive heart failure, which results in death within two to six years from disease onset. Worldwide, there are an estimated 300,000 – 500,000 patients with ATTR-CM. We and AstraZeneca are co-developing eplontersen globally and co-commercializing eplontersen in the U.S. AstraZeneca has exclusive rest-of-world commercialization rights.

We are conducting the ongoing placebo-controlled CARDIO-TTRansform Phase 3 cardiovascular outcome study of eplontersen in patients with ATTR-CM. We designed the study to evaluate the efficacy, safety and tolerability of eplontersen in patients with ATTR-CM.

As discussed above under “WAINUA” in the section titled, Our Marketed Medicines – Bringing Value to Patients Today, eplontersen is approved in numerous countries for the treatment of the ATTRv-PN.

The FDA granted Orphan Drug designation to WAINUA for the treatment of ATTR. The FDA also granted Fast Track designation to eplontersen for ATTR-CM.

Pelacarsen (Apo(a)) (TQJ230) – Pelacarsen is an investigational RNA-targeted medicine we designed to inhibit the production of apolipoprotein(a), or Apo(a), in the liver to offer a direct approach for reducing lipoprotein(a), or Lp(a). Elevated Lp(a) is recognized as an independent, genetic cause of CVD. Lp(a) levels are determined at birth and lifestyle modification, including diet and exercise, do not impact Lp(a) levels. Inhibiting the production of Apo(a) in the liver reduces the level of Lp(a) in blood, potentially slowing down or reversing CVD in people with hyperlipoproteinemia(a), a condition in which individuals have levels of Lp(a) greater than 50 mg/dL, the recognized threshold for risk of CVD. We believe antisense technology is well suited to address hyperlipoproteinemia(a) because it specifically targets the RNA that codes for all forms of the Apo(a) molecule. It is estimated that there are more than eight million people living with CVD and elevated levels of Lp(a). Our partner, Novartis, is responsible for ongoing development and commercialization of pelacarsen worldwide.

Novartis is conducting the placebo-controlled Phase 3 cardiovascular outcome study of pelacarsen, Lp(a)HORIZON, to assess the efficacy, safety and tolerability of pelacarsen in patients with elevated Lp(a) levels and established or at risk for CVD.

In November 2018, at the American Heart Association annual meeting, we reported results of the Phase 2 study of pelacarsen in patients with hyperlipoproteinemia(a). In the Phase 2 study, we observed statistically significant and dose dependent reductions from baseline in Lp(a) levels. Additionally, pelacarsen demonstrated a favorable safety and tolerability profile in the study.

The FDA and CDE of NMPA of China granted pelacarsen Fast Track designation and Breakthrough Therapy, respectively, for the treatment of patients with elevated Lp(a) and established CVD.

**Sefaxersen (IgAN) (**RO7434656) – Sefaxersen (formerly IONIS-FB-LRx) is an investigational RNA-targeted medicine we designed to reduce the production of complement factor B, or FB, and to lower activation of the alternative complement pathway. Genetic association studies have shown that overaction of the alternative complement pathway has been associated with the development of several complement-mediated diseases, including immunoglobulin A nephropathy, or IgAN. IgAN is one of the most common causes of inflammation that impairs the filtering ability of kidneys and is an important cause of chronic kidney disease and kidney failure. Also known as Berger’s disease, IgAN is characterized by deposits of IgA in the kidneys, resulting in inflammation and tissue damage. Our partner, Hoffmann-La Roche Inc. and F. Hoffmann-La Roche Ltd, collectively Roche, is responsible for ongoing development and commercialization of sefaxersen worldwide.

In April 2023, Roche initiated a placebo-controlled Phase 3 study of sefaxersen, called IMAGINATION, in patients with IgAN designed to assess the efficacy, safety and tolerability of sefaxersen.

We reported positive results from a Phase 2 open-label study of sefaxersen in patients with IgAN, demonstrating robust and sustained reductions in complement FB and other key measures of the alternative complement pathway. Sefaxersen treatment also resulted in sustained reductions in proteinuria with patients maintaining kidney function, as measured by estimated glomerular filtration rate, or eGFR, during six months of treatment. Sefaxersen demonstrated a favorable safety and tolerability profile in the study.

Tofersen (SOD1) – As discussed above under “QALSODY” in the section titled, Our Marketed Medicines – Bringing Value to Patients Today, tofersen is being evaluated for treatment of presymptomatic individuals who have a SOD1 genetic mutation

Ulefnersen (FUS) – Ulefnersen is an investigational RNA-targeted medicine we designed to reduce the production of the fused in sarcoma, or FUS, protein to treat people with Amyotrophic lateral sclerosis, or ALS, caused by mutations in the FUS gene. Because antisense-mediated reduction of mutant FUS protein in a FUS-ALS mouse model demonstrated the ability to prevent motor neuron loss, it is hypothesized that reduction of FUS protein will reverse or prevent disease progression in FUS-ALS patients. FUS-ALS is a rare, fatal, neurodegenerative disorder characterized by muscle weakness, loss of movement, and difficulty breathing and swallowing, resulting in a severely declining quality of life and eventually death. Current treatment options are extremely limited, with no medicines that significantly slow disease progression. Our partner, Otsuka, is responsible for global regulatory and commercialization activities, and costs for ulefnersen.

In April 2021, we initiated the Phase 3 FUSION study of ulefnersen in patients with FUS-ALS designed to assess the efficacy, safety and tolerability of ulefnersen.

The FDA and EMA granted Orphan Drug designation to ulefnersen. The FDA also granted Fast Track designation to ulefnersen.

Our Innovative Mid-Stage Pipeline of Investigational Medicines

We also have a rich mid-stage pipeline with numerous potentially transformational investigational medicines, including both Ionis-owned and partnered therapies. The table below lists our medicines in mid-stage development. For further information on our collaboration agreements, refer to the section titled, Collaborative Arrangements.

Our Technology

We have a rich history of discovering and developing life-changing medicines that target RNA – a molecule that carries out the genetic instructions encoded in people's DNA. Today, we are focused on harnessing advanced technology to create medicines that target and interact with both RNA and DNA to treat a variety of conditions, including prevalent cardiometabolic diseases, neurological conditions and rare diseases with few or no effective treatment options. Our recent technology advancements have enabled us to advance programs with the potential for extended dosing and delivery to new tissues, such as muscle. We have also added capabilities to utilize small interfering RNA, or siRNA, and potentially gene editing in addition to our novel antisense technology, which gives us the potential to deliver medicines to a greater number of people living with serious diseases.

Overview of Ionis’ Technology

The advanced technology behind our medicines leverages oligonucleotides – small sequences of modified RNA – to precisely target and interact with RNA and DNA. We achieve this precision by tapping into the same biology used to store and process information in the genetic code – our genes. Our technology enables us to change the function or expression of a gene in a highly specific and directed manner, which, in turn, can help address the root cause of a disease.

For example, a gene called TTR contains instructions to make TTR protein, which can accumulate in tissues and cause disease. We have designed eplontersen, an RNA medicine that seeks out, binds to and destroys TTR RNA, which significantly reduces the levels of the disease-causing TTR protein. Our technology can also increase or change the expression of a gene. For example, in SMA we have mitigated the deficiency in a critical protein called SMN with a medicine that changes the “instructions” in RNA. This modulation enabled the production of the SMN protein, thereby counteracting the root, genetic cause of the disease.

Emerging Technology Advancements

Our recent technology advancements have enabled us to create even more potent medicines amenable to new potential targets and tissue types. We have also diversified the approaches we can use in designing our medicines to reach more patients with severe diseases. Today our medicines and those entering our pipeline utilize our key technology advances, including MsPA backbone chemistry, Bicycle technology and Vect-Horus technology. And we now have the potential to use gene editing, which modifies DNA.

Mesyl phosphoramidate Backbone Chemistry

We designed our MsPA backbone chemistry to improve both therapeutic index and durability. It does this by increasing metabolic stability relative to the other backbone chemistries we utilize. We have also shown it can improve potency in certain circumstances and reduce non-specific interactions with proteins that can cause undesirable effects, such as proinflammatory effects. We currently have multiple new programs using our MsPA backbone in preclinical development.

Bicycle Collaboration

In 2021, we entered into a collaboration with Bicycle Therapeutics that we expect can expand our LICA platform to target both skeletal and cardiac muscle, and potentially deliver medicines across the blood brain barrier. Bicycles are small, bicyclic peptides that have high affinity and selectivity for protein targets. Our collaboration with Bicycle allows us to utilize Bicycles that bind transferrin receptor 1 to facilitate the tissue specific delivery of oligonucleotide drugs (both antisense and siRNAs). Our first program utilizing Bicycle technology, ION826 (AZD4063), is being advanced by AstraZeneca and is currently in Phase 1 development.

Vect-Horus License Agreement

In 2023, we exclusively licensed Vect-Horus’ platform technology for systemic delivery of RNA-targeted therapeutics to potentially cross the blood-brain barrier and address targets in the central nervous system for a specified number of targets. This technology is derived from antibodies made by certain camelid species, which are smaller than normal human antibodies. We advanced our first program that utilizes this technology into preclinical development in 2025.

Gene Editing and Metagenomi Collaboration

In 2022, we entered into a collaboration with Metagenomi that leverages our extensive expertise in RNA-targeted therapeutics and Metagenomi’s next-generation gene editing systems to pursue a mix of validated and novel genetic targets with the goal of discovering and developing new drugs. These targets have the potential to expand therapeutic options for patients.

Gene editing utilizes specific RNA-guided nucleases known as Cas enzymes to precisely and permanently modify a DNA sequence. Because of this, gene editing holds the promise of treatments that could provide long-term, potentially permanent, therapeutic benefits.

Gene editing is highly complementary and synergistic with RNA-targeted therapeutics. Both platforms rely on the same nucleic acid hybridization principals to precisely target nucleases to either RNA, in the case of RNase H and siRNA drugs, or to DNA in the case of Clustered Regularly Interspaced Short Palindromic Repeats, or CRISPR-Cas systems. This enables us to leverage our expertise in nucleic acids and modified nucleic acid chemistry with the goal to enhance gene editing’s ability to treat diseases for which there are limited treatment options.

Collaborative Arrangements

We have established alliances with a number of leading global pharmaceutical companies. Our partners include the following companies, among others: AstraZeneca, Biogen, GSK, Novartis, Ono, Otsuka and Roche. Through our partnerships, we have earned both commercial revenue in the form of royalties and sales milestones and a broad and sustaining base of R&D revenue in the form of license fees, upfront payments and milestone payments. Below, we include the significant terms of our collaboration agreements. For additional details, including other financial information, refer to Part IV, Item 15, Note 4, Collaborative Arrangements and Licensing Agreements, in the Notes to the Consolidated Financial Statements.

AstraZeneca

WAINUA (Eplontersen) Collaboration

In 2021, we entered into a joint development and commercialization agreement with AstraZeneca to develop and commercialize eplontersen for the treatment of ATTR. The FDA approved eplontersen with the brand name, WAINUA, for ATTRv-PN, while the EC approved WAINUA for ATTRv-PN in the EU as WAINZUA. WAINUA is also approved in other markets, including the UK, Canada and China, with additional regulatory reviews underway. Under the agreement, we are jointly developing WAINUA with AstraZeneca worldwide for ATTRv-PN and ATTR cardiomyopathy, or ATTR-CM. We are jointly commercializing WAINUA with AstraZeneca in the U.S. We granted AstraZeneca exclusive rights to commercialize WAINUA outside the U.S.

The collaboration includes territory-specific development, commercial and medical affairs cost-sharing provisions. From inception through December 31, 2025, AstraZeneca was responsible for 55 percent of the costs associated with the ongoing global Phase 3 development program. After December 31, 2025, AstraZeneca is responsible for 75 percent and 87.5 percent of development costs in the U.S. and the rest of the world, respectively. AstraZeneca is responsible for the vast majority of the commercial and medical affairs costs in the U.S. and all costs associated with bringing WAINUA to market outside the U.S.

Over the term of the collaboration, we are eligible to receive an upfront payment, development and approval milestone payments and sales milestone payments. In addition, we are eligible to receive up to mid-20 percent royalties for sales in the U.S. and tiered royalties up to the high teens for sales outside the U.S.

We recognize royalties that we earn from WAINUA sales within commercial revenue in our consolidated statements of operations.

From inception through December 31, 2025, we have generated more than $615 million in payments under this collaboration, including regulatory milestone payments and revenue we earned from cost sharing provisions and royalties.

Cardiovascular, Renal and Metabolic Collaboration

We also have a collaboration with AstraZeneca focused on discovering and developing treatments for cardiovascular, renal and metabolic diseases, which we formed in 2015. Under our collaboration, AstraZeneca has licensed multiple medicines from us. AstraZeneca is responsible for global development, regulatory and commercialization activities and costs for each of the medicines it has licensed from us.

Over the term of the collaboration, we are eligible to receive an upfront payment, license fees, development milestone payments, regulatory milestone payments and sales milestone payments. In addition, we are eligible to receive tiered royalties up to 10 percent on net sales from any product that AstraZeneca successfully commercializes under this collaboration agreement. From inception through December 31, 2025, we have generated more than $420 million in payments under this collaboration.

Biogen

Marketed Medicines

SPINRAZA

In 2012, we entered into a collaboration agreement with Biogen to develop and commercialize SPINRAZA. We are receiving tiered royalties ranging from 11 percent to 15 percent on sales of SPINRAZA. Under our agreement, Biogen is responsible for global development, regulatory and commercialization activities and costs for SPINRAZA. From inception through December 31, 2025, we recognized more than $2.5 billion in total revenue under this collaboration, including more than $2.0 billion in revenue from SPINRAZA royalties and more than $425 million in R&D revenue.

We have exclusively in-licensed patents related to SPINRAZA from Cold Spring Harbor Laboratory and the University of Massachusetts. We pay Cold Spring Harbor Laboratory and the University of Massachusetts a low single digit royalty on net sales of SPINRAZA.

QALSODY

In 2018, Biogen exercised its option to license QALSODY from us. We are receiving tiered royalties ranging from 11 percent to 15 percent on net sales of QALSODY. Under our agreement, Biogen is responsible for global development, regulatory and commercialization activities and costs for QALSODY. Biogen is also evaluating QALSODY as a potential treatment for presymptomatic SOD1-ALS patients in the ongoing ATLAS study. From inception through December 31, 2025, we recognized more than $120 million in total revenue under this collaboration, including approximately $14 million in revenue from QALSODY royalties and $108 million in R&D revenue.

New antisense medicines for the treatment of SMA

In 2017, we entered into a collaboration agreement with Biogen to identify new antisense medicines for the treatment of SMA. In 2021, Biogen exercised its option to license salanersen (formerly ION306). Biogen is solely responsible for the costs and expenses related to the development, manufacturing and potential future commercialization of salanersen. We will receive development and regulatory milestone payments from Biogen if salanersen advances towards marketing approval.

Over the term of this collaboration, we are eligible to receive development, regulatory and sales milestone payments. In addition, we are eligible to receive tiered royalties from the mid-teens to mid-20 percent range on net sales from any product that Biogen successfully commercializes under this collaboration. From inception through December 31, 2025, we have generated $85 million in payments under this collaboration.

Neurology Collaborations

We have multiple collaborations with Biogen focused on using antisense technology to advance the treatment of neurological disorders, including our 2018 and 2012 neurology collaborations. Under these collaborations, Biogen gained exclusive rights to the use of our antisense technology to develop therapies for certain neurological diseases and the option to license certain medicines resulting from these collaborations. If Biogen exercises its option to license a medicine, it will assume global development, regulatory and commercialization responsibilities and costs for that medicine.

For each medicine under these collaborations, we are eligible to receive a license fee, development milestone payments and regulatory milestone payments. In addition, we are eligible to receive tiered royalties up to the 20 percent range on net sales from any products that Biogen successfully commercializes under these collaborations. We are currently advancing multiple programs under this collaboration. From inception through December 31, 2025, we have generated more than $1.3 billion in payments under these collaborations.

GSK

In 2010, we entered into a collaboration with GSK using our antisense drug discovery platform to discover and develop new medicines against targets for serious and rare diseases, including infectious diseases. Under our collaboration, GSK is developing bepirovirsen for the treatment of chronic HBV infection. In 2019, following positive Phase 2 results, GSK licensed our HBV program. GSK is responsible for all global development, regulatory and commercialization activities and costs for the HBV program.

Over the term of the collaboration, we are eligible to receive an upfront payment, a license fee, development milestone payments, regulatory milestone payments and sales milestone payments if GSK successfully develops and commercializes bepirovirsen. In addition, we are eligible to receive tiered royalties ranging from 10 to 12 percent on net sales of bepirovirsen. From inception through December 31, 2025, we have generated more than $105 million in payments under the HBV program collaboration.

Novartis

Pelacarsen Collaboration

In 2017, we initiated a collaboration with Novartis to develop and commercialize pelacarsen for patients with elevated Lp(a) and cardiovascular disease, or CVD. Novartis is responsible for conducting and funding development and regulatory activities for pelacarsen, including a global Phase 3 cardiovascular outcomes study that Novartis initiated in 2019.

Over the term of the collaboration, we are eligible to receive an upfront payment, a license fee, a development milestone payment, regulatory milestone payments and sales milestone payments. We are also eligible to receive tiered royalties in the mid-teens to low 20 percent range on net sales of pelacarsen. From inception through December 31, 2025, we have generated more than $275 million in payments under this collaboration.

New Medicine for the Treatment of Lp(a)-Driven Cardiovascular Disease

In 2023, we entered into a collaboration and license agreement with Novartis for the discovery, development and commercialization of a novel medicine for patients with Lp(a)-driven CVD. In 2025, Novartis terminated this collaboration and license agreement. Prior to this, Novartis was solely responsible for the development, manufacturing and potential commercialization of the next generation Lp(a) medicine. From inception through December 31, 2025, we have generated more than $65 million in payments under this collaboration.

Ono

In March 2025, we entered into an agreement with Ono Pharmaceutical Co., Ltd., or Ono, to develop and commercialize sapablursen, an investigational RNA-targeted medicine for the potential treatment of polycythemia vera, a rare and potentially life-threatening hematologic disease. We are responsible for completing the Phase 2 IMPRSSION study of sapablursen, including the ongoing extension period. Ono is solely responsible for subsequent development, regulatory filings and commercialization of sapablursen.

Over the term of the collaboration, we are eligible to receive an upfront payment, development milestone payments, regulatory milestone payments and sales milestone payments. We are also eligible to receive royalties in the mid-teen percentage range on net sales. From inception through December 31, 2025, we have generated more than $285 million in payments under this collaboration.

Roche

Sefaxersen for Complement-Mediated Diseases

In 2018, we entered into an agreement with Roche to develop sefaxersen for the treatment of complement-mediated diseases, including IgAN, and geographic atrophy, or GA. In April 2023, Roche initiated a Phase 3 study of sefaxersen in patients with IgAN.

After positive data from a Phase 2 clinical study in patients with IgAN, Roche licensed sefaxersen in 2022. As a result, Roche is responsible for global development, regulatory and commercialization activities, and costs for sefaxersen.

In July 2024, Roche discontinued development of sefaxersen for the treatment of GA, the advanced stage of dry age-related macular degeneration, following the completion of the Phase 2 study, which showed a favorable safety profile and target engagement, but insufficient efficacy to advance into Phase 3 development.

Over the term of the collaboration, we are eligible to receive a license fee, development milestone payments, regulatory milestone payments and sales milestone payments. We are also eligible to receive tiered royalties from the high teens to 20 percent on net sales. From inception through December 31, 2025, we have generated approximately $140 million in payments under this collaboration.

Huntington’s Disease

In 2013, we entered into an agreement with Roche to develop treatments for Huntington’s disease, or HD, based on our antisense technology. Under the agreement, we discovered and developed tominersen, an investigational antisense medicine targeting HTT protein. We developed tominersen through completion of our Phase 1/2 clinical study in people with early-stage HD. In 2017, upon completion of the Phase 1/2 study, Roche exercised its option to license tominersen. As a result, Roche is responsible for all global development, regulatory and commercialization activities and costs for tominersen.

Over the term of the collaboration, we are eligible to receive a license fee, development milestone payments, regulatory milestone payments and sales milestone payments as tominersen advances. In addition, we are eligible to receive milestone payments for each additional medicine successfully developed. We are also eligible to receive tiered royalties up to the mid-teens on net sales of any product resulting from this collaboration. From inception through December 31, 2025, we have generated more than $150 million in payments under this collaboration.

RNA-Targeting Medicines for Alzheimer's Disease and Huntington's Disease

In September 2023, we entered into an agreement with Roche to develop two undisclosed early-stage programs for RNA-targeting investigational medicines for the treatment of Alzheimer’s disease, or AD, and HD. Under the agreement, we are responsible for advancing the two programs through preclinical studies and Roche is responsible for clinical development, manufacturing and commercialization of the medicines if they receive regulatory approval.

In January 2026, Roche initiated a Phase 1 trial for an investigational medicine for the treatment of AD.

Over the term of the collaboration, we are eligible to receive an upfront payment, development milestone payments and sales milestone payments. In addition, we are eligible to receive tiered royalties up to the mid-teens on net sales. From inception through December 31, 2025, we have generated more than $65 million in payments under this collaboration.

Commercialization Partnerships

Otsuka

In December 2023, we entered into an agreement with Otsuka Pharmaceutical Co., Ltd., or Otsuka, to commercialize DAWNZERA in Europe. In the second quarter of 2024, we expanded the agreement to include commercialization rights for DAWNZERA in the Asia-Pacific region. We are responsible for the ongoing development of DAWNZERA.

In November 2024, we entered into an agreement with Otsuka to commercialize ulefnersen worldwide. We are responsible for the ongoing development of ulefnersen.

Over the term of the collaborations, we are eligible to receive upfront payments, regulatory milestone payments and sales milestone payments. In addition, we are eligible to receive tiered royalties up to 30 percent on net sales. From inception through December 31, 2025, we have generated more than $125 million in payments under these collaborations.

PTC Therapeutics

In August 2018, we entered into an exclusive license agreement with PTC Therapeutics to commercialize TEGSEDI and WAYLIVRA in Latin America and certain Caribbean countries. Under the license agreement, we are eligible to receive royalties from PTC in the mid-20 percent range on net sales for each medicine. In December 2021 and September 2023, we started receiving royalties from PTC for TEGSEDI and WAYLIVRA sales, respectively. From inception through December 31, 2025, we have generated more than $70 million in payments under this collaboration.

Swedish Orphan Biovitrum AB (Sobi)

We began commercializing TEGSEDI and WAYLIVRA in Europe in January 2021 and TEGSEDI in North America in April 2021 through distribution agreements with Sobi. Under our agreements, we are responsible for supplying finished goods inventory to Sobi and Sobi is responsible for selling each medicine to the end customer. In exchange, we earn a distribution fee on net sales from Sobi for each medicine. In October 2023, our agreement for TEGSEDI in North America was terminated and we discontinued TEGSEDI in North America in 2024. In March 2025, we entered into an agreement with Sobi to commercialize TRYNGOLZA in countries outside of the U.S., Canada and China. From inception through December 31, 2025, we have generated more than $145 million in payments under this collaboration.

Theratechnologies

In December 2024, we entered into an agreement with Theratechnologies, Inc. to commercialize DAWNZERA and olezarsen in Canada. We are responsible for the ongoing development of DAWNZERA and olezarsen.

Technology Enhancement Collaborations

Bicycle Therapeutics

In 2020, we entered into a collaboration agreement with Bicycle Therapeutics and obtained an option to license its peptide technology that we expect can expand our LICA platform to target both skeletal and cardiac muscle, and potentially deliver medicines across the blood brain barrier. In 2021, we exercised our option to license Bicycle's technology. Our payment to Bicycle for licensing its technology included an equity investment in Bicycle. In addition, we will pay Bicycle milestone payments and royalties that are contingent on the achievement of certain development, regulatory and sales events.

Metagenomi

In 2022, we entered into a collaboration and license agreement with Metagenomi to research, develop and commercialize investigational medicines for up to four initial genetic targets, and, upon the achievement of certain development milestones, four additional genetic targets using gene editing technologies. As a result, we paid Metagenomi to license its technologies and will pay Metagenomi certain fees for the selection of genetic targets. In addition, we will pay Metagenomi milestone payments and royalties that are contingent on the achievement of certain development, regulatory and sales events. We will also reimburse Metagenomi for certain of its costs in conducting its research and drug discovery activities under the collaboration.

Vect-Horus

In December 2023, we entered into a license agreement with Vect-Horus to provide us with a worldwide, exclusive license for a specified number of targets using Vect-Horus' technology for systemic delivery of RNA-targeted therapeutics that may cross the blood-brain barrier and address targets in the central nervous system. We will pay Vect-Horus milestone payments and royalties that are contingent on the achievement of certain development, regulatory and sales events.

Other Agreements

Alnylam Pharmaceuticals, Inc.

Under the terms of our agreement with Alnylam, each party licensed to the other party its early patent estate relating to oligonucleotide chemistry for specified uses (generally, single-stranded ASOs for us and siRNA for Alnylam). Additionally, in 2015, we and Alnylam entered into an alliance in which we exclusively cross-licensed rights to four therapeutic programs. Alnylam granted us an exclusive, royalty-bearing license to its chemistry, RNA targeting mechanism and target-specific intellectual property for oligonucleotides against four targets, including FXI and Apo(a) and two other targets. In exchange, we granted Alnylam an exclusive, royalty-bearing license to our chemistry, RNA targeting mechanism and target-specific intellectual property for oligonucleotides against four other targets.

Manufacturing

We manufacture most of the active pharmaceutical ingredients, or APIs, we use for our research and development, or R&D, activities ourselves. We have also manufactured API and commercial supply for our approved medicines. We have dedicated significant resources to develop ways to improve manufacturing efficiency and capacity. Since we can use variants of the same nucleotide building blocks and the same type of equipment to produce our oligonucleotide medicines, we found that the same techniques we used to efficiently manufacture one oligonucleotide medicine could help improve the manufacturing processes for our other medicines. By developing several proprietary chemical processes to scale up our manufacturing capabilities, we have greatly reduced the cost of producing oligonucleotide medicines. For example, we have significantly reduced the cost of raw materials through improved yields and process efficiencies, while at the same time increasing our capacity to make our medicines. Through both our internal research and development programs and collaborations with outside vendors, we may achieve even greater efficiency and further cost reductions.

Our manufacturing facility is located in a 26,800 square foot building in Carlsbad, California. We purchased this building in 2017. In addition, we have a 25,800 square foot building that houses support functions for our manufacturing activities. We lease this facility under a lease that has a term ending in October 2031. Our manufacturing facility is subject to periodic inspections by the FDA and foreign equivalents to ensure that it is operating in compliance with current Good Manufacturing Practices, or cGMP, requirements.

As part of our collaborations, we may agree to manufacture clinical trial material and/or commercial drug supply for our partners. For example, in the past we have manufactured clinical trial material for AstraZeneca, Biogen, GSK, Roche, and Novartis and commercial drug supply for Biogen.

We believe we have sufficient manufacturing capacity at our own facility or at contract manufacturing organizations, or CMOs, to meet our current internal research, development and potential commercial needs, as well as our obligations under existing agreements with our partners for research, development and commercial material. We and/or our CMOs manufacture process performance qualification batches and pre-approval inspection batches of our Phase 3 medicines that may be used for regulatory submissions and, pending regulatory approval, commercial sale. We believe our current network of CMOs are capable of providing sufficient quantities to meet anticipated commercial demands. Additionally, we continue to evaluate relationships with additional suppliers to increase overall capacity and diversify our supply chain. We plan to leverage our relationships with CMOs to maintain long-term supply at competitive prices in the future. While we believe that there are alternate sources of supply that can satisfy our commercial requirements, it is possible that identifying and establishing relationships with such sources, if necessary, could result in significant delay or material additional costs. We also could experience a disruption in supply from our current CMOs.

CMOs are subject to the FDA’s cGMP requirements and other rules and regulations prescribed by foreign regulatory authorities. We depend on our CMOs for continued compliance with cGMP requirements and applicable foreign standards.

Specifically, we have the following in place for our commercial medicines and our late-stage medicines.

TRYNGOLZA/Olezarsen

For TRYNGOLZA’s commercial drug supply, we are using CMOs to produce API and finished goods for ourselves and Sobi. For the ongoing olezarsen clinical studies, we and/or our CMOs have supplied the API and the finished drug product. We intend to leverage our relationships with CMOs to meet and maintain long-term commercial supply at competitive prices in the future. We plan to accomplish this through a combination of maintaining adequate levels of safety stock and increasing the batch sizes to support approved indications.

DAWNZERA

For DAWNZERA’s commercial drug supply, we are using CMOs to produce API and finished goods for ourselves and Otsuka. We intend to leverage our relationships with CMOs to meet and maintain long-term commercial supply at competitive prices in the future. We plan to accomplish this through maintaining adequate levels of safety stock.

WAINUA/Eplontersen

AstraZeneca is responsible for WAINUA's commercial drug supply. Our CMOs supplied the API and the finished drug product for WAINUA’s Phase 3 program. Pursuant to our collaboration with AstraZeneca, we will supply WAINUA using CMOs for the ongoing clinical trials.

SPINRAZA

Biogen is responsible for SPINRAZA drug supply.

QALSODY

Biogen is responsible for QALSODY drug supply.

TEGSEDI and WAYLIVRA

For TEGSEDI’s commercial drug supply, we are using CMOs to produce API and finished goods for Sobi and PTC. For WAYLIVRA’s commercial drug supply, we are using API that we have manufactured and CMOs to produce the finished goods.

Zilganersen

We and our CMOs have supplied the API and the finished drug product for zilganersen clinical supply. We intend to use the same supply chain for future commercial drug supply.

Ulefnersen

We and our CMOs have supplied the API and the finished drug product for ulefnersen that we believe will be sufficient through the completion of the Phase 3 programs. Our partner, Otsuka, will be responsible for future commercial drug supply.

Obudanersen

We supplied API and drug product for the obudanersen Phase 1 and Phase 2 programs and intend to continue to supply drug for the ongoing Phase 3 program and any further clinical programs.

Pelacarsen

We supplied API and finished drug product for pelacarsen’s Phase 3 program. Pursuant to our collaboration with Novartis, Novartis is responsible for any further pelacarsen drug supply.

Bepirovirsen

We supplied API for bepirovirsen’s Phase 1 and Phase 2 programs. Pursuant to our collaboration with GSK, GSK is responsible for any further bepirovirsen drug supply.

Sefaxersen (IONIS-FB-LRx)

We supplied API for the sefaxersen Phase 1 and Phase 2 IgAN programs. Pursuant to our collaboration with Roche, Roche is responsible for any further drug supply for sefaxersen.

Commercial Operations

We have established sales and marketing capabilities to support our commercial launches of TRYNGOLZA, DAWNZERA and WAINUA in the U.S. We began with our co-commercialization partnership with AstraZeneca for WAINUA in which we combine our experience in RNA-targeted therapeutics and deep knowledge of the TTR amyloidosis market with AstraZeneca's global scale in drug development and commercialization to enable market penetration for the benefit of patients.

We entered a new chapter as a fully integrated commercial-stage biotechnology company with our first independent commercial launch of TRYNGOLZA in December 2024. We have continued refining our portfolio strategy and recruiting experienced professionals with relevant backgrounds in sales, marketing, patient education, market access, portfolio planning and market insight, new product commercial strategy and commercial operations in the pharmaceutical industry. We are focused on developing a unique and innovative approach to bring our medicines to patients living with serious diseases. We have built core capabilities and a commercial platform with the ability to scale as needed to meet our current and future commercialization needs. In addition, we established our TRYNGOLZA, DAWNZERA and olezarsen (sHTG) field sales team and plan to build additional field teams as we approach each of our launches.

Medical Affairs

We have built medical affairs capabilities to disseminate information about our medicines and increase disease awareness through various channels of communication with key stakeholders. Our medical affairs function is responsible for funding and coordinating investigator-sponsored trials, communicating scientific and clinical information to healthcare providers, medical professionals and patients, and managing publications.

Intellectual Proprietary Rights

We rely on patents, trademarks, trade secrets, and proprietary know-how to develop and maintain a competitive position in RNA-targeted therapeutics generally and to protect our investment in specific products. To this end, we focus our resources on intellectual property, or IP, that drives value for our company.

Product-Specific IP

Each of our medicines is protected worldwide by product-specific patents claiming oligonucleotides having the nucleobase sequences and chemical modifications of our medicines; and methods of achieving cellular or clinical endpoints using such oligonucleotides. We pursue such patents in significant markets and/or countries for each medicine in development. We also seek to maximize patent term. In some cases, the patent term can be extended to recapture a portion of the term lost during regulatory review. Expiration dates listed below do not reflect any such extensions.

Commercial products are also protected by trademarks filed throughout the world.

Marketed Products

TRYNGOLZA/Olezarsen and ApoC-III

We believe TRYNGOLZA (olezarsen) is protected from generic competition in the U.S. and Europe until at least 2034. Patent applications to protect TRYNGOLZA in other jurisdictions have been granted or are being pursued. The table below lists some key issued patents protecting TRYNGOLZA in the U.S. and Europe.

20

Trademark

The name “TRYNGOLZA” is protected by trademarks throughout the world.

DAWNZERA and PKK

We believe DAWNZERA is protected from generic competition in the U.S. and Europe until at least 2035. Patent applications to protect DAWNZERA in other jurisdictions have been granted or are being pursued. The table below lists some key issued patents protecting DAWNZERA in the U.S. and Europe.

Trademark

The name "DAWNZERA" is protected by trademarks throughout the world.

WAINUA/WAINZUA/Eplontersen and Transthyretin

Patents

We believe WAINUA/WAINZUA (eplontersen) is protected from generic competition in the U.S. and Europe until at least 2034. Patent applications to protect WAINUA/WAINZUA in other jurisdictions are being pursued. The table below lists some key issued patents protecting WAINUA/WAINZUA in the U.S. and Europe:

Trademarks

The names “WAINUA” and “WAINZUA” are protected by trademarks owned by our commercial partner Astra Zeneca.

SPINRAZA and Survival Motor Neuron 2

Patents

We believe SPINRAZA (nusinersen) is protected from generic competition in the U.S. until at least 2035 and in Europe until at least 2030 by a suite of patents. These issued patents include: (i) patents licensed from the University of Massachusetts drawn to antisense compounds having the sequence of SPINRAZA, independent of chemical modification, and uses of such compounds for treating SMA, (ii) joint patents with Cold Spring Harbor Laboratory claiming fully modified 2’-MOE compounds targeting SMN2, including the precise composition of matter of SPINRAZA and methods of using such compositions; and (iii) dosing and therapeutic methods of using such compounds and compositions. With Biogen’s license of SPINRAZA, we assigned our interest in these patents to Biogen. The table below lists some key issued patents protecting SPINRAZA in the U.S. and Europe:

Trademarks

The name “SPINRAZA” is protected throughout the world by trademarks owned by our commercial partner Biogen.

QALSODY and SOD-1

Patents

We believe QALSODY is protected from generic competition in the U.S. and Europe until at least 2035. Patent applications to protect QALSODY in other jurisdictions have been granted or are being pursued. With Biogen’s license of QALSODY, we assigned our interest in these patents to Biogen. The table below lists some key issued patents protecting QALSODY in the U.S. and Europe:

Trademarks

The name “QALSODY” is protected throughout the world by trademarks owned by our commercial partner Biogen.

TEGSEDI and Transthyretin

Patents

We believe TEGSEDI (inotersen) is protected from generic competition in the U.S. and Europe until at least 2031. The table below lists some key issued patents protecting TEGSEDI in the U.S. and Europe:

Trademarks

The name “TEGSEDI” is protected by trademark throughout the world.

WAYLIVRA and ApoC-III

Patents

We believe WAYLIVRA (volanesorsen) is protected from generic competition in Europe until at least 2034. We have obtained patent claims in the U.S. and Europe drawn to the use of antisense compounds complementary to a broad active region of human ApoC-III, including the site targeted by WAYLIVRA. We have also obtained issued patents claiming the specific sequence and chemical composition of WAYLIVRA in the U.S. and Europe. The table below lists some key issued patents protecting WAYLIVRA in the U.S. and Europe:

Trademark

The name “WAYLIVRA” is protected by trademark in Europe.

Late-Stage Ionis-Owned Programs

Zilganersen and GFAP

We believe zilganersen is protected from generic competition in the U.S. and Europe until at least 2041. The table below lists key issued patents protecting zilganersen in the U.S. and Europe:

Obudanersen and UBE3A

We believe obudanersen is protected from generic competition in the U.S. and Europe until at least 2040. Patent applications to protect obudanersen in other jurisdictions have been granted or are being pursued. The table below lists key issued patents protecting obudanersen in the U.S. and Europe:

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Late-Stage Partnered Programs

Bepirovirsen and Hepatitis B Virus

We believe bepirovirsen is protected from generic competition in the U.S. and Europe until at least 2032. Patent applications to protect bepirovirsen in other jurisdictions have been granted for are being pursued. With GSK’s license of bepirovirsen, we assigned our interest in these patents to GSK. The table below lists some key issued patents protecting bepirovirsen in the U.S. and Europe:

Pelacarsen and Apo(a)

We believe pelacarsen is protected from generic competition in the U.S. and Europe until at least 2034. Patent applications to protect pelacarsen in other jurisdictions have been granted or are being pursued. The table below lists some key issued patents protecting pelacarsen in the U.S. and Europe:

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Sefaxersen and Factor B

We believe sefaxersen is protected from generic competition in the U.S. and Europe until at least 2035. Patent applications to protect sefaxersen in other jurisdictions are being pursued. The table below lists some key issued patents protecting sefaxersen in the U.S. and Europe:

Ulefnersen and FUS

We believe ulefnersen will be protected from generic competition in the U.S. and Europe until at least 2040. The table below lists a key pending patent application designed to protect ulefnersen in the U.S. and a key issued patent protecting ulefnersen in Europe:

Platform IP

In addition to the IP that provides exclusivity for specific products, we also pursue IP that provides exclusivity for our core technology more generally. Our core technology patents include claims to chemically modified oligonucleotides as well as designs utilizing these chemical modifications. Because these core claims are independent of specific therapeutic target, nucleic acid sequence, or clinical indication, they may reach several products.

Chemically Modified Nucleosides and Oligonucleotides

The most broadly applicable of our patents are those that claim modified nucleosides and oligonucleotides comprising the modified nucleosides that we incorporate into our medicines to increase their therapeutic efficacy. The following are some of our patents in this category in the U.S. and Europe:

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LIgand-Conjugated Antisense (LICA) Technology

We also have patent claims to chemistries created to enhance targeting of antisense medicines to specific tissues and cells to improve a drug’s properties. We designed our GalNAc LIgand-Conjugated Antisense, or LICA, medicines to provide an increase in potency for targets in the liver. We have successfully obtained issued patent claims covering our LICA technology conjugated to any modified oligonucleotide, including gapmers, double-stranded siRNA compounds, and fully modified oligonucleotides. The following patents are some examples of our issued patents in this category:

Manufacturing

We also own patents claiming methods of manufacturing and purifying oligonucleotides and related compounds. These patents claim methods for improving oligonucleotide drug manufacturing, including processes for large-scale oligonucleotide synthesis and purification.

Government Regulation

Regulation by government authorities in the U.S. and other countries is a significant component in the development, manufacture and commercialization of pharmaceutical products and services. In addition to regulations enforced by the FDA and relevant foreign regulatory authorities, we are also subject to regulation under the Occupational Safety and Health Act, the Environmental Protection Act, the Toxic Substances Control Act, the Resource Conservation and Recovery Act and other present and potential future federal, state and local regulations.

Extensive regulation by the U.S. and foreign governmental authorities governs the development, manufacture and sale of our medicines. In particular, our medicines are subject to a number of approval requirements by the FDA in the U.S. under the Federal Food, Drug and Cosmetic Act, or FDCA, and other laws and by comparable agencies in those foreign countries in which we conduct business. The FDCA and other various federal, state and foreign statutes govern or influence the research, testing, manufacture, safety, labeling, storage, recordkeeping, approval, promotion, marketing, distribution, post-approval monitoring and reporting, sampling, quality, and import and export of our medicines. State, local, and other authorities also regulate pharmaceutical manufacturing facilities and procedures.

Our manufacturing facility and our CMOs are subject to periodic inspection by the FDA and other foreign equivalents to ensure that they are operating in compliance with cGMP requirements. In addition, marketing authorization for each new medicine may require a rigorous manufacturing pre-approval inspection by regulatory authorities. Post approval, there are strict regulations regarding changes to the manufacturing process, and, depending on the significance of the change, changes may require prior FDA approval. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting and documentation requirements upon us and any third-party manufacturers that we may decide to use.

The FDA must approve any new medicine or new indication before a manufacturer can market it in the U.S. To obtain approval, we and our partners must complete clinical studies and prepare and submit an NDA or supplemental NDA to the FDA. When the FDA approves a medicine, it will issue an approval letter authorizing commercial marketing of the medicine and may require a risk evaluation and mitigation strategy, or REMS, to help ensure the benefits of the medicine outweigh the potential risks. The requirements for REMS can materially affect the potential market and profitability of our medicines. In foreign jurisdictions, the drug approval process is similarly demanding.

Pricing and Reimbursement

For any approved medicine, domestic and foreign sales of the medicine depend, in part, on the availability and amount of coverage and adequate reimbursement by third-party payers, including governments and private health plans. The process for determining whether a payer will provide coverage for a product may be separate from the process for setting the reimbursement rate that the payer will pay for the product, or procedures that utilize such product. Private health plans may seek to manage cost and use of our medicines by implementing coverage and reimbursement limitations. For example, third-party payers may limit coverage to specific products on an approved list, or formulary, which might not include all FDA-approved products for a particular indication. Moreover, a payer's decision to provide coverage for a medicine does not imply that an adequate reimbursement rate will be approved. Additionally, coverage and reimbursement for drugs can differ significantly from payer to payer. One third-party payer's decision to cover a particular medicine does not ensure that other payers will also provide coverage for the medicine or will provide coverage at an adequate reimbursement rate.

Third-party payers are increasingly challenging the price and examining the medical necessity and cost-effectiveness of medicines and services, in addition to their safety and efficacy. To obtain coverage and reimbursement for any medicine that might be approved for sale, we may need to conduct expensive pharmacoeconomic studies to demonstrate the medical necessity and cost-effectiveness of our medicine. These studies will be in addition to the studies required to obtain regulatory approvals. If third-party payers do not consider a medicine to be cost-effective compared to other available therapies, they may not cover the medicine after approval as a benefit under their plans or, if they do, the level of payment may not be sufficient to sell such medicine at a profit.

In certain jurisdictions, governments may also regulate or influence coverage, reimbursement and/or pricing of our medicines to control cost or affect use. In the European community, governments influence the price of drugs through their pricing and reimbursement rules and control of national health care systems that fund a large part of the cost of those medicines to consumers. Some jurisdictions operate positive and negative list systems under which medicines may only be marketed once a reimbursement price has been agreed to by the government. To obtain reimbursement or pricing approval, some of these countries may require the completion of clinical studies that compare the cost effectiveness of a particular drug candidate to currently available therapies. Other member states allow companies to fix their own prices for medicines but monitor and control company profits.

The marketability of any medicine for which we receive regulatory approval for commercial sale may suffer if the government or third-party payers fail to provide adequate coverage and reimbursement. In addition, the focus on cost containment measures in the U.S. and other countries has increased and we expect will continue to increase the pressure on pharmaceutical pricing. Coverage policies and third-party reimbursement rates may change at any time. Even if we attain favorable coverage and reimbursement status for one or more medicines for which we receive regulatory approval, less favorable coverage policies and reimbursement rates may be implemented in the future.

Healthcare Reform

Both the federal and state governments in the U.S. and foreign governments continue to propose and pass new legislation and regulations designed to contain or reduce the cost of healthcare.

In the U.S., recent health reform measures have resulted in reductions in Medicare and other healthcare funding, and there have been several recent U.S. Congressional inquiries, legislation and executive orders designed to, among other things, reduce drug prices, increase competition (including by enhancing support for generic and biosimilar drugs), lower out-of-pocket drug costs for patients, curtail spread pricing practices by pharmacy benefit managers, and foster scientific innovation to promote better health care and improved health. For example, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, or collectively the Affordable Care Act, substantially changed the way healthcare is financed by both governmental and private insurers and continues to significantly impact the U.S. pharmaceutical industry. Since its enactment, there have been amendments and judicial, Congressional and executive branch challenges to certain aspects of the Affordable Care Act, as well as efforts to repeal or replace certain aspects of the Affordable Care Act. We expect that additional U.S. federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that the U.S. federal government will pay for healthcare products and services, which could result in reduced demand or revenue for our commercial medicines and our medicines in development.

There has also been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in efforts to bring more transparency to drug pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for medicines. For example, in August 2022, the Inflation Reduction Act of 2022, or the IRA, was signed into law, which includes key actions aimed at reducing the costs of prescription drugs and allows the U.S. Department of Health and Human Services, or HHS, to negotiate the price of certain single-source drugs covered under Medicare and establish a price cap on such drugs, known as the Maximum Fair Price. There are important exemptions to the Maximum Fair Price, including for medications that are orphan drug designated and approved for only one rare disease, and drugs with low Medicare spend as defined by the Centers for Medicare & Medicaid Services, or CMS. The IRA, among other things, (1) directed HHS to negotiate, through a negotiation program, the price of certain single-source drugs and biologics that have been on the market for at least seven years covered under Medicare, or the Medicare Drug Price Negotiation Program, and (2) imposed rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation. Each year, up to 20 products will be selected by HHS for the Medicare Drug Price Negotiation Program. Products subject to the Medicare Drug Price Negotiation Program are expected to experience a significant reduction in reimbursement from the Medicare program on a per unit basis.

The current U.S. Presidential administration is pursuing policies to reduce regulations and expenditures across government agencies, including at HHS, the FDA, CMS, and other related agencies, with a particular focus on most favored nation pricing equal to or lower than those paid in other developed nations. These actions, presently directed by executive orders or memoranda from the Office of Management and Budget, may propose additional policy changes that create uncertainty for our business. For example, in furtherance of the administration’s drug pricing initiatives, in December 2025, CMS issued proposed rules that, if finalized, would implement new mandatory and voluntary payment models to implement a most favored nation rebate model. These models are referred to as the GLOBE Model, GUARD Model and GENEROUS Model. At this time, it remains unclear whether the proposed models will be finalized and, if so, whether any changes will be made prior to their implementation.

Any reduction in reimbursement from Medicare and other government programs may result in a similar reduction in payments from private payers. Our future product sales may be subject to additional discounts from list price in the form of rebates and discounts provided to 340B covered entities. Changes to the 340B program or to Medicare or Medicaid programs at the federal or state level, including outcomes of ongoing litigation in our industry, may impact our product prices and rebate liability.

Other Healthcare Laws

In addition, the distribution of prescription pharmaceutical products is subject to the Drug Supply Chain Security Act, or DSCA, which regulates the distribution and tracing of prescription drugs and prescription drug samples at the federal level and sets minimum standards for the regulation of drug distributors by the states. The DSCA imposes requirements to ensure accountability in distribution and to identify and remove counterfeit and other illegitimate products from the market.

Numerous regulatory authorities in addition to the FDA, including, in the U.S., CMS, other divisions of the HHS, the U.S. Department of Justice, and similar foreign, state and local government authorities, regulate sales, promotion and other activities following drug approval. As described above, the FDA regulates all advertising and promotion activities for drugs under its jurisdiction both prior to and after approval. Only those claims relating to safety and efficacy that the FDA has approved may be used in labeling. Physicians may prescribe legally available drugs for uses that are not described in the drug’s labeling and that differ from those tested and that the FDA approved. The FDA does not regulate the behavior of physicians in their choice of treatments, but FDA regulations do impose stringent restrictions on manufacturers’ pre-approval communications and communications regarding off-label uses. If we do not comply with applicable FDA requirements, we may face adverse publicity, enforcement action by the FDA, including corrective advertising, consent decrees and the full range of civil and criminal penalties available to the FDA. Promotion of off-label uses of drugs can also implicate the false claims laws described below.

In the U.S., sales, marketing and scientific/educational programs must also comply with various federal and state laws pertaining to healthcare “fraud and abuse,” including anti-kickback laws and false claims laws. Anti-kickback laws make it illegal for a prescription drug manufacturer to solicit, offer, receive, or pay any remuneration in exchange for, or to induce, the referral of business, including the purchase or prescription of a particular drug. Moreover, healthcare reform legislation has strengthened certain of these laws. For example, the Affordable Care Act, among other things, amends the intent requirement of the federal anti-kickback and criminal healthcare fraud statutes to clarify that a person or entity does not need to have actual knowledge of this statute or specific intent to violate it. In addition, the Affordable Care Act clarifies that the government may assert that a claim that includes items or services resulting from a violation of the federal anti-kickback statute constitutes a false or fraudulent claim for purposes of the federal false claims statutes. False claims laws prohibit anyone from knowingly and willingly presenting, or causing to be presented for payment, to third-party payers (including Medicare and Medicaid) claims for reimbursed drugs or services that are false or fraudulent, claims for items or services not provided as claimed, or claims for medically unnecessary items or services. Our activities relating to the sale and marketing of our drugs may be subject to scrutiny under these laws. Violations of fraud and abuse laws may be punishable by criminal, civil and administrative sanctions, including fines and civil monetary penalties, the possibility of exclusion from federal healthcare programs (including Medicare and Medicaid) and corporate integrity agreements, which impose, among other things, rigorous operational and monitoring requirements on companies. Similar sanctions and penalties also can be imposed upon executive officers and employees, including criminal sanctions against executive officers under the so-called “responsible corporate officer” doctrine, even in situations where the executive officer did not intend to violate the law and was unaware of any wrongdoing.

Other healthcare laws that may affect our ability to operate include, for example, the following:

• The federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, which imposes requirements relating to the privacy, security and transmission of individually identifiable health information on certain health care providers, health care clearinghouses, and health plans, known as covered entities, and their covered subcontractors, known as business associates;
• HIPAA also created additional federal criminal statutes that prohibit, among other actions, knowingly and willfully executing, or attempting to execute, a scheme to defraud any healthcare benefit program, including private third-party payers and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false, fictitious or fraudulent statement in connection with the delivery of or payment for healthcare benefits, items or services;
• Foreign and state laws governing the privacy and security of health information, such as the General Data Protection Regulation, or GDPR, in the EU and UK; and the California Consumer Privacy Act, or CCPA, in California, some of which are more stringent than HIPAA and many of which differ from each other in significant ways and may not have the same effect;
• The Physician Payments Sunshine Act, which requires certain manufacturers of medicines, devices, biologics, and medical supplies to report annually to CMS information related to payments and other transfers of value to physicians (defined to include doctors, dentists, optometrists, podiatrists, and chiropractors), other healthcare providers (such as physician assistants and nurse practitioners), and teaching hospitals, and ownership and investment interests held by physicians and their immediate family members; and
• Foreign laws requiring reporting on transfers of value to physicians, which may differ from those in the U.S.

Given the significant penalties and fines that can be imposed on companies and individuals if convicted, allegations of such violations often result in settlements even if the company or individual being investigated admits no wrongdoing. Settlements often include significant civil sanctions, including fines and civil monetary penalties, corporate integrity agreements, and could include criminal penalties. If the government alleged, or subsequently settled or convicted us or our executive officers of violating these laws, our business could be harmed. In addition, private individuals can bring similar actions. Our activities could be subject to challenge for the reasons discussed above and due to the broad scope of these laws and the increasing attention being given to them by law enforcement authorities. As described above, other healthcare laws that may affect our operations include HIPAA, analogous state laws governing the privacy and security of health information, some of which are more stringent than HIPAA and many of which differ from each other in significant ways and may not have the same effect, and the Physician Payments Sunshine Act. Further, there are an increasing number of state laws that require manufacturers to make reports to states on pricing and marketing information. Many of these laws contain ambiguities as to what is required to comply with the laws. Given the lack of clarity in laws and their implementation, our reporting actions could be subject to the penalty provisions of the pertinent state authorities.

Similar rigid (and in some areas, heightened) restrictions are imposed on the promotion and marketing of drugs in the E.U. and other countries. Even in those countries where we may not be directly responsible for the promotion and marketing of our medicines, if our potential international distribution partners engage in inappropriate activity, it can have adverse implications for us.

As discussed above, both the federal and state governments in the U.S. and foreign governments continue to propose and pass new legislation and regulations designed to contain or reduce the cost of healthcare, which may impact these laws. Further, such laws may be subject to future amendments, updated guidance or varying interpretations.

The Foreign Corrupt Practices Act

The U.S. Foreign Corrupt Practices Act, or FCPA, prohibits certain individuals and entities, including us, from promising, paying, offering to pay, or authorizing the payment of anything of value to any foreign government official, directly or indirectly, to obtain or retain business or an improper advantage. The FCPA also requires publicly traded companies to maintain accurate books and records and establish and maintain a system of internal accounting controls. If we violate the FCPA, it could result in large civil and criminal penalties as well as have an adverse effect on our reputation, operations, and financial condition. We could also face collateral consequences such as debarment and the loss of export privileges. In addition, in many other countries, the healthcare providers who conduct clinical trials or prescribe pharmaceuticals are employed by their government, and the purchasers of pharmaceuticals are government entities; therefore, any dealings with these prescribers and purchasers may be subject to regulation under the FCPA. There is no certainty that all employees and third-party business partners (including our contract research organizations, contract manufacturing organizations, distributors, wholesalers, agents, contractors and other partners) will comply with the FCPA or local anti-bribery laws. Importantly, we do not control the actions of contract manufacturers and other third-party agents, although we may be liable for their actions.

Competition

Our Business in General

Some of our medicines may compete with existing therapies for market share and some of our medicines in development may compete for patients in clinical trials. In addition, there are a number of companies pursuing the development of genetic medicines and the development of pharmaceuticals utilizing these technologies. These companies include biopharmaceutical companies and large pharmaceutical companies acting either independently or together. Our medicines are differentiated from traditional small molecule medicines by their chemistry, how they move in the body, how they act in the body, delivery technology, and formulations.

Our commercial medicines and our medicines in development address numerous markets. The diseases our medicines target for which we have or may receive marketing authorization will determine our competition. For some of our medicines, an important factor may be the timing of market introduction of competitive products. Accordingly, the relative speed with which we can develop medicines, complete the clinical trials and marketing authorization processes and supply commercial quantities of the medicines to the market are important competitive factors. We expect to compete with products approved for sale based on a variety of factors, including, among other things, product efficacy, safety, mechanism of action, dosing administration, marketing and sales strategy and tactics, availability, price, and reimbursement.

Below we have included what we believe to be medicines that compete or may compete directly with our marketed medicines and late-stage medicines. We included competitors and potential competitors that are past Phase 1 development.

Marketed Medicines

TRYNGOLZA/Olezarsen and WAYLIVRA

We believe that the following medicines could compete with TRYNGOLZA/olezarsen and WAYLIVRA in FCS and sHTG:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

DAWNZERA

We believe that the following medicines could compete with DAWNZERA as a prophylactic treatment for patients with HAE:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

WAINUA/Eplontersen and TEGSEDI

We consider the following medicines as competitors and potential future competitors to WAINUA/eplontersen and TEGSEDI for ATTRv-PN and/or ATTR-CM:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

SPINRAZA

We consider the following medicines as competitors to SPINRAZA for the indication of SMA:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

QALSODY

We believe that the following medicine could compete with QALSODY in SOD1-ALS:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

Late-Stage Ionis-Owned Programs

Zilganersen

We are not aware of any medicines in clinical development for AxD other than zilganersen.

Obudanersen

We believe that the following medicines could compete with obudanersen in Angelman syndrome:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

Late-Stage Partnered Programs

Bepirovirsen

We believe that the following medicines could compete with bepirovirsen in HBV:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

Pelacarsen

We believe that the following medicines could compete with pelacarsen in CVD in patients with elevated Lp(a):

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

Sefaxersen

We believe that the following medicines could compete with sefaxersen in IgAN:

(1) Taken from public documents including respective company press releases, company presentations, and scientific presentations.

Ulefnersen

We are not aware of any medicines in clinical development for FUS-ALS other than ulefnersen.

Corporate Responsibility Initiatives

We believe operating responsibly and sustainably creates long-term value for our company and our stakeholders. We recognize the importance of Corporate Responsibility, or CR, and Environmental, Social and Governance, or ESG, initiatives as it relates to our business strategy and risk assessment. We continue to evolve our CR program and established three strategic CR pillars and associated goals to guide our approach and provide a framework for reporting on our performance.

We began reporting on CR metrics in 2021 and have continued to expand disclosure since then. In 2025, we reported progress on our CR goals aligned to the three strategic CR pillars that we believe are most important to our business:

Ionis Corporate Responsibility Strategic Pillars

Our CR initiatives are driven by our Chief Executive Officer and executive-level CR Steering Committee, or CR Committee. The CR Committee consists of senior leaders in key functions across the company, including legal, finance, investor relations, human resources, research and development, manufacturing, commercial, compliance and corporate affairs.

The CR Committee is part of our governance framework, which defines responsibilities and ensures we have the right systems and controls to oversee ethical and sustainable operations across our business. Our Board of Directors, specifically the Nominating, Governance and Review Committee, has oversight of our overall CR strategy and material CR risks and opportunities as outlined in the Committee’s charter. The Board receives updates related to corporate governance and corporate responsibility from the CR Committee at least once annually. We look to our stakeholders and third-party frameworks such as the Sustainability Accounting Standards Board Health Care – Biotechnology and Pharmaceuticals Standard and the Task Force on Climate-Related Financial Disclosures to inform our approach and our disclosures.

We continue to share progress on our CR goals and more details on our initiatives in our 2025 CR Report, which we expect to publish in April 2026 and will be available on our website. Nothing in the report or on our website shall be deemed incorporated by reference into this Annual Report on Form 10-K.

Employees and Human Capital

As of February 19, 2026, we employed 1,402 people, the vast majority of whom reside in the U.S. A significant number of our management and professional employees have had prior experience with pharmaceutical, biotechnology or medical product companies. Our average employee turnover rate in 2025 was 7 percent, while the turnover for life sciences and medical device companies over this period was 20 percent according to a survey published by Radford – an Aon Hewitt Company. Given the uniqueness and complexity of our technology, it is critical to retain the knowledge and experience of outstanding long service employees. The experience and seniority of our employees is as critical to our future success as it has been to the success we have enjoyed to date.

Collective bargaining agreements do not cover any of our employees, and management considers relations with our employees to be good. We believe that the future will be defined by outstanding people and we are committed to recruiting, developing, motivating, and rewarding them.

We encourage you to visit our website for more detailed information regarding our Human Capital programs and initiatives. Nothing on our website shall be deemed incorporated by reference into this Annual Report on Form 10-K.

Benefits

We reward our employees individually on the basis of their responsibilities and accomplishments. We offer competitive compensation and benefits to our employees. In addition to salary and bonus programs, we also offer:

• Comprehensive medical, dental and vision insurance;
• 401(k) matching;
• Stock options, RSUs and an Employee Stock Purchase Plan, or ESPP;
• Vacation, holiday, sick time and paid time off for volunteering;
• Wellness programs;
• Flexible spending accounts for health and dependent day care needs;
• Family care benefits;
• Life, AD&D insurance and long-term disability insurance coverage options; and
• Employee Assistance Program, or EAP.

We recognize achievements with salary increases, equity awards, promotions, and bonus opportunities.

Pay Equity

We are committed to paying our employees fairly, regardless of their gender, ethnicity, race, age or other personal characteristics. To ensure we are achieving our commitment, we benchmark and evaluate pay based on market data and consider factors such as an employee’s role and experience, an employee’s performance and internal equity. We also regularly review our compensation practices, in terms of our overall workforce and individual employees, to ensure our pay is fair and equitable.

Our 2025 pay equity analysis confirmed that compensation for employees performing the same or similar work shows no statistically significant differences based on gender, ethnicity, race or age.

A Culture of Inclusion

At Ionis, prejudicial barriers to human potential and productivity are foreign to our values. We recognize that for the full potential of our workforce to be realized, we must cultivate an inclusive culture where all employees feel empowered to contribute fully in an environment that values different perspectives, leading to better ​​​​​​​ideas and increased innovation. We have several employee-led resource groups dedicated to supporting engagement and empowerment and a diverse management team and board of directors. From our Executive Leadership Team to our newest hire, we strive for an environment where our employees feel a strong sense of belonging in our organization.

Training and Development

We designed our training and development programs to help employees gain important Ionis knowledge and develop the skills to be successful at Ionis. All of our trainings from new hire through senior leader, are focused on the Ionis culture and core principles and learning what we mean when we say: “Working the Ionis Way.”

We empower our employees to build rewarding careers at Ionis, driven by a culture of having a bias to act that encourages personal and professional employee growth. Ionis offers robust training opportunities with course offerings and events available to every employee regardless of level or function. In addition, employees also have access to Ionis’ learning and development library that houses important information on career growth and planning. By supporting our employees, we know that each professional development milestone enables our continued success.

Investing in our securities involves a high degree of risk. You should carefully consider the following information about the risks described below, together with the other information contained in this report and in our other public filings in evaluating our business. If any of the following risks actually occur, our business could be materially harmed, and our financial condition and results of operations could be materially and adversely affected. As a result, the trading price of our securities could decline, and you might lose all or part of your investment.

Risks Related to the Commercialization of our Medicines

We have limited experience as a company in commercializing medicines and we will have to continue to invest significant resources to develop our capabilities. If we are unable to effectively establish or maintain an effective commercialization infrastructure, or enter into agreements with third parties to commercialize our medicines, we may not be able to successfully commercialize our medicines.

We have historically relied on third parties to commercialize our marketed medicines and have limited experience as a company in commercializing medicines. We currently have two independently launched medicines, TRYNGOLZA and DAWNZERA, and we expect to independently launch additional medicines in the near future. Any failure to effectively commercialize our medicines, including our failure to allocate resources to our commercial launches efficiently or timely, could adversely impact the revenue we generate from our medicines. If the commercialization of our independently launched medicines and future sales of such are less successful than anticipated by us or our investors or securities analysts, our stock price could decline and our business may be harmed.

We will have to continue to invest significant financial and management resources to build and maintain the infrastructure required to successfully commercialize our medicines. We will need to establish and maintain effective sales teams for each of our independently launched medicines and there are significant risks involved in managing a sales organization, including our ability to hire, retain and incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, and effectively manage a geographically dispersed sales and marketing team. We must also continue to scale-up existing internal support functions to aid our commercialization efforts, which will need to work effectively in coordination with new commercial functional areas. Any failure to establish or maintain an effective commercialization infrastructure, including our sales, marketing, market access, distribution, and related capabilities, scale-up our existing support functions, or effectively integrate new functional areas, could adversely affect our ability to successfully commercialize our medicines.

If we choose to rely on third parties to assist us in commercializing our medicines, we may not be able to enter into collaborations or hire consultants or external service providers on acceptable financial terms, or at all. In addition, if we continue to engage third parties to assist us in the commercialization of our medicines, our product revenues and profitability may be lower than if we commercialized such medicines ourselves.

The proximity of our current and planned independent launches could increase the likelihood that the risks set forth above will occur.

If the market does not accept our medicines, including our commercial medicines and our medicines in development, we are not likely to generate substantial revenues or become consistently profitable.

Even if our medicines are authorized for marketing, our success will depend upon the medical community, patients and third-party payers accepting our medicines as medically useful, cost-effective, safe and convenient. Even when the FDA or foreign regulatory authorities authorize our or our partners’ medicines for commercialization, doctors may not prescribe our medicines to treat patients. Furthermore, we and our partners may not successfully commercialize additional medicines.

Additionally, in many of the markets where we or our partners may sell our medicines in the future, if we or our partners cannot agree with the government or other third-party payers regarding the price we can charge for our medicines, we may not be able to sell our medicines in that market. Similarly, cost control initiatives by governments or third-party payers could decrease the price received for our medicines or increase patient coinsurance to a level that makes our medicines, including our commercial medicines and our medicines in development, economically unviable. If the pricing of any of our medicines decreases for any reason, it will reduce our revenue for such medicine. For example, Biogen has in the past disclosed that SPINRAZA revenue decreased in part due to lower pricing in the U.S. and certain rest-of-world markets.

The degree of market acceptance for our medicines, including our commercial medicines and our medicines in development, depends upon several factors, including the:

• receipt and scope of marketing authorizations;
• establishment and demonstration in the medical and patient community of the efficacy and safety of our medicines, public perception regarding our medicines and their potential advantages over competing products;
• cost and effectiveness of our medicines compared to other available therapies;
• patient convenience of the dosing regimen for our medicines; and
• reimbursement policies of government and third-party payers.

Based on the profile of our medicines, physicians, patients, patient advocates, payers or the medical community in general may not accept or use any of the medicines that we or our partners may develop. For example, the product label for WAYLIVRA in the EU requires regular blood monitoring, which has negatively affected our ability to attract and retain patients for this medicine.

If government or other third-party payers fail to provide adequate coverage and payment rates for our medicines, including our commercial medicines and our medicines in development, or if healthcare reform measures increase our costs, decrease our sales, or negatively impact reimbursement for our products, our revenue will be limited.

In both domestic and foreign markets, sales of our current and future products will depend in part upon the availability of coverage and reimbursement from third-party payers. The majority of patients in the U.S. who would fit within our target patient populations for our medicines have their healthcare supported by a combination of Medicare coverage, other government health programs such as Medicaid, managed care providers, private health insurers and other organizations. Coverage decisions may depend upon clinical and economic standards that disfavor new medicines when more established or lower cost therapeutic alternatives are already available or subsequently become available. Assuming coverage is approved, the resulting reimbursement payment rates might not be enough to make our medicines affordable. Even if favorable coverage status and adequate reimbursement rates are attained, less favorable coverage policies and reimbursement rates may be implemented in the future. Accordingly, our commercial medicines and our medicines in development will face competition from other therapies and medicines for limited financial resources. Furthermore, we or our partners may need to conduct post-marketing studies to demonstrate the cost-effectiveness of any future products to satisfy third-party payers. These studies might require us to commit a significant amount of management time and financial and other resources. In addition, third-party payers may never consider our future products as cost-effective and adequate third-party coverage and reimbursement might not be available to enable us to maintain price levels sufficient to realize an appropriate return on investment in product development.

Third-party payers, whether foreign or domestic, or governmental or commercial, are developing increasingly sophisticated methods of controlling healthcare costs. In addition, in the U.S., no uniform policy of coverage and reimbursement for medicines exists among third-party payers. Therefore, coverage and reimbursement for medicines can differ significantly from payer to payer.

Further, we believe that future coverage, reimbursement and pricing will likely be subject to increased restrictions both in the U.S. and in international markets. In the U.S., recent health reform measures have resulted in reductions in Medicare and other healthcare funding, and there have been several recent U.S. Congressional inquiries, legislation and executive orders designed to, among other things, reduce drug prices, increase competition (including by enhancing support for generic and biosimilar drugs), lower out-of-pocket drug costs for patients, curtail spread pricing practices by pharmacy benefit managers, and foster scientific innovation to promote better health care and improved health. For example, the Affordable Care Act substantially changed the way healthcare is financed by both governmental and private insurers and continues to significantly impact the U.S. pharmaceutical industry. Since its enactment, there have been amendments and judicial, Congressional and executive branch challenges to certain aspects of the Affordable Care Act, as well as efforts to repeal or replace certain aspects of the Affordable Care Act. We expect that additional U.S. federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that the U.S. federal government will pay for healthcare products and services, which could result in reduced demand or revenue for our commercial medicines and our medicines in development.

In addition, the Inflation Reduction Act of 2022, or the IRA, includes key actions aimed at reducing the costs of prescription drugs and allows HHS to negotiate the price of certain single-source drugs covered under Medicare and establish a price cap on such drugs. The IRA, among other things, (1) directed HHS to negotiate the price of certain single-source drugs and biologics that have been on the market for at least seven years covered under Medicare, or the Medicare Drug Price Negotiation Program, and (2) imposed rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation. Each year, up to 20 products will be selected by HHS for the Medicare Drug Price Negotiation Program. Products subject to the Medicare Drug Price Negotiation Program are expected to experience a significant reduction in reimbursement from the Medicare program on a per unit basis.

The current U.S. Presidential administration is pursuing policies to reduce regulations and expenditures across government agencies, including at HHS, the FDA, CMS, and other related agencies, with a particular focus on most favored nation pricing equal to or lower than those paid in other developed nations. These actions, presently directed by executive orders or memoranda from the Office of Management and Budget, may propose additional policy changes that create uncertainty for our business. For example, in furtherance of the administration’s drug pricing initiatives, in December 2025, CMS issued proposed rules that, if finalized, would implement new mandatory and voluntary payment models to implement a most favored nation rebate model. These models are referred to as the GLOBE Model, GUARD Model and GENEROUS Model. At this time, it remains unclear whether the proposed models will be finalized and, if so, whether any changes will be made prior to their implementation. These and other recent actions and policies may significantly reduce U.S. drug prices, potentially impacting manufacturers’ global pricing strategies and profitability, while increasing their operational costs and compliance risks.

Any reduction in reimbursement from Medicare and other government programs may result in a similar reduction in payments from private payers. Our future product sales may be subject to additional discounts from list price in the form of rebates and discounts provided to covered entities under the Public Health Service Act 340B drug pricing program. Changes to the 340B program or to Medicare or Medicaid programs at the federal or state level, including outcomes of ongoing litigation in our industry, may impact our product prices and rebate liability.

At the state level, legislatures have increasingly passed legislation and implemented regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. Third-party coverage and reimbursement for medicines may not be available or adequate in either the U.S. or international markets, which would negatively affect the potential commercial success of our products, our revenue and our profits.

If we or our partners fail to compete effectively, our medicines, including our commercial medicines and our medicines in development, will not generate significant revenues.

The biotechnology and pharmaceutical industries are highly competitive and subject to significant and rapid technological change. Our competitors engage in drug discovery throughout the world, are numerous, and include, among others, major pharmaceutical companies and specialized biopharmaceutical firms. In addition, other companies are engaged in developing RNA-targeted technology. Our competitors may, among other things, relative to our medicines or medicines in development:

• develop safer or more effective products;
• develop less costly products;
• receive more favorable reimbursement coverage;
• implement more effective approaches to sale and marketing;
• develop products that are more convenient to use than our medicines;
• have access to increased manufacturing capacity;
• obtain regulatory approval for products more quickly; or
• establish superior intellectual property positions.

These competitive advantages could make our medicines, including our commercial medicines and our medicines in development, obsolete or non-competitive.

Many of our competitors have substantially greater financial, technical and human resources than we do. In addition, many of these competitors have significantly greater experience than we do in conducting preclinical testing and human clinical studies of new pharmaceutical products, in obtaining FDA and other regulatory authorizations of such products and in commercializing such products.

There are several pharmaceutical and biotechnology companies engaged in the development or commercialization in certain geographic markets of products against targets that are also targets of products in our development pipeline or of medicines we are commercializing. For example:

• TRYNGOLZA faces competition in FCS from a commercial competitor and, if approved for sHTG, could face competition from commercial competitors in the future;
• DAWNZERA faces competition from several commercial competitors, including an oral product, and could face competition from additional commercial competitors in the future;
• WAINUA faces competition in ATTRv-PN from numerous competitors, including an oral product, and, if approved for ATTR-CM, would face competition from several commercial competitors, including an oral product, and could face competition from additional commercial competitors in the future;
• SPINRAZA faces competition from both a gene therapy product and an oral product for the treatment of SMA. Biogen has in the past disclosed that SPINRAZA revenue decreased due to a reduction in demand as a result of increased competition and that future sales of SPINRAZA may be adversely affected by competing products;
• QALSODY could face competition from a commercial competitor in the future; and
• Obudanersen, if approved, could face competition from commercial competitors in the future, including oral products.

For details regarding medicines that compete or may compete directly with our marketed medicines and late-stage medicines, refer to the section titled, Competition, in Part I, Item 1, Business.

Certain of our partners are pursuing other technologies or developing other medicines either on their own or in collaboration with others, including our competitors, to treat some of the same diseases that our own programs target. Competition may negatively impact a partner’s focus on and commitment to our medicines and, as a result, could delay or otherwise negatively affect the commercialization of our partnered medicines. Additionally, companies that are developing medicines that target the same patient populations as our medicines in development may compete with us to enroll participants in the clinical trials for such medicines, which could make it more difficult for us to complete enrollment for these clinical trials.

Our medicines could be subject to regulatory limitations following approval.

Following approval of a medicine, we and our partners must comply with comprehensive government regulations regarding the manufacture, marketing and distribution of medicines. The FDA and foreign regulatory bodies have the authority to impose significant restrictions on an approved medicine through the product label. We or our partners may not obtain the labeling claims necessary or desirable to successfully commercialize our medicines, including our commercial medicines and our medicines in development.

Promotional communications regarding prescription medicines must be consistent with the information in the product’s approved labeling. Additionally, prescription medicines may be promoted only for the approved indication(s) in accordance with the approved label. The FDA and other regulatory authorities actively enforce the laws and regulations prohibiting the promotion of off-label uses, and a company that is found to have improperly promoted off-label uses may be subject to significant liability.

In addition, when approved, the FDA or a foreign regulatory authority may condition approval on the performance of post-approval clinical studies or patient monitoring, which could be time consuming and expensive. For example, in connection with the conditional marketing approval for WAYLIVRA in the EU, we are required to conduct a post-authorization safety study to evaluate the safety of WAYLIVRA on thrombocytopenia and bleeding in FCS patients taking WAYLIVRA. If the results of such post-marketing studies are not satisfactory, the FDA, EC or other foreign regulatory authorities may withdraw the marketing authorization or may condition continued marketing on commitments from us or our partners that may be expensive and time consuming to fulfill.

If we or others identify side effects after any of our medicines are on the market, or if manufacturing problems occur subsequent to regulatory approval, or if we, our CMOs or our partners fail to comply with regulatory requirements, we or our partners may, among other things, lose regulatory approval and be forced to withdraw products from the market, need to conduct additional clinical studies, incur restrictions on the marketing, distribution or manufacturing of the product, and/or change the labeling of our medicines.

We depend on our collaborations with Biogen for the development and commercialization of SPINRAZA and QALSODY.

We have entered into separate collaborative arrangements with Biogen to develop and commercialize SPINRAZA and QALSODY. We entered into these collaborations primarily to:

• fund our development activities for SPINRAZA and QALSODY;
• seek and obtain regulatory approvals for SPINRAZA and QALSODY; and
• successfully commercialize SPINRAZA and QALSODY.

We are relying on Biogen to obtain additional regulatory approvals for SPINRAZA and QALSODY, generate additional clinical data for SPINRAZA and QALSODY, manufacture SPINRAZA and QALSODY, and successfully commercialize SPINRAZA and QALSODY. In general, we cannot control the amount and timing of resources that Biogen devotes to our collaborations. If Biogen fails to further develop SPINRAZA or QALSODY, obtain additional regulatory approvals for SPINRAZA or QALSODY, manufacture SPINRAZA or QALSODY, or successfully commercialize SPINRAZA or QALSODY, revenues for SPINRAZA or QALSODY would be negatively affected.

In addition, our collaborations with Biogen may not continue for various reasons. Biogen can terminate our collaborations at any time. If Biogen stops developing or commercializing SPINRAZA or QALSODY, we would have to seek or spend additional funding, and SPINRAZA’s or QALSODY’s commercialization may be harmed.

We depend on our collaboration with AstraZeneca for the joint development and commercialization of WAINUA.

We have entered into a collaborative arrangement with AstraZeneca to develop and commercialize WAINUA. Under the terms of the collaboration agreement, we and AstraZeneca are co-developing and co-commercializing WAINUA in the U.S. and AstraZeneca has the sole right to commercialize WAINUA in all other countries. As a company we do not have experience with co-commercialization arrangements. We also do not have control over (1) the amount and timing of resources that AstraZeneca devotes to our collaboration, particularly outside of the U.S; (2) the pricing and reimbursement strategies for WAINUA; and (3) whether AstraZeneca elects to terminate the collaborative arrangement. If the co-commercialization arrangement for WAINUA is not successful for any reason, WAINUA may not meet our commercial objectives and our revenues for WAINUA may be limited.

In addition, a Joint Steering Committee, or JSC, having equal membership from us and AstraZeneca, and various subcommittees oversee and coordinate the development, manufacturing, commercialization and other exploitation activities for WAINUA in the U.S. by mutual agreement. If any subcommittee cannot reach unanimous agreement on any matter within its respective scope of authority, such matter may be referred to the JSC for resolution. If the JSC cannot come to a mutual agreement on any particular matter, this could delay our ability to develop or commercialize WAINUA.

If we are not successful in expanding our manufacturing capabilities or cannot manufacture our medicines or contract with a third party to manufacture our medicines at costs that allow us to charge competitive prices to buyers, we cannot market our products profitably.

To successfully commercialize any of our medicines, we need to optimize and manage large-scale commercial manufacturing capabilities either on a standalone basis or through a third-party manufacturer. As our drug development and commercial pipeline increases and matures, we will have a greater need for clinical trial and commercial manufacturing capacity. We also must ensure that we have the manufacturing capabilities in place to support advances in our drug development activities, such as new chemistries. While we believe our current capabilities and those we obtain through third-party manufacturers support our manufacturing needs now, it will be important to expand our manufacturing infrastructure in the future, which will likely require substantial expenditures. If we are not successful in executing this expansion, or if the demand for any of our commercial medicines exceeds our expectations, it could limit our ability to meet our manufacturing requirements and commercial objectives in the future.

In addition, we have limited experience manufacturing pharmaceutical products of the chemical class represented by our medicines, called oligonucleotides, on a commercial scale for the systemic administration of a medicine. There are a small number of suppliers for certain capital equipment and raw materials that we use to manufacture our medicines, and some of these suppliers will need to increase their scale of production to meet our projected needs for commercial manufacturing. If a supplier chooses to devote more resources to other products, especially products with higher manufacturing capacity needs, that could impact such supplier’s capability to deliver our requirements timely. Further, we must continue to improve our manufacturing processes to allow us to reduce our drug costs. We or our partners may not be able to manufacture our medicines at a cost or in quantities necessary to make commercially successful products.

Manufacturers, including us, must adhere to the FDA’s cGMP regulations and similar regulations in foreign countries, which the applicable regulatory authorities enforce through facilities inspection programs. We, our partners and our contract manufacturers may not comply or maintain compliance with cGMP, or similar foreign regulations. Non-compliance could significantly delay or prevent receipt of marketing authorizations for our medicines, including authorizations for our commercial medicines and our medicines in development, or could result in enforcement action after authorization that might limit the commercial success of our medicines.

We rely on third-party manufacturers to supply the drug substance and drug product for TRYNGOLZA, DAWNZERA and WAINUA and drug product for WAYLIVRA. The operations of our suppliers, many of which are located outside of the United States, are subject to additional risks that are beyond our control. For example, tariffs on the raw materials, components, or equipment we use to manufacture our products, or on our drug substance or finished products, will increase our manufacturing costs. In addition, merger and acquisition activity within the commercial manufacturing space could reduce the availability of resources from our third-party manufacturers. Delays or disruption to our own or third-party commercial manufacturing capabilities for any reason could limit the commercial success of our medicines.

Risks Related to the Development and Regulatory Approval of our Medicines

If we or our partners fail to obtain regulatory approval for our medicines and additional approvals for our commercial medicines, we or our partners cannot sell them in the applicable markets.

We cannot guarantee that any of our medicines will be considered safe and effective or will be approved for commercialization. In addition, it is possible that our commercial medicines may not be approved in additional markets or for additional indications. We and our partners must conduct time-consuming, extensive and costly clinical studies to demonstrate the safety and efficacy of each of our medicines before they can be approved or receive additional approvals for sale. We and our partners must conduct these studies in compliance with FDA regulations and with comparable regulations in other countries.

We and our partners may not obtain necessary regulatory approvals on a timely basis, if at all, for our medicines. It is possible that regulatory authorities will not approve our medicines for marketing or our commercial medicines in additional markets or for additional indications. If the FDA or another regulatory authority believes that we or our partners have not sufficiently demonstrated the safety or efficacy of any of our medicines, including our commercial medicines or our medicines in development, the authority will not approve such medicine or will require additional studies, which could be time consuming and expensive and delay or harm commercialization of the medicine. For example, in August 2018 we received a complete response letter from the FDA regarding the new drug application for WAYLIVRA in which the FDA determined that the safety concerns identified with WAYLIVRA in our clinical development program outweighed the expected benefits of triglyceride lowering in patients with FCS. We also received a Notice of Non-Compliance Withdrawal Letter, or Non-W, from Health Canada for WAYLIVRA in November 2018.

The FDA or other comparable foreign regulatory authorities can delay, limit or deny approval of a medicine for many reasons, including:

• such authorities may disagree with the design or implementation of our clinical studies;
• we or our partners may be unable to satisfactorily demonstrate that a medicine is safe and effective for any indication;
• such authorities may not accept clinical data from studies conducted at clinical facilities that have deficient clinical practices or that are in countries where the standard of care is potentially different from the U.S.;
• we or our partners may be unable to demonstrate that our medicine’s clinical and other benefits outweigh its safety risks to support approval;
• such authorities may disagree with the interpretation of data from preclinical or clinical studies;
• such authorities may find deficiencies in the manufacturing processes or facilities of third-party manufacturers who manufacture clinical and commercial supplies for our medicines; and
• the approval policies or regulations of such authorities or their prior guidance to us or our partners during clinical development may significantly change in a manner rendering our clinical data insufficient for approval.

For example, while we continue to activate sites in the U.S., Canada, U.K., Australia and Japan, we revised and resubmitted the study protocol for the REVEAL study of obudanersen to address changes requested by EU regulators and plan to initiate EU sites for this study in 2026. Importantly, we believe we are on track to complete enrollment for this study in 2026.

Failure to receive marketing authorization for our medicines in development, or failure to receive additional marketing authorizations for our commercial medicines, or delays in these authorizations, could prevent or delay commercial introduction of the medicine, and, as a result, could negatively impact our ability to generate revenue from product sales.

If the results of clinical testing indicate that any of our medicines are not suitable for commercial use, we may need to abandon one or more of our drug development programs.

Drug discovery and drug development have inherent risks and the historical failure rate for drugs is high. Antisense medicines are a relatively new approach to therapeutics. If we cannot demonstrate that our medicines are safe and effective for human use in the intended indication(s), we may need to abandon one or more of our drug development programs.

Even if our medicines are successful in preclinical and human clinical studies, the medicines may not be successful in late-stage clinical studies. Similarly, topline, preliminary or interim data we release for any of our clinical studies may not be indicative of full or final results from such study.

Successful results in preclinical or initial human clinical studies, including the Phase 2 results for some of our medicines in development, may not predict the results of subsequent clinical studies. If any of our medicines in Phase 3 clinical studies do not show sufficient safety and efficacy in patients with the targeted indication, or if such studies are discontinued for any other reason, it could negatively impact our development and commercialization goals for these medicines and our stock price could decline. In addition, we may release topline, preliminary or interim data for any of our clinical studies. The interim, topline or preliminary results we report may differ from future results of the same studies, or different conclusions or considerations may qualify such results, once additional data have been received and fully evaluated. As a result, such data should be viewed with caution until the final data are available.

In the past, we have invested in clinical studies of medicines that have not met the primary clinical endpoints in their Phase 3 studies or have been discontinued for other reasons. For example, in October 2021, Biogen reported that QALSODY did not meet the primary clinical endpoint in the Phase 3 VALOR study; however, trends favoring QALSODY were seen across multiple secondary and exploratory measures of disease activity and clinical function. In addition, in March 2021, Roche decided to discontinue dosing in the Phase 3 GENERATION HD1 study of tominersen in patients with manifest Huntington’s disease based on the results of a pre-planned review of data from the Phase 3 study conducted by an unblinded Independent Data Monitoring Committee. Similar results could occur in clinical studies for our other medicines.

There are a number of factors that could cause a clinical study to fail or be delayed, including:

• the clinical study may produce negative or inconclusive results;
• regulators may require that we hold, suspend or terminate clinical research for noncompliance with regulatory requirements;
• we, our partners, the FDA or foreign regulatory authorities could suspend or terminate a clinical study due to adverse side effects of a medicine on subjects or lack of efficacy in the trial;
• we or our partners may decide, or regulators may require us, to conduct additional preclinical testing or clinical studies;
• enrollment in our clinical studies may be slower than we anticipate;
• we or our partners, including our independent clinical investigators, contract research organizations and other third-party service providers on which we rely, may not identify, recruit or train suitable clinical investigators at a sufficient number of study sites or timely enroll a sufficient number of study subjects in the clinical study;
• the institutional review board for a prospective site might withhold or delay its approval for the study;
• people who enroll in the clinical study may later drop out due to adverse events, a perception they are not benefiting from participating in the study, fatigue with the clinical study process or personal issues;
• a clinical study site may deviate from the protocol for the study;
• the cost of our clinical studies may be greater than we anticipate;
• our partners may decide not to exercise any existing options to license and conduct additional clinical studies for our medicines; and
• the supply or quality of our medicines or other materials necessary to conduct our clinical studies may be insufficient, inadequate or delayed.

Further, the FDA or other regulatory authorities could request, among other things, additional information or commitments before we can start or continue a clinical study, protocol amendments, increased safety monitoring, additional product labeling information, and post-approval commitments. This happened in connection with the conditional marketing approval for WAYLIVRA in the EU, as the European Commission is requiring us to conduct a post-authorization safety study to evaluate the safety of WAYLIVRA on thrombocytopenia and bleeding in FCS patients taking WAYLIVRA. In addition, under accelerated approval the FDA is requiring completion of the ongoing Phase 3 trial for QALSODY to confirm the clinical benefit of QALSODY.

Moreover, our commercial medicines are chemically similar to each other. As a result, a safety observation we encounter with one of our medicines could have, or be perceived by a regulatory authority to have, an impact on a different medicine we are developing. This could cause the FDA or other regulators to ask questions or take actions that could harm or delay our ability to develop and commercialize our medicines or increase our costs. Any failure or delay in our clinical studies could reduce the commercial potential or viability of our medicines.

We depend on third parties to conduct clinical studies for our medicines and any failure of those parties to fulfill their obligations could adversely affect our development and commercialization plans.

We depend on independent clinical investigators, contract research organizations and other third-party service providers to conduct our clinical studies for our medicines and expect to continue to do so in the future. For example, we use clinical research organizations, such as Icon Clinical Research Limited, Medpace, Inc., Parexel International Corporation, Syneos Health, Inc. and Thermo Fisher Scientific Inc. for the clinical studies for our medicines, including WAINUA for the treatment of ATTR-CM, DAWNZERA, obudanersen, olezarsen, ulefnersen and zilganersen. We rely heavily on these parties for successful execution of our clinical studies, but do not control many aspects of their activities. For example, the investigators are not our employees, but we are responsible for ensuring that such investigators conduct each of our clinical studies in accordance with the general investigational plan and approved protocols for the study. Third parties may not complete activities on schedule or may not conduct our clinical studies in accordance with regulatory requirements or our stated protocols. For example, some of our key vendors have in the past experienced labor shortages, which impacted their ability to perform services for us for certain of our clinical trials. Subsequent failures of these third parties to carry out their obligations, or a termination of our relationship with such third parties, could delay or prevent the development, marketing authorization and commercialization of our medicines.

In addition, while we do not have any clinical trial sites in Russia, Ukraine or Gaza, we do have a limited number of clinical trial sites in Israel that may be materially impacted by the ongoing military conflicts in Israel and elsewhere in the Middle East and could result in difficulties enrolling or completing our clinical trials in such areas on schedule.

Since corporate partnering is part of our strategy to fund the advancement and commercialization of some of our development programs, if any of our collaborative partners fail to fund our collaborative programs, or if we cannot obtain additional partners, we may have to delay or stop progress on those drug development programs.

To date, corporate partnering has played a significant role in our strategy to fund our development programs and to add key development resources. While we are now commercializing some of our medicines independently, we still plan to continue to rely on additional collaborative arrangements to develop and commercialize some of our unpartnered medicines. However, we may not be able to negotiate favorable collaborative arrangements for these drug programs. If we cannot continue to secure additional collaborative partners, our revenues could decrease and the development of our medicines could suffer.

Our corporate partners are developing and funding many of the medicines in our development pipeline. For example, we are relying on:

• AstraZeneca for the joint development and funding of WAINUA;
• Novartis for development and funding of pelacarsen;
• GSK for development and funding of bepirovirsen;
• Roche for development and funding of sefaxersen; and
• Otsuka for development and funding of ulefnersen.

If any of these pharmaceutical companies stops developing and funding these medicines, our business could suffer and we may not have, or be willing to dedicate, the resources available to develop these medicines on our own. Our collaborators can terminate their relationships with us under certain circumstances, many of which are outside of our control. For example, in 2025, Novartis decided to return the clinical development program for a follow on to pelacarsen, and in 2022, Pfizer and Bayer decided to discontinue the clinical development programs for vupanorsen and fesomersen, respectively.

Even with funding from corporate partners, if our partners do not effectively perform their obligations under our agreements with them, it would delay or stop the progress of our drug development and commercial programs.

In addition to receiving funding, we enter into collaborative arrangements with third parties to:

• conduct clinical studies;
• seek and obtain marketing authorizations; and
• manufacture and commercialize our medicines.

Once we have secured a collaborative arrangement to further develop and commercialize one of our drug development programs, such as our collaborations with AstraZeneca, Biogen, GSK, Novartis, Otsuka and Roche, these collaborations may not continue or result in commercialized medicines, or may not progress as quickly as we anticipated.

For example, a collaborator such as AstraZeneca, Biogen, GSK, Novartis, Otsuka or Roche, could determine that it is in its financial interest to:

• pursue alternative technologies or develop alternative products that may be competitive with the medicine that is part of the collaboration with us;
• pursue higher-priority programs or change the focus of its own development programs; or
• devote fewer resources to our medicines than it does to its own medicines.

If any of these occur, it could affect our partner’s commitment to the collaboration with us and could delay or otherwise negatively affect the commercialization of our medicines, including DAWNZERA, QALSODY, SPINRAZA, WAINUA, bepirovirsen, sefaxersen, pelacarsen and ulefnersen.

We may not be able to benefit from designations for our medicines from regulatory authorities that are intended to confer benefits such as financial incentives or an accelerated regulatory pathway.

In the U.S., under the Orphan Drug Act, the FDA may designate a medicine as an Orphan Drug if it is intended to treat a rare disease or condition affecting fewer than 200,000 individuals in the U.S. Orphan Drug designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval process, but it can provide financial incentives, such as tax advantages and user-fee waivers, as well as longer regulatory exclusivity periods. The FDA has granted Orphan Drug designation to TRYNGOLZA for the treatment of patients with FCS, to WAINUA for the treatment of patients with ATTR, to ulefnersen for the treatment of patients with FUS-ALS, to obudanersen for the treatment of patients with Angelman syndrome, and to some of our earlier stage medicines. The FDA and EMA have granted Orphan Drug designation to DAWNZERA for the treatment of patients with HAE, to WAYLIVRA for the treatment of patients with FCS, to tominersen for the treatment of patients with HD, and to some of our earlier stage medicines. In addition, the EMA has granted Orphan Drug designation to WAYLIVRA for the treatment of patients with FPL. Even if approval is obtained for a medicine that has been designated as an Orphan Drug, we may lose Orphan Drug exclusivity if the FDA or EMA determines that the request for designation was materially defective or if we cannot assure sufficient quantity of the applicable medicine to meet the needs of patients with the rare disease or condition, or if a competitor is able to gain approval for the same or a substantially similar medicine in a safer or more effective form or that makes a major contribution to patient care. If we lose Orphan Drug exclusivity on any of our medicines, we may face increased competition and lose market share for such medicine.

We may also seek rare pediatric disease designation for some of our medicines. The FDA defines “rare pediatric disease” as a serious or life-threatening disease in which the serious or life-threatening manifestations primarily affect individuals aged from birth to 18 years or is a rare disease or condition within the meaning of the Orphan Drug Act. Designation of a medicine as a medicine for a rare pediatric disease does not guarantee that a marketing application for such medicine will meet the eligibility criteria for a rare pediatric disease priority review voucher, or PRV, at the time the application is approved. Under the FDCA, we will need to request a rare pediatric disease PRV in our original marketing application for any potential medicine for which we have received rare pediatric disease designation. The FDA may determine that a marketing application for any such medicine, if approved, does not meet the eligibility criteria for a PRV. Under the current statutory sunset provisions, after December 20, 2024, the FDA may only award a PRV for an approved rare pediatric disease application if the sponsor has rare pediatric disease designation for the drug or biologic that is the subject of such application, and that designation was granted by December 20, 2024. After September 30, 2026, the FDA may not award any rare pediatric disease PRVs. However, it is possible the authority for the FDA to award rare pediatric disease PRV will be further extended by Congress.

Risks Associated with our Businesses as a Whole

Risks related to our financial condition

If we fail to obtain timely funding, we may need to curtail or abandon some of our programs.

Many of our medicines are undergoing clinical studies or are in the early stages of research and development. Most of our programs will require significant additional research, development, manufacturing, preclinical and clinical testing, marketing authorizations, preclinical activities and commitment of significant additional resources prior to their successful commercialization. In addition, as we commercialize more medicines on our own, we will need to invest significant financial resources to continue developing the infrastructure required to successfully commercialize our medicines, including building and maintaining new support functions, scaling up existing internal support functions and expanding our manufacturing capabilities. All of these activities will require significant cash. As of December 31, 2025, we had cash, cash equivalents and short-term investments equal to $2.7 billion. If we or our partners do not meet our goals to successfully commercialize our medicines, including our commercial medicines, or to license certain medicines and proprietary technologies, we will need additional funding in the future. Our future capital requirements will depend on many factors such as:

• successful commercialization of our commercial medicines;
• the profile and launch timing of our medicines in development;
• changes in existing collaborative relationships and our ability to establish and maintain additional collaborative arrangements;
• continued scientific progress in our research, drug discovery and development programs;
• the size of our programs and progress with preclinical and clinical studies;
• the time and costs involved in obtaining marketing authorizations;
• competing technological and market developments, including the introduction by others of new therapies that address our markets; and
• our manufacturing requirements and capacity to fulfill such requirements.

If we need additional funds, we may need to raise them through public or private financing. Additional financing may not be available on acceptable terms or at all. If we raise additional funds by issuing equity securities, the shares of existing stockholders will be diluted and the price, as well as the price of our other securities, may decline. For example, in September 2024, we completed an underwritten public offering of 11,500,000 shares of our common stock for total net proceeds, after deducting underwriting discounts and commissions and other offering expenses payable by us, of approximately $489.1 million. If adequate funds are not available or not available on acceptable terms, we may have to cut back on one or more of our research, drug discovery or development programs, or commercial operations. Alternatively, we may obtain funds through arrangements with collaborative partners or others, which could require us to give up rights to certain of our technologies or medicines.

We have incurred losses, and our business will suffer if we fail to consistently achieve profitability in the future.

Because drug discovery and development require substantial lead-time and money prior to commercialization, our expenses have generally exceeded our revenue since we were founded in January 1989. As of December 31, 2025, we had an accumulated deficit of approximately $2.6 billion and stockholders’ equity of approximately $0.5 billion. Most of our income has historically come from collaborative arrangements, including commercial revenue from royalties and R&D revenue, with additional income from research grants and the sale or licensing of our patents, as well as interest income. We will now and continuing into the foreseeable future need to invest significant financial resources to commercialize medicines on our own and expect that our income in the future will be driven primarily by commercial sales. If we do not earn substantial revenue from commercial sales, we may incur additional operating losses in the future, which could restrict our ability to successfully develop additional medicines or sustain future profitability.

We may not be entitled to obtain additional milestone payments under our royalty monetization agreement with Royalty Pharma.

In January 2023, we entered into a Royalty Purchase Agreement with Royalty Pharma Investments. In addition to the $500 million we received at closing, this agreement makes available to us up to an additional $625 million in milestone payments. However, these additional milestone payments are subject to satisfaction of certain conditions related to the regulatory approval or commercial sales of pelacarsen, in certain cases by specific deadlines. Should we not satisfy such conditions by the applicable deadlines, or if we fail to meet our obligations or default under this agreement, the actual amount of additional payments to us could be substantially less than the maximum amounts available thereunder.

Risks related to our intellectual property

If we cannot protect our patent rights or our other proprietary rights, others may compete more effectively against us.

Our success depends to a significant degree upon whether we can continue to develop, secure and maintain intellectual property rights to proprietary products and services. However, we may not receive issued patents on any of our pending patent applications in the U.S. or in other countries and we may not be able to obtain, maintain or enforce our patents and other intellectual property rights, any of which could impact our ability to compete effectively. In addition, the scope of any of our issued patents may not be sufficiently broad to provide us with a competitive advantage. Furthermore, other parties may successfully challenge, invalidate or circumvent our issued patents or patents licensed to us so that our patent rights do not create an effective competitive barrier or revenue source.

We cannot be certain that the U.S. Patent and Trademark Office, or U.S. PTO, and courts in the U.S. or the patent offices and courts in foreign countries will consider the claims in our patents and applications covering our commercial medicines, or any of our medicines in development, as patentable. Method-of-use patents protect the use of a product for the specified method. This type of patent does not prevent a competitor from making and marketing a product that is identical to our product for an indication that is outside the scope of the patented method. Moreover, even if competitors do not actively promote their product for our targeted indications, physicians may prescribe these products off-label. Although off-label prescriptions may infringe or contribute to the infringement of method-of-use patents, the practice is common and such infringement is difficult to prevent, even through legal action.

If we or any licensor partner loses or cannot obtain patent protection for our commercial medicines or any of our medicines in development, it could have a material adverse impact on our business.

Intellectual property litigation could be expensive and prevent us from pursuing our programs.

From time to time, we have to defend our intellectual property rights. If we are involved in an intellectual property dispute, we may need to litigate to defend our rights or assert them against others. Disputes can involve arbitration, litigation or proceedings declared by the U.S. PTO or the International Trade Commission or foreign patent authorities. Even if resolved in our favor, litigation or other legal proceedings relating to intellectual property claims may cause us to incur significant expenses and could distract our technical and management personnel from their normal responsibilities. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments and if securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our common stock. For example, in September 2025, we filed a claim against Arrowhead Pharmaceuticals, Inc., or Arrowhead, for patent infringement over Arrowhead's commercialization of plozasiran, and Arrowhead filed a separate lawsuit against us seeking to invalidate that same patent. For details regarding this proceeding, refer to Part IV, Item 15, Note 11, Legal Proceedings, in the Notes to the Consolidated Financial Statements.

If a third party claims that our medicines or technology infringe its patents or other intellectual property rights, we may have to discontinue an important product or product line, alter our products and processes, pay license fees or cease certain activities. We may not be able to obtain a license to needed intellectual property on favorable terms, if at all. There are many patents issued or applied for in the biotechnology industry, and we may not be aware of patents or patent applications held by others that relate to our business. This is especially true since patent applications in the U.S. are filed confidentially for the first 18 months. Moreover, the validity and breadth of biotechnology patents involve complex legal and factual questions for which important legal issues remain.

Risks related to product liability

We are exposed to potential product liability claims, and insurance against these claims may not be available to us at a reasonable rate in the future or at all.

Our business exposes us to potential product liability risks that are inherent in the testing, manufacturing, marketing and sale of therapeutic products, including potential product liability claims related to our commercial medicines and our medicines in development. We have clinical study insurance coverage and commercial product liability insurance coverage. However, this insurance coverage may not be adequate to cover claims against us, or be available to us at an acceptable cost, if at all. Regardless of their merit or eventual outcome, product liability claims may result in decreased demand for our medicines, injury to our reputation, withdrawal of clinical study volunteers and loss of revenues. Thus, whether or not we are insured, a product liability claim or product recall may result in losses that could be material.

Risks related to our personnel

The loss of key personnel, or the inability to attract and retain highly skilled personnel, could make it more difficult to run our business and reduce our likelihood of success.

We are dependent on the principal members of our management, scientific and commercial staff. We do not have employment agreements with any of our employees that would prevent them from leaving us. The loss of our key management, scientific or commercial employees might slow the achievement of important research and development or commercial goals. It is also critical to our success that we recruit and retain qualified scientific personnel to perform research and development work and that we recruit and retain qualified marketing, sales, market access, distribution, and related personnel to commercialize our medicines. We may not be able to attract and retain skilled and experienced personnel on acceptable terms because of intense competition for experienced personnel among many pharmaceutical and health care companies, universities and non-profit research institutions. In addition, failure to succeed in clinical studies or in commercializing our medicines may make it more challenging to recruit and retain qualified personnel.

Risks related to health epidemics, climate change and other events

Our business may be adversely affected by health epidemics, climate change, extreme weather events, fires, earthquakes, war, civil or political unrest, terrorism or disruptions of the U.S. government.

Our business could be adversely affected by health epidemics in regions where we or our partners are commercializing our medicines, have concentrations of clinical trial sites or other business operations, and could cause disruption in the operations of third-party manufacturers and contract research organizations upon whom we rely. For example, enrollment in some of our clinical trials was delayed due to the COVID-19 pandemic.

In recent years, extreme weather events and changing weather patterns have become more common. As a result, we are potentially exposed to varying natural disaster or extreme weather risks such as fires, hurricanes, tornadoes, droughts, floods, or other events that may result from the impact of climate change on the environment, any of which could impact our business and manufacturing operations. The potential impacts of climate change may also include increased operating costs associated with additional regulatory requirements and investments in reducing energy, water use and greenhouse gas emissions. In addition, we currently manufacture most of our research and clinical supplies in a manufacturing facility located in Carlsbad, California, and various regions within California have recently experienced numerous catastrophic wildfires. We manufacture the finished drug product for TRYNGOLZA, DAWNZERA, WAYLIVRA and eplontersen for ongoing clinical trials at third-party contract manufacturers. Biogen manufactures the finished drug product for SPINRAZA and QALSODY and AstraZeneca is responsible for WAINUA’s commercial drug supply. The facilities and the equipment we, our partners and our contract manufacturers use to research, develop and manufacture our medicines would be costly to replace and could require substantial lead time to repair or replace.

Our facilities or those of our partners or contract manufacturers may be harmed by natural disasters or other events outside our control, such as earthquakes, war, civil or political unrest, deliberate acts of sabotage, terrorism or industrial accidents such as fire and explosion, whether due to human or equipment error, and if such facilities are affected by a disaster or other event, our development and commercialization efforts would be delayed. Although we possess property damage and business interruption insurance coverage, this insurance may not be sufficient to cover all of our potential losses and may not continue to be available to us on acceptable terms, or at all.

In addition, our development and commercialization activities could be harmed or delayed by staffing shortages or a shutdown or other significant disruption of the U.S. government, including the FDA or the U.S. PTO.

Risks related to personal information, cybersecurity, social media and artificial intelligence

We are dependent on data as well as information technology systems and infrastructure, which exposes us to data protection risks.

We are dependent upon our own and third-party data as well as information technology systems and infrastructure, including mobile technologies, to operate our business. The personal information we process subjects us to stringent and evolving U.S. and foreign laws, rules and regulations, contractual obligations, industry standards and other obligations related to data privacy and security. Our obligations (including in relation to personal information) require us to maintain certain practices, including those in relation to cross-border transfers of data. The multitude and complexity of our information technology systems and infrastructure (including those of third parties with whom we work) make them vulnerable to a variety of evolving threats that may result in systems or data interruption, corruption, destruction, disruption of data integrity, malicious intrusion, or random attacks or other compromise (such as due to malfunctions, software vulnerabilities, natural disasters, telecommunications failures, malicious actors and personnel error). Data privacy or security incidents or breaches pose a risk that sensitive data, including our intellectual property, trade secrets or personal information of our employees, patients, customers or other business partners may be exposed to unauthorized persons. Cyber-attacks are increasing in their frequency, sophistication and intensity, particularly as companies (including us) continue to leverage remote work structures. In addition, the number and frequency of cybersecurity events globally may be heightened during times of geopolitical tension or instability between countries, including, for example, the ongoing war between Russia and Ukraine and military conflicts in the Middle East and the surrounding areas, or collectively, conflicts in Eastern Europe and the Middle East, as well as related political or economic responses and counter-responses by various global actors.

Cybersecurity related events could include the deployment or use of harmful malware or malicious code, denial-of-service attacks, credential stuffing attacks, credential harvesting attacks, social engineering attacks (including deep fakes and phishing attacks), ransomware and other means to affect, as applicable, the confidentiality, privacy, security, integrity or availability of our data as well as information systems and infrastructure (including that of third parties with whom we work). Our current, past and prospective business partners face similar risks and any security breaches of their systems (or those of third parties upon which they rely) could adversely affect our security posture. A security breach or a violation of obligations related to privacy or cybersecurity (including perceived breaches or violations) could result in any of the following, any of which could disrupt our business and result in increased costs or loss of revenue:

• harm our reputation;
• delay progress on the development of our medicines;
• compel us to comply with applicable security or data breach notification obligations (including laws);
• result in the diversion of monetary funds and other company resources;
• subject us to financial or other penalties, regulatory investigations or actions, including mandatory and costly corrective actions, and otherwise subject us to litigation or other liabilities; and
• require us to verify the correctness of database contents.

Risk mitigation strategies such as liability limitations in our contracts and insurance coverage may prove inadequate if there is a security breach or privacy violation. We do not maintain cyber insurance. While we have invested, and continue to invest, in the protection of our data and information technology systems and infrastructure as well as our compliance with relevant privacy and cybersecurity obligations, our efforts may not be successful. Non-compliance with relevant data protection obligations or a failure to secure our data, information technology systems or infrastructure could adversely affect our business and operations and result in the loss of critical or sensitive information, which could result in financial, legal, business or reputational harm to us.

The increasing use of social media platforms presents new risks and challenges.

Social media is increasingly being used to communicate about our medicines and the diseases our therapies are designed to treat. Social media practices in the biopharmaceutical industry continue to evolve and regulations relating to such use are not always clear and create uncertainty and risk of noncompliance with regulations applicable to our business. Despite our efforts to provide guidelines and training to our employees regarding social media use and monitor social media communications, there is risk that the unauthorized use of social media by our employees to communicate about our products or business, or any inadvertent disclosure of material, nonpublic information through these means, may result in violations of applicable laws and regulations, which may result in significant legal and financial exposure and reputational damages that could have a material adverse impact on our business. Furthermore, negative posts or comments about us or our medicines on social media could seriously damage our reputation, brand image and goodwill. If any of these events were to occur or we otherwise fail to comply with applicable regulations, we could incur liability, face restrictive regulatory actions or incur other harm to our business.

We use artificial intelligence in certain aspects of our business, and challenges with properly managing its use could adversely affect our business.

We incorporate artificial intelligence, or AI, solutions into certain aspects of our business, and applications of AI may become important in our operations over time. Our competitors or other third parties may incorporate AI into their businesses more quickly or more successfully than us, which could impair our ability to compete effectively and adversely affect our results of operations.

There are also significant risks involved in developing and deploying AI, and there can be no assurance that the usage of AI will enhance our medicines or the discovery or development of our product candidates or be beneficial to our business, including our efficiency or profitability. It is also uncertain how various laws will apply to content generated by AI. Various governmental authorities have proposed or enacted laws governing the development and use of AI technologies. We are subject to the risks of new or enhanced governmental or regulatory scrutiny, litigation, or other legal liability, ethical concerns, negative consumer perceptions as to automation and AI, or other complications that could adversely affect our business, reputation, or financial results.

Risks related to our securities and the global credit markets

If we do not progress in our programs as anticipated, the price of our securities could decrease.

For planning purposes, we estimate and may disclose the timing of a variety of clinical, regulatory and other milestones, such as when we anticipate a certain medicine will enter clinical trials, when we anticipate disclosing clinical data, when we anticipate completing a clinical study, when we anticipate filing an application for, or obtaining, marketing authorization, or when we or our partners plan to commercially launch a medicine. We base our estimates on present facts and a variety of assumptions, many of which are outside of our control. If we do not achieve milestones in accordance with our or our investors’ or securities analysts’ expectations, including milestones related to our commercial medicines and medicines in development, the price of our securities could decrease. In addition, our share price may be dependent upon the valuations and recommendations of the analysts who cover our business. If our results do not meet these analysts’ forecasts, the expectations of our investors or the financial guidance we provide to investors in any period, the market price of our common stock could decline. Our ability to meet analysts’ forecasts, investors’ expectations and our financial guidance is substantially dependent on our ability to maintain or increase sales of our commercial medicines, both partnered and unpartnered.

If the price of our securities continues to be highly volatile, this could make it harder to liquidate your investment and could increase your risk of suffering a loss.

The market price of our common stock, like that of the securities of many other biopharmaceutical companies, has been and is likely to continue to be highly volatile. These fluctuations in our common stock price may significantly affect the trading price of our securities. During the 12 months preceding December 31, 2025, the closing market price of our common stock ranged from $82.73 to $25.51 per share. Many factors can affect the market price of our securities, including, for example, fluctuations in our operating results, financing transactions, announcements of collaborations, clinical study results, technological innovations or new products being developed by us or our competitors, the commercial success of our approved medicines, governmental regulation, marketing authorizations, changes in payers’ reimbursement policies, developments in patent or other proprietary rights and public concern regarding the safety of our medicines.

Broad market factors may materially harm the market price of our common stock irrespective of our operating performance. For example, events such as recent tariffs announcements and the ongoing conflicts in Eastern Europe and the Middle East have caused disruptions of global financial markets and resulted in increased volatility in the trading price of our common stock. In addition, industry factors may materially harm the market price of our common stock. Nasdaq, and the market for biotechnology companies in particular, have historically experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of the particular companies affected. The trading prices and valuations of these stocks, and of ours, may not be predictable. A loss of investor confidence in the market for biotechnology or pharmaceutical stocks or the stocks of other companies that investors perceive to be similar to us, the opportunities in the biotechnology and pharmaceutical market or the stock market in general, could depress our stock price regardless of our business, prospects, financial conditions or results of operations.

Negative conditions in the global credit markets and financial services and other industries may adversely affect our business, financial condition or stock price.

The global credit and financial markets have experienced extreme volatility and disruptions recently, including as a result of tariffs announcements and the ongoing conflicts in Eastern Europe and the Middle East. These disruptions can result in severely diminished liquidity and credit availability, declines in consumer confidence, declines in economic growth, increases in unemployment rates and uncertainty about economic stability. There can be no assurance that further deterioration in credit and financial markets and confidence in economic conditions will not occur. If the current equity and credit markets deteriorate, it may make any necessary debt or equity financing more difficult, more costly and more dilutive. Failure to secure any necessary financing in a timely manner and on favorable terms could have a material adverse effect on our operations, growth plans, financial performance or stock price. In addition, our insurance carriers and insurance policies covering all aspects of our business may become financially unstable or may not be sufficient to cover any or all of our losses and may not continue to be available to us on acceptable terms, or at all.

A variety of risks associated with operating our business and marketing our medicines internationally could adversely affect our business. In addition to our U.S. operations, we are commercializing WAYLIVRA in the EU, Latin America and certain Caribbean countries. We face risks associated with our international operations, including possible unfavorable regulatory, pricing and reimbursement, political, tax and labor conditions, which could harm our business. Because we have international operations, we are subject to numerous risks associated with international business activities, including:

• compliance with differing or unexpected regulatory requirements for our medicines and foreign employees;
• complexities associated with managing multiple payer reimbursement regimes, government payers or patient self-pay systems;
• difficulties in staffing and managing foreign operations;
• in certain circumstances, increased dependence on the commercialization efforts and regulatory compliance of third-party distributors or strategic partners;
• foreign government taxes, regulations and permit requirements;
• U.S. and foreign government tariffs, trade and export restrictions, price and exchange controls and other regulatory requirements;
• U.S. restrictions on the use of certain foreign biotech equipment and service providers, such as those set forth in the BIOSECURE Act;
• anti-corruption laws, including the Foreign Corrupt Practices Act, or the FCPA, and its equivalent in foreign jurisdictions;
• economic weakness, including inflation, natural disasters, war, acts of terrorism, political instability or public health issues or health epidemics, in particular foreign countries or globally;
• fluctuations in currency exchange rates, which could result in increased operating expenses and reduced revenue, and other obligations related to doing business in another country;
• the potential for a local seller, faced with higher local prices, importing medicines from an international market with lower prices rather than buying such medicines locally, which is referred to as parallel importation;
• compliance with tax, employment, privacy, immigration and labor laws, regulations and restrictions for employees living or traveling abroad;
• workforce uncertainty in countries where labor unrest is more common than in the U.S.; and
• changes in diplomatic and trade relationships.

Our business activities outside of the U.S. are subject to the FCPA and similar anti-bribery or anti-corruption laws, regulations or rules of other countries in which we operate, including the United Kingdom’s Bribery Act 2010. In many other countries, the healthcare providers who prescribe pharmaceuticals are employed by their government, and the purchasers of pharmaceuticals are government entities; therefore, any dealings with these prescribers and purchasers may be subject to regulation under the FCPA. There is no certainty that all employees and third-party business partners (including our contract research organizations, contract manufacturing organizations, distributors, wholesalers, agents, contractors and other partners) will comply with anti-bribery laws. Importantly, we do not control the actions of manufacturers and other third-party agents, although we may be liable for their actions. Violation of these laws may result in civil or criminal sanctions, which could include monetary fines, criminal penalties, and disgorgement of past profits, which could have an adverse impact on our business and financial condition.

Provisions in our certificate of incorporation, bylaws, convertible notes documents, call spread hedge transaction documents and Delaware law may prevent stockholders from receiving a premium for their shares.

Our certificate of incorporation provides for classified terms for the members of our board of directors. Our certificate also includes a provision that requires at least 66 2/3 percent of our voting stockholders to approve a merger or certain other business transactions with, or proposed by, any holder of 15 percent or more of our voting stock, except in cases where certain directors approve the transaction or certain minimum price criteria and other procedural requirements are met.

Our certificate of incorporation also requires that any action required or permitted to be taken by our stockholders must be taken at a duly called annual or special meeting of stockholders and may not be taken by written consent. In addition, only our board of directors, chairperson of the board or chief executive officer can call special meetings of our stockholders. We have in the past, and may in the future, implement a stockholders’ rights plan, also called a poison pill, which could make it uneconomical for a third party to acquire our company on a hostile basis. In addition, our board of directors has the authority to fix the rights and preferences of, and issue shares of preferred stock, which may have the effect of delaying or preventing a change in control of our company without action by our stockholders.

The provisions of our convertible senior notes could make it more difficult or more expensive for a third party to acquire us. Upon the occurrence of certain transactions constituting a fundamental change, holders of the notes will have the right, at their option, to require us to repurchase all of their notes or a portion of their notes, which may discourage certain types of transactions in which our stockholders might otherwise receive a premium for their shares over the then-current market prices.

In 2025, we completed a $770 million offering of 0% Notes due 2030 and used $267.6 million of the net proceeds from the issuance of the 0% Notes due 2030 to repurchase $200 million of our 0% Notes due 2026. In 2023, we completed a $575 million offering of 1.75% Notes due 2028 and used $488.2 million of the net proceeds from the issuance of the 1.75% Notes due 2028 to repurchase $504.4 million of our 0.125% Notes due 2024. In 2024, we used $44.5 million of the net proceeds to settle the remaining principal balance of our 0.125% Notes due 2024 upon maturity. In 2021, we completed a $632.5 million offering of 0% Notes due 2026 and used $319.0 million of the net proceeds from the issuance of the 0% Notes due 2026 to repurchase the remaining $309.9 million of our 1% Notes due 2021. Additionally, in connection with the pricing of our 0% Notes due 2026, we entered into call spread transactions in which we purchased note hedges and sold warrants. Terminating or unwinding the call spread transactions for our 0% Notes due 2026 could require us to make substantial payments to the counterparties under those agreements or may increase our stock price. The costs or any increase in stock price that may arise from terminating or unwinding such agreements could make an acquisition of our company significantly more expensive to the purchaser.

These provisions, as well as Delaware law, including Section 203 of the Delaware General Corporation Law, and other of our agreements, may discourage certain types of transactions in which our stockholders might otherwise receive a premium for their shares over then-current market prices, and may limit the ability of our stockholders to approve transactions that they think may be in their best interests.

Future sales of our common stock in the public market could adversely affect the trading price of our securities.

Future sales of substantial amounts of our common stock in the public market, or the perception that such sales could occur, could adversely affect trading prices of our securities. For example, we may issue approximately 26.0 million shares of our common stock upon conversion of our 0% Notes due 2030, 1.75% Notes due 2028 and 0% Notes due 2026. In connection with the issuance of the 0% Notes due 2026, we entered into certain call spread transactions covering 10.9 million shares that we expect will offset the dilution to holders of common stock upon any conversion of those notes. However, the anti-dilutive effect of the convertible note hedges is offset by certain warrant transactions we entered into in connection with the issuance of the 0% Notes due 2026. The addition of any of these shares into the public market may have an adverse effect on the price of our securities.

In addition, pursuant to the call spread transactions we entered into in connection with the pricing of our 0% Notes due 2026, the counterparties are likely to modify their hedge positions from time to time at or prior to the conversion or maturity of the notes by purchasing and selling shares of our common stock, other of our securities, or other instruments, including over-the-counter derivative instruments, that they may wish to use in connection with such hedging, which may have a negative effect on the conversion value of those notes and an adverse impact on the trading price of our common stock. The call spread transactions are expected generally to reduce potential dilution to holders of our common stock upon any conversion of our 0% Notes due 2026 or offset any cash payments we are required to make in excess of the principal amount of the converted 0% Notes due 2026, as the case may be. However, the warrant transactions could separately have a dilutive effect to the extent that the market value per share of our common stock exceeds the applicable strike price of the warrants.

Risks related to compliance with laws

Our operations are subject to extensive legal and regulatory requirements affecting the health care industry.

Our operations are subject to extensive legal and regulatory requirements affecting the health care industry, including federal, state, and foreign fraud and abuse (including anti-kickback laws and false claims laws), transparency laws, such as the federal Sunshine Act, and health information privacy and security laws, which are subject to change at any time. It is possible that governmental authorities will conclude that our business practices may not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. Penalties for violations of applicable healthcare laws and regulations may include significant civil, criminal and administrative penalties, damages, disgorgement, fines, imprisonment, exclusion of products from government funded healthcare programs, such as Medicare and Medicaid, and additional reporting requirements and oversight if we enter into a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws. In addition, violations may also result in reputational harm, diminished profits and future earnings.

Because we use biological materials, hazardous materials, chemicals and radioactive compounds, if we do not comply with laws regulating the protection of the environment and health and human safety, our business could be adversely affected.

Our research, development and manufacturing activities involve the use of potentially harmful biological materials as well as materials, chemicals and various radioactive compounds that could be hazardous to human health and safety or the environment. We store most of these materials and various wastes resulting from their use at our facilities in Carlsbad, California pending ultimate use and disposal. We cannot completely eliminate the risk of contamination, which could cause:

• interruption of our research, development and manufacturing efforts;
• injury to our employees and others;
• environmental damage resulting in costly clean up; and
• liabilities under federal, state and local laws and regulations governing health and human safety, as well as the use, storage, handling and disposal of these materials and resultant waste products.

In such an event, we may be held liable for any resulting damages, and any liability could exceed our resources. Although we carry insurance for pollution liability in amounts and types that we consider commercially reasonable, the coverage or coverage limits of our insurance policies may not be adequate. If our losses exceed our insurance coverage, our financial condition would be adversely affected.

Our business is subject to changing regulations for corporate governance and public disclosure that has increased both our costs and the risk of noncompliance.

Each year we are required to evaluate our internal control systems to allow management to report on, and our Independent Registered Public Accounting Firm to attest to, our internal controls as required by Section 404 of the Sarbanes-Oxley Act. As a result, we continue to incur additional expenses and divert our management’s time to comply with these regulations. In addition, if we cannot continue to comply with the requirements of Section 404 in a timely manner, we might be subject to sanctions or investigation by regulatory authorities, such as the SEC, the Public Company Accounting Oversight Board, or PCAOB, or The Nasdaq Global Select Market. Any such action could adversely affect our financial results and the market price of our common stock.

The SEC and other regulators have continued to adopt new rules and regulations and make additional changes to existing regulations that require our compliance. In July 2010, the Dodd-Frank Wall Street Reform and Protection Act, or the Dodd-Frank Act, was enacted, and in August 2022, the SEC adopted additional rules and regulations under the Dodd-Frank Act related to “say on pay” and proxy access. Stockholder activism, the current political environment and the current high level of government intervention and regulatory reform may lead to substantial new regulations and disclosure obligations, which has and may in the future lead to additional compliance costs and impact the manner in which we operate our business.

Risks related to taxes

Our ability to use our net operating loss carryovers and certain other tax attributes may be limited.

Under the Internal Revenue Code of 1986, as amended, or the Code, a corporation is generally allowed a deduction for net operating losses, or NOLs, carried over from a prior taxable year. Under the Code, we can carry forward our NOLs to offset our future taxable income, if any, until such NOLs are used or expire. The same is true of other unused tax attributes, such as tax credits.

Under the current U.S. federal income tax law, U.S. federal NOLs generated in taxable years beginning after December 31, 2017 may be carried forward indefinitely, but the deductibility of such U.S. federal NOLs is limited to 80 percent of taxable income.

In addition, under Sections 382 and 383 of the Code, and corresponding provisions of state law, if a corporation undergoes an “ownership change,” which is generally defined as a greater than 50 percentage-point cumulative change, by value, in its equity ownership over a three-year period, the corporation’s ability to use its pre-change NOL carryforwards and other pre-change tax attributes to offset its post-change income or taxes may be limited. We may experience ownership changes in the future as a result of subsequent shifts in our stock ownership, some of which may be outside of our control. If an ownership change occurs and our ability to use our NOL carryforwards or other tax attributes is materially limited, it would harm our future operating results by effectively increasing our future tax obligations. As a result of our merger with Akcea Therapeutics, Inc. in 2020, or the Akcea Merger, we are subject to the separate return limitation year, or SRLY, rules. Under the SRLY rules, our utilization of Akcea’s pre-merger NOL and tax credit carryforwards is limited to the amount of income that Akcea contributes to our consolidated taxable income. The Akcea pre-merger tax attributes cannot be used to offset any of the income that Ionis contributes to our consolidated taxable income. In addition, at the state level, there may be periods during which the use of NOLs is suspended or otherwise limited, which could accelerate or permanently increase state taxes owed. For example, in June 2024, California enacted Senate Bill 167, or SB 167, which, with certain exceptions, suspends the ability to use California net operating losses to offset California income and limits the ability to use California business tax credits to offset California taxes, for taxable years beginning after 2023 and before 2027.

Our future taxable income could be impacted by changes in tax laws, regulations and treaties.

A change in tax laws, treaties or regulations, or their interpretation, of any country in which we operate could materially affect us.

We could be subject to additional tax liabilities.

We are subject to U.S. federal, state, local and foreign income taxes, sales taxes in the U.S., withholding taxes and transaction taxes in foreign jurisdictions. Significant judgment is required in evaluating our tax positions and our worldwide provision for taxes. During the ordinary course of business, there are many activities and transactions for which the ultimate tax determination is uncertain. In addition, our tax obligations and effective tax rates could be adversely affected by changes in the relevant tax, accounting and other laws, regulations, principles and interpretations, including those relating to income tax nexus, by recognizing tax losses or lower than anticipated earnings in jurisdictions where we have lower statutory rates and higher than anticipated earnings in jurisdictions where we have higher statutory rates, by changes in foreign currency exchange rates, or by changes in the valuation of our deferred tax assets and liabilities. In particular, our tax obligations and effective tax rate in the jurisdictions in which we conduct business could increase in the future as a result of the base erosion and profit shifting, or BEPS, project led by the Organization for Economic Co-operation and Development, or OECD, and other initiatives led by the OECD or the European Commission. The OECD is leading work on an iteration of the BEPS project based on two “pillars” (subject to certain revenue thresholds), involving, among other measures, the reallocation of taxing rights in respect of certain multinational enterprises above a fixed profit margin to the jurisdictions in which they carry on business (referred to as “Pillar One”) and imposition of a minimum effective corporate tax rate on certain multinational enterprises (referred to as “Pillar Two”). A number of countries in which we conduct business have enacted, or are in the process of enacting, core elements of the Pillar Two rules (with further provisions expected to be enacted in the future). Based on the minimum revenue thresholds we currently expect to fall within the scope of these requirements in the near term. The OECD has issued (and is expected to continue to issue further) administrative guidance providing transition and safe harbor rules in relation to the implementation of the Pillar Two proposal. For example, in January 2026, the OECD issued administrative guidance providing for, among other things, a side-by-side framework intended to limit the application of Pillar Two top-up taxes to U.S.-parented groups; however, the ultimate impact will depend on jurisdictional adoption and further guidance. We are monitoring developments and evaluating the potential impacts of the Pillar Two rules, including on our effective tax rates, and considering our eligibility to qualify for these safe harbor rules (including under the proposed “side-by-side” arrangement).

We may be audited in various jurisdictions, and such jurisdictions may assess additional income, sales and value-added or other taxes against us. In addition, we are currently under examination by the Internal Revenue Service for tax year 2023. Although we believe our tax estimates are reasonable, the final determination of any tax audits or litigation could be materially different from our historical tax provisions and accruals, which could have a material adverse effect on our operating results or cash flows in the period for which a determination is made.

Risk management and strategy

We have implemented and maintain various information security processes designed to detect, respond to, recover, and protect our technology ecosystem from cybersecurity threats. These processes are designed to identify, assess, and manage material risks that may result from cybersecurity threats and apply to our critical technologies inclusive of networks, third party hosted services, communications systems, hardware, software, and critical data, including intellectual property and confidential information that is proprietary, strategic, or competitive in nature.

Our Information Technology department, led by our Senior Vice President, Information Technology, helps to detect, respond to, and manage cybersecurity threats and risks by monitoring and evaluating our threat environment using various manual and automated tools in certain environments and systems and other methods including, for example:

• analyzing reports of certain threats and actors;
• conducting scans of the threat environment;
• evaluating our and our industry's risk profile;
• evaluating certain threats reported to us;
• conducting internal and external audits;
• conducting threat assessments for certain internal and external threats; and
• conducting vulnerability assessments designed to identify vulnerabilities.

Depending on the environment, system and data, we have implemented and maintain various technical, physical, and organizational measures, processes, standards, and policies designed to manage and mitigate material risks from cybersecurity threats to our critical technologies and data, including, for example:

• incident response plan;
• disaster recovery/business continuity plans;
• risk assessments;
• encryption of certain data;
• network security and access controls for certain systems;
• physical security;
• asset management, tracking and disposal;
• systems monitoring; and
• employee training.

Our assessment and management of material risks from cybersecurity threats are integrated into the Company’s overall risk management processes. For example, cybersecurity risk is assessed as a component of our enterprise risk management program. In addition, we have developed a process whereby our senior management evaluates material risks from cybersecurity threats against our overall business objectives and reports certain cybersecurity incidents to the Audit Committee of the Board of Directors, which evaluates our overall enterprise risk.

We use third-party providers to perform various functions throughout our business, such as application providers and hosting companies. We use third-party providers to assist us from time to time in an effort to identify, assess, and manage material risks from cybersecurity threats, including, for example, legal counsel, cybersecurity consultants, cybersecurity software providers, penetration testing firms, and forensic investigators. The Company maintains a risk-based approach and process designed to identify and oversee cybersecurity risks presented by third parties, including vendors, service providers and other external users of the Company’s systems, as well as the systems of third parties that could materially impact our business if there is a cybersecurity incident affecting those third-party systems.

For an additional description of the risks from cybersecurity threats that may materially affect us and how they may do so, see our risk factors under Item 1A, Risk Factors, in this Annual Report on Form 10-K, including the risk factor titled “We are dependent on data as well as information technology systems and infrastructure, which exposes us to data protection risks.”

Governance

Our Board of Directors addresses our cybersecurity risk management as part of its general oversight function. The Audit Committee of the Board of Directors is responsible for overseeing our cybersecurity risk management processes, including oversight and mitigation of risks from cybersecurity threats. The Audit Committee also oversees our internal audit department and management’s internal controls over financial reporting, including with respect to cybersecurity.

Our cybersecurity risk assessment and management processes are implemented and maintained by our Senior Vice President, Information Technology, who holds an undergraduate degree in Computer Engineering and has served in information technology and security roles dedicated to the pharmaceutical and biotechnology sector for approximately 18 years, including serving as the Chief Information Officer of two public biopharmaceutical companies.

Our Senior Vice President, Information Technology is responsible for hiring appropriate personnel, helping to integrate cybersecurity risk considerations into our overall risk management strategy, communicating key priorities to relevant personnel, helping prepare for cybersecurity incidents, approving cybersecurity processes, and reviewing security assessments and other security-related reports.

Our cybersecurity incident response plan is designed to escalate certain cybersecurity incidents, depending on the circumstances, to our senior management team and Audit Committee of the Board of Directors. The Audit Committee of the Board of Directors receives reports from our Senior Vice President, Information Technology concerning our significant cybersecurity threats and risks (including certain cybersecurity threats) and the processes we have implemented that are designed to address them.

As of February 19, 2026, the following are the primary facilities in which we operate:

We believe that our current and future facilities will be adequate for the foreseeable future. Refer to Part IV, Section 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for details on our facilities.

For details of legal proceedings, refer to Part IV, Item 15, Note 11, Legal Proceedings, in the Notes to the Consolidated Financial Statements.

This financial review presents our operating results for each of the two years in the period ended December 31, 2025, and our financial condition as of December 31, 2025. Refer to Part II, Item 7, Management's Discussion and Analysis of Financial Condition and Results of Operations, in our 2024 Form 10-K for our results of operations for 2024 compared to 2023. Except for the historical information contained herein, the following discussion contains forward-looking statements that are subject to known and unknown risks, uncertainties and other factors that may cause our actual results to differ materially from those expressed or implied by such forward-looking statements. We discuss such risks, uncertainties and other factors throughout this report and specifically under Part I, Item 1A, Risk Factors. In addition, the following review should be read in conjunction with the information presented in our consolidated financial statements and the related notes to our consolidated financial statements included in Part II, Item 8, Financial Statements and Supplementary Data, of this report.

Overview

As noted in our Business Overview in Part I, Item 1, Business, for three decades, we have invented medicines that we believe bring better futures to people with serious diseases. Today, as a pioneer in RNA-targeted medicines, we continue to drive innovation in RNA therapies. We currently have seven marketed medicines: TRYNGOLZA, DAWNZERA, WAINUA, SPINRAZA, QALSODY, TEGSEDI and WAYLIVRA. We also have a rich innovative late- and mid-stage pipeline in neurology, cardiometabolic diseases and select areas of high patient needs. We currently have nine medicines in Phase 3 development and additional medicines in early and mid-stage development. Refer to Part I, Item 1, Business, for further details on our business and key developments in our medicines.

Results of Operations

The following table provides selected summary information from our consolidated statements of operations for 2025 and 2024 (in millions):

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Revenue

Total revenue for 2025 was $943.7 million compared to $705.1 million in 2024 and was comprised of the following (in millions):

Commercial revenue in 2025 increased 49 percent compared to 2024. This increase was primarily driven by TRYNGOLZA product sales and higher royalty revenue.

The remainder of our revenue came from programs under our R&D collaborations, including a $280 million upfront payment for the global license of sapablursen to Ono in the second quarter of 2025, reflecting the value that our pipeline and technology continues to generate.

WAINUA (Eplontersen) Collaboration with AstraZeneca

Our financial results for the years ended December 31, 2025 and 2024 reflected the cost-sharing provisions related to our collaboration with AstraZeneca to develop and commercialize WAINUA for the treatment of ATTR. Under the terms of the collaboration agreement, AstraZeneca was responsible for 55 percent of the costs associated with the ongoing global Phase 3 development program through December 31, 2025. After December 31, 2025, AstraZeneca is responsible for 75 percent and 87.5 percent of development costs in the U.S. and the rest of the world, respectively. Because we are leading and conducting the Phase 3 development program, we are recognizing as R&D revenue the percentage of cost-share funding AstraZeneca is responsible for, net of our share of AstraZeneca’s development expenses, in the same period we incur the related development expenses.

As AstraZeneca is responsible for the vast majority of the medical affairs and commercial costs in the U.S. and all costs associated with bringing WAINUA to market outside the U.S., we are recognizing cost-share funding we receive from AstraZeneca related to these activities as a reduction of our medical affairs and commercialization expenses, which we classify as R&D and selling, general and administrative, or SG&A, expenses, respectively. We expect our medical affairs and commercialization expenses to increase as WAINUA advances toward the market under our collaboration with AstraZeneca.

The following table sets forth information on revenue and expenses under this collaboration (in millions):

Our WAINUA joint development revenue in 2024 included a $30 million milestone payment from AstraZeneca that we earned when the Medicines and Healthcare products Regulatory Agency, or MHRA, approved WAINUA for ATTRv-PN in the UK as WAINZUA. Research and development expenses related to the Phase 3 development of WAINUA decreased in 2025 compared to 2024 as development activities related to ATTRv-PN continued to wind down with the commercial launch of WAINUA.

Operating Expenses

The following table sets forth information on operating expenses (in millions):

Operating expenses, excluding non-cash compensation expense related to equity awards, increased in 2025 compared to 2024. SG&A expenses increased year over year primarily due to the launches of TRYNGOLZA, DAWNZERA and WAINUA.

Non-cash compensation expense related to equity awards were essentially flat year over year due to increased headcount offset by a lower stock price on the grant date of annual equity awards in 2025 compared to 2024. We believe non-cash compensation expense related to equity awards is not indicative of our operating results or cash flows from our operations.

Cost of Sales

Our cost of sales is comprised of costs related to our commercial revenue, which consisted of manufacturing costs, transportation and freight, indirect overhead costs associated with the manufacturing and distribution of TRYNGOLZA, DAWNZERA, TEGSEDI and WAYLIVRA and associated period costs.

Costs of sales for recently launched products, such as TRYNGOLZA and DAWNZERA, does not include the full cost of manufacturing until we manufacture and sell additional inventory after exhausting pre-launch inventory, which we previously recorded as R&D expense.

The following table sets forth information on cost of sales (in millions):

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Research, Development and Patent Expenses

Our research, development and patent expenses consist of expenses for drug discovery, drug development, medical affairs, manufacturing and development chemistry and R&D support expenses.

The following table sets forth information on research, development and patent expenses (in millions):

Drug Discovery

We use our proprietary technologies to generate information about the function of genes and to determine the value of genes as drug discovery targets. We use this information to direct our own drug discovery research, and that of our partners. Drug discovery is also the function that is responsible for advancing our core technology. This function is also responsible for making investments in complementary technologies to expand the reach of our technologies.

The following table sets forth information on drug discovery expenses (in millions):

Drug discovery expenses, excluding non-cash compensation expense related to equity awards, increased in 2025 compared to 2024 as we continued to advance our technologies discussed above.

Drug Development

The following table sets forth drug development expenses, including expenses for our marketed medicines and those in Phase 3 development for which we have incurred significant costs (in millions):

Our development expenses, excluding non-cash compensation expense related to equity awards, decreased in 2025 compared to 2024 as several late-stage studies ended. We expect our development expenses will continue to stabilize as several late-stage studies end and we reallocate resources toward earlier stage programs.

We may conduct multiple clinical trials on a drug candidate, including multiple clinical trials for the various indications we may be studying. Furthermore, as we obtain results from trials, we may elect to discontinue clinical trials for certain drug candidates in certain indications in order to focus our resources on more promising drug candidates or indications. Our Phase 1 and Phase 2 programs are clinical research programs that fuel our Phase 3 pipeline. When our medicines are in Phase 1 or Phase 2 clinical trials, they are in a dynamic state in which we may adjust the development strategy for each medicine. Although we may characterize a medicine as “in Phase 1” or “in Phase 2,” it does not mean that we are conducting a single, well-defined study with dedicated resources. Instead, we allocate our internal resources on a shared basis across numerous medicines based on each medicine’s particular needs at that time. This means we are constantly shifting resources among medicines. Therefore, what we spend on each medicine during a particular period is usually a function of what is required to keep the medicines progressing in clinical development, not what medicines we think are most important. For example, the number of people required to start a new study is large, the number of people required to keep a study going is modest and the number of people required to finish a study is large. However, such fluctuations are not indicative of a shift in our emphasis from one medicine to another and cannot be used to accurately predict future costs for each medicine. Because we always have numerous medicines in preclinical and varying stages of clinical research, the fluctuations in expenses from medicine to medicine, in large part, offset one another. If we partner a medicine, it may affect the size of a trial, its timing, its total cost and the timing of the related costs.

Medical Affairs

Our medical affairs function is responsible for funding and coordinating investigator-sponsored trials, communicating scientific and clinical information to healthcare providers, medical professionals and patients, and managing publications.

The following table sets forth information on medical affairs expenses (in millions):

Medical affairs expenses, excluding non-cash compensation expense related to equity awards, increased in 2025 compared to 2024 as we continued advancing our late-stage pipeline.

Manufacturing and Development Chemistry

Expenditures in our manufacturing and development chemistry function consist primarily of personnel costs, specialized chemicals for oligonucleotide manufacturing, validation batches to support regulatory approvals, laboratory supplies and outside services. Our manufacturing and development chemistry function is responsible for providing drug supplies to drug development and our collaboration partners. Our manufacturing procedures include testing to satisfy good laboratory and good manufacturing practice requirements.

The following table sets forth information on manufacturing and development chemistry expenses (in millions):

Manufacturing and development chemistry expenses, excluding non-cash compensation expense related to equity awards, increased in 2025 compared to 2024 due to the timing of manufacturing performed by our contract manufacturing organizations for drug product and active pharmaceutical ingredients related to several late-stage programs. Refer to the section titled, Manufacturing, in Part I, Item 1, Business, for further details on the activities and types of costs we incur in our manufacturing process.

R&D Support

In our research, development and patent expenses, we include support costs such as rent, repair and maintenance for buildings and equipment, utilities, depreciation of laboratory equipment and facilities, amortization of our intellectual property, information technology costs, procurement costs and waste disposal costs. We call these costs R&D support expenses.

The following table sets forth information on R&D support expenses (in millions):

R&D support expenses, excluding non-cash compensation expense related to equity awards, increased in 2025 compared to 2024 primarily due to increased costs relating to computer software and licenses.

Selling, General and Administrative Expenses

SG&A expenses include personnel, information technology systems and outside costs associated with the commercialization and pre-commercialization activities for our medicines and costs to support our company, our employees and our stockholders including, legal, human resources, investor relations and finance. Additionally, we include in SG&A expenses such costs as rent, repair and maintenance of buildings and equipment, depreciation and utilities costs that we need to support the corporate functions listed above. We also include fees we owe under our in-licensing agreements related to SPINRAZA and QALSODY and cost sharing payments associated with the co-commercialization activities under our WAINUA collaboration with AstraZeneca.

The following table sets forth information on SG&A expenses (in millions):

SG&A expenses, excluding non-cash compensation expense related to equity awards, increased in 2025 compared to 2024 primarily due to the launches of TRYNGOLZA, DAWNZERA and WAINUA. We expect SG&A expenses to increase as we continue to invest in our independent commercial launches.

Investment Income

Investment income for 2025 was $97.8 million compared to $107.0 million for 2024. The decrease in investment income was primarily due to a decrease in interest rates associated with our investments during 2025 compared to 2024.

Interest Expense

The following table sets forth information on interest expense (in millions):

Interest Expense Related to Sale of Future Royalties

We recorded $73.3 million and $73.5 million of interest expense related to the sale of future royalties in 2025 and 2024, respectively. These amounts are related to the Royalty Pharma Investments, or Royalty Pharma, transaction, in which we sold a minority interest in our future SPINRAZA and pelacarsen royalties to Royalty Pharma for a $500 million upfront payment and $625 million of potential future payments. Refer to Part IV, Item 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for further details.

Gain (Loss) on Investments

We recorded a $10.2 million gain on investments and a $2.9 million loss on investments for 2025 and 2024, respectively. The period-over-period fluctuation in our gain (loss) on investments was primarily driven by changes in the fair value of our investments in privately held and publicly traded biotechnology companies.

Other Income (Expense)

In 2025, we completed a $770.0 million offering of our 0% Notes due 2030 and used $267.6 million of the net proceeds to repurchase $200.0 million in principal of our 0% Notes due 2026 at a premium. As a result of the repurchase, we recognized induced conversion expense of $16.3 million, which we recorded as other expense in our consolidated statement of operations for the year ended December 31, 2025. The induced conversion expense is the difference between the amount paid to repurchase the 0% Notes due 2026 and the if-converted value of the notes at the time that the debt repurchase terms were finalized. Refer to Part IV, Item 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for further details regarding our convertible debt.

Income Tax Expense (Benefit)

We recorded an income tax expense of $1.8 million for 2025 compared to an income tax benefit of $6.2 million for 2024.

The income tax expense for 2025 primarily relates to state income taxes, partially offset by a federal tax benefit related to a capital loss carryback. The income tax benefit for 2024 primarily related to adjustments to prior year tax return positions for the royalty purchase agreement with Royalty Pharma and deductions related to foreign SPINRAZA royalties.

In July 2025, H.R.1 - 119th Congress was signed into law, introducing significant changes to U.S. federal tax law. The new law restores current expensing of domestic R&D costs and allows us to accelerate the deduction for a significant amount of such costs we capitalized since 2022. These tax law changes did not have a material effect on our tax expense for the year ended December 31, 2025.

We continue to maintain a full valuation allowance on all our net deferred tax assets.

Net Loss and Net Loss per Share

We generated a net loss of $381.4 million for 2025 compared to $453.9 million for 2024. Our net loss decreased for 2025 compared to 2024 primarily due to factors discussed in the sections above. Basic and diluted net loss per share for 2025 were $2.38 compared to $3.04 for 2024. Our net loss per share decreased for 2025 compared to 2024 primarily due to factors discussed in the sections above.

Liquidity and Capital Resources

We have financed our operations primarily from research and development collaborative agreements. We also financed our operations from commercial revenue from SPINRAZA, WAINUA and QALSODY royalties and TEGSEDI and WAYLIVRA commercial revenue. In addition, we began earning commercial revenue from TRYNGOLZA product sales in late December 2024 and DAWNZERA product sales in late August 2025. From our inception through December 31, 2025, we have earned approximately $8.9 billion in revenue. We have also financed our operations through the sale of our equity securities, the issuance of long-term debt and the sale of future royalties. From the time we were founded through December 31, 2025, we have raised net proceeds of approximately $2.8 billion from the sale of our equity securities. Additionally, from our inception through December 31, 2025, we have borrowed approximately $3.5 billion under long-term debt arrangements and received proceeds of approximately $0.5 billion from the sale of future royalties to finance a portion of our operations.

Our working capital decreased from 2024 to 2025 as we reclassified our 0% Notes due 2026 from non-current liabilities to current liabilities in the second quarter of 2025 because the notes are due in April 2026. During the same period, our long-term obligations increased due to the issuance of our 0% Notes due 2030, which was partially offset by the partial repurchase of our 0% Notes due 2026, in the fourth quarter of 2025.

The following table summarizes our contractual obligations, excluding our liability related to the sale of future royalties, as of December 31, 2025. The table provides a breakdown of when obligations become due. We provide a more detailed description of the major components of our debt in Part IV, Item 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements.

Our contractual obligations consist primarily of our convertible debt. In addition, we also have a facility mortgage, facility leases, equipment financing arrangements and other obligations. In the third quarter of 2025, our build-to-suit lease in Carlsbad, California commenced, resulting in an increase to our contractual obligations related to operating leases. We believe our cash, cash equivalents and short-term investments, as well as plans for cash in the future, will be sufficient to fund our planned operations and these obligations. We have not entered into, nor do we currently have, any off-balance sheet arrangements (as defined under SEC rules).

Convertible Debt and Call Spread

Refer to our Convertible Debt and Call Spread accounting policies in Part IV, Item 15, Note 1, Organization and Significant Accounting Policies, and Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for the significant terms of each convertible debt instrument.

Operating Facilities

Refer to Part IV, Item 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for further details on our operating facilities.

Operating Leases

Refer to Part IV, Item 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for further details on our operating leases.

Royalty Revenue Monetization

In 2023, we entered into a royalty purchase agreement with Royalty Pharma to monetize a portion of our future SPINRAZA and pelacarsen royalties we are entitled to under our agreements with Biogen and Novartis, respectively. Refer to Part IV, Item 15, Note 7, Long-Term Obligations and Commitments, in the Notes to the Consolidated Financial Statements for further details on this agreement.

Other Obligations

In addition to contractual obligations, we had outstanding purchase orders as of December 31, 2025 for the purchase of services, capital equipment and materials as part of our normal course of business.

We may enter into additional collaborations with partners which could provide for additional revenue to us and we may incur additional cash expenditures related to our obligations under any of the new agreements we may enter into. We currently intend to use our cash, cash equivalents and short-term investments to finance our activities. However, we may also pursue other financing alternatives, like issuing additional shares of our common stock, issuing debt instruments, refinancing our existing debt, securing lines of credit or executing royalty monetization agreements. Whether we use our existing capital resources or choose to obtain financing will depend on various factors, including the future success of our business, the prevailing interest rate environment and the condition of financial markets generally.

Critical Accounting Estimates

We prepare our consolidated financial statements in conformity with accounting principles generally accepted in the U.S. As such, we make certain estimates, judgments and assumptions that we believe are reasonable, based upon the information available to us. These judgments involve making estimates about the effect of matters that are inherently uncertain and may significantly impact our quarterly or annual results of operations and financial condition. Each quarter, our senior management reviews the development, selection and disclosure of such estimates with the audit committee of our board of directors. In the following paragraphs, we describe the specific risks associated with these critical accounting estimates and we caution that future events rarely develop exactly as one may expect, and that best estimates may require adjustment. Our significant accounting policies are outlined in Part IV, Item 15, Note 1, Organization and Significant Accounting Policies, in the Notes to the Consolidated Financial Statements.

The following are our significant accounting estimates, which we believe are the most critical to aid in fully understanding and evaluating our reported financial results:

• Assessing the propriety of revenue recognition and associated deferred revenue;
• Determining the appropriate cost estimates for unbilled preclinical studies and clinical development activities; and
• Assessing the appropriate estimate of anticipated future royalty payments under our royalty purchase agreement.

The following are descriptions of our critical accounting estimates.

Revenue Recognition

We earn revenue from several sources. The judgements and estimates we make vary between each source of our revenue. At contract inception, we analyze our collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of Accounting Standards Codification, or ASC, Topic 808, Collaborative Arrangements, or ASC 808. For collaboration arrangements within the scope of ASC 808 that contain multiple elements, we first determine which elements of the collaboration reflect a vendor-customer relationship and are therefore within the scope of ASC 606, Revenue from Contracts with Customers. When we determine elements of a collaboration do not reflect a vendor-customer relationship, we consistently apply the reasonable and rational policy election we made by analogizing to authoritative accounting literature.

The following is a summary of the critical accounting estimates we make with respect to our revenue.

Research and development revenue under collaborative agreements

We recognize R&D revenue from numerous collaboration agreements. Our collaboration agreements typically contain multiple elements, or performance obligations, including technology licenses or options to obtain technology licenses, R&D services, and manufacturing services. Upon entering into a collaboration agreement, we are required to make the following judgements:

Identifying the performance obligations contained in the agreement

Our assessment of what constitutes a separate performance obligation requires us to apply judgement. Specifically, we have to identify which goods and services we are required to provide under the contract are distinct.

Determining the transaction price, including any variable consideration

To determine the transaction price, we review the amount of consideration we are eligible to earn under the agreement. We do not typically include any payments we may receive in the future in our initial transaction price since the payments are typically not probable because they are contingent upon certain future events. We reassess the total transaction price at each reporting period to determine if we should include additional payments in the transaction price that have become probable.

Allocating the transaction price to each of our performance obligations

When we allocate the transaction price to more than one performance obligation, we make estimates of the relative stand-alone selling price of each performance obligation because we do not typically sell our goods or services on a stand-alone basis. The estimate of the relative stand-alone selling price requires us in some cases to make significant judgements. For example, when we deliver a license at the start of an agreement, we use valuation methodologies, such as the relief from royalty method, to value the license. Under this method we are required to make estimates including future sales, royalties on future product sales, contractual milestones, expenses, income taxes and discount rates. Additionally, when we estimate the selling price for R&D services, we make estimates, including: the number of internal hours we will spend on the services, the cost of work we and third parties will perform and the cost of clinical trial material we will use.

The R&D revenue we recognize each period is comprised of several types of revenue, including amortization from upfront payments, milestone payments, license fees and other services that we recognize immediately or amortize over the period in which we satisfy our performance obligation. Each of these types of revenue require us to make various judgements and estimates.

R&D Services with Upfront Payments

We recognize revenue from the amortization of upfront payments as we perform R&D services. We use an input method to estimate the amount of revenue to recognize each period. This method requires us to make estimates of the total costs we expect to incur to complete our R&D services performance obligation or the total amount of effort it will take us to complete our R&D services performance obligation. If we change our estimates, we may have to adjust our revenue.

Milestone Payments

When recognizing revenue related to milestone payments, we typically make the following judgements and estimates:

Whether a milestone payment is probable (discussed in detail above under “Determining the transaction price, including any variable consideration”); and

If we are performing services, we recognize revenue over our estimated period of performance in a similar manner to the amortization of upfront payments (discussed above under “R&D Services with Upfront Payments”).

License Fees

When we grant a license for a medicine in clinical development, we generally recognize as R&D revenue the total amount we determine to be the relative stand-alone selling price of a license when we deliver the license to our partner. Refer to Part IV, Item 15, Note 1, Organization and Significant Accounting Policies, in the Notes to the Consolidated Financial Statements for our revenue recognition policy. We discuss the estimates we make related to the relative stand-alone selling price of a license in detail above under “Allocating the transaction price to each of our performance obligations.”

Estimated Liability for Clinical Development Costs

We have numerous medicines in preclinical studies and/or clinical trials at clinical sites throughout the world. On at least a quarterly basis, we estimate our liability for preclinical and clinical development costs we have incurred and services that we have received but for which we have not yet been billed and maintain an accrual to cover these costs. These costs primarily relate to third-party clinical management costs, laboratory and analysis costs, toxicology studies and investigator grants. We estimate our liability using assumptions about study and patient activities and the related expected expenses for those activities determined based on the contracted fees with our service providers. The assumptions we use represent our best estimates of the activity and expenses at the time of our accrual and involve inherent uncertainties and the application of our judgment. Upon settlement, these costs may differ materially from the amounts accrued in our consolidated financial statements. Our historical accrual estimates have not been materially different from our actual amounts.

As of December 31, 2025, a hypothetical 10 percent increase in our liability for preclinical and clinical development costs would have resulted in an increase in our loss before income tax benefit and accrued liabilities of approximately $5.4 million.

Liability Related to Sale of Future Royalties

In 2023, we entered into a royalty purchase agreement with Royalty Pharma to monetize a portion of our future SPINRAZA and pelacarsen royalties we are entitled to under our agreements with Biogen and Novartis, respectively. Under our agreement with Royalty Pharma, we calculate the liability related to the sale of future royalties, effective interest rate and the related interest expense using our current estimate of anticipated future royalty payments under the arrangement, which we periodically reassess based on internal projections and information from our partners who are responsible for commercializing the medicines. The amount that Royalty Pharma will receive under the agreement is based on sales of SPINRAZA, our currently commercialized medicine, and pelacarsen, a product candidate that is not currently commercialized. As such, the repayment amounts that we estimate related to projections of future pelacarsen revenues contain more subjective estimation which we believe could lead to larger changes in estimates in the future. If there is a material change in our estimate, we will prospectively adjust the effective interest rate and the related interest expense.

There are numerous factors, most of which are not within our control, that could materially impact the amount and timing of future royalty payments, particularly those from Novartis for pelacarsen, and could result in changes to our estimate of future royalty payments to Royalty Pharma. Such factors include, but are not limited to, the regulatory approval and commercial sales of pelacarsen, competing products or other significant events. These factors and other events or circumstances could result in reduced royalty payments from sales of pelacarsen, which would result in a reduction of our non-cash royalty revenue and non-cash interest expense over the life of the agreement. Conversely, if sales of pelacarsen are more than amounts we estimated, the non-cash royalty revenue and non-cash interest expense we record would be greater over the life of the arrangement.

We are exposed to changes in interest rates primarily from our investments in certain short-term investments. We primarily invest our excess cash in highly liquid short-term investments of the U.S. Treasury and reputable financial institutions, corporations, and U.S. government agencies with strong credit ratings. We typically hold our investments for the duration of the term of the respective instrument. We do not utilize derivative financial instruments, derivative commodity instruments or other market risk sensitive instruments, positions or transactions to manage exposure to interest rate changes. Accordingly, we believe that, while the securities we hold are subject to changes in the financial standing of the issuer of such securities, we were not subject to any material risks arising from changes in interest rates, foreign currency exchange rates, commodity prices, equity prices or other market changes that affect market risk sensitive instruments as of December 31, 2025 and will not be subject to any material risks arising from these changes in the foreseeable future.

Disclosure Controls and Procedures

We maintain disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended, or Exchange Act) that are designed to ensure that information we are required to disclose in our Exchange Act reports is recorded, processed, summarized and reported within the time periods specified in the SEC’s rules and forms, and that such information is accumulated and communicated to our management, including our Chief Executive Officer and Chief Financial Officer, as appropriate, to allow timely decisions regarding required disclosure. We designed and evaluated our disclosure controls and procedures recognizing that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance and not absolute assurance of achieving the desired control objectives.

As of the end of the period covered by this report on Form 10-K, we carried out an evaluation of our disclosure controls and procedures under the supervision of, and with the participation of our management, including our Chief Executive Officer and Chief Financial Officer. Based on our evaluation, our Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures were effective as of December 31, 2025.

Management’s Report on Internal Control over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over financial reporting, as defined in Exchange Act Rules 13a-15(f). Our internal control over financial reporting is a process designed under the supervision of our Chief Executive Officer and Chief Financial Officer, and effected by our board of directors, management and other personnel, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of our financial statements for external purposes in accordance with U.S. generally accepted accounting principles.

As of December 31, 2025, we assessed the effectiveness of our internal control over financial reporting based on the criteria for effective internal control over financial reporting under the 2013 “Internal Control—Integrated Framework,” issued by the Committee of Sponsoring Organizations, or COSO, of the Treadway Commission, under the supervision of, and with the participation of our management, including our Chief Executive Officer and Chief Financial Officer. Based on that assessment, our management concluded that we maintained effective internal control over financial reporting as of December 31, 2025.

Ernst & Young LLP, an independent registered public accounting firm, audited the effectiveness of our internal control over financial reporting as of December 31, 2025, as stated in their attestation report, which is included elsewhere herein.

Changes in Internal Control over Financial Reporting

The above assessment did not identify any change in our internal control over financial reporting that occurred during our latest fiscal quarter and that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Stockholders and the Board of Directors of Ionis Pharmaceuticals, Inc.

Opinion on Internal Control Over Financial Reporting

We have audited Ionis Pharmaceuticals, Inc.’s internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework) (the COSO criteria). In our opinion, Ionis Pharmaceuticals, Inc. (the Company) maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on the COSO criteria.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidated balance sheets of the Company as of December 31, 2025 and 2024, the related consolidated statements of operations, comprehensive loss, stockholders’ equity and cash flows for each of the three years in the period ended December 31, 2025, and the related notes and our report dated February 26, 2026 expressed an unqualified opinion thereon.

Basis for Opinion

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting included in the accompanying Management’s Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects.

Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

Definition and Limitations of Internal Control Over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

/s/ Ernst & Young LLP

San Diego, California

February 26, 2026