Ionis presents new long-term data supporting durable efficacy and disease control with DAWNZERA® (donidalorsen) at ACAAI 2026 Annual Meeting

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• DAWNZERA showed sustained HAE attack rate reduction and long-term safety over two years
• 71% HAE attack rate reduction maintained after two years on DAWNZERA compared to baseline for patients switching from another long-term prophylactic therapy
• Treatment effect maintained regardless of dosing frequency every four or eight weeks

CARLSBAD, Calif.--(BUSINESS WIRE)-- Ionis Pharmaceuticals, Inc. (Nasdaq: IONS) today announced new long-term data for DAWNZERA^® (donidalorsen), the first and only RNA-targeted medicine for hereditary angioedema (HAE), to be presented at the 2026 American College of Allergy, Asthma & Immunology (ACAAI) Annual Scientific Meeting in Phoenix, Arizona. Multiple presentations will demonstrate the long-term efficacy and safety of DAWNZERA in the OASISplus open-label extension (OLE) and switch cohorts over two years.

“People living with hereditary angioedema are faced with a chronic disease and need prophylactic therapy that will provide long-lasting disease control,” said Kenneth Newman, M.D., senior vice president, clinical development, Ionis. “These data demonstrate that DAWNZERA achieved durable efficacy and safety, not only when dosed every four weeks but also every eight weeks. In our switch study, patients who transitioned to DAWNZERA using a predefined protocol continue to experience lasting reductions in attack rates compared with baseline on their prior therapy.”

The OASISplus OLE cohort enrolled adult and adolescent patients continuing from the Phase 3 OASIS-HAE pivotal trial, who received DAWNZERA every four (Q4W) or every eight weeks (Q8W). A majority (84%) of patients remained in the study after two years, and patients in the OLE achieved a 95% overall reduction from baseline in HAE attack rates across both dosing groups (n=83).

The OASISplus switch cohort evaluated DAWNZERA in patients previously treated with lanadelumab, C1-esterase inhibitor or berotralstat who switched to DAWNZERA using a predefined protocol. After two years, 80% of patients remained in the switch cohort. Patients experienced an overall reduction in HAE attack rate of 71% from baseline on their prior long-term prophylactic therapy (n=64).

Ionis will also present a post hoc analysis of DAWNZERA in patients who were eligible to receive Q8W dosing in the OASISplus OLE and switch cohorts over two years of treatment. Patients who received DAWNZERA dosed every eight weeks at the start of the open-label extension maintained a 95% overall attack rate reduction over the two years, consistent with those who received DAWNZERA every four weeks.

Across these analyses, DAWNZERA maintained a favorable long-term safety and tolerability profile, with no new safety signals observed. The majority of treatment-emergent adverse events (TEAEs) were mild or moderate, with no serious TEAEs related to DAWNZERA.

All presentations are available on the Ionis website.

IMPORTANT SAFETY INFORMATION

CONTRAINDICATIONS

DAWNZERA is contraindicated in patients with a history of serious hypersensitivity reactions, including anaphylaxis, to donidalorsen or any of the excipients in DAWNZERA.

WARNINGS AND PRECAUTIONS

Hypersensitivity Reactions

Hypersensitivity reactions, including anaphylaxis, have been reported in patients treated with DAWNZERA. If signs and symptoms of serious hypersensitivity reactions occur, discontinue DAWNZERA and institute appropriate therapy.

ADVERSE REACTIONS

Most common adverse reactions (incidence ≥ 5%) are injection site reactions, upper respiratory tract infection, urinary tract infection, and abdominal discomfort.

Please see full Prescribing Information for DAWNZERA.

About Hereditary Angioedema (HAE)

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 7,000 people in the U.S.

About DAWNZERA^® (donidalorsen)

DAWNZERA^® (donidalorsen) is approved for prophylaxis to prevent attacks of hereditary angioedema (HAE) in adult and pediatric patients 12 years of age and older. DAWNZERA is an RNA-targeted medicine designed to target plasma prekallikrein (PKK), which plays an important role in activating inflammatory mediators associated with acute attacks of HAE. For more information about DAWNZERA, visit DAWNZERA.com.

About Ionis Pharmaceuticals, Inc.

For three decades, Ionis has invented medicines that bring better futures to people with serious diseases. Ionis has marketed medicines and a leading pipeline in neurology, cardiometabolic and other areas of high patient need. As the pioneer in RNA-targeted medicines, Ionis continues to drive innovation in RNA therapies in addition to advancing new approaches in gene editing. A deep understanding of disease biology and industry-leading technology propels our work, coupled with a passion and urgency to deliver life-changing advances for patients. To learn more about Ionis, visit Ionis.com and follow us on X (Twitter), LinkedIn and Instagram.

Forward-looking Statements

This press release includes forward-looking statements regarding Ionis' business and the therapeutic and commercial potential of DAWNZERA, our commercial medicines, additional medicines in development and technologies and our expectations regarding development and regulatory milestones. Any statement describing Ionis' goals, expectations, financial or other projections, intentions or beliefs is a forward-looking statement and should be considered an at-risk statement. Such statements are subject to certain risks and uncertainties including those inherent in the process of discovering, developing and commercializing medicines that are safe and effective for use as human therapeutics, and in the endeavor of building a business around such medicines. Ionis' forward-looking statements also involve assumptions that, if they never materialize or prove correct, could cause its results to differ materially from those expressed or implied by such forward-looking statements. Although Ionis' forward-looking statements reflect the good faith judgment of its management, these statements are based only on facts and factors currently known by Ionis. Except as required by law, we undertake no obligation to update any forward-looking statements for any reason. As a result, you are cautioned not to rely on these forward-looking statements. These and other risks concerning Ionis' programs are described in additional detail in Ionis' annual report on Form 10-K for the year ended December 31, 2025 and most recent Form 10-Q, which are on file with the Securities and Exchange Commission. Copies of these and other documents are available from the Company.

In this press release, unless the context requires otherwise, "Ionis," "Company," "we," "our" and "us" all refer to Ionis Pharmaceuticals and its subsidiaries.

Ionis Pharmaceuticals^® and DAWNZERA^® are trademarks of Ionis Pharmaceuticals, Inc.

View source version on businesswire.com: https://www.businesswire.com/news/home/20261111437603/en/

Ionis Investor Contact:
D. Wade Walke, Ph.D.
IR@ionis.com
760-603-2331

Ionis Media Contact:
Hayley Soffer
media@ionis.com
760-603-4679

Source: Ionis Pharmaceuticals, Inc.

Key Terms

hereditary angioedema medical

A rare inherited disorder that causes sudden, painful swelling under the skin or in internal tissues, including the airway, because a natural blood‑control protein is missing or not working. Attacks can be unpredictable and sometimes life‑threatening, so people often need ongoing medication or emergency treatment. For investors, hereditary angioedema represents a niche but stable market for specialized therapies, diagnostics, and emergency care solutions.

open-label extension medical

An open-label extension is a continuation of a clinical trial where all participants and researchers know which treatment is being given, often after an initial blinded phase. It allows further study of a drug's long-term safety and effectiveness. For investors, it can indicate ongoing interest and confidence in a product's potential, influencing perceptions of its future value.

treatment-emergent adverse events medical

Events or symptoms that either appear for the first time or get worse after a patient starts a treatment; think of new or intensified side effects that show up once medicine or a medical device is used. Investors watch these closely because they affect whether a therapy can gain regulatory approval, be prescribed widely, or face legal and commercial setbacks—similar to how early customer complaints can sink a new product’s prospects.

C1-esterase inhibitor medical

A C1-esterase inhibitor is a naturally occurring protein that acts like a brake on parts of the immune system to prevent excessive swelling and inflammation; therapeutically, it is given as a biologic drug to treat conditions such as hereditary angioedema. Investors care because it is a specialized, often high-cost biologic with complex manufacturing, tight regulation, and clear clinical endpoints—so trial results, approvals, supply and reimbursement decisions can materially affect a company’s revenue and valuation.