Ionis Pharmaceuticals, Inc. (Nasdaq: IONS) today announced new data to be presented for DAWNZERA™ (donidalorsen), the first and only RNA-targeted medicine for hereditary angioedema (HAE), including new analyses from the Phase 3 OASIS-HAE and OASISplus studies. Results will be presented at the 2026 American Academy of Allergy, Asthma & Immunology (AAAAI) Annual Meeting in Philadelphia, PA.

“These data add to a growing body of evidence outlining the clinical value of DAWNZERA for people living with HAE, highlighting its potential to deliver meaningful improvement in HAE attack rate and quality of life, including for those switching from another long-term prophylactic therapy,” said Kenneth Newman, M.D., senior vice president, clinical development, Ionis. “We know that patients continue to seek out a treatment that meaningfully reduces attack frequency and severity while also addressing the administration and lifestyle burden of long-term therapy. The breadth of data being presented at AAAAI underscores the potential for DAWNZERA to meet these needs and to be the prophylactic treatment of choice for many people living with HAE.”

Ionis will have eight poster presentations, as follows. All final posters are available on the Ionis website.

• Additional Benefit of Switching to Donidalorsen for Patients with Hereditary Angioedema Having Breakthrough Attacks: Findings from the OASISplus Study
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 163)
  • Presenting Author: Marc Riedl
• Real-world Adherence and Persistence with Long-term Prophylaxis among Patients with Hereditary Angioedema
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 043)
  • Presenting Author: William Lumry
• Safety and Efficacy of Donidalorsen in Adolescent Patients With Hereditary Angioedema: 1-Year Results From OASISplus
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 059)
  • Presenting Author: H. James Wedner
• Patient-Reported Disease Control, Work Productivity, and Activity Impairment in Hereditary Angioedema: Insights from OASIS-HAE
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 149)
  • Presenting Author: Juan Carlos Cardet
• The Relationship Between Objective Disease Control at Baseline and Change in Subjective Disease Control and Quality of Life in Patients with Hereditary Angioedema Receiving Donidalorsen
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 150)
  • Presenting Author: Alan P. Baptist
• Predictors of Disease Control, Attack Rate, and Quality of Life in HAE: An Exploratory Analysis
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 153)
  • Presenting Authors: Timothy Craig
• Unmet Treatment Need in a Real-World US Population of Patients with Hereditary Angioedema Treated for Over a Year with Long-Term Prophylaxis
  • Poster Presentation: February 27, 2026, 2:45-3:45 pm (Poster 152)
  • Presenting Author: Dawn Flick
• Rethinking Severity Assessment in Hereditary Angioedema: Insights from Patient Experiences
  • Poster Presentation: March 1, 2026, 9:45-10:45 am (Poster 722)
  • Presenting Author: Art Zbrozek

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 more than 20,000 people in the U.S. and Europe.

About DAWNZERA™ (donidalorsen)

DAWNZERA™ (donidalorsen) is approved in the U.S. and the EU 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.

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 Ionis Pharmaceuticals, Inc.

For three decades, Ionis has invented medicines that bring better futures to people with serious diseases. Ionis currently has marketed medicines and a leading pipeline in neurology, cardiometabolic disease and select 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.

Ionis Forward-looking Statements

This press release includes forward-looking statements regarding Ionis' business and the therapeutic and commercial potential of DAWNZERA, additional medicines in development and technologies. Any statement describing Ionis' goals, expectations, financial or other projections or guidance, 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 but not limited to those related to our commercial products and the medicines in our pipeline, and particularly 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 Dec. 31, 2025, and most recent Form 10-Q, which are on file with the SEC. Copies of these and other documents are available at www.Ionis.com.

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.

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