Donidalorsen Sustains 95% Attack Reduction in HAE
Two-year open-label data from Ionis Pharmaceuticals show lasting efficacy and no new safety signals for the hereditary angioedema treatment.
Updated on Nov. 13, 2026 in Allergies
Ionis Pharmaceuticals reported 2-year OASISplus data showing donidalorsen (Dawnzera) sustained a 95% overall reduction in hereditary angioedema attacks. Patients who switched to donidalorsen from lanadelumab, C1-esterase inhibitor, or berotralstat had a 71% lower attack rate than their baseline on prior prophylactic therapy.
Why it matters
Long-term durability data address a key question for patients who need ongoing prophylaxis for a rare, unpredictable condition. The company reported no new safety signals and no serious treatment-emergent adverse events related to the drug across the analyses.
The OASISplus extension reported a 95% overall attack reduction over 2 years in 83 patients, with 84% of the cohort remaining in the study. Because the study is open-label without a placebo arm and about one in six patients did not complete two years, the durability of these figures across all patients is not established.
The players
Ionis Pharmaceuticals
Ionis Pharmaceuticals is a Carlsbad, California-based biotechnology company that develops RNA-targeted medicines, including donidalorsen, for rare and serious diseases.
The details
Donidalorsen is an RNA-targeted medicine designed to target plasma prekallikrein, a protein involved in hereditary angioedema. In the switch cohort, patients previously treated with lanadelumab, C1-esterase inhibitor, or berotralstat moved to donidalorsen using a predefined protocol. In the first year, 27% of patients reported treatment-related adverse events, none serious, with injection-site reactions the most common.
Timeline
November 12, 2026: Ionis announced the 2-year OASISplus donidalorsen data.
November 12-16, 2026: Findings were slated for presentation at the ACAAI Annual Scientific Meeting in Phoenix, Arizona.
Health Landscape
The 2-year data extend the first-year results from the OASIS-HAE phase 3 trial, testing whether donidalorsen's attack reduction holds as patients remain on therapy. Long-term extension data of this kind are the evidence regulators and clinicians weigh when comparing prophylactic options for hereditary angioedema, a condition affecting an estimated 7,000 people in the United States.
For people with hereditary angioedema, these results suggest that a prophylactic therapy given every 4 or 8 weeks may keep attacks low over two years, though the data come from a company-sponsored open-label study. Patients considering a switch from another prophylactic should discuss the reported side-effect profile, including injection-site reactions, with their treating clinician.
The takeaway
Durable attack control over two years is the key question for long-term prophylaxis in a rare condition, and these open-label results point in a positive direction. Patients and clinicians should weigh them alongside the study's limitations, including the absence of a placebo arm.
Further reading
For more on immune-driven swelling conditions, see the Allergies section.
More information
Read the full Ionis press release on 2-year Dawnzera data from the company's investor relations site.
Source note: This article includes information reported by BioPharm International.
