A phase 2 extension study has confirmed prior study results demonstrating a sustained 90% reduction in the rate of hereditary angioedema (HAE) attacks with donidalorsen treatment as well as a lower adverse event rate than placebo with the therapy.

The study was published in the Annals of Allergy, Asthma, & Immunology.

“Results of this study demonstrated sustained reduction in HAE attack rate and no new safety signals with donidalorsen treatment, confirming prior phase 2 study findings and supporting its continued development,” the authors wrote.

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HAE is a disorder caused by a deficiency of C1 inhibitor characterized by episodes of swelling in the face, limbs, intestines, or airway that can be severe or even life-threatening.

Read more about HAE therapies

The randomized, double-blind, placebo-controlled extension study enrolled 17 adult patients with HAE who had completed the phase 2 study. The study extension included a fixed treatment period in which patients were administered 80 mg of donidalorsen subcutaneously every 4 weeks for 13 weeks, followed by a flexible treatment period in which patients either continued taking 80 mg every 4 weeks or changed to 80 mg every 8 weeks or 100 mg every 4 weeks.

The primary outcome measure was the time-normalized number of HAE attacks per month over 17 weeks. Secondary outcome measures included investigator-confirmed HAE attacks, clinical response to the therapy, kininogen levels, prekallikrein activity levels, medication use, and quality of life.

No serious adverse events were reported and no patients discontinued the treatment due to adverse events. Most notably, the participants had no HAE attacks for 99.6% of the study days on treatment. The overall mean HAE attack rate during the study dropped from 2.7 per month to 0.08 per month, an almost 95% drop. The patients on 80 mg every 8 weeks had an HAE attack rate 76% lower than baseline.


Bordone L, Riedl M, Newman K et al. Phase 2 open-label extension study with donidalorsen treatment in patients with hereditary angioedema. Ann Allergy Asthma Immunol. Published online November 10, 2022. doi:10.1016/j.anai.2022.08.599