Ionis Pharmaceuticals announced positive phase 2 data from their open-label extension (OLE) trial assessing the safety and efficacy of donidalorsen, a novel investigational antisense treatment for patients with hereditary angioedema (HAE).

The results were presented at the American College of Allergy, Asthma, and Immunology Annual Scientific Meeting in Louisville, Kentucky, on November 13, 2022.

“Today’s data further enhance donidalorsen’s profile and potential to provide significant sustained protection from attacks for people living with hereditary angioedema,” said Richard S. Geary, PhD, executive vice president and chief development officer at Ionis. “The positive results of the Phase 2 OLE are encouraging as we continue evaluating donidalorsen, a potential best-in-class medicine, in the ongoing OASIS Phase 3 program.”  

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HAE is a rare hereditary disease in which patients experience acute and painful attacks of inflammation in various parts of the body, including the face, hands and feet, limbs, larynx and trachea, and abdomen. Donidalorsen is designed to reduce prekallikrien production, which activates inflammatory mediators associated with these attacks.

Read more about HAE therapies

Twenty patients with type 1 or type 2 HAE completed the phase 2 study and were enrolled in the OLE extension study. Over a period of 13 weeks, they received 80 mg of donidalorsen subcutaneously every 4 weeks. Eight of the patients switched to 80 mg of the medication every 8 weeks. Those patients who received the therapy every 4 weeks had a 95.3% reduction in HAE attack rate from week 1 and a 98.3% reduction from week 5.

Those who received the treatment every 8 weeks had a 75.6% reduction from baseline in the rate of attacks and their mean attack rate per month was 0.28. Of these 8 patients, 5 remained free of attacks at 1 year and 3 resumed receiving donidalorsen every 4 weeks.

The company reported no serious adverse events, and no patient discontinued the study due to treatment-emergent adverse events.


Ionis presents positive phase 2 data from open label extension study of donidalorsen at 2022 ACAAI Annual Meeting. News release. Ionis Pharmaceuticals, Inc.; November 13, 2022.