Donidalorsen for hereditary angioedema: Long-term results from a 4-year, phase 2, open-label extension study

Hereditary angioedema (HAE) is a rare disorder caused by kallikrein-kinin system dysregulation. Donidalorsen is a prekallikrein-directed antisense oligonucleotide that can rebalance this system by reducing prekallikrein production and is indicated for prophylaxis to prevent HAE attacks in patients 12 years of age and older.

To report results from a 4-year, phase 2, open-label extension study of donidalorsen (NCT04307381).

The study on-treatment period included fixed (weeks 0-12) and flexible (weeks 16-208) treatment periods. Patients received donidalorsen 80 mg subcutaneously every 4 weeks (Q4W) in the fixed treatment period and could receive 80 mg every 8 weeks (Q8W) in the flexible treatment period if attack free for greater than or equal to 12 weeks or 100 mg Q4W if disease was not adequately controlled. End points are summarized through the end of the study (week 208).

Of 17 patients with HAE-C1INH-type 1 or HAE-C1INH-type 2, 13 (76%) completed 4 years of treatment (median exposure: 3.99 years). Eight patients changed to donidalorsen Q8W; 5 stayed on Q8W to study completion. One patient received 100 mg Q4W. Mean monthly HAE attack rates decreased by 97% overall from baseline to the on-treatment period, with 97% (Q4W) and 83% (Q8W) decreases to the flexible treatment period. The median longest attack-free interval was 990 days. No serious treatment-emergent adverse events (TEAEs) occurred. One patient (6%) (100 mg Q4W) discontinued due to a TEAE (injection-site discoloration). Seven patients (41%) reported treatment-related TEAEs; the only treatment-related TEAEs reported in more than 1 patient were injection-site reactions.

In this 4-year study, donidalorsen led to sustained reductions in monthly HAE attack rate with an acceptable safety profile.

ClinicalTrials.gov Identifier: NCT04307381 (https://www.

gov/study/NCT04307381).