Hereditary Angioedema Attacks in Patients Receiving Long-Term Prophylaxis: A Systematic Review

Long-term prophylaxis (LTP) has been shown to reduce the frequency of hereditary angioedema (HAE) attacks; however, attacks occurring in patients receiving LTP have not been well characterized. The objective of this systematic review was to evaluate the proportion of type I/II HAE (HAE-C1INH) patients who experience attacks while receiving LTP, the characteristics of these attacks, and associated on-demand therapy use. A systematic search was conducted in PubMed to identify studies reporting LTP use with plasma-derived C1 inhibitor (pdC1INH), lanadelumab, berotralstat, androgens, or antifibrinolytics in patients with HAE-C1INH. Forty-five primary studies met the inclusion criteria. In phase 3 trials, attack-free rates were 40% for subcutaneous pdC1INH 60 IU/kg twice weekly at 16 weeks, and 44% for lanadelumab 300 mg every second week at 6 months (77% during steady-state [days 70-182]); there was no difference in attack-free rate for berotralstat 150 mg versus placebo at 24 weeks. Phase 3 studies reported a lower average attack severity with subcutaneous and intravenous pdC1INH versus placebo. With lanadelumab and berotralstat, the prophylactic treatment effect was more pronounced in peripheral attacks than in abdominal and laryngeal attacks. Laryngeal attacks accounted for 2%-7% of all attacks in observational and interventional studies, regardless of the LTP agent received. On-demand therapy was used in 49%-94% of attacks occurring in the presence of LTP. In conclusion, patients receiving LTP experienced attacks in all anatomic locations, including the larynx. Most attacks were treated with on-demand therapy, although outcomes were not reported. Access to on-demand therapy remains essential for all people with HAE-C1INH.