D2.360 - Hereditary Angioedema Attack Rates among Patients with Normal C1 Esterase Inhibitor Before and After Switching from Another Long-Term Prophylaxis to Berotralstat

Patients with hereditary angioedema (HAE) with normal C1 esterase inhibitor (HAE-nC1INH) face recurrent, potentially life-threatening swelling attacks despite normal C1INH levels and function. Berotralstat is the only targeted, once-daily, oral long-term prophylaxis (LTP) that reduces the frequency and severity of HAE attacks. This real-world study compared HAE attack rates before and after initiation of berotralstat among patients with HAE-nC1INH who switched from a prior LTP.

Optime Care Specialty Pharmacy data (December 3, 2020 ─ September 10, 2025) were used to conduct this retrospective pre-post study. Optime Care, Inc. is the sole dispenser of berotralstat in the United States. Eligible patients had ≥2 berotralstat dispensings (first dispensing = index), normal C1INH based on laboratory measurements (C1INH levels, C1INH function, and C4 levels), ≥90 days of follow-up (spanning from first to last berotralstat dispensing), a self-assessment of attacks during baseline (90 days pre-index), and ≥1 self-assessment of attacks during follow-up. Included patients also reported previously using another LTP and discontinuing this medication within ±60 days of starting berotralstat. Monthly HAE attack rates were assessed during baseline and follow-up over fixed 90-day intervals among patients with follow-up through the end of a given 90-day interval and ≥1 self-assessment of attacks in the 90-day interval. Attack rates in each follow-up interval were compared with baseline using mean differences, 95% confidence intervals (CIs), and p-values from generalized estimating equations linear regression models with robust standard errors.

A total of 59 patients with HAE-nC1INH switched from another LTP to berotralstat; mean age was 43.0 years, 81.4% were female, and most switched from either lanadelumab (54.2%) or subcutaneous plasma-derived C1INH (23.7%). Mean baseline attack rates were 4.44, 4.53, and 4.92 attacks/month among patients with ≥12, ≥24, and ≥36 months of follow-up, respectively. Compared to baseline, attack rates decreased significantly (95% CIs) by -1.93 (-3.02, -0.85), -2.57 (-3.70, -1.45), and -3.21 (-4.63, -1.78) attacks/month at 12, 24, and 36 months of follow-up, respectively (all p<0.001) (Figure).

Significant and sustained reductions in HAE attacks were observed among patients with HAE-nC1INH who switched to berotralstat from another LTP.