Hereditary angioedema (HAE) has been managed long term with injectable prophylactic therapies which may be burdensome for patients. Berotralstat, an oral once-daily prophylactic treatment for HAE, is an approved effective alternative to injectable therapies. Previously presented data demonstrated that patients who switched from injectable prophylactic therapy maintained consistently low monthly attack rates and reported markedly improved patient satisfaction as compared to their prior injectable prophylactic therapy. Here we report the attack-free status in patients who switched from lanadelumab to berotralstat monotherapy at US sites in the open-label international APeX-S study (NCT03472040).

In the US, all patients enrolled in APeX-S received open-label berotralstat 150mg once daily (QD). Safety (primary objective), effectiveness and quality of life (secondary objectives) were evaluated. For this analysis, we report attack-free time in subjects following a switch from lanadelumab to berotralstat monotherapy (1 month equals 28 days of therapy).

21 patients discontinued lanadelumab and switched to berotralstat 150mg monotherapy. Patients received berotralstat for a median of 336 days. Monthly attack rates were consistently low following the switch to berotralstat monotherapy. The mean (SEM) monthly attack rate after Month 1 was 0.1 (0.08), which was sustained through Month 6 (0.5 [0.24]) and Month 12 (0.2 [0.15]). Median attack rates were 0.0 attacks/month during each timepoint throughout 12 months of treatment. The percentage of attack-free days remained consistently high after patients switched to berotralstat. Overall, patients remained attack-free a total of 98% of days (5272/5393) during the 12 months of treatment with berotralstat monotherapy. The percentage of attack free-days during Months 1, 6, and 12 was 99%, 98%, and 100%, respectively.  While on berotralstat monotherapy, the duration of time between attacks was a mean (SEM) of 144 (23.7) days with a maximum duration of 411 days. The most common adverse events (occurring in ≥10% of patients) were vomiting and insomnia (each 14.3%).

In patients who switched from lanadelumab to oral berotralstat, HAE attack rates remained consistently low. In addition, patients remained attack-free an average of 98% of days during treatment, indicating that berotralstat is effective at maintaining good control of HAE symptoms.