This is a phase 3b open-label study providing access to berotralstat for HAE patients who were previously enrolled in berotralstat studies.

APeX-A, 7353-312, is a single-arm, open-label, multicenter study. The study will be conducted in countries where berotralstat is not available either commercially or via another mechanism and is planned in countries where pediatric participants have been enrolled in BCX7353-304 (Study 304). Adult and adolescent (≥12 years) participants will receive berotralstat 150 mg administered orally once daily (QD). Pediatric participants will receive a weight-appropriate dose. The study will assess the long term safety and tolerability of berotralstat.

Eligible subjects will be enrolled directly into Study BCX7353-312 (Study 312) from Studies 302, 204, and 304. Subjects will receive berotralstat administered orally once daily (QD). Subjects will return to the clinic every 24 weeks for drug dispensation and safety monitoring. Participants form Studies 302 and 204 may remain on study for up to 480 weeks (approximately 10 years). Participants from Study 304 may remain in the study until 16 years of age and have access to berotralstat via another mechanism; or up to 5 years, whichever comes first.

Safety and tolerability will be evaluated through assessment of serious adverse events (SAEs) and treatment-related, treatment-emergent adverse events (TEAEs). Up to 139 subjects are planned to enroll.

Key Inclusion Criteria:

• Males and females currently enrolled in BioCryst-sponsored Study 302, 204, or 304
• Participant or parent/legally designated representative (for participants <18 years of age) able to provide written informed consent.
• Would benefit from continued berotralstat treatment
• Acceptable effective contraception

Key Exclusion Criteria:

• Pregnancy or breast-feeding
• Any condition or situation, including medical history that, in the opinion of the investigator or sponsor, would interfere with the subject's safety or ability to participate in the study
• Use of other medications for long-term prophylaxis of HAE attacks at the Baseline visit or any time during the study.
• Use of any other investigational medicinal product at the Baseline visit or any time during the study.

No masking as this is open-label.