The study includes 2 distinct parts: Part 1 and Part 2. In Part 1, an ascending-dose design will be utilized to enable evaluation of increasing doses in a stepwise manner. The objective for this dose escalation is to identify the dose of BE-101 required to achieve desired FIX activity 28 days after infusion. Upon identification of a safe and efficacious dose in Part 1, an expansion phase (Part 2) will initiate. The initial cohort in the Part 2 expansion (Part 2a) phase will include up to 6 adult participants to further characterize the safety and activity of BE-101 at the selected dose. Additional cohorts for adolescents and redosing for participants in Part 1 of the study will occur following data availability of Part 1.
Up to 24 participants will be enrolled across Part 1 (up to 18) and Part 2a (up to 6). Consented participants will complete a screening period to assess eligibility and upon enrollment will undergo leukapheresis collection to support BE-101 manufacturing. Following administration, participants will be monitored for safety and clinical activity. The total duration of study participation is approximately 52 weeks post IV administration of BE-101.
