Peak FIX activity by participant, baseline CRM status, and dose cohort. FIX activity was measured in each participant during the 6 months after BAX 335 infusion. Participants, testing either positive or negative for circulating FIX antigen CRM at baseline, received a single infusion of BAX 335 at 1 of 3 doses. FIX measurements were determined by one-stage clotting assay (central laboratory), including measurements within 5 days of an exogenous FIX infusion and measurements from unscheduled study visits.