Overview of the phase 2b study design. After an initial screening period, during which time the participants received their usual standard of care or FIX replacement therapy, patients received a single IV dose of 2 × 1013 gc/kg etranacogene dezaparvovec. FIX levels were assessed weekly for the first 6 weeks, before assessments were reduced to biweekly until week 26 after infusion, when they reduced to monthly up to month 12, and twice-yearly up to the study completion of month 60. Quality-of-life assessments (Hem-A-QoL) were performed at week 26, and then annually from year 1 to year 5. Bleeding events, AEs, and any exogenous FIX use were reported throughout the study period. ∗Data from the year before screening were collected retrospectively using medical records. †Data were collected on the day of dosing. Tx, treatment.
