Participant efficacy data and liver function tests. (A) Annualized FVIII infusion rate (infusions/yr). (B) ABR (treated bleeds/yr). (C) Liver function test results for P1. (D) Liver function test results for P2. (E) FVIII measured by 1-stage assay (IU/dL). (F) FVIII measured by chromogenic assay (IU/dL). (G) Liver function test results for P3. ∗The postprophylaxis period began either at the start of week 5 or 3 days after the end of FVIII prophylaxis (whichever was later) and ended at the data cutoff date. P1 and P2 were enrolled in 301 and received 6×10¹³ vg/kg valoctocogene roxaparvovec. P3 was enrolled in 302 and received 4×10¹² vg/kg valoctocogene roxaparvovec. In Figure 1C, 1D, and 1G, open symbols denote values above the ULN, and all depicted measurements were from a central laboratory. In Figure 1D, the light blue stepwise box below the X-axis denotes prednisone use in P2, and the light blue arrow located in the insert denotes when prednisone was started in P2. In Figure 1G, local laboratory measurements of liver function tests were also performed to support participant monitoring; these demonstrated ALT levels worsened again after resuming efavirenz by day 63. Bleeds and any FVIII treatment that was administered were self-reported by participants. Treated bleeds were defined as bleeds followed by use of standard half-life, extended half-life, or plasma-derived FVIII products within 72 hours. Bleeds associated with surgery or procedures were excluded from the analysis. ABR was defined as number of bleeding episodes/total number of days x 365.25. Annualized FVIII utilization rate was defined as number of FVIII infusions/total number of days x 365.25. The black arrow in Figures 1E and 1F denotes when P3 resumed FVIII prophylaxis and measurements of FVIII activity beyond this time were excluded. Values for FVIII activity detected below the lower limit of quantification (1 IU/dL for OSA, 3 IU/dL for CSA) were reported as 0 IU/dL and any measurements of FVIII activity were excluded if obtained within 72 hours of an infusion of exogenous FVIII. ABR, annualized bleeding rate; ALP, alkaline phosphatase; ALT, alanine aminotransferase; AST, aspartate aminotransferase; CSA, chromogenic assay; FVIII, factor VIII; GGT, gamma-glutamyl transferase; HAART, highly active antiretroviral therapy; LDH, lactate dehydrogenase; OSA, one-stage assay; P, participant; ULN, upper limit of normal; vg, vector genomes; yr, year.