Anti-AAV5 NAB threshold compatible with readministration. The efficacy of rAAV5-hFIX liver transduction at readministration was determined as a function of anti-AAV5 NAB titers. Post-rAAV5-hFIX readministration levels of hFIX protein at day 56 were plotted against the anti-AAV5 NAB IC50 levels just before the rAAV5-hFIX readministration. The data for 14 NHPs are reported in the graph; NHPs 1 to 6 (closed symbols) and NHPs 7 to 14 (open symbols). The vertical dotted line represents the threshold of efficacy determined at an IC50 of 8250. The horizontal area represents the minimal therapeutic range of 150 to 250 ng/mL corresponding to 3% to 5% of 5 mg/mL.