Previous studies investigating predictors of ABR identified that endogenous factor levels, adherence, BMI, primary dosing regimen, inhibitor development, presence of arthropathy, and intensity of physical activity as variables that can influence bleeding rates.1, 4, 26, 27, 28, 29, 30In the present analysis, the post-N8-GP 12-week prophylaxis model demonstrated that total bleed count up to 12 weeks postprophylaxis switch, baseline vWF level, and mean FVIII at 30 minutes postdose were the most important variables for predicting observed ABR with N8-GP prophylaxis. Here, F8 is linked to arthropathy.