The antibody response to wt fVIII, R372A/R1689A fVIII, or V634M fVIII in fVIII^−/−/VWF^−/− mice. FVIII^−/−/VWF^−/− mice were injected with 6 weekly doses of wt fVIII (n = 13), R372A/R1689A fVIII (n = 14), or V634M fVIII (n = 13) at 0.6 μg, followed by 2 weekly doses of 1.5 μg. One week after the last dose plasma was collected for both (A) anti-fVIII ELISA titers and (B) fVIII inhibitor titers. The differences in anti-fVIII antibody and fVIII inhibitor titers between wt fVIII and R372A/R1689A fVIII and V634M fVIII were not statistically significant.