mAb14C12 capacity to restore normal FVIII function in vivo in the presence of mAbBO2C11. C57BL/6 FVIII^-/- mice injected intravenously with 0.5 μg mAbBO2C11 and 1 IU FVIII show complete inhibition of FVIII activity. Injection of complexes made of mAbBO2C11 and various concentrations of mAb14C12 (A) or sequential administration of mAbBO2C11 followed by mAb14C12 (B) show a dose-dependent neutralization of the inhibitory activity of mAbBO2C11 with full FVIII functional activity as measured in a chromogenic assay. Bars show mean of 3 values ± SD. Under both experimental conditions, ± 50% restoration was obtained at an mAbBO2C11/mAb14C12 equimolar ratio. An unrelated IgG2a mAb had no effect.