In vivo recovery of fVIII in the presence of saturating concentrations of anti-fVIII MAb. Blood was obtained by cardiac puncture 120 min after injection of rBDD fVIII to the indicated peak plasma concentrations in the presence of saturating plasma concentrations (65 nM) of the indicated MAb. fVIII recovery was determined by 1-stage coagulation assay (A) or fVIII antigen assay (B). Error bars represent SEM (each group n = 2 or 3).