Effect of FX activation peptide and variants thereof on the half-life of FVII and FX. (A) Mean plasma concentration of FVII or FX antigen as a function of time after intravenous administration of 1 mg/kg FX, FVII_X, FXa_i, and FVII to mice. (B) Mean plasma concentration of FVII antigen as a function of time after intravenous administration of 1 mg/kg FVII_X and FVII_X_HC, (C) FVII_X, FVII_X_1-34 and FVII_X_30-52, and (D) FVII_X, FVII_X_NNAA, and FVII_X_TTAA to mice. Blood was sampled in a sparse schedule as each compound was administered to a total of 6 to 9 mice, and 3 samples were taken from each animal as described in “Pharmacokinetics.”