Recombinant FVIII constructs. Amino acid numbering refers to mature, full-length human FVIII.39 The parent human B-domainless FVIII construct (HB⁻) lacks residues 741-1648. Porcine B-domain deficient FVIII (PSQ) contains a 14-residue sequence (SQ) corresponding to Ser741-Asn745, Pro1640-Arg1648 in human FVIII, instead of the B domain. Shaded regions correspond to areas of porcine substitution. In constructs HP23-HP28, these boundaries are defined by amino acid residues of human-porcine nonidentity at amino acid residues 2181, 2199, 2207, 2243, 2253, 2311, and 2321.