Modification of site-directed FVIII

A conjugate having procoagulant activity of factor VIII comprising a VIII polypeptide functional factor that is mutated so that at least one other non-cysteine ​​has been replaced with a cysteine ​​residue such that there is a rest of mutant cysteine, wherein the VIII functional polypeptide factor is covalently attached to a biocompatible polymer in the other mutant cysteine, wherein the biocompatible polymer is covalently attached to the polypeptide at one of the factor VIII amino acid of the 81, 129, 377, 378, 468 positions, 487, 491, 504, 556, 570, 1648, 1795, 1796, 1803, 1804, 1808, 1810, 1812, 1813, 1815, 1864, 1911, 2091, 2118 and 2284.