The present invention relates to a proteinaceous construct comprising a bloodcoagulation factor, e.g., Factor VIII(FVIII), being bound to at least one water soluble polymer, including apoly(alkylene oxide) such as polyethylene glycol (PEG).Further the present invention relates to methods of preparing PEGylated bloodcoagulation factor, e.g., FVIII, in the presence ofbound antibodies. The invention also relates to methods for prolonging the invivo-half-life of blood coagulation factor, e.g.,FVI-II, in the blood of a mammal having a bleeding disorder associated withfunctional defects or deficiencies of blood coagulationfactor, e.g., FVIII.
