PROCESS FOR PURIFYING FACTOR VIII

Proteases generally tend to reduce the activity of coagulation factor VIII by degrading the molecule. The present invention relates to a process for reducing the detrimental influence of metal-dependent proteases upon recombinant factor VIII molecules, by adding an inhibitor of metal-dependent proteases to a solution after harvest. The solution is suitably the harvest solution or any aqueous solution being fed to or leaving the primary isolation, being the initial step of the purifying sequence. The inhibitor is selected from: i) complexing agents with a stronger affinity for the metal ion of the protease than for the ion or ions stabilizing the factor VIII molecule and ii) compounds structurally related to the natural substrate of the protease and containing an electronegative moiety. The presence of an inhibitor, preferably a complexing agent, after harvest allows for a prolonged harvest period and considerably higher yield with essentially retained factor VIII activity. The invention further relates to an aqueous solution containing recombinant factor VIII which has been purified according to the present process and use of such an aqueous solution, for the manufacture of a medicament for administration to a patient having the symptoms of hemophilia. Also, the invention relates to a method for treatment of hemophilia by administration of a therapeutically effective amount of recombinant factor VIII which has been purified according to the present process.