In vitro evaluation of a very-high-purity, solvent/detergent-treated, von Willebrand factor concentrate.

A very highly purified von Willebrand factor (vWF) concentrate was analyzed in order to evaluate its suitability for the treatment of von Willebrand's disease (vWD). The functional activity of vWF assessed by its ristocetin cofactor activity (vWF:RCo) correlated with the level of vWF antigen (vWF:Ag), with the vWF:RCo/vWF:Ag ratios ranging from 0.56 to 1.02, and the specific activity being always greater than 50 IU vWF:RCo/mg protein. Electrophoretic analysis showed a normal pattern of high, intermediate and low-molecular-weight multimers of vWF. The biological activity of vWF was also evaluated by studying its ability to bind to collagen and to platelet receptors in the presence of either ristocetin or thrombin. Furthermore, these functional activities of vWF were confirmed by the capacity of this concentrate to induce platelet adhesion to collagen in a perfusion system. Moreover, the vWF present in this preparation was able to bind factor VIII. All these in vitro data suggest that this preparation is likely to be effective in the treatment of vWD patients.