Pharmacokinetic studies on Wilfactin®, a von Willebrand factor concentrate with a low factor VIII content treated with three virus-inactivation/removal methods

Objective: In order to correct the primary von Willebrand factor (VWF) defect and avoid supra-physiologic plasma levels of factor VIII, a pure VWF concentrate almost devoid of FVIII was developed and used in France since 1989. Methods: The pharmacokinetic (PK) profile of the most recent version of this concentrate (Wilfactin (R); LFB, Les Ulis, France), treated with three virus-inactivation/removal methods (solvent/detergent, 35 nm filtration, dry heat treatment), was investigated in 25 patients. Seventeen patients with various types of clinically severe von Willebrand disease (VWD) were included in a crossover, randomized trial carried out in five European centers and comparing Wilfactin (R) with concentrates containing both FVIII and VWF (FVIII/VWF). Eight type 3 VWD patients were included in another trial carried out in six French centers comparing Wilfactin (R) with its previous version (Facteur Willebrand-LFB (R); LFB) that adopted one virus-inactivation method only. Results: For both the measurements evaluated in this study (VWF antigen, VWF:Ag; and VWF ristocetin co-factor activity, VWF:RCo), Wilfactin (R) had a PK profile similar to that of the FVIII/VWF concentrates and of Facteur Willebrand-LFB (R). VWF:RCo and VWF:Ag recoveries were 2.1 +/- 0.3 and 1.8 +/- 0.3 per IU kg(-1) respectively, and the half-lives were 12.4 +/- 1.8 and 15.9 +/- 1.5 h. The FVIII synthesis rate was 5.8 +/- 1.0 IU dL(-1) h(-1), with a half-life of 15.8 +/- 2.4 h. Conclusion: The PK of VWF and FVIII have not been altered by the three virus-inactivation/removal steps during the manufacturing of Wilfactin (R).