Pharmacokinetics and safety of a novel recombinant human von Willebrand factor manufactured with a plasma-free method: a prospective clinical trial.

Safety and pharmacokinetics (PK) of recombinant von Willebrand factor (rVWF) combined at a fixed ratio with recombinant factor VIII (rFVIII) were investigated in 32 subjects with type 3 or severe type 1 von Willebrand disease (VWD) in a prospective phase 1, multicenter, randomized clinical trial. rVWF was well tolerated and no thrombotic events, inhibitors, or serious adverse events were observed. The PK of rVWF ristocetin cofactor activity, VWF antigen, and collagen-binding activity were similar to those of the comparator plasma-derived (pd) VWF-pdFVIII. In vivo cleavage of ultra-large molecular-weight rVWF multimers by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13; the endogenous VWF protease) and generation of characteristic satellite bands were demonstrated. In 2 subjects with specific nonneutralizing anti-VWF-binding antibodies already detectable before rVWF infusion, a reduction in VWF multimers and VWF activity was observed. Stabilization of endogenous FVIII was enhanced following post-rVWF-rFVIII infusion as shown by the difference in area under the plasma concentration curve compared with pdVWF-pdFVIII (AUC0-∞) (P < .01). These data support the concept of administering rVWF alone once a therapeutic level of endogenous FVIII is achieved.

First and next generation native rFVIII in the treatment of hemophilia A. What has been achieved? Can patients be switched safely?

The introduction of plasma-derived human factor VIII (FVIII) and later human recombinant FVIII (rFVIII) has potentially allowed patients suffering from hemophilia A to have a quality of life and life expectancy similar to the population at large. One of the major achievements in molecular biology over the past 15 years was the sequencing of the gene coding for FVIII, leading eventually to the ability to isolate the human gene for FVIII and transfect cells to produce human rFVIII. The first rFVIII products, which are native full-length FVIII molecules, have proved to have an excellent efficacy and safety profile in patients with hemophilia A. Initial concerns about a potential increased inhibitor formation have not been confirmed so far but long-term pharmacovigilance of inhibitor formation is still ongoing. To date, no transmission of hepatitis or human immunodeficiency virus (HIV) attributable to rFVIII products has been reported. However, a theoretical risk of transmission of infectious disease does exist as long as nonsynthetic proteins are used during the production process. The next-generation native rFVIII has been developed to minimize the exposure of patients to animal or human plasma-derived proteins. This has been achieved through major changes to the process of production of rFVIII from baby hamster kidney cells (BHK). This change has included the introduction of a solvent/detergent step and, of more importance, the introduction of a purification procedure without using albumin as a stabilizer. Finally, the rFVIII (BHK) is formulated using sucrose as the final stabilizer to produce the sucrose formulated rFVIII referred to as rFVIII-FS. This article summarizes the recently published pharmacokinetic, safety, and efficacy data for the native rFVIII-FS and compares its clinical profile with that of the first-generation rFVIII.