Comparison of the pharmacokinetics of two von Willebrand factor concentrates [Biostate and AHF (High Purity)] in people with von Willebrand disorder

Plasma-derived factor concentrates are important in the management of von Willebrand disorder (VWD). In our geographic locality, a single viral inactivation step concentrate (AHF [High Purity]), has been replaced with one using a double viral inactivation step (Biostate®). The aim of this study was to compare the pharmacokinetics of von Willebrand factor (VWF) and factor VIII (FVIII) after administration of AHF (High Purity) and Biostate®. This study was a single-blind, randomised cross-over, multi-centre investigation in twelve people with VWD, comprising four type 3, two type 2B, one type 2M and five type I VWD.The subjects received a single infusion of 60 IU/kg ristocetin cofactor activity (VWF:RCo) of either AHF (High Purity) or Biostate®, and after a minimum 15-day wash-out period they received the alternative product. Blood samples were collected for up to 48 hours after each dose for assay of FVIII coagulant activity (FVIII:C) and VWF by VWF:RCo, collagen binding capacity (VWF:CB) and antigen (VWF:Ag).As a measure of delivered VWF 'functionality' we calculated the area-under-the-concentration-time-curve (AUC) ratios of VWF:RCo to VWF:Ag and VWF:CB to VWF:Ag. The effect on platelet adhesiveness by PFA-100 closure times (CTs) was measured prior to and 30 minutes post infusion. VWF multimers were also assessed pre and post infusion. Pharmacokinetic parameters after AHF (High Purity) and Biostate® were in close agreement for VWF:RCo (confirming dosing equivalence). Parameters for other study markers were also similar, although Biostate® tended to yield relatively lower VWF:Ag and higher VWF:CB levels. Although AHF (High Purity) and Biostate® resulted in similar levels of high-molecular-weight (HMW) multimers post-infusion, the relative level of HMW to low-molecular-weight (LMW) multimers were determined to be higher following Biostate®. The relative levels of functional VWF (i.e.VWF:CB and VWF:RCo) to VWF:Ag were also higher in Biostate® compared to AHF (High Purity). With both study products, PFA-100 CTs 30 minutes post infusion showed minor improvement for only some subjects. In conclusion, the pharmacokinetics of FVIII:C and VWF are not significantly different after administration of AHF (High Purity) and Biostate®. Study parameters considered as 'in-vitro' markers of VWF 'functionality' or potential clinical efficacy (i.e.VWF:CB and VWF:RCo relative to VWF:Ag, level of HMW VWF relative to LMW-VWF) were determined to be higher for Biostate® than AHF (High Purity). PFA-100 CTs did not adequately reflect changes in these VWF parameters. Based on these results, one would expect Biostate® to be at least as effective, if not superior to AHF (High Purity) for the treatment of VWD.