Summary
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 1 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.
Keywords
Pharmacokinetics - von Willebrand factor - von Willebrand disease - VWF - von Willebrand
disorder - VWD - coagulation factor concentrate