Immune tolerance induction using a factor VIII/von Willebrand factor concentrate (BIOSTATE), with or without immunosuppression, in Australian paediatric severe haemophilia A patients with high titre inhibitors: a multicentre, retrospective study.

INTRODUCTION: It has been postulated that factor VIII (FVIII) products containing von Willebrand factor (VWF) may improve immune tolerance induction (ITI) success rate in patients with haemophilia A and poor prognostic factors. MATERIALS AND METHODS: We conducted a retrospective cohort analysis of a FVIII/VWF concentrate (BIOSTATE) for ITI in paediatric patients with severe haemophilia A (SHA) and inhibitors, from January 2003 to December 2011 at 3 paediatric-only Haemophilia Treatment Centres in Australia. Response to ITI was assessed at or before 33 months and at completion of ITI. Fifteen male patients with SHA were included in the analysis. RESULTS: BIOSTATE was used for primary ITI in 8 patients (2 years, range 1.1-11.5 years) and for salvage ITI in 7 patients (9.9 years, range 1.1-15.4). At the end of the observation period there were 11 patients who achieved a complete response with BIOSTATE after a median duration of 21 months (range 5-85 months); a partial response was achieved in 2 patients in whom ITI is ongoing. Therefore, the overall response rate was 86.6%. Two patients were deemed treatment failures: one due to non-compliance after 18 months of ITI and another in whom a partial response had not been achieved after 22 months of ITI. CONCLUSION: BIOSTATE was well-tolerated and effective when used for primary or salvage ITI in this cohort of paediatric patients with SHA and a high-level inhibitor.

Comparison of the pharmacokinetics of two von Willebrand factor concentrates [Biostate and AHF (High Purity)] in people with von Willebrand disorder. A randomised cross-over, multi-centre study.

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.