Factor VIII recovery after a single infusion of recalibrated ReFacto in 14 severe haemophilia A patients.

Summary.  A recent multicentre collaborative study showed higher estimates of ReFacto® potency when assayed with ReFacto Laboratory StandardTM (RLS) in comparison when standards consisting of full-length factor VIII (FVIII) were used. The RLS was hence recalibrated, leading to a 20% increase in the amount of ReFacto® per vial without change in the labelled potency. The primary objective of this study was to determine the incremental and in vivo recovery of the recalibrated ReFacto® in patients with severe haemophilia A. Fourteen male severe haemophilia A patients (FVIII  150 were administered an intravenous infusion 50 ± 5 IU kg−1 of ReFacto® over a 5-min period. Blood samples were collected before infusion and after 15, 30 and 60 min. FVIII clotting activity (FVIII:C) was assessed in a central laboratory by the chromogenic substrate assay. After ReFacto® infusion, peak FVIII:C was obtained within 15 min for 10 patients and within 30 min for the remaining four. Mean FVIII:C at peak was 117.7 ± 17.3 IU dL−1. Mean incremental recovery was 2.22 ± 0.27 IU dL−1 per IU kg−1 while mean in vivo recovery was 105.9 ± 14.6%. One patient reported three mild adverse events rated as ‘unrelated’ to the study drug. FVIII recovery after recalibrated ReFacto® infusion falls within the expected range and is similar to the values reported for other FVIII concentrates.