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

A recent multicentre collaborative study showed higher estimates of ReFacto^® potency when assayed with ReFacto Laboratory Standard^TM (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 < 1 IU dL⁻¹) with a cumulative previous exposure days to any FVIII product >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. [ABSTRACT FROM AUTHOR]