The safety and efficacy of B-domain deleted recombinant factor VIII concentrate in patients with severe haemophilia A

Background: B-domain-deleted recombinant factor VIII (BDDrFVIII) was developed when the B-domain was found to be redundant for maintaining haemostasis. This allows formulation of the final product without albumin added as a stabilizer. Methods: Three multicentre clinical studies and one pharmacokinetic study were conducted in 218 patients to evaluate the safety and haemostatic efficacy of BDDrFVIII. Results: Previously treated patients (n = 113; median duration, 1711 days; median exposure days, 385; total 98 096 287 IU infused) rated 97-99% of all infusions as good or excellent efficacy. FVIII inhibitor was noted in one patient in the previously treated patient cohort after 113 exposure days. Among 101 previously untreated patients, responses to BDDrFVIII were rated as excellent or good in 92-95% of infusions (median duration, 1413 days; median exposure days, 148; total 12 636 458 IU infused). Thirty-two previously untreated patients developed inhibitors after a median duration of 12 exposure days (range, 3-49). Sixteen of 32 (50%) patients had low levels (less than or equal to 5 Bethesda units) and 16 had high levels of inhibitors. Inhibitors disappeared in six of 14 (43%) of the high-level and six of eight (75%) of the low-level patients who underwent immune tolerance induction therapy. A total of 42 patients underwent surgery and the overall efficacy of BDDrFVIII was rated as excellent or good for 99.6% of infusions. Conclusions: The results of these clinical studies indicate that BBDrFVIII is safe and effective and has haemostatic activity similar to that of full-length FVIII concentrates.