• factor VIII;
  • haemophilia A;
  • inhibitors;
  • Octanate®;
  • previously untreated patients;
  • surgery

Summary.  For patients with haemophilia A (HA), lifelong replacement therapy with factor VIII (FVIII) concentrates is the treatment of choice. Octanate® is a plasma-derived, human, von Willebrand factor-stabilized FVIII product with demonstrated haemostatic efficacy in patients with HA. The aim of this ongoing study is to assess the immunogenicity of Octanate® in previously untreated patients (PUPs), monitoring for development of FVIII inhibitors. Interim data on 39 PUPs treated for bleeding, prophylactically and for surgical coverage are reported. Two of 39 subjects (5.1%) developed clinically relevant inhibitor titres over the course of the study. Another two displayed inhibitors that disappeared spontaneously without Octanate® dose change. All inhibitors developed under on-demand treatment and before exposure day (ED) 50. Remarkably, no inhibitor was observed in PUPs receiving prophylaxis with Octanate®. Of 39 subjects, 30 had exceeded 50 EDs at the time of this analysis. All inhibitor subjects were found to have large FVIII gene defects, either intron 22-inversions or large deletions. Octanate® was well-tolerated and the adverse event profile was consistent with the population studied. The haemostatic efficacy of Octanate® in prophylaxis and treatment of bleeding were generally rated as ‘excellent’, and no complication was reported for surgery. Notable FVIII activity was present in blood at 15 min postadministration, and levels remained high at 1 h. Mean incremental in vivo recovery (IVR) was 2.0 (±0.6) % IU−1kg−1. These interim results indicate Octanate® to be an efficacious, well-tolerated human FVIII product for management of HA in PUPs, associated with a minimal risk of inhibitors.