Pharmacokinetic, efficacy and safety evaluation of B‐domain‐deleted recombinant FVIII (SCT800) for prophylactic treatment in adolescent and adult patients with severe haemophilia A

Abstract Introduction SCT800 is a recombinant human B‐domain‐deleted coagulation factor VIII (BDDrFVIII) developed in China. Aim To evaluate the repeat pharmacokinetics (PKs), efficacy, and safety of SCT800 in previously treated Chinese adolescent and adult patients with severe haemophilia A. Methods A phase III, multicentre, prospective, open‐label, single‐arm trial was conducted at 12 medical centres. Subjects received treatment for 24 weeks. PKs were assessed at the initial and repeated dosing 24 weeks later. The primary endpoint was annualized bleeding rate (ABR). Breakthrough bleeding episodes and inhibitor development were assessed. Results A total of 71 of 73 patients completed the study, and 18 were enrolled for the repeat PK investigation. Total exposure was 5643 exposure days. Overall, SCT800 showed comparable repeat PK profiles. The total ABR was 2.82 (95% confidence interval 2.01‐3.96). During prophylaxis, 43.8% of patients had no bleeding episodes. The majority (89.4%) of bleeding episodes were controlled with 1–2 injections of SCT800, the success rate (defined as ‘excellent’ or ‘good’ haemostatic response) for the treatment of bleeding episodes was 92.6%. The incidence of treatment‐related adverse events was 53.4%. Drug‐related AE incidence was 4.1%. The observed AEs were similar to those of other coagulation factor VIII, but lower in frequency. No subject developed an inhibitor, and no other safety concerns were identified. Conclusions SCT800 has robust PK characteristics, and is safe and efficacious for the prophylaxis and treatment of bleeding episodes in previously treated adolescent and adult patients with severe haemophilia A.