OBJECTIVES: The aim of this extension study was to investigate the long-term safety and efficacy of rVIII-SingleChain prophylaxis in ≥200 previously treated patients (PTPs) with hemophilia A with ≥100 exposure days (EDs).

METHODS: In total, 222 patients were enrolled, of which 204 rolled over from prior rVIII-SingleChain studies. The median age was 21 years (range, 2-65 years), including 155 patients ≥12 years and 67 patients <12 years. Patients continued with their previously assigned dose and regimen, or switched at the investigator's discretion. Patients were treated for a mean duration of 31 months (range, 1-47 months), the mean ED was 342 (standard deviation, 135.5), and 212 (95.5%) patients achieved >100 EDs. When the study ended, most patients were on either a prophylaxis regimen of 34.9 (17-62) IU/kg, 3×/week (N = 88; 39.6%), or 37.2 (13-65) IU/kg, 2×/week regimen (N = 72; 32.4%).

RESULTS: Hemostatic efficacy was rated excellent or good in 87.1% of assessed bleeds. The median (range) annualized bleeding rate was 1.21 (0.0-42.6), and the annualized spontaneous bleeding rate (AsBR) was 0.32 (0.0-33.0) for prophylaxis regimens. Median AsBR was similar for patients treated 3×/week and 2×/week (0.31 and 0.30, respectively). Surgical hemostatic efficacy was rated excellent or good in 100% of surgeries. No inhibitors, anaphylactic reactions, or thromboembolic events were reported in PTPs.