rVIII-SingleChain is a novel B-domain–truncated recombinant factor VIII, comprised of covalently bonded factor VIII (FVIII) heavy and light chains. This phase 1/3 open-label, nonrandomized multicenter pivotal study investigated the safety, efficacy and pharmacokinetics (PK) of rVIII-SingleChain in previously treated patients with severe hemophilia A. Study participants were males with severe hemophilia A (FVIII activity <1%), with >150 exposure days [EDs] to FVIII prior to enrollment, aged between 12 and 65 years. rVIII-SingleChain was administered 20 to 40 IU/kg every second day or 20 to 50 IU/kg, 2 to 3 times per week, or with other dosing regimens at the investigator’s discretion. Ten of the 174 subjects recruited were Japanese. In all subjects, the median annualized spontaneous bleeding rate (AsBR) of total prophylaxis therapy was 0.0 and the median annualized bleeding rate (ABR) was 1.14, whereas the median AsBR of on-demand therapy was 11.73 and the median ABR was 19.64. In Japanese subjects, the median AsBR of prophylaxis was 0.00, and the median ABR was 0.00, whereas the median AsBR of on-demand therapy was 3.55, the median ABR was 6.22. No patient developed an inhibitor, and no safety concerns were identified in the study.