There are some issues in the current factor (F)VIII replacement therapy for severe hemophilia A. One is mental and physical burden for the multiple intravenous infusions, and the other is difficulty in the hemostatic treatment for the patients with FVIII inhibitor. The development of novel drug with fully hemostatic effect, simply procedure, and long-acting reaction has been expected. Recently, FVIIIa-mimicking humanized recombinant bispecific antibody (ACE910) against FIXa and FX was developed. In the non-human clinical study, primate model of acquired hemophilia A demonstrated that the ACE910 was effective on both on-going and spontaneous bleedings. A phase I clinical study was conducted in healthy adults by single subcutaneous infusion of ACE910, followed by the patients' part study, Japanese patients with severe hemophilia A without or with inhibitor were treated with once-weekly subcutaneous injection of ACE910 at three dose levels for 12 successive weeks. There was no significant adverse event related to ACE910 in the clinical and laboratorial findings, and t1/2 of ACE910 was ∼30 days. The median annual bleeding rates were reduced very markedly dose-dependently, independently of inhibitor. Furthermore, among the patients with dose escalation, bleeding rate was decreased as ACE910 dose was increased. In conclusion, ACE910 would have a number of promising features: its high subcutaneous bioavailability and long half-life make the patients possible to be injected subcutaneously with a once-a-week or less frequency. In addition, ACE910 would provide the bleeding prophylactic efficacy, independently of inhibitor.
Keywords: Hemophilia; bispecific antibody; clinical study; factor IX; factor VIII; factor X.
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