Lasker Award Honors Developers of Hemophilia A Antibody

The 2026 Lasker-DeBakey Clinical Medical Research Award was presented to Kunihiro Hattori, PhD, Takehisa Kitazawa, PhD, DVM, and Tomoyuki Igawa, PhD, for developing a bispecific antibody that mimics coagulation factor VIII, according to a Perspective published in JAMA.

Hemophilia A is an X-linked recessive bleeding disorder caused by factor VIII deficiency or dysfunction. Conventional factor VIII replacement enables hemostasis and bleeding prophylaxis, but its 0.5-day half-life and poor subcutaneous bioavailability require frequent intravenous home injections. About one-third of people with hemophilia A develop neutralizing factor VIII inhibitors that render replacement ineffective.

In 2000, Hattori conceived a bispecific immunoglobulin G (IgG) that would bind activated factor IX and factor X to reproduce part of factor VIII’s cofactor function. Early screening generated 460 bispecific IgGs. The first clinical candidate later lacked clear in vivo hemostatic activity and caused bleeding in nonhemophilic animals because strong binding interfered with factor VIII–driven coagulation.

The team restarted discovery using approximately 200 antibodies to activated factor IX and 200 to factor X, generating about 40,000 bispecific IgGs. Only BS15 marginally passed screening. Across iterative design and testing, approximately 2400 variants were evaluated before ACE910, later named emicizumab, was selected as the most balanced molecule.

The Perspective reported that subcutaneous emicizumab substantially reduced bleeding in people with hemophilia A with or without factor VIII inhibitors and enabled maintenance dosing from weekly to once every 4 weeks. It also identified denecimig (Mim8) as another factor VIII-mimetic bispecific IgG and zemocimig (NXT007) as a next-generation molecule in clinical development. All three authors disclosed Chugai-related patents and minority shareholdings; Kitazawa and Igawa reported current Chugai employment, while Hattori reported former employment.

Source: Hattori K, Kitazawa T, Igawa T. From biological insight to a new class of medicines for hemophilia A: the 2026 Lasker-DeBakey Clinical Medical Research Award. JAMA. Published online September 9, 2026. doi:10.1001/jama.2026.15612