Key messages :
- Kunihiro Hattori, Takehisa Kitazawa and Tomoyuki Igawa, (Chugai Pharmaceutical), received the 2026 Lasker DeBakey Clinical Medical Research Award for restoring deficient Factor VII activity in hemophilia A, thus preventing the severe bleeding that characterises this genetic disorder.
- Haemophilia A is a genetic condition that results in a deficiency in the blood-clotting protein Factor 8, which prevents blood from clotting properly.
- Emicizumab is a bispecific antibody that performs the job of Factor 8 by binding Factor 9a and Factor 10 and bringing them together, restoring the disrupted clotting reaction chain.
- The therapeutic synthetic Factor 8, developed in the 1990s, required several injections a week into the bloodstream, and 30% of patients developed an immune response that blocked it. Emicizumab only requires a monthly injection under the skin.
- Emicizumab was approved in the US in 2017 and about 30,000 people worldwide have since received it. Fourteen other bispecific antibodies have been approved since, 11 of them for cancer.
Haemophilia A is a genetic condition that can cause a lifetime of uncontrollable bleeding. Three scientists, Kunihiro Hattori (formerly at Chugai Pharmaceutical), Takehisa Kitazawa (Chugai Pharmaceutical), and Tomoyuki Igawa (Chugai Pharmaceutical), have been awarded the 2026 Lasker DeBakey Clinical Medical Research Award for inventing an antibody that can prevent this severe bleeding. Working with rats, mice, rabbits and non-human primates, they found a way to restore the activity of a deficient blood-clotting factor.
When the clotting chain reaction stalls
Blood carries oxygen and nutrients around the body, removes waste and delivers infection-fighting cells. It serves vital functions, but blood vessels are fragile and can tear. To seal a damaged vein or artery, cell fragments called platelets gather at the break and provide a platform for clotting. Damage to a vessel triggers a set of proteins, called clotting factors, which activate each other until a clot forms.
One of these proteins, Factor 8, plays a crucial role. It grabs two other proteins, Factor 9a and Factor 10, and brings them together so that Factor 9a can activate Factor 10, which drives the process forward. In people with haemophilia A, Factor 8 is deficient. This halts the whole chain reaction and prevents blood from clotting properly.
Sufferers from haemophilia A are consequently at high risk of bleeding, which interferes with social and leisure activities, as well as school and work, with an effect on wellbeing, especially for children and their caregivers.
Bringing the factors together
In the 1990s, a synthetic version of Factor 8 was developed and dramatically benefited people with haemophilia A. But this therapy has limitations. It requires several injections a week directly into the bloodstream, and 30% of patients develop an immune response to the synthetic drug, which blocks its action.
Hattori, Igawa and Kitazawa developed an alternative approach that transformed treatment of the disease. In the 2000s, they imagined and designed a special antibody that could perform the job of Factor 8, while overcoming the main problems with existing treatments. Antibodies are proteins that recognise and attach to specific molecules, usually as part of the body’s response to disease or infection. The challenge was to make one that could both target and bring together Factors 9a and 10.
The scientists worked with mice, rats and rabbits to identify and refine promising candidates they had created until they found the most effective one, emicizumab (Hemlibra). This breakthrough held the promise of restoring the missing Factor 8 activity in haemophilia A patients, preventing the severe bleeding that characterises this genetic disorder.
From non-human primates to clinical trials
Before testing on human patients, emicizumab was tested in non-human primates called cynomolgus macaques, in which haemophilia A had been induced experimentally. The bispecific antibody – an antibody that binds two different targets – successfully prevented bleeding and protected the animals from internal bleeding and bruising. This result suggested that the therapy could stave off bleeds in people.
Clinical trials showed that an injection of emicizumab under the skin, given weekly or even monthly, could reduce bleeding in people with haemophilia A both dramatically and safely. The three scientists then devised solutions to allow production at industrial scale. Emicizumab was approved in the US in 2017, and more than 100 countries have followed.
The real-world impact has been profound, especially for children, who can take part more fully in normal play. Hattori, Igawa and Kitazawa have helped the 30,000 people worldwide who have received emicizumab. They have also widened the possibilities for therapeutic antibody design, opening the way to bispecific antibodies that target a range of disease processes. Since emicizumab, 14 additional bispecific antibodies have been approved, 11 of them targeting cancer.
FAQ :
What is haemophilia A?
Haemophilia A is a genetic condition that can cause a lifetime of uncontrollable bleeding. People with haemophilia A have a deficiency of Factor 8, a protein needed to form blood clots.
Why do people with haemophilia A bleed so severely?
Factor 8 normally brings together two other clotting proteins, Factor 9a and Factor 10, so that Factor 9a can activate Factor 10 and drive the clotting process forward. Factor 8 is deficient in haemophilia A patients so this chain reaction halts and blood cannot clot properly.
Who won the 2026 Lasker DeBakey Clinical Medical Research Award?
Kunihiro Hattori (formerly at Chugai Pharmaceutical), Takehisa Kitazawa and Tomoyuki Igawa (both at Chugai Pharmaceutical) received the award. They were recognised for restoring deficient Factor 8 activity in hemophilia A, thus preventing the severe bleeding that characterizes this genetic disorder
What is emicizumab (Hemlibra)?
Emicizumab, marketed as Hemlibra, is a bispecific antibody, meaning it binds two different targets. It performs the job of Factor 8 by attaching to Factor 9a and Factor 10 and bringing them together, which activates the downstream clotting activity.
How is emicizumab different from earlier treatments?
A synthetic version of Factor 8, developed in the 1990s, required several injections a week directly into the bloodstream. In 30% of patients it triggered an immune response that blocked its action. Emicizumab is given as a monthly injection under the skin.
Was emicizumab tested on animals?
Yes. The scientists worked with mice, rats and rabbits to identify and refine promising antibody candidates. Emicizumab was then tested in cynomolgus macaques, a non-human primate, in which haemophilia A had been induced experimentally. It prevented bleeding and protected the animals from internal bleeding and bruising.
Is emicizumab safe and effective in people?
Clinical trials showed that a weekly or even monthly injection under the skin could reduce bleeding in people with haemophilia A both dramatically and safely.
When was emicizumab approved, and how many people use it?
Emicizumab was approved in the US in 2017, and more than 100 countries have followed. About 30,000 people worldwide have received it.
What is the wider impact of this discovery?
The work has widened the possibilities for therapeutic antibody design. Since emicizumab arrived, 14 additional bispecific antibodies have been approved, 11 of them targeting cancer.
REFERENCES
Kitazawa T, Igawa T, Sampei Z, Muto A, Kojima T, Soeda T, Yoshihashi K, Okuyama-Nishida Y, Saito H, Tsunoda H, Suzuki T, Adachi H, Miyazaki T, Ishii S, Kamata-Sakurai M, Iida T, Harada A, Esaki K, Funaki M, Moriyama C, Tanaka E, Kikuchi Y, Wakabayashi T, Wada M, Goto M, Toyoda T, Ueyama A, Suzuki S, Haraya K, Tachibana T, Kawabe Y, Shima M, Yoshioka A, and Hattori K. (2012). A bispecific antibody to factors IXa and X restores factor VIII hemostatic activity in a hemophilia A model. Nat. Med. 18, 1570-1574.
Sampei Z, Igawa T, Soeda T, Okuyama-Nishida Y, Moriyama C, Wakabayashi T, Tanaka E, Muto A, Kojima T, Kitazawa T, Yoshihashi K, Harada A, Funaki M, Haraya K, Tachibana T, Suzuki S, Esaki K, Nabuchi Y, and Hattori K. (2013). Identification and multidimensional optimization of an asymmetric bispecific IgG antibody mimicking the function of factor VIII cofactor activity. PLoS One, 8:e57479. doi: 10.1371/journal.pone.0057479.
Muto A, Yoshihashi K, Takeda M, Kitazawa T, Soeda T, Igawa T, Sakamoto Y, Haraya K, Kawabe Y, Shima M, Yoshioka A, and Hattori K. (2014). Anti‐factor IXa/X bispecific antibody (ACE910): hemostatic potency against ongoing bleeds in a hemophilia A model and the possibility of routine supplementation. J. Thromb. Haemost. 12, 206-213.
Muto A, Yoshihashi K, Takeda M, Kitazawa T, Soeda T, Igawa T, Sampei Z, Kuramochi T, Sakamoto A, Haraya K, Adachi K, Kawabe Y, Nogami K, Shima M, and Hattori K. (2014). Anti-factor IXa/X bispecific antibody ACE910 prevents joint bleeds in a long-term primate model of acquired hemophilia A. Blood. 124, 3165-3171.
Kitazawa T, Esaki K, Tachibana T, Ishii S, Soeda T, Muto A, Kawabe Y, Igawa T, Tsunoda H, Nogami K, Shima M, and Hattori K. (2017). Factor VIIIa-mimetic cofactor activity of a bispecific antibody to factors IX/IXa and X/Xa, emicizumab, depends on its ability to bridge the antigens. Thromb. Haemost. 117, 1348-1357.
Shima M, Hanabusa H, Taki M, Matsushita T, Sato T, Fukutake K, Fukazawa N, Yoneyama K, Yoshida H, and Nogami K. (2016). Factor VIII-mimetic function of humanized bispecific antibody in hemophilia A. N. Engl. J. Med. 374, 2044-2053.
Last edited: 27 October 2026 08:43
