Blood loss was lower after tail clip in a mouse model of hemophilia following prophylaxis with emicizumab plus tranexamic acid, according to a new study that was published in the journal Haemophilia. 

Compared to treatment only with emicizumab, the addition of tranexamic acid to the prophylaxis significantly reduced joint bleeding.

The fibrin fiber diameters of the animals treated with emicizumab plus tranexamic acid were smaller than that of mice treated with emicizumab only. Fibrin fibers are generally thicker in the plasma of hemophilia patients compared to people without the disease.

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This finding suggested that tranexamic acid in combination with emicizumab, when used prophylactically, may benefit patients with hemophilia, especially those who experience breakthrough bleeds. 

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Emicizumab is a humanized bispecific antibody that mimics the activity of activated factor VIII, which is deficient in people with hemophilia A. Even though prophylaxis with emicizumab can dramatically reduce the bleeding rate in patients with the disease, breakthrough bleeds may still occur.

To test whether the addition of tranexamic acid to emicizumab can improve hemostasis, a team of researchers led by Yesim Dargaud MD, PhD, treated factor VIII-knockout mice with either emicizumab alone or emicizumab plus tranexamic acid before trauma (tail clip of knee).

The researchers compared the hemostatic efficacy of the 2 prophylactic approaches using MRI and histological analyses. They also measured the generation of thrombin and analyzed the obtained clots using scanning electron microscopy.

The authors note that this is a preclinical study in an animal model, results of which cannot currently be used in the clinic. The safety and efficacy of the combined prophylaxis must first be confirmed in clinical trials. Only then may it be possible to hypothesize that adding tranexamic acid to emicizumab prophylaxis may improve hemostasis in patients with the disease.


Janbain M, Enjolras N, Bolbos R, Brevet M, Bordet JC, Dargaud Y. Haemostatic effect of adding tranexamic acid to emicizumab prophylaxis in severe haemophilia A: a preclinical study. Haemophilia. Published online October 13, 2021. doi:10.1111/hae.14435