Thrombotic rates in individuals with inherited bleeding disorders treated with concentrate or bispecific antibody. Fifteen-year EUHASS data.

Abstract

Background: Although inherited bleeding disorders are associated with a reduced risk of thrombosis, the rate of thrombosis following treatment of the bleeding disorders is unknown.

Objective: To determine the rates of thrombosis in persons with inherited bleeding disorders treated with clotting factor concentrates or a bispecific antibody.

Methods: Analysis of the thrombotic events reported to the EUHASS system. EUHASS is the European surveillance system for adverse events in persons with all inherited bleeding disorders treated with clotting factor concentrates and/or emicizumab. 95 sentinel centres from 27 countries participated. From 10/2008 to 12/2023, thrombotic events occurring within 30 days of product administration, and the number of persons treated with each product were reported. Annual thrombosis rates (95% confidence intervals-CI) according to the product were compared using rate ratios.

Results: During the 15-year period, 204 episodes of thrombosis occurred in 209,842 treatment years 113 events were in hemophilia A, 22 in hemophilia B, 22 in von Willebrand disease, and 47 in other bleeding disorders. The rates of thrombosis following plasma-derived FVIII was 1.10, recombinant standard half-life FVIII 0.70 and extended half-life FVIII 0.52 per 1000 patient years. The rate for emicizumab (Hemlibra) was 0.92 per 1000 patient years. The highest rate was in persons treated with fibrinogen concentrate at 11.56 per 1000 patient years.

Conclusion: The rate of thrombosis in persons with hemophilia A and B treated with FVIII and IX concentrates, respectively, is less than 1.0 per 1000 patient years. This information can be used in comparisons with rates for newly introduced products.