PB0258 - Emicizumab and females with hemophilia A in the ATHNdataset and prospective ATHN7 study

Background: Females with hemophilia A (HA) are under-represented in clinical trials, registries, and medical literature. However, they have unmet needs and can experience bleeding symptoms similar to males, making it essential to evaluate their characteristics and treatment experience.

Aims: To characterize the emicizumab-treated females with HA in the American Thrombosis and Hemostasis Network (ATHN)dataset and the ATHN 7 study (NCT03619863; supported in part by Genentech, Inc.).

Methods: The ATHNdataset contains health information for people with hemophilia in the US. Data are collected by hemophilia treatment centers and include demographics, diagnoses, and treatment. ATHN 7 is a longitudinal, prospective observational cohort study of people with hemophilia conducted at 26 ATHN-affiliated sites; demographics and medical history were documented at study entry, with data on treatment, bleeding, safety, and patient-reported outcomes collected at least quarterly. Ethics approval was obtained. Females with HA receiving emicizumab prophylaxis in the ATHNdataset or ATHN 7 were included in this analysis.

Results: As of October 31, 2023, the ATHNdataset included 30 emicizumab-treated females with congenital HA (Table 1). Of these, 15 (50.0%) had severe HA, 6 (20.0%) had moderate, and 8 (26.7%) had mild (severity unknown for 1 [3.3%]). The mean (standard deviation) annualized bleed rate was 0.6 (1.5).
As of August 31, 2023, three emicizumab-treated females with HA in the ATHNdataset were included in ATHN 7 (Table 2). Two had severe HA without factor (F)VIII inhibitors; one had moderate HA with inhibitors. One participant experienced a treated bleed (associated with a dental procedure) and an untreated bleed (menses) during the study. The other two participants experienced no bleeds. No adverse events were reported.

Conclusion(s): This is the largest dataset on emicizumab-treated females with HA reported to date, providing data on demographic and clinical characteristics, as well as the effectiveness of emicizumab, contributing greatly to the literature on this highly under-represented population.