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BACKGROUND: The Natural History Study of the Safety, Effectiveness, and Practice of Treatment for People with Haemophilia (ATHN 7) monitors use of contemporary haemophilia therapies, including emicizumab, a bispecific antibody substituting for activated factor (F)VIII in people with haemophilia A (HA). AIM: To report participant characteristics and real-world safety and effectiveness of emicizumab in ATHN 7. METHODS: ATHN 7 is a prospective observational cohort study conducted across 26 American Thrombosis and Haemostasis Network (ATHN)-affiliated sites. People with HA receiving emicizumab were eligible for inclusion in this analysis. Clinical information was collected quarterly through participant interview and medical record review. Safety was evaluated by documenting adverse events (AEs); effectiveness was assessed by annualized bleeding rates (ABRs). RESULTS: At data cut-off (31st December 2023), 257 participants were receiving emicizumab; 63 (24.5%) had FVIII inhibitors at baseline; 84.4% had severe HA. In total, 109 (42.4%) participants were <12 years old. Median (range) emicizumab exposure duration was 116.4 (0.1-206.6) weeks. Overall, 40 AEs were reported in 13 (5.1%) participants; a total of 33 injection-site reactions were reported in 7 (2.7%) participants. No thromboses or thrombotic microangiopathy were reported. There was one fatality from haemorrhagic shock, deemed unrelated to emicizumab. Median (range) ABR for treated bleeds was 0.25 (0-8.18) for participants with FVIII inhibitors and 0.51 (0-16.25) for participants without FVIII inhibitors. CONCLUSION: In people with HA treated with emicizumab, no new safety signals were identified. ABRs were similar for participants with or without FVIII inhibitors, across different severities of HA. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03619863.
Buckner et al. (Tue,) studied this question.