Bleed Treatment Outcomes from the XTEND-ed Study in Patients Aged 50 Years and Older

Introduction Older adults with haemophilia A face complex medical challenges due to aging that are compounded by limited factor therapy data in this population. Efanesoctocog alfa is a first-in-class high sustained factor VIII replacement therapy designed to decouple recombinant factor VIII from endogenous von Willebrand factor. In XTEND-1 (NCT04161495), once-weekly efanesoctocog alfa provided superior bleed prevention over prior FVIII prophylaxis and was well tolerated in adults/adolescents with severe haemophilia A. Patients completing XTEND-1 could enter Arm A of the extension study, XTEND-ed (NCT04644575); we assessed outcomes of patients aged≥50 years. Method Post-hoc analysis of data from patients aged≥50 years through the second interim analysis of XTEND-ed (datacut: February 22, 2024). Patients received once weekly efanesoctocog alfa (50 IU/kg). Endpoints included bleed treatment, factor consumption, annualised bleeding rates (ABRs), and safety outcomes. Results At enrolment of XTEND-ed, 32 patients (1 female) were aged≥50 years: mean age (SD; range), 58.5 (6.6; 50.0–74.0) years. Median (range) efficacy and treatment duration in XTEND-ed were 115.4 (31.3–136.6) and 120.1 (31.3–136.6) weeks, respectively. Median (range) exposure was 121.5 (30.0–146.0) days; median (range) injections/patient was 121.5 (30.0–146.0); median (range) weekly dose was 51.1 (47.2–53.2) IU/kg. Mean (95% CI) model-based ABRs during the efficacy period were: overall, 0.92 (0.54, 1.55); spontaneous, 0.38 (0.19, 0.75); traumatic, 0.29 (0.15, 0.54). Bleeding episodes (BEs) data by year are reported in the [ Fig. 1 ]. Median (range) injections for resolution of BEs were 1 (1–2). Treatment-emergent adverse events were reported in 26/32 (81.3%) participants during the efficacy period; one treatment-related ([ Fig. 1 ]). No inhibitor development occurred. Conclusion Prophylaxis treatment with once weekly efanesoctocog alfa (50 IU/kg) continued to provide highly effective bleed protection in patients aged≥50 years. Study funded by Sanofi and Sobi. Acknowledgments: Medical writing support for the development of this abstract was provided by Helen Jones, PhD, of Envision Pharma Group and funded by Sanofi and Sobi. The authors thank Emily Ly, PharmD (Sanofi) and Nick Fulcher, PhD, CMPP (Sobi) for publication coordination, and Erin Fang (Sanofi) for biostatistical support. Sanofi and Sobi personnel reviewed this abstract. The authors had full editorial control of the abstract and provided their final approval of all content. Fig. 1