Late-breaking efanesoctocog alfa data presented at ISTH demonstrates highly effective bleed protection in children with severe haemophilia A with once-weekly dosing – SOBI + Sanofi

Pivotal data from the Phase III XTEND-Kids study evaluating efanesoctocog alfa [Antihemophilic Factor (Recombinant), Fc-VWF-XTEN Fusion Protein] once-weekly prophylaxis in previously treated patients younger than 12 years of age with severe haemophilia A were presented in a late-breaking session at the Annual Meeting of the International Society on Thrombosis and Haemostasis (ISTH) in Montreal, Canada.

The oral presentation detailed results from the XTEND-Kids study and confirmed that efanesoctocog alfa met the primary endpoint, occurrence of inhibitor development, and secondary endpoints including annualised bleeding rate (ABR). In the paediatric population, clearance of administered factor concentrates in the blood is greater than in adults, often requiring multiple injections per week using SHL or EHL factor VIII products. These data confirm that a once-weekly 50 IU/kg dose of efanesoctocog alfa provides highly effective bleed protection in both children and adults and can be used across all clinical scenarios.

“Haemophilia A is often diagnosed at a very young age. The requirement for haemophilia patients to be careful in their physical activities to prevent bleeding episodes and joint injuries is especially challenging for young children. They also need frequent infusions of prophylactic treatments. The results from XTEND-Kids demonstrate that efanesoctocog alfa offers highly effective bleed protection also for paediatric patients, with a once-weekly dosing. This is encouraging, as it highlights its potential to become a new standard of care for haemophilia A in patients of all age groups,” said Lydia Abad-Franch, MD, PhD, Head of Research & Development and Medical Affairs and Chief Medical Officer at Sobi.

Key Results : The Phase III XTEND-Kids study (NCT04759131) was an open-label, non-randomised interventional study of the safety, efficacy, and pharmacokinetics of once-weekly efanesoctocog alfa in previously treated patients younger than 12 years of age with severe haemophilia A. Patients (n=74) received once-weekly efanesoctocog alfa prophylaxis (50 IU/kg) for a mean duration of 51 weeks.• Development of Factor VIII inhibitors was not detected (0% [95% confidence interval (CI)] 0–4.9]). • Efanesoctocog alfa was well-tolerated and demonstrated a safety profile consistent with the XTEND-1 trial, confirming safety in both adults and children. • No serious allergic reactions, anaphylaxis, or embolic or thrombotic events were reported. No adverse events led to treatment discontinuation.• Median (interquartile range) and mean ABRs (95% CI) were 0.00 (0.00–1.02) and 0.89 (0.56–1.42), respectively. • 64% of patients had zero bleeding episodes, 82% of patients had zero joint bleeds and 88% of patients had zero spontaneous bleeds.• Pharmacokinetic results showed that weekly efanesoctocog alfa prophylaxis provided FVIII levels above 40% for approximately 3 days and above 10% at approximately day 7.

Haemophilia A is a rare, lifelong condition in which the ability of a person’s blood to clot properly is impaired, leading to excessive and spontaneous bleeds into joints that can result arthropathy and chronic pain, and potentially impact quality of life. The severity of haemophilia is determined by the level of clotting factor activity in a person’s blood, and there is a negative correlation between risk of bleeding and factor activity levels.

About XTEND-Kids :The XTEND-Kids study (NCT04759131) was an open-label, non-randomized interventional study of the safety, efficacy, and pharmacokinetics of once-weekly Altuviiio in previously treated patients younger than 12 years of age with severe hemophilia A. Patients received once-weekly Altuviiio prophyaxis (50 IU/kg) for 52 weeks which provided high-sustained FVIII levels throughout the weekly dosing interval with a median (IQR) annualized bleeding rate (ABR) of 0.00 (0.00, 1.02) and an estimated mean (95% CI) ABR of 0.89 (0.56 ; 1.42). The primary endpoint was the occurrence of inhibitor development (baseline to 52 weeks). No inhibitors were detected in this study.

About the XTEND Clinical Programs : The XTEND clinical program is comprised of two Phase III trials in hemophilia A: XTEND-1 in people 12 years or older and XTEND-Kids in children younger than 12 years old. There is also an ongoing extension study (XTEND-ed).