Sanofi announced that Pivotal study data published in The New England Journal of Medicine (NEJM) continues to highlight the efficacy, safety, and pharmacokinetic profile of efanesoctocog alfa, an investigational treatment for hemophilia A. These data demonstrate that efanesoctocog alfa delivered normal to near-normal factor activity levels (>40%) for the majority of the week with once-weekly dosing. Efanesoctocog alfa is currently under priority review by the United States Food and Drug Administration (FDA) and the target action date for the decision is February 28, 2023. Hemophilia A is a rare, lifelong condition in which the ability of a person's blood to clot properly is impaired, leading to excessive bleeds that can result in joint damage and chronic pain, and potentially impact their quality of life.

The severity of hemophilia is determined by the level of clotting factor activity in a person's blood. The data from the pivotal XTEND-1 Phase 3 study published in NEJM show that efanesoctocog alfa met primary and key secondary endpoints, demonstrating clinically meaningful prevention of bleeds and superior bleed protection compared to prior factor VIII prophylaxis based on an intra-patient comparison. Treatment with efanesoctocog alfa prophylaxis resulted in significant and clinically meaningful improvements in physical health, pain, and joint health.

Key results include: The median and mean annualized bleeding rates (ABR) were 0.00 (IQR: 0.00-1.04) and 0.71 (95% CI: 0.52-0.97), respectively; A statistically significant and clinically meaningful reduction in ABR (77%) versus prior factor VIII prophylaxis (p<0.001); Nearly all (97%) bleeding episodes resolved with a single injection of efanesoctocog alfa (50 IU/kg); Efanesoctocog alfa provided mean factor activity >40 IU/dL for the majority of the week and at 15 IU/dL at Day 7; Efanesoctocog alfa prophylaxis improved physical health (p<0.001), pain intensity (p=0.03), and joint health (p=0.01) when comparing 52 week and baseline measurements; In patients with target joints at baseline, 100% of the target joints were resolved after at least 12 months of continuous prophylaxis; Efanesoctocog alfa was well-tolerated, and inhibitor development to factor VIII was not detected. The most common treatment-emergent adverse events (>5% of participants overall) were headache, arthralgia, fall, and back pain. Quality of life data from the XTEND-1 study were recently presented at the 64th American Society of Hematology (ASH) Annual Meeting & Exposition.

The findings provided further evidence of the potential positive impact of once-weekly efanesoctocog alfa prophylaxis to provide normal to near-normal factor activity levels for the majority of the week, reduce pain, and improve physical functioning for people with hemophilia A.