Sanofi, Sobi announce results of XTEND-1 phase 3 study of efanesoctocog alfa

The study met the primary endpoint, showing a clinically meaningful prevention of bleeds in people with severe hemophilia A receiving weekly prophylaxis with efanesoctocog alfa over a period of 52 weeks. The median annualized bleeding rate (ABR) was 0 with a mean ABR of 0.71. The key secondary endpoint was also met, demonstrating once-weekly efanesoctocog alfa was superior to prior prophylactic factor VIII replacement therapy, showing a statistically significant reduction in ABR based on intra-patient comparison. 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.

Dietmar Berger, MD, PhD
Global Head of Development and Chief Medical Officer, Sanofi
"While advances have been made in the treatment of hemophilia, unmet medical needs still exist. These positive topline data, showing a very low annualized bleeding rate, enhance efanesoctocog alfa's potential to transform hemophilia A therapy. We believe efanesoctocog alfa provides higher protection for longer duration with reduced treatment burden of once-weekly dosing, and we look forward to working with regulators to bring this therapy to patients as soon as possible."

Hemophilia A is a rare, genetic disorder in which the ability of a person's blood to clot is impaired due to a lack of factor VIII. Hemophilia A occurs in about one in 5,000 male births annually, and more rarely in females. People with hemophilia can experience bleeding episodes that can cause pain, irreversible joint damage and life-threatening hemorrhages.

Anders Ullman, MD, PhD
Head of R&D and Chief Medical Officer, Sobi
"We believe once-weekly efanesoctocog alfa has the potential to represent a new class of factor VIII therapy designed to provide high sustained factor VIII levels near normal for the majority of the week. We look forward to sharing these Phase 3 results, including data on physical health, pain and joint health, at future medical meetings."

The data will be the basis for submission to regulatory authorities around the globe beginning this year. Submission in the EU will follow availability of data from the ongoing XTEND-Kids pediatric study, expected in 2023. Efanesoctocog alfa was granted Orphan Drug Designation by the US Food and Drug Administration (FDA) in August 2017 and the European Commission in June 2019. The US FDA granted Fast Track Designation in February 2021. Efanesoctocog alfa is currently under clinical investigation and its safety and efficacy have not been evaluated by any regulatory authority.

About Phase 3 XTEND-1 study
The Phase 3 XTEND-1 study (NCT04161495) is an open-label, non-randomized interventional study assessing the safety, efficacy and pharmacokinetics of efanesoctocog alfa in people 12 years of age or older (n=159) with severe hemophilia A who were previously treated with factor VIII replacement therapy. The study includes two parallel treatment arms – the prophylaxis arm, where study participants received a weekly prophylactic 50 IU/kg dose of efanesoctocog alfa for 52 weeks (Arm A), some of which were enrolled following an observation period on prophylaxis using currently marketed factor VIII replacement therapies, and an on-demand arm, where study participants received 50 IU/kg as needed for 26 weeks followed by weekly prophylaxis for another 26 weeks (Arm B).

The primary efficacy endpoint was the annualized bleeding rate (ABR) in Arm A, and the key secondary endpoint was an intra-patient comparison of ABR during the efanesoctocog alfa weekly prophylaxis treatment period versus the prior prophylaxis ABR for participants in Arm A who participated in Study 242HA201/OBS16221, an observational study.

Read Also - GSK, Sanofi to seek regulatory authorization for COVID vaccine