Efanesoctocog alfa (Altuviiio®), a first-in-class, high-sustained factor VIII replacement therapy, has been granted a supplemental biologics license application (sBLA) by the US Food and Drug Administration (FDA). This therapy has demonstrated its efficiency in providing highly effective bleed protection with once-weekly dosing for children suffering from hemophilia A.

The Prescription Drug User Fee Act action date is scheduled for May 10, 2024.

“In the U.S., treatment advances over time have given children living with hemophilia the opportunity to move from watching sports as a spectator to becoming an active participant with certain limitations and considerations. With Altuviiio, we are building on this momentum by offering a first-of-its-kind option with proven bleed protection and reduced treatment burden for healthcare providers and caregivers of children with hemophilia A,” said Jeff Schaffnit, head of US rare blood disorders at Sanofi.

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Efanesoctocog alfa received Breakthrough Therapy designation from the FDA in May 2022, becoming the first factor VIII therapy to receive this designation. It also received Fast Track designation in February 2021, and Orphan Drug designation in 2017. The European Commission granted Orphan Drug designation in June 2019.

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The open-label, nonrandomized XTEND-Kids study enrolled 74 patients to evaluate efanesoctocog alfa as once-weekly prophylaxis for 52 weeks in patients with severe hemophilia A under 12 years old. Efanesoctocog alfa successfully met its primary endpoint by demonstrating no factor VIII inhibitor development. It also achieved key secondary endpoints.

Furthermore, efanesoctocog alfa maintained factor activity levels in the normal to near-normal range for approximately 3 days. The safety profile was similar to that of the XTEND-1 trial (for individuals 12 years or older), with no reported serious allergic reactions, anaphylaxis, or embolic or thrombotic events.

In addition to XTEND-1 and XTEND-Kids, there is an ongoing extension study (XTEND-ed) to evaluate the long-term safety and efficacy of efanesoctocog alfa in previously treated patients with severe hemophilia A.


ALTUVIIIO® supplemental biologics license application based on positive final results from phase 3 XTEND-Kids study accepted by FDA. News release. Sanofi; September 12, 2023.

Long-term safety and efficacy of efanesoctocog alfa (BIVV001) in previously treated patients with hemophilia A (XTEND-ed). ClinicalTrials.gov. November 25, 2020. Updated March 14, 2023. Accessed September 18, 2023.