The US Food and Drug Administration has approved a new high-sustained factor VIII (FVIII) replacement therapy—efanesoctocog alfa (ALTUVIIIO™ [Antihemophilic Factor (Recombinant), Fc-VWF-XTEN Fusion Protein-ehtl])—for the treatment of hemophilia A.

Efanesoctocog alfa is indicated for routine prophylaxis and control of bleeding episodes, as well as the perioperative management of adults and children with hemophilia. It is the first and only treatment for hemophilia A that delivers near to near-normal factor activity levels (ie, >40%) for most of the week with the use of once-weekly dosing, according to a press release from Sanofi.

Additionally, efanesoctocog alfa is associated with significant reductions in bleeds compared with prior FVIII treatments.

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In patients with hemophilia A, the ability of the blood to clot appropriately is impaired, which may be associated with excessive bleeds and spontaneous bleeds into joints. This can lead to joint damage and chronic pain, potentially impacting an individual’s quality of life.

According to Paul Hudson, chief executive officer at Sanofi, which markets efanesoctocog alfa with Sobi, the approval “allows patients and physicians to reimagine living with hemophilia. . . . For the first time, with a once-weekly dose, powerful bleed protection is a reality for patients.”

Learn more about the history of hemophilia

The FDA approval is based on findings from the pivotal phase 3 XTEND-1 study, which were published recently in The New England Journal of Medicine. Treatment with once-daily efanesoctocog alfa prophylaxis met the primary endpoint, demonstrating significant bleed protection with a mean annualized bleeding rate (ABR) of 0.70 (95% CI, 0.5-1.0) and a median ABR of 0.0 (Q1: 0.0; Q3: 1.0).

The agent met its secondary endpoint as well, with a significant reduction in ABR of 77%, compared with the use of previous factor prophylaxis (95% CI, 58%-87%).

Additional data revealed that treatment with efanesoctocog alfa provided 100% resolution of target joints—that is, the joints in which recurrent bleeds can occur (eg, knees, ankles, elbows). For most of the week, efanesoctocog alfa therapy was associated with mean FVIII activity of more than 40%; the mean FVIII at day 7 was greater than 10%.

Interim data from XTEND-Kids trial demonstrated that among 23 children aged less than 12 years who received once-weekly efanesoctocog alfa for 26 weeks, a mean ABR of 0.5 was reported (95% CI, 0.2-1.3), along with a median ABR of 0.0 (Q1: 0.0; Q3: 1.0).

Across studies, efanesoctocog alfa has an established safety profile. No FVIII inhibitor development was reported with efanesoctocog alfa, although inhibitors can form following administration of it. The most frequently occurring adverse effects, which were reported in more than 10% of patients, included arthralgia and headache.


FDA approves once-weekly ALTUVIIIO™, a new class of factor VIII therapy for hemophilia A that offers significant bleed protection. News release. Sanofi; February 23, 2023.