Topline results were announced from a phase 3 study evaluating the efficacy and safety of efanesoctocog alfa (BIVV001) in patients 12 years of age and older with severe hemophilia A previously treated with factor VIII replacement therapy.

Efanesoctocog alfa is a novel recombinant factor VIII (FVIII) therapy designed to extend protection from bleeds by breaking the von Willebrand factor ceiling, which imposes a half-life limitation on current FVIII treatments.

The multicenter, open-label, nonrandomized, interventional XTEND-1 study ( Identifier: NCT04161495) included 159 previously-treated patients with severe hemophilia A. The study included 2 parallel treatment arms: the prophylaxis arm (Arm A), where patients received a weekly prophylactic 50 IU/kg dose of efanesoctocog alfa intravenously (IV) for 52 weeks; and the on-demand arm (Arm B), where patients received a weekly on-demand 50 IU/kg dose of efanesoctocog alfa IV for 26 weeks followed by weekly prophylaxis for 26 weeks.

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The primary endpoint was the annualized bleeding rate (ABR) in Arm A. A key secondary endpoint was the intra-patient comparison of ABR during the efanesoctocog alfa weekly prophylaxis treatment period vs the historical prophylaxis ABR for some of the patients in Arm A who participated in a prior observational study using currently marketed factor VIII replacement therapies.

Findings showed that weekly prophylactic treatment with efanesoctocog alfa resulted in clinically meaningful prevention of bleeds over 52 weeks; the median ABR was 0 with a mean ABR of 0.71. Moreover, once-weekly efanesoctocog alfa was found to be superior to prior prophylactic FVIII replacement therapy, demonstrating a statistically significant reduction in ABR based on intra-patient comparison. The most common treatment-emergent adverse events reported were headache, arthralgia, fall, and back pain.

“These positive top-line data, showing a very low annualized bleeding rate, enhance efanesoctocog alfa’s potential to transform hemophilia A therapy,” said Dietmar Berger, MD, PhD, Global Head of Development at Sanofi. “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.”

The Food and Drug Administration (FDA) previously granted Orphan Drug and Fast Track designations to efanesoctocog alfa for this indication. Study data will be submitted to regulatory authorities in 2022.


Efanesoctocog alfa met primary and key secondary endpoints in pivotal study in haemophilia A, demonstrating superiority to prior factor prophylaxis treatment. News release. Swedish Orphan Biovitrum AB. Accessed March 9, 2022.

This article originally appeared on MPR