FDA approves updated Altuviiio label with full XTEND-Kids data

Once-weekly therapy effective after one year, clinical trial shows

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by Steve Bryson, PhD |

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The U.S. Food and Drug Administration (FDA) has approved an update to the prescribing information for Altuviiio (efanesoctocog alfa), a long-lasting factor VIII (FVIII) replacement therapy for hemophilia A, to include the full results from a clinical trial, the XTEND-Kids study.

As requested by Sanofi, which markets the therapy in the U.S., the label update builds up on interim data from the Phase 3 trial (NCT04759131), which supported Altuviiio’s approval in 2023 as a routine prophylactic (preventive) and on-demand treatment for adults and children with hemophilia A. The therapy is also indicated to manage bleeds occurring during surgery in these patients.

Because children with hemophilia typically clear standard FVIII replacement therapies in the blood faster than adults, multiple injections per week are often needed. Full results from the XTEND-Kids study reinforce that a once-weekly dose of Altuviiio is sufficient to provide bleed protection in young children with hemophilia A.

“Hemophilia is a lifelong condition, so starting children on an early prophylactic regimen can help them stay ahead of bleeds and reduce other potential complications, such as joint damage and pain,” Mindy Simpson, MD, pediatric hematologist/oncologist and assistant professor of pediatrics at Rush University Medical Center in Illinois, said in a Sanofi press release. “Delivering significant bleed protection with a reduced treatment burden can allow families to spend more time on activities and less time focused on infusion schedules.”

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Primary, key secondary goals met

XTEND-Kids evaluated the safety, efficacy, and pharmacological properties of Altuviiio in 74 boys younger than 12 with severe hemophilia A who had previously been treated with other FVIII therapies. Participants received a once-weekly prophylactic regimen of the therapy for one year.

Meeting the study’s primary goal, none of the children enrolled in XTEND-Kids developed inhibitors, or neutralizing antibodies against the treatment that can reduce its effectiveness, according to Sanofi.

Key secondary outcomes, including having a low number of treated bleeds per year, were also met in 72 evaluable patients. The mean annualized bleeding rate for this type of bleeds was 0.6, while the median annualized bleeding rate was zero.

No serious allergic reactions or abnormal blood clotting events were reported. No adverse events led to treatment discontinuation, and no inhibitors have been detected in post-market surveillance data so far. Fever, occurring in more than 10% of patients, was the most common adverse reaction.

Altuviiio’s approval in hemophilia A patients ages 12 and older was supported by positive data from the Phase 3 XTEND-1 trial (NCT04161495), which tested the treatment in 159 patients with severe hemophilia A.

Top-line results from XTEND-1 showed the trial met its main goal of reducing annualized bleeding rates among those treated with Altuviiio. Nearly two-thirds of patients had no bleeds for the entire year, with 93% having fewer than three bleeds.

An ongoing Phase 3 extension study called XTEND-ed (NCT04644575) is evaluating the long-term safety of the therapy in patients who participated in XTEND-1, XTEND-Kids, or any other Altuviiio study.

Jointly developed jointly by Sobi and Sanofi, Altuviiio is a new class of replacement therapy that combines a lab-made version of FVIII with other proteins and protein fragments that help stabilize it and extend the time it remains in the bloodstream.

The FDA previously granted Altuviiio breakthrough therapy, fast-track, and orphan drug designations, all intended to speed its development and review.