FDA Approves Marstacimab-hncq for Adults, Adolescents With Hemophilia A or B Without Inhibitors

This approval marks the first and only anti-tissue factor pathway inhibitor approved in the US for the treatment hemophilia A or B, and the first approved hemophilia treatment to be administered via a pre-filled, auto-injector pen.

The FDA has approved marstacimab-hncq (Hympavzi; Pfizer) for routine prophylactic use or to reduce the frequency of bleeding episodes in adults and adolescents 12 years of age and older with hemophilia A without factor VIII inhibitors, or with hemophilia B without factor IX inhibitors.

This approval marks the first and only anti-tissue factor pathway inhibitor approved in the US for the treatment hemophilia A or B, and the first approved hemophilia treatment to be administered via a pre-filled, auto-injector pen. Marstacimab-hncq can offer a subcutaneous treatment option with a once-weekly dosing schedule and minimal required preparation for each individual administration, potentially improving ease of use for patients.

“The approval of Hympavzi is a meaningful advancement for people living with hemophilia A or B without inhibitors for bleed prevention, with a generally manageable safety profile and a straightforward once-weekly subcutaneous administration,” said Suchitra S. Acharya, MD, director of Hemostasis and Thrombosis Center Northwell Health and program head of the Bleeding Disorders and Thrombosis Program at Cohen Children’s Medical Center, in a news release.

The inhibitor cohort of the BASIS trial is ongoing, with results anticipated in the third quarter of 2025. Pfizer is also conducting BASIS KIDS, an open-label study investigating the safety and efficacy of marstacimab-hncq in children 1 to less than 18 years of age with severe hemophilia A or moderately severe to severe hemophilia B with or without inhibitors.

In the on-demand treatment group, superiority of marstacimab-hncq was demonstrated across all bleeding-related secondary end points, including spontaneous bleeds, joint bleeds, target joint bleeds, and total bleeds. In the routine prophylaxis group, marstacimab-hncq demonstrated non-inferiority to these secondary efficacy end points.

“The hemophilia community continually seeks advancements in care that can improve quality of life for our community members,” said Phil Gattone, president and CEO of the National Bleeding Disorders Foundation, in a news release. “The availability of this therapy represents a powerful step forward in advancing care for more individuals and families in the bleeding disorders community.”