FDA Approves Hympavzi for Hemophilia A and B

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The FDA approved Pfizer’s Hympavzi (marstacimab-hncq) to prevent or reduce the frequency of bleeding episodes in patients age 12 or older with hemophilia A or B without inhibitors (neutralizing antibodies), according to a news release published today.

Hympavzi is the first approved hemophilia medicine administered using a pre-filled, auto-injector pen and the first and only anti-tissue factor pathway inhibitor (anti-TFPI) in the United States. It can be given to patients once a week.

Hemophilia A and B are both rare, genetic blood diseases that prevent blood from clotting due to dysfunction in different blood proteins called coagulation factors. Hemophilia A is caused by a dysfunction in coagulation factor VIII and hemophilia B is characterized by a dysfunction in coagulation factor IX. Patients with these hemophilias bleed longer after injury or surgery and are prone to spontaneous internal bleeding which can cause joint damage. Despite advances in treatment, many patients rely on intravenous infusions, sometimes given multiple times a week, to manage their condition.

Hympavzi reduces the activity of the Kunitz 2 domain of tissue factor pathway inhibitor, which is a natural anticoagulant protein found in the body.

“The hemophilia community continually seeks advancements in care that can improve quality of life for our community members,” Phil Gattone, president and CEO of the National Bleeding Disorders Foundation said in the 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.”

This approval was made using data from the phase 3 BASIS trial in which Hympavzi initially reduced patients’ annualized bleeding rate (ABR) by 35% and 92% after 12 months of active treatment, when compared to routine prophylaxis and on-demand (OD) treatment. The trial consisted of 116 male patients with either severe hemophilia A or severe hemophilia B.

Side effects were reported in at least 3% of participants, the most common being injection site reactions, headaches and itchiness.

The full prescribing information will be available soon.

The BASIS KIDS trial is ongoing. It is an open-label study examining the effectiveness and safety of Hympavzi in children with hemophilia A or B with or without inhibitors. Results are expected in the third quarter of 2025.