Pfizer Inc. (NYSE: PFE)today announced that the U.S. Food and Drug Administration (FDA) has accepted and granted Priority Review for the company's supplemental Biologics License Application (sBLA) for HYMPAVZI® (marstacimab) to expand the approved indication to include the treatment of hemophilia A or B patients 6 years and older with inhibitors, and pediatric patients (ages 6 to 11) with hemophilia A or B without inhibitors. In the U.S., HYMPAVZI is currently approved for the treatment of patients 12 years of age and older with hemophilia A without factor VIII (FVIII) inhibitors, or hemophilia B without factor IX (FIX) inhibitors.
The FDA has set a Prescription Drug User Fee Act (PDUFA) action date in the second quarter of 2026. If approved, HYMPAVZI would offer a combination of bleed protection with a straightforward, once-weekly subcutaneous injection administration, requiring minimal preparation and no routine treatment-related lab monitoring for these difficult-to-treat patient populations.
"There is a significant medical need for younger patients with hemophilia and for those who have developed inhibitors, which neutralize factor replacement therapies and render them ineffective," said Michael Vincent, M.D., Ph.D., Chief Inflammation & Immunology Officer, Pfizer. "Based on the findings in the BASIS clinical trial program and if approved, we believe HYMPAVZI has the potential to become a transformative option for these patients that have limited or burdensome treatment options today. We look forward to progressing discussions with regulators to make this medicine available for patients."
Hemophilia is diagnosed in early childhood and impacts more than 800,000 people worldwide.1 The inability of the blood to clot properly can increase the risk of painful bleeding, including inside the joints, which can cause joint scarring and damage.2,3 Children's joints have growing cartilage and bone, which makes them particularly susceptible to damage caused by repeated bleeding episodes.4 Inhibitors, or antibodies, develop in approximately 20% of people with hemophilia A and 3% of people with hemophilia B. People living with inhibitors to FVIII and FIX are unable to continue taking factor replacement therapies as they no longer prevent or stop bleeding episodes, particularly in individuals who are refractory to immune tolerance induction therapy.1,5,6
"For children living with hemophilia A or B between ages 6 and 11, treatment approaches that prevent bleeds are particularly important to protect growing joints," said Guy Young, M.D., Director, Hemostasis and Thrombosis Center at Children's Hospital, Los Angeles. "HYMPAVZI would address a critical unmet medical need for these patients and those with inhibitors if approved, particularly patients ages 6 to 11 with hemophilia B who do not have non-factor treatment options available today."
The FDA grants Priority Review to medicines that may offer significant advances in treatment or may provide a treatment where no adequate therapy exists. Priority Review designation by the FDA shortens the standard sBLA review period by four months.
The FDA also granted HYMPAVZI Breakthrough Therapy Designation for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in younger pediatric (≥6 to <12 years of age) patients with hemophilia B with and without inhibitors. The FDA's Breakthrough Therapy Designation is intended to expedite the development and review of medicines with the potential to treat a serious or life-threatening disease, when preliminary clinical evidence indicates the medicine may demonstrate substantial improvement over existing therapies.
The submission for HYMPAVZI in adults and adolescents is based on efficacy and safety data from the inhibitor cohort of the Phase 3 BASIS trial (NCT03938792extlink label). The submission for HYMPAVZI in children aged 6 to 11 years with or without inhibitors is supported by efficacy and safety data from the Phase 3 BASIS KIDS trial (NCT05611801extlink label).
The use of HYMPAVZI for the treatment of patients 12 years and older living with hemophilia A or B with inhibitors is also under review by the European Medicines Agency.
About HYMPAVZI
Discovered by Pfizer scientists, HYMPAVZI has a unique mechanism of action that is differentiated from FVIII and FIX replacement treatments. Instead of replacing missing or insufficient clotting factors, HYMPAVZI is intentionally designed to target tissue factor pathway inhibitor (TFPI), one of the body's natural mechanisms that inhibits the initiation of blood clotting. By targeting the Kunitz 2 domain of TFPI, HYMPAVZI may help re-establish balance between bleeding and blood clot formation with the goal of offering a combination of bleed protection and straightforward administration.
HYMPAVZI is a hemophilia treatment that has received regulatory approvals in more than 40 countries for eligible patients living with hemophilia A without factor VIII inhibitors, or hemophilia B without factor IX inhibitors. HYMPAVZI was the first anti-TFPI approved in the U.S. and EU for the treatment of hemophilia A or B and the first hemophilia medicine approved in the U.S. and EU to be administered via a pre-filled, auto-injector pen. For eligible people living with hemophilia B, it is the first once-weekly subcutaneous prophylactic treatment. HYMPAVZI is a subcutaneous treatment option with a once-weekly dosing schedule and minimal preparation required for each individual administration.
About the BASIS Clinical Trial
