The U.S. Food and Drug Administration (FDA) has accepted and granted Priority Review for Pfizer’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.”

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 submission for HYMPAVZI in adults and adolescents is based on efficacy and safety data from the inhibitor cohort of the Phase 3 BASIS trial (NCT03938792). 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 (NCT05611801).

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.

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