NEW YORK, May 13, 2026
Pfizer has received European Commission approval for HYMPAVZI® (marstacimab) for the treatment of adults and adolescents aged 12 years and older with hemophilia A or hemophilia B with inhibitors, marking a major milestone in the evolution of care for patients living with difficult-to-treat bleeding disorders. The approval expands the therapy’s indication across the European Union and positions HYMPAVZI as the only once-weekly subcutaneous treatment approved in Europe for hemophilia A and B with or without inhibitors.
Phase 3 Trial Shows Strong Bleed Reduction
The European Commission decision was supported by results from Pfizer’s pivotal Phase 3 BASIS clinical trial, which demonstrated that HYMPAVZI achieved a 93% reduction in annualized bleeding rates compared with on-demand therapy in patients with inhibitors. Patients receiving the therapy showed significantly lower bleeding episodes across all key secondary endpoints, including spontaneous bleeds, joint bleeds, and total treated bleeds.
The study also showed durable long-term efficacy during an open-label extension trial, where treated annualized bleeding rates remained consistently low for patients receiving HYMPAVZI for up to 53 months. Researchers noted that the therapy maintained favorable clinical outcomes while providing a simplified once-weekly administration schedule.
Pfizer stated that the treatment was generally well tolerated during the study, with the most commonly reported adverse events including injection site reactions, headache, rash, hypertension, and pruritus. The company noted that thrombosis was the most serious adverse event observed during clinical development.
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Once-Weekly Therapy Targets Unmet Need
Hemophilia patients who develop inhibitors face significant treatment challenges because the antibodies neutralize standard clotting factor replacement therapies, making conventional treatment ineffective. According to Pfizer, approximately 20% of patients with hemophilia A and 3% of patients with hemophilia B develop inhibitors that limit treatment options and increase the risk of uncontrolled bleeding episodes.
HYMPAVZI works differently from traditional replacement therapies by targeting tissue factor pathway inhibitor (TFPI), a natural regulator that suppresses blood clot formation. By inhibiting TFPI, the therapy aims to restore balance in the clotting system without replacing missing clotting factors directly.
The approval is particularly important because the therapy provides a subcutaneous once-weekly injection that does not require routine laboratory monitoring, potentially reducing treatment burden for patients and caregivers. Pfizer emphasized that the therapy may help simplify disease management while improving bleed protection for people living with severe forms of hemophilia.
Pfizer Expands Global Hemophilia Strategy
Pfizer executives described the European approval as another important step in the company’s long-standing commitment to advancing hemophilia care globally. The company confirmed that HYMPAVZI has already received approvals in more than 40 countries for eligible hemophilia patients without inhibitors and continues to expand into additional patient populations.
The company also revealed that the U.S. FDA has accepted a supplemental Biologics License Application seeking expanded approval for pediatric patients and patients with inhibitors in the United States, with a regulatory decision expected later in 2026.
The latest European approval strengthens Pfizer’s position in the rapidly evolving hemophilia therapeutics market, where biotechnology companies continue to develop next-generation therapies focused on improved convenience, extended efficacy, and reduced treatment burden for rare disease patients worldwide.
Source: Pfizer press release
