European Commission expands Pfizer’s HYMPAVZI label to cover haemophilia A and B patients with inhibitors

Pfizer has secured a broader European marketing authorization for HYMPAVZI® (marstacimab), with the European Commission clearing the medicine for patients aged 12 and over weighing at least 35 kg who have haemophilia A (congenital factor VIII deficiency) with FVIII inhibitors or haemophilia B (congenital factor IX deficiency) with FIX inhibitors. The decision establishes HYMPAVZI as the only once-weekly subcutaneous therapy approved across the EU spanning haemophilia A and B, with or without inhibitors.

For this hard-to-treat group, HYMPAVZI delivered superior bleed protection versus on-demand treatment in clinical testing while sparing patients the routine lab monitoring that typically accompanies haemophilia care. The drug is administered weekly under the skin and was generally well tolerated in the supporting studies.

Inhibitors are a long-standing obstacle in haemophilia management: these antibodies neutralize standard factor replacement therapy and leave patients exposed to uncontrolled bleeds. Of the more than 800,000 people worldwide living with haemophilia A or B, roughly 20% of those with haemophilia A and around 3% of those with haemophilia B develop inhibitors that take factor replacement off the table — particularly when immune tolerance induction does not succeed.

“Inhibitors present a substantial challenge for people living with hemophilia as they neutralize traditional factor replacement therapies, in turn limiting treatment options and leaving patients vulnerable to uncontrolled bleeding episodes,” said Dr. Laurent Frenzel, Head of the Hemophilia Treatment and Research Center at the Necker-Enfants malades Hospital (Paris Cité). “The approval of HYMPAVZI offers adults and adolescents in the EU a once-weekly subcutaneous option that has demonstrated the ability to reduce bleeding episodes and maintain bleed reduction based on observation to date in a long-term extension study.”

“For people living with hemophilia with inhibitors, recurring bleeding episodes can lead to damaged joints and introduce real limitations and disruptions to everyday life,” said Alexandre de Germay, Chief International Commercial Officer and Executive Vice President, Pfizer. “This approval brings a once-weekly medicine to the EU that meets a critical need for patients who face a treatment journey that can be complex and challenging with limited options available today, representing the latest step in Pfizer’s more than 40-year commitment to advancing care for people living with hemophilia. We look forward to working with regulators globally to continue bringing HYMPAVZI to those who can benefit from it.”

The label expansion rests on the Phase 3 BASIS study, which enrolled adults and adolescents aged 12 and over with severe haemophilia A or moderately severe to severe haemophilia B and inhibitors. During the active treatment period, HYMPAVZI cut the mean treated annualized bleeding rate (ABR) by 93% versus on-demand therapy — 1.39 (95% CI 0.85–2.29) compared with 19.78 (95% CI 16.12–24.27); p<0.0001 — clearing the bar for superiority. The medicine also outperformed on-demand treatment (p≤0.0001) on every prespecified bleeding-related secondary endpoint, including spontaneous bleeds, joint bleeds, target joint bleeds, and total treated and untreated bleeds. An interim analysis of the open-label extension, in which patients continued on HYMPAVZI for up to a further 41 months (53 months in total), showed bleed control held up over time, with a mean treated ABR of 1.19 (95% CI 0.72–1.95) and a median of 0.00 (95% CI 0.00–1.18).

The safety profile lined up with prior Phase 1/2 readouts. The most commonly reported adverse events were injection site reactions, headache, pruritus, hypertension and rash, with thrombosis the most serious event flagged across the program.

The authorization applies in all 27 EU member states as well as Iceland, Liechtenstein and Norway. In parallel, the US Food and Drug Administration accepted a supplemental Biologics License Application earlier this year under Priority Review, seeking to extend the US label to cover patients aged 6 and over with inhibitors, and paediatric patients (6–11) without inhibitors. HYMPAVZI is currently authorized in the US for routine prophylaxis in adults and children aged 12 and over with haemophilia A or B but without inhibitors. A Prescription Drug User Fee Act decision is expected in the second quarter of 2026.

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Related Topics and Keywords

haemophilia A and B, inhibitors, Pfizer, Pfizer's HYMPAVZI