Clinical Report: FDA Expands Marstacimab Indication in Hemophilia A and B

Overview

The FDA has approved an expanded indication for marstacimab-hncq (HYMPAVZI) for routine prophylaxis in patients aged 12 years and older with hemophilia A or B with inhibitors, and in pediatric patients aged 6 to 11 years. This approval is based on significant reductions in annualized bleeding rates observed in clinical trials.

Background

Hemophilia A and B are serious bleeding disorders that require effective management to prevent bleeding episodes. The introduction of marstacimab as a non-factor therapy offers a new treatment option for patients, particularly those with inhibitors, who often face challenges with traditional therapies. The expanded indication for both adults and pediatric patients underscores the need for innovative treatments in this patient population.

Data Highlights

Key Findings

• Marstacimab reduced the mean treated annualized bleeding rate (ABR) by 93% in the inhibitor cohort compared to on-demand treatment.
• The mean treated ABR was significantly lower in patients receiving marstacimab compared to historical rates in both inhibitor and non-inhibitor cohorts.
• Marstacimab is administered once weekly via subcutaneous injection, simplifying treatment regimens.
• The most common adverse reactions included injection-site reactions, headache, and pyrexia.
• Warnings include potential thromboembolic events and hypersensitivity reactions.

Clinical Implications

The approval of marstacimab provides a new prophylactic option for patients with hemophilia A and B, particularly those with inhibitors, enhancing treatment adherence and potentially improving quality of life. Clinicians should be aware of the safety profile and monitor for adverse reactions, especially thromboembolic events.

Conclusion

Marstacimab represents a significant advancement in the management of hemophilia A and B, offering a novel mechanism of action and the potential for improved clinical outcomes in a challenging patient population.

Related Resources & Content

1. Pfizer, Business Wire, 2026 -- U.S. FDA Approves Pfizer’s HYMPAVZI for the Treatment of Two Additional Hemophilia A or B Patient Populations with Significant Medical Need
2. Marstacimab prophylaxis in hemophilia A/B without inhibitors: results from the phase 3 BASIS trial - PubMed
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7. U.S. FDA Approves Pfizer’s HYMPAVZI for the Treatment of Two Additional Hemophilia A or B Patient Populations with Significant Medical Need
8. Marstacimab prophylaxis in hemophilia A/B without inhibitors: results from the phase 3 BASIS trial - PubMed
9. Anti-Tissue Factor Pathway Inhibitors in Hemophilia | NBDF