Objective:

To report the FDA's approval of an expanded indication for marstacimab-hncq (HYMPAVZI) for routine prophylaxis in hemophilia A and B patients.

Key Findings:

• In the BASIS trial, marstacimab reduced the mean treated annualized bleeding rate (ABR) by 93% compared to on-demand treatment.
• Mean treated ABR was 1.4 for marstacimab versus 19.8 for on-demand treatment (p<0.0001).
• In BASIS KIDS, mean treated ABR was 1.8 for patients without inhibitors and 1.4 for those with inhibitors, compared to historical rates of 3.6 and 18.9, respectively.

Interpretation:

Marstacimab targets the Kunitz 2 domain of tissue factor pathway inhibitor (TFPI) to restore balance between bleeding and coagulation.

Limitations:

• Interim results from BASIS KIDS are descriptive analyses and not inferential comparisons.
• Reference rates in BASIS KIDS are historical model-based estimates.

Conclusion:

Marstacimab is the first subcutaneous non-factor therapy available for pediatric patients with hemophilia B aged 6 to 11 years.