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# FDA OKs Pfizer’s Hympavzi for Hemophilia A and B
- URL: https://www.fdaweb.com/fda-oks-pfizers-hympavzi-for-hemophilia-a-and-b/
- Published: 2024-10-11T12:00:00.000Z
- Updated: 2026-09-14T14:43:47.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5157971

FDA has approved a Pfizer BLA for Hympavzi (marstacimab-hncq) for preventing or reducing bleeding episodes in patients aged 12 and older with hemophilia A or B who do not have inhibitors to factor VIII or IX, respectively. The approval marks the first treatment to target a specific protein involved in blood clotting — tissue factor pathway inhibitor — to increase the amount of thrombin, an enzyme that is critical in blood clotting, that is generated, according to an [FDA release](https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-hemophilia-or-b?utm%5Fmedium=email&utm%5Fsource=govdelivery). This is expected to reduce or prevent bleeding episodes.

Hympavzi's approval is based on data from a multi-center study in 116 adult and pediatric male patients with either severe hemophilia A or B, both without inhibitors, the agency says. “In the patients receiving on-demand factor replacement during the first six months of the study, the estimated annualized bleeding rate was 38 compared to the estimated annualized bleeding rate during treatment with Hympavzi of 3.2, showing that Hympavzi was superior to on-demand factor replacement,” it says. “In the initial six-month period during which patients received prophylactic factor replacement, the estimated annualized bleeding rate was 7.85 and was 5.08 during the subsequent 12 months on Hympavzi prophylaxis, showing that Hympavzi provided similar bleeding rates.”

Regarding safety, Hympavzi comes with warnings and precautions about thromboembolic events, hypersensitivity and embryofetal toxicity, FDA says. The most common side effects observed were injection site reactions, headache and itching.