Patient Dies from Thrombotic Stroke in Pfizer’s Hympavzi Hemophilia Trial After Minor Surgery
A patient with hemophilia A and inhibitors died on December 14, 2025, from a fatal thrombotic stroke (cerebellar infarction followed by cerebral hemorrhage) after minor surgery in Pfizer's long-term open-label extension study of Hympavzi (marstacimab).1234
The patient participated in the parent study in 2022 and entered the extension in 2023, receiving marstacimab prophylaxis for about three years, combined with recombinant factor VIIa for perioperative management.234
Hympavzi, approved in October 2024 for hemophilia A or B without inhibitors, is a rebalancing therapy targeting TFPI to enhance clot formation; thrombosis is a known adverse event of special interest, especially in surgery or with other hemostatics.234
Pfizer is investigating with the trial investigator and an independent Data Monitoring Committee, has notified regulators, and is reviewing surgical protocols; patient support remains available.234
Organizations like World Federation of Hemophilia, National Bleeding Disorders Foundation, and Coalition for Hemophilia B urge close monitoring for thrombosis and express condolences.24
Sources:
1. https://www.noahai.co/discover/article/14053
2. https://stocktwits.com/news-articles/markets/equity/pfizer-confirms-death-of-patient-enrolled-in-hemophilia-drug-study/cLepu4KREHO
3. https://www.investing.com/news/stock-market-news/patient-dies-after-receiving-pfizers-hemophilia-drug-hympavzi-93CH-4421417