Pfizer has disclosed the death of a patient who was receiving its hemophilia therapy Hympavzi as part of a long-term clinical study. The company said the patient died on December 14 while participating in an extended follow-up trial involving the drug.
The individual was originally enrolled in a Phase III clinical study in 2022 and transitioned into an extension phase in 2023. During the extension period, the patient continued treatment with Hympavzi. According to Pfizer, the therapy was administered as a prophylaxis alongside recombinant factor VIIa, which was used to help prevent bleeding following a minor surgery.
Pfizer reported that the patient experienced serious adverse events during the course of treatment. These events included a stroke and bleeding in the brain. The company did not provide further details on the sequence of events leading up to the patient’s death.
The pharmaceutical company said it is working with the trial investigator and the independent external data monitoring committee to collect and review information related to the case. Pfizer also noted that the patient had co-existing medical conditions and was taking other medications at the time of the adverse events.
In a statement, the company said, “Pfizer, together with the trial investigator and the independent external Data Monitoring Committee, is actively gathering information to better understand the complex, multi-factorial circumstances surrounding this occurrence.”
The death was also referenced by the European Haemophilia Consortium, a patient support group. The organization stated that the patient died after suffering a stroke followed by a brain hemorrhage. According to the group, the patient was enrolled in a study testing Hympavzi in individuals with hemophilia A or B, with or without inhibitors.
Hympavzi was approved in the United States in October 2024 as a once-weekly subcutaneous prophylactic injection for patients with hemophilia A or B without inhibitors. The therapy has since received authorization in Europe. Pfizer has said that, based on its current knowledge and the overall clinical data collected to date, it does not anticipate any impact on safety for patients treated with the drug.
The therapy is an IgG1 monoclonal antibody that targets the Kunitz domain 2 of the tissue factor pathway inhibitor protein. By targeting this protein, the drug enhances blood clotting in patients with hemophilia. People with hemophilia have a defect in a gene that regulates the production of clotting factors, which can result in spontaneous bleeding and severe bleeding after injuries or surgery.
Earlier this year, Pfizer discontinued global development and commercialization of its hemophilia gene therapy Beqvez, citing low patient interest and a shift toward Hympavzi. Beqvez, which was developed in partnership with Sangamo Therapeutics, had been approved in the United States as a one-time therapy for adults with moderate to severe hemophilia B.
Separately, in September 2024, Pfizer withdrew its sickle cell disease treatment Oxbryta from the market after new data showed a higher risk of death and complications in patients who received the therapy.
Hympavzi, developed by Pfizer, was approved in the United States in October 2024 as a once-weekly subcutaneous prophylactic injection for patients with hemophilia A or B without inhibitors, targeting the tissue factor pathway inhibitor protein to enhance blood clotting efficiency. It has since received authorization in Europe and other regions. U.S. Food and Drug Administration
People with hemophilia have a genetic defect that affects production of clotting factors, resulting in spontaneous bleeding and severe bleeding following injuries or surgery. By targeting the Kunitz domain 2 of the tissue factor pathway inhibitor, the therapy aims to reduce bleeding episodes by increasing coagulation activity.
Earlier this year, Pfizer discontinued global development and commercialization of its hemophilia gene therapy Beqvez, citing low patient interest and a strategic shift toward Hympavzi. Beqvez had been approved in the U.S. as a one-time therapy for adults with moderate to severe hemophilia B.
Separately, in September 2024, Pfizer withdrew its sickle cell disease treatment Oxbryta after new data indicated a higher risk of death and complications in patients who received the therapy.
