Pfizer Shares Fall After Patient Death in Hemophilia Drug Study
A patient with hemophilia A died from a stroke, prompting a safety review of the marstacimab trial. The company does not foresee an impact on the approved version of the drug.
Pfizer (PFE) shares declined in Tuesday trading after the company disclosed a patient death in an extension study for its hemophilia treatment, marstacimab. The stock fell by 0.8% to $25.01, reflecting investor concern over the drug's development, even as the company stated it did not anticipate an impact on the already-approved version of the therapy, sold as Hympavzi.
The patient, who had severe hemophilia A, died on December 14 from a cerebellar infarction and cerebral hemorrhage, a type of stroke. The event occurred during a post-surgical period while the patient was receiving marstacimab as a prophylactic, along with another clotting factor. In response, Pfizer has initiated a comprehensive safety review and is reassessing surgical protocols for the ongoing clinical trial.
"The safety and well-being of our patients are our top priorities," a Pfizer spokesperson said in a statement. "We are thoroughly evaluating the case and working closely with trial investigators. We do not currently believe this event will impact the established safety profile of Hympavzi."
This incident casts a shadow over a key asset in Pfizer’s pipeline. Marstacimab is a subcutaneously administered antibody designed to help blood clot, aiming to offer a more convenient treatment option for patients with hemophilia A and B. Clinical trial setbacks are a known risk in pharmaceutical development, but patient deaths can lead to heightened regulatory scrutiny and potential delays.
Analysts have adopted a cautious stance following the news. While the current consensus 12-month price target for Pfizer sits at $28.62, recent commentary has emphasized the criticality of the drug's safety profile for investor confidence. According to a report from AInvest, the stock's December decline was also influenced by the discontinuation of another drug, Beqvez, and weaker-than-expected financial guidance for 2026.
The market for hemophilia treatments is intensely competitive, with established players like Roche, Takeda, and BioMarin. A successful and safeconvenient subcutaneously administered drug like marstacimab could capture significant market share and bolster Pfizer's portfolio as it navigates declining revenues from its COVID-19 products and faces patent expirations for other blockbuster drugs.
The company has affirmed that it remains confident in marstacimab's potential. As reported by Benzinga, the comprehensive safety review is now the immediate focus. Investors and regulators will be closely watching for the outcome of this review and any subsequent communications from the U.S. Food and Drug Administration (FDA).