Study: Pfizer Hemophilia Drug Reduces Bleeding Rates

    Study: Pfizer Hemophilia Drug Reduces Bleeding Rates
    Last updated Jun 01, 2023
    Image credit: Wikimedia Commons


    • On Tuesday, US drugmaker Pfizer announced the results of a late-stage study for its experimental hemophilia therapy, marstacimab, claiming that the drug reduced bleeding rates in patients with severe hemophilia A and moderately severe to severe hemophilia B without inhibitors.[1]
    • The phase 3 BASIS clinical trial of the under-the-skin therapy, which blocks the anticoagulant protein known as tissue factor pathway inhibitor (TPFI), reportedly demonstrated superiority compared to prophylaxis and on-demand factor replacement therapies, reducing bleeding by 35% and 92%, respectively.[2]
    • Pfizer claims the results could make marstacimab the first once-weekly subcutaneous treatment for hemophilia B, as well as the first treatment administered as a flat dose for people living with either hemophilia A or B.[3]
    • As a next step, Pfizer plans to discuss the trial's results with regulatory authorities in the coming months, and begin the process of seeking marstacimab's regulatory approval.[4]
    • Last month, Novo Nordisk received a complete response letter (CRL) from the FDA on the regulatory filing for its own anti-TFPI, concizumab, in hemophilia A and B patients. The agency also requested additional data on the drug's administration and manufacturing process.[5]
    • The US Centers for Disease Control and Prevention (CDC) estimates that as many as 33K males in the US are living with hemophilia, an inherited bleeding disorder in which the blood does not clot properly.[6]


    Narrative A

    This study's results are promising and could be the first step towards Pfizer's marstacimab revolutionizing treatment for patients with hemophilia A or B. These results suggests the drug could prevent excessive bleeds and reduce treatment burden through once-weekly, under-the-skin administration.

    Narrative B

    While the experimental therapy is undeniably innovative — as it reduces the amount of anticoagulation instead of addressing the factor deficiency — TFPI blockers in marstacimab can cause clotting episodes that do not usually show up in small studies. The medical community should not get too excited about this development too soon.

    Articles on this story

    Sign up to our newsletter!