Study: Pfizer Hemophilia Drug Reduces Bleeding Rates

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The Facts

  • 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.

  • 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.


The Spin

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.


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