Experimental Therapy for Hemophilia Meets Phase 3 Trial Endpoints


An announcement by Pfizer was recently published in Biospace outlining the results of BASIS its Phase 3 clinical trial (NCT03938792). The drug being studied, marstacimab, met its primary endpoints and now holds the potential to be the first non-factor replacement therapy for hemophilia.

According to the Centers for Disease Control, the optimum treatment for hemophilia involves replacing blood clotting factors that are missing. Blood clotting factor concentrates are injected into an individual’s veins.

The treatment for hemophilia generally involves an increase in the body’s supply of clotting factor proteins which are known to be low due to a genetic mutation. Marstacimab’s approach differs from the current standard process by inhibiting a protein that keeps blood from clotting.

Marstacimab’s new approach has been attempted by various drugmakers, but safety risks complicated the clinical testing. As a result, regulators have proceeded with caution in approving new development.

About the Products

The products often referred to as “factor”, use a molecule similar to natural factors in humans. Rather than replacing clotting factors that are insufficient, marstacimab focuses on TFPI, a natural mechanism in the body that inhibits blood clotting.

Non-factor replacement therapies either help to prevent bleeding or improve clotting through methods in the body other than “factor” replacement therapy which is the standard therapy.

The new marstacimab treatments augment the factor in the body to levels leading to improved clotting and hence less bleeding. The therapy is administered intravenously (infusion).

Inhibitors that Prevent Clotting

Individuals with hemophilia or von Willebrand disease type 3 are prone to develop inhibitors that make it difficult to stop bleeding. The inhibitors, as the name implies, prevent the treatment from working.

About the BASIS Phase 3 Trial

The trial involved 116 individuals with hemophilia who were administered marstacimab for a period of twelve months.

The second group received prophylaxis as standard care during the initial six-month period.

In the group of patients who were administered factor replacement therapy, marstacimab reduced bleeds by 92%. Its safety profile remained the same as the Phase ½ results while the treatment in general was well-tolerated. The final results for the second group should be announced in late 2024.


Rose Duesterwald

Rose Duesterwald

Rose became acquainted with Patient Worthy after her husband was diagnosed with Acute Myeloid Leukemia (AML) six years ago. During this period of partial remission, Rose researched investigational drugs to be prepared in the event of a relapse. Her husband died February 12, 2021 with a rare and unexplained occurrence of liver cancer possibly unrelated to AML.

Share this post