FDA Approves New Once-Weekly Therapy for Hemophilia A or B

The Food and Drug Administration approved marstacimab-hncq (Hympavzi, Pfizer) on Friday for the treatment of adults and adolescents with hemophilia A or B without inhibitors. The therapy is the first non-factor, once-weekly treatment for hemophilia B.

Unlike traditional factor replacement therapies, marstacimab is a rebalancing agent that works by targeting the Kunitz 2 domain of tissue factor pathway inhibitor (TFPI), a natural anticoagulation protein that inhibits clot formation. By reducing TFPI activity, the treatment increases thrombin generation, helping to prevent or reduce the frequency of bleeding episodes in patients.

FDA based its approval on findings from the Phase 3 BASIS trial, which involved 116 patients. Marstacimab reduced the annualized bleeding rate for treated bleeds by 92% compared to on-demand treatment and by 35% compared to routine prophylaxis,

Marstacimab comes with warnings and precautions about thromboembolic events, hypersensitivity and embryofetal toxicity. The most common side effects were injection site reactions, headache and itching.