Pfizer Inc. today announced that the first participant has been dosed in the Phase 3 BASIS study of marstacimab (PF-06741086), an anti-tissue factor pathway inhibitor (anti-TFPI) being evaluated for the treatment of people with severe hemophilia A or B, with or without inhibitors.

BASIS is a global Phase 3, open-label, multicenter study that will evaluate annualized bleed rate (ABR) through 12 months on prophylaxis treatment with marstacimab, an investigational, novel subcutaneous therapy, in adolescents and adults with hemophilia A or B compared to a run-in period on replacement therapy with FVIII or FIX clotting factor, respectively, or bypass therapy (i.e., treatments that “bypass” the need for clotting factor treatment to help the body form a normal clot). The primary endpoint is impact on ABR through 12 months following prophylaxis treatment with marstacimab. The incidence and severity of thrombotic events will also be assessed.

“Our approach to hemophilia research includes the investigation of multiple mechanisms to help address the needs of all people with hemophilia, including those with hemophilia A or B, and with or without inhibitors, and targeting TFPI provides a novel approach to improve blood coagulation,” said Brenda Cooperstone, Chief Development Officer, Rare Disease, Pfizer Global Product Development. “Based on the Phase 2 study findings to date, marstacimab may have the potential to offer improved bleed control via subcutaneous injection and potentially eliminate the need for prophylactic factor replacement, providing an enhanced treatment option compared to factor replacement therapy.”

The completed Phase 2 study results demonstrated that treatment with marstacimab showed significant (>75%) reductions in ABR for all participants in the study population. The participants were monitored in a long-term extension study, which showed sustained efficacy up to 12 months and no thrombotic events or treatment-related serious adverse events in 20 participants receiving weekly subcutaneous marstacimab doses at or above the dose to be studied in the BASIS Phase 3 pivotal trial (300 mg subcutaneous loading followed by 150 mg subcutaneous weekly).