Pfizer doses first participant in phase 3 study evaluating anti-TFPI investigational therapy

Pfizer 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).

BASIS is a global Phase 3, open-label, multicenter study evaluating annualized bleed rate through 12 months on treatment with marstacimab, an investigational, novel subcutaneous therapy option, in approximately 145 adolescent and adult participants between ages 12 to <75 years with severe hemophilia A or B (defined as factor VIII or factor IX activity <1%, respectively), with or without inhibitors.

Approximately 20% of participants will be adolescents (ages between 12 to <18 years old). This study is comparing treatment with a run-in period on patients’ prescribed factor replacement therapy or bypass therapy during a 6-month Observational Phase with a 12-month Active Treatment Phase, during which participants will receive prophylaxis (a 300 mg subcutaneous loading dose of marstacimab, followed by 150 mg subcutaneously once weekly) with potential for dose escalation to 300 mg once weekly.

Marstacimab (PF-06741086) is a human monoclonal immunoglobulin G isotype, subclass 1 (IgG1) that targets the Kunitz 2 domain of tissue factor pathway inhibitor (TFPI). Marstacimab is in development as a prophylactic treatment to prevent or reduce the frequency of bleeding episodes in individuals with severe hemophilia A or B (defined as factor VIII or factor IX activity <1%, respectively) with or without inhibitors. In September 2019, the U.S. Food and Drug Administration (FDA) granted Fast Track designation to marstacimab for use in combination with inhibitors as a potential treatment for hemophilia A and B.

Hemophilia is a genetic hematological rare disease that results in a deficiency of a protein that is required for normal blood clotting—clotting factor VIII in hemophilia A and clotting factor IX in hemophilia B. The severity of hemophilia that a person has is determined by the amount of factor in the blood. The lower the amount of the factor, the more likely it is that bleeding will occur which can lead to serious health problems.

Hemophilia A occurs in approximately one in every 5,000-10,000 male births worldwide, and the incidence of hemophilia B is one in 25,000 male births. For people who live with hemophilia, there is an increased risk of spontaneous bleeding as well as bleeding following injuries or surgery. It is a lifelong disease that requires constant monitoring and therapy.