Pfizer unveiled very encouraging topline results from its Phase 3 BASIS clinical trial (NCT03938792). The study examined once‑weekly, under‑skin injections of HYMPAVZI™ (marstacimab) in adolescents and adults (12 years+) living with hemophilia A or B complicated by inhibitors an antibody that can neutralize traditional factor replacement therapy.
In this head‑to‑head comparison against on‑demand treatment (where patients receive bypassing agents only during bleeding episodes), HYMPAVZI delivered outstanding results. It slashed the annualized bleeding rate (ABR) by 93%, reducing it from 19.78 bleeds per year with on‑demand therapy to just 1.39 on HYMPAVZI, with the difference being both statistically significant and clinically meaningful (p < 0.0001).
This remarkable reduction was consistent across all bleeding types, including spontaneous, joint, target‑joint, and total bleeds. What's more, the treatment was generally well tolerated, aligning with prior data from Phase 1/2 studies and the non‑inhibitor cohort—there were no reported deaths or blood clotting (thromboembolic) events .
Dr. Davide Matino, the lead investigator from McMaster University, expressed optimism: patients most desperately in need of simpler, reliable treatment now have a promising option. HYMPAVZI’s easy once‑weekly subcutaneous injection could help ease the treatment burden that hemophilia patients with inhibitors often face.
Michael Vincent, Pfizer’s Chief Inflammation & Immunology Officer, emphasized that these results fill a critical unmet need: "They demonstrate HYMPAVZI’s potential to help people living with hemophilia A or B with inhibitors," he said.
