What is abelacimab?

Abelacimab is an injectable, experimental, anti-clotting medication that is categorized as a factor XI inhibitor. It has the potential to prevent the clots responsible for strokes and heart attacks while preserving the body's natural ability to repair blood vessels after an injury.

How does abelacimab work?

Abelacimab is a monoclonal antibody and it works differently from other anticoagulants because it binds to factor XI and locks it in the zymogen (inactive precursor) conformation. This prevents its activation by factor XIIa or thrombin – both of these substances are important for clot growth and stabilization. It also works within minutes, compared with other anticoagulants that may take up to four weeks to have their full effect. The way abelacimab works means it prevents blood from clotting without increasing the risk of bleeding.

What do trials show?

Venograms were obtained in 98% (400 out of 409) of patients who received abelacimab. Venous thromboembolism occurred in 13% of patients in the 30-mg abelacimab group, 5% in the 75-mg group, and 4% in the 150-mg group, in comparison to 22% in the enoxaparin group. Among the patients with evaluable venograms, three underwent venography outside the days 8 to 12 window, and none of them exhibited deep-vein thrombosis.

Abelacimab significantly lowered bleeding in individuals with atrial fibrillation at risk of stroke, as per the AZALEA-TIMI 71 phase 2 trial results presented at the American Heart Association’s Scientific Sessions 2023. The trial was halted early in September 2023 due to a substantial decrease in bleeding (over 60%) compared to the medication rivaroxaban. This stands as the lengthiest and most extensive trial to date, comparing factor XI inhibitors to the current standard of care involving direct-acting oral anticoagulants.