BREAKING NEWS: Anthos Therapeutics’ Novel Dual-Acting Factor XI/XIa Inhibitor, Abelacimab, Demonstrated a 67% Greater Reduction in the Primary Endpoint of Major or Clinically Relevant Non-Major Bleeding 
Compared to Rivaroxaban in Patients with Atrial Fibrillation

The clinical promise of Factor XI inhibition has given rise to a number of investigational compounds. Within this emerging class of Factor XI inhibitors, abelacimab – a highly selective, fully human monoclonal antibody – stands out due to its novel dual activity against both Factor XI and its activated form, Factor XIa. This dual activity enables profound suppression of Factor XI activity.

Abelacimab is a highly selective, fully human monoclonal antibody

Phase I and 2 clinical studies confirmed that a single 150mg dose of abelacimab (intravenous or subcutaneous) effectively suppresses Factor XI for at least 30 days.


The groundbreaking results of our Phase 2 efficacy study – in which abelacimab significantly outperformed standard of care enoxaparin – was published in 2021 in the The New England Journal of Medicine.2

In this prospective study of 412 patients undergoing elective total knee arthroplasty, a single post-operative IV dose of abelacimab (75mg or 150mg) reduced the rate of venous thromboembolism by ~80% compared to standard of care enoxaparin (40mg SC once daily).

Abelacimab was well tolerated with no safety signals and bleeding was insignificant in both study arms.

The ability of abelacimab to provide effective anticoagulation with a reduced rate of bleeding relative to DOACs will be assessed in the ongoing AZALEA-TIMI 71- TIMI STUDY GROUP study in atrial fibrillation.

Created for the heterogeneous real world, abelacimab has the promise of suitability for a broad spectrum of patients, no requirement for dosage adjustment in cases of renal or hepatic impairment and no interactions with other drugs.

It is planned to be available as a rapid-onset intravenous presentation to prevent VTEs in the inpatient setting and a once-monthly subcutaneous version for ongoing protection in the community, with the anticipation of improved adherence.

1 papagrigoriou, E. et al nat Struct Mol Biol 2006; 13:557-558
2 Verhamme P et al. n Engl J Med 2021; 385:609-617