American Society of Hirudotherapy

Recent advances in the discovery and development of factor XI/XIa inhibitors.

Review published in Medicinal research reviews (2018)

Last Updated: June 18, 2026Reviewed by: ASH Editorial Board
Research article — evidence reviewArticle reference
Evidence: Narrative reviewClinical TrialsSalivary PharmacologyGenomics & ProteomicsSafety & Infection ControlAl-Horani RA et al. · Medicinal research reviews, 2018

Abstract

Factor XIa (FXIa) is a serine protease homodimer that belongs to the intrinsic coagulation pathway. FXIa primarily catalyzes factor IX activation to factor IXa, which subsequently activates factor X to factor Xa in the common coagulation pathway. Growing evidence suggests that FXIa plays an important role in thrombosis with a relatively limited contribution to hemostasis. Therefore, inhibitors targeting factor XI (FXI)/FXIa system have emerged as a paradigm-shifting strategy so as to develop a new generation of anticoagulants to effectively prevent and/or treat thromboembolic diseases without the life-threatening risk of internal bleeding. Several inhibitors of FXI/FXIa proteins have been discovered or designed over the last decade including polypeptides, active site peptidomimetic inhibitors, allosteric inhibitors, antibodies, and aptamers. Antisense oligonucleotides (ASOs), which ultimately reduce the hepatic biosynthesis of FXI, have also been introduced. A phase II study, which included patients undergoing elective primary unilateral total knee arthroplasty, revealed that a specific FXI ASO effectively protects patients against venous thrombosis with a relatively limited risk of bleeding. Initial findings have also demonstrated the potential of FXI/FXIa inhibitors in sepsis, listeriosis, and arterial hypertension. This review highlights various chemical, biochemical, and pharmacological aspects of FXI/FXIa inhibitors with the goal of advancing their development toward clinical use.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

Publication typeJournal ArticleResearch Support, N.I.H., ExtramuralReview
Indexed MeSH termsAnimalsAnticoagulantsBlood CoagulationDrug DevelopmentDrug DiscoveryFactor XIFactor XIaHumans

Summary

Factor XIa (FXIa) is a serine protease homodimer that belongs to the intrinsic coagulation pathway. FXIa primarily catalyzes factor IX activation to factor IXa, which subsequently activates factor X to factor Xa in the common coagulation pathway.

Why This Matters for Hirudotherapy

This review surveys the past decade of efforts to inhibit coagulation factor XI/XIa, summarizing diverse approaches (polypeptides, peptidomimetics, allosteric inhibitors, antibodies, aptamers, and antisense oligonucleotides) and noting a Phase II signal that an FXI antisense agent protected knee-arthroplasty patients against venous thrombosis with relatively limited bleeding. For hirudotherapy, it situates the medicinal-leech anticoagulant tradition within the broader modern goal that motivates leech-secretome drug discovery: blocking specific clotting factors to prevent thrombosis while sparing hemostasis and reducing bleeding risk. As a narrative review it aggregates and interprets other groups' findings rather than reporting new data, and it centers on FXI/FXIa drug candidates, not on leech-derived therapeutics or hirudotherapy itself; the cited Phase II result applies to one antisense agent in a surgical population, not to leech treatment.

Citation

Recent advances in the discovery and development of factor XI/XIa inhibitors.

Al-Horani RA et al. · Medicinal research reviews, 2018

Added to ASH library: May 28, 2026 · Site last updated: June 18, 2026

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