American Society of Hirudotherapy

Therostasin

Factor Xa inhibitor from Theromyzon tessulatum — Kunitz-domain analog with novel selectivity profile.

Preclinical / mechanisticLast updated: 2026-05-26 · Reviewed by ASH Editorial Board
Molecular weight of Therostasin compared with other characterized leech-derived compoundsHementerin80 kDaHementin80 kDaHementin-Like Protein (HLP-1)80 kDaLeech Collagenase70 kDaHaemadipsa yanyuanensis Progr…70 kDaLeech Apyrase67 kDaCalin65 kDaHyaluronidase60 kDaAntithrombin III binding prot…58 kDaCollagenolytic Fibrinolysin55 kDaLeech Thrombospondin-Like Pro…50 kDaTherostasin14 kDa
Molecular weight (kilodaltons) of Therostasin (highlighted) alongside other characterized leech salivary compounds. Smaller proteins/peptides generally diffuse and act faster.

Mechanistic Evidence Box

Preclinical / mechanistic
Page type
Compound profile
Evidence type
Factor Xa inhibitor from Theromyzon tessulatum — Kunitz-domain analog with novel selectivity profile.
Evidence level
In vitro
Drug vs leech
Purified natural compound
Safety domains
Bleeding

Clinical translation limit

Therostasin's in vitro inhibition of Factor Xa does not establish clinical efficacy. No FDA-approved derivative exists. Mechanism is preclinical/biochemical only.

Molecular Profile

Category
Anticoagulant
Evidence tier
Preclinical
Molecular weight
14,000 Da
Source species
Theromyzon tessulatum
Discovered
1999 · Chopin V et al.
Therostasin molecular structure

Biological Targets

  • → Factor Xa

Key Citations

  1. Chopin V et al. (2000), J Biol Chem · PMID 10852926

External Resources

    Related Anticoagulant Compounds

    Hirudin

    The most potent natural thrombin inhibitor — and the molecular template for three FDA-approved direct thrombin inhibitor drugs.

    Antistasin

    Factor Xa inhibitor — prototype molecule that inspired the entire DOAC drug class (rivaroxaban, apixaban).

    Ghilanten

    Factor Xa inhibitor with anti-metastatic activity in animal cancer models — translational dual-use compound.

    Lefaxin

    Factor Xa inhibitor with anti-inflammatory properties.

    ← Back to Compound Reference

    This website provides educational information and does not constitute medical advice, diagnosis, or treatment recommendations. Medicinal leech therapy carries clinically meaningful risks and should be performed only by qualified clinicians under institutionally approved protocols. FDA 510(k) clearance for medicinal leeches is limited to specific indications; investigational and off-label discussions are labeled accordingly. For patient-specific guidance, consult a qualified healthcare provider.