American Society of Hirudotherapy

The collagen-binding leech products rLAPP and calin prevent both von Willebrand factor and alpha2beta1(GPIa/IIa)-I-domain binding to collagen in a different manner

Research article published in Thromb Haemost (1999)

Last Updated: June 18, 2026Reviewed by: ASH Editorial Board
Research article — evidence reviewArticle reference
Evidence: Research reportSalivary PharmacologyDrug DevelopmentDepraetere H et al. · Thromb Haemost, 1999

Abstract

Calin and rLAPP are two natural inhibitors that are able to inhibit the vWF-binding and platelet adhesion to collagen both under static and flow conditions. In this study we demonstrate that both rLAPP and Calin prevent alpha2I-domain binding to human collagen type I with an IC50 of 5 microg/ml. However, although both vWF and alpha2I-domain binding to collagen is prevented by rLAPP and Calin, the latter two do not bind to the same collagen site since Calin only partially could compete with rLAPP for binding to collagen. Also vWF and the alpha2I-domain were unable to compete completely with each other for the binding to collagen. So the following hypothesis can be made: the binding sites of vWF and of the alpha2I-domain on human collagen type I are different but close to each other since rLAPP could inhibit both interactions, and thus should bind to an overlapping epitope. The Calin preparation on the other hand may still contain two active principles, one interfering with vWF-binding, the other with the alpha2I-domain-binding to collagen.

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

Publication typeJournal ArticleResearch Support, Non-U.S. Gov't
Indexed MeSH termsBase SequenceBinding SitesBinding, CompetitiveCollagenDNA, ComplementaryHumansIn Vitro TechniquesIntegrinsInvertebrate HormonesPlatelet Aggregation InhibitorsProtein BindingReceptors, Collagen

Summary

rLAPP and Calin both prevent alpha2I-domain binding to human collagen type I with IC50 of 5 microg/ml; the two inhibitors do not bind to the same collagen site since Calin only partially competes with rLAPP.

Why This Matters for Hirudotherapy

This in-vitro study examined two collagen-binding leech-derived inhibitors, recombinant LAPP (rLAPP) and Calin, and showed both prevent the platelet integrin α2β1 (GPIa/IIa) I-domain from binding human collagen type I (IC50 ~5 µg/ml) in addition to blocking von Willebrand factor–collagen binding, while mapping evidence suggests they act at different but overlapping collagen sites. It is directly relevant to the leech secretome drug-discovery narrative because it characterizes how specific leech salivary proteins interrupt the very first steps of platelet adhesion — a distinct antithrombotic mechanism from hirudin's thrombin inhibition. Honest caveat: this is mechanistic biochemistry on isolated molecules under static and flow conditions, not an animal or clinical study, so it explains how these leech proteins work but says nothing about safety, dosing, or therapeutic benefit in patients.

Citation

The collagen-binding leech products rLAPP and calin prevent both von Willebrand factor and alpha2beta1(GPIa/IIa)-I-domain binding to collagen in a different manner.

Depraetere H et al. · Thromb Haemost, 1999

DOI

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