American Society of Hirudotherapy

Antimicrobial Peptides (AMPs)

Leech-derived defense molecules with translational potential against drug-resistant pathogens

Last Updated: May 27, 2026Reviewed by: Andrei Dokukin, MD
Biochemistry & mechanismNot a clinical efficacy claim

Last updated: March 18, 2026

Medicinal leeches produce a diverse arsenal of antimicrobial peptides (AMPs) as part of their innate immune defense. These molecules protect the leech gut environment during months-long blood digestion and represent a largely untapped source of novel antimicrobial candidates at a time when antibiotic resistance is a critical global health threat.

Preclinical Research

All leech-derived antimicrobial peptides discussed on this page are at the preclinical research stage. No AMP from leech SGS has entered human clinical trials or received FDA evaluation.

Key AMP Families

Hirunipins

Recently characterized cysteine-rich peptides from Hirudo medicinalis salivary glands. Active against both Gram-positive and Gram-negative bacteria, including multidrug-resistant strains. Mechanism involves membrane disruption via a three-step oligomerization-dependent translocation (ODT) model.

Theromacin & Theromyzin

AMPs identified in Theromyzon tessulatum (a related leech species). Theromacin is an 8.2 kDa cysteine-stabilized peptide with broad-spectrum activity. Both contribute to understanding the leech AMP repertoire across species.

Destabilase-Lysozyme

A dual-function enzyme with both isopeptidase (fibrinolytic) and muramidase (antimicrobial) activities. Cleaves peptidoglycan in bacterial cell walls while simultaneously acting as a thrombolytic agent. See Destabilase for details.

Peptide B

A chloride channel-inhibiting peptide with secondary antimicrobial properties. Part of the broader salivary defense system that maintains sterility during blood storage in the crop.

Hirunipin-2 (2025)

A novel antimicrobial peptide isolated from Hirudo nipponia salivary glands (Advanced Science, 2025, Wiley). Discovered using 3D holotomographic high-throughput screening combined with AI-based bioinformatics by Chosun University and the Korea Basic Science Institute. Demonstrates potent activity against multidrug-resistant bacteria including Acinetobacter species, with significant anti-biofilm activity — particularly relevant given the WHO critical-priority designation of MDR Acinetobacter.

LBrHM1 / NrlHM1 / NrlHM2 (2025)

Three novel antimicrobial peptides identified from the H. medicinalis genome by Serebrennikova et al. (IJMS 2025, 26(14):6903) via heterologous expression in E. coli. These expand the known leech antimicrobial arsenal substantially beyond the classical theromyzin/theromacin/peptide B trio.

Mechanisms of Action

Leech AMPs employ multiple mechanisms to kill or inhibit bacteria:

  • Membrane disruption: Cationic AMPs interact with negatively charged bacterial membranes, forming pores or causing lysis. Hirunipins use a three-step process: surface binding, oligomerization, and translocation.
  • Biofilm disruption: Certain leech AMPs penetrate and disrupt bacterial biofilms, which are a major barrier to conventional antibiotic efficacy in chronic infections.
  • Synergy with antibiotics: Preclinical data shows fractional inhibitory concentration index (FICI) values indicating synergistic or additive effects when leech AMPs are combined with conventional antibiotics.
  • Anti-inflammatory modulation: Some leech AMPs reduce pro-inflammatory cytokine release (TNF-alpha, IL-6, IL-1beta), potentially addressing the dual challenge of infection and inflammation.

Translational Relevance

With the WHO identifying antimicrobial resistance as a top-10 global health threat and the clinical antibiotic pipeline stagnating, leech-derived AMPs represent a promising bioprospecting resource. Key advantages include novel mechanisms of action that differ from conventional antibiotics, broad-spectrum activity against drug-resistant strains, and potential for combination therapy. The 2025 discovery of hirunipin-2 — active against MDR Acinetobacter with anti-biofilm properties — and three novel AMPs (LBrHM1, NrlHM1, NrlHM2) significantly expands the pipeline. Additionally, the demonstration of extracellular vesicle (EV) biogenesis in H. nipponia salivary gland cells (ScienceDirect, 2025) opens a potential natural nanocarrier platform for AMP delivery. Research is at the preclinical stage.

For a detailed analysis of the latest research, including the 2025 hirunipins study, see our Research: Novel Leech Antimicrobial Peptides article.

Research Stage

Leech-derived antimicrobial peptides are at the preclinical research stage. No AMP from leech SGS has entered clinical trials. Discussion of antimicrobial properties is provided as scientific context for the broader leech secretome.

Related Resources

Salivary Gland Complex

440+ proteins across anticoagulant, anti-inflammatory, and antimicrobial functional groups.

Destabilase

Dual-function enzyme — fibrinolytic AND antimicrobial activities.

Drug Development

From leech compounds to FDA-approved drugs and the research pipeline.

Compound Coverage Map

All antimicrobial peptides and hirunipins in the 107-entry leech compound catalogue.

Research Roadmap

AMR-relevant antimicrobial research priorities and pipeline gaps.

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.

Antimicrobial Peptides (AMPs) | ASH