What Is Omiganan? Definition and What Research Reports

Omiganan is a short, synthetic cationic antimicrobial peptide developed as an analogue of indolicidin, a tryptophan-rich peptide originally isolated from bovine neutrophils. It is most often encountered in the literature as omiganan pentahydrochloride, the salt form used in topical formulation and clinical research, and it has been described as one of the antimicrobial peptides taken furthest into clinical application (review of omiganan pentahydrochloride in clinical applications of antimicrobial peptides). In peptide research vocabulary, "omiganan" is used as a reference compound for the host-defence peptide class: a linear, positively charged, membrane-interacting molecule studied for antibacterial, antifungal and immune-modulating properties rather than for any metabolic or performance-related purpose. This page is for educational purposes only and is not medical advice; consult a licensed physician for any health question.

Molecule Class and Origin

Omiganan belongs to the cationic antimicrobial peptide (CAMP) family, sometimes called host-defence peptides. These are short amino-acid chains carrying a net positive charge and a substantial proportion of hydrophobic residues, a combination that allows them to associate with negatively charged microbial membranes. Omiganan's parent molecule, indolicidin, is a naturally occurring 13-residue peptide from bovine neutrophil granules; omiganan was engineered from that template to alter its activity and tolerability profile.

Biophysical work characterised how the peptide engages membranes directly. Researchers studying omiganan's interaction with bacterial membranes and cell-wall models reported that the peptide's behaviour depended on lipid saturation, and assigned a biological role to the degree of acyl-chain saturation in the target membrane (omiganan interaction with bacterial membranes and cell wall models). That mechanistic framing — surface charge attraction followed by membrane perturbation — is the standard way the class is described in review literature.

Naming conventions

• Omiganan — the peptide itself, as referred to in most literature.
• Omiganan pentahydrochloride — the hydrochloride salt used in topical research formulations (review, 2006).
• Retro-omiganan — a reversed-sequence analogue used as a comparator in antimicrobial screening (anticandidal activity of omiganan and its retro analog).
• Omiganan-based synthetic peptides — derivative sequences designed from the omiganan scaffold (omiganan-based synthetic antimicrobial peptides, 2024).

How the Term Is Used in Peptide Research

Across the published record, "omiganan" appears in three broad research contexts. The first is antimicrobial screening, where the peptide serves as a test agent against bacterial and fungal isolates. The second is topical dermatology research, where it has been evaluated in human skin models and inflammatory skin conditions. The third is immunology, where investigators examined whether the peptide modifies innate immune signalling rather than simply killing microbes. The table below summarises those usages as they appear in the cited literature.

What the Published Literature Reports

Antimicrobial and antifungal findings

In vitro work tested omiganan pentahydrochloride against Staphylococcus aureus isolates that were vancomycin-tolerant, vancomycin-intermediate or vancomycin-resistant, and reported activity across those categories (Diagnostic Microbiology and Infectious Disease, 2008). A separate group evaluated antimicrobial and antifungal activity in experimental skin colonisation models, examining how the peptide performed against organisms established on skin rather than in broth alone (International Journal of Antimicrobial Agents, 2009). Researchers also compared omiganan with a retro (reversed-sequence) analogue against Candida species, both alone and in combination with fluconazole (Probiotics and Antimicrobial Proteins, 2021), and a later study assessed the antistaphylococcal potential of omiganan and retro-omiganan specifically under flow conditions, a model intended to better approximate biofilm environments (Probiotics and Antimicrobial Proteins, 2025).

Immune-modulating findings

Beyond direct microbial killing, the study of omiganan in human peripheral blood mononuclear cells reported that the peptide enhanced interferon responses to endosomal Toll-like receptor ligands (Clinical and Translational Science, 2020). A complementary human study reported that omiganan enhanced imiquimod-induced inflammatory responses in the skin of healthy volunteers (Clinical and Translational Science, 2020). Together these reports positioned the peptide as an immune-modulating agent in addition to a direct antimicrobial.

Clinical and formulation research

A randomised, placebo-controlled phase II trial examined the pharmacodynamic effects of topical omiganan in patients with mild to moderate atopic dermatitis (Clinical and Translational Science, 2020). Formulation researchers characterised liposomes encapsulating omiganan and evaluated them pharmacodynamically in mouse models of atopic dermatitis and psoriasis (International Journal of Pharmaceutics, 2022). Other groups extended the scaffold into new indications, designing omiganan-based synthetic antimicrobial peptides aimed at infectious endophthalmitis (ACS Biomaterials Science & Engineering, 2024), while an animal study examined the effect of omiganan on colonic anastomosis healing in a rat model of peritonitis (American Journal of Translational Research, 2017).

Tolerability and Adverse Events: What Studies Report

The verified literature summarised here reported on activity and pharmacodynamics rather than presenting detailed safety tabulations. The human volunteer work described enhancement of imiquimod-induced inflammatory responses in skin, which is an intended pharmacodynamic readout in that challenge model rather than a safety signal per se (Clinical and Translational Science, 2020), and the atopic dermatitis trial was described as randomised and placebo-controlled with pharmacodynamic endpoints (Clinical and Translational Science, 2020). The 2006 review discussed omiganan pentahydrochloride's progression into clinical applications among antimicrobial peptides (Recent Patents on Anti-Infective Drug Discovery). No specific dosing figures are reproduced here because the cited abstracts do not supply them.

Summary of the Definition

• Class: synthetic cationic antimicrobial (host-defence) peptide.
• Origin: analogue of bovine neutrophil indolicidin.
• Common form in literature: omiganan pentahydrochloride, studied topically (review, 2006).
• Mechanistic framing: membrane and cell-wall interaction, with lipid saturation reported as relevant (Biochimica et Biophysica Acta, 2007).
• Research domains: antibacterial, antifungal, dermatological and immunological.

This entry is definitional and summarises what researchers reported; it does not describe how any compound should be handled or administered. Peptides discussed in research literature are not interchangeable with approved therapies, and regulatory status varies by jurisdiction and product.

References

• Omiganan pentahydrochloride in the front line of clinical applications of antimicrobial peptides (Recent Patents on Anti-Infective Drug Discovery, 2006)
• Omiganan interaction with bacterial membranes and cell wall models. Assigning a biological role to saturation (Biochimica et Biophysica Acta, 2007)
• In vitro activity of omiganan pentahydrochloride tested against vancomycin-tolerant, -intermediate, and -resistant Staphylococcus aureus (Diagnostic Microbiology and Infectious Disease, 2008)
• Antimicrobial and antifungal activities of a novel cationic antimicrobial peptide, omiganan, in experimental skin colonisation models (International Journal of Antimicrobial Agents, 2009)
• Effect of omiganan on colonic anastomosis healing in a rat model of peritonitis (American Journal of Translational Research, 2017)
• Antimicrobial Peptide Omiganan Enhances Interferon Responses to Endosomal Toll-Like Receptor Ligands in Human Peripheral Blood Mononuclear Cells (Clinical and Translational Science, 2020)
• Omiganan Enhances Imiquimod-Induced Inflammatory Responses in Skin of Healthy Volunteers (Clinical and Translational Science, 2020)
• Pharmacodynamic Effects of Topical Omiganan in Patients With Mild to Moderate Atopic Dermatitis in a Randomized, Placebo-Controlled, Phase II Trial (Clinical and Translational Science, 2020)
• Anticandidal Activity of Omiganan and Its Retro Analog Alone and in Combination with Fluconazole (Probiotics and Antimicrobial Proteins, 2021)
• Liposomes encapsulating novel antimicrobial peptide Omiganan: Characterization and its pharmacodynamic evaluation in atopic dermatitis and psoriasis mice model (International Journal of Pharmaceutics, 2022)
• Omiganan-Based Synthetic Antimicrobial Peptides for the Healthcare of Infectious Endophthalmitis (ACS Biomaterials Science & Engineering, 2024)
• The Study of Antistaphylococcal Potential of Omiganan and Retro-Omiganan Under Flow Conditions (Probiotics and Antimicrobial Proteins, 2025)