Omiganan Enhances Imiquimod‐Induced Inflammatory Responses in Skin of Healthy Volunteers

Abstract

Omiganan (OMN; a synthetic cationic peptide) and imiquimod (IMQ; a TLR7 agonist) have synergistic effects on interferon responses in vitro. The objective of this study was to translate this to a human model for proof-of-concept, and to explore the potential of OMN add-on treatment for viral skin diseases. Sixteen healthy volunteers received topical IMQ, OMN, or a combination of both for up to 4 days on tape-stripped skin. Skin inflammation was quantified by laser speckle contrast imaging and 2D photography, and molecular and cellular responses were analyzed in biopsies. IMQ treatment induced an inflammatory response of the skin. Co-treatment with OMN enhanced this inflammatory response to IMQ, with increases in perfusion (+17.1%; 95% confidence interval (CI) 5.6%-30%; P < 0.01) and erythema (+1.5; 95% CI 0.25%-2.83; P = 0.02). Interferon regulatory factor-driven and NFκBdriven responses following TLR7 stimulation were enhanced by OMN (increases in IL-6, IL-10, MXA, and IFNɣ), and more immune cell infiltration was observed (in particular CD4+, CD8+, and CD14+ cells). These findings are in line with the earlier mechanistic in vitro data, and support evaluation of imiquimod/OMN combination therapy in human papillomavirus-induced skin diseases.Cathelicidins are a family of antimicrobial (cationic) peptides that play an important role in the first line immune defense of the skin, related to their broad antimicrobial activity against bacteria, viruses, and fungi. 1 LL-37 is the only human member of the cathelicidin family. 1 Besides its antimicrobial effects, this peptide also has direct immunomodulatory activity. LL-37 affects the response of neutrophils to viruses, and modulates interferon (IFN) responses induced by viral triggers. 2 LL-37 converts self-RNA into a ligand for toll-like receptor (TLR)7 and TLR8 in human dendritic cells, thereby enhancing IFNα production in human skin. 3 Omiganan (OMN) is a synthetic indolicidin (a cathelicidin isolated from bovine neutrophils), currently under development as topical gel for several clinical indications. OMN is known to have activity against a wide variety of microorganisms, such as gram-positive and gramnegative bacteria and fungi. 4,5 Moreover, OMN enhances IFN responses induced by TLR3 (Poly:IC), TLR7 (imiquimod (IMQ)), TLR8 (ssRNA), and TLR9 (CpG) in human immune cells, comparable but not similar to the effects observed for Grievink et al.). These observations support the future application of OMN

Intradermal lipopolysaccharide challenge as an acute in vivo inflammatory model in healthy volunteers

“…Skin punch biopsies (3 mm) were collected after local anaesthesia and immediately snap frozen using liquid nitrogen as previously described 16 . The biopsies were stored at −80°C until analysis.…”

“…Skin punch biopsies (3 mm) were collected after local anaesthesia and immediately snap frozen using liquid nitrogen as previously described. 16 The biopsies were stored at −80°C until analysis. Immunohistochemistry was performed for the following targets: CD1a dendritic cells (Clone EP3622; Cell Marque Sigma‐Aldrich); CD4 T cells (Clone SP35; Ventana, Roche Diagnostics, Rotkreuz, Switzerland); CD8 T cells (Clone SP57; Ventana, Roche Diagnostics); CD14 monocytes (Clone EPR3653; Cell Marque Sigma‐Aldrich); CD19 B cells (clone LE‐CD19; Thermo Fischer Scientific) and myeloperoxidase (MPO) neutrophils (polyclonal 760–2659; Cell Marque Sigma‐Aldrich).…”

“…Skin punch biopsies (3 mm) were collected after local anaesthesia and immediately snap frozen using liquid nitrogen as previously described. 16 The biopsies were stored at À80 C until analysis. Immunohistochemistry was performed for the following targets: The slides were scored qualitatively on a 6-point scale (negative, minimal, few, moderate, many or excessive) by a blinded dermatopathologist.…”

Pharmacodynamic Effects of Topical Omiganan in Patients With Mild to Moderate Atopic Dermatitis in a Randomized, Placebo‐Controlled, Phase II Trial

“…The final set of markers was chosen based on disease involvement (IL-31, eotaxin, interferon-gamma (IFN-γ)) and expected investigational drug effects (IFN-α, IFN-γ, and IL-6). 18 Safety and tolerability Safety and tolerability end points were assessed by frequency of treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), discontinuations due to AEs or deaths, laboratory values (hematology, chemistry, coagulation, and urinalysis), vital signs, electrocardiographic parameters, and physical examination.…”

Blueprint for mechanistic, data‐rich early phase clinical pharmacology studies in dermatology

“…Given the fact that most dermatological drugs have an immunomodulatory mechanism of action, translational models are of particular interest for human pharmacology. Such studies include in vivo or ex vivo immune challenges targeting innate immunity pathways, e.g., lipopolysaccharide for Toll‐like receptor (TLR)‐4 and imiquimod for TLR‐7 stimulation, or adaptive pathways, e.g., the neoantigen keyhole limpet hemocyanin driving an antigen‐specific T‐cell and B‐cell response 15,16 . Other valuable models include histamine or capsaicin challenges via skin prick, as model for pruritus as was reviewed by Assil et al 17 Combining a dose‐ranging trial with a proof‐of‐pharmacology trial at the earliest clinical stage (i.e., in healthy volunteers) results in proving the pharmacological action and supports rational dose selection for a subsequent “proof‐of‐concept” trial in a relevant patient population.…”