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Imiquimod (IMQ) is a topical agent that induces local inflammation via the Toll-like receptor 7 pathway. Recently, an IMQ-driven skin inflammation model was developed in healthy volunteers for proof-of-pharmacology trials. The aim of this study was to profile the cellular, biochemical, and clinical effects of the marketed anti-inflammatory compound prednisolone in an IMQ model. This randomized, double-blind, placebo-controlled study was conducted in 24 healthy volunteers. Oral prednisolone (0.25 mg/kg/dose) or placebo (1:1) was administered twice daily for 6 consecutive days. Two days after treatment initiation with prednisolone or placebo, 5 mg imiquimod (IMQ) once daily for two following days was applied under occlusion on the tape-stripped skin of the back for 48 h in healthy volunteers. Non-invasive (imaging and biophysical) and invasive (skin punch biopsies and blister induction) assessments were performed, as well as IMQ ex vivo stimulation of whole blood. Prednisolone reduced blood perfusion and skin erythema following 48 h of IMQ application (95% CI [-26.4%, -4.3%], p = 0.0111 and 95% CI [-7.96, -2.13], p = 0.0016). Oral prednisolone suppressed the IMQ-elevated total cell count (95% CI [-79.7%, -16.3%], p = 0.0165), NK and dendritic cells (95% CI [-68.7%, -5.2%], p = 0.0333, 95% CI [-76.9%, -13.9%], p = 0.0184), and classical monocytes (95% CI [-76.7%, -26.6%], p = 0.0043) in blister fluid. Notably, TNF, IL-6, IL-8, and Mx-A responses in blister exudate were also reduced by prednisolone compared to placebo. Oral prednisolone suppresses IMQ-induced skin inflammation, which underlines the value of this cutaneous challenge model in clinical pharmacology studies of novel anti-inflammatory compounds. In these studies, prednisolone can be used as a benchmark., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Assil, Buters, Hameeteman, Hallard, Treijtel, Niemeyer – Van der Kolk, de Kam, Florencia, Prens, van Doorn, Rissmann, Klarenbeek, Jansen and Moerland.)

Development of pharmacological interventions for wound treatment is challenging due to both poorly understood wound healing mechanisms and heterogeneous patient populations. A standardized and well-characterized wound healing model in healthy volunteers is needed to aid in-depth pharmacodynamic and efficacy assessments of novel compounds. The current study aims to objectively and comprehensively characterize skin punch biopsy-induced wounds in healthy volunteers with an integrated, multimodal test battery. Eighteen (18) healthy male and female volunteers received three biopsies on the lower back, which were left to heal without intervention. The wound healing process was characterized using a battery of multimodal, non-invasive methods as well as histology and qPCR analysis in re-excised skin punch biopsies. Biophysical and clinical imaging read-outs returned to baseline values in 28 days. Optical coherence tomography detected cutaneous differences throughout the wound healing progression. qPCR analysis showed involvement of proteins, quantified as mRNA fold increase, in one or more healing phases. All modalities used in the study were able to detect differences over time. Using multidimensional data visualization, we were able to create a distinction between wound healing phases. Clinical and histopathological scoring were concordant with non-invasive imaging read-outs. This well-characterized wound healing model in healthy volunteers will be a valuable tool for the standardized testing of novel wound healing treatments., (© 2023 The Authors. Experimental Dermatology published by John Wiley & Sons Ltd.)

A follow-up study was performed in 12 healthy women to evaluate systemic exposure to aluminium following topical application of a representative antiperspirant formulation under real-life use conditions (part A) and to assess the local fate of topically applied aluminium by taking additional tape strips and skin biopsies (Part B). A simple roll-on formulation, containing the maximal possible radioactive dose, was prepared with [ 26 Al] aluminium-labeled chlorohydrate (ACH). The microtracer of [ 26 Al] was used to distinguish aluminium from the natural background, using accelerator mass spectrometry. [ 26 Al] aluminiumcitrate was administered intravenously to estimate the dermal fraction absorbed. Despite the 25-fold increase of the topical dose compared with the previous study, only 12 blood samples gave results above the lower limit of quantitation (0.118 fg/mL). The most reliable estimates of the dermal fraction absorbed are derived from noncompartmental analysis with the urine data. By using the intravenous dose to normalize the urinary excretion to 100% bioavailability, the best estimate of the fraction absorbed of [ 26 Al] from a topical application of [ 26 Al]-aluminium-labeled chlorohydrate in an antiperspirant formulation was 0.00052%. Part B of the study demonstrated that the majority of the aluminium in the formulation remained associated with the external layers of the skin without penetration through the skin., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Dysbiosis and colonization with Staphylococcus aureus is considered to play an important role in the pathogenesis of atopic dermatitis (AD). Recovering this dysbiosis may improve AD symptoms. Omiganan is a synthetic indolicidin analogue antimicrobial peptide with activity against S aureus and could be a viable new treatment option for AD., Objective: To explore the tolerability, clinical efficacy, and pharmacodynamics of omiganan in mild to moderate AD., Methods: Eighty patients were randomized to omiganan 1%, 1.75%, or 2.5% or vehicle twice daily for 28 days on all lesions. Weekly visits included clinical scores and microbiological and pharmacodynamic assessments of 1 target lesion., Results: In all omiganan treatment groups, dysbiosis was recovered by reducing Staphylococcus species abundance and increasing diversity. A reduction of cultured S aureus was observed in all omiganan treatment groups, with a significant reduction for omiganan 2.5% compared to vehicle (-93.5%; 95% CI, -99.2 to -28.5%; P = .02). No significant clinical improvement was observed., Conclusion: Topical administration of omiganan twice daily for up to 28 days in patients with mild to moderate AD led to a recovery of dysbiosis but without clinical improvement. Therefore, a monotreatment that selectively targets the microbiome does not appear to be a successful treatment strategy in mild to moderate AD., (Copyright © 2020. Published by Elsevier Inc.)

The intradermal lipopolysaccharide (LPS) challenge in healthy volunteers has proven to be a valuable tool to study local inflammation in vivo. In the current study the inhibitory effects of oral and topical corticosteroid treatment on intradermal LPS responses were evaluated to benchmark the challenge for future investigational drugs. Twenty-four healthy male volunteers received a two-and-a-half-day twice daily (b.i.d.) pretreatment with topical clobetasol propionate 0.05% and six healthy volunteers received a two-and-a-half-day b.i.d. pretreatment with oral prednisolone at 0.25 mg/kg body weight per administration. Participants received one injection regimen of either 0, 2, or 4 intradermal LPS injections (5 ng LPS in 50 µL 0.9% sodium chloride solution). The LPS response was evaluated by noninvasive (perfusion, skin temperature, and erythema) and invasive assessments (cellular and cytokine responses) in suction blister exudate. Both corticosteroids significantly suppressed the clinical inflammatory response (erythema P = 0.0001 for clobetasol and P = 0.0016 for prednisolone; heat P = 0.0245 for clobetasol, perfusion P < 0.0001 for clobetasol and P = 0.0036 for prednisolone). Clobetasol also significantly reduced the number of monocytes subsets, dendritic cells, natural killer cells, and T cells in blister exudate. A similar effect was observed for prednisolone. No relevant corticosteroid effects were observed on the cytokine response to LPS. We successfully demonstrated that the anti-inflammatory effects of corticosteroids can be detected using our intradermal LPS challenge model, validating it for evaluation of future investigational drugs, as an initial assessment of the anti-inflammatory effects of such compounds in a minimally invasive manner., (© 2021 The Authors. Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Aims: Whereas intravenous administration of Toll-like receptor 4 ligand lipopolysaccharide (LPS) to human volunteers is frequently used in clinical pharmacology studies, systemic use of LPS has practical limitations. We aimed to characterize the intradermal LPS response in healthy volunteers, and as such qualify the method as local inflammation model for clinical pharmacology studies., Methods: Eighteen healthy male volunteers received 2 or 4 intradermal 5 ng LPS injections and 1 saline injection on the forearms. The LPS response was evaluated by noninvasive (perfusion, skin temperature and erythema) and invasive assessments (cellular and cytokine responses) in skin biopsy and blister exudate., Results: LPS elicited a visible response and returned to baseline at 48 hours. Erythema, perfusion and temperature were statistically significant (P < .0001) over a 24-hour time course compared to saline. The protein response was dominated by an acute interleukin (IL)-6, IL-8 and tumour necrosis factor response followed by IL-1β, IL-10 and interferon-γ. The cellular response consisted of an acute neutrophil influx followed by different monocyte subsets and dendritic cells., Discussion: Intradermal LPS administration in humans causes an acute, localized and transient inflammatory reaction that is well-tolerated by healthy volunteers. This may be a valuable inflammation model for evaluating the pharmacological activity of anti-inflammatory investigational compounds in proof of pharmacology studies., (© 2021 The Authors. British Journal of Clinical Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.)

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 NFκB-driven 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., (© 2020 The Authors. Clinical and Translational Science published by Wiley Periodicals, Inc. on behalf of the American Society for Clinical Pharmacology and Therapeutics.)