The mode of action of tapinarof may not only depend on the activation of cutaneous aryl hydrocarbon receptor signaling but also on its antimicrobial activity

Management of Plaque Psoriasis in Adults: Clinical Utility of Tapinarof Cream

Topical medications represent the most commonly used drugs in the treatment of psoriasis. However, topical steroids are mainly limited to short-term or intermittent use, and traditional non-steroidal topicals such as vitamin D analogues, topical calcineurin inhibitors, and topical retinoids are limited by low efficacy and poor local skin tolerability. Tapinarof (GSK2894512, DMVT-505) is a novel, topical aryl hydrocarbon receptor (AHR) agonist, which was recently approved by the FDA for the treatment of plaque psoriasis in adults. Tapinarof acts to improve psoriasis through diminished IL-17A production by CD4+ T cells, increased barrier gene expression in keratinocytes, and reduced production of reactive oxygen species. Both short-term and long-term efficacy and safety have been evaluated in two Phase II and two Phase III (PSOARING 1 and 2) clinical trials in addition to a long-term extension study (PSOARING 3). Overall, the drug has shown beneficial effects in achieving clear skin in adults with moderate-to-severe psoriasis, good local tolerability, and also a long duration of effect even after discontinuation of the drug. Therefore, this therapy provides a new, highly effective and safe non-steroidal option to add to our psoriasis treatment toolbox for both initial clearance and long-term maintenance of disease.

Tapinarof for the treatment of psoriasis

Although topical drugs are the mainstay of treatment for patients with mild-to-moderate psoriasis, the developments observed in this field in the last two decades have been limited. The most commonly used drugs are still vitamin D analogues and corticosteroids, both with several limitations. The aryl hydrocarbon receptor (AhR) plays a role in the pathogenesis of psoriasis, and tapinarof, a novel, first-in-class, small molecule topical therapeutic AhR-modulating agent has been recently approved by the FDA for the topical treatment of plaque psoriasis in adults. Two large, 12-week, phase III trials, PSOARING 1 and 2, showed that 35.4%-40.2% of patients in the tapinarof 1% cream arm achieved the primary endpoint (Physician's Global Assessment [PGA] score of 0 or 1 and a decrease of ≥2-5 points at week 12) compared with 6.0%-6.3% for vehicle arm, respectively. The most common adverse effects were folliculitis, contact dermatitis, headache and pruritus. In the open label, 40-week, extension trial, PSOARING 3, the efficacy and safety results were similar, with 40.9% of patients achieving a PGA = 0 at least one time during the trial and 58.2% of patients with PGA≥2 achieved PGA = 0/1 at least once during the trial, without tachyphylaxis. There were no new safety signals, with most frequent adverse events being folliculitis, contact dermatitis, and upper respiratory tract infection. Tapinarof 1% cream has shown to be effective and to have a favorable safety profile in the treatment of psoriatic patients, representing an alternative to the current therapeutic options, increasing our armamentarium in the topical treatment of psoriasis.

Aryl Hydrocarbon Receptor/nuclear factor E2-related factor 2 (AHR/NRF2) Signaling: A Novel Therapeutic Target for Atopic Dermatitis

Aryl hydrocarbon receptor (AHR)/nuclear factor-erythroid 2-related factor 2 (NRF2) modulation are emerging as novel targets in the treatment of atopic dermatitis and other inflammatory skin disorders. Agonist activation of this pathway has downstream effects on epidermal barrier function, immunomodulation, oxidative stress reduction, and cutaneous microbiome modulation. Tapinarof, a dual agonist of the AHR/NRF2 signaling pathway, has shown promise in phase 2 trials for atopic dermatitis. In this review, we summarize current knowledge of the AHR/NRF2 pathway and implications in skin disease process. We also review the therapeutic potential of current AHR agonists and propose future directions to address knowledge gaps.

Aryl Hydrocarbon Receptor and Its Diverse Ligands and Functions: An Exposome Receptor

The aryl hydrocarbon receptor (AhR) is a transcriptional factor that regulates multiple functions following its activation by a variety of ligands, including xenobiotics, natural products, microbiome metabolites, and endogenous molecules. Because of this diversity, the AhR constitutes an exposome receptor. One of its main functions is to regulate several lines of defense against chemical insults and bacterial infections. Indeed, in addition to its well-established detoxication function, it has several functions at physiological barriers, and it plays a critical role in immunomodulation. The AhR is also involved in the development of several organs and their homeostatic maintenance. Its activity depends on the type of ligand and on the time frame of the receptor activation, which can be either sustained or transient, leading in some cases to opposite modes of regulations as illustrated in the regulation of different cancer pathways. The development of selective modulators and their pharmacological characterization are important areas of research. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The aryl hydrocarbon receptor at the forefront of host-microbe interactions in the skin: A perspective on current knowledge gaps and directions for future research and therapeutic applications

The skin is home to a community of skin microbiota including bacteria, viruses and fungi, which are widely accepted to be of importance for skin homeostasis but also associated with skin diseases. Detailed knowledge on the skin microbiota composition and its changes in a number of skin diseases is available. Yet, specific interactions between microbes and the host skin cells or how they communicate with each other are less well understood. To identify, understand and eventually therapeutically exploit causal relationships of microbial dysbiosis with disease, studies are required that address the receptors and mediators involved in host‐microbe interactions. In this perspective article, we provide an outlook on one of such receptors, namely the aryl hydrocarbon receptor (AHR). The AHR is well known for being a ligand‐activated transcription factor regulating the proliferation, differentiation and function of many cell types present in the skin. Its targeting by anti‐inflammatory therapeutics such as coal tar and Tapinarof is effective in atopic dermatitis and psoriasis. AHR signalling is activated upon binding of wide variety of small chemicals or ligands, including microbiota‐derived metabolites. New evidence has emerged pointing towards a key role for epidermal AHR signalling through skin microbiota‐derived metabolites. In response, AHR‐driven expression of antimicrobial peptides and stratum corneum formation may alter the skin microbiota composition. This a self‐perpetuating feedback loop calls for novel therapeutic intervention strategies for which we herein discuss the requirements in future mechanistic studies.