Therapeutic pipeline for atopic dermatitis: End of the drought?
Until the past year, our therapeutic armamentarium for treating atopic dermatitis (AD) was still primarily topical corticosteroids and, for more severe disease, systemic immunosuppressants. The pipeline of more targeted topical and systemic therapies is expanding based on our growing understanding of the mechanism for AD and is particularly focused on suppressing the skewed immune activation. Most agents are in phase 2 clinical trials. Crisaborole, a topical phosphodiesterase 4 (PDE4) inhibitor, became available in late 2016 in the United States for mild-to-moderate AD, with other PDE4 inhibitors, an agonist of the aryl hydrocarbon receptor, Janus kinase inhibitors, and commensal organisms also in trials for topical application. The first highly effective mAb for AD, dupilumab, targets the IL-4/IL-13 receptor and was approved in early 2017 in the United States for moderate-to-severe adult AD. Other biologics similarly inhibit TH2 cytokines (thymic stromal lymphopoietin, IL-4, IL-5, IL-13, and the itch-specific cytokine IL-31 and their receptors) or TH22/TH17 cytokines, levels of which are increased in lesional skin. Orally administered small-molecule inhibitors that suppress inflammation (targeting chemoattractant receptor–homologous molecules expressed on TH2 lymphocytes, PDE4, the histamine 4 receptor, and Janus kinase) or specifically itching (eg, NK1R inhibitors) are also being studied. Comparing biomarkers with individual responses to experimental agents will help to determine subphenotypes within AD that predict prognosis and treatment responses.