Targeting cytokines and signaling molecules related to immune pathways in atopic dermatitis: therapeutic implications and challenges

Although atopic dermatitis (AD) is primarily a Th2-driven disease, it shows high heterogeneity with additional variable contributions of the Th22, Th17, and Th1 pathways, depending on the subtype of the disease. Expanding knowledge and understanding of AD pathogenesis has promoted the development of numerous novel therapeutics that target cytokines and their signaling molecules, representatively, Janus kinases, involved in the underlying immune pathways, resulting in therapeutic success and failure. The first FDA approval was for the targeted biologic dupilumab. Although this proved the therapeutic relevance of targeting Th2 cytokines in moderate-to-severe forms of AD, it did not treat all patients, necessitating additional targeted therapeutics that modulate other cytokine pathways to resolve AD in all subtypes. Three more recently FDA-approved targeted therapeutics and several others that have been developed represent different targeted approaches directed to the Th2, Th22, Th17, or Th1 pathways. This review summarizes the main features and clinical outcomes of various approaches targeting cytokines and signaling molecules in these different pathways in view of both successful and failed cases, with a discussion of their therapeutic implications. In future, AD should be treated with more specific treatments reflecting the disease heterogeneity, but the current development of targeted therapeutics has faced some challenges in this context, which is also discussed.