Interleukin-17 Inhibitors

The cytokine interleukin (IL)-17 is mainly produced by T-helper 17 cells and to a lesser extent by other innate immune cells. IL-17A is a homodimeric glycoprotein with varying homology with other family members, ranging from 55% for IL-17F to 17% for IL-17E. IL-17 cytokines act via their receptor family, which is distinct from other known cytokine receptors. The IL-17 receptor family contains 5 subunits, each of which contains an extracellular domain, single transmembrane domain and a signalling adaptor protein. The IL-17A inhibitors currently used in dermatology can be divided into two groups: Monoclonal antibodies targeting IL-17A and monoclonal antibodies targeting IL-17RA. IL-17A inhibitors are also licensed for treatment of psoriatic arthritis and ankylosing spondylitis. They have been used off-label for several recalcitrant skin diseases. IL-17 inhibitors do not appear to play a significant downregulatory role in systemic immunity compared with tumour necrosis factor antagonists.