IL-17

Class

IL-17 inhibitor

Interleukin-17 (IL-17), primarily the IL-17A isoform, is a pro-inflammatory cytokine secreted mainly by a subset of T helper cells called Th17 cells, as well as by innate immune cells. It acts on epithelial cells, fibroblasts, and synovial tissue to trigger release of chemokines, antimicrobial peptides, and growth factors that recruit neutrophils and promote tissue remodeling. This signaling is a normal part of host defense against fungi and extracellular bacteria at barrier surfaces such as skin and gut, but when persistently overactive it drives chronic inflammatory diseases including plaque psoriasis, psoriatic arthritis, and axial spondyloarthritis, conditions marked by excessive keratinocyte proliferation, synovial inflammation, and new bone formation at entheses (where tendons attach to bone). Because IL-17 sits centrally in this inflammatory cascade, blocking it—either the cytokine itself or its receptor—can substantially dampen downstream tissue damage. Therapeutics targeting this pathway include monoclonal antibodies and smaller binding proteins that neutralize the cytokine, as well as molecules designed to inhibit IL-17 alongside other inflammatory mediators such as tumor necrosis factor, an approach intended to address disease processes driven by more than one cytokine simultaneously.