IL17A and psoriasis: IL-17 is a key mediator in the development of psoriasis, and IL-17 inhibitors can treat psoriasis by binding to its ligands or receptors to block the IL-17 pathway.30 To date, three biologic agents targeting the IL-17 cytokine pathway have been approved to treat psoriasis by the FDA, and they include two monoclonal antibodies against interleukin-17A with high affinity, secukinumab and ixekizumab.