RECENT FINDINGS: New drugs that are designed to inhibit steps in this pathway, the IL12/IL23 inhibitor, ustekinumab, the IL17A inhibitors secukinumab and ixekizumab, the IL17A receptor inhibitor, brodalumab, and the IL23 inhibitors guselkumab and tildrakizumab, have demonstrated significant effectiveness in treating these diseases, particularly psoriasis, psoriatic arthritis and ankylosing spondylitis.