A Magnetic Resonance Imaging Study and Arthroscopic Biopsy Substudy in Subjects With Active Rheumatoid Arthritis Receiving VX-509, an Oral JAK3 Inhibitor

VX-509 is an oral, selective Janus kinase 3 (JAK3) inhibitor being developed by Vertex. In autoimmune diseases, JAK3 is an essential component of the immune signaling cascade. This cascade ultimately contributes to abnormal immune response that results in chronic inflammation and, in the case of rheumatoid arthritis (RA), irreversible damage to cartilage and bones. Selective inhibition of JAK3 offers a new disease modifying approach to the treatment of RA, and a broad range of other autoimmune diseases.