XELJANZ (tofacitinib) was the first FDA-approved pill of its kind (JAK inhibitor) that treats adults with moderate to severe rheumatoid arthritis, active psoriatic arthritis, active ankylosing spondylitis, and moderate to severe ulcerative colitis. XELJANZ is also approved for children ages 2 and older with active polyarticular course juvenile idiopathic arthritis and psoriatic arthritis.