Tnib Tablet belongs to a group of medicines called Janus kinase inhibitors used to treat rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis. Rheumatoid arthritis is an auto-immune disease (the body's immune system attacks its tissue) which leads to joint pain and damage. Psoriatic arthritis is an inflammatory condition of the joints, often associated with psoriasis. Ulcerative colitis is an inflammatory disease of the large intestine.