Affecting nearly 1.5 million adults, rheumatoid arthritis is an inflammatory disease that causes pain, swelling, stiffness, and loss of function in the joints. It occurs when the immune system, which normally defends the body from outside invaders such as bacteria and viruses, attacks the membrane that lines the joints.
Tofacitinib is from a new class of drugs developed to target Janus kinases. One member of this family, JAK3, was discovered in the early 1990s by a National Institutes of Health laboratory in the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Subsequent studies carried out at the National Heart, Lung, and Blood Institute (NHLBI), in collaboration with the NIAMS, showed that genetic defects in JAK3 can cause severe combined immunodeficiency. This discovery led to the idea that drugs blocking Janus kinases would suppress the immune system and might be protective against the damaging inflammation of rheumatoid arthritis and certain other autoimmune diseases.
The approval of tofacitinib represents the first time in a decade that the FDA has approved an oral disease modifying antirheumatic drug, or DMARD, for the treatment of rheumatoid arthritis. This broad class of drugs slows or halts the progression of damage from the disease, rather than merely providing relief from symptoms. Unlike biologic treatments for rheumatoid arthritis — which are also DMARDs and target immune system proteins — tofacitinib is a pill, not an infusion or an injection. It is the first Janus kinase inhibitor to receive an FDA approval for rheumatoid arthritis.