説明
In November 2012, the US FDA approved tofacitinib (also referred to as
CP-690550) for the treatment of adult patients with moderate to severely
active rheumatoid arthritis (RA) who have had an inadequate response or
intolerance to methotrexate. Tofacitinib is the first small molecule kinase inhibitor approved for the treatment of RA. Tofacitinib is an inhibitor of the four subtypes of Janus kinase (JAK): JAK1, JAK2, JAK3, and Tyk2. The JAKs are intracellular, nonreceptor tyrosine kinases that play important roles in the signal transduction pathway of many cytokines (e.g., interleukins 2, 4, 7, 9, 15, and 21) and are involved in the propagation of inflammation in RA. Tofacitinib acts by inhibiting the phosphorylation and activation of signal transducers and activators of transcription (STATs), thereby suppressing the production of inflammatory mediators in joint tissue. At the enzyme level, tofacitinib inhibits JAKs 1, 2, 3, and Tyk2 with IC50s of 3.2, 4.1, 1.6, and 34 nM, respectively. At the cellular level, tofacitinib inhibits the in vitro activities of JAK1/JAK2, JAK1/JAK3, and JAK2/JAK2 combinations with IC50s of 406, 56, and 1377 nM, respectively.
適応症
The JAK family includes four isoforms, JAK1, JAK2, JAK3, and tyrosine kinase (TYK2). Ruxolitinib (Jakafi(R), Incyte Corp.) was the first approved JAK inhibitor, which inhibits both JAK1 and JAK2, used for the treatment of different types of myelofibrosis. Tofacitinib (Xeljanz(R), Pfizer) was approved by FDA as a JAK3-selective inhibitor for the treatment of rheumatoid arthritis and is one of the only two FDA-approved kinase inhibitors for non-oncological indications.
