The biologics have revolutionized the treatment of rheumatoid arthritis (RA). However, there are still patients that are difficult to control and a cure is still not achievable. Tofacitinib, a Janus kinase (JAK) inhibitor is an orally available, new-in-class, disease-modifying anti-rheumatic drug with similar efficacy to biologics. JAK is activated by multiple cytokines involved in the pathology of RA, and affects non-immune and immune cells, mainly the lymphocytes. Besides its anti-rheumatic effect, the recent focus has been on adverse events. As with other biologics, serious infections have been observed especially with patients with lymphopenia, consistent with the mechanism of action. The major difference in adverse events from other disease-modifying anti-rheumatic drugs is the prominent increase in the occurrence of herpes zoster; it is increased worldwide, especially in Asia. There are other concerns such as malignancies and hyperlipidemia that may cause cardiovascular events that deserve further attention. The first JAK inhibitor for RA is demonstrating great benefit along with some risk, providing insights into the post-biologic era.
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