Tofacitinib is a Janus kinase (JAK) inhibitor. JAKs are enzymes inside your cells that help transmit signals from certain cytokines and growth factors, which are important in the immune system and blood cell formation. By blocking JAKs, tofacitinib disrupts these signals, which can reduce inflammation and abnormal immune responses.

This medication works by preventing the activation of proteins called STATs, which are involved in gene expression and immune cell function. By interfering with this pathway, tofacitinib helps to reduce the activity of the immune system, which can be helpful in diseases where the immune system is overactive, such as rheumatoid arthritis and other autoimmune conditions. However, this also means your immune system may not work as well to fight infections while you are taking this medication.

Tofacitinib

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Approved use in