JAK (Janus Kinase Pathway) Inhibitor Tofacitinib – pharmacology, mechanism of action, side effects

Tofacitinib is an oral agent taken twice daily used to treat many rheumatological conditions mainly RA. Tofacitinib inhibits Janus kinase (JAK) signalling. Immune cells such as macrophages, monocytes and T cells play a key role in the pathophysiology of RA. They contain receptors on their surface which rely on the JAK. JAK initiates a cascade of intracellular phosphorylation events leading to the activation of transcription factor STAT. In rheumatological disease JAK-STAT signalling pathway is involved in the transcription of immune cells which promote inflammatory response.