JAK inhibitors

Janus kinase inhibitors, also known as JAK inhibitors.

A type of medication that functions by inhibiting the activity of one or more of the Janus kinase family of enzymes (JAK1, JAK2, JAK3, TYK2), thereby interfering with the JAK-STAT signaling pathway.

JAK inhibitors are used in the treatment of cancer and inflammatory diseases.

JAK3 inhibitors are attractive as a possible treatment of various autoimmune diseases since its functions is mainly restricted to lymphocytes.

Cytokines help to control cell growth and the immune response.

Cytokines function by binding to and activating type I and type II cytokine receptors.

Cytokine receptors rely on the Janus kinase (JAK) family of enzymes for signal transduction.

Drugs that inhibit the activity of these Janus kinases block cytokine signalling.

Janus kinases phosphorylate activated cytokine receptors, which in turn recruit STAT transcription factors which modulate gene transcription.

Tofacitinib is a specific inhibitor of JAK3, which blocks the activity of IL-2, IL-4, IL-15 and IL-21.

With Tofacitinib Th2 cell differentiation is blocked and therefore it is effective in treating allergic diseases.

Tofacitinib to a lesser extent also inhibits JAK1 and JAK2 which in turn blocks IFN-? and IL-6 signalling and consequently Th1 cell differentiation.

The blocking of Jak-dependent IL-23 reduces IL-17 and the damage it causes in psoriasis.

Ruxolitinib (trade names Jakafi/Jakavi) against JAK1/JAK2 for psoriasis, myelofibrosis, and rheumatoid arthritis.

Tofacitinib ( Xeljanz ) is a JAK3 inhibitor for psoriasis and rheumatoid arthritis.

Oclacitinib (Apoquel)-against JAK1 for the control of pruritus associated with allergic dermatitis.

Baricitinib (trade name Olumiant) against JAK1/JAK2 for rheumatoid arthritis.

Fedratinib is a JAK2 inhibitor that treats primary myelofibrosis, including in patients those previously treated with ruxolitinib, polycythemia vera and essential thrombocythemia.

Ruxolitinib inhibits both JAK1 and JK2, where as fedratinib is more specific for JAK2.

JAK2 reduces the production of blood cells.

Ruxolitinib has anti-proliferative effects, lowers counts of white blood cells, platelets and red blood cells, and reduces the size of the spleen.

Ruxolitinib is also anti-inflammatory based on combined inhibition of JAK1 and JAK2.Z

Tofacitinib for alopecia universalis.

Topical tofacitinib and ruxolitinib for alopecia.

Topical ruxolitinib for Vitiligo.

Upadactinib for rheumatoid arthritis.

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