Cytokines are key mediators of the development and homeostasis of haematopoietic 
cells, critical for host defense, but also for the development of autoimmune and 
inflammatory diseases such as psoriasis or rheumatoid arthritis (RA). Blocking 
cytokines activity by interfering with the ligand-receptor association has been 
successfully employed to treat several immune disorders. A subgroup of cytokines 
signals through receptors requiring the association with a family of cytoplasmic 
protein tyrosine kinases known as Janus kinases (Jaks). Jaks have recently 
gained significant attention as therapeutic targets in inflammation and 
autoimmunity, and several Jak inhibitory small molecules have been developed. 
The first two Jak inhibitors, tofacitinib and ruxolitinib, have been approved 
for the treatment of RA and primary myelofibrosis, respectively. Efficacy and 
safety data suggest that some of these oral Jak inhibitors as well as their 
topical formulations may soon enter the daily clinical practice for treating 
patients with psoriasis, lupus erythematosus or other inflammatory skin 
diseases. While biologics typically target one single cytokine, these new 
immunomodulators can inhibit signals from multiple cytokines intra-cellularly 
and therefore could be useful when other therapies are ineffective. Thus, Jak 
inhibitors may replace some traditional immunosuppressive agents and help 
patients not responding to previous therapies.