Janus kinases have proved to be essential for many immunological processes but 
there is growing evidence that they also play a critical role in pathogenesis of 
many diseases including inflammatory diseases and cancer where they promote 
multiple steps of tumorigenesis. Several companies are in late stage clinical 
programs for the development of JAK kinase inhibitors and the first small 
molecule JAK inhibitor, Jakafi® (ruxolitinib) has been just approved for 
treatment of myeloproliferative neoplasms. Several other molecules are on the 
rise to treat arthritis, psoriasis and multiple types of cancer. This commentary 
will provide a review of the JAK kinase field as it pertains to small molecule 
inhibition for the treatment of cancer and autoimmune diseases with an emphasis 
on JAK2. The use of experimental and clinical inhibitors of JAK will be 
discussed for solid tumor and hematological malignancies, lupus, arthritis, 
colitis, neurological disorders, pain, diabetes and cardiovascular disease. In 
addition, it will review current paradigms in the field and treatment programs 
which could be complemented by small molecule inhibitors of Janus kinase.