BACKGROUND: JAK/STAT signal pathway, a requisite part in the signaling process 
of growth factors and cytokines, has become attractive targets for numerous 
immune, inflammatory and hematopoietic diseases.
OBJECTIVE: Herein, we present a review of the JAK/STAT signal pathway, the 
structure, biological function, mechanism of the JAKs and STATs along with a 
summary of the up-to-date clinical or approved JAK inhibitors which are involved 
in the treatment of various kinds of tumors and other immunity indications. 
Moreover, kinds of recently discovered JAKs inhibitors with potent activity or 
promising selectivity are also briefly discussed.
CONCLUSION: Research and development of isoform selective JAK inhibitors has 
become a hot topic in this field. With the assistance of high throughput 
screening and rational drug design, more and more JAK inhibitors with improved 
selective profiles will be discovered as biological probes and even therapeutic 
agents.