JAK1 together with JAK2, JAK3, and TYK2 belong to the JAK (Janus-associated kinase) family of cytoplasmic tyrosine kinases that play important roles in cytokine and growth factor mediated signal transduction[1]. Dysregulated JAK activity leading to a constitutively activated signal transducers and activators of transcription (STAT) is strongly associated with immune-related diseases and cancers. Targeting JAK to interfere the signaling of JAK/STAT pathway has achieved quite success in the treatment of these diseases.