Protein kinases are enzymatic components of the signal transduction pathways, which catalyze the transfer of the terminal phosphate from ATP to the hydroxyl group of tyrosine, serine and/or threonine residues of proteins.  Thus, compounds which inhibit protein kinase functions are valuable tools for assessing the physiological consequences of protein kinase activation.  The overexpression or inappropriate expression of normal or mutant protein kinases in mammals has been a topic of extensive study and has been demonstrated to play a significant role in the development of many diseases, including diabetes, angiogenesis, psoriasis, restenosis, ocular disease, schizophrenia, rheumatoid arthritis, atherosclerosis, cardiovascular disease and cancer.  Inhibitors of protein kinases have particular utility in the treatment of human and animal disease. 
One of the principal mechanisms by which cellular regulation is effected is through the transduction of extracellular signal across the membrane that in turn modulates biochemical pathways within the cell.  Protein phosphorylation represents one course by which intracellular signals propagated from molecule to molecule resulting eventually in a cellular response.  Phosphorylation of proteins occurs predominantly at serine, threonine or tyrosine residues and protein kinases have therefore been classified by their specificity of phosphorylation sites, i.e. serine/threonine kinases and tyrosine kinases.  Because phosphorylation is such a ubiquitous process within cells, and because cellular phenotypes are largely influenced by the activity of these pathways, it is currently believed that a number of diseases states and/or disorders are a result of either aberrant activation or functional mutations in the molecular components of kinase cascades. 
Anaplastic lymphoma kinase (ALK) is a member of the receptor tyrosine kinase family, which can collect downstream protein molecules through autophosphorylation, express specific genes and modulate the growth and metabolism of cells.  Anaplastic lymphoma kinase was firstly discovered in anaplastic large cell lymphoma (ALCL).  Abnormal expression of ALK in certain ALCL comes from the ectopias of different chromosomes, the fusion proteins produced from ALK ectopia play a role of oncogene.  Such fusion proteins retain the intracellular kinase portion of ALK and fuse the N-terminal fragment of the fusion protein, resulting in high expression and over-activation of intracellular ALK kinases and causing the malignant transformation of cells.  Currently known genes which can fuse with ALK have reached 22 or more.  On the other hand, just as other members of the receptor tyrosine kinase family, ALK also can lead to over-activation of intracellular ALK kinases through gene mutations and overexpression from varieties reasons. 
So far, ALK fusion protein, ALK gene overexpression and ALK mutation have been identified in large numbers of human diseases, including tumors and cancers, such as melanoma, neuroblastoma, glioblastoma, rhabdomyosarcoma, astrocytoma, Ewing's sarcoma, retinoblastoma, anaplastic large cell lymphoma (ALCL), inflammatory myofibroblastic tumor (IMT), diffuse large B-cell lymphoma (DLBCL), non-small cell lung cancer (NSCLC), renal medullary carcinoma (RMC), renal cell carcinoma (RCC), breast cancer, colon cancer, ovarian serous carcinoma (SOC) and esophageal squamous cell carcinoma (ESCC).