Targeting non-receptor tyrosine kinases using small molecule inhibitors: an overview of recent advances

Protein tyrosine kinases are enzymes that catalyze the transfer of phosphate groups from ATP to tyrosine residues on other proteins as substrate. Phosphorylation at tyrosine residues regulates several functions, including enzyme activity, cellular localization, signal transduction and interactions between proteins. Non-receptor tyrosine kinases (nRTKs) are one of the main players in intracellular signaling pathways. Dysregulation of nRTKs leads to their constitutive activation, which might contribute to initiation or progression of cancer. Therefore, targeting dysregulated nRTKs may prevent the process of tumorigenesis. Targeted-based cancer therapy (TBCT) methods and agents or personalized medicine have emerged as the main tools for cancer treatment. Currently, several TBCT agents, including monoclonal antibodies (mAbs) and small molecules inhibitors of tyrosine kinases (TKIs) have been developed. TKIs of cytoplasmic kinases inhibit intracellular signaling pathways and interfere with tumor cell functions. In this article, the recent progresses in development of TKIs of nRTKs approved by the US Food and Drug Administration (FDA) and current promising TKIs in pre-clinical and clinical settings have been reviewed.