Receptor tyrosine kinase (RTK) plays a significant role in cellular proliferation. MAPK and PI3K-AKT-mTOR pathways are two key downstream pathways of RTK. Targeting these pathways has remained a successful approach to cause the antitumor effect. Small molecule inhibitors have been widely used for targeting different components of such pathways. Several small molecule inhibitors targeting different proteins of RTK signaling pathways are depicted in this diagram.