Development of PI3K inhibitors: Advances in clinical trials and new strategies (Review)

Phosphatidylinositol 3-kinases (PI3Ks) are the family of vital lipid kinases widely distributed in mammalian cells. The overexpression of PI3Ks leads to hyperactivation of the PI3K/AKT/mTOR pathway, which is considered a pivotal pathway in the occurrence and development of tumors. Hence, PI3Ks are viewed as promising therapeutic targets for anti-cancer therapy. To date, some PI3K inhibitors have achieved desired therapeutic effect via inhibiting the activity of PI3Ks or reducing the level of PI3Ks in clinical trials, among which, Idelalisib, Alpelisib and Duvelisib have been approved by the FDA for treatment of ER+/HER2- advanced metastatic breast cancer and refractory chronic lymphocytic leukemia (CLL) and small lymphocytic lymphomas (SLL). This review focuses on the latest advances of PI3K inhibitors with efficacious anticancer activity, which are classified into Pan-PI3K inhibitors, isoform-specific PI3K inhibitors and dual PI3K/mTOR inhibitors based on the isoform affinity. Their corresponding structure characteristics and structures-activity relationship (SAR), together with the progress in the clinical application are mainly discussed. Additionally, the new PI3K inhibitory strategy, such as PI3K degradation agent, for the design of potential PI3K candidates to overcome drug resistance is referred as well.