Design, synthesis and biological evaluation of novel 9-methyl-9H-purine and thieno[3, 2-d]pyrimidine derivatives as potent mTOR inhibitors.

The mammalian target of rapamycin (mTOR) has been proved to be an effective target for cancer therapy. Two kinds of mTOR inhibitors, the rapalogs and mTOR kinase inhibitors (TORKi), have been developed and clinically validated in several types of malignancies. Compared with rapalogs, TORKi can exert better antitumor activity by inhibiting both mTORC1 and mTORC2, but the clinical development of current TORKi candidates has been relative slow, more TORKi with novel scaffold need to be developed to expand the current pipelines. In this study, a series of 9-methyl-9H-purine and thieno[3, 2-d]pyrimidine derivatives were designed, synthesized and biological evaluation. Most of these compounds exhibited good mTOR kinase inhibitory activity and selectivity over PI3Kα. Subsequent antiproliferative assay allowed us to identify the lead compound 15i, which display nanomolar to low micromolar IC50s against six human cancer cell lines. 15i could induce cell cycle arrest of MCF-7, PC-3 and A549 cells at the G0/G1 phase and suppress the migration and invasion of these cancer cells by suppressing the phosphorylation of AKT and P70S6 kinase. It could also regulate autophagy-related proteins to induce autophagy. Therefore, 15i would be a starting point for the development of new TORKi as anticancer drug.

Identification of a selective BRD4 PROTAC with potent antiproliferative effects in AR-positive prostate cancer based on a dual BET/PLK1 inhibitor.

BRD4-targeted proteolysis targeting chimera (PROTAC) have exhibited promising in vitro and in vivo anticancer activity in a number of cancer models. However, the clinical development of current reported BRD4-PROTACs have stagnated, largely due to the safety risks caused by their poor degradation selectivity. In this study, we designed and synthesized a series of PROTACs based on our recently reported dual BET/PLK1 inhibitor WNY0824, which led to the discovery of an isoform-selective and potent BRD4-PROTAC 12a (WWL0245). WWL0245 exhibited excellent selective cytotoxicity in the BETi sensitive cancer cell lines, including AR-positive prostate cancer cell lines. It could also efficiently induce ubiquitin-proteasomal degradation of BRD4 in AR-positive prostate cancer cell lines, with sub-nanomolar half-maximal degrading concentration (DC50) and maximum degradation (Dmax) > 99%. Moreover, WWL0245 induced cell cycle arrest at the G0/G1 phase and apoptosis in AR-positive prostate cancer by downregulation of the protein levels of AR, PSA and c-Myc as well as transcriptionally suppressed AR-regulated genes. WWL0245 was thus expected to be developed as a promising drug candidate for AR-positive prostate cancer and a valuable tool compound to study the biological function of BRD4.