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.