Discovery of indole- and quinolone-based inhibitors of the mTOR/Akt/Pi3K pathway for the potential treatment of autism and certain types of cancer

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that belongs to the PI3K-related protein kinase family. It is an integral part of two functionally distinct protein complexes: mTOR complex 1 and mTOR complex 2. Its signaling pathway is linked to cell survival, growth, proliferation, and motility. Deregulation of the mTOR pathway has been reported in many types of cancer. Hence, mTOR is an attractive target for the treatment of certain cancers such as renal cell carcinoma and pancreatic tumors. In addition, hyperactivity in mTOR-mediated signaling is associated with the pathogenesis of autism spectrum disorder (ASD) and Alzheimer's disease. Recently, mTOR inhibitors have been considered as emerging pharmacotherapy for these disorders. In this research, we have used molecular modeling techniques to design three series of compounds, indoles, β-carbolines, and 4-aminoquinolines, targeting the ATP site of the mTOR kinase. Based on insights from molecular docking, we developed twenty eight derivatives of these scaffolds to explore the SAR and optimize their affinities. The prepared compounds were evaluated for their inhibitory activity against mTOR as well as other closely related kinases such as PI3K and AKt. To our delight, twenty compounds have shown sub-micromolar activities towards the mTOR kinase. Compounds HA-2l and HA-2c showed a superior IC₅₀ of 66 and 75 nM, respectively, for mTOR, while being selective against AKt and Pi3K. Upon optimization, these selective inhibitors could be useful for the management of ASD due to their relatively higher safety and, hence, suitability for long-term use. On the other hand, derivatives HA-1e, HA-2g, and HA-3d exhibited high affinities for the three enzymes, suggesting their potential utility as anticancer agents. Also, the cytotoxicity of the most active compounds was assessed using different cell-lines. Compounds HA-2g, HA-2l, and HA-3d showed sub-micromolar inhibition, in the range of 0.610-0.780 μM, against the tested cancer cell lines MDA-MB231 and HCT-116. The discovery of a clinically useful mTOR inhibitor would represent a new hope for patients of two important non-communicable diseases, cancer and ASD.