Development of Benzoxazole Derivatives Targeting mTOR: A Promising Approach for Breast Cancer Therapy

Clinical use of mTOR inhibitors in cancer treatment is well established due to the critical role of mTOR signaling in tumor progression. In this study, we report the structure-based design and biological evaluation of a series of benzoxazole derivatives as potential mTOR inhibitors. Cytotoxicity studies using MTT assays showed that compounds B4, B11, B12, and B20 exhibited significant antiproliferative effects against breast cancer cell lines with IC₅₀ values between 4.96 and 9.82 µM. Colorimetric enzymatic assays further revealed that among these, only B12 and B20 effectively inhibited mTOR phosphorylation at Ser2448 in MCF-7 cells. Additionally, both compounds modulated the expression of key apoptotic proteins, including Bax, caspase-3, p53, and Bcl2. Molecular docking studies against the 4JT5 protein demonstrated binding affinities with docking scores ranging from −7.084 to −7.426 kcal/mol, comparable to the reference compound P2X (−7.309 kcal/mol). Molecular dynamics simulations over 150 ns confirmed the stability of B12 and B20 in the active site, with an average RMSD of 2.8 Å and 3.0 Å, respectively. The absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of the synthesized compounds were evaluated in silico. Among them, B4, B11, B12, and B20 exhibited drug-like characteristics and showed no undesirable toxic effects. These findings highlight the potential of B12 and B20 as lead compounds for the development of novel mTOR inhibitors in breast cancer therapy.