Design, synthesis and evaluation of novel oxadiazole-based compounds as potential Rac1 inhibitors against breast...

In this study, a series of novel small molecule Rac1 inhibitors were rationally designed and synthesized by targeting key pharmacophore features associated with its hydrophobic pocket. Structural confirmation of the compounds was achieved through spectral analysis, and their cytotoxic effects were evaluated using MTT test on breast cancer and healthy breast epithelial cell lines. Cytotoxicity screening revealed six compounds as the most active and selective, with IC₅₀ values ranging from 9 to 19 μM and selectivity indexes greater than 2.9 based on the MTT assay. Further evaluation using a Rac1 inhibition assay demonstrated that two compounds bearing 2-fluorophenyl and 4-methylphenyl substituents exhibited the strongest inhibitory effects, with 81 % and 78 % inhibition at 19 μM and 12 μM, respectively, whereas NSC23766, a reported selective Rac1 inhibitor, showed 82 % activity at 100 μM. At their IC₅₀ concentrations, both compounds induced apoptosis in MCF-7 cells. A structure-activity relationship analysis was conducted to elucidate the correlation between specific structural modifications and biological activity. The strong agreement between docking scores and biological assay data supports the conclusion that these two compounds act as potent inhibitors of Rac1-GEF interaction, thereby interfering with Rac1-mediated oncogenic signaling. Given their strong in vitro activity and favorable selectivity, these compounds are proposed as promising hit candidates for further in vivo studies to evaluate their therapeutic potential and safety profiles.