New 1,3,4-Thiadiazole-Based Dual B-Raf/VEGFR-2 Inhibitors With Potential Anti-Breast Activity: Design, Synthesis, In Vitro and In Silico Evaluations

This study reports the design, synthesis, and biological evaluation of a novel series of 1,3,4-thiadiazole-based derivatives as dual B-Raf and VEGFR-2 kinase inhibitors with potential anticancer activity. Among the synthesized compounds, 7b emerged as the most potent candidate, exhibiting strong cytotoxicity against the MDA-MB-231 and MCF-7 breast cancer cell lines (IC₅₀ = 9.66 and 15.83 µM, respectively), with minimal toxicity toward normal WI-38 and WISH cells, reflected by favorable selectivity indices. Compound 7b, featuring a unique structural assembly of a 2,3-dihydro-1,3,4-thiadiazole core, a para-methoxyphenyl group, and a sulfonamide-linked methylpiperidine moiety, exhibited superior dual-inhibitory activity. It showed IC₅₀ values of 0.75 µM for B-Raf and 58.13 nM for VEGFR-2. Flow cytometry and gene expression analysis revealed that 7b induces G1-phase cell-cycle arrest and promotes apoptosis through the upregulation of BAX, caspases-8/9, and downregulation of Bcl-2. Compound 7b also inhibited cell migration in wound-healing assays. Structure–activity relationship (SAR) analysis indicated that para-substituted electron-donating groups enhanced cytotoxic potency. Molecular docking and molecular dynamics simulations confirmed the stable binding of 7b to the kinase active sites, supported by favorable Glide scores (–25.47 kcal/mol for VEGFR-2 and –31.64 kcal/mol) and MM-GBSA (molecular mechanics with generalized Born and surface area solvation) binding energies. Density functional theory (DFT) calculations further validated the compound's electronic stability and reactivity. These integrated findings suggest that compound 7b is a promising lead for further development as a selective dual kinase inhibitor for breast cancer therapy.