1,3,4-Thiadiazoles are known to exhibit a wide array of biological activities such as diuretic, antifungal, anticonvulsant and anticancer properties. Since 1,3,4-thiadiazoles are structurally considered as bio-isosteres of pyrimidine, this structural framework along with its capability to bind to various biological targets has led to the development of many FDA approved drugs. The current work focuses on the identification of an initial hit from an existing library of thiadiazoles and its optimization to a potential lead molecule. The compounds were evaluated for in-vitro cytotoxicity in four human cancer cell lines namely HepG2, MCF7, HCT116 and A549 as well as in Vero cell lines. Four compounds 11h-11k showed potency comparable with or better than the positive control Erlotinib and exemplary selectivity towards normal cells. These compounds were then screened to assess their inhibitory potential in wild type and mutated EGFR (T790M). Compound 11j was found to be potent in these assays. Further computational approach driven SAR around this compound led to the identification of a more potent compound 14h that showed sub-micromolar potency in wild type EGFR with much improved potency against T790M. Apoptotic effect of 14h was investigated using annexin V-FITC/PI dual staining assay in which 14h was found to trigger apoptotic pathways effectively with a significantly higher proportion of cells undergoing both early and late apoptotic events, underscoring its potential as a therapeutic agent targeting programmed cell death. Western blot analysis of 14h indicates that it primarily impairs EGFR phosphorylation, supporting its potential as a targeted modulator of EGFR signalling.
