Design and synthesis of thiadiazolo-carboxamide bridged β-carboline-indole hybrids: DNA intercalative topo-IIα inhibition with promising antiproliferative activity

[Display omitted] •Compound 12c displayed superlative cytotoxicity in the cancer cell lines.•Selectivity index of 12c is in the range of 14.90–25.26.•Compound 12c along with 12a inhibited topoisomerase IIα and interacted with DNA via intercalative mode of binding.•Compound 12c induced apoptosis in A549 lung cancer cell line.•In silico and in vitro evaluation established the cytotoxic potential of compound 12c. The conjoining of salient pharmacophoric properties directing the development of prominent cytotoxic agents was executed by constructing thiadiazolo-carboxamide bridged β-carboline-indole hybrids. On the evaluation of in vitro cytotoxic potential, 12c exhibited prodigious cytotoxicity among the synthesized new molecules 12a–k, with an IC50