Design, synthesis and antiproliferative activity of novel heterobivalent hybrids based on imidazo[2,1-b][1,3,4]thiadiazole and imidazo[2,1-b][1,3]thiazole scaffolds.

Heterobivalent ligands constituted by two different pharmacophores that bind to different molecular targets or to two distinct sites on the same molecular target could be one of the methods used for the treatment of cancer. In view of the importance of imidazo[1,2-b][1,3]thiazole and imidazo[1,2-b][1,3,4]thiadiazole as privileged structures for the preparation of novel anticancer agents, we decided to explore the synthesis and biological evaluation of molecular conjugates comprising these fused bicyclic systems tethered at their C-6 position by a meta-(α-bromoacryloylamido)phenyl moiety. We found that most of the hybrid compounds displayed high antiproliferative activity toward a wide panel of cancer cell lines, with one-digit micromolar to submicromolar 50% inhibitory concentrations (IC50). We have observed that selected compounds 7d, 7e, 7n and 8c induced apoptosis, which was associated with the release of cytochrome c and cleavage of multiple caspases. Overexpression of the protective mitochondrial protein Bcl-2 did not confer protection to cell death induced by these compounds.