Design and synthesis of 1‑sec/tert‑butyl-2-chloro/nitrophenylbenzimidazole derivatives: Molecular docking and in vitro evaluation against MDA-MB-231 and MCF-7 cell lines

Abstract

Breast cancer is the most common type of cancer among women and the increasing cases of drug resistance pose a great challenge in the development of new anticancer drugs. Benzimidazole derivatives containing various functional groups have been reported to exhibit excellent anticancer activity. Previous studies revealed that some of the synthesized 2‑chloro/nitrophenylbenzimidazole derivatives showed unexpected selective inhibition towards MDA-MB-231. In continuing efforts toward the development of a more selective anticancer drug, two series of N-sec and tert-butyl-2-phenylbenzimidazoles were designed and synthesized by substitution of chloro‑ and nitro- groups at various positions of the phenyl group. The derivatives were characterized by 1H NMR, 13C NMR, and mass spectrometry. The antiproliferative activity of the synthesized compounds was evaluated against MDA-MB-231 and MCF-7. In both cell lines, chloro‑substituted benzimidazoles generally showed better inhibitory effect compared to those with nitro-substituent. The most potent compound was 4b3 (IC50 = 54.62 µM for MCF-7), and the most potent derivative on MDA-MB-231 cells was 4a7 (IC50 = 62.3 µM). ortho-Chloro-substituted derivatives 4a7 and 4b1 exhibited good selectivity towards MDA-MB-231 cells, although the additional chloro‑substituent and the presence of the less bulky sec-butyl group in 4a7 slightly increased its selectivity. Benzimidazoles 4b6, 4b8, 4b9, and 4b10 were found to show selectivity towards the estrogen receptor-positive cell line, MCF-7, and inactive against the MDA-MB-231 cell line. Molecular dockings of 4a7 and 4b3 in the Epidermal Growth Factor Receptor (EGFR) (PDB ID: 1M17) active sites showed similar binding poses, while gefitinib bound slightly further inside the binding sites.