Design, synthesis and anticancer activity of novel 2-arylbenzimidazole/2-thiopyrimidines and 2-thioquinazolin-4(3H)-ones conjugates as targeted RAF and VEGFR-2 kinases inhibitors

Abstract

In the current study, series of 2-arylbenzimidazole-thiopyrimidine and -thioquinazolin-4(3H)-ones conjugates 12a-d, 13a,b and 14a-l have been synthesized. All the synthesized compounds were tested in vitro for their anticancer activities against a panel of cancer cell lines at NCI - US and their growth inhibition (GI) % were determined at 10 µM. Compounds 14c and 14g-i were selected to be screened at the five dose assay and were found to exhibit GI₅₀ values 1.1-30.0 µM. The benzimidazole-quinazolinone derivative 14c, in particular, showed potent anticancer activity against the tested cancer cell lines (GI₅₀ of 1.3-4.2 µM). In addition, compounds 12a,b, 13a, 14a-e, 14g, 14i and 14j were selected to be tested against some cancer cell lines using MTT assay and the benzimidazole-quinazolinone 14g was found to have potent anticancer activities against melanoma (Mel-501 and A-375), breast (MCF-7), colon (HCT-116), prostate (PC-3), lung (A-549) and pancreas (Paca-2) cancer cell lines reporting IC₅₀ values ranging between 0.1 and 6.2 µM. Moreover, the synthesized hybrids were tested in vitro on kinases; BRAF (wt), BRAF (V600E), CRAF and VEGFR-2. The benzimidazole-quinazolinone derivatives 14f,g revealed potent RAF kinases inhibitory activities on BRAF (wt), BRAF (V600E) and CRAF showing IC₅₀ values 0.002-0.1 µM, whereas, the benzimidazole-quinazolinone derivatives 14i and 14k showed moderate VEGFR-2 inhibitory activity (IC₅₀ = 20.60 and 6.14 µM, respectively). Moreover, the representative compounds 14g and 14i caused cell cycle arrest of A-375 melanoma cell line at G2/M phase and were found to induce late apoptosis. CRAF in the DFG-out inactive conformation homology modeling was first reported in this study and molecular docking studies on BRAF, CRAF and VEGFR-2 were also performed to investigate the binding modes of the target compounds and their interactions with the key amino acids; BRAF (Glu500, Cys531 and Asp593), CRAF (Glu393, Cys424 and Asp486) and VEGFR-2 (Glu885, Cys919 and Asp1046).

Keywords: 2-Arylbenzimidazoles; Anticancer evaluation; Molecular docking; RAF/VEGFR-2 kinase inhbitors.