Design, synthesis and molecular modeling of new Pyrazolyl-Benzimidazolone hybrids targeting breast Cancer

Methyl-piperidino-pyrazole (MPP) is a pyrazole derivative acting as a lead estrogen receptor (ER) antagonist and has an anti-breast cancer effect. Since some benzimidazole derivatives were reported for their inhibitory activity against breast cancer, hybrids from these reported compounds (5a-c, 6a-c, 7a-c and 8a-c) were designed to develop anti-breast cancer agents. The synthesis involved 1,3-dipolar cycloaddition of nitrilimines on the benzimidazolone derivatives 2a-b and 3a-b which occurred with chemo- and regioselectivity depending on the dipole and was confirmed by an X-ray structure of 6b. In vitro biological testing of the newly prepared compounds against the 60-cell line panel showed that 5a-c and 6a-c with a partially unsaturated pyrazole ring possessed a high GI% in the T-47D breast cancer cell line with a selectivity margin against different cell lines. Five compounds were selected for apoptotic studies in T-47D cells, of which 6a arrested cells in G1 phase and caused more apoptosis than MPP. The MTT assay revealed that compound 6a has an IC₅₀ = 6.77 ± 0.03 μM against T-47D cells. Furthermore, 6a reduced the estrogen receptor 1 gene expression levels 3-fold in T-47D cells. Molecular dynamics simulations indicated that the complex of the active compound 6a remained stable over the last 150 ns. An analysis of the binding mode revealed that compound 6a exhibited a similar conformation compared to MPP and the co-ligand in the active site of via a specific pose involving noncovalent interactions.