Carbendazim
derivatives, commonly used as antiparasitic drugs,
have shown potential as anticancer agents due to their ability to
induce cell cycle arrest and apoptosis in human cancer cells by inhibiting
tubulin polymerization. Crystallographic structures of α/β-tubulin
multimers complexed with nocodazole and mebendazole, two carbendazim
derivatives with potent anticancer activity, highlighted the possibility
of designing compounds that occupy both benzimidazole- and colchicine-binding
sites. In addition, previous studies have demonstrated that the incorporation
of a phenoxy group at position 5/6 of carbendazim increases the antiproliferative
activity in cancer cell lines. Despite the significant progress made
in identifying new tubulin-targeting anticancer compounds, further
modifications are needed to enhance their potency and safety. In this
study, we explored the impact of modifying the phenoxy substitution
pattern on antiproliferative activity. Alchemical free energy calculations
were used to predict the binding free energy difference upon ligand
modification and define the most viable path for structure optimization.
Based on these calculations, seven compounds were synthesized and
evaluated against lung and colon cancer cell lines. Our results showed
that compound 5a, which incorporates an α-naphthyloxy
substitution, exhibits the highest antiproliferative activity against
both cancer lines (SK-LU-1 and SW620, IC50 < 100 nM)
and induces morphological changes in the cells associated with mitotic
arrest and mitotic catastrophe. Nevertheless, the tubulin polymerization
assay showed that 5a has a lower inhibitory potency than
nocodazole. Molecular dynamics simulations suggested that this low
antitubulin activity could be associated with the loss of the key
H-bond interaction with V236. This study provides insights into the
design of novel carbendazim derivatives with anticancer activity.