In Silico Inspired Design of Urea Noscapine Congeners as Anticancer Agents: Chemical Synthesis and Experimental Evaluation Using Breast Cancer Cells and a Xenograft Mouse Model

Abstract

A series of semisynthetic noscapine-urea congeners (7a-7h) as potential tubulin-binding agents are being developed by integrating a urea pharmacophore at the C-9 position of the noscapine scaffold. Their binding affinity to tubulin was predicted through molecular docking, molecular dynamics (MD) simulations, and the MM-PBSA approach. These molecules were subsequently chemically synthesized and assessed using breast cancer cell lines (MCF-7 and MDA-MB-231) and normal human embryonic kidney cells (HEK). Both the docking score and the predicted binding free energy (ΔG_bind,pred) revealed that urea congeners had a stronger affinity towards tubulin than noscapine and effectively inhibited the proliferation of all cancer cell types without affecting normal healthy cells. The results indicated that compound 7g exhibited the most promise and was chosen for further studies. Moreover, MDA-MB-231 cells treated with 7g at its IC₅₀ concentration showed morphological changes such as membrane blebbing, fragmented nuclei, and the presence of apoptotic bodies. Apoptosis induction was further confirmed by flow cytometry. Moreover, the tubulin binding assay revealed a greater binding affinity with an equilibrium dissociation constant (KD) of 42 ± 2.4 μM for compound 7g. The number of MCF-7 cells engrafted as breast tumors in nude mice was found to be reduced significantly without any adverse effects. Noscapine is already in clinical trials, but the urea noscapine congener offers an advantage because of its increased potency without impacting the nontoxic profile of noscapine.