Synthesis and Biological Evaluation of Indazole Ring Containing Diaryl Urea Derivatives Inducing Activities in Human Breast Cancer MCF-7 Cells

Abstract

In this study, a series of twelve novel indazole-diaryl urea hybrids (R₁-R₁₂) was designed, synthesised and structurally characterised with the aim of developing new breast cancer therapeutics. The synthetic strategy employed a multistep route starting from 5-bromo-1H-indazole and afforded the desired derivatives in good yields. The chemical structures of all final products were confirmed using ¹H and ¹³C NMR spectroscopy, FTIR and mass spectrometry, ensuring high purity and structural integrity. In vitro cytotoxic activity was assessed against the MCF-7 human breast cancer cell line using the MTT assay. Among the synthesised molecules, compounds R₇, R₈ and R₁₁ emerged as the most active, with IC₅₀ values of 13.15, 12.71 and 11.48 µM, respectively. Notably, these values represent a significant improvement compared to the reference drug sorafenib (IC₅₀ = 29.3 µM). Structure–activity relationship (SAR) analysis suggested that electron-withdrawing substituents such as fluorine and chlorine, as well as di-substituted aromatic rings, enhanced cytotoxic potency. Molecular docking studies were performed on the histone deacetylase crystal structure (HDAC, PDB ID: 4LXZ) to provide structural insights into binding affinity. The most potent compounds displayed favourable docking scores (R₇ = -10.1 kcal/mol and R₁₁ = -9.5 kcal/mol) and established key hydrogen bonding and hydrophobic interactions with active site residues, validating the experimental data. In addition, in silico ADME profiling using SwissADME demonstrated compliance with Lipinski’s rule of five, favourable log P values and suitable topological polar surface area (TPSA), indicating good oral bioavailability and drug-likeness. Taken together, these results demonstrate that indazole-diaryl urea hybrids, particularly compounds R₇, R₈ and R₁₁, possess significant cytotoxic potential against breast cancer cells and outperform sorafenib in vitro. The combined experimental and computational data highlight these compounds as promising lead scaffolds for further optimisation and development of next-generation anticancer therapeutics.