Novel imidazo[2,1-b]thiazoles and imidazo[1,2-a]pyridines tethered with indolinone motif as VEGFR-2 inhibitors and apoptotic inducers: Design, synthesis and biological evaluations.

The current study investigates the anticancer and VEGFR-2 inhibitory activities of 16 novel indolinone-grafted imidazo[2,1-b]thiazole and imidazo[1,2-a]pyridine derivatives (6a-h and 10a-h). The structures of these target compounds were confirmed using elemental and spectral analyses. All compounds were evaluated for their VEGFR-2 inhibitory activity in vitro, with eight compounds demonstrating promising results, exhibiting IC values in the sub-micromolar range (0.22 μM - 0.95 μM). Additionally, the anticancer potential of these compounds was assessed using an MTT assay against two breast cancer cell lines, MCF-7 and MDA-MB-231. Compounds 6a, 6f, 6 h, and 10f showed superior performance (IC = 9.79, 8.78, 8.35, and 10.88 µM, respectively) compared to the reference drug cisplatin (IC = 11.50 µM) against MDA-MB-231 cells. Based on their consistent VEGFR-2 inhibitory activity, compounds 6a, 6 h, and 10f were selected for further analysis. Molecular docking studies with VEGFR-2 (PDB ID: 4AGD) revealed binding behaviors similar to the co-crystallized ligand sunitinib. Among the reported target molecules, compound 10f exhibited the most desirable characteristics in terms of efficacy and safety and was further analyzed using density-functional theory (DFT) simulations to better understand its physical properties.