Indole-based anti-angiogenic agents via VEGFR-2 inhibition: A critical review.

Abstract

Tumor angiogenesis is an essential process in cancer progression, and vascular endothelial growth factor receptor-2 (VEGFR-2) continues to be one of the key targets for small-molecule anti-angiogenic therapy. This review critically summarizes the reported indole, oxindole, spirooxindole, and indazole derivatives as VEGFR-2-directed anticancer agents, including scaffold-based SAR, kinase binding modes, selectivity, multitarget design, and experimental anti-angiogenic validation. These chemotypes require the presence of a hinge-binding heteroaromatic head, an orienting linker, a hydrogen-bonding region engaging the αC/DFG network, and a hydrophobic back-pocket group, all in a coordinated fashion for fruitful inhibition. The contribution of each element depends on the scaffold and context. Oxindole and indazole scaffolds are effective hinge recognition motifs, but parent indoles and spirooxindoles are more promising for hybridization and 3-dimensional fine tuning. Critically, the clinically efficacious VEGFR inhibitors are typically multitarget kinase inhibitors, underscoring that therapeutic benefit is not solely a function of optimal VEGFR-2 selectivity but rather the balance of polypharmacology, exposure, and tolerability. The review also contrasts biochemical potency and docking predictions with cellular target engagement and functional vascular data, noting recurring enzyme-to-cell and exposure gaps. These findings support scaffold-specific optimization led by profiling against kinases, endothelial validation, pharmacokinetics, and mechanism-based lead progression.

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