VEGFR-2 as a druggable target: recent advances (2025) in the development of five-membered heterocyclic anticancer agents

The global burden of cancer continues to escalate, with angiogenesis representing a critical driver of tumor progression and metastasis. Vascular endothelial growth factor receptor-2 (VEGFR-2) stands as the principal mediator of angiogenic signaling, making it an established and compelling therapeutic target. Despite the clinical success of first-generation inhibitors, their long-term efficacy remains limited by off-target toxicities, suboptimal pharmacokinetic profiles, and the inevitable emergence of drug resistance through multiple adaptive mechanisms. These limitations underscore an urgent need for next-generation inhibitors engineered with enhanced selectivity, improved safety margins, and the capacity to circumvent resistance pathways. This comprehensive review systematically examines recent advances in the rational design, synthesis, and biological evaluation of five-membered heterocyclic scaffolds, thiadiazol, oxazole, thiazole, and pyrrole, as well as pyrazole and imidazole-based inhibitors as novel VEGFR-2 inhibitors. Each section analyzes the molecular hybridization strategies employed to integrate essential pharmacophoric features, including heteroaromatic hinge-binding motifs, hydrogen bond donor-acceptor systems for DFG motif engagement, and terminal hydrophobic groups for allosteric pocket occupancy. Detailed structure-activity relationship discussions elucidate how substituent variations influence potency, selectivity, and physicochemical properties.