Medicinal Chemistry of Small-Molecule c-Met Inhibitors: From Approved Therapies to Emerging Multitarget Anticancer Agents

The hepatocyte growth factor (HGF)/c-Met signaling pathway plays a central role in cellular proliferation, survival, migration, invasion, angiogenesis, and therapeutic resistance. Aberrant c-Met activation, driven by gene amplification, overexpression, activating mutations, exon 14-skipping alterations, or ligand-dependent stimulation, drives the development and progression of many solid tumors, positioning c-Met as a key target for anticancer drug development. The clinical effectiveness of c-Met-targeted treatments such as crizotinib, capmatinib, tepotinib, savolitinib, and cabozantinib has confirmed c-Met as a viable oncogenic driver for therapy, leading to the development of various next-generation inhibitors with different structures. This review provides a comprehensive perspective on small-molecule c-Met inhibitors from the perspectives of medicinal chemistry and structure-based drug design, encompassing approved drugs, investigational agents, natural-product-inspired leads, and emerging multitarget anticancer therapeutics. Particular emphasis is given to the principles of molecular recognition that govern c-Met inhibition. This includes the structure of the kinase domain, interactions at the ATP-binding site, recognition of the hinge region, and the different binding modes of Type I, Type II, and allosteric inhibitors. The design, synthesis, biological evaluation, and structure–activity relationships of diverse heterocyclic scaffolds that have shaped c-Met inhibitor discovery are critically analyzed. Key medicinal chemistry strategies, including scaffold hopping, bioisosteric replacement, conformational optimization, molecular hybridization, and multitarget pharmacophore integration, are discussed in the context of potency, selectivity, resistance management, and drug-like properties. Particular attention is given to the integration of structural biology, molecular docking, binding-mode analysis, and structure-guided optimization approaches that have enabled the development of potent c-Met-directed inhibitors. In addition, recent advances in dual- and multitarget agents that simultaneously modulate c-Met and complementary therapeutic targets, including VEGFR-2, EGFR, AXL, MER, PARP1, CDK2, and tubulin, are highlighted as promising strategies for overcoming pathway redundancy and acquired resistance. This review summarizes contemporary structure-based and medicinal chemistry principles underlying c-Met inhibitor discovery, critically evaluates the relationship between biochemical potency and therapeutic efficacy, and provides a framework for the rational design of next-generation c-Met-targeted and multitarget anticancer agents.