G-Protein–Coupled Receptors as Therapeutic Targets: Innovations, Challenges, and Future Opportunities in Drug Discovery

G protein-coupled receptors (GPCRs) establish one of the most lengthily investigated and therapeutically important receptor families in contemporary pharmacology. These receptors mediate the transduction of diverse extracellular stimuli into intracellular responses, thereby regulating many physiological processes and contributing to a wide spectrum of pathological conditions. Their central role in cell signalling underscores their importance as targets for novel therapeutic agents. Recent advances in structural biology—particularly cryo-electron microscopy and X-ray crystallography have yielded extraordinary insights into GPCR conformational states and ligand-binding mechanisms, driving a new era of structure-based drug design. Complementarily, computational methodologies, including artificial intelligence (AI) and machine-learning (ML) approaches, are accelerating the identification and optimisation of selective GPCR ligands for novel targeting. Despite this progress, several challenges, such as ligand specificity, receptor desensitisation, and the inherent complexity of biased signalling, remain notably high. In addition, the limited availability of high-resolution structures for receptor subtypes restricts toxicological specificity. Emerging strategies to address these limitations include precision pharmacology, integrating genomic and pharmacogenomic data, nanotechnology-enabled GPCR-targeted drug delivery systems, and the rational design of allosteric modulators.