Peptide hormone-receptor interactions serve as critical regulators of metabolic homeostasis, a paradigm exemplified by the clinical efficacy of glucagon-like peptide-1 (GLP-1) receptor agonists. Building upon this framework, strategic design has yielded unimolecular dual and triple agonists targeting GLP-1R, glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon receptor (GcgR), leveraging the sequence homology within the cognate native ligands of the class B G protein-coupled receptor (GPCR) family. However, the integration of Y2 receptor (Y2R) agonism─engaged by peptide YY (PYY) and belonging to the structurally divergent class A GPCR family─has remained an unaddressed challenge due to the topological and sequence disparities between these receptor classes. Y2R activation plays a pivotal role in appetite suppression, potentiating the metabolic benefits conferred by GLP-1R, GIPR, and GcgR agonism. Here, we report first-in-class, unprecedented tetra-agonists with high potency at GLP-1R, GIPR, GcgR, and Y2R. The chimeric peptides overcome the intrinsic sequence constraints imposed by class A and class B GPCR divergence, demonstrating the feasibility of rationally designed agonism mediated by single agents across receptor families. Lipidation of this template is well tolerated enhancing the promise of therapeutic viability. Furthermore, we show that biased agonism at GLP-1R selectively boosts cyclic AMP (cAMP) signaling while minimizing β-arrestin recruitment, thereby decoupling receptor desensitization from metabolic efficacy. Additionally, we introduce a tunable framework to modulate β-arrestin engagement without compromising cAMP potency, providing insight into the fine-tuning of GPCR-mediated signaling for next-generation peptide therapeutics.
