A High-Potency Protein That Normalizes Body Weight in DIO Mice through Triple Agonism at FGF21, GLP1, and GIP Receptors

Obesity and its associated metabolic syndrome present significant therapeutic challenges, with current pharmacological interventions often falling short of replicating the multifaceted benefits of bariatric surgery. Recent advances in incretin-based therapies, particularly GLP-1 and GIP coagonists, have demonstrated substantial improvements in glycemic control and weight management, yet residual cardiovascular risk and lipid abnormalities persist. Fibroblast growth factor 21 (FGF21) has emerged as a promising protein to complement incretin pharmacology due to its potent lipid-lowering effects and favorable safety profile. This study describes the engineering of a balanced, long-acting triple agonist that simultaneously targets FGF21, GLP-1, and GIP receptors. Through strategic N- and C-terminal modifications and lipid conjugation, a novel optimized FGF21 analogue is engineered to exhibit enhanced potency, stability, and sustained pharmacokinetics compared to native protein. In Diet-Induced Obesity (DIO) mice, this FGF21 analogue achieves near normalization of body weight, superior to benchmark GLP-1 agonists, and demonstrates additive efficacy when combined with a GLP-1/GIP receptor coagonist. Based on this additivity, a unimolecular triagonist is engineered, and mechanistic studies confirm balanced receptor activity at the FGF21 and incretin receptors to achieve combinational pharmacology, with significant reductions in body fat, improved glucose tolerance, and extended duration of action. These findings position the FGF21/GLP-1/GIP triagonist as a first-in-class candidate for next-generation metabolic disease therapy, potentially approximating the efficacy of surgical intervention while addressing lipid disorders inadequately managed by current incretin therapies.