The Paradox and Future of GLP-1/GIP Combination Therapies: Efficacy and Mechanisms.
This review examines the evolution of GLP-1–based pharmacotherapies for obesity, tracing the discovery of glucagon-like peptide-1 (GLP-1) and assessing the clinical efficacy of GLP-1 receptor agonists (GLP-1RAs), with particular focus on semaglutide. The authors explore proposed central mechanisms by which GLP-1RAs may reduce appetite and body weight. A substantial portion of the review addresses the "paradox" surrounding glucose-dependent insulinotropic polypeptide receptor (GIPR) targeting: both dual GLP-1R/GIPR agonism (as seen with tirzepatide) and GLP-1R agonism combined with GIPR antagonism (as seen with maridebart cafraglutide) appear to yield favorable metabolic outcomes. The authors note a lack of evidence that GIPR agonism or antagonism alone produces meaningful anorectic effects in humans, raising mechanistic questions about how GIPR modulation enhances GLP-1RA efficacy. The review concludes by exploring additional explanations for why dual-targeting compounds appear to outperform semaglutide monotherapy. As a narrative review, this paper synthesizes existing literature rather than generating new primary data, and its conclusions are dependent on the quality and scope of the studies reviewed.
Why this grade: This is a narrative review that synthesizes existing preclinical and clinical literature rather than presenting original trial data, so it is graded as review-level evidence.
Glucagon-like peptide-1 (GLP-1)-based obesity pharmacotherapies have revolutionized obesity treatment. In this review, we discuss the discovery of GLP-1 and evaluate the efficacy of marketed and investigational GLP-1 receptor (GLP-1R) agonists (GLP-1RAs), most notably semaglutide, as well as their potential central mechanism of action. We highlight the GLP-1R/glucose-dependent insulinotropic polypeptide receptor (GIPR) dual agonist tirzepatide and the GLP-1RA/GIPR antagonist maridebart cafraglutide, discussing how both methods of GIPR targeting can produce beneficial metabolic effects. The lack of evidence for the anorectic effects of GIPR agonism or antagonism alone in humans is noted, and the review concludes with an evaluation of other reasons for the greater efficacy of GIPR/GLP-1R dual targeting compounds over semaglutide.
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