GLP-1 Receptor Agonists Explained

Glucagon-like peptide-1 (GLP-1) receptor agonists have become the most-discussed peptide class in the metabolic research community. We've gone from single-agonist drugs like Semaglutide to dual-agonist Tirzepatide, and now triple-agonist Retatrutide. Here's how the science evolved.

The GLP-1 axis

GLP-1 is an incretin hormone released by intestinal L-cells after eating. It binds the GLP-1 receptor on pancreatic β-cells (driving glucose-dependent insulin secretion), and in the central nervous system (driving satiety signalling). Synthetic GLP-1 analogues are engineered to resist DPP-4 degradation, extending their half-life from minutes to days.

Single-agonist: Semaglutide

Semaglutide is a long-acting GLP-1 analogue with two key modifications: an Aib substitution at position 8 (DPP-4 resistance) and a fatty-acid moiety at position 26 (albumin binding for extended half-life). One-weekly dosing is standard in clinical-trial protocols.

Dual-agonist: Tirzepatide

Tirzepatide engages both the GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. The hypothesis: GIP co-activation amplifies GLP-1's metabolic effects while partially offsetting some GI side-effect signalling. Pre-clinical data show stronger weight-loss outcomes than Semaglutide in comparable models.

Triple-agonist: Retatrutide

Retatrutide adds a third receptor — glucagon — to the agonist portfolio. Glucagon receptor activity boosts energy expenditure (thermogenesis), which complements the appetite-suppression of GLP-1 and the metabolic effects of GIP. Phase 2 research data have shown the largest weight-loss magnitudes of any peptide class to date.

Beyond weight management

Researchers are also exploring GLP-1 RAs in cardiovascular, neurodegenerative, and inflammatory disease models — the receptor is expressed widely beyond the pancreas.

Comparing in our catalog

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