Few areas of peptide research have advanced as quickly as the incretin class. In just a few generations, the design has progressed from molecules targeting a single receptor to molecules engaging three at once. Semaglutide, tirzepatide and retatrutide are the headline examples — and the differences between them come down to how many metabolic pathways each one activates.
Incretins: the shared foundation
Incretins are hormones the gut releases in response to food. The two most studied are GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Both influence insulin signalling and energy metabolism. A third receptor target, the glucagon receptor, adds a further dimension to energy expenditure. The "generations" of incretin research compounds are defined largely by how many of these receptors a single molecule is designed to engage.
Semaglutide — the single agonist
Semaglutide is a GLP-1 receptor agonist. It acts on one receptor family, and it is the most extensively characterised compound of the three. As a single-target molecule, it serves as the baseline reference point against which dual and triple agonists are compared in metabolic research. Its long half-life relative to native GLP-1 is one of the features most frequently studied.
Tirzepatide — the dual agonist
Tirzepatide is a dual GLP-1 / GIP receptor agonist. By engaging two incretin receptors with one molecule, it broadens the range of metabolic pathways under investigation in a single research arm. The addition of GIP activity is the defining difference from semaglutide and the reason tirzepatide is often described as a second-generation incretin compound.
Retatrutide — the triple agonist
Retatrutide extends the design further as a triple GLP-1 / GIP / glucagon receptor agonist. Adding the glucagon receptor introduces a pathway associated with energy expenditure on top of the two incretin receptors. As the newest of the three, it is the most active subject of comparative metabolic research and represents the current frontier of the multi-agonist approach.
Side-by-side comparison
| Compound | Receptor targets | Class | Generation |
|---|---|---|---|
| Semaglutide | GLP-1 | Single agonist | First |
| Tirzepatide | GLP-1 + GIP | Dual agonist | Second |
| Retatrutide | GLP-1 + GIP + glucagon | Triple agonist | Third |
Handling & reconstitution
Like other lyophilised peptides, these compounds are reconstituted with bacteriostatic water before use. Because incretin research often spans a wide dose range, getting the concentration maths right is essential for repeatable measurements across study arms.
Use our peptide reconstitution calculator to compute concentration and draw volume, and see how to reconstitute peptides for the full handling procedure.
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View the catalogueFrequently asked questions
What is the difference between semaglutide, tirzepatide and retatrutide?
Semaglutide is a single GLP-1 receptor agonist; tirzepatide is a dual GLP-1/GIP agonist; retatrutide is a triple GLP-1/GIP/glucagon agonist. They represent successive generations of incretin-based research compounds.
What does dual or triple agonist mean?
It refers to how many receptor types a single molecule activates. A dual agonist engages two receptor families and a triple agonist engages three, broadening the pathways studied in one compound.
Are these GLP-1 peptides approved for human use?
The reference compounds supplied here are for laboratory research use only and are not for human consumption. They are not approved medicines and are not intended to diagnose, treat, cure or prevent any disease.
This article is provided for educational and scientific reference only and does not constitute medical advice. All products referenced are sold strictly for laboratory research use, are not for human or animal consumption, and are not intended to diagnose, treat, cure or prevent any disease.