How single, dual and triple incretin agonists differ by receptor target, what each added receptor contributes, and where each compound stands in development.
Semaglutide, tirzepatide and retatrutide are three successive generations of incretin-based research compounds. What separates them is how many hormone receptors each one is designed to activate, which makes the trio a useful way to study what changes when receptor targets are added one at a time.
One, two or three receptors
| Compound | Receptor targets | Class |
|---|---|---|
| Semaglutide | GLP-1 | Single agonist |
| Tirzepatide | GIP and GLP-1 | Dual agonist |
| Retatrutide | GIP, GLP-1 and glucagon | Triple agonist |
Each step in this progression has been studied as a test of a single question: does engaging an additional receptor produce an effect beyond what the existing pathways achieve on their own?
What each added receptor contributes
GLP-1
Glucagon-like peptide-1 receptor signalling is the shared foundation of all three compounds. It is the most extensively characterized pathway of the three, with a long research history in glucose regulation and gastric emptying.
GIP
Glucose-dependent insulinotropic polypeptide was long considered a weaker partner to GLP-1. Published work on tirzepatide renewed interest in it, and researchers now describe the GIP and GLP-1 combination as synergistic rather than simply additive, meaning the two pathways appear to interact rather than act independently.
Glucagon
Retatrutide’s third target is the glucagon receptor. Glucagon signalling on its own is associated with increased energy expenditure, but it also raises blood glucose. That tension is what makes retatrutide interesting to study: the design relies on concurrent GLP-1 and GIP activity to balance the glucose-raising effect of glucagon activation. Published trial reports to date describe the three pathways working in a balanced, complementary way in the populations studied.
What the trial programs measure
All three compounds have been evaluated in large, registered clinical trial programs: STEP for semaglutide, SURMOUNT for tirzepatide, and TRIUMPH for retatrutide. These programs track a common set of metabolic endpoints, including body weight, glycaemic markers such as HbA1c, and in some substudies liver fat. Readers who need the specific results should go to the primary publications. Those papers report outcomes in the context of their own protocols and populations, and those results do not transfer to any other setting.
Regulatory and development status
Semaglutide and tirzepatide are approved medicines with established regulatory histories in several jurisdictions. Retatrutide is investigational. It has not been approved by Health Canada, the FDA or the EMA and remains in Phase 3 trials. That difference matters when reading the literature, because retatrutide’s evidence base is at an earlier stage than that of the other two compounds.
Class-wide safety findings
Published trials report a broadly similar adverse-event profile across all three compounds, dominated by gastrointestinal effects. Thyroid C-cell findings from rodent studies and pancreatitis are tracked as class-wide considerations in ongoing programs. Long-term safety data for retatrutide is still accumulating as TRIUMPH progresses.
For researchers
Lot-level identity, purity and quantity results for the tirzepatide and retatrutide reference material we supply are published in our Lab Results library, with each certificate verifiable on the testing lab’s own site.
This article summarizes published research literature for general educational purposes. It is not usage, dosing or medical guidance. All products referenced are sold strictly for laboratory research use and are not for human or veterinary use.