Peptides MEX / Comparisons
Retatrutide vs semaglutide: receptors and trial interpretation
Retatrutide was designed to activate GIP, GLP-1 and glucagon receptors; semaglutide acts at GLP-1 receptors. That distinction describes pharmacology. Comparing outcomes requires examining participants, endpoints and controls, rather than aligning percentages from independent trials.
Updated · Sources and editorial standards
| Feature | Retatrutide | Semaglutide |
|---|---|---|
| Described receptors[1][2] | GIP, GLP-1 and glucagon | GLP-1 |
| Selected weight trial[3][2] | Phase 2, 2023; 338 adults; 48 weeks | STEP 1; 1,961 participants; 68 weeks |
| Comparator in those trials[3][2] | Placebo; not semaglutide | Placebo; not retatrutide |
One receptor and three receptors are not an efficacy scale
The retatrutide discovery paper, using the name LY3437943, described activity at three receptors and combined in vitro experiments, animal models and early clinical evaluation. Semaglutide was investigated as a GLP-1 analogue. Counting receptors alone does not establish benefit size, adverse events or an individual response.
Two weight trials with different designs
The 2023 retatrutide phase 2 trial included 338 adults and followed weight changes through 48 weeks. STEP 1 evaluated semaglutide in 1,961 participants over 68 weeks. Both used placebo, but did not randomize between the two molecules. Their design differences prevent interpreting a subtraction of percentages as a causal advantage.
Body weight and cardiovascular events are distinct outcomes
SELECT studied semaglutide in people with established cardiovascular disease, overweight or obesity and no diabetes. Its primary endpoint was a composite of cardiovascular events, rather than weight alone. The 2023 retatrutide trial cited here focused on weight change. Evidence for one outcome should not be transferred to another molecule or population.
Questions about this reference
Does triple agonism necessarily mean greater efficacy?
No. It describes the receptor set activated. Comparative efficacy requires a design that can attribute differences to the interventions, with attention to the endpoint and population.
Sources and original reading
- LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept
- Once-Weekly Semaglutide in Adults with Overweight or Obesity
- Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial
- Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes
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