Key takeaways
- Ozempic (semaglutide) activates one receptor: GLP-1. Retatrutide activates three: GIP, GLP-1 and glucagon.
- Semaglutide is an approved prescription medicine. Retatrutide is investigational and not approved by Health Canada or the FDA.
- Both use a fatty-acid side chain that binds albumin, giving each a long half-life suited to once-weekly dosing in clinical studies.
In this guide
- At a glance
- What is Ozempic?
- What is retatrutide?
- The key differences
- Where tirzepatide fits
- What researchers compare
- FAQ
At a glance
| Ozempic (semaglutide) | Retatrutide | |
|---|---|---|
| Receptor targets | GLP-1 | GIP + GLP-1 + glucagon |
| Agonist type | Single | Triple |
| Developer | Novo Nordisk | Eli Lilly |
| Peptide length | 31 amino acids (GLP-1 analogue) | 39 amino acids |
| Half-life extension | C18 fatty diacid side chain binds albumin | C20 fatty diacid side chain binds albumin |
| Molecular weight | 4,113.6 g/mol | 4,731.3 g/mol |
| Status | Approved prescription medicine | Investigational (phase 3) |
What is Ozempic?
Ozempic is Novo Nordisk's brand name for semaglutide, a GLP-1 receptor agonist. It's approved in Canada and many other countries as a prescription medicine for type 2 diabetes. The same molecule is sold at a different strength as Wegovy for chronic weight management, and in tablet form as Rybelsus.
Semaglutide is based on the human GLP-1 hormone, with changes that protect it from rapid breakdown and a fatty-acid side chain that binds albumin in the blood. Native GLP-1 lasts only minutes in the body; semaglutide's half-life is about a week.
What is retatrutide?
Retatrutide (LY3437943) is an investigational peptide developed by Eli Lilly. It's a single 39-amino-acid molecule designed to activate the GIP, GLP-1 and glucagon receptors, which is why it's called a triple agonist. Like semaglutide, it carries a fatty-acid side chain that binds albumin and extends its half-life.
Retatrutide has been through phase 2 trials, published in 2023, and Eli Lilly announced topline results from its phase 3 TRIUMPH program in 2026. It is not approved by Health Canada, the FDA or any other regulator. For a full profile, see Retatrutide: understanding the triple receptor agonist.
The key differences
One receptor vs three
This is the core difference. Semaglutide works entirely through the GLP-1 receptor, which is involved in insulin secretion, appetite signalling and gastric emptying. Retatrutide adds two more pathways: GIP, the other main incretin hormone, and glucagon, which is linked to liver glucose output, lipid metabolism and energy expenditure.
Receptor balance
A multi-receptor compound isn't equally strong at every target. In its discovery study, retatrutide showed comparatively stronger activity at the GIP receptor, with more balanced activity at the GLP-1 and glucagon receptors (Coskun et al., 2022). How that balance affects results is one of the main research questions.
Status
Semaglutide has years of clinical use and regulatory approval behind it. Retatrutide is still investigational, and its long-term safety profile is still being established in clinical trials.
Where tirzepatide fits
Between the two sits tirzepatide (Mounjaro, Zepbound), a dual GIP and GLP-1 agonist, also from Eli Lilly. The three compounds form a progression: one receptor, then two, then three. Our comparison of retatrutide vs tirzepatide vs semaglutide covers all three side by side.
What researchers compare
- Receptor pharmacology: potency and selectivity at each receptor.
- Single vs multi-receptor signalling: whether adding GIP and glucagon activity changes outcomes compared with GLP-1 alone.
- Energy expenditure and liver fat: areas where glucagon receptor activity is of particular interest.
- Glucose regulation: how the glucose-raising effect of glucagon is balanced by incretin activity.
Frequently asked questions
Is retatrutide the same as Ozempic?
No. Ozempic is semaglutide, which activates only the GLP-1 receptor. Retatrutide is a different molecule that activates the GIP, GLP-1 and glucagon receptors.
Is retatrutide approved like Ozempic?
No. Ozempic (semaglutide) is an approved prescription medicine. Retatrutide is investigational and has not been approved by Health Canada, the FDA or any other regulator.
Who makes Ozempic and retatrutide?
Ozempic is made by Novo Nordisk. Retatrutide is being developed by Eli Lilly, which also makes tirzepatide.
Why does retatrutide target glucagon?
Glucagon receptor activity is associated with energy expenditure and liver lipid metabolism. Pairing it with incretin activity, which can offset glucagon's glucose-raising effect, is the research rationale behind triple agonists.
References
- Coskun T, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss. Cell Metab. 2022;34(9):1234–1247.
- Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity — a phase 2 trial. N Engl J Med. 2023;389(6):514–526.
