Semaglutide vs Tirzepatide vs Retatrutide: 2026 Metabolic Peptide Comparison
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Semaglutide vs Tirzepatide vs Retatrutide: 2026 Metabolic Peptide Comparison
By the ThePeptide Research Team · Every figure cited from its primary published trial · Last updated July 24, 2026
Semaglutide, tirzepatide, and retatrutide represent three successive generations of incretin-based research peptides — single-, dual-, and triple-receptor agonists. They progress from single-receptor (semaglutide, GLP-1) to dual (tirzepatide, GIP/GLP-1) to triple (retatrutide, GIP/GLP-1/glucagon) incretin-receptor engagement. This guide compares their mechanisms, receptor pharmacology, safety, and molecular profiles for Canadian laboratory researchers, with each trial figure drawn from its own published source.
Key takeaways
- More receptors, more pathways engaged. The class progresses from single GLP-1 to dual GIP/GLP-1 to triple GIP/GLP-1/glucagon receptor engagement.
- Not a head-to-head study. Each figure comes from a separate trial and population — the numbers show a trend, not a controlled comparison.
- Two approved, one investigational. Semaglutide and tirzepatide are approved drugs in some markets; retatrutide is Phase 3. All material here is research-use-only.
- Retatrutide's Phase 3 package is now complete. TRIUMPH-1 (obesity), TRIUMPH-2 (type 2 diabetes) and TRIUMPH-3 (cardiovascular disease) have all reported; Lilly plans submissions in 2027.
- Same GI-dominant safety pattern. All three reported concentration-dependent nausea, diarrhea, and vomiting in trials.
- Pick by research question, not "strength" — single-target, dual, or triple-agonist pharmacology.
At a Glance
| Feature | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Receptor targets | GLP-1 (single) | GIP + GLP-1 (dual) | GIP + GLP-1 + glucagon (triple) |
| Pivotal trial | STEP 1, 68 wks | SURMOUNT-1, 72 wks | TRIUMPH-1, 104 wks |
| Developer | Novo Nordisk | Eli Lilly | Eli Lilly |
| Regulatory status | Approved (Ozempic/Wegovy) | Approved (Mounjaro/Zepbound) | Phase 3 (investigational) |
| Amino acids | 31 | 39 | 34 |
| CAS number | 910463-68-2 | 2023788-19-2 | 2381089-83-2 |
| Full research guide | Semaglutide | Tirzepatide | Retatrutide |
Mechanism: Single vs Dual vs Triple Agonism
The defining difference between these three peptides is how many incretin/metabolic receptors each engages:
- Semaglutide — single (GLP-1). A GLP-1 receptor agonist associated with glucose-dependent insulin secretion, glucagon suppression, delayed gastric emptying, and central appetite signaling. Read the full semaglutide guide.
- Tirzepatide — dual (GIP + GLP-1). Adds a second incretin pathway (GIP) to GLP-1 in one molecule — the "twincretin" concept. Read the full tirzepatide guide.
- Retatrutide — triple (GIP + GLP-1 + glucagon). Layers glucagon-receptor agonism, associated with increased energy expenditure, on top of the GIP/GLP-1 pair. Read the full retatrutide guide.
Researchers study whether adding pathways — appetite-related incretin signaling plus a metabolic-rate pathway — broadens the metabolic-signalling range engaged, a question examined across the trials. ↑ Back to top
Clinical Trial Evidence
The pivotal trials below are each the compound's own registrational obesity study. They are separate trials in separate populations, not a single head-to-head study.
| Compound | Pivotal trial (citation) | Duration |
|---|---|---|
| Semaglutide | STEP 1 (Wilding et al., NEJM 2021) | 68 weeks |
| Tirzepatide | SURMOUNT-1 (Jastreboff et al., NEJM 2022) | 72 weeks |
| Retatrutide | TRIUMPH-1 (Eli Lilly, 2026) | 104 weeks |
The progression from single to dual to triple agonism is the central axis of comparison across these trials.
Retatrutide's Phase 3 program has since expanded. On July 23, 2026, Lilly reported TRIUMPH-2 (adults with type 2 diabetes, 80 weeks) and TRIUMPH-3 (adults with established cardiovascular disease), alongside the primary readout in the non-diabetic obesity trial (TRIUMPH-1). TRIUMPH-3 also reported a neutral cardiovascular (MACE) result. See the primary releases for reported endpoints. ↑ Back to top
Safety Comparison
Across all three compounds the most frequently reported adverse events in the trials were gastrointestinal and concentration-dependent — predominantly nausea, diarrhea, vomiting, and constipation. In the retatrutide TRIUMPH-1 program the reported rates in the highest arm were nausea ~42%, diarrhea ~32%, constipation ~26%, and vomiting ~25%, with treatment discontinuation of 11.3% versus 4.9% for placebo; the semaglutide and tirzepatide programs reported the same GI-dominant pattern. These figures describe outcomes in published clinical trial populations, reported for reference only. ↑ Back to top
Molecular Profiles
| Property | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| CAS number | 910463-68-2 | 2023788-19-2 | 2381089-83-2 |
| Molecular formula | C187H291N45O59 | C225H348N48O68 | (lipidated 34-mer) |
| Molar mass | ~4113.6 g/mol | ~4813.5 g/mol | lipidated 34-aa peptide |
| Amino acids | 31 | 39 | 34 |
| Structure | Fatty-acid (albumin-binding) | Fatty-acid (C20 diacid) | Fatty-acid lipidated |
All three are fatty-acid-modified peptides whose albumin binding gives them an extended half-life. ↑ Back to top
Choosing a Compound for Research
Selection is a function of the research question, not personal use. In practice, researchers reference: semaglutide as the extensively characterized single-target GLP-1 benchmark; tirzepatide when studying dual GIP/GLP-1 "twincretin" pharmacology; and retatrutide when investigating triple-agonist activity and the added glucagon/energy-expenditure arm. All three are supplied by ThePeptide as independently tested, Canadian-shipped lyophilized powder for laboratory research. ↑ Back to top
Semaglutide (GLP-1) — Summary
The most-studied GLP-1 receptor agonist (Novo Nordisk; Ozempic/Wegovy). It is the standard single-receptor reference compound, characterized in STEP 1 (68 weeks). Full details, molecular data, and sourcing are in the Semaglutide Canada research guide, and product options are Semaglutide 5mg and 10mg.
Tirzepatide (GIP/GLP-1) — Summary
The first dual GIP/GLP-1 agonist (Eli Lilly; Mounjaro/Zepbound), characterized in SURMOUNT-1 (72 weeks). Full details are in the Tirzepatide Canada research guide; products are Tirzepatide 5mg and 10mg.
Retatrutide (Triple Agonist) — Summary
The first triple GIP/GLP-1/glucagon agonist (Eli Lilly; investigational). It was characterized in Phase 3 TRIUMPH-1 (104 weeks), with TRIUMPH-2 (type 2 diabetes) and TRIUMPH-3 (established cardiovascular disease, neutral MACE result) reported in July 2026; Lilly plans regulatory submissions in 2027. Full details are in the Retatrutide Canada research guide; the product is Retatrutide 10mg.
How to buy research peptides in Canada →
Frequently Asked Questions
Which is stronger: semaglutide, tirzepatide, or retatrutide?
They differ by receptor engagement rather than a single "strength" ranking: semaglutide is a single GLP-1 agonist, tirzepatide a dual GIP/GLP-1 agonist, and retatrutide a triple GIP/GLP-1/glucagon agonist, each characterized in its own pivotal trial (STEP 1, SURMOUNT-1, TRIUMPH-1). These are separate trials, not a head-to-head study, reported here for research reference only.
What is the mechanistic difference between them?
Semaglutide is a single GLP-1 agonist, tirzepatide is a dual GIP/GLP-1 agonist, and retatrutide is a triple GIP/GLP-1/glucagon agonist. Each added receptor engages a further metabolic pathway.
Are any of them approved?
Semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound) are approved as drugs in some markets; retatrutide is investigational (Phase 3). All material sold by ThePeptide is research-use-only, not the approved drug products, and not for human consumption.
Which should I choose for research?
It depends on the research question — semaglutide for single-target GLP-1 work, tirzepatide for dual GIP/GLP-1 pharmacology, retatrutide for triple-agonist and glucagon-arm studies. See the individual guides for full detail.
Do they share the same side-effect profile?
All three reported predominantly gastrointestinal, concentration-dependent adverse events (nausea, diarrhea, vomiting, constipation) in their trials. Reported for reference only.
Related Research Resources
- Retatrutide Canada guide · Tirzepatide Canada guide · Semaglutide Canada guide
- Where to get research peptides tested in Canada
- How to buy research peptides in Canada
References
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384:989-1002. DOI: 10.1056/NEJMoa2032183.
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387:205-216. DOI: 10.1056/NEJMoa2206038. PMID: 35658024.
- Jastreboff AM, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity (Phase 2). N Engl J Med. 2023;389:514-526. DOI: 10.1056/NEJMoa2301972.
- Eli Lilly and Company. Retatrutide Phase 3 TRIUMPH-1 topline results, May 2026.
- Eli Lilly and Company. Retatrutide successful in two additional Phase 3 trials (TRIUMPH-2 and TRIUMPH-3 topline), July 23, 2026. investor.lilly.com.