Retatrutide vs Semaglutide: What’s the Difference?
Retatrutide and semaglutide are both lipidated, once-weekly peptides studied in metabolic research, but they act on a different number of receptors.
Semaglutide (Novo Nordisk) is a 31-residue analogue of human GLP-1 and a selective GLP-1 receptor agonist. It is the active ingredient of FDA-approved Ozempic, Wegovy and Rybelsus.
Retatrutide (Eli Lilly, LY3437943) is a 39-residue peptide built on the GIP backbone that activates three receptors: GIP, GLP-1 and glucagon. It is investigational, in phase 3, and not approved anywhere. Research catalogues also list it as GLP-3 R or GLP-3 RT.
In short: semaglutide is one receptor, retatrutide is three. Tirzepatide, with two (GIP and GLP-1), sits between them.
Retatrutide vs Semaglutide at a Glance
Retatrutide is a 39-residue GIP-backbone peptide (C221H342N46O68, 4,731.34 g/mol) that activates three receptors. Semaglutide is a 31-residue GLP-1 analogue (C187H291N45O59, 4,113.58 g/mol per the FDA label) that activates one. Semaglutide is FDA-approved; retatrutide is not approved anywhere.
| Comparison | Retatrutide | Semaglutide |
|---|---|---|
| Peptide length | 39 amino acids | 31 amino acids |
| Molecular weight | 4,731.34 g/mol | 4,113.58 g/mol |
| Sequence | YXQGTFTSDYSILLDKKAQXAFIEYLLEGGPSSGAPPPS-NH2 | HXEGTFTSDVSSYLEGQAAKEFIAWLVRGRG |
| Molecular relationship | GIP-backbone triple agonist | GLP-1(7-37) analogue |
| Main research focus | GIP, GLP-1 and glucagon receptor signalling | Selective GLP-1 receptor signalling |
| Research evidence | Phase 1–3 trials; investigational | Large phase 3 and outcomes trials; FDA-approved |
| FDA-approved drug component | No | Yes (Ozempic, Wegovy, Rybelsus) |
What are Retatrutide and Semaglutide
39 AA
Retatrutide
A 39-residue lipidated peptide from Eli Lilly that activates the GIP, GLP-1 and glucagon receptors in one molecule.
Research areas
GIPR • GLP-1R • GCGR • Metabolic models
X = Aib at positions 2 and 20; position 13 is α-methyl-leucine; Lys17 carries a C20 fatty diacid through a γGlu–AEEA linker. In vitro it showed balanced glucagon- and GLP-1-receptor activity with more GIP-receptor activity, and its half-life in a phase 1b study was about 6 days.
Explore GLP-3 Reta (retatrutide)31 AA
Semaglutide
A 31-residue GLP-1 analogue from Novo Nordisk with 94% sequence homology to human GLP-1, acting on the GLP-1 receptor only.
Research areas
GLP-1R • Incretin biology • Metabolic and cardiovascular outcomes research
X = Aib at position 8, which protects against DPP-4; Arg34 replaces Lys; Lys26 carries a C18 fatty diacid through a hydrophilic spacer. The FDA label gives an elimination half-life of about one week.
Key Differences Between Retatrutide and Semaglutide
| Key differences | Retatrutide | Semaglutide |
|---|---|---|
| Receptors | Three: GIP receptor, GLP-1 receptor and glucagon receptor. |
One: the GLP-1 receptor (the label calls it selective). |
| Backbone | Built on the GIP sequence; 39 residues with a C-terminal amide. |
Built on human GLP-1(7-37); 31 residues with a free C-terminal acid. |
| Lipidation | C20 fatty diacid on Lys17 via γGlu–AEEA. |
C18 fatty diacid on Lys26 (GLP-1 numbering) via two AEEA units and γGlu. |
| Reported half-life | About 6 days (phase 1b, type 2 diabetes). |
About 1 week (FDA label). |
| Clinical programme | Phase 2 (NEJM, Lancet 2023) and phase 3 TRIUMPH and TRANSCEND-T2D trials, several published in 2026. |
Phase 3 STEP and SUSTAIN programmes plus cardiovascular (SELECT) and kidney (FLOW) outcomes trials. |
| Regulatory status | Investigational; not approved by FDA or any regulator. |
FDA-approved since 2017 (Ozempic), with Rybelsus and Wegovy following. |
How their research profiles differ
- Retatrutide
- 39-AA GIP-backbone peptide
- GIP + GLP-1 + glucagon receptors
- Triple-agonist metabolic research
- Semaglutide
- 31-AA GLP-1 analogue
- GLP-1 receptor only
- Selective GLP-1 research
Retatrutide vs Semaglutide: Which Is Better?
There is no head-to-head result to answer that yet. The two have been studied in different trials, with different populations, durations and endpoints, so their published results cannot be compared directly.
A phase 3 trial comparing retatrutide with semaglutide in type 2 diabetes (NCT06260722) is registered and was still running in October 2026.
For research purposes the useful distinction is pharmacological: semaglutide isolates GLP-1 receptor signalling, while retatrutide adds GIP and glucagon receptor activity on top of it.
Does the model need selective GLP-1 receptor agonism, or the combined GIP, GLP-1 and glucagon receptor profile?
Can Retatrutide and Semaglutide Be Studied Together?
They can be compared in the same research programme, as separate groups, when the aim is to separate GLP-1-receptor effects from the added contribution of GIP and glucagon receptors. Tirzepatide is a natural third arm, since it adds GIP but not glucagon.
Giving both in the same condition is a different question: both act on the GLP-1 receptor, so their effects would overlap and could not be attributed.
There Isn’t One Universal “Winner”
Retatrutide
Triple-agonist research profile
GIP • GLP-1 • glucagon • investigational
Semaglutide
Selective GLP-1 research profile
GLP-1R only • FDA-approved molecule
Compare the Research. Verify the Material.
Clean Peptide stocks retatrutide as GLP-3 Reta in 10, 20 and 30 mg. Each size has its own lot, analysed by ILS Laboratories with a full QC panel, including identity by HPLC retention time against a retatrutide reference standard.
We do not stock semaglutide at the moment. Our tirzepatide (GLP-2 Tirz) and survodutide are in the catalogue with their own certificates.
Research use only
Identity
verified
Purity
verified
Endotoxin
verified
Tested
in USA
Research use only- Identity
verified - Purity
verified - Endotoxin
verified - Tested
in USA
Question
Frequently Asked
What is the difference between retatrutide and semaglutide?
Semaglutide activates one receptor, the GLP-1 receptor. Retatrutide activates three: GIP, GLP-1 and glucagon. Semaglutide is FDA-approved; retatrutide is investigational.
Is retatrutide stronger than semaglutide?
No head-to-head trial has reported yet. They were studied in separate trials with different populations, so their results cannot be compared directly. A retatrutide vs semaglutide phase 3 trial (NCT06260722) is under way.
Are retatrutide and semaglutide made by the same company?
No. Retatrutide is from Eli Lilly, which also developed tirzepatide. Semaglutide is from Novo Nordisk.
How long are their half-lives?
Retatrutide's half-life was about 6 days in a phase 1b study; semaglutide's elimination half-life is about one week per its FDA label. Both were given once weekly in trials.
What is retatrutide vs Ozempic?
Ozempic is a brand of semaglutide. So retatrutide vs Ozempic is the same comparison: a triple GIP/GLP-1/glucagon agonist against a selective GLP-1 agonist.
Where does tirzepatide fit?
Tirzepatide activates two receptors, GIP and GLP-1. It sits between semaglutide (one receptor) and retatrutide (three).
Does Clean Peptide sell semaglutide?
Not at the moment. We stock retatrutide (GLP-3 Reta), tirzepatide (GLP-2 Tirz) and survodutide, each with per-lot certificates.
Research Peptides. Documented by Batch.
Every size in the catalogue ships against the certificate issued for its own lot.
For laboratory research use only. Not for human or veterinary use.
References
Identity data come from the FDA labels, the FDA substance registry (GSRS), KEGG and PubChem. Trial descriptions follow the PubMed abstracts.
- Coskun T, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept Cell Metabolism, 2022. Discovery and receptor profile of retatrutide.
- Urva S, et al. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial Lancet, 2022. Half-life of about 6 days.
- Jastreboff AM, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity NEJM, 2026. Phase 3 TRIUMPH-1.
- Lau J, et al. Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide Journal of Medicinal Chemistry, 2015. Design, substitutions and albumin binding.
- FDA label Ozempic (semaglutide) injection Structure, formula, molecular weight, selectivity and half-life.
- Li W, et al. Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide Cell Discovery, 2024. Acylation sites of semaglutide, tirzepatide and retatrutide.
- ClinicalTrials.gov NCT06260722 Phase 3, retatrutide vs semaglutide in type 2 diabetes; ongoing.
- KEGG DRUG Retatrutide, D12430 Sequence, formula and molecular weight.
