August 29, 2026
RESEARCH USE ONLY. Materials discussed as catalog items are supplied for laboratory research only. They are not for human or veterinary use, not drugs as sold here, and not intended to diagnose, treat, cure, or prevent any disease. Nothing on this page is medical advice or a protocol for any person or animal.
Three peptides sit in the same internet conversation and are not the same molecule. Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual GIP/GLP-1 receptor agonist. Retatrutide is a triple agonist at GIP, GLP-1, and glucagon receptors. The papers that compared them compared trial drug products under protocol. They did not compare research vials, and they did not write a catalog.
This is a short review of receptor pharmacology and of what those papers actually measured. PureLab Performance, Morgan Hill, California. Research use only. Not for human consumption.
| Semaglutide | Tirzepatide | Retatrutide | |
|---|---|---|---|
| Receptor pharmacology | GLP-1 receptor agonist (mono) | Dual GIP / GLP-1 receptor agonist | Triple agonist: GIP, GLP-1, and glucagon receptors |
| Literature identity | GLP-1 analog with an extended fatty-acid side chain. CAS 910463-68-2; formula C187H291N45O59 as listed in the public compound record. | 39-residue peptide based on the GIP sequence, engineered for dual-receptor activity (Willard et al., JCI Insight 2020). | Investigational LY3437943, characterised as a GIP/GLP-1/glucagon triple agonist (Coskun et al., Cell Metabolism 2022). |
| FDA status of the drug substance | FDA-approved drug substance in prescription products | FDA-approved drug substance in prescription products | Investigational. Not FDA-approved for any indication. |
| Direct head-to-head in the peer-reviewed record | SURPASS-2: tirzepatide vs semaglutide in type 2 diabetes (Frías et al., N Engl J Med 2021). Trial products, not research vials. | No published head-to-head versus semaglutide or tirzepatide as of August 2026. TRIUMPH-5 (NCT06662383) versus tirzepatide is running. | |
Willard et al., JCI Insight 2020, describe tirzepatide as an imbalanced, biased dual agonist: equal affinity to native GIP at GIPR, approximately five-fold weaker than native GLP-1 at GLP-1R, and a partial agonist at GLP-1R while remaining a full agonist at GIPR. That paper is often mis-cited as Coskun; Coskun is not an author on it. Coskun et al., Cell Metabolism 2022, is the discovery paper for retatrutide (LY3437943). Li et al., Cell Discovery 2024, report structural work on retatrutide’s triple agonism. Receptor count is the design difference. It is not a ranking, and it is not a reason to treat one research listing as a stand-in for another.
Semaglutide and tirzepatide are FDA-approved drug substances in specific prescription products. Those approvals attach to named, regulated pharmaceutical products — not to a research peptide with a similar sequence, and not to this page. Retatrutide is investigational. A Drugs@FDA query returns no approval record; the status note on this site is Is retatrutide FDA approved?.
This page is educational. The GLP-1-class research peptides PureLab Performance currently catalogs are tirzepatide and retatrutide, each as Research Use Only material, each with its own lot line. A literature identity is not a SKU.
Semaglutide injection products were added to FDA’s drug shortage list in 2022. FDA determined that shortage resolved in February 2025 (declaratory order, 21 February 2025). While the products were listed, compounding of copies expanded, and listings that mixed approved drugs, compounded copies, and research peptides multiplied. That history explains the noise. It is not a reason to treat a research vial as a drug product, and it is not a procurement instruction.
Frías et al., N Engl J Med 2021, reported SURPASS-2: a 40-week, phase 3, randomized, open-label trial of tirzepatide 5, 10, and 15 mg versus semaglutide 1 mg, once weekly, in adults with type 2 diabetes inadequately controlled on metformin. The primary endpoint was change in HbA1c. The paper reported greater HbA1c reduction with tirzepatide than with semaglutide 1 mg. Body weight was a secondary endpoint in a diabetes trial. Those measurements describe the trial drug products under protocol. They are not a specification for a laboratory reagent, and they are not restated here as a product claim.
Limits the paper itself flags, and that a review should not sand off:
Open questions remaining after SURPASS-2 include how the comparison would read against a higher semaglutide dose, over a longer horizon, in a different background-therapy population, and on outcomes the trial was not powered to assess. Companion note on the two-molecule slice: Tirzepatide vs semaglutide.
Retatrutide has no published head-to-head versus semaglutide. It also has no published head-to-head versus tirzepatide. Cross-trial tables that put a phase 2 retatrutide point estimate next to a phase 3 tirzepatide or semaglutide point estimate are not evidence of superiority. Different populations, durations, dose ladders, and blinding. The honest position is that those direct questions have not been answered.
Jastreboff et al., N Engl J Med 2023, reported a phase 2, randomized, double-blind, placebo-controlled trial of once-weekly retatrutide in adults with obesity, 48 weeks, primary endpoint percent change in body weight versus placebo. That is investigational trial product versus placebo, not versus semaglutide, and not a research-vial assay. The abstract reports dose-dependent increases in heart rate that peaked at 24 weeks and declined thereafter — an unflattering signal that belongs next to the efficacy line, not underneath it.
Bajaj et al., Lancet 2026, reported TRANSCEND-T2D-1, the first peer-reviewed phase 3 retatrutide trial, in type 2 diabetes. Phase 3 obesity results in the TRIUMPH program have been discussed as sponsor disclosures; they are not a substitute for the peer-reviewed papers. TRIUMPH-5 (NCT06662383) is the ongoing phase 3 comparison of retatrutide versus tirzepatide, with estimated primary completion in late 2026. Until it is published, every retatrutide-versus-tirzepatide table on the internet is an indirect comparison. See Retatrutide vs tirzepatide and what a triple agonist is.
A clinical paper tells you what a protocol measured in a defined population. A Certificate of Analysis tells you what a laboratory measured on a named lot. Those are different documents. Mixing them is how a peak-area ratio gets treated as a trial result, and how a trial result gets treated as a vial.
If the object in hand is a research peptide, the checks are lot match, a named laboratory, chromatographic purity versus fill versus label, and mass-spectrometric identity. How to read those fields: What to require on a retatrutide research COA and How to read a GLP-1 peptide COA. Public lot records: /coa/.
Three strings have to be identical: the lot on the vial, the lot on the PDF, and the lot on the product page. HPLC purity is a peak-area ratio. Content versus label is a fill question. They can diverge. On retatrutide lot fghe8m6 they did.
These listings are research-use-only peptides. They are not the prescription products in SURPASS-2, not investigational trial product from Jastreboff et al., and not interchangeable with one another because a paper compared two of the drug substances.
Use restriction: What “Research Use Only” means. Class hub: GLP-1 research peptides.
Not medical advice. Not a treatment comparison. Not a ranking of research listings. Not a reconstitution or administration protocol. Trial endpoints stay in the papers that measured them. Laboratory concentration math, when a lot has an assayed mass, is on GLP-1 peptide reconstitution and storage — arithmetic for a working solution, not use in a person.
Related reading: Tirzepatide vs semaglutide · Retatrutide vs tirzepatide · Semaglutide vs retatrutide · How does retatrutide work? · Is retatrutide FDA approved?.
Research Use Only (RUO). For laboratory research only. Not for human or veterinary use. Not a drug, not a supplement, not food. Not intended to diagnose, treat, cure, or prevent any disease. No statements on this page have been evaluated by the FDA. Retatrutide is investigational and not FDA-approved. Tirzepatide RUO material is not the FDA-approved prescription drug. Not for human consumption.
