GLP-1 and Multi-Agonist Research Peptides Compared: Semaglutide, Tirzepatide, Retatrutide, Cagrilintide and Survodutide

Five compounds dominate metabolic peptide research right now, and they are routinely discussed as if they were interchangeable. They are not. They hit different receptors, they sit at very different points on the evidence curve, and three of the five have never been approved by any regulator anywhere.

This is a comparison of what the published literature establishes for each one, where the gaps are, and what that means when you are selecting a research material. It contains no dosing, no protocols, and no administration guidance.

Research use only. Every compound discussed here is supplied for laboratory and in-vitro research. None is a drug, a supplement, or a therapeutic product as sold. None is intended or sold for human or veterinary administration or consumption.

The short version

The pattern worth noticing: receptor count still tracks inversely with regulatory maturity, but through 2026 the evidence gap has narrowed sharply. All five now have phase 3 data reported or under regulatory review. What separates them is no longer whether the trials have run, but how far the follow-up extends and how much post-approval population data exists — and on that axis the two approved molecules remain well ahead.

Why the receptor target is the thing that actually matters

Everything else in this comparison follows from mechanism, so it is worth being precise.

GLP-1 receptor agonism is the established anchor. Glucagon-like peptide-1 is an incretin — a gut hormone released in response to nutrient intake. Agonism at its receptor has been studied for well over two decades, and the downstream effects on insulin secretion, gastric emptying and central appetite signalling are among the better-characterised pathways in metabolic pharmacology.

GIP receptor agonism was, for years, the confusing one. Glucose-dependent insulinotropic polypeptide is the other major incretin, and earlier work suggested GIP agonism might be metabolically unhelpful. Tirzepatide’s clinical results forced a reassessment of that assumption, and the mechanistic question — how much of the effect is GIP-mediated, and through which tissues — is still genuinely open in the literature.

Glucagon receptor agonism is the newest addition and the most counterintuitive, since glucagon opposes insulin. The rationale is energy expenditure: glucagon receptor activation increases hepatic energy output, so the design bet is that pairing it with incretin agonism captures that effect while the GLP-1 component offsets the glycaemic downside. Whether that balance holds across a long enough horizon is exactly what the ongoing phase 3 programmes are testing.

Amylin/calcitonin receptor agonism sits outside the incretin axis entirely. Amylin is co-secreted with insulin from beta cells and acts on satiety signalling through a different route. That mechanistic independence is why cagrilintide is studied mostly in combination rather than alone — it is additive to, not redundant with, GLP-1 agonism.

Compound by compound

Semaglutide — the reference point

Semaglutide is the most thoroughly documented molecule in this group and functions as the literature’s comparator. Its published record spans large glycaemic trials, large weight-related trials, and — unusually for this category — a dedicated cardiovascular outcomes trial that reported a significant reduction in major adverse cardiovascular events in a population with established cardiovascular disease.

That outcomes data matters for a reason that has nothing to do with the endpoint itself: it means semaglutide has been observed in large populations over multi-year horizons. For a research material, that translates into an unusually rich body of comparator data, well-characterised pharmacokinetics, and widely available reference standards.

Structurally it is a 31-amino-acid GLP-1 analog with substitutions resisting DPP-4 degradation and a C18 fatty diacid chain enabling albumin binding. That acylation produces the long half-life — and, as discussed below, it also complicates analytical characterisation.

Tirzepatide — the dual agonist

Tirzepatide is a 39-amino-acid synthetic peptide engineered to activate both GIP and GLP-1 receptors, with a C20 fatty diacid moiety. Its phase 3 programme covered glycaemic control and weight endpoints, and later trials extended into sleep-disordered breathing and heart failure with preserved ejection fraction — a signal that research interest has broadened beyond the original metabolic framing.

In head-to-head published comparisons against semaglutide, tirzepatide produced larger effects on the primary endpoints studied. That is the finding most often cited, and it is real — but it is worth reading alongside the fact that the two molecules have different tolerability profiles and different discontinuation patterns in trial populations.

For research purposes, tirzepatide is the compound where the mechanistic question is most interesting and least settled: the relative contribution of the GIP arm remains debated, and receptor-level work on that question is ongoing.

Retatrutide — the triple agonist

Retatrutide engages GIP, GLP-1 and glucagon receptors in a single molecule, and it has produced the largest weight-related effect sizes reported in this class. Phase 3 TRIUMPH-1 topline results, announced in May 2026, covered 2,339 randomised participants over 80 weeks: the 12 mg arm averaged 28.3% weight reduction against 2.2% for placebo, and a 104-week extension in participants with baseline BMI of 35 or above averaged 30.3%.

It remains investigational and is not approved in any market; TRIUMPH-2 and TRIUMPH-3 are expected to report later in 2026. What is still thin is long-horizon safety data, particularly anything relating to sustained glucagon receptor activation, and the post-approval population evidence that semaglutide has accumulated over years. We covered the compound in depth in the full retatrutide trial record, including why vendor vetting matters more here than for any other compound on this list.

The practical consequence for sourcing: retatrutide has no approved pharmaceutical reference product, which means no pharmacopoeial monograph and fewer independent points of comparison for identity confirmation. Analytical documentation carries more weight here, not less.

Cagrilintide — the one that isn’t an incretin

Cagrilintide is a long-acting amylin analog, and it is the odd one out mechanistically. Most of its published record comes from combination studies with semaglutide rather than monotherapy. In REDEFINE 1, the combination produced 20.4% weight loss over 68 weeks against 3.0% for placebo, and Novo Nordisk filed it with the FDA in December 2025 with a review expected during 2026. Cagrilintide itself is not approved as a standalone agent.

If you are working on additive or synergistic mechanisms, this is the compound that makes the question tractable, because its pathway is genuinely separate from the incretin axis. We stock it as a standalone material, which for most research designs is preferable to a fixed-ratio blend: pairing it with separately sourced semaglutide leaves the ratio under your control.

Survodutide — the GLP-1/glucagon dual

Survodutide targets GLP-1 and glucagon receptors — retatrutide minus the GIP arm. That makes it mechanistically useful as a comparator: set against retatrutide, the difference between the two isolates what the GIP component contributes.

Phase 3 SYNCHRONIZE-1 reported results across 725 adults over 76 weeks: the 6.0 mg arm averaged 13.0% weight reduction against 5.4% for placebo under the treatment-policy estimand, or 16.6% against 3.2% under the efficacy estimand. A separate programme in metabolic dysfunction-associated steatotic liver disease has drawn considerable attention, and survodutide holds FDA Fast Track and Breakthrough Therapy designations for MASH plus EMA Priority Medicine recognition. SYNCHRONIZE-2 is expected later in 2026. Like retatrutide, it is unapproved and has no reference pharmaceutical product.

What to check before you source any of them

Mechanism decides what you study. These five factors decide whether the material you receive supports the work.

A note on availability: of the five compounds above, we currently stock semaglutide, tirzepatide and cagrilintide. Retatrutide and survodutide are covered here as comparators because the mechanistic contrast is what makes the other three legible.

1. Whether an approved reference product exists. Semaglutide and tirzepatide have approved pharmaceutical counterparts, which means published analytical methods and established impurity profiles. Retatrutide, survodutide and cagrilintide do not. For the unapproved three, your confidence in identity rests entirely on the analytical documentation supplied — there is no external monograph to check against.

2. Whether the purity figure names its method. “99%+ pure” with no method attached is not a specification. HPLC area-percent purity, the column and gradient used, and the detection wavelength are the minimum. Area-percent under UV detection tells you what fraction of UV-absorbing material eluted as the main peak — it does not by itself confirm the peak is the compound you ordered. Mass spectrometry does that.

3. Whether identity was confirmed separately from purity. These are two different questions and they need two different answers. Purity says “one thing dominates”. Identity says “that thing is the molecule named on the vial”. For the acylated compounds — semaglutide, tirzepatide, retatrutide — this matters more than usual, because the lipid side chain affects chromatographic behaviour and related structures can co-elute.

4. Whether the COA is lot-specific. A single certificate reused across every shipment documents one historical batch, not the vial in front of you. The lot number on the vial should match the lot number on the certificate. Ours are published in the certificate of analysis library.

5. Whether the peptide content is stated. Lyophilized peptides are not pure peptide by mass — they carry counterions and residual water. Net peptide content is a distinct figure from chromatographic purity, and a material can be 99% pure by HPLC while being substantially less than 99% peptide by weight. If your work depends on accurate mass, you need both numbers.

Storage and handling

All five are supplied lyophilized, and all five are more stable in that state than in solution. General laboratory handling for lyophilized peptides of this class: store the sealed vial cold, protect from light, allow it to reach room temperature before opening to avoid condensation, and minimise freeze-thaw cycles on any reconstituted material. Reconstitution solvent choice depends on your assay, not on the compound’s category.

Ancillary materials — sterile water and antibacterial water — are stocked alongside in supplies and ancillary.

Frequently asked questions

Which of these is “best”?
The question does not have an answer at the compound level, because it depends entirely on what you are studying. If you need the deepest comparator literature, semaglutide. If the GIP pathway is your question, tirzepatide. If you are isolating the glucagon contribution, survodutide against retatrutide. If you are working outside the incretin axis, cagrilintide. Effect size in a weight-loss trial is not a proxy for research utility.

Why do the unapproved compounds cost less?
Different synthesis scales and no pharmaceutical supply chain. Price is not a quality signal in either direction here — analytical documentation is.

Are blends useful for research?
Sometimes, but they cost you a variable. A fixed-ratio blend is convenient and removes your ability to vary the ratio. For most designs, separate materials are the better choice.

Can you tell me how to use these?
No. These are laboratory research materials, not therapeutics, and we do not provide administration, dosing or protocol guidance of any kind. Nothing on this site should be read as describing human use. See our research-use policy.

What is the difference between purity and peptide content?
Purity is the proportion of the chromatographic signal attributable to the main peak. Peptide content is the proportion of the vial’s mass that is actually peptide, with the remainder being counterions and water. Both belong on a complete certificate.

Related

• The full retatrutide trial record
• Metabolic research compounds
• Certificate of analysis library
• How to order

Research Use Only. The compounds described are supplied solely for laboratory and in-vitro research. They are not drugs, foods, supplements or cosmetics, are not evaluated or approved by the FDA for any therapeutic use, and are not sold or intended for human or animal consumption or administration. This article summarises published preclinical and clinical-trial literature for scientific reference and does not describe, recommend or imply any human use, dose or health outcome.