Retatrutide – commonly referred to as GLP-3 in research and user communities – is a synthetic peptide belonging to the latest generation of incretin analogues and is described as a triple agonist: the molecule was engineered to bind to three different receptors – the GIP receptor, the GLP-1 receptor and the glucagon receptor. Conceptually, Retatrutide therefore goes one step further than dual agonists and represents the current state of peptide engineering in the metabolic research field.
Like other modern incretin analogues, Retatrutide is a chemically modified, lipidated peptide: a fatty acid side chain stabilises the molecule against enzymatic degradation. Retatrutide is in clinical development and is currently not approved as a medicinal product in any country. Outside clinical trials, the substance exists exclusively as reference and research material for laboratory purposes – and it is described here in precisely that capacity.
Profile
Molecule type: synthetic, lipidated peptide (incretin analogue)
Receptor profile (pharmacological classification): triple agonist at GIP, GLP-1 and glucagon receptors
Development status: in clinical development, no medicinal product approval
Research classification: reference and research material, research use only (RUO)
Why Retatrutide is called “GLP-3”
GLP-3 is neither an official substance name nor a receptor name. There is no GLP-3 receptor in the scientific literature: the endogenous peptides of the proglucagon family are GLP-1 and GLP-2, with GLP-2 acting at its own receptor related to the intestinal mucosa and having little to do with the incretin axis in the sense meant here. Instead, “GLP-3” is a collective term that emerged in research and user circles.
The numbering follows not the peptide family but the number of receptors addressed simultaneously. The first tier consists of pure GLP-1 agonists such as semaglutide, the second tier of dual GIP/GLP-1 agonists such as tirzepatide, and the third tier of triple agonists. Anyone searching for a GLP-3 peptide in practice always means Retatrutide – no other molecule currently carries this label. The full logic behind the numbering, including the terms GLP-4 and GLP-5 now in circulation, is set out in the article GLP-1 to “GLP-5”: what lies behind the numbering.
GLP-3 compared with GLP-1 and GIP/GLP-1 peptides
The three development tiers differ not in molecule class but in receptor profile:
- Semaglutide – one receptor (GLP-1). The longest-studied representative and the usual reference molecule in the literature when incretin signalling pathways are described. A component of approved, prescription-only medicinal products.
- Tirzepatide – two receptors (GIP and GLP-1). A dual agonist and therefore the second tier. Likewise a component of an approved medicinal product.
- Retatrutide – three receptors (GIP, GLP-1 and glucagon). The molecule referred to as “GLP-3”. It is in clinical testing and is not approved as a medicinal product in any country; outside clinical trials it exists exclusively as reference and research material.
For laboratory practice, one point follows above all: Retatrutide is the longest and most heavily modified of the three molecules, which makes analytical characterisation more demanding and increases the importance of a complete batch-related certificate of analysis (COA).
Research context
In metabolic research, Retatrutide is studied in connection with the question of how the simultaneous activation of three hormone receptors affects cellular signalling pathways and energy metabolism. Published preclinical work addresses receptor binding profiles, signal transduction in cell models and the pharmacology of multi-receptor agonists in animal models. These findings do not support conclusions about effects in humans.
In addition, the developer is running clinical study programmes whose results are published in specialist journals – these concern the medicinal product development programme and not the research material described here. For laboratories, Retatrutide is also relevant as an analytical test object, for example in method development for the characterisation of long, lipidated peptides. All research content named here is reported in neutral terms only.
Quality criteria for laboratory procurement
Because Retatrutide is a long, multiply modified peptide, analytical documentation is particularly important. A serious offer includes a batch-related certificate of analysis (COA) with HPLC purity determination and mass spectrometric identity testing that also confirms the correct side chain modification. The batch number on the label and on the certificate must match.
Storage corresponds to that of other lipidated research peptides: the lyophilisate is kept dry, cool and protected from light, and frozen for longer periods. Aliquoting protects the stock material from repeated temperature cycles and preserves material quality over the life of the project.
Frequently asked questions
Is Retatrutide legal?
Retatrutide is not approved as a medicinal product in any country. Procurement as reference and research material for scientific laboratory purposes is legally possible; any use in or on humans or animals is excluded. The respective national regulations for handling research chemicals apply.
What should be checked on the COA?
The three core elements of any batch documentation: an unambiguous batch number, an HPLC purity figure and mass spectrometric confirmation of the molecular mass. Particularly with a new, complex molecule such as Retatrutide, a complete batch-related certificate is the most important criterion for assessing a supplier.
How is Retatrutide stored?
As a lyophilisate: dry, dark and cool – frozen for long-term storage. Moisture and repeated thawing are to be avoided; in the laboratory, working with single aliquots is the established way to safeguard the integrity of the material.
Available from Peptélia
Peptélia supplies Retatrutide as batch-documented research material with a certificate of analysis (COA). The available nominal quantities – 5, 10, 15 and 20 mg as well as capsules – can be found in the Retatrutide GLP3 category. Each nominal quantity is available in packs of 1, 3, 5 and 10 vials.
How the nominal quantities compare in price – including converted to euros per milligram of active substance – is set out in the Retatrutide price and quantity comparison. The current phase 3 data are summarised in Retatrutide (GLP-3) trials 2026.
Important notice
All substances offered by Peptélia are intended exclusively for scientific use in the laboratory (research use only). They are not medicinal products, not food supplements and not cosmetics. Use in or on humans or animals, as well as any diagnostic or therapeutic use, is expressly excluded.
Distinction from approved medicinal products: Retatrutide is not approved as a medicinal product; related substances such as semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro) are components of prescription-only medicinal products that Peptélia does not distribute. This article is not a procurement or usage guide.
For research use only. Not for use in or on the human body.
