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Research profile · Peptide analogue

Retatrutide

Also known as LY3437943, GGG tri-agonist

Early human — evidence level 3 of 4: Early human evidenceExperimental — UK regulatory status: Experimental — not authorised for human use in the UK

Overview

An investigational synthetic peptide studied as an agonist at the GIP, GLP-1 and glucagon receptors.

Category
Peptide analogue
Highest evidence level identified
Early human evidence
Last scientifically reviewed
19 August 2026
Last regulatory review
19 August 2026

Mechanism under investigation

Retatrutide is a synthetic single-peptide agonist reported to act at three receptors: the glucose-dependent insulinotropic polypeptide receptor, the glucagon-like peptide-1 receptor and the glucagon receptor. Structurally it is a GIP-based peptide backbone carrying a fatty-acid modification that extends its half-life. Published receptor pharmacology reports sub-nanomolar potency at all three human receptors, with relatively greater activity at the GIP receptor than at the other two.

Research areas

  • Metabolic research
  • Incretin biology

These are fields in which the compound has been investigated. Listing a field is not a statement that anything was demonstrated within it.

Current evidence

In-vitro evidence

Cells, tissues or biochemical systems outside a living organism.

Receptor binding and activation data at all three human target receptors were published in the discovery paper, which characterises the balance of agonism between the GIP, GLP-1 and glucagon receptors. This work describes what the molecule does in a controlled assay system and does not establish an effect in a living organism.

Animal evidence

Studies in living non-human animals.

Preclinical rodent characterisation appears in the same discovery publication, covering body-weight and glycaemic endpoints in obese rat models and hepatic lipid endpoints in mouse models. This rests on a single principal publication rather than a broad independent literature, and has not been widely replicated by unaffiliated groups.

Human observational evidence

Studies observing people without assigning an intervention.

No substantial published work exists at this level. Retatrutide is not authorised or prescribable in any jurisdiction, so there is no routine-care population to observe. Material sold online under this name is unregulated and its contents are unverified, so it generates no usable observational evidence.

Clinical-trial evidence

Studies assigning an intervention to human participants.

Peer-reviewed evidence reaches phase 2. A 48-week double-blind randomised placebo-controlled trial in adults with obesity, and a randomised phase 2a substudy in metabolic dysfunction-associated steatotic liver disease, have both been published. Phase 3 programmes are registered and several have completed, but their results have to date been communicated largely through sponsor announcements rather than peer-reviewed publication.

Study limitations

  • No peer-reviewed phase 3 publication exists. The largest results in public circulation are sponsor announcements, which have not undergone independent peer review or full data release.
  • Every human dataset is sponsor-run and sponsor-analysed, with no independent replication.
  • There is no observational or post-marketing evidence of any kind, so rare adverse events, long-term effects and behaviour in unselected populations are entirely uncharacterised.
  • Preclinical mechanistic work rests essentially on one discovery publication, so the animal evidence base is narrow and not independently corroborated.

UK regulatory context

Experimental — not authorised for human use in the UK

A compound appearing in research literature that holds no UK authorisation for human use in any indication.

Source: No summer shortcut for safe weight loss (opens gov.uk in a new tab) (Medicines and Healthcare products Regulatory Agency)

Regulatory classification is jurisdiction-specific. A compound authorised elsewhere is not thereby authorised in the UK, and a supplier’s description of a substance does not determine how it is classified in law. See safety and regulation for the framework and the authoritative sources.

Safety and interpretation

In the published phase 2 literature the most frequently reported adverse events were gastrointestinal — nausea, vomiting and diarrhoea — described as transient and generally mild to moderate, with frequency rising in higher dose groups. The phase 2a liver substudy reported serious adverse events in two of eighty treated participants and reported no hepatotoxicity signal through 48 weeks. Because no regulator has assessed the compound and no post-marketing surveillance exists, this characterisation should be regarded as provisional. The MHRA has separately warned that products sold as retatrutide in the UK are unregulated and may not contain what they claim.

References