Retatrutide

At a glance

Strengths

5 mg, 10 mg, 15 mg, 20 mg, 30 mg, 15 mg dual pen and 30 mg dual pen

Also known as

LY3437943; LY-3437943; Triple G

CAS number

2381089-83-2

Molecular formula

C221H342N46O68

Molecular weight

4731 g/mol

Sequence

Y-Aib-QGTFTSDYSI-(alpha-Me-Leu)-LDK-K(gamma-Glu-AEEA-C20 diacid)-AQ-Aib-AFIEYLLEGGPSSGAPPPS-NH2 (39 residues; Lys17 acylated)

PubChem CID

171390338

What retatrutide is

Retatrutide is a single peptide that targets three receptors: the glucagon receptor (GCGR), the GIP receptor (GIPR) and the glucagon-like peptide-1 receptor (GLP-1R) ¹². The literature therefore calls it a triple agonist. Its development code is LY3437943, and structural and analytical papers give both names ²³. Eli Lilly is its developer and the sponsor of its phase 3 programme. Retatrutide is related to tirzepatide, which acts at GIPR and GLP-1R only. The two are different molecules, with different sequences, side chains and masses, so one cannot stand in for the other as a research material. In this catalogue the name refers to the single defined structure described in the next section, and every lot should be checked against that structure rather than against the name on the label.

Structure and chemical identity

The backbone has 39 amino acids and ends in a C-terminal amide. Three residues are not among the standard twenty: 2-aminoisobutyric acid (Aib) at positions 2 and 20, and alpha-methyl-leucine at position 13. The lysine at position 17 carries a fatty diacid attached through a linker ²; by its CAS index name, the side chain is built from a gamma-glutamic acid, one amino-ethoxy-ethoxy-acetic acid spacer and a 20-carbon diacid. PubChem holds the parent structure as CID 171390338, with the formula C221H342N46O68 and a molecular weight of 4731 g/mol. That record is titled "Triple G", and the substance records deposited under the name retatrutide map to it. The CAS number is 2381089-83-2, recorded both in PubChem and in FDA's substance registry. Synthesis has relied mainly on solid-phase peptide synthesis, and a liquid-phase route using a hydrophobic tag has also been reported ¹.

Regulatory status

Retatrutide is investigational: FDA has not approved it for any use, and Drugs@FDA held no application record for it when checked on October 2, 2026. Eli Lilly is the sponsor. On ClinicalTrials.gov, Lilly's phase 3 programme is registered under the name TRIUMPH. TRIUMPH-1 to TRIUMPH-4 were recorded as completed and TRIUMPH-5 to TRIUMPH-9 as active, not recruiting, at that check. The retatrutide sold here is a laboratory research material. FDA has not approved it, and it must not be used in people or animals.

Published research and registered studies

Published work on retatrutide falls into two groups: human trials run by the sponsor, and chemistry and analytical studies from other laboratories.

• Registered human studies. There are more than 30 registered studies, almost all sponsored by Lilly, covering phase 1, phase 2 and phase 3 (ClinicalTrials.gov, checked 3 October 2026).
• Trial reports. Phase 2 and phase 3 reports are indexed in PubMed. This page describes the compound, not those results.
• Synthesis (2026). A hydrophobic tag-assisted liquid-phase method was presented as an alternative to solid-phase synthesis ¹.
• Structural biology (2024). Cryo-electron microscopy structures of GLP-1R, GIPR and GCGR, each bound to retatrutide. The authors described conserved peptide and receptor contacts alongside receptor-specific conformations, particularly in extracellular loop 1 ².
• Analytical methods (2026). A liquid chromatography and high-resolution mass spectrometry method for retatrutide in plasma and urine, validated to World Anti-Doping Agency criteria ³, and a multiplexed method that identifies nine incretin-class peptides, retatrutide and tirzepatide among them ⁴.

What is not known

Most of the phase 3 programme was still active at the October 2026 registry check (ClinicalTrials.gov), so its results are still being reported. Trial reports do not establish the identity, purity or stability of research material from other manufacturers; each lot has to show those itself. A PubMed search found no stability study of lyophilised retatrutide. How the peptide degrades in the solid state, and which impurities dominate after storage, has not been described.

Laboratory storage and handling

Store each vial as stated on its certificate of analysis and product label, because no published stability data exist for the powder. The sequence has no methionine, cysteine or tryptophan, the residues most prone to oxidation, which leaves moisture and temperature as the main factors a laboratory controls. A cold vial should warm to room temperature while still closed, because a cold, open vial draws in moist air. Weighing out portions once, rather than opening the same vial many times, limits that exposure.

Quality testing

A certificate of analysis for retatrutide should confirm identity by mass spectrometry. The measured mass should match the expected value of about 4731 Da, which also separates retatrutide from tirzepatide at about 4813 Da. In the published plasma method, detection was based on the triply protonated ion, [M+3H]3+ ³. A multiplexed method combines accurate full-scan mass with fragment spectra for structural confirmation, and it identifies retatrutide, tirzepatide and seven related peptides in a single 20-minute run ⁴. Purity should be measured by reversed-phase HPLC, with the chromatogram and the integration method shown. Useful additions are peptide content as a percentage of the powder, the counter-ion and water content. For an acylated synthetic peptide, the most informative related impurities are truncated sequences and molecules missing the fatty diacid side chain. A good certificate states whether these were looked for. Purity figures belong to each batch and are reported on that batch's certificate, not on this page.