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Molecular Weight
Purity
Storage
Appearance
Solubility
01
Retatrutide (development code LY3437943) is a synthetic 39-residue peptide designed to activate three related receptors: the GIP receptor, the GLP-1 receptor and the glucagon receptor. This “triple agonist” profile sets it apart from single agonists such as semaglutide and from dual GIP/GLP-1 agonists such as tirzepatide.
Its backbone carries several non-standard residues, including two Aib residues and an α-methyl-leucine, and a C20 fatty diacid attached to Lys17 through a γ-glutamate–AEEA linker. The lipid enables binding to serum albumin and strongly affects how the peptide behaves in chromatography and in solution. It is supplied as a lyophilized reference material for in vitro research on multi-receptor peptide pharmacology and on the analysis of lipidated peptides.
02
Retatrutide’s 39 residues combine features from several incretin hormones with engineered modifications.
Tyr1 N-terminus
Like GIP and tirzepatide, Retatrutide begins with tyrosine rather than the histidine found in GLP-1 and glucagon.
Aib2 and Aib20
α-Aminoisobutyric acid at position 2 protects against DPP-IV, which would otherwise remove the first two residues. A second Aib at position 20 adds further backbone rigidity.
α-Methyl-leucine at position 13
An α-methylated residue that stabilises helical structure and reduces enzymatic cleavage.
Lipidated Lys17
The side-chain amine of Lys17 carries a C20 fatty diacid linked through γ-glutamic acid and an AEEA (aminoethoxyethoxyacetyl) spacer. This is the albumin-binding element and the main driver of the peptide’s hydrophobic behaviour.
C-terminal extension
The sequence ends in Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH₂, a proline-rich tail related to that of exendin-4, with an amidated C-terminus.
The peptide contains no methionine, cysteine or tryptophan, so its main chemical risks are deamidation of glutamine and changes to the lipid and linker.
03
Retatrutide is characterised in vitro by measuring binding and activation at each of its three receptors separately.
GIP receptor
Published data describe strong potency at the human GIP receptor, typically measured by cAMP accumulation in receptor-expressing cells and compared with native GIP and tirzepatide.
GLP-1 receptor
Activity at the GLP-1 receptor is measured in parallel assays and compared with GLP-1(7–36)-NH₂ and semaglutide.
Glucagon receptor
Activity at the glucagon receptor is the feature that distinguishes it from dual agonists. Published in vitro data show lower potency here than at the GIP receptor, giving an unbalanced, receptor-specific profile.
Assay considerations
Because the lipid binds albumin, measured potency can shift depending on the albumin or serum content of the assay buffer, so assay conditions must be reported carefully.
All receptor data described here come from cell-free and cell-based in vitro systems.
04
Multi-receptor pharmacology
A reference triple agonist for building potency profiles across the GIP, GLP-1 and glucagon receptors alongside single and dual agonists.
Lipidated peptide chromatography
Its C20 diacid makes it a demanding test compound for reversed-phase methods for acylated peptides.
Albumin-binding studies
Used to study how lipid modification and albumin content affect measured potency and free fraction in vitro.
Forced degradation
Stress studies track glutamine deamidation, linker or lipid modification and backbone cleavage to develop stability-indicating methods.
05
Storage
Store the lyophilized powder at −20 °C, sealed, desiccated and protected from light. Let the vial reach room temperature before opening.
Solubility and pH
Like other fatty-diacid peptides, Retatrutide is least soluble at mildly acidic pH, near its isoelectric point. DMSO, or a neutral to slightly basic aqueous buffer, dissolves it more readily; gentle sonication can help with concentrated stocks.
Aggregation
The lipid chain encourages self-association. Prepare stocks at moderate concentration and avoid vigorous shaking.
Surface adsorption
The hydrophobic lipid promotes sticking to plastics at low concentrations. Use low-binding polypropylene tubes and tips, and consider a carrier protein in dilute working solutions.
Solutions
Freeze single-use aliquots and avoid repeated freeze–thaw cycles.
06
Retatrutide combines the analytical challenges of a mid-sized peptide with those of a lipid conjugate.
HPLC
Wide-pore (300 Å) C4 or C8 columns are usually preferred to C18, which can retain the lipid very strongly. Raising column temperature and using a steeper organic gradient improve peak shape and recovery; the exact conditions are set during method development.
Mass spectrometry
ESI-MS shows multiply charged ions consistent with 4731.3 Da (for example +4 near m/z 1184 and +5 near m/z 947). Use formic acid rather than TFA for LC-MS to avoid signal suppression.
Lipid and linker confirmation
Peptide mapping with MS/MS of the fragment containing Lys17 confirms the attachment site and the C20 diacid–γGlu–AEEA linker. The non-acylated peptide is about 600 Da lighter and is monitored as an impurity.
Impurity profile
Typical checks include the des-lipid peptide, linker-truncated forms, glutamine deamidation (+1 Da), Aib/α-MeLeu-related deletion sequences and the free-acid C-terminus.
07
Tirzepatide activates the GIP and GLP-1 receptors; Retatrutide also activates the glucagon receptor. This third activity, with its own potency at each receptor, is what makes it a triple agonist.
Yes. It is registered under CAS 2381089-83-2, with molecular formula C₂₂₁H₃₄₂N₄₆O₆₈ and molecular weight 4731.3 g/mol.
It makes the peptide very hydrophobic, so it can retain strongly, tail, or be lost to the column on long-chain phases. Wide-pore C4 or C8 columns, elevated temperature and adjusted gradients are typically needed for good peak shape and recovery.
By peptide mapping: the peptide is digested, and the fragment containing Lys17 is analysed by LC-MS/MS. Its mass and fragment ions confirm the C20 diacid, the γ-glutamic acid and the AEEA spacer, and that they sit on Lys17.
There is no single universal value; it depends on the column, mobile phase and gradient. Elevated temperatures (often in the 40–60 °C range) generally improve peak shape for lipidated peptides, and the optimum is set during method development.
Fatty-diacid peptides are least soluble near their isoelectric point, which lies in the mildly acidic range. DMSO or a neutral to slightly basic buffer dissolves them more readily.
No. It is supplied strictly as a reference compound for laboratory and analytical research and is not for human or animal use.
Retatrutide Research Reference. (2026). Pure Peptides Labs Research Catalogue. Retrieved from https://purepeptideslabs.net/research-catalogue/metabolic-research-peptides/retatrutide/
Materials listed on this platform are supported by independent testing and published documentation for laboratory research contexts.
