Retatrutide, also known as LY3437943, is a 39-residue lipidated peptide designed as a single-molecule agonist of the glucose-dependent insulinotropic polypeptide receptor (GIPR), glucagon-like peptide-1 receptor (GLP-1R), and glucagon receptor (GCGR). Its triple-receptor profile makes retatrutide a useful research tool for investigating multireceptor pharmacology, GPCR signaling, receptor selectivity, and structure–activity relationships.

The molecular design combines a modified peptide backbone with noncanonical amino acids, site-specific lipidation at Lys17, and C-terminal amidation. Two α-aminoisobutyric acid (Aib) residues and an α-methyl-leucine residue are incorporated into the sequence, while a C20 fatty diacid is attached to Lys17 through a γ-Glu/AEEA-containing linker.

This combination of backbone engineering and site-specific lipidation makes retatrutide particularly relevant to research on multireceptor peptide agonists, lipidated peptide chemistry, albumin association, peptide modification strategies, and analytical characterization of structurally complex peptides.

Alan Scientific supplies synthetic retatrutide for laboratory research with batch-specific analytical documentation, including HPLC and mass spectrometry data as applicable.

Certificates of Analysis (COAs) are batch-specific. Please contact us to request the COA for your product, and we will provide it by email.

Product Information

Retatrutide Sequence and Molecular Design

Sequence:

Y{Aib}QGTFTSDYSI{α-Me-Leu}LDK-Lys(AEEA-γGlu-C20 diacid)-AQ{Aib}AFIEYLLEGGPSSGAPPPS-NH₂

Retatrutide is structurally distinct from a conventional GLP-1 analog. Its molecular architecture combines receptor-active sequence engineering with multiple nonstandard structural features within a single peptide scaffold.

Two adjacent lysine residues occur at positions 16 and 17, with Lys17 carrying the lipid modification. Correct assignment of this modification site is important because a peptide containing the correct amino-acid backbone but lipidated at a different residue would represent a different molecular species.

The sequence also contains Aib at positions 2 and 20 and α-methyl-leucine at position 13. These noncanonical residues alter the chemical and conformational properties of the peptide relative to an all-natural amino-acid sequence and are integral components of the retatrutide molecular design.

C-terminal amidation provides another defined structural feature that should be considered together with peptide sequence, noncanonical residue incorporation, and lipidation when confirming product identity.

Triple-Receptor Pharmacology

Retatrutide is designed to interact with three class B G-protein-coupled receptors within a single peptide architecture.

Published pharmacological characterization has demonstrated activity at all three receptors, with comparatively strong GIPR activity and a more balanced relationship between GLP-1R and GCGR activity. The magnitude and relative potency observed at each receptor can vary with assay design, receptor expression level, species, and experimental system.

This receptor profile distinguishes retatrutide from single-receptor GLP-1 agonists and dual GIPR/GLP-1R agonists and makes the molecule useful for comparative studies of single-, dual-, and triple-receptor peptide pharmacology.

Why the Lys17 Lipid Modification Matters

The Lys17 lipid modification is part of the molecular identity of retatrutide, rather than an optional solubility or formulation feature.

A C20 fatty diacid is connected to the peptide through a γ-Glu/AEEA-containing linker at Lys17. The resulting modification substantially changes the physicochemical properties of the peptide compared with the corresponding non-lipidated backbone.

From a research and analytical perspective, lipidation can influence:

• hydrophobicity and chromatographic retention;

• interaction with albumin and other proteins;

• peptide solubility behavior;

• purification conditions;

• recovery during sample preparation;

• analytical method development.

These effects are particularly important when comparing retatrutide with non-lipidated analogs or with variants containing alternative fatty-acid chains, linkers, or attachment sites.

For scientists developing related lipidated peptides or modified receptor agonists, Alan Scientific's Custom Peptide Synthesis service supports project-specific sequences, noncanonical amino acids, linker designs, and peptide modifications.

Structural Features Relevant to Experimental Design

Retatrutide combines several structural variables that can be studied independently or together.

Noncanonical Amino Acids

Aib and α-Me-Leu introduce structural features that are not present in a conventional all-natural peptide sequence. Researchers comparing retatrutide-inspired analogs should therefore consider not only sequence substitutions but also the stereochemical and conformational consequences of these residues.

Site-Specific Lipidation

Attachment of the fatty-diacid moiety at a defined lysine residue creates a chemically distinct conjugated peptide. Positional isomers or incompletely modified material may have similar peptide backbones while differing substantially in chromatographic and functional behavior.

Linker Architecture

The γ-Glu/AEEA-containing linker separates the peptide backbone from the C20 lipid moiety. Linker length, polarity, orientation, and attachment chemistry are relevant variables for structure–activity and peptide-conjugation studies.

C-Terminal Amidation

Retatrutide contains a C-terminal amide rather than a free C-terminal carboxyl group. This distinction should be included when designing synthetic analogs and confirming molecular identity by mass spectrometry.

Research Applications

Retatrutide can be used as a research peptide in studies involving:

• GIPR, GLP-1R and GCGR receptor pharmacology;

• GPCR signaling and comparative receptor activation;

• multireceptor agonist characterization;

• ligand–receptor interaction studies;

• receptor selectivity and activity profiling;

• incretin-related signaling research;

• structure–activity relationship studies;

• noncanonical amino-acid incorporation;

• lipidated peptide design;

• fatty-acid and linker modification strategies;

• albumin-association studies;

• comparative analysis of single-, dual-, and triple-receptor peptide agonists;

• analytical method development for modified peptides.

Its combination of receptor-active sequence engineering and site-specific lipidation also makes retatrutide a useful reference structure for scientists designing related multireceptor or lipidated peptide analogs.

Quality Considerations for Synthetic Retatrutide

Retatrutide presents a more complex analytical problem than a conventional unmodified linear peptide.

A suitable quality assessment should consider several attributes together rather than relying exclusively on a single HPLC purity value.

Sequence Identity

The complete 39-residue sequence, including the two Aib residues and α-Me-Leu, should correspond to the intended molecular structure.

Modification Identity

The C20 fatty-diacid conjugate should be associated with the intended Lys17 modification site through the appropriate linker architecture.

Molecular Mass

Mass spectrometry provides an important orthogonal measurement supporting the molecular identity of the final peptide and its covalent modifications.

Chromatographic Purity

Analytical HPLC is useful for evaluating the relative abundance of the principal peptide component and detecting chromatographically resolved impurities.

However, HPLC purity alone does not establish complete molecular identity. Two species can exhibit similar chromatographic behavior while differing in sequence, modification state, oxidation, deletion products, or other structural attributes.

For a highly modified peptide such as retatrutide, molecular mass, chromatographic purity, sequence design, and modification identity should therefore be considered together.

More information about HPLC, mass spectrometry, and peptide analytical documentation is available through our Peptide Quality Control resource.

Purity and Experimental Planning

The appropriate peptide purity depends on the intended research workflow.

Exploratory analytical work or early method development may tolerate a different impurity profile from quantitative receptor assays, cell-based experiments, binding studies, or other sensitive biological workflows.

For modified peptides, researchers should consider more than the nominal HPLC percentage. Depending on the experiment, relevant specifications can include:

• molecular identity;

• modification identity;

• counterion or salt form;

• residual solvent profile;

• peptide content;

• water content;

• endotoxin requirements for sensitive biological workflows.

The practical objective is to select material with a specification appropriate for the experiment rather than treating the highest available HPLC percentage as the only measure of suitability.

Our Recommended Peptide Purity guide provides additional considerations for selecting peptide specifications for different research applications.

Retatrutide Analogs and Custom Synthesis

Research programs may require molecules related to retatrutide rather than the reference sequence itself.

Alan Scientific can support project-specific peptide designs involving modifications such as:

• amino-acid substitutions;

• noncanonical amino acids;

• alternative lipidation sites;

• different fatty-acid chains;

• modified linker architectures;

• C-terminal modifications;

• isotopic or fluorescent labels;

• related single-, dual-, or multireceptor peptide sequences.

For technically demanding lipidated peptides, sequence length alone is not an adequate measure of synthesis difficulty. Modification chemistry, hydrophobicity, aggregation tendency, purification behavior, and the required analytical specification should all be considered during project planning.

Researchers can contact our Custom Peptide Synthesis team for project-specific feasibility assessment and quotation.

Frequently Asked Questions

What receptors does retatrutide target?

Retatrutide is a single peptide agonist with activity at GIPR, GLP-1R and GCGR. This triple-receptor architecture distinguishes it from GLP-1R-only peptides and dual GIPR/GLP-1R agonists.

Is retatrutide correctly described as “GLP-3”?

No. “GLP-3” is not the name of a recognized receptor represented in retatrutide's pharmacological profile. Retatrutide is more accurately described as a GIPR/GLP-1R/GCGR triple-receptor agonist.

How many amino-acid residues are in retatrutide?

Retatrutide contains 39 amino-acid residues. Its sequence includes Aib at positions 2 and 20, α-Me-Leu at position 13, and a lipid-modified Lys17.

Why is Lys17 important in retatrutide?

Lys17 is the defined attachment site for the C20 fatty-diacid modification. Because the lipid attachment site forms part of the molecular structure, correct site-specific modification is an important identity attribute for synthetic research material.

Why is retatrutide lipidated?

The fatty-diacid conjugate increases the hydrophobic character of the peptide and supports reversible interactions with albumin. From a laboratory perspective, lipidation also influences purification, chromatographic behavior, solubility, and analytical method development.

Does high HPLC purity alone confirm retatrutide identity?

No. HPLC primarily provides information about chromatographic composition. For a peptide containing noncanonical residues, C-terminal amidation, and site-specific lipidation, mass spectrometry and confirmation of the intended molecular design are also important.

What makes synthetic retatrutide more challenging than a conventional linear peptide?

The combination of 39 residues, noncanonical amino acids, site-specific lipidation, a relatively hydrophobic fatty-diacid conjugate, and C-terminal amidation increases both synthetic and purification complexity. These features can also affect chromatographic behavior and analytical interpretation.

Can Alan Scientific support custom retatrutide-related analogs?

Yes. Alan Scientific's custom peptide synthesis service can support project-specific sequence variants, noncanonical amino acids, alternative lipidation strategies, linker modifications, and other research-oriented peptide designs. Feasibility and analytical requirements are evaluated according to the individual project.

Research Use Only

Retatrutide is supplied for research use only. It is not intended for therapeutic, or human use.