What Are GLP-1 Research Peptides?

GLP-1 research peptides are a class of synthetic peptide analogues studied in the published biochemistry literature under the name glucagon-like peptide-1 (GLP-1) receptor agonists. This reference page describes the class chemically: what groups a compound into it, which peptides are named in the literature as members, and how each is documented by identity and purity testing. It is written for laboratory reference only and makes no claims about use.

What defines the GLP-1 research-peptide class chemically

The defining feature of the class is structural: each member is a synthetic peptide built around, or engineered to bind at, the glucagon-like peptide-1 receptor (GLP-1R), a receptor described in pharmacology databases such as PubChem. In the published literature these compounds are classified by their receptor-binding profile rather than by any single sequence.

• Single (selective) GLP-1R agonists — engineered to bind primarily one receptor.
• Dual agonists — reported to bind the GLP-1 receptor and the GIP receptor (GIPR).
• Triple agonists — reported to bind the GLP-1, GIP and glucagon (GCGR) receptors.

Chemically, the members are large peptides, typically in the range of roughly 30 to 40 amino-acid residues, with molecular weights near 4,000 to 4,900 g/mol. Several carry a fatty-acid (lipid) side chain attached to the peptide backbone, a structural modification documented in their chemical entries. Their size and modification are what distinguish them from short unmodified research peptides and what make identity confirmation by mass spectrometry a meaningful test.

Which compounds fall in the class

The following three compounds are the members most frequently referenced in the GLP-1 research-peptide literature. Each figure below is stated from its PubChem or CAS registry entry.

Semaglutide

Semaglutide (house code GLP1-SM) has CAS number 910463-68-2, molecular formula C₁₈₇H₂₉₁N₄₅O₅₉, and a molecular weight of approximately 4,113.6 g/mol (PubChem CID 56843331). It is classified in the literature as a selective GLP-1 receptor agonist and carries a lipid side chain on its peptide backbone.

Tirzepatide

Tirzepatide (house code GLP2-TZ) has CAS number 2023788-19-2, molecular formula C₂₂₅H₃₄₈N₄₈O₆₈, and a molecular weight of approximately 4,813.5 g/mol (PubChem CID 156588324). It is a 39-amino-acid, lipid-conjugated peptide described in the literature as a dual GIP and GLP-1 receptor agonist.

Retatrutide

Retatrutide (house code GLP3-RT) has CAS number 2381089-83-2, molecular formula C₂₂₁H₃₄₂N₄₆O₆₈, and a molecular weight of approximately 4,731.4 g/mol. It is a single-molecule 39-amino-acid peptide characterized in the literature as a triple agonist at the GIP, GLP-1 and glucagon receptors. The full identity set for these compounds is grouped in the GLP research peptide collection.

How GLP-1 research peptides are documented and tested

Because these peptides are large and chemically modified, two independent measurements establish that a vial contains what its label states: identity and purity.

• Identity is confirmed by mass spectrometry. Liquid chromatography–mass spectrometry (LC-MS) and high-resolution mass spectrometry (HRMS) measure the intact mass of the peptide, which can be checked against the calculated molecular weight from the formula. A measured mass matching the expected value within instrument tolerance confirms the peptide is the stated compound and not a substitution or truncation product.
• Purity is quantified by high-performance liquid chromatography (HPLC), which separates the main peptide from related impurities and reports the main peak as a percentage of the total.

Every batch is tested at the USC Alfred E. Mann Multi-Omics Mass Spectrometry Core, a university laboratory, by LC-MS and HRMS, and the resulting Certificate of Analysis (COA) is published per batch. Details of the methodology are set out on the quality and testing page.

How to read a Certificate of Analysis

A COA for a GLP-1 research peptide typically lists the compound name and batch number, the analytical methods used (for example LC-MS/HRMS for identity and HPLC for purity), the observed versus calculated mass, and the measured purity percentage. Reading a COA means checking three things: that the batch number on the certificate matches the vial, that the reported mass corresponds to the compound’s known molecular weight, and that the purity figure is stated with the method that produced it.

For laboratory research use only. Not for human or veterinary use.

Frequently asked questions

What are GLP-1 research peptides?

GLP-1 research peptides are synthetic peptide analogues classified in the published literature as glucagon-like peptide-1 (GLP-1) receptor agonists. Chemically they are large peptides, roughly 30 to 40 amino-acid residues with molecular weights near 4,000 to 4,900 g/mol, often carrying a fatty-acid side chain. The class is described here as a chemical and analytical category for laboratory reference only.

Which compounds are GLP-1 research peptides?

The three most frequently referenced members are semaglutide (GLP1-SM, CAS 910463-68-2), classified as a selective GLP-1 receptor agonist; tirzepatide (GLP2-TZ, CAS 2023788-19-2), classified as a dual GIP and GLP-1 receptor agonist; and retatrutide (GLP3-RT, CAS 2381089-83-2), classified as a triple GIP, GLP-1 and glucagon receptor agonist. These are structural and pharmacological classifications, not statements of use.

What is the CAS number and molecular weight of retatrutide?

Retatrutide (GLP3-RT) has CAS number 2381089-83-2, molecular formula C221H342N46O68, and a molecular weight of approximately 4,731.4 g/mol. It is a single-molecule 39-amino-acid peptide characterized in the literature as a triple receptor agonist. These figures are verified against its registry entry.

How is a GLP-1 research peptide's identity confirmed?

Identity is confirmed by mass spectrometry. Liquid chromatography–mass spectrometry (LC-MS) and high-resolution mass spectrometry (HRMS) measure the intact mass of the peptide, which is compared against the calculated molecular weight from its chemical formula. Purity is measured separately by HPLC. Livvmore has every batch tested at the USC Alfred E. Mann Multi-Omics Mass Spectrometry Core with a per-batch Certificate of Analysis.

What is the difference between a single, dual and triple agonist in this class?

The terms describe how many receptors a peptide is reported to bind in the literature. A selective agonist such as semaglutide binds primarily the GLP-1 receptor; a dual agonist such as tirzepatide binds the GLP-1 and GIP receptors; a triple agonist such as retatrutide binds the GLP-1, GIP and glucagon receptors. The distinction is a structural and pharmacological classification, not a statement of use.