What tirzepatide is
Tirzepatide is a synthetic lipidated 39-amino-acid peptide developed by Eli Lilly and Company under the developer code LY3298176 (WHO INN identifier 10849). It is a dual agonist of the glucose-dependent insulinotropic polypeptide receptor (GIPR) and the glucagon-like peptide-1 receptor (GLP-1R) — the so-called 'twincretin'. The molecule is engineered from the GIP backbone and shows greater relative activity at GIPR than at GLP-1R.
Tirzepatide is approved as a medicine under the brand names Mounjaro (type 2 diabetes) and Zepbound (obesity, and obstructive sleep apnoea), with approvals in Australia (December 2022), the United States and the European Union. This page is a molecular and scientific reference for researchers only. RetaLABS supplies a research-grade compound, which is a distinct category from the approved therapeutic product. Nothing here is medical advice, a treatment recommendation, or a claim of efficacy for any person. For an overview of the compound in a research context, see the tirzepatide research guide.
Key fact: Tirzepatide (LY3298176) is a 39-amino-acid dual GIP/GLP-1 receptor agonist peptide. CAS 2023788-19-2, formula C225H348N48O68, average MW ~4813 g/mol.
Molecular structure and sequence
Tirzepatide is a 39-residue peptide. Its one-letter amino acid sequence (where X denotes 2-aminoisobutyric acid, Aib) is:
YXEGTFTSDYSIXLDKIAQKAFVQWLIAGGPSSGAPPPS (X = Aib at positions 2 and 13)
Several engineered modifications define the structure:
- Aib substitutions at positions 2 and 13 (2-aminoisobutyric acid).
- Lysine-20 acylation: the side chain of the lysine at position 20 is acylated with a C20 fatty diacid (eicosanedioic acid), connected via a gamma-glutamate linker and two AEEA (2-[2-(2-aminoethoxy)ethoxy]acetic acid) spacers. This fatty-acid moiety enables albumin binding.
- C-terminal amidation: the C-terminus (Ser39) is amidated.
The fatty acid is a C20 diacid. The combination of the GIP-derived backbone, the two Aib residues, the C20 acyl chain on Lys20 and the amidated C-terminus together produce a peptide that is both proteolytically more stable and long-acting.
Physicochemical properties
The table below summarises the confirmed physicochemical and identifier data for tirzepatide. Every row is a confirmed reference value.
| Property | Value |
|---|---|
| Name | Tirzepatide |
| Developer code | LY3298176 |
| WHO INN identifier | 10849 |
| Developer | Eli Lilly and Company |
| Class | Synthetic lipidated 39-amino-acid peptide; dual GIP/GLP-1 receptor agonist |
| CAS Registry Number | 2023788-19-2 (parent / free form) |
| Molecular formula | C225H348N48O68 (free acid) |
| Average molecular weight | ~4813 g/mol |
| Monoisotopic mass | ~4810.52 Da (monoisotopic mass, not the average MW) |
| Peptide length | 39 amino acids |
| Plasma half-life | ~5 days (~5.4 days by population PK) |
| Route | Subcutaneous, once weekly |
| PubChem CID | 156588324 |
| DrugBank | DB15171 |
| ChEMBL | CHEMBL4297839 |
| UNII | OYN3CCI6QE |
| ChEBI | CHEBI:194186 |
The headline molecular weight is the average MW of approximately 4813 g/mol. The monoisotopic mass (~4810.52 Da) is listed separately and should not be confused with the average value. This page does not state solubility or storage specifications; for handling guidance, see the peptide reconstitution and storage guide.
Pharmacokinetics and half-life extension
Tirzepatide has a plasma half-life of approximately 5 days (about 5.4 days by population pharmacokinetics), supporting a once-weekly subcutaneous regimen. This extended half-life is a direct consequence of the structural engineering described above.
The key driver is the C20 fatty-diacid acylation at Lysine-20. The eicosanedioic-acid chain, linked through a gamma-glutamate and two AEEA spacers, promotes reversible binding to serum albumin. Albumin binding slows renal clearance and shields the peptide, extending circulation time well beyond that of an unmodified incretin peptide. The two Aib substitutions (positions 2 and 13) and C-terminal amidation further contribute to the molecule's stability profile. For more on how this maps to a research dosing schedule, see the tirzepatide dosing protocol.
Structure-to-mechanism: dual receptor agonism
Functionally, tirzepatide is a dual GIP/GLP-1 receptor agonist. The peptide is engineered from the GIP backbone and is sometimes described as a 'twincretin' because it engages both incretin receptors with a single molecule, showing greater relative activity at GIPR than at GLP-1R.
This dual-agonist architecture distinguishes tirzepatide from single-receptor incretin agonists and from triple agonists. For a structural comparison with another multi-receptor research peptide, see retatrutide vs tirzepatide research.
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