Tirzepatide
Mounjaro · Zepbound · LY3298176 · tirzepatide injection · tirz · tizepeptide
Coming soon
What Tirzepatide is
Tirzepatide is a 39-amino-acid synthetic peptide built on the sequence of GIP, a gut hormone, and designed to act on both the GIP and GLP-1 receptors. It was developed by Eli Lilly under the code LY3298176. Two of its residues are non-standard (Aib), its C-terminus is amidated, and a long fatty-acid chain is attached to one lysine so that the molecule binds albumin and stays in circulation longer. That combination makes it a harder molecule to make, and to verify, than an unmodified peptide.
Tirzepatide is an FDA-approved prescription drug, sold as Mounjaro and Zepbound, and it has a large body of randomized-trial evidence behind those approvals. Products sold outside that approved supply chain are a different matter: FDA does not review compounded drugs for safety, effectiveness or quality, and it has warned sellers marketing tirzepatide as "for research purposes" or "not for human consumption." Because the trial evidence applies to the approved product, not to vials from other sources, independent lot testing is the only way to know whether a given vial contains tirzepatide, how much, and what else is in it.
| Sequence | Tyr-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Ile-Aib-Leu-Asp-Lys-Ile-Ala-Gln-Lys(γGlu-2xOEG-C20 diacid)-Ala-Phe-Val-Gln-Trp-Leu-Ile-Ala-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH2 |
|---|---|
| One-letter code | Y[Aib]EGTFTSDYSI[Aib]LDKIAQK*AFVQWLIAGGPSSGAPPPS-NH2 (K* = acylated Lys20) |
| Length | 39 amino acids |
| Molecular formula | C225H348N48O68 |
| Molecular weight | ≈4813.53 Da |
| Expected m/z | [set when the lab validates the method] |
Modifications and look-alikes
Modifications
Two non-coded residues: alpha-aminoisobutyric acid (Aib) at positions 2 and 13. Lys20 side chain acylated with a C20 fatty diacid (1,20-eicosanedioic acid) through a linker; GSRS describes the substituted residue as N6-(N-(hydrogen icosanedioyl)-gamma-Glu-bis(iminobis(ethylenoxy)acetyl))-lysine, i.e. gamma-glutamate plus two 8-amino-3,6-dioxaoctanoic acid (OEG) units. C-terminal serine is amidated. The unmodified backbone (GSRS) reads YAEGTFTSDYSIGLDKIAQKAFVQWLIAGGPSSGAPPPS, with Aib replacing residues 2 and 13.
What it gets confused with
(1) Reported molecular weight differs by source: 4813.53 Da (FDA Mounjaro label) vs 4810.52 Da (Coskun et al. 2018 discovery paper; DrugBank). Same formula in both, so the gap is a calculation convention, not a different molecule; confirm which value the lab's method uses. (2) Bulk API sold as "research" material may be a salt (e.g. acetate or TFA); the counterion adds to weighed mass and lowers peptide content per mg, but does not change the peptide's measured mass by LC-MS. (3) FDA has warned sellers of semaglutide, tirzepatide and retatrutide falsely labeled "for research purposes" or "not for human consumption"; vials sold as tirzepatide can contain a different GLP-1 analog, so identity must be confirmed by mass, not label. (4) Compounded tirzepatide is often combined with vitamin B12 analogs; a reaction product between the two has been reported (PMID 42010938).
Identity sources: accessdata.fda.gov · doi.org · gsrs.ncats.nih.gov · go.drugbank.com
Regulatory status. FDA-approved prescription drug: Mounjaro (tirzepatide) for adults with type 2 diabetes, and Zepbound (tirzepatide) for chronic weight management, approved November 8, 2023 (https://www.fda.gov/news-events/press-announcements/fda-approves-new-medication-chronic-weight-management). FDA determined on December 19, 2024 that the tirzepatide injection shortage, which began in December 2022, is resolved, with enforcement discretion for 503A compounders running until February 2025 and for 503B outsourcing facilities until March 19, 2025 (https://www.fda.gov/media/185577/download). FDA states that compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before marketing, and that it has warned companies illegally selling unapproved tirzepatide falsely labeled 'for research purposes' or 'not for human consumption' (https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss).
Read the research summary and referencesTirzepatide test results
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Vialidate Labs reports analytical results only. Nothing on this page is medical advice or a recommendation to use any compound.