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Research reference · updated October 15, 2026
What is tirzepatide? A research reference
Tirzepatide, development code LY3298176, is a synthetic peptide from Eli Lilly and Company that activates two receptors: the GIP receptor and the GLP-1 receptor. It is 39 amino acids long, built on the GIP sequence, with two non-coded residues and a C20 fatty diacid on lysine 20. It is the active ingredient of two FDA-approved medicines, Mounjaro and Zepbound; a research vial is neither of them. This page is the reference sheet, and each question has its own page below.
At a glance
| Name | Tirzepatide |
|---|---|
| Development code | LY3298176 |
| Chain length | 39 residues |
| Molecular formula | C225H348N48O68 |
| Molecular weight | 4,813 g/mol |
| PubChem record | CID 156588324 |
| Status | Active ingredient of FDA-approved Mounjaro (NDA 215866, 2022) and Zepbound (NDA 217806, 2023). Not on FDA’s drug shortage list; compounding enforcement discretion ended in 2025. Checked October 15, 2026. |
| Identifier | Value | Source |
|---|---|---|
| INN | tirzepatide (INN 10849) | FDA GSRS |
| FDA UNII | OYN3CCI6QE | FDA GSRS; Mounjaro label |
| CAS number | 2023788-19-2 | FDA GSRS |
| Molecular weight (label) | 4,813.53 Da | Mounjaro and Zepbound labels, section 11 |
| Monoisotopic mass | 4,810.52 Da | PubChem CID 156588324 |
| Receptor structures | PDB 7FIY, 7RBT (GIPR); 7FIM, 7RGP (GLP-1R) | RCSB Protein Data Bank |
Formula and weight are PubChem’s; the registry identifiers are FDA’s. The status line is dated and is rechecked on every filing, approval or FDA action.
The 39 residues
Tirzepatide is one chain of 39 amino acids. Four positions are not a plain coded amino acid: two aminoisobutyric acid (Aib) residues that the genetic code does not encode, a lysine carrying the fatty acid that binds albumin, and an amide at the end of the chain.
- 1Y
- 2Aib
- 3E
- 4G
- 5T
- 6F
- 7T
- 8S
- 9D
- 10Y
- 11S
- 12I
- 13Aib
- 14L
- 15D
- 16K
- 17I
- 18A
- 19Q
- 20K
- 21A
- 22F
- 23V
- 24Q
- 25W
- 26L
- 27I
- 28A
- 29G
- 30G
- 31P
- 32S
- 33S
- 34G
- 35A
- 36P
- 37P
- 38P
- 39S
Sequence and modifications from FDA’s Global Substance Registration System (UNII OYN3CCI6QE, record edited August 10, 2026) and section 11 of the Mounjaro label. GSRS’s plain one-letter string shows A and G at positions 2 and 13; its own modification table replaces both with Aib.
What tirzepatide is
Tirzepatide is a single synthetic peptide that is an agonist at two related receptors. Its label puts it in one sentence: "Tirzepatide is a GIP receptor and GLP-1 receptor agonist." It was first described in 2018 under its development code, in a Molecular Metabolism paper that called LY3298176 "a fatty acid modified peptide with dual GIP and GLP-1 receptor agonist activity." Semaglutide acts at one of those receptors; retatrutide adds a third.
It is registered with FDA's Global Substance Registration System as UNII OYN3CCI6QE, with CAS number 2023788-19-2. PubChem holds more than one record with its formula (CID 166567236 is another); the one titled tirzepatide is CID 156588324.
How it is built
- 39 residues "based on the GIP sequence", in the label's words.
- Two non-coded residues, aminoisobutyric acid at positions 2 and 13, which the label states directly.
- A C20 fatty diacid on lysine 20, joined through a γ-glutamic acid and two short ethylene-glycol units. The label says only "via a linker"; the linker chemistry is in FDA's substance registry.
- An amide at the C-terminus, so the chain ends in serinamide.
Its structures bound to both receptors were published in 2022, by a Shanghai group in Nature Communications and by Lilly in PNAS. The sequence, the job of each modification and what those structures show are in tirzepatide structure and sequence.
Where it stands
Tirzepatide is the active ingredient of two approved products. Mounjaro (NDA 215866) was approved on May 13, 2022 and Zepbound (NDA 217806) on November 8, 2023, both by Eli Lilly, and each has been supplemented since. FDA declared the tirzepatide shortage resolved, finally on December 19, 2024, and the windows in which pharmacies could compound it closed in February and March 2025. FDA has warned sellers whose research-labelled tirzepatide was, on the evidence of their own websites, meant for people. The approvals and the letters are dated in is tirzepatide FDA approved?, and compounding in what ended for compounded semaglutide and tirzepatide.
How it compares
Tirzepatide sits between semaglutide and retatrutide: a GIP-based peptide like retatrutide, active at two receptors where semaglutide reaches one and retatrutide three. The molecules side by side are on tirzepatide vs semaglutide and on the three-way comparison with retatrutide.
How it is tested
Every tirzepatide size listed here has a current laboratory certificate. Each reports identity by mass spectrometry, purity by reversed-phase HPLC, the measured milligrams in the vial, and screens for endotoxin, elemental impurities and sterility. How to read a tirzepatide certificate works through each line on these certificates, and the mass values a laboratory should see are further down this page.
What this site does not publish
A research vial labelled tirzepatide is not Mounjaro or Zepbound and cannot be represented as either. This reference and the pages it links to carry no clinical figures and no guidance of any kind on use, and the material listed is for laboratory research only. FDA's letters to research-labelled sellers show where that line is drawn; what FDA reads before calling a research product a drug sets it out.
Tirzepatide at FDA, dated
The main actions, each from Drugs@FDA, its approval letter or an FDA page, named by kind. Smaller labeling and manufacturing supplements are left out. What each approved product is indicated for is on its FDA label, linked in the sources, not repeated here.
Mounjaro approved, NDA 215866
Original approval of tirzepatide, a new molecular entity, under priority review.
FDA approval letterMounjaro authorised in the European Union
EMEA/H/C/005620, after a CHMP opinion of July 21, 2022.
European Medicines AgencyZepbound approved, NDA 217806
Second tirzepatide application, under priority review.
FDA approval letterZepbound: vial presentation added
Supplement S-003: a new presentation.
FDA approval letterFDA declares the tirzepatide shortage resolved
Remanded for re-evaluation on October 22, 2024, as part of litigation.
FDAWarning letter to a research-labelled seller
Summit Research Peptides: FDA quotes and rejects its “research use only” labelling.
FDA warning letterFDA re-determines the shortage resolved
Sets the end of enforcement discretion for compounders: February 18, 2025 (503A) and March 19, 2025 (503B).
FDAZepbound: new indication
Supplement S-013. The indication is on the label.
FDA approval letterCompounding window closes for 503A pharmacies
FDACompounding window closes for 503B outsourcing facilities
FDAMounjaro: indication extended to a new patient population
Supplement S-039.
FDA approval letterA further vial presentation added for both products
Mounjaro S-041 and Zepbound S-037.
FDA approval letterKwikPen added for both products
Mounjaro S-009 and Zepbound S-002: a new pen presentation in six strengths.
FDA approval letterFour warning letters name research-labelled tirzepatide
Gram Peptides, Pink Pony Peptides, Mile High Compounds and Prime Sciences. Code names such as “GLP-2 TRZ” did not change FDA’s reading.
FDA warning letter (Gram Peptides)Three more warning letters
Royal Peptides, Peptide Partners and Tex Peptides.
FDA warning letter (Royal Peptides)Mounjaro: new indication
Supplement S-044. The indication is on the label.
FDA approval letter
Certificates on file
| Material | Lot | Purity (RP-HPLC) | Issued |
|---|---|---|---|
| Tirzepatide 10 mg | TIR10-0803 | 99.80% | Aug 28, 2026 |
| Tirzepatide 20 mg | TIR20-0803 | 99.80% | Aug 28, 2026 |
| Tirzepatide 30 mg | TIR30-0803 | 99.85% | Aug 28, 2026 |
| Tirzepatide 60 mg | TIR60-0803 | 99.79% | Aug 28, 2026 |
| Tirzepatide 100 mg | TIR100-0803 | 99.85% | Aug 28, 2026 |
Each certificate is the testing laboratory’s own document, linked and never reproduced. How to read one line by line.
Every tirzepatide lot on file
All ten laboratory certificates held for tirzepatide, current and earlier, newest first. Measured content is the laboratory’s own quantitation of the vial, shown against the size on the label.
| Lot | Size | Issued | Purity (RP-HPLC) | Measured content | Identity | Status |
|---|---|---|---|---|---|---|
| TIR10-0803 | 10 mg | Aug 28, 2026 | 99.80% | 10.18 mg (101.8% of label) | LC-MS/MS: Conforms | Current |
| TIR20-0803 | 20 mg | Aug 28, 2026 | 99.80% | 20.77 mg (103.9% of label) | LC-MS/MS: Conforms | Current |
| TIR30-0803 | 30 mg | Aug 28, 2026 | 99.85% | 30.69 mg (102.3% of label) | LC-MS/MS: Conforms | Current |
| TIR60-0803 | 60 mg | Aug 28, 2026 | 99.79% | 61.11 mg (101.9% of label) | LC-MS/MS: Conforms | Current |
| TIR100-0803 | 100 mg | Aug 28, 2026 | 99.85% | 101.88 mg (101.9% of label) | LC-MS/MS: Conforms | Current |
| TIR100-0616 | 100 mg | Jul 7, 2026 | 99.9% | 101.25 mg (101.3% of label) | MALDI-MS: Conforms | Earlier lot |
| TIR10-0528 | 10 mg | Jun 17, 2026 | 99.9% | 10.42 mg (104.2% of label) | MALDI-MS: Conforms | Earlier lot |
| TIR20-0528 | 20 mg | Jun 17, 2026 | 99.9% | 20.38 mg (101.9% of label) | MALDI-MS: Conforms | Earlier lot |
| TIR600-0528 | 60 mg | Jun 17, 2026 | 99.9% | 60.57 mg (101.0% of label) | MALDI-MS: Conforms | Earlier lot |
| TIRZ10-0318 | 10 mg | Apr 3, 2026 | 99.8% | 11.06 mg (110.6% of label) | MALDI-MS: Conforms | Earlier lot |
Checking identity by mass spectrometry
An electrospray spectrum of tirzepatide shows the molecule carrying several protons at once. These are the values to look for, from the label formula C225H348N48O68 and the formula m/z = (M + z × 1.00728) / z.
| Ion | m/z from monoisotopic mass | m/z from average mass |
|---|---|---|
| [M+3H]3+ | 1604.52 | 1605.52 |
| [M+4H]4+ | 1203.64 | 1204.39 |
| [M+5H]5+ | 963.11 | 963.71 |
Arithmetic on PubChem’s monoisotopic mass (4,810.5249) and the label’s molecular weight (4,813.53). At this size the monoisotopic peak is not the tallest: check it at the low-mass edge of a resolved isotope envelope, and compare a low-resolution centroid with the average-mass column.
Tirzepatide on this site
Each page answers one question. Start with the one you came with.
- Is tirzepatide FDA approved? Mounjaro, Zepbound and research materialThe main FDA actions on tirzepatide, dated, and what FDA has said and done about tirzepatide sold for research.
- Tirzepatide structure and sequenceThe 39 residues, the two Aib positions, the lipid on lysine 20, and the published structures at both receptors.
- How to read a tirzepatide certificate of analysisIdentity, purity, content, endotoxin, metals and sterility, line by line, on the ten tirzepatide certificates on file.
- Tirzepatide vs semaglutideHow the two molecules differ in backbone, length, receptors, lipid, mass and approvals.
- Semaglutide vs tirzepatide vs retatrutideThe three incretin peptides side by side.
- Compounded semaglutide and tirzepatide: what ended and whenWhy compounding was allowed during the shortage, and the dates it ended.
- Tirzepatide research vialThe lyophilized research material in five sizes, with its specification and certificates.
Common questions
What is tirzepatide?
Tirzepatide (LY3298176) is a synthetic 39-residue peptide developed by Eli Lilly and Company that is an agonist at the GIP and GLP-1 receptors. It is the active ingredient of the FDA-approved products Mounjaro and Zepbound.
What does LY3298176 mean?
LY3298176 is Lilly’s development code for tirzepatide, used in the 2018 discovery paper and in the structure papers before the name was assigned. The two refer to the same molecule.
Is a tirzepatide research vial the same as Mounjaro or Zepbound?
No. Mounjaro and Zepbound are approved drug products, made and labelled under their FDA applications. A research vial contains the same peptide as a laboratory material, made to a research specification, and is not a drug product of any kind.
What is the molecular weight of tirzepatide?
4,813.53 Da, as stated in section 11 of the Mounjaro and Zepbound labels, for the formula C225H348N48O68. The monoisotopic mass, which matters on a high-resolution spectrum, is 4,810.52 Da.
What is the CAS number for tirzepatide?
2023788-19-2. Its FDA UNII is OYN3CCI6QE, and the PubChem record titled tirzepatide is CID 156588324.
Where are the tirzepatide certificates of analysis?
On this page, under Certificates on file and Every tirzepatide lot on file. All five sizes, 10, 20, 30, 60 and 100 mg, have a current certificate, and each links to its own page with the full readings and the laboratory’s verification number.
Sources
- MOUNJARO (tirzepatide) prescribing information, sections 11 and 12.1, revised 8/2026, DailyMed
- ZEPBOUND (tirzepatide) prescribing information, revised 8/2026, DailyMed
- Drugs@FDA: NDA 215866 (Mounjaro), read October 15, 2026
- Drugs@FDA: NDA 217806 (Zepbound), read October 15, 2026
- Tirzepatide, UNII OYN3CCI6QE, FDA Global Substance Registration System, edited August 10, 2026
- Tirzepatide, PubChem CID 156588324, National Library of Medicine
- Coskun T et al., LY3298176, a novel dual GIP and GLP-1 receptor agonist, Molecular Metabolism, 2018 (PubMed 30473097)
- Zhao F et al., cryo-EM structures of tirzepatide-bound GIPR and GLP-1R, Nature Communications, 2022 (PubMed 35217653)
- Sun B et al., Structural determinants of dual incretin receptor agonism by tirzepatide, PNAS, 2022 (PubMed 35333651)
- FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize, FDA, content current as of April 1, 2026
- FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss, FDA, content current as of October 1, 2026
- Mounjaro, EPAR, European Medicines Agency
For laboratory research use only. Not a drug, not a supplement, not for human or veterinary use.