Tirzepatide is a single 39-residue peptide that activates two different incretin receptors — the GIP receptor and the GLP-1 receptor — from one molecule. This guide covers the tirzepatide research peptide in depth: its GIP-derived backbone and engineered modifications, the receptor potency data that make it an imbalanced dual agonist, verified physicochemical identifiers, concentration references for solution preparation, and what a meaningful certificate of analysis must demonstrate.
Key takeaways
- Tirzepatide is a 39-residue synthetic peptide built on a GIP-derived backbone, not a GLP-1 backbone — a key distinction from semaglutide.
- It carries α-aminoisobutyric acid (Aib) at positions 2 and 13, a C20 fatty diacid on the lysine at position 20 via a γGlu–AEEA linker, and a C-terminal amide.
- Verified identity data: CAS 2023788-19-2, molecular formula C225H348N48O68, molecular weight approximately 4813 Da.
- Published receptor characterisation reports binding at GIPR comparable to native GIP (Ki 0.135 nM) but roughly five-fold weaker than native GLP-1 at GLP-1R (Ki 4.23 nM) — hence “imbalanced”.
- At GLP-1R, tirzepatide is biased towards G-protein signalling over β-arrestin recruitment, so it is not pharmacologically equivalent to combining two selective agonists.
- The reported half-life of the licensed pharmaceutical form is approximately 117 hours, about five days, supporting weekly administration in trials.
- Because tirzepatide is larger than semaglutide, an equal mass yields fewer moles — convert using MW 4813 Da whenever an assay is designed in molar terms.
What is the tirzepatide research peptide?
The tirzepatide research peptide is a synthetic 39-residue analogue that acts as a dual agonist at the glucose-dependent insulinotropic polypeptide receptor and the glucagon-like peptide-1 receptor, supplied as lyophilised powder for laboratory investigation. It was originally designated LY3298176 in the literature.
Its architecture is what makes it interesting as a research tool. Rather than starting from GLP-1 and adding GIP activity, the designers started from GIP and engineered in enough GLP-1 receptor recognition to activate that receptor as well. Coskun and colleagues described the discovery and initial characterisation in Molecular Metabolism in 2018.1
The consequence is a molecule that is genuinely dual but not symmetrically so. That asymmetry — near-native potency at one receptor and substantially reduced potency at the other, with a different signalling character at each — is the central fact any experiment involving tirzepatide has to account for.
Dual receptor mechanism: GIPR and GLP-1R
Both target receptors are class B G-protein-coupled receptors in the secretin family, and both couple predominantly to Gs, raising intracellular cyclic AMP. What differs is where each receptor is expressed and what downstream physiology has been attributed to it in published work.
The GLP-1 receptor arm contributes the pharmacology described for GLP-1 mono-agonists: glucose-dependent potentiation of insulin secretion at the beta cell, receptor populations in hindbrain and hypothalamic nuclei implicated in food-intake regulation, and modulation of gastric emptying.4
The GIP receptor arm is expressed in pancreatic islets, adipose tissue and at central sites. GIPR pharmacology has been more contested in the literature than GLP-1R pharmacology, and much of the interest in tirzepatide as a research compound stems from the opportunity to interrogate that receptor with a well-characterised agonist.
Why tirzepatide is called imbalanced and biased
“Imbalanced” and “biased” describe two separate phenomena, and tirzepatide displays both. Imbalance refers to unequal potency across its two target receptors. Bias refers to preferential engagement of some downstream effectors over others at a single receptor.
The imbalance was quantified in the discovery characterisation. At GIPR, tirzepatide’s binding affinity and cyclic AMP potency are close to those of native GIP. At GLP-1R, affinity is roughly five-fold lower than native GLP-1, and functional potency roughly thirteen-fold lower.1
The bias was demonstrated by Willard and colleagues, who reported that at GLP-1R tirzepatide favours G-protein coupling over β-arrestin recruitment relative to native GLP-1.2 Since β-arrestin recruitment drives receptor internalisation and desensitisation, a G-protein-biased agonist can sustain signalling differently over time from a balanced one.
Sun and colleagues then supplied the structural account, resolving how the GIP-derived scaffold makes the contacts needed to activate GLP-1R at all while remaining optimised for GIPR.3
Structure: 39 residues, Aib2, Aib13 and the C20 diacid
Tirzepatide is a 39-residue peptide with a C-terminal amide, built on a GIP-derived backbone and carrying three engineered features: two Aib substitutions, a fatty-diacid acylation, and the amidated C-terminus.
The two Aib substitutions
Aib at position 2 occupies the site that dipeptidyl peptidase-4 recognises, blocking enzymatic cleavage in the same way that Aib8 does in semaglutide (the numbering differs only because the GIP and GLP-1 backbones are numbered from different origins). Aib at position 13 sits within the peptide’s helical region, where its conformational rigidity stabilises the fold.
The C20 diacid and linker
The lysine at position 20 carries a twenty-carbon dicarboxylic acid attached through a γ-glutamic acid unit and AEEA spacers — the same linker architecture used in semaglutide, but with a longer fatty tail. A longer tail generally increases albumin affinity, which is one contributor to the extended persistence of the molecule.
Tirzepatide specification data
The identifiers below are the properties researchers use to confirm they have received the right compound. Always reconcile them against the batch certificate of analysis rather than the label alone.
| Property | Value |
|---|---|
| INN | Tirzepatide |
| Development code | LY3298176 |
| CAS number | 2023788-19-2 |
| Molecular formula | C225H348N48O68 |
| Molecular weight | ≈4813 Da |
| Residue count | 39 |
| Backbone origin | GIP-derived |
| Substitutions | Aib at positions 2 and 13 |
| Acylation | C20 fatty diacid at Lys20 |
| Linker | γ-glutamic acid + AEEA spacers |
| C-terminus | Amide |
| Receptor targets | GIPR and GLP-1R (both class B GPCRs) |
| Reported half-life (licensed form) | ≈117 h (≈5 days) |
| Physical form | White to off-white lyophilised powder |
| Appearance reconstituted | Clear, colourless solution |
| Parameter | GIP receptor | GLP-1 receptor | Interpretation |
|---|---|---|---|
| Binding affinity, Ki | 0.135 nM | 4.23 nM | Comparable to native GIP; ≈5× weaker than native GLP-1 |
| Functional potency, EC50 (cAMP) | 0.0224 nM | 0.934 nM | Near-native at GIPR; ≈13× weaker than native GLP-1 |
| Signalling character | Full-agonist behaviour reported | Biased towards G protein over β-arrestin | Not equivalent to two selective agonists combined |
| Receptor class | Class B GPCR | Class B GPCR | Both couple predominantly to Gs |
What published research reports
Tirzepatide has an unusually complete published record for a research peptide, spanning discovery chemistry, receptor pharmacology, structural biology and large randomised clinical trials of the licensed pharmaceutical form.
The discovery paper by Coskun and colleagues reported the receptor binding and potency data reproduced in Table 2, together with the phase 1 pharmacokinetic characterisation that established a mean half-life of approximately 117 hours.1 Willard and colleagues characterised the signalling bias at GLP-1R.2 Sun and colleagues resolved the structural basis of dual agonism.3
On the clinical side, the SURMOUNT-1 trial reported by Jastreboff and colleagues examined once-weekly tirzepatide in 2,539 adults over 72 weeks and reported mean changes in body weight ranging from −15.0% to −20.9% across the administered levels, against −3.1% in the placebo group.5 The SURPASS-2 trial reported by Frías and colleagues provided a direct randomised comparison against semaglutide in type 2 diabetes, with greater HbA1c reduction on tirzepatide across all administered levels.6
These clinical data describe the licensed pharmaceutical form under controlled conditions. They are cited here to explain why tirzepatide is a compound of research interest, not as any suggestion that a research-grade material behaves equivalently.
Reconstitution and concentration reference
Tirzepatide is handled exactly as other acylated incretin analogues are. The C20 tail makes it strongly surface-active, so foaming and adsorption are the dominant practical risks.
- Equilibrate the vial. Let the sealed vial reach ambient temperature before removing the flip cap to avoid condensation on the cake.
- Sanitise the stopper. Wipe with an alcohol swab and allow to dry fully before the first puncture.
- Add diluent down the wall. Deliver the measured volume slowly against the glass, never directly onto the lyophilised cake.
- Dissolve by gentle inversion. Rotate until clear. Shaking generates foam, and foam means lost monomer.
- Inspect for clarity. Discard any solution that is opalescent or contains visible particulates.
- Aliquot and label. Single-use volumes only, each labelled with compound, batch, mg/mL, diluent and date.
| Mass in vial | Diluent added | Concentration | Amount per 0.1 mL | Amount per 0.05 mL | Approx. molar concentration |
|---|---|---|---|---|---|
| 5 mg | 1.0 mL | 5.0 mg/mL | 500 mcg | 250 mcg | ≈1.04 mM |
| 5 mg | 2.0 mL | 2.5 mg/mL | 250 mcg | 125 mcg | ≈520 µM |
| 10 mg | 1.0 mL | 10.0 mg/mL | 1000 mcg | 500 mcg | ≈2.08 mM |
| 10 mg | 2.0 mL | 5.0 mg/mL | 500 mcg | 250 mcg | ≈1.04 mM |
| 10 mg | 2.5 mL | 4.0 mg/mL | 400 mcg | 200 mcg | ≈831 µM |
| 10 mg | 4.0 mL | 2.5 mg/mL | 250 mcg | 125 mcg | ≈520 µM |
| 15 mg | 3.0 mL | 5.0 mg/mL | 500 mcg | 250 mcg | ≈1.04 mM |
| 20 mg | 4.0 mL | 5.0 mg/mL | 500 mcg | 250 mcg | ≈1.04 mM |
Storage, stability and handling
The lyophilised powder is the stable form. Freeze-drying removes the water that drives hydrolytic degradation, so a sealed vial held cold and dark is far more robust than any solution prepared from it.
In solution, two categories of degradation compete. Chemical routes include deamidation of asparagine and glutamine residues, which accelerates at elevated pH, and hydrolysis at labile bonds. Physical routes are dominated by aggregation, driven here by the long C20 acyl chain, which is more hydrophobic than semaglutide’s C18 tail and correspondingly more prone to self-association.
Practical mitigations are straightforward. Keep the pH away from the peptide’s isoelectric region, avoid agitation entirely, use low-binding plastic for dilute working solutions, and never subject a working stock to repeated freeze–thaw. Our storage guide sets out stability windows by form and temperature.
Reading a tirzepatide certificate of analysis
Identity by mass is the decisive test for tirzepatide. The theoretical mass of approximately 4813 Da includes the C20 diacid and its linker; a batch that failed acylation, or that carries an incomplete linker, is several hundred daltons lighter while eluting close to the target on HPLC.
A useful certificate reports four things at minimum: appearance, reversed-phase HPLC purity with the chromatogram and stated method conditions, mass-spectrometric identity with the deconvolved mass, and a batch number tied to an analysis date. Net peptide content is a valuable fifth field, since it distinguishes peptide mass from counter-ion and residual water.
Be alert to two specific defects in this compound class. First, deletion sequences — a missing residue in a 39-mer changes the mass by 57 to 186 Da depending on which residue, comfortably resolvable by mass spectrometry. Second, incomplete C-terminal amidation, which leaves a free acid roughly 1 Da heavier and requires adequate instrument resolution to detect.
GenoPept publishes per-batch third-party certificates covering HPLC purity and mass-spectrometric identity at the COA certificates page; our guide to reading a COA explains each field in turn.
Tirzepatide in the GenoPept store
Frequently asked questions
What is tirzepatide and how does it differ from semaglutide?
Tirzepatide is a 39-residue dual agonist that activates both the GIP receptor and the GLP-1 receptor from a single molecule, built on a GIP-derived backbone. Semaglutide is a 31-residue GLP-1 mono-agonist built on a GLP-1 backbone. Tirzepatide is also heavier — roughly 4813 Da against 4113.6 Da — so equal masses give unequal molar amounts.
What is the molecular weight and CAS number of tirzepatide?
Tirzepatide has CAS number 2023788-19-2, molecular formula C225H348N48O68 and a molecular weight of approximately 4813 Da. That mass includes the C20 fatty diacid and its γGlu–AEEA linker. Confirming the deconvolved mass against this value is the most informative identity check available on a certificate of analysis.
Why is tirzepatide described as an imbalanced dual agonist?
Because its potency differs markedly between its two target receptors. Published characterisation reports a binding affinity at GIPR comparable to native GIP but roughly five-fold weaker than native GLP-1 at GLP-1R, with functional potency about thirteen-fold below native GLP-1. The two receptor arms are therefore engaged to different degrees at any given concentration.
What does biased agonism mean for tirzepatide?
At the GLP-1 receptor, tirzepatide preferentially drives G-protein coupling over β-arrestin recruitment compared with native GLP-1. Because β-arrestin recruitment governs receptor internalisation and desensitisation, a G-protein-biased agonist can sustain cyclic AMP signalling with a different time course from a balanced agonist at the same receptor.
How is tirzepatide reconstituted in the laboratory?
Bring the sealed vial to ambient temperature, sanitise the stopper, then add the measured diluent slowly down the inside wall rather than onto the cake. Dissolve by gentle inversion only — never shake or vortex, since foaming denatures peptide at the air–liquid interface. Inspect for clarity, then aliquot into single-use volumes and label each fully.
What is the half-life of tirzepatide?
The phase 1 pharmacokinetic characterisation of the licensed pharmaceutical form reported a mean half-life of approximately 117 hours, about five days, which is what supports weekly administration in clinical trials. The extended persistence comes from Aib at position 2 blocking DPP-4 cleavage and the C20 fatty diacid providing reversible serum albumin binding.
Does tirzepatide need refrigeration and how should it be stored?
Sealed lyophilised vials are normally held at 2–8 °C for medium-term storage and at −20 °C for long-term storage, protected from light in both cases, and tolerate short ambient periods in transit. Reconstituted solution is much less stable: refrigerate it, protect it from light, and never re-freeze a thawed aliquot.
Is tirzepatide from GenoPept suitable for human use?
No. Tirzepatide supplied by GenoPept is a research chemical intended for in-vitro laboratory and analytical work only. It is not a medicine, is not manufactured to pharmaceutical standards, and must not be used for human or veterinary purposes or for the diagnosis, treatment or prevention of any condition. Purchasers must be qualified researchers or institutions.
References
- Coskun T, Sloop KW, Loghin C, et al. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: from discovery to clinical proof of concept. Molecular Metabolism. 2018;18:3–14. PubMed
- Willard FS, Douros JD, Gabe MB, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI Insight. 2020;5:e140532. PubMed
- Sun B, Willard FS, Feng D, et al. Structural determinants of dual incretin receptor agonism by tirzepatide. Proceedings of the National Academy of Sciences. 2022;119(13):e2116506119. Publisher
- Drucker DJ. Mechanisms of Action and Therapeutic Application of Glucagon-like Peptide-1. Cell Metabolism. 2018;27(4):740–756. PubMed
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022;387(3):205–216. PubMed
- Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine. 2021;385:503–515. PubMed
- Lau J, Bloch P, Schäffer L, et al. Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide. Journal of Medicinal Chemistry. 2015;58(18):7370–7380. Publisher
Research-grade tirzepatide, batch-verified
GenoPept supplies tirzepatide as lyophilised vials with a per-batch third-party certificate of analysis covering HPLC purity and mass-spectrometric identity, dispatched from the UK strictly for laboratory research.