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Research / Tirzepatide review
Reference review

Tirzepatide: structure, dual GIP/GLP-1 mechanism and published research

Null Bio Lab Research Desk · Last reviewed October 18, 2026 · Research use only

Scope. This article summarises published laboratory literature for readers working with tirzepatide as a research reagent. It gives no dosing, administration or usage guidance, and nothing here is a statement about any use in humans or animals. Tirzepatide is an authorised prescription medicine under brand names such as Mounjaro and Zepbound. Research-grade reagent material is not that medicine and is not interchangeable with it.
Key facts
  • Class: dual GIP and GLP-1 receptor agonist
  • Size: 39 amino acids, about 4.81 kDa
  • Design: built on the native GIP sequence; two α-aminoisobutyric acid (Aib) residues; C-terminal amide; a C20 fatty diacid on Lys20 via a linker for albumin binding
  • Pharmacology: reported as “imbalanced” toward GIP receptor and “biased” at the GLP-1 receptor
  • Status: authorised medicine; research-grade reagent supplied here for laboratory use only

What tirzepatide is

Tirzepatide (research code LY3298176) is a synthetic 39-residue peptide that activates two incretin receptors, the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor.1 Its sequence follows native GIP, with substitutions that let it engage the GLP-1 receptor as well. For a plain comparison with a three-receptor agonist, see our retatrutide review.

Structure and lipidation

Two features explain the molecule's behaviour in the laboratory. First, Aib residues at positions 2 and 13 protect against N-terminal cleavage by dipeptidyl peptidase-4, which otherwise inactivates native incretins within minutes. Second, a C20 fatty diacid is attached to the Lys20 side chain through a short linker. That lipid binds serum albumin, which is the design basis for the long half-life reported for the molecule.1 Because the lipid moiety is part of the covalent structure, the measured mass of an authentic sample is about 4.81 kDa, far from what the bare 39-residue chain would give.

Receptor pharmacology

A JCI Insight study characterised tirzepatide against native GIP and GLP-1 in receptor assays and titled its findings accordingly: tirzepatide is an “imbalanced and biased” dual agonist.2 In the authors' account it acts at the GIP receptor with potency close to native GIP, while at the GLP-1 receptor it is weaker than native GLP-1 and favours cAMP signalling over β-arrestin recruitment. That bias is one of the main reasons tirzepatide is not simply “GIP plus GLP-1” in a single molecule.

Structural biology

Cryo-electron microscopy work resolved tirzepatide bound to both receptors and analysed which residues determine dual recognition.3 The study is the best source for how one peptide can adopt compatible poses at two related class B G protein-coupled receptors.

Mechanistic human studies

Alongside the preclinical work, a mechanistic clinical study in people with type 2 diabetes examined beta-cell function and insulin sensitivity under tirzepatide.4 We cite it as published mechanism research on an authorised medicine. This page does not describe treatment, and nothing here is guidance on use in people.

Limits of this page

  • Large registration trials exist for the authorised medicine; they concern the finished drug product and are outside the scope of a reagent reference.
  • Receptor-assay results depend on cell line, receptor species and readout, so potency ratios from one paper are not universal.
  • Research-grade material has no clinical-grade specification. Its identity and purity rest on the independent test report.

Regulatory status

Tirzepatide is authorised as a prescription medicine in the EU and US. Regulatory positions change, so confirm the current status with the relevant authority. Null Bio Lab supplies tirzepatide only as a laboratory research reagent, and the material is not the authorised medicinal product.

Verifying a batch

Check that the report shows a main-peak mass near 4.81 kDa (the deconvoluted value for the lipidated peptide, not the bare chain), HPLC purity, measured quantity, and a batch number matching the vial. Lipidated peptides can broaden on reverse-phase columns, so the chromatogram shape is worth reading as well as the percentage. See how to read a peptide COA. Reagent page: NB-Tirzepatide.

Frequently asked questions

What type of molecule is tirzepatide?

A 39-residue synthetic peptide with a C20 fatty diacid attached at Lys20. It activates both the GIP and GLP-1 receptors.

Why does tirzepatide have Aib residues?

Aib at positions 2 and 13 protects the N-terminus from DPP-4 cleavage, which inactivates native incretins quickly.

What does “biased agonist” mean here?

At the GLP-1 receptor, tirzepatide favours cAMP signalling over β-arrestin recruitment compared with native GLP-1, as reported in receptor assays.

Is research-grade tirzepatide the same as the medicine?

No. The authorised product is a regulated pharmaceutical. Research material is supplied for laboratory use only.

References

  1. Coskun T, 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. doi:10.1016/j.molmet.2018.09.009.
  2. Willard FS, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI Insight. 2020;5. doi:10.1172/jci.insight.140532.
  3. Sun B, et al. Structural determinants of dual incretin receptor agonism by tirzepatide. Proceedings of the National Academy of Sciences. 2022;119. doi:10.1073/pnas.2116506119.
  4. Thomas MK, et al. Dual GIP and GLP-1 receptor agonist tirzepatide improves beta-cell function and insulin sensitivity in type 2 diabetes. Journal of Clinical Endocrinology & Metabolism. 2021;106. doi:10.1210/clinem/dgaa863.

Related reading

For newly published papers on this and other peptides, see the live feed on the Research Desk.