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Metabolic researchSelected research

Tirzepatide

A fatty acid modified peptide that activates both the GIP and the GLP-1 receptor, characterized in cell-line signaling assays, in isolated islets, in mice, and in cryo-EM structures of both receptor complexes.

For in-vitro research only.Reviewed 2026-09-20

Key findings

  • Receptor occupancy calculated from signaling data showed greater engagement of the GIP receptor than of the GLP-1 receptor, which the authors describe as an imbalanced mechanism of action. [1]
  • At the GLP-1 receptor the peptide favored cAMP generation over beta-arrestin recruitment and drove receptor internalization more weakly than GLP-1, while at the GIP receptor it mimicked native GIP. [1]
  • Cryo-EM structures of the peptide bound to the GIP receptor and to the GLP-1 receptor showed both shared and distinct contacts, and the accompanying simulations attributed the mode of action to the fatty acid modification combined with the amino acid sequence. [2][3]
  • In mice the peptide lowered body weight and food intake more than a selective GLP-1 receptor agonist, and improved glucose tolerance by acting on both receptors. [4]

Identity and structure

Design
A fatty acid modified peptide with agonist activity at both the GIP and the GLP-1 receptor [4]
Development code
Described in the discovery report as LY3298176 [4]
Form as supplied
Sterile lyophilized powder

Mechanism as studied

The signaling work frames the molecule as imbalanced rather than equipotent. The authors calculated occupancy at each receptor and found more engagement of the GIP receptor, then showed that at the GLP-1 receptor the peptide is biased toward cAMP generation and away from beta-arrestin recruitment, with weaker receptor internalization than GLP-1 produces. [1]

Isolated islet experiments in the same report tie the bias to a specific step: beta-arrestin1 limited the insulin response to GLP-1 but not the response to GIP or to this peptide, which the authors read as the biased signaling contributing to the insulin secretion they measured. [1]

Two independent cryo-EM studies resolved the peptide in both incretin receptors. One compared the dual agonist with a triple agonist at the GIP, GLP-1 and glucagon receptors and reported common and unique features of each interaction; the other combined cryo-EM with molecular dynamics and concluded that the extent of fatty acid modification together with the amino acid sequence determines the mode of action of a multireceptor agonist. [2][3]

Research findings

In vitro
System
Cell lines expressing recombinant or endogenous incretin receptors
Measured
Signaling and functional responses at the GIP and GLP-1 receptors
Reported
The peptide activated signaling at both receptors in the same assay panel. [4]
In vitro
System
Signaling assays at the GIP receptor and the GLP-1 receptor, with occupancy calculated for each
Measured
Receptor occupancy, cAMP generation, beta-arrestin recruitment and receptor internalization, compared with native GIP and GLP-1
Reported
Engagement of the GIP receptor exceeded engagement of the GLP-1 receptor; the peptide mimicked native GIP at the GIP receptor but at the GLP-1 receptor favored cAMP over beta-arrestin recruitment and internalized the receptor more weakly than GLP-1. [1]
Ex vivo
System
Primary islets, including islets lacking beta-arrestin1
Measured
Insulin response to GLP-1, to GIP and to this peptide
Reported
Beta-arrestin1 limited the insulin response to GLP-1 but not the response to GIP or to this peptide. [1]
Preclinical in vivo
System
Mice; the material is the peptide as prepared by its originators rather than a catalog lot
Measured
Body weight, food intake, insulin secretion and glycemic profiles
Reported
Insulin secretion was glucose-dependent and glucose tolerance improved through both receptors; under chronic exposure body weight and food intake fell, significantly more than with a GLP-1 receptor agonist. [4]
Structural
System
Cryo-EM of the peptide bound to the GIP receptor and to the GLP-1 receptor, alongside a triple agonist bound to the GIP, GLP-1 and glucagon receptors
Measured
Near-atomic interactions of each peptide with each receptor
Reported
The structures revealed both features common to the two peptides and features unique to each, illustrating the key receptor contacts of the dual and the triple agonist. [2]
Structural
System
Cryo-EM combined with molecular dynamics simulations of the peptide at both incretin receptors
Measured
Receptor activation mode and agonist-induced receptor desensitization
Reported
The peptide closely resembled native GIP in how it activated the GIP receptor but differed markedly from GLP-1 at the GLP-1 receptor, with less agonist-induced desensitization; fatty acid modification combined with sequence determined the mode of action. [3]
Order Tirzepatide with the certificate for the lot that ships

Handling for in-vitro work

Assay comparators in the cited work
The signaling reports compare the peptide against native GIP and native GLP-1 in the same assay, so a comparator peptide is part of the method record [1]
Storage
Lyophilized at −20 °C, dark and dry; reconstituted aliquots kept cold and used promptly

Open questions

  • The two cryo-EM reports resolved different receptor complexes, and the cited work does not establish how the structures relate to the occupancy calculation made from the signaling data.
  • None of the cited work reports an analytical identity check that would distinguish this fatty acid modified peptide from a related incretin analogue in a supplied lot.
  • Whether the beta-arrestin1 result in isolated islets extends to other tissues expressing both receptors is not addressed in the cited work.

The discovery report and much of the later literature on this peptide is clinical and concerns a finished formulation; those sections are out of scope for a research material profile.

Lot records

Check the record for the exact material you order. A published paper and a batch certificate answer different questions.

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References

  1. Willard FS, Douros JD, Gabe MB, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI insight. 2020.

    PubMed 32730231 · doi:10.1172/jci.insight.140532

  2. Zhao F, Zhou Q, Cong Z, et al. Structural insights into multiplexed pharmacological actions of tirzepatide and peptide 20 at the GIP, GLP-1 or glucagon receptors. Nature communications. 2022.

    PubMed 35217653 · doi:10.1038/s41467-022-28683-0

  3. Sun B, Willard FS, Feng D, et al. Structural determinants of dual incretin receptor agonism by tirzepatide. Proceedings of the National Academy of Sciences of the United States of America. 2022.

    PubMed 35333651 · doi:10.1073/pnas.2116506119

  4. 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.

    PubMed 30473097 · doi:10.1016/j.molmet.2018.09.009

Publication records fetched from PubMed on 2026-09-20. Profile text reviewed 2026-09-20.