What Is Tirzepatide? Structure, Receptors and Research

Tirzepatide is a synthetic 39-amino-acid peptide that activates two incretin receptors: the GIP receptor and the GLP-1 receptor. It is built on the GIP sequence, and a C20 fatty diacid side chain binds albumin and extends its half-life to about five days. As a research compound it is central to work on dual incretin signalling; as a licensed medicine, it has a large body of phase 3 trial data.

For laboratory research use only. The compounds discussed are not approved for human or veterinary use and are not drugs, foods or cosmetics. This article summarises published research and is not medical advice.

Key points

39-residue peptide, 4813.53 Da, C₂₂₅H₃₄₈N₄₈O₆₈.
Based on the GIP sequence, with Aib at positions 2 and 13 and a lipidated Lys20.
Dual GIP/GLP-1 receptor agonist; development code LY3298176.
Human half-life about 5 days, driven by albumin binding.
Research material is supplied as lyophilized powder; handle as a lipidated, aggregation-prone peptide.

Quick facts

Property	Value
Length	39 amino acids, C-terminal amide
Molecular formula / weight	C₂₂₅H₃₄₈N₄₈O₆₈, 4813.53 Da
Backbone basis	GIP sequence
Non-natural residues	Aminoisobutyric acid (Aib) at positions 2 and 13
Lipidation	1,20-eicosanedioic acid (C20 diacid) on Lys20 via a linker
Targets	GIP receptor, GLP-1 receptor
Half-life (human)	~5 days

Structural details are from the U.S. prescribing information. Our tirzepatide research peptide is supplied as lyophilized powder in 5–60 mg vials, with HPLC and MS data for each lot.

Design: what each modification does

Feature	Purpose
Aib at position 2	Blocks cleavage by dipeptidyl peptidase-4 (DPP-4), which rapidly inactivates native GIP and GLP-1
Aib at position 13	Tunes receptor activity and helical structure
C20 fatty diacid on Lys20	Binds serum albumin, prolonging circulation
C-terminal amide	Protects against carboxypeptidase degradation

Native GLP-1 has a half-life of only minutes because of DPP-4 cleavage and renal clearance (Müller et al., 2019). Tirzepatide’s modifications address both problems, which is what makes once-weekly exposure possible.

Discovery

Lilly scientists described tirzepatide (then LY3298176) in 2018 as a fatty-acid-modified peptide designed to test whether adding GIP agonism improves on selective GLP-1 receptor agonists. In vitro it activated both receptors; in mice it lowered body weight and food intake and improved glucose tolerance. The phase 1 program included single and multiple ascending dose studies in healthy volunteers and a four-week proof-of-concept study in type 2 diabetes, using dulaglutide as a comparator (Coskun et al., 2018).

Pharmacokinetics

A population pharmacokinetic model built from 19 pooled studies described tirzepatide with a two-compartment model, first-order absorption and elimination, and a half-life of about 5 days. Covariate analysis did not suggest that adjustments for demographics or subpopulations were needed (Schneck et al., 2024). Our tirzepatide half-life article explains how this compares with other incretin peptides.

Phase 3 trial endpoints (SURMOUNT-1)

In SURMOUNT-1, 2539 adults with obesity (or overweight with a weight-related complication), excluding diabetes, were randomised to once-weekly tirzepatide at one of three dose levels or placebo for 72 weeks (Jastreboff et al., 2022).

Endpoint at week 72	Tirzepatide (range across dose groups)	Placebo
Mean % change in body weight	−15.0% to −20.9%	−3.1%
Participants with ≥5% reduction	85% to 91%	35%
Most common adverse events	Gastrointestinal, mostly mild to moderate

These are trial results for a licensed medicine under medical supervision. They describe the trial population and are not applicable to research material.

Handling research-grade tirzepatide

Lyophilized powder; store sealed at −20 °C, protected from light.
The licensed product is a clear, colourless to slightly yellow solution; reconstituted research material should look the same. See tirzepatide powder: appearance and testing.
As a lipidated peptide it can self-associate; swirl gently, do not shake, and avoid freeze–thaw. See how to reconstitute tirzepatide.
Use the peptide reconstitution calculator for concentrations.

Tirzepatide as a research tool

Beyond clinical use, tirzepatide is valuable in laboratory research because it combines GIP and GLP-1 receptor activity in one molecule with a well-characterised structure and pharmacokinetic profile. It is used to study incretin receptor signalling and receptor cross-talk, and as a reference compound when evaluating newer co-agonists such as retatrutide. Researchers comparing compounds should note that albumin in assay buffers binds the fatty diacid and can shift apparent potency, so buffer composition should be reported.

Open questions

What exactly does GIP receptor agonism add to GLP-1 receptor agonism? This remains an active research question in incretin biology.
How do outcomes differ in populations not well represented in the trials?

Related research

Frequently asked questions

Is tirzepatide a peptide?

Yes. Tirzepatide is a synthetic 39-amino-acid peptide based on the GIP sequence, with two aminoisobutyric acid (Aib) residues, a C-terminal amide and a C20 fatty diacid attached to lysine 20 through a linker. Its molecular weight is 4813.53 Da.

What receptors does tirzepatide act on?

It is a dual agonist of the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor.

What is the half-life of tirzepatide?

About 5 days in humans, according to a population pharmacokinetic model built from 19 pooled studies and the U.S. prescribing information.

Why does tirzepatide last so long?

The fatty diacid side chain binds serum albumin, which slows clearance and protects the peptide from rapid degradation.

What was tirzepatide's development code?

LY3298176. Its discovery and first clinical proof of concept were published in 2018.

References

DailyMed. Tirzepatide injection, solution — U.S. prescribing information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d2d7da5d-ad07-4228-955f-cf7e355c8cc0
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. Mol Metab. 2018. PMID: 30473097 https://pubmed.ncbi.nlm.nih.gov/30473097/
Schneck K, et al. Population pharmacokinetics of the GIP/GLP receptor agonist tirzepatide. CPT Pharmacometrics Syst Pharmacol. 2024. PMID: 38356317 https://pubmed.ncbi.nlm.nih.gov/38356317/
Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022. PMID: 35658024 https://pubmed.ncbi.nlm.nih.gov/35658024/
Müller TD, et al. Glucagon-like peptide 1 (GLP-1). Mol Metab. 2019. PMID: 31767182 https://pubmed.ncbi.nlm.nih.gov/31767182/
PubChem Compound Summary for CID 166567236, Tirzepatide. National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/166567236