What is tirzepatide's mechanism of action?

Researchers describe it as a single peptide that activates two incretin receptors, GIP and GLP-1. In published studies this dual agonism was associated with glucose-dependent insulin secretion, lower glucagon, and reduced food intake.

Why is tirzepatide dosed once weekly in studies?

A C20 fatty-diacid chain binds albumin and slows degradation, giving an elimination half-life of about five days in pharmacokinetic analyses. Investigators used once-weekly subcutaneous dosing on that basis.

What is tirzepatide's molecular formula and weight?

Per PubChem (CID 156588324), the molecular formula is C225H348N48O68 with a molecular weight of about 4813.45 g/mol. Its CAS number is 2023788-19-2 and its InChIKey is AAPYRSPHYSKGIS-MCNPHUAVSA-N.

What did clinical studies report for tirzepatide?

In SURPASS-2 (type 2 diabetes), researchers reported HbA1c reductions of about 2.0–2.3% and weight reductions of 7.6–11.2 kg over 40 weeks. In SURMOUNT-1 (obesity), mean weight reductions of 16.0–22.5% over 72 weeks were reported. These are study findings, not outcomes promised to any individual.

Tirzepatide Dosage, Half-Life & Research

Tirzepatide is a 39-amino-acid synthetic peptide engineered as a dual agonist of the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors.¹ Built on a GIP backbone, it carries two non-coded aminoisobutyric acid (Aib) residues and a C20 fatty-diacid chain that binds albumin to extend its half-life to roughly five days, supporting once-weekly subcutaneous administration in studies.²⁵

Important context: tirzepatide is the active ingredient in approved prescription medicines (Mounjaro, Zepbound). Peptigo supplies tirzepatide strictly for laboratory research use only; it is not offered as a drug, and nothing here is a usage direction, medical advice, or a claim of clinical benefit. All figures below describe what investigators reported in published studies.

Structure

Sequence & identity

39-residue GIP-based analogue (Aib^2,13, C-terminal amide, Lys²⁰-linked C20 diacid) · C₂₂₅H₃₄₈N₄₈O₆₈ · 4813.45 g/mol

Lipidated, non-coded-residue-containing peptide — not a simple linear sequence. Identity per PubChem CID 156588324, InChIKey AAPYRSPHYSKGIS-MCNPHUAVSA-N.¹

What the research shows

Mechanisms studied

Researchers describe tirzepatide as a single molecule that engages two incretin receptors. The GIP-based peptide backbone was modified at positions 2 and 13 with aminoisobutyric acid and at the receptor-interaction region to confer cross-reactivity at the GLP-1 receptor, producing dual agonism.¹ In published mechanistic and clinical work, activation of both receptors was associated with glucose-dependent insulin secretion, reduced glucagon, and reduced food intake.³ A Lys²⁰-conjugated C20 fatty-diacid (via a γ-glutamate/2×AEEA linker) promotes albumin binding and resistance to proteolysis, which investigators report as the basis for its extended exposure and once-weekly profile.²⁵

Reported in studies

Dosing in the research literature

The figures below summarise regimens as reported in published research — they are not recommendations or directions for use.

Source / model	Regimen reported	Notes
Frías et al., NEJM 2021 (SURPASS-2)³	5, 10, or 15 mg once weekly, subcutaneous, after dose escalation (40-week trial)	Doses evaluated in adults with type 2 diabetes versus semaglutide 1 mg. Reported as a study regimen, not a usage direction.
Jastreboff et al., NEJM 2022 (SURMOUNT-1)⁴	5, 10, or 15 mg once weekly, subcutaneous, titrated from 2.5 mg (72-week trial)	Doses evaluated in adults with obesity/overweight versus placebo. Escalation schedule used to manage gastrointestinal effects in the trial.
Population PK analysis, Schneck & Urva 2024⁵	Once-weekly SC dosing; steady state ~4 weeks; ~5-day (≈120 h) elimination half-life	Two-compartment model with first-order absorption. The authors report no dose adjustment based on renal or hepatic impairment, body weight, sex, age, or race/ethnicity. Product labeling separately reports tirzepatide as ~99% bound to plasma albumin.⁷

Research use only. Peptigo products are sold to qualified researchers for laboratory use. This information summarises published research for reference and is not medical advice, a dosing recommendation, or directions for human or animal use.

Reported in studies

Effects observed in research

In randomized human trials, investigators reported large reductions in glycated haemoglobin and body weight. In SURPASS-2, the 5, 10, and 15 mg once-weekly doses produced mean HbA1c reductions of −2.01%, −2.24%, and −2.30% and body-weight reductions of −7.6, −9.3, and −11.2 kg over 40 weeks, exceeding semaglutide 1 mg on both measures.³ In the SURMOUNT-1 obesity trial, mean weight reductions at 72 weeks were 16.0%, 21.4%, and 22.5% for the 5, 10, and 15 mg doses versus 2.4% with placebo; 89–96% of participants on tirzepatide reached at least 5% weight loss versus 28% on placebo.⁴ The most commonly reported adverse events across studies were gastrointestinal (nausea, diarrhoea, vomiting), generally mild-to-moderate and most frequent during dose escalation.³⁴

Honest assessment

Strength of evidence

Grade A

Grade A. Tirzepatide is supported by multiple large, randomized, controlled human trials (the SURPASS and SURMOUNT programs), with endpoints in type 2 diabetes and obesity reported in peer-reviewed journals.³⁴ Chemical identity (formula, molar mass, InChIKey) is confirmed against PubChem, and CAS is documented in chemical registries.¹⁶ This is one of the better-evidenced compounds in this category. Note: robust clinical evidence reflects the approved pharmaceutical product; it does not change the fact that Peptigo offers tirzepatide for research use only, and the data above are not a basis for human use.

Handling

Reconstitution & storage

Reconstitute with bacteriostatic water for laboratory handling. Store lyophilised material frozen and reconstituted material refrigerated. Use Peptigo’s reconstitution calculator and storage cheat sheet for working figures.

References

PubChem Compound Summary, CID 156588324, Tirzepatide (MolecularFormula C225H348N48O68; MolecularWeight 4813; InChIKey AAPYRSPHYSKGIS-MCNPHUAVSA-N). National Library of Medicine. https://pubchem.ncbi.nlm.nih.gov/compound/156588324
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;18:3-14. doi:10.1016/j.molmet.2018.09.009
Frías JP, Davies MJ, Rosenstock J, et al.; SURPASS-2 Investigators. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. N Engl J Med. 2021;385(6):503-515. doi:10.1056/NEJMoa2107519
Jastreboff AM, Aronne LJ, Ahmad NN, et al.; SURMOUNT-1 Investigators. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038
Schneck K, Urva S. Population pharmacokinetics of the GIP/GLP-1 receptor agonist tirzepatide. CPT Pharmacometrics Syst Pharmacol. 2024;13(3):494-503. doi:10.1002/psp4.13099. PMID:38356317; PMCID:PMC10962491.
Tirzepatide, CAS 2023788-19-2. ChemicalBook / chemical registry record. https://www.chemicalbook.com/ChemicalProductProperty_EN_CB24869395.htm
MOUNJARO (tirzepatide) injection, US prescribing information, Clinical Pharmacology (plasma protein binding ~99%; steady state reached after 4 weeks). Eli Lilly and Company / FDA. https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/215866s000lbl.pdf

Written by the Peptigo Research Team · scientifically reviewed by Peter, Peptigo Research Team · Last reviewed June 2026. We cite primary literature and flag where evidence is limited. Our sourcing & RUO policy →