Short answer: tirzepatide (LY3298176) is a 39-amino-acid synthetic peptide developed by Eli Lilly, the first dual agonist in its class - it simultaneously activates both the GLP-1 and GIP receptors. It is FDA-approved as Mounjaro (type-2 diabetes) and Zepbound (chronic weight management), with the head-to-head SURMOUNT-5 trial showing a greater mean weight reduction over 72 weeks than once-weekly semaglutide. New-U catalogues research-grade tirzepatide as GLP-1 RC-T - lyophilised reference peptide, sealed vials, per-batch CoA, research use only.
Tirzepatide is the single most-searched peptide on the internet in 2026, with roughly 1 million monthly Google queries in the United States alone - nearly double the next compound in the category. That demand sits across two distinct populations: clinicians prescribing the approved branded product (Mounjaro, Zepbound), and the research community studying the underlying 39-amino-acid molecule. This guide is for the latter. It explains the mechanism, summarises the pivotal Phase 3 evidence (SURPASS, SURMOUNT, SURMOUNT-5), and frames what tirzepatide looks like as a research reference compound - catalogued on our site as GLP-1 RC-T. For the broader GLP-1 class explainer see Is Ozempic a Peptide?; for the side-by-side single-vs-dual mechanism comparison see GLP-1 RC-S vs GLP-1 RC-T.
Plain-English summary. Tirzepatide is an approved medicine in the United States, the United Kingdom and many other jurisdictions when supplied through licensed channels as Mounjaro or Zepbound. Research-grade tirzepatide, sold as a lyophilised reference peptide for laboratory use, is a separate non-medicine category. New-U sells only the research reagent - not the medicine - with no human-use claims, no dosing guidance and no therapeutic protocol. This page is general information, not legal or medical advice.
Tirzepatide, developmental code LY3298176, is a 39-amino-acid synthetic peptide modelled on the native GIP backbone. A C20 fatty acid is attached via a γ-Glu-2xOEG linker at Lys20; that lipid tail drives reversible albumin binding, which extends the half-life to roughly 5 days. The long half-life is what enables once-weekly subcutaneous administration in the licensed product. Structurally, tirzepatide is not a GLP-1 analogue with a GIP feature bolted on - it is a GIP-derived sequence engineered to acquire potent GLP-1 receptor binding while retaining native GIP activity.
That dual-agonist property is the entire point. GLP-1 and GIP are the two principal incretins - gut-derived hormones released after a meal that potentiate glucose-dependent insulin secretion. Native GIP loses activity in type-2 diabetes; restoring GIP-receptor signalling alongside GLP-1 activation is hypothesised to be the mechanistic reason tirzepatide produces larger metabolic effects than GLP-1 mono-agonists. The full mechanism is reviewed in the StatPearls tirzepatide chapter.
Tirzepatide does four things simultaneously:
The dual GIP arm adds an additional set of effects on adipose tissue glucose handling and energy expenditure. The net result, as documented in the Phase 3 programme, is a larger mean body-weight reduction than any approved GLP-1 mono-agonist had previously demonstrated.
Tirzepatide’s approval rests on two trial programmes:
SURPASS (type-2 diabetes, n > 13,000 across SURPASS-1 through SURPASS-6). At the 15 mg weekly dose, tirzepatide produced HbA1c reductions of ~2.1–2.4% from baseline, larger than insulin glargine and larger than semaglutide 1.0 mg in the SURPASS-2 head-to-head.
SURMOUNT (chronic weight management). SURMOUNT-1 reported mean weight reduction of ~20.9% at the 15 mg dose over 72 weeks in adults with obesity without diabetes, with a placebo-corrected difference of around 17.8 percentage points - the largest effect ever recorded for a single pharmacological agent in an obesity trial at the time of publication.
The head-to-head SURMOUNT-5 trial (NEJM, 2025) compared tirzepatide and semaglutide directly over 72 weeks. Tirzepatide produced a significantly greater mean reduction in body weight than semaglutide, with the magnitude of the difference roughly mirroring what the cross-trial comparisons had already suggested.
The incretin landscape now spans three receptor profiles and three approval stages:
| Compound | Receptor profile | Amino acids | Status |
|---|---|---|---|
| Semaglutide GLP-1 RC-S |
GLP-1 only (mono-agonist) | 31 | Approved (Ozempic, Wegovy, Rybelsus) |
| Tirzepatide GLP-1 RC-T |
GLP-1 + GIP (dual agonist) | 39 | Approved (Mounjaro, Zepbound) |
| Retatrutide GLP-1 RC-R |
GLP-1 + GIP + glucagon (triple agonist) | 39 | Phase 3, no approval |
Each step up the agonist count adds an additional metabolic pathway: semaglutide acts on GLP-1 alone; tirzepatide adds GIP-receptor signalling; retatrutide adds glucagon-receptor agonism, which contributes hepatic thermogenesis and an additional energy-expenditure arm. For the regulatory framing of each one in the UK specifically, see Where to Buy Retatrutide in the UK.
Native GLP-1 has a circulating half-life of roughly 2 minutes - it is degraded almost instantly by DPP-4. Tirzepatide gets to ~5 days by a combination of three engineering choices: (1) the C20 fatty acid for albumin binding, (2) Aib substitutions at residues 2 and 13 that block DPP-4 cleavage, and (3) the γ-Glu-2xOEG linker that positions the fatty acid for optimal albumin affinity. Steady-state plasma concentration is reached after roughly 4 weeks of weekly dosing.
On the New-U catalogue, the research-grade reference peptide is listed under the research-compound code GLP-1 RC-T. Same 39-amino-acid sequence, same dual GLP-1/GIP receptor mechanism, same molecule that Eli Lilly studies as LY3298176 - the “RC-T” code is the research-compound naming convention used for our incretin reference range. The product is a sealed glass vial of lyophilised peptide for laboratory use only.
The reason for the research-compound posture is the same reason it matters everywhere else in this catalogue: a peptide marketed for human use is a medicine, and selling an unapproved medicine is the line both the FDA and MHRA actually enforce. A lyophilised reference peptide labelled research use only, not for human consumption sits in a separate, lawful category. See Are Peptides Legal? for the US framing and Are Peptides Legal in the UK? for the UK.
For a 39-amino-acid peptide with a fatty acid tail, the purity questions are:
Our walkthrough of every line item is in How to Read a Certificate of Analysis.
The same scam patterns appear across the entire GLP-1 cluster. Walk away from any tirzepatide listing that:
Lyophilised tirzepatide is robust at standard freezer temperatures but should be handled like the long-chain modified peptide it is. Keep sealed vials at −20°C for long-term storage. Allow vials to reach room temperature before opening so condensation does not enter the vial. Reconstitute only the volume needed; once reconstituted, store at 2–8°C and protect from light. Our full handling reference is in How to Store Peptides.
What is tirzepatide?
A 39-amino-acid synthetic peptide developed by Eli Lilly (developmental code LY3298176). It is a dual agonist of the GLP-1 and GIP receptors, marketed as Mounjaro for type-2 diabetes and Zepbound for chronic weight management.
How is tirzepatide different from semaglutide?
Semaglutide is a single GLP-1 agonist. Tirzepatide adds GIP-receptor agonism - the “dual” in dual incretin agonist. In SURMOUNT-5 (NEJM, 2025) tirzepatide produced a significantly greater mean weight reduction than semaglutide over 72 weeks.
What is tirzepatide’s half-life?
Approximately 5 days, enabling once-weekly subcutaneous dosing. The long half-life comes from a C20 fatty acid moiety that drives reversible albumin binding.
Is tirzepatide a research compound on this site?
Yes. New-U catalogues research-grade tirzepatide as GLP-1 RC-T, lyophilised reference peptide with a per-batch Certificate of Analysis. Sold research use only, not for human consumption.
How do I verify tirzepatide purity?
Demand a per-batch CoA showing >99% HPLC purity and a mass-spec identity match to the calculated monoisotopic mass, from a named third-party lab. See how to read a CoA.
External links are provided for research reference only; New-U is not affiliated with the cited organisations and links carry no endorsement either way. Mounjaro and Zepbound are trade names of Eli Lilly and Company; New-U sells research-grade reference peptide only, not the licensed medicine.
New-U Research Compounds catalogues tirzepatide as GLP-1 RC-T - sealed 10-vial packs of lyophilised reference peptide, independently verified by Janoshik and Freedom Diagnostics for >99% HPLC purity, with a per-batch Certificate of Analysis. Tracked worldwide delivery. Research use only - not for human consumption.
View GLP-1 RC-T (tirzepatide)