Tirzepatide (LY3298176) is a synthetic, fatty-acid-conjugated long-acting peptide developed by Eli Lilly as the first-in-class dual agonist of the GIP and GLP-1 receptors. By engaging both incretin systems in a single molecule, it drives greater metabolic effect than the selective GLP-1 agonists that preceded it — combining potent appetite suppression and glucose-dependent insulin secretion with the complementary adipose and insulinotropic activity of GIP. Marketed as Mounjaro and Zepbound, it is the benchmark against which the newer triple agonists are measured.
Tirzepatide (LY3298176) is a first-in-class, once-weekly dual agonist of the GIP and GLP-1 receptors developed by Eli Lilly and marketed as Mounjaro (type 2 diabetes) and Zepbound (chronic weight management). In the Phase 3 SURMOUNT-1 obesity trial (NEJM, 2022; n=2539) it produced 16.0–22.5% mean body-weight reduction at 72 weeks, and in the SURPASS diabetes programme it outperformed once-weekly semaglutide on glycaemic control (SURPASS-2). Its differentiator is the addition of GIP-receptor agonism alongside GLP-1, giving greater effect than selective GLP-1 agonists. It has a ~5-day half-life, is a fatty-acid-conjugated peptide supplied as a lyophilised powder reconstituted with bacteriostatic water, and is supplied by RS Bio Labs as an in vitro research reagent only — not for human use. Research-grade Tirzepatide is available in ten strengths at ≥99% purity; see the buy Tirzepatide UK page.
Tirzepatide, known by its developer code LY3298176, is a synthetic 39-amino-acid peptide engineered by Eli Lilly to activate two distinct metabolic receptors simultaneously: the glucose-dependent insulinotropic polypeptide receptor (GIPR) and the glucagon-like peptide-1 receptor (GLP-1R). Because it engages both, it is described in the literature as a "dual agonist" or "twincretin", placing it one generation beyond the single GLP-1 agonist Semaglutide and one generation behind the triple GIP/GLP-1/glucagon agonist Retatrutide.
Tirzepatide is the compound that reset expectations for the incretin class. Where selective GLP-1 agonists had delivered meaningful but modest metabolic effects, the addition of a second incretin arm produced a step-change in magnitude of response in large randomised trials. The design idea is that GLP-1 and GIP act on overlapping but non-identical tissues — brain satiety circuits, pancreatic β-cells and adipose tissue — so co-activating both yields complementary effects on appetite, insulin secretion and lipid handling that a single receptor cannot match.
The molecule is marketed under the brand names Mounjaro (for type 2 diabetes) and Zepbound (for chronic weight management), and it is FDA-approved in those therapeutic settings. However, the material supplied by RS Bio Labs is strictly a research reagent for in vitro laboratory work and is not for human use. Researchers looking to buy Tirzepatide in the UK can obtain it in ten strengths, each third-party HPLC tested to ≥99% purity.
Tirzepatide is the product of a long incretin-engineering programme at Eli Lilly. The scientific lineage runs from native glucagon-like peptide-1 — a gut hormone with a half-life of only a couple of minutes — through long-acting GLP-1 analogues, to the deliberate fusion of GIP and GLP-1 activity into a single balanced molecule. Rather than combining two separate drugs, Lilly's chemists built one peptide backbone capable of engaging both receptors, then conjugated a fatty-acid tail to extend its duration of action.
The compound's preclinical characterisation was published by Coskun and colleagues in Molecular Metabolism in 2018, in a paper titled "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." That work described the molecule's receptor-binding profile — notably an imbalanced agonism that favours the GIP receptor — and demonstrated in animal models and early human studies that the dual mechanism produced greater improvements in glucose control and body weight than selective GLP-1 agonism alone.
First-in-human studies established the compound's tolerability and its approximately five-day half-life, confirming that a once-weekly schedule was feasible. These data set the stage for the sprawling SURPASS Phase 3 programme in type 2 diabetes and the SURMOUNT Phase 3 programme in obesity, which together enrolled many thousands of participants and led to regulatory approval as Mounjaro and Zepbound. The compound registration for the pivotal obesity trial is held on ClinicalTrials.gov under NCT04184622.
Tirzepatide is a single peptide molecule that binds and activates two structurally related class B G-protein-coupled receptors. Each sits at a different node of the energy-balance and glucose-handling network, and the combined agonism produces a metabolic phenotype more potent than that of any selective GLP-1 agonist studied before it. Receptor affinity has been tuned so that the molecule behaves as a balanced-to-GIP-biased agonist, preserving metabolic synergy across both targets.
The GIP arm is the crux of the design. For decades GIP was regarded as the "forgotten incretin," and its precise contribution to Tirzepatide's effect remains an area of active research — but the consistent observation is that adding GIP agonism to GLP-1 agonism raises the ceiling on both weight and glucose outcomes. The molecule itself is a fatty-acid-conjugated (C20) long-acting peptide; the fatty-acid tail promotes reversible binding to serum albumin, which is what gives Tirzepatide its extended, once-weekly duration of action. For a broader treatment of how these pathways differ, see our guide to GLP-1 vs GIP vs glucagon agonists.
Tirzepatide's clinical evidence base is among the largest for any modern metabolic compound, spanning type 2 diabetes (the SURPASS programme) and obesity (the SURMOUNT programme). The landmark readouts are summarised below, followed by the individual trial and discovery cards.
| Trial / population | Publication | n | Headline result |
|---|---|---|---|
| Phase 3 · Obesity (SURMOUNT-1) | NEJM, 2022 | 2539 | ~16.0% (5 mg) to ~22.5% (15 mg) weight reduction at 72 wk |
| Phase 3 · Type 2 diabetes (SURPASS-2) | NEJM, 2021 | 1879 | Superior HbA1c and weight reduction vs semaglutide 1 mg |
| Preclinical · Discovery | Molecular Metabolism, 2018 | — | Dual GIP/GLP-1 agonism; proof of concept in T2D |
Tirzepatide's defining pharmacokinetic feature is its terminal half-life of approximately five days. This is a direct consequence of the molecule's C20 fatty-acid conjugation, which drives reversible binding to serum albumin. Albumin binding acts as a circulating reservoir, slows renal clearance, and shields the peptide from rapid proteolytic degradation — the same design principle used across the modern long-acting incretin class.
A ~5-day half-life supports a once-weekly research schedule. As with any compound dosed at roughly one half-life intervals, plasma concentrations accumulate over successive administrations and approach steady state after about four to five half-lives — on the order of four to five weeks. This accumulation behaviour is the reason published protocols use gradual dose escalation: titrating upward over several weeks allows tolerance to the gastrointestinal effects to develop as concentrations rise.
| Parameter | Value (approx.) | Note |
|---|---|---|
| Terminal half-life | ~5 days | Fatty-acid/albumin driven |
| Research schedule | Once weekly | ~1 half-life dosing interval |
| Time to steady state | ~4–5 weeks | ~4–5 half-lives |
| Molecular weight | ~4,813 Da | 39-aa peptide + C20 tail |
| Elimination | Proteolysis + renal | Slowed by albumin binding |
As a lyophilised (freeze-dried) powder, Tirzepatide is highly stable. Removing water from the formulation dramatically slows the chemical degradation pathways — hydrolysis, deamidation, oxidation and aggregation — that shorten a peptide's shelf life in solution. Sealed, protected from light and kept cool, lyophilised Tirzepatide retains its integrity over long periods.
Stability falls once the powder is reconstituted. In solution the peptide becomes susceptible to gradual hydrolysis and to physical stresses such as agitation (which can cause aggregation and foaming) and repeated freeze–thaw cycles (which mechanically damage peptide structure). Heat and light accelerate degradation in both states. In practical terms this means the lyophilised vial is the storage-stable form, and the reconstituted solution should be treated as a shorter-lived working stock — see Storage and Reconstitution below.
Correct storage preserves both the mass and the biological integrity of the compound. The guidance below reflects standard best practice for lyophilised research peptides.
| State | Temperature | Approx. shelf life | Notes |
|---|---|---|---|
| Lyophilised | −20 °C (freezer) | Months to years | Best long-term option; protect from light |
| Lyophilised | 2–8 °C (fridge) | Weeks to months | Fine for medium-term storage |
| Lyophilised | Room temperature | Days (transit) | Tolerates brief shipping periods |
| Reconstituted | 2–8 °C (fridge) | ~4–6 weeks | Bacteriostatic water aids stability; keep dark |
| Reconstituted | Frozen | Avoid | Freeze–thaw degrades the peptide |
Label reconstituted vials with the date of preparation, minimise exposure to light and heat, and avoid repeatedly warming and cooling a working stock. Allow refrigerated vials to return toward room temperature before handling to reduce condensation.
The following describes standard laboratory technique for preparing a research stock solution from a lyophilised vial. It is not guidance for human use of any kind. For a fully worked walkthrough with more dilution examples, see our reconstitution calculator.
Reconstitution simply means dissolving the freeze-dried powder into solution. The standard diluent for a multi-use research vial is bacteriostatic water (water with 0.9% benzyl alcohol, which suppresses microbial growth). You will also need a sterile syringe and alcohol wipes. Technique matters: wipe the vial stopper, draw the chosen volume of bacteriostatic water, and add it slowly down the inner glass wall rather than squirting it directly onto the powder. Let the peptide dissolve, swirl gently, and never shake — agitation causes foaming and can damage the peptide.
Concentration is simply the mass of peptide divided by the volume of water added. Adding more water gives a lower concentration:
| Vial | Bacteriostatic water added | Resulting concentration |
|---|---|---|
| 10 mg | 1 ml | 10 mg/ml |
| 10 mg | 2 ml | 5 mg/ml |
| 30 mg | 3 ml | 10 mg/ml |
| 30 mg | 2 ml | 15 mg/ml |
| 60 mg | 3 ml | 20 mg/ml |
Once reconstituted, store the vial refrigerated at 2–8 °C and use it within a few weeks (see Storage). Maintain sterility throughout and label the vial with the concentration and preparation date.
Tirzepatide sits on the middle rung of the incretin "agonism ladder" — above the selective GLP-1 agonists and below the newer triple agonists. The table below places it against the other most-studied metabolic research peptides by receptor targets and headline trial effect. For the mechanistic detail behind these classes, see GLP-1 vs GIP vs glucagon; for a direct head-to-head, see Retatrutide vs Tirzepatide.
| Compound | Receptor targets | Class | Peak trial weight change | Half-life |
|---|---|---|---|---|
| Tirzepatide | GIP + GLP-1 | Dual | ~22.5% (Ph3, 72 wk) | ~5 days |
| Retatrutide | GIP + GLP-1 + Glucagon | Triple | ~24.2% (Ph2, 48 wk) | ~6 days |
| Semaglutide | GLP-1 | Mono | ~15% (Ph3, 68 wk) | ~7 days |
| Mazdutide | GLP-1 + Glucagon | Dual | ~14% (Ph3, 48 wk) | Weekly |
| Survodutide | GLP-1 + Glucagon | Dual | MASH-focused Ph2 | ~6 days |
The pattern is consistent: engaging more complementary receptor systems has raised the ceiling on effect size at each step. Tirzepatide's addition of the GIP "second incretin" arm placed it well ahead of the selective GLP-1 agonists, and it remains the highest-efficacy compound with full regulatory approval — while the triple agonists that add a glucagon "energy-out" arm edge ahead of it in cross-trial comparisons. To compare live pricing and strengths, see the buy Tirzepatide UK and buy Retatrutide UK pages.
The findings above are drawn from the following peer-reviewed publications and trial registrations. Links open on the publisher or registry site.