A synthetic 39-amino-acid peptide that activates both the GIP and the GLP-1 receptor, the first dual agonist of its kind. It is the active ingredient of medicines authorised in the EU; material supplied here is laboratory reagent and not that product.

Is tirzepatide more effective than semaglutide?

In a direct head-to-head trial in patients with type 2 diabetes, tirzepatide produced greater reductions in glycated haemoglobin and in body weight across its treatment groups over 40 weeks. That is a published result in that population; extending it to other populations is an inference rather than a finding.

What happens when tirzepatide is stopped?

SURMOUNT-4 tested exactly that. After a 36-week lead-in reaching a mean 20.9% weight reduction, participants who continued changed by a further −5.5% while those switched to placebo gained 14.0% — a 19.4 percentage point divergence over 52 weeks.

What adverse findings have been reported?

The most consequential published finding is the withdrawal result above: the effect is contingent on continued treatment. Gastrointestinal events are the commonly reported tolerability issue across the trial programme, and rodent carcinogenicity findings underlie warnings in the approved product information in several jurisdictions.

Is research-grade tirzepatide the same as the prescription medicine?

No. The authorised product is manufactured, tested, labelled and released under a marketing authorisation. A research vial carries a certificate of analysis and nothing more, and no published trial has studied material of that kind.

Research guides

Tirzepatide: what the research says

A dual GIP and GLP-1 receptor agonist, and the active ingredient of EU-authorised medicines. What the trials reported, and what no trial has studied.

Available in the catalogue

Supplied as research material. Sizes and pricing are on the product page. Availability is not a statement about what a compound does.

TIRZEPATIDE
Metabolic & GLP-1

Tirzepatide is the compound that made the dual-agonist approach credible, and the trial programme behind it is unusually complete: a placebo-controlled obesity trial, a head-to-head against semaglutide in type 2 diabetes, and a randomised withdrawal trial. Between them they answer three different questions, and the third is the one most often skipped.

The authorisation distinction, first

As with semaglutide, tirzepatide is the active ingredient of medicines authorised in the EU and elsewhere, and every trial below studied the authorised pharmaceutical product. Material supplied here has not been manufactured, tested, labelled or released under a marketing authorisation. It is laboratory reagent with a certificate of analysis, supplied for in-vitro research, and no published trial has studied material of that kind.

What the molecule is

A synthetic 39-amino-acid peptide that acts at both the GIP and the GLP-1 receptor — the first dual agonist of its kind, also designated LY3298176. Combining the two incretin pathways in one molecule is the whole design idea, and the head-to-head trial below is what tested whether it made a measurable difference.

The head-to-head, and why it is the interesting one

Placebo-controlled trials tell you that something works. A head-to-head against the established comparator tells you whether the new mechanism was worth adding. Frías and colleagues ran tirzepatide against semaglutide in patients with type 2 diabetes and reported greater reductions in glycated haemoglobin and in body weight across the tirzepatide groups.

That is a stronger form of evidence than a placebo comparison, and it is why the dual-agonist result registered as a significant finding in metabolic research rather than as one more incretin trial.

What stopping did

SURMOUNT-4 was built to answer the withdrawal question directly. Participants took tirzepatide for a 36-week lead-in, reaching a mean weight reduction of 20.9%, and were then randomised either to continue or to switch to placebo. Over the following 52 weeks the continued group changed by a further −5.5%; the withdrawn group gained 14.0%.

A nineteen-point divergence between continuing and stopping is the clearest statement in this literature about what the effect is contingent on. It belongs beside the headline figure and not below it.

What studies reported

Each entry states what a study examined and the model it used. Nothing below describes an outcome for a person.

Everything below is drawn from published research, and each entry names the model the study used. Approval status varies by compound and by country, and nothing described here is supplied as a medicine or for use in a person.

Jastreboff et al. (2022)New England Journal of Medicine · 387(3):205–16
Reported mean body weight reduction of 16.0–22.5% over 72 weeks across treatment groups, versus 2.4% on placebo, in adults with obesity or overweight and without diabetes.
human, randomised double-blind placebo-controlled (SURMOUNT-1) Source
Frías et al. (2021)New England Journal of Medicine · 385(6):503–15
Compared tirzepatide directly against semaglutide in patients with type 2 diabetes, reporting greater reductions in glycated haemoglobin and in body weight across the tirzepatide groups over 40 weeks.
human, randomised open-label active-comparator against semaglutide (SURPASS-2) Source

Adverse and null findings reported

Harms, tolerability observations, and trials that did not meet their endpoint. A negative result is a finding and is listed here rather than omitted.

Aronne et al. (2024)JAMA · 331(1):38–48
After a 36-week lead-in reaching a mean weight reduction of 20.9%, participants were randomised to continue or to withdraw. From week 36 to week 88 the continued group changed by −5.5% and the withdrawn group by +14.0%, a difference of 19.4 percentage points.
human, randomised withdrawal trial, 670 participants (SURMOUNT-4) Source

What the research does not establish

An absence cannot be cited, so these are stated plainly. They are the part of the picture that silence would otherwise hide.

No published trial has studied research-grade or compounded tirzepatide. Every result above was obtained with the authorised pharmaceutical product.
SURMOUNT-4 establishes that withdrawal reverses the effect substantially within a year. Nothing published establishes what happens over the timescales the compound would have to be used across for that to matter.
The head-to-head against semaglutide was run in type 2 diabetes, not in obesity without diabetes. Reading it across to the obesity population is an inference and not a published result.
Body composition over long periods is not characterised, including what proportion of the loss is lean mass and whether that proportion changes with duration.
Rodent carcinogenicity findings underlie warnings in the approved product information in several jurisdictions, and whether they translate to humans is not established.

Common questions

What is tirzepatide?: A synthetic 39-amino-acid peptide that activates both the GIP and the GLP-1 receptor, the first dual agonist of its kind. It is the active ingredient of medicines authorised in the EU; material supplied here is laboratory reagent and not that product.
Is tirzepatide more effective than semaglutide?: In a direct head-to-head trial in patients with type 2 diabetes, tirzepatide produced greater reductions in glycated haemoglobin and in body weight across its treatment groups over 40 weeks. That is a published result in that population; extending it to other populations is an inference rather than a finding.
What happens when tirzepatide is stopped?: SURMOUNT-4 tested exactly that. After a 36-week lead-in reaching a mean 20.9% weight reduction, participants who continued changed by a further −5.5% while those switched to placebo gained 14.0% — a 19.4 percentage point divergence over 52 weeks.
What adverse findings have been reported?: The most consequential published finding is the withdrawal result above: the effect is contingent on continued treatment. Gastrointestinal events are the commonly reported tolerability issue across the trial programme, and rodent carcinogenicity findings underlie warnings in the approved product information in several jurisdictions.
Is research-grade tirzepatide the same as the prescription medicine?: No. The authorised product is manufactured, tested, labelled and released under a marketing authorisation. A research vial carries a certificate of analysis and nothing more, and no published trial has studied material of that kind.

Compounds covered

The reference page for each compound this article discusses.

Tirzepatide

Semaglutide: what the research says
A GLP-1 receptor agonist and the active ingredient of EU-authorised medicines. What the trials reported, the discontinuation rates, and the open questions.
Retatrutide (LY3437943): what the research says
A triple hormone receptor agonist still in development, with no marketing authorisation anywhere. What the published phase 2 work reported, and what it did not.
How to store research peptides
Lyophilised peptides at -20°C, reconstituted at 2–8°C, ambient in transit. Why the dry cake tolerates shipping, and what actually degrades a vial.

About this article

Everything reported here comes from published research, and each finding names the model the study used — cell culture, rat, or human. Findings in one model do not transfer to another, most of the work described is preclinical, and none of it is a claim that a compound is safe or effective for any purpose. Nothing on this page describes doses, routes of administration, or use in a person.

Approval status varies by compound and by country. A few of the substances described are the active ingredient of medicines authorised in the EU; most have no marketing authorisation anywhere and have never been assessed by a regulator. Neither is supplied as a medicine here. All material supplied by ASSAY is sold for in-vitro laboratory research only, and is not a drug, food, cosmetic or medical device, and not for human or veterinary use.

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