Tirzepatide – Research Peptide

What tirzepatide is

Tirzepatide is a synthetic 39-residue peptide that acts as an agonist at two incretin receptors at once — the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor^[1]. It was developed by Eli Lilly and Company, which funded essentially the entire clinical programme cited on this page^[1][5].

Unlike most compounds in this catalogue, tirzepatide is not an obscure preclinical molecule. It went through a large, well-powered, registrational phase 3 programme, and it is an approved drug substance. That changes what this page has to do. The problem here is not a thin evidence base — it is that the evidence base belongs to a regulated medicine, and none of it transfers to material bought as a research chemical.

Structure and identity

Tirzepatide · C225H348N48O68 · 4813 g/mol · CAS 2023788-19-2 · Source: PubChem CID 166567236

Molecular formula, molecular weight, CAS registry number and the structure above were retrieved directly from the PubChem PUG-REST API, not transcribed from a secondary source^[9]. The Aib substitutions confer resistance to dipeptidyl peptidase-4 cleavage; the fatty diacid chain drives albumin binding and produces the once-weekly pharmacokinetic profile used throughout the clinical programme.

Every batch we supply is assayed by an independent laboratory using HPLC-UV-MS. The mass spectrum is compared against an authentic reference standard to confirm molecular identity; the peptide’s peak area is measured against the total chromatogram area to establish chromatographic purity; and total peptide mass in the vial is measured against the stated label claim.

Measured values for the current lot are pending. We do not print numbers we do not have. When the certificate is released it will appear on this page and be independently verifiable with the issuing laboratory.

An approved drug substance, sold for research use

Where the evidence stands

This is the section most vendors skip. It is the most important one on the page.

This is an unusual entry in a research-peptide catalogue: the human tier is the strongest tier, not the weakest. Almost everything below is human phase 3 data, and we are going to report the unflattering parts of it as well as the headline numbers.

The SURPASS programme human

SURPASS-1 was a 40-week, double-blind, randomised, placebo-controlled phase 3 trial across 52 centres in India, Japan, Mexico and the USA. 478 adults with type 2 diabetes, naive to injectable therapy, were randomised 1:1:1:1 to tirzepatide 5, 10 or 15 mg once weekly, or placebo. Mean HbA_1c change from baseline at 40 weeks was −1.87% (5 mg), −1.89% (10 mg) and −2.07% (15 mg) versus +0.04% with placebo. Mean bodyweight change across the tirzepatide arms ranged from −7.0 to −9.5 kg. No severe hypoglycaemia was reported in any tirzepatide arm. One death occurred, in the placebo group. Funded by Eli Lilly and Company^[1].

SURPASS-2 was an open-label 40-week phase 3 trial randomising 1879 participants to tirzepatide 5, 10 or 15 mg or to an active GLP-1 receptor agonist comparator. Mean HbA_1c change was −2.01% to −2.30% across the tirzepatide arms versus −1.86% with the comparator; estimated treatment differences ranged from −0.15 to −0.45 percentage points^[2]. Participants and investigators knew which drug they were on. That is a real methodological limitation, not a footnote.

SURPASS-4 randomised 2002 participants with type 2 diabetes and elevated cardiovascular risk against insulin glargine, with adjudicated major adverse cardiovascular events collected over up to 104 weeks. Mean HbA_1c change at 52 weeks was −2.43% (10 mg) and −2.58% (15 mg) versus −1.44% with glargine. Adjudicated MACE-4 events occurred in 109 participants; hazard ratio 0.74 (95% CI 0.51–1.08) versus glargine. Sixty deaths occurred during the study (25 tirzepatide, 35 glargine)^[3].

SURPASS-5 added tirzepatide to titrated insulin glargine in 475 participants over 40 weeks; mean HbA_1c change was −2.11% to −2.40% versus −0.86% with placebo, and mean bodyweight change was −5.4 to −8.8 kg versus +1.6 kg^[4].

SURMOUNT-1 human

SURMOUNT-1 was a 72-week, double-blind, randomised phase 3 trial in 2539 adults with obesity and without diabetes, including a 20-week supervised dose-escalation period. Mean percentage change in weight at week 72 was −15.0% (5 mg), −19.5% (10 mg) and −20.9% (15 mg) versus −3.1% with placebo. In the 15 mg arm, 57% of participants had a weight reduction of 20% or more, versus 3% on placebo^[5].

These are among the largest weight changes recorded in a pharmacological obesity trial. They were also obtained with a slow supervised escalation, trial-grade drug product, and clinical monitoring — none of which describes anyone handling a research vial.

Mechanism at the receptor in vitro

Tirzepatide’s defining pharmacology is co-agonism: a single molecule engaging both the GIP receptor and the GLP-1 receptor^[1]. The clinical programme was built around the hypothesis that dual incretin engagement produces larger glycaemic and weight effects than GLP-1 receptor agonism alone, and SURPASS-2 was the head-to-head test of that hypothesis^[2]. That is a statement about receptor pharmacology established in binding and signalling assays. On its own it says nothing about any outcome in a person.

Adverse events and safety signals

This section is not an afterthought. It is the reason to read the page.

Gastrointestinal events human

Across the entire programme, the dominant adverse events are gastrointestinal and dose-related. SURPASS-1: nausea 12–18% (placebo 6%), diarrhoea 12–14% (placebo 8%), vomiting 2–6% (placebo 2%)^[1]. SURPASS-4: nausea 12–23%, diarrhoea 13–22%, decreased appetite 9–11%, vomiting 5–9%, versus 2%, 4%, <1% and 2% on glargine^[3]. A 2025 systematic review and meta-analysis in Annals of Saudi Medicine pooled gastrointestinal safety data for tirzepatide and semaglutide against placebo in participants with obesity and without diabetes, and found a materially elevated rate of gastrointestinal adverse events on active drug^[6].

Discontinuation human

In SURMOUNT-1, adverse events caused treatment discontinuation in 4.3%, 7.1% and 6.2% of the 5, 10 and 15 mg arms respectively, versus 2.6% on placebo^[5]. In SURPASS-5, treatment was prematurely discontinued by 18% of the 15 mg arm versus 3% of placebo^[4]. People leave these trials because of how the drug makes them feel, and the rate rises with dose.

Serious adverse events and hypoglycaemia human

In SURPASS-2, serious adverse events were reported in 5–7% of tirzepatide participants versus 3% of the comparator arm — tirzepatide had the higher serious-event rate in that trial. Hypoglycaemia below 54 mg/dL was reported in 0.6%, 0.2% and 1.7% of the 5, 10 and 15 mg arms^[2].

Rodent thyroid C-cell tumours rodent

Cardiovascular tolerability human

A 2025 systematic review and meta-analysis in the Journal of the American College of Cardiology pooled cardiovascular effects and tolerability data across GLP-1 receptor agonists in 99,599 patients^[7]. SURPASS-4 specifically found no excess of adjudicated cardiovascular events on tirzepatide versus insulin glargine over up to 104 weeks^[3].

What did not go the drug’s way

• SURPASS-4’s MACE hazard ratio was 0.74, 95% CI 0.51–1.08. That interval includes 1.0. The trial demonstrated the absence of excess cardiovascular risk, not cardiovascular benefit, and it was not powered to show benefit^[3].
• SURPASS-2 was open-label. An unmasked head-to-head efficacy comparison is a weaker design than the same trial with masking, and the direction of that weakness is not neutral^[2].
• Serious adverse events were numerically higher on tirzepatide than on the active comparator in SURPASS-2 (5–7% vs 3%)^[2].
• Nearly one in five participants left the 15 mg arm of SURPASS-5 early^[4].
• The rat thyroid C-cell signal has never been resolved. “Human relevance unknown” is not “human relevance excluded”^[8].

Limitations of the literature

The evidence base has one owner. SURPASS-1, SURPASS-2, SURPASS-4, SURPASS-5 and SURMOUNT-1 were all funded by Eli Lilly and Company, and Lilly employees are co-authors on all of them^{[1][2][3][4][5]}. This is normal for a registrational programme and does not make the results wrong. It does mean fully independent replication of the headline effect sizes is thinner than the volume of literature suggests.

Trial conditions are not field conditions. Every number on this page was generated under a supervised dose-escalation protocol with pharmaceutical-grade drug product and clinical monitoring. The escalation schedule is not a detail — it is the principal method by which the gastrointestinal burden was kept tolerable, and the discontinuation rates show it only partly worked.

Regulatory and anti-doping status

Tirzepatide is an FDA-approved drug substance. The material sold on this page is supplied as a research chemical and is not an approved drug product; it has not been reviewed, released, or labelled as a medicine, and no part of the branded product’s approval extends to it^[8]. An approved drug sold research-use-only is a different animal from an unapproved one, and it is worth being precise about which animal you are looking at: the molecule has a regulatory dossier; the vial does not.

WADA status appears as a neutral data line in the specification block above — Not listed — in the same register as the CAS number. Anti-doping lists change annually and by governing body. If you compete under any tested organisation, the only reliable source is that organisation’s current prohibited list — not this page, and not any vendor’s.

What we don’t know

• Whether the rat thyroid C-cell tumour finding has any human relevance. It has not been determined^[8].
• Outcomes beyond the trial windows above — SURMOUNT-1 ran 72 weeks, SURPASS-4 up to 104 weeks. Nothing here speaks to year five.
• Whether the cardiovascular hazard ratio in SURPASS-4 would separate from 1.0 in a trial powered to test it.
• Anything at all about the stability, content, or behaviour of research-grade material outside a validated pharmaceutical supply chain. Per-kilogram dosing in animal models does not scale to humans, and nothing on this page should be read as implying that it does.

We supply this compound for laboratory research. The clinical dataset behind tirzepatide is genuinely large and genuinely good. It is also not a dataset about the vial we are selling you.