Retatrutide in Type 2 Diabetes: TRANSCEND-T2D-1 Phase 3 Data

What is the TRANSCEND-T2D-1 trial?

TRANSCEND-T2D-1 is a Phase 3 randomised, double-blind, placebo-controlled trial evaluating retatrutide (LY3437943) in adults with recent-onset type 2 diabetes (T2D). Results were simultaneously published in The Lancet and presented at the 86th American Diabetes Association (ADA) Scientific Sessions in New Orleans on 6 June 2026 — making this the freshest Phase 3 dataset available on retatrutide.[1]

The trial is distinct from TRIUMPH-1, Eli Lilly’s earlier Phase 3 readout (announced 21 May 2026), which studied retatrutide in adults with obesity or overweight without diabetes. TRANSCEND-T2D-1 specifically investigated retatrutide in an insulin-resistant, hyperglycaemic model — a metabolic phenotype of particular interest to researchers studying multi-receptor incretin pharmacology, because T2D involves impaired insulin secretion, hepatic glucose overproduction, and adipose dysfunction that differ from non-diabetic obesity.

Retatrutide (CAS 2381089-83-2) is a synthetic peptide developed by Eli Lilly that activates three receptor types simultaneously: the GLP-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor. For a full overview of receptor pharmacology, preclinical data, and TRIUMPH-1 results, see the Retatrutide Research Overview. For head-to-head comparisons with tirzepatide and semaglutide, see the retatrutide vs tirzepatide vs semaglutide guide.

Velox Peptides supplies retatrutide as an HPLC-verified (≥99% purity) lyophilised reagent for in vitro research use only. View the Retatrutide product page →

How was TRANSCEND-T2D-1 designed?

TRANSCEND-T2D-1 enrolled 537 adults with recent-onset type 2 diabetes. The trial’s population selection was deliberate: participants had a mean disease duration of approximately 2.5 years, and glycaemic control was inadequate on diet and exercise alone — meaning no background glucose-lowering medication was permitted at baseline. This clean-background design allows direct assessment of retatrutide’s glycaemic activity without confounding from concomitant antidiabetic therapy, making the dataset particularly informative for receptor-level pharmacology research.[2]

Participants were randomised 1:1:1:1 to four arms:

• Retatrutide 4 mg once weekly (subcutaneous injection)
• Retatrutide 9 mg once weekly
• Retatrutide 12 mg once weekly
• Placebo

The primary endpoint was change in glycated haemoglobin (HbA1c, referred to below as A1C) from baseline to week 40. Pre-specified secondary endpoints included the proportion of participants achieving A1C targets (<7.0% and ≤6.5%), body weight change, and a panel of cardiometabolic markers: fasting triglycerides, non-HDL cholesterol, systolic blood pressure, and waist circumference.

What did the A1C and glycaemic control data show?

From a mean baseline A1C of approximately 7.9%, retatrutide produced dose-dependent A1C reductions across all three active arms at week 40. The placebo arm reduced A1C by −0.81% over the same period, reflecting a modest improvement attributable to trial participation and lifestyle support.[2]

Beyond mean A1C, the study reported that approximately 90% of participants on the 12 mg dose achieved A1C < 7.0% at week 40 — the ADA’s general glycaemic target for T2D management. Approximately 85% achieved A1C ≤ 6.5% at the same timepoint, a stricter target often used in early or uncomplicated T2D research models.[2]

The placebo-adjusted A1C reduction with the 12 mg dose is approximately 1.1 percentage points, which the published report characterises as a clinically meaningful difference in this population of drug-naïve early T2D. The dose–response relationship across the three active cohorts (4→9→12 mg: −1.69%→−1.86%→−1.94%) is consistent with the pharmacodynamic properties described in the preclinical characterisation by Coskun et al. (2022).[5]

What weight and cardiometabolic outcomes were reported?

Weight reduction was a pre-specified secondary endpoint. At week 40, the 12 mg dose reported a mean body-weight reduction of 16.8%. This figure is lower than the 28.3% reported in TRIUMPH-1 at week 80, but the comparison should be made carefully: TRANSCEND-T2D-1 had a shorter observation period (40 vs 80 weeks), and it is well established across GLP-1-class research literature that weight response is typically attenuated in T2D populations compared to non-diabetic obesity models — a pattern observed with semaglutide and tirzepatide as well.[3]

Beyond body weight, the 12 mg dose at 40 weeks was also associated with the following cardiometabolic changes in the published report:[1][2]

Waist circumference was also reduced by a mean of 12.4 cm (4.9 inches) at the 12 mg dose. This broad cardiometabolic signal across lipid fractions, blood pressure, and adiposity markers is consistent with the triple-receptor mechanism described in preclinical models: the GLP-1 pathway contributes to insulin sensitisation and appetite modulation, GIP to fat-tissue signalling, and the glucagon pathway to hepatic lipid handling and energy expenditure.[5][6]

Safety profile in TRANSCEND-T2D-1

The safety profile reported in TRANSCEND-T2D-1 was broadly consistent with GLP-1-class compounds. Gastrointestinal adverse events — primarily nausea, diarrhoea, and vomiting — were the most frequently reported events and were described as predominantly mild-to-moderate in severity. Treatment-related discontinuations ranged from 2.2% (4 mg) to 5.1% (12 mg) across the active arms, compared with 0% in the placebo group. No unexpected safety signals were described in the published report.[2]

How do TRANSCEND-T2D-1 and TRIUMPH-1 compare?

TRANSCEND-T2D-1 and TRIUMPH-1 are two separate Phase 3 trials of retatrutide, each studying the compound in a distinct metabolic phenotype. The table below summarises key design and outcome differences. Neither trial’s results should be read as claims about Velox Peptides products.

The lower weight reduction in TRANSCEND-T2D-1 (16.8% at 40 weeks) compared with TRIUMPH-1 (28.3% at 80 weeks) reflects both the shorter observation period and the known pharmacodynamic pattern across the GLP-1 class: weight responses in T2D are typically smaller than in non-diabetic obesity populations, a finding attributed in part to differences in baseline insulin resistance, gut hormone signalling, and compensatory mechanisms. The TRANSCEND-T2D-1 dataset offers a complementary perspective for researchers interested in how retatrutide’s glucagon receptor arm contributes to hepatic and lipid outcomes specifically in an insulin-resistant context.

Where does TRANSCEND-T2D-1 fit in the broader TRIUMPH programme?

TRANSCEND-T2D-1 is part of Eli Lilly’s extensive Phase 3 programme for retatrutide, which runs under the TRIUMPH (TRIple-hormone-receptor aGonist for ObesIty Management Pivotal) umbrella. The full programme comprises eight pivotal trials enrolling more than 5,800 participants in total across weight-management and diabetes indications, plus a separate cardiovascular outcomes trial enrolling approximately 10,000 patients.[4]

For researchers studying GLP-1/GIP/glucagon receptor pharmacology, the TRIUMPH programme represents the largest clinical dataset on triple-receptor agonism to date. The separation of non-diabetic obesity (TRIUMPH-1) and early T2D (TRANSCEND-T2D-1) into distinct trials provides a controlled way to examine how baseline metabolic state modifies the observed response profile — an area of active interest in the preclinical literature on incretin biology.[5]

Velox Peptides Supply Information

Retatrutide is supplied as a research reagent only. It is not a medicine and has not been evaluated by the MHRA or FDA. Not for human or veterinary use. See our Research Use Policy and MHRA Statement.

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