Introduction
Eli Lilly has announced positive topline results from two additional Phase 3 clinical trials of research grade retatrutide. It is an experimental triple hormone receptor agonist that has now become a potential candidate for submission for regulatory approval as early as 2027. The results of the TRIUMPH-2 and TRIUMPH-3 studies have successfully achieved their primary endpoints by showing significant weight reduction along with improved glycemic control and metabolic parameters among adults suffering from obesity and comorbid conditions.
Phase 3 Clinical Results
TRIUMPH-2: Weight Loss Outcomes in Type 2 Diabetes
The TRIUMPH-2 study included 1,152 adults with either overweight or obesity in combination with type 2 diabetes, which is an area known to face substantial metabolic resistance to weight loss. Patients were randomized to receive weekly retatrutide in doses of 4 mg, 9 mg, or 12 mg or placebo.
Key Findings:
| Dose | Mean Weight Loss | A1C Reduction |
| 4 mg | 12.7% | 1.4 percentage points |
| 9 mg | 19.1% | 1.6 perecentge points |
| 12 mg | 20.8% (49.6 lbs) | 1.5 percentage points |
| Placebo | 4.0% | 0.5 percentage points |
Based on the information shared by Eli Lilly, and along with the American Diabetes Association disclosure, those patients who were under the dosage of 12 mg managed to lose close to 50 pounds after 80 weeks. As well, the improvement in terms of glycemia was also seen to be very good, since those patients managed to see a reduction in their A1C level by 1.6 percentage points.
TRIUMPH-3: Targeting Severe Obesity and Cardiovascular Comorbidities
TRIUMPH-3 included 1,949 adults who were severely obese (BMI ≥ 35 kg/m²) and had cardiovascular diseases. The patients were provided with retatrutide at 9 mg, 12 mg, or placebo.
Findings: With respect to different doses:
- 12 mg: 22.6% weight loss on average (55.8 lbs)
- 9 mg: 21.6% weight loss on average
- Placebo: 3.2% weight loss
The safety results matched those seen previously in trials studying incretin peptides. The side effects observed were mainly moderate.
Cardiometabolic and Biomarker Observations
Beyond weight reduction, researchers also observed meaningful secondary improvements in several major cardiometabolic biomarkers within the clinical trial setting:
| Cardiovascular Marker | Reduction (12 mg dose) |
| Triglycerides | 37.0% |
| Cholesterol (Non-HDL) | 16.5% |
| Blood Pressure ( Systolic) | 9.3 mmHg |
| hsCRP (Inflammation Marker) | 51.2% |
Cardiovascular Event Analysis
In TRIUMPH-3, cardiovascular outcomes were followed as prespecified exploratory analyses. In the composite MACE-5 analysis (all-cause mortality, myocardial infarction, stroke, heart failure events, or coronary revascularization), there were 44 events in the pooled retatrutide groups compared to 52 in the placebo group (Hazard Ratio 0.82; 95% CI: 0.55–1.22). 27 events in the retatrutide group and 23 events in the placebo group (Hazard Ratio 1.12; 95% CI, 0.64 to 1.96).
Because the confidence intervals crossed 1.0, researchers emphasize that these exploratory trial endpoints were underpowered and leave definitive cardiovascular outcomes unresolved pending dedicated long-term cardiovascular outcome studies (such as the ongoing TRIUMPH-Outcomes trial).
The Concept of Tri-agonism
Retatrutide (LY3437943) is an experimental multifunctional peptide designed to bind and activate all three metabolic hormones’ receptors, namely GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon.
As described in the “Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide” article published in Cell Discovery (2024), this tri-agonism occurs due to selected changes in amino acids that enable fitting into specific receptor binding sites.
The other article titled “The power of three: Retatrutide’s role in modern obesity and diabetes therapy,” published in the European Journal of Pharmacology (2024), explains the following tri-functional mechanism of retatrutide:
- Activation of GLP-1 and GIP Receptors: Causes glucose-dependent insulin release and central appetite suppression.
- Activation of Glucagon Receptor: Promotes liver fatty acid oxidation and increases resting energy expenditure.
Inclusion of glucagon receptor signal makes it possible for retatrutide to maintain burning calories and fat oxidation even in animal models that normally reach a metabolic plateau with single or dual agonists.
Building on TRIUMPH-1 and Prior Studies
The new release of the data is based on the groundbreaking findings obtained during TRIUMPH-1. In this study, the 12 mg dose was found to provide an average 28.3% (70.3 lbs) weight loss at 80 weeks in adults who have obesity or are overweight but do not have diabetes. As part of a prespecified extended cohort of patients with a baseline BMI ≥ 35 who have remained on therapy up to 104 weeks, an average weight loss has reached 30.3% (85 lbs).
The level of weight loss comes close to that observed after certain surgeries aimed at bariatric weight loss; however, care should be exercised when comparing clinical trial and surgical data.
Pathway to Regulatory Submission
It has been formally declared by Eli Lilly that the company intends to submit a BLA application to the U.S. FDA in Q1 2027. Although artificial peptides usually go through the NDA submission process, Lilly is seeking a BLA to set up strict manufacturing, characterization, and quality control criteria for the molecule.
The intended submission will cover several conditions, including chronic weight management, obstructive sleep apnea, and knee osteoarthritis pain.
Safety and Adverse Events Profile
In both TRIUMPH-2 and TRIUMPH-3, there was no difference in the adverse events profile compared to other GLP-1 and multi-agonist peptides. The most common adverse events were gastrointestinal issues that, as a rule, were classified as mild or moderate and resolved while the dose was being titrated.
Adverse events-related discontinuation rates:
- TRIUMPH-2: 3.8% (4 mg), 11.6% (9 mg), and 7.7% (12 mg) versus 4.9% in the placebo group.
- TRIUMPH-3: 9.8% (9 mg) and 13.5% (12 mg) versus 4.8% in the placebo group.
The most commonly reported side effects were diarrhea, nausea, constipation, vomiting, and dysesthesia (altered skin sensation).
Applications for Scientific Research
In terms of laboratory and biochemical studies, retatrutide is a good research model for receptor cross-talk, tissue-specific metabolism signaling, and mitochondrial bioenergetics. Studying triple receptor agonists helps to understand the effect of combined activation of certain pathways on cellular energy expenditure, lipid transport, and hepatic steatosis.
FAQs
1. What is Retatrutide in scientific research?
Retatrutide (LY3437943) is an experimental triple hormone receptor agonist that targets GLP-1, GIP, and glucagon receptors simultaneously. It is used for scientific research to investigate the effect of multi-target metabolism regulation.
2. What were the main results in TRIUMPH-2 and TRIUMPH-3 trials?
Subjects in the TRIUMPH-2 trial (patients with obesity and type 2 diabetes) lost weight by 20.8% (49.6 lbs) on average and lowered their HbA1c levels by up to 1.6% in 80 weeks. Subjects in the TRIUMPH-3 trial (patients with severe obesity and cardiovascular diseases) lost weight by 22.6% (55.8 lbs) on average in 80 weeks.
3. What is the date of planned FDA application of retatrutide?
According to Eli Lilly, they will file a BLA (Biologics License Application) with the FDA in the first quarter of 2027.
4. What distinguishes the mechanism of action of retatrutide from that of dual agonists such as tirzepatide?
Unlike single agonists, which act through GLP-1 receptor activation and dual agonists, which activate GLP-1 and GIP receptors, retatrutide activates another receptor called the glucagon receptor. Activation of the glucagon pathway results in an increase in energy expenditure and liver fat breakdown, forming a third way to investigate metabolism. Retatrutide is still under investigation and has not been approved by the FDA yet and is not available for sale for human consumption.
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References
- Eli Lilly and Company. (2026). Lilly’s triple agonist, retatrutide, successful in two additional Phase 3 obesity trials, delivering significant improvements in weight and A1C. PR Newswire.
- ClinicalTrials.gov. (2026). A Study of Retatrutide (LY3437943) in Participants With Overweight or Obesity (TRIUMPH Program). U.S. National Library of Medicine.
- Jastreboff, A. M., et al. (2023). “Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial.” New England Journal of Medicine, 389(6), 514–526.
- Zhao, L., et al. (2024). “Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide.” Cell Discovery, 10, 144.
- HCPLive / Custer, K. (2026). Retatrutide Meets Phase 3 Weight-Loss Endpoints in 2 Obesity Trials.
