Updated 7 October 2026. Retatrutide is an investigational, once-weekly medicine being developed by Eli Lilly. It is designed as a single molecule that activates three hormone receptors: GIP, GLP-1 and glucagon. The newest Phase 3 results are notable, but retatrutide remains under clinical investigation and has not been approved by the FDA, EMA or any other regulatory authority.
What is retatrutide?
Retatrutide is often described as a “triple agonist” because it targets the glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and glucagon receptors. The informal label “GLP-3” is scientifically inaccurate: there is no GLP-3 receptor involved.
The combination is being studied for its effects on appetite, glucose regulation and energy metabolism. These mechanisms are still being evaluated across Lilly’s TRIUMPH and TRANSCEND Phase 3 programmes.
Latest Phase 3 results in obesity: TRIUMPH-1
TRIUMPH-1 was a randomized, double-blind, placebo-controlled Phase 3 trial in 2,339 adults with obesity or overweight and at least one weight-related condition, without diabetes. At 80 weeks, the efficacy estimand showed average weight changes of 19.0% with 4 mg, 25.9% with 9 mg and 28.3% with 12 mg, compared with 2.2% with placebo.
Among a pre-specified extension group with a baseline BMI of at least 35, participants assigned to 12 mg reached an average 30.3% weight reduction at 104 weeks. This extension involved a selected subgroup that had completed the main study and tolerated treatment, so it should not be interpreted as the expected result for every patient.
Full TRIUMPH-1 results were published in The New England Journal of Medicine on 29 September 2026. The reported figures describe group averages under defined trial conditions; they do not predict an individual outcome.
Type 2 diabetes and obesity: TRIUMPH-2
Detailed TRIUMPH-2 results were announced on 29 September 2026 and presented at the 2026 EASD meeting. In adults with type 2 diabetes and obesity or overweight, average weight change at 80 weeks was 12.7% with 4 mg, 19.1% with 9 mg and 20.8% with 12 mg, compared with 4.0% with placebo. Average A1C reductions reached up to 1.6 percentage points in the retatrutide groups.
These results apply to the population and protocol studied. Comparisons with another medicine cannot be made reliably without an appropriate head-to-head trial.
Other Phase 3 developments
- TRIUMPH-3: Lilly reported topline results in adults with severe obesity and established cardiovascular disease, with or without type 2 diabetes. Average weight change reached 22.6% with 12 mg at 80 weeks, versus 3.2% with placebo. The cardiovascular event analyses were not conclusive and should not be read as proof of cardiovascular benefit.
- TRIUMPH-4: In adults with obesity or overweight and knee osteoarthritis without diabetes, Lilly reported improvements in both body weight and osteoarthritis pain. These findings require interpretation in the context of the full trial design and subsequent peer review.
- Ongoing programme: Studies are also examining obstructive sleep apnea, chronic low back pain, metabolic dysfunction-associated steatotic liver disease, kidney outcomes and longer-term cardiovascular outcomes.
What is known about safety?
Across the reported trials, the most common adverse events were gastrointestinal, including nausea, diarrhea, constipation and vomiting. In TRIUMPH-1, treatment discontinuation because of adverse events increased with dose and was reported in 4.1%, 6.9% and 11.3% of participants receiving 4 mg, 9 mg and 12 mg, respectively, compared with 4.9% receiving placebo. Dysesthesia—unusual skin sensations—was also reported more often with higher doses.
Clinical trials use eligibility rules, medical monitoring and controlled dose escalation. Their safety findings do not establish the safety of products sold outside the trial system, and longer-term or less common risks may become clearer only with additional data.
Is retatrutide approved or available?
No. As of 7 October 2026, retatrutide is not approved for public use. Lilly states that it is legally available only to participants in its clinical trials and has warned against products claiming to contain retatrutide outside those trials. Such products are not part of the regulated clinical programme and may have unverifiable identity, strength, purity or sterility.
Lilly has said it plans to submit a Biologics License Application to the US FDA in the first quarter of 2027. A planned submission is not an approval, and timing will depend on regulatory review.
What to watch next
The most important next steps are full peer-reviewed publication of additional Phase 3 datasets, completion of ongoing outcome trials, regulatory submissions, and independent assessment of benefit-risk across different patient groups. Until regulators complete that review, retatrutide should be described as an investigational medicine rather than an available treatment.
Sources
- Eli Lilly: What to know about retatrutide (updated September 2026)
- Eli Lilly: TRIUMPH-1 Phase 3 results
- The New England Journal of Medicine: TRIUMPH-1 peer-reviewed publication
- Eli Lilly: detailed TRIUMPH-2 results
- ClinicalTrials.gov: TRIUMPH-1 (NCT05929066)
This article is for educational and research reference only. It is not medical advice and does not support the purchase, use or self-administration of any unapproved product.
