Retatrutide: what the research shows
An experimental “triple” hormone medicine that has produced some of the largest weight losses ever seen in a drug trial.
Also known as LY3437943, often called “triple G”
At a glance
24.2%
average weight lost in 48 weeks (12 mg)
Phase 2 trial, 338 adults · placebo: 2.1%
Not approved anywhere yet. Eli Lilly has reported positive results from its large phase 3 trials and plans to apply for US approval by early 2027.
What is Retatrutide?
Retatrutide is an experimental medicine made by Eli Lilly. It acts on three hormone targets at once: GLP-1, GIP and glucagon.
How does Retatrutide work?
GLP-1 and GIP reduce appetite and help control blood sugar. Glucagon is thought to make the body burn more energy, including fat stored in the liver. Together they work on appetite and on energy use at the same time.
What does the research show?
- In a 2023 phase 2 trial, 338 adults with obesity took retatrutide for 48 weeks. People on the highest dose (12 mg) lost 24.2% of their body weight on average, compared with 2.1% on placebo.
- In May 2026 Lilly reported early results from the first big phase 3 trial, TRIUMPH-1, with 2,339 adults: 28.3% average weight loss after 80 weeks on 12 mg. These are company results and have not yet been published in a medical journal.
- Two more phase 3 trials (July 2026) showed average weight loss of up to 20.8% in people with type 2 diabetes and up to 22.6% in people with heart disease, compared with 4.0% and 3.2% on placebo.
How do the weight-loss results compare?
Each medicine compared with a placebo in its own trial. Ordered by reported average; this is not a head-to-head ranking.
- Medicine
- Placebo
Retatrutide · Experimental
12 mg weekly
Phase 2 · 48 weeks · 338 people
Tirzepatide · Approved
15 mg weekly (Zepbound)
SURMOUNT-1 · 72 weeks · 2,539 people
Semaglutide · Approved
2.4 mg weekly injection (Wegovy)
STEP 1 · 68 weeks · 1,961 people
Semaglutide · Approved (US)
25 mg daily pill (Wegovy pill)
OASIS 4 · 64 weeks · 307 people
Average body weight lost
Each human trial had different people, doses and lengths, so compare with care. The bars describe approved or experimental medicines studied under medical supervision with diet and exercise advice, not laboratory research products. They use full journal reports; conference findings and different endpoints appear separately below.
Show these numbers as a table
| Medicine | Trial | People | Weeks | Medicine | Placebo | Source |
|---|---|---|---|---|---|---|
| Retatrutide, 12 mg weekly | Phase 2 | 338 | 48 | 24.2% | 2.1% | PubMed |
| Tirzepatide, 15 mg weekly (Zepbound) | SURMOUNT-1 | 2,539 | 72 | 20.9% | 3.1% | PubMed |
| Semaglutide, 2.4 mg weekly injection (Wegovy) | STEP 1 | 1,961 | 68 | 14.9% | 2.4% | PubMed |
| Semaglutide, 25 mg daily pill (Wegovy pill) | OASIS 4 | 307 | 64 | 13.6% | 2.2% | PubMed |
PTT-A and CBL-514: evidence so far
Neither has a comparable average human body-weight-loss result in the research below. Animal body weight and human fat volume measure different things, so they are shown separately from the bars.
Animal research · conference abstract
PTT-A
- Average human body-weight loss
- Not established in the cited research
- What was measured
- Body weight in diet-induced obese rats over 21 days
- Reported finding
- Body weight was 19.2% lower versus vehicle at the higher studied exposure; tirzepatide was 12.1% lower versus vehicle in the same experiment.
A difference versus vehicle in rats is not average weight lost by people. It cannot establish superiority to retatrutide in humans.
Human fat-volume subgroup · conference report
CBL-514
- Average human body-weight loss
- Not established by this fat-volume result
- What was measured
- MRI-measured visceral-fat volume, four weeks after final treatment
- Reported finding
- Visceral-fat volume fell 12.01%; placebo rose 5.68%. The small phase 2 subgroup had 40 participants with later follow-up data.
12.01% less visceral fat is not 12.01% less body weight. CBL-514 is an experimental small molecule, not a peptide.
Known risks and side effects
- Stomach side effects are common and increase with the dose. In TRIUMPH-1, 42% of people on the top dose had nausea, compared with 15% on placebo.
- More people stopped the top dose because of side effects: 11.3%, compared with 4.9% on placebo.
- The phase 2 trial also saw a dose-related rise in heart rate.
- Long-term safety is still being studied, and it is not an approved medicine.
Is Retatrutide approved?
Tested in people, but not approved as a medicine.
Not approved anywhere yet. Eli Lilly has reported positive results from its large phase 3 trials and plans to apply for US approval by early 2027.
From the community
Watch: Retatrutide and related science
Start with the compound discussion, then use the background lesson to understand its biology. Each card explains its connection. Recordings may predate later findings or regulatory changes.
Dr Brad Stanfield
Retatrutide: interpreting the newer trial results
A physician reviews retatrutide results. Read the linked trial reports for the population, follow-up and analysis used.
Brad Stanfield, MBChB · general practitioner
Discusses the compound
Discusses Retatrutide or its clinical context. Read the original studies linked here for the exact formulation, population and outcomes.
Dr Brad Stanfield
Retatrutide weight-loss truth
A GP reads the retatrutide trial data and what it does and doesn’t show.
Brad Stanfield, MBChB, general practitioner
Discusses the compound
Discusses Retatrutide or its clinical context. Read the original studies linked here for the exact formulation, population and outcomes.
Ohio State Wexner Medical Center
What is a GLP-1 agonist, and how does it work?
A hospital explainer of GLP-1 signalling, appetite and blood-sugar regulation.
Allison L. Rhodes, MD · obesity medicine
Related biology
Background on GLP-1 signalling for understanding Retatrutide. It does not demonstrate benefits of this compound or formulation.
Sources and references
- Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 TrialJastreboff et al. · New England Journal of Medicine · 2023
- TRIUMPH-1: phase 3 retatrutide topline resultsEli Lilly and Company · original sponsor announcement · May 21, 2026
- TRIUMPH-2 and TRIUMPH-3: phase 3 retatrutide topline resultsEli Lilly and Company · original sponsor announcement · July 23, 2026
VETUD Learn explains published research in plain language. It is general information, not medical advice. Talk to a doctor before starting, stopping or changing any treatment.
In the research shop
Check the catalog for related laboratory research materials. These products are separate from the approved medicines and clinical trial formulations discussed here.
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