Retatrutide Clinical Trials 2026: Every Phase 3 Study Tracked

Retatrutide FDA Approval Status: Phase 3 Results, NDA Timeline & What Comes Next

Last updated: March 14, 2026. This is a living tracker. We update this page as new data and trial results become available.

Key takeaways:

• Eli Lilly is running 7+ Phase 3 clinical trials for retatrutide (LY3437943) across multiple indications.
• The first Phase 3 results dropped in February 2026. Participants lost up to 28.7% of body weight at the 12 mg dose. Pain scores in knee osteoarthritis patients dropped by 75.8%.
• Phase 2 data published in the New England Journal of Medicine (PMID: 37385275) showed up to 24.2% weight loss. That data triggered the entire Phase 3 program.
• Most remaining Phase 3 readouts are expected throughout 2026.
• An NDA submission to the FDA could come as early as mid-to-late 2026. Full approval is possible by mid-2027.

Important: This article is for informational purposes only. It is not medical advice. Retatrutide is an investigational compound not yet approved by the FDA for any indication. All clinical trial data discussed here comes from publicly available sources, including ClinicalTrials.gov and published peer-reviewed research. See our full medical disclaimer.

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What is retatrutide?

Retatrutide is a triple hormone receptor agonist developed by Eli Lilly. It activates three receptors at once: GLP-1, GIP, and glucagon. This makes it different from tirzepatide (Mounjaro/Zepbound), which only targets two of those three receptors. For a broader look at this compound, see our retatrutide guide.

The addition of glucagon receptor activation is significant. Glucagon increases energy expenditure and promotes fat breakdown in the liver. In theory, this triple mechanism could produce greater weight loss and broader metabolic benefits than dual agonists.

For a full compound overview, see our retatrutide guide.

Phase 2 recap: the data that started it all

Before we get into the Phase 3 program, here is the foundation it was built on.

The Phase 2 trial enrolled 338 adults with obesity. It ran for 48 weeks and tested multiple doses of retatrutide against placebo. The results were published in the New England Journal of Medicine in July 2023 (PMID: 37385275).

Dose	Weight Loss at 48 Weeks
Placebo	-2.1%
4 mg	-17.1%
8 mg	-22.8%
12 mg	-24.2%

The 24.2% weight loss figure at the highest dose was the largest ever recorded in a controlled obesity trial at the time. For context, semaglutide (Wegovy) showed about 15% in its pivotal trial, and tirzepatide (Zepbound) showed about 22.5%.

The side effect profile was mostly gastrointestinal. Nausea, diarrhea, and vomiting were the most common adverse events, consistent with the GLP-1 drug class.

These Phase 2 results gave Eli Lilly the confidence to launch a massive Phase 3 clinical program.

Phase 3 trials: the full tracker

Eli Lilly's Phase 3 program for retatrutide is called TRIUMPH. It spans multiple indications beyond just obesity. Here is every major trial we are tracking.

NCT05882045: Obesity + knee osteoarthritis (FIRST RESULTS)

Status: Results reported, February 2026

This was the first Phase 3 trial to report results. It studied retatrutide in adults with obesity who also had knee osteoarthritis.

The headline numbers:

• 28.7% body weight loss at the 12 mg dose
• 75.8% reduction in knee pain (measured by WOMAC pain score)
• Treatment duration: 48 weeks

These results exceeded even the Phase 2 data. The weight loss figure jumped from 24.2% in Phase 2 to 28.7% in this larger Phase 3 population. The knee osteoarthritis pain reduction adds a second potential indication for the drug beyond weight management.

For more context on what these numbers mean, see our retatrutide weight loss results breakdown.

NCT06383390: Obesity (primary weight loss trial)

Status: Ongoing, results expected 2026

This is the big one. This trial is the primary obesity study that Eli Lilly will likely use as the backbone of its NDA submission. It is testing retatrutide specifically for weight management in adults with obesity or overweight with at least one weight-related comorbidity.

We expect this to be the largest and most closely watched readout in the TRIUMPH program.

Type 2 diabetes trials

Status: Ongoing

Separate Phase 3 trials are studying retatrutide for glycemic control in adults with type 2 diabetes. Given the GLP-1 component and the success of tirzepatide in the diabetes space, Eli Lilly is pursuing a diabetes indication in parallel with obesity.

NASH/MASH (metabolic liver disease)

Status: Ongoing

Retatrutide is being studied for non-alcoholic steatohepatitis, now called metabolic dysfunction-associated steatohepatitis (MASH). The glucagon receptor activation is particularly relevant here. Glucagon plays a role in liver fat metabolism, which makes retatrutide a strong candidate for this indication.

Sleep apnea

Status: Ongoing

Obstructive sleep apnea is closely linked to obesity. A trial is evaluating whether the weight loss from retatrutide translates into meaningful improvements in sleep apnea severity, similar to what tirzepatide demonstrated in its own sleep apnea trials.

Cardiovascular outcomes

Status: Ongoing (long-term study)

A cardiovascular outcomes trial (CVOT) is underway. These trials take longer because they measure hard endpoints like heart attack, stroke, and cardiovascular death over extended follow-up periods. This data will be important for insurance coverage and broader prescribing.

How to read clinical trial results

If you are following these trials, it helps to understand a few key terms.

Primary endpoint. This is the main question the trial is designed to answer. For the obesity trials, the primary endpoint is usually percent change in body weight from baseline. If the drug hits its primary endpoint with statistical significance, the trial is considered a success.

Secondary endpoints. These are additional measurements the trial tracks. Examples include waist circumference, blood pressure, A1C levels, or quality-of-life scores. Hitting secondary endpoints strengthens the overall case for the drug.

Statistical significance. A result is considered statistically significant when the probability of it occurring by chance is very low (typically less than 5%, expressed as p < 0.05). When a trial reports a statistically significant result, it means the effect is very likely real and not random noise.

Intention-to-treat analysis. Most trials report results based on everyone who was enrolled, even if some participants dropped out. This is a more conservative and more honest way to report data.

What do these trials mean for approval?

The FDA requires positive Phase 3 data to approve a new drug. With the osteoarthritis trial already reporting positive results and multiple other TRIUMPH trials expected to read out in 2026, Eli Lilly is building the dataset needed for an NDA submission.

For the full breakdown of NDA requirements, tirzepatide precedent comparison, and best-case vs. realistic timeline scenarios, see our retatrutide FDA approval timeline analysis.

If you are interested in accessing retatrutide now through clinical trial enrollment or other pathways, see our guide to getting retatrutide in 2026.

Frequently asked questions

How many retatrutide clinical trials are running right now?

At least 7 Phase 3 trials are active under the TRIUMPH program. They cover obesity, type 2 diabetes, MASH (liver disease), sleep apnea, cardiovascular outcomes, and obesity with knee osteoarthritis.

Has any retatrutide Phase 3 trial reported results?

Yes. The first Phase 3 trial (NCT05882045, obesity with knee osteoarthritis) reported results in February 2026. Participants on the 12 mg dose lost 28.7% of their body weight and experienced a 75.8% reduction in knee pain.

When will retatrutide be FDA approved?

No approval date has been set. The earliest realistic window is mid-2027 based on current trial timelines. See our full FDA approval timeline analysis for the detailed breakdown.

Can I get retatrutide now?

Not through a pharmacy. See our complete guide to accessing retatrutide in 2026 for current pathways including clinical trial enrollment.

How does retatrutide compare to semaglutide and tirzepatide for weight loss?

Phase 2 data showed 24.2% weight loss with retatrutide at 48 weeks. Phase 3 data showed 28.7% in the osteoarthritis population. For comparison, semaglutide showed about 15% and tirzepatide about 22.5% in their respective pivotal trials. For a detailed comparison, see our retatrutide for weight loss breakdown. For a ranked overview of where retatrutide fits among all available weight loss options, see our evidence-based ranking of the best peptides for weight loss in 2026.

What are the side effects of retatrutide?

The most common side effects reported in trials are gastrointestinal: nausea, diarrhea, vomiting, and constipation. These are consistent with the GLP-1 drug class. Most side effects were mild to moderate and decreased over time with dose escalation. See our retatrutide side effects page for the full breakdown.

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Medical Disclaimer: The information on this website is for educational and informational purposes only. It is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any peptide protocol, medication, or supplement regimen. Individual results vary. We share published research and publicly available clinical trial information. This is not a medical recommendation.

Sources

1. Retatrutide Phase 2 trial results - New England Journal of Medicine, 2023 (PMID: 37385275)
2. NCT05882045: Retatrutide in obesity with knee osteoarthritis - ClinicalTrials.gov
3. NCT06383390: Retatrutide for obesity - ClinicalTrials.gov