Retatrutide Clinical Trials & Results

Last updated: February 14, 2026

Retatrutide (LY3437943) is Eli Lilly's investigational triple hormone receptor agonist targeting GIP, GLP-1, and glucagon receptors. It is the most advanced triple agonist in clinical development, with Phase 2 results showing up to 24.2% weight loss and a large Phase 3 program (TRIUMPH) underway across multiple indications.

This page is a living tracker of every retatrutide clinical trial, from Phase 1 through the ongoing Phase 3 TRIUMPH program. We update it as new data is published or presented.

For a full explanation of how retatrutide works, see What is Retatrutide (GLP-3)?. For a comparison with existing drugs, see Retatrutide vs Mounjaro vs Ozempic.

Trial Summary Table

Total TRIUMPH Phase 3 enrollment: ~5,800 participants across all trials.

Phase 1: First in Human

NCT04143802 | Published: The Lancet, 2022 (Coskun et al.)

The first-in-human study of retatrutide was a single- and multiple-ascending-dose trial in patients with type 2 diabetes.

Key findings:

• Up to approximately 8.5 kg weight loss over 12 weeks at the highest doses tested
• HbA1c reduction of up to approximately 0.9%
• Acceptable safety and tolerability profile, supporting advancement to Phase 2

These results were notable because they demonstrated meaningful metabolic effects even in a short, dose-finding study, suggesting the triple agonist mechanism was producing clinically relevant signals early.

Source: Coskun et al., The Lancet 2022

Phase 2 Results

Phase 2 -- Obesity (NEJM 2023)

NCT04881760 | Published: New England Journal of Medicine, 2023 (Jastreboff AM, et al.)

This was the landmark Phase 2 trial that put retatrutide on the map. A 48-week, randomized, double-blind, placebo-controlled study in 338 adults with obesity (BMI >= 30) or overweight (BMI >= 27) with at least one weight-related comorbidity. Participants did not have type 2 diabetes.

Weight loss results at 48 weeks:

Categorical weight loss at 12 mg (from 2 mg escalation):

• 100% of participants lost >= 5% body weight
• ~93% lost >= 10%
• ~83% lost >= 15%
• ~63% lost >= 20%

Additional metabolic improvements:

• Improved lipid profiles
• Reduced blood pressure
• Improved insulin sensitivity

The 24.2% mean weight loss at 48 weeks exceeded published results for both semaglutide 2.4 mg (STEP 1: -14.9% at 68 weeks) and tirzepatide 15 mg (SURMOUNT-1: -22.5% at 72 weeks) in their respective Phase 3 obesity trials, though cross-trial comparisons have limitations. For a detailed comparison, see Retatrutide vs Mounjaro vs Ozempic.

Source: Jastreboff AM, et al., NEJM 2023

Phase 2 -- Type 2 Diabetes (Lancet 2023)

NCT04867785 | Published: The Lancet, 2023 (Rosenstock J, et al.)

A 36-week, randomized trial in 281 participants with type 2 diabetes.

HbA1c results:

Achieving HbA1c < 5.7% is significant because it represents normoglycemia -- blood sugar levels in the non-diabetic range. Two-thirds of participants on the highest dose reached this threshold.

Weight loss:

• Up to -16.94% at 12 mg (over 36 weeks)
• This degree of weight loss in a type 2 diabetes population is particularly notable, as patients with T2D typically lose less weight on anti-obesity medications than those without diabetes

Source: Rosenstock J, et al., The Lancet 2023

Phase 2 -- Liver Fat (MASLD/MASH)

Sub-study from the Phase 2 program | Presented at EASL and ADA 2024 | Published in Nature Medicine

Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly NAFLD) and its more severe form MASH (formerly NASH) are closely linked to obesity and metabolic syndrome. This sub-study evaluated retatrutide's effect on liver fat content measured by MRI-PDFF.

Key findings:

• 81-86% relative reduction in liver fat at higher doses
• 78-90% of participants achieved >= 30% reduction in liver fat
• 52-69% achieved liver fat normalization (< 5% by MRI-PDFF)

These results are among the strongest liver fat reductions reported for any pharmacotherapy, suggesting retatrutide's glucagon receptor activity may provide direct hepatic benefits beyond what is achieved through weight loss alone.

Source: Nature Medicine 2024

Phase 3: The TRIUMPH Program

Eli Lilly launched the TRIUMPH Phase 3 program in 2023, enrolling approximately 5,800 participants across multiple indications. This is one of the largest obesity drug development programs ever conducted.

"With 7 additional phase 3 readouts expected in 2026..." -- Kenneth Custer, PhD, EVP Lilly Cardiometabolic Health

For how the TRIUMPH timeline fits into the broader regulatory picture, see Retatrutide FDA Approval Timeline.

TRIUMPH-1 -- Obesity

TRIUMPH-1 is the pivotal obesity trial that will form the basis of Lilly's regulatory submission. Per the trial design paper published in Diabetes, Obesity and Metabolism (January 2026), it is structured as a basket trial with nested protocols for obstructive sleep apnea and osteoarthritis — meaning it will generate data across multiple indications simultaneously. Lilly confirmed on its Q4 2025 earnings call that TRIUMPH results will be submitted in 2026 to support regulatory applications.

TRIUMPH-2 -- Obesity in Type 2 Diabetes

TRIUMPH-2 evaluates retatrutide for weight management in people with type 2 diabetes, with a nested obstructive sleep apnea protocol. This complements TRIUMPH-1 by covering the T2D population and will support both obesity and diabetes-related regulatory filings.

TRIUMPH-3 -- Cardiovascular Disease Population

TRIUMPH-3 evaluates retatrutide for weight management in a cardiovascular disease population. This trial is important for establishing retatrutide's safety and efficacy in higher-risk patients and could support a broader label if the results are positive.

TRIUMPH-4 -- Knee Osteoarthritis -- RESULTS (Dec 2025)

TRIUMPH-4 was the first Phase 3 TRIUMPH trial to report results. It evaluated retatrutide in patients with both obesity and knee osteoarthritis.

Weight loss results:

The 28.7% mean weight loss at 12 mg over 68 weeks is the largest reported in any Phase 3 obesity trial to date.

Pain outcomes (WOMAC pain score):

Additional findings:

• Systolic blood pressure reduced by 14 mmHg at 12 mg
• Improved non-HDL cholesterol, triglycerides, and hsCRP (a marker of inflammation)

New safety signal -- dysesthesia:

Dysesthesia (abnormal sensations such as burning, tingling, or numbness) emerged as a new adverse event in this trial:

• 8.8% at 9 mg
• 20.9% at 12 mg
• 0.7% at placebo

This dose-dependent signal will be closely watched in future trial readouts. For more detail on retatrutide safety data, see Retatrutide Side Effects & Safety.

Source: Lilly Investor Relations, December 2025

TRIUMPH-5 -- Cardiovascular / Renal Outcomes

TRIUMPH-5 is a long-term cardiovascular outcomes trial (CVOT). These trials are now standard in the GLP-1 drug class -- semaglutide's SELECT trial demonstrated a 20% reduction in MACE, leading to a cardiovascular indication for Wegovy. A positive CVOT for retatrutide would significantly expand its market and clinical utility.

TRIUMPH-6 -- Weight Maintenance

Weight regain after stopping GLP-1-class medications is a known challenge. TRIUMPH-6 will evaluate whether and how retatrutide can maintain weight loss long-term, which is critical for real-world clinical use.

Additional TRIUMPH and Other Phase 3 Trials

Lilly has initiated or announced additional Phase 3 trials for retatrutide:

• Chronic low back pain -- Phase 3 initiated in Q3 2025
• Overweight/obesity (additional) -- new Phase 3 trial initiated in Q3 2025
• MASLD (metabolic dysfunction-associated steatotic liver disease) -- building on the strong Phase 2 liver fat data

TRANSCEND Program -- Type 2 Diabetes

Separate from the TRIUMPH program, Lilly is running the TRANSCEND Phase 3 program evaluating retatrutide specifically for type 2 diabetes. Multiple TRANSCEND trials are expected to read out in 2026. This program will support a potential T2D indication filing, likely separate from the obesity filing.

These trials are expected to further broaden retatrutide's potential label across metabolic, musculoskeletal, and liver disease indications.

How Retatrutide Compares

The table below provides a high-level comparison of retatrutide Phase 2 results against approved drugs' Phase 3 results. Cross-trial comparisons have limitations (different populations, durations, designs), but they provide useful context.

For a full breakdown, see Retatrutide vs Mounjaro vs Ozempic.

What's Next: Upcoming Readouts in 2026

Lilly confirmed on its Q4 2025 earnings call (February 4, 2026) that six additional Phase 3 readouts are expected in 2026, including:

• TRIUMPH-1 (pivotal obesity trial with nested OSA and OA)
• TRIUMPH-2 (obesity in T2D with nested OSA)
• TRIUMPH-3 (obesity in CV disease population)
• TRANSCEND program trials (dedicated type 2 diabetes)
• Additional readouts across other indications

Lilly confirmed it plans to submit regulatory applications in 2026 based on the core TRIUMPH results, supporting filings for obesity, obstructive sleep apnea, and knee osteoarthritis. Potential FDA approval in 2027.

For the full regulatory timeline, see Retatrutide FDA Approval Timeline.

How to Sign Up for Retatrutide Clinical Trials

If you are interested in retatrutide trial sign-up, several TRIUMPH trials are still recruiting or active. Here is how to find a retatrutide clinical trial near you:

1. ClinicalTrials.gov — Search for "retatrutide" on ClinicalTrials.gov to see all registered trials, locations, and eligibility criteria. Filter by "Recruiting" status to find trials currently accepting participants.
2. Lilly's trial finder — Visit LillyTrialGuide.com for Lilly-sponsored studies. You can search by condition and location to find sites near you.
3. Ask your doctor — Your physician can help determine if you meet eligibility criteria and refer you to a trial site.

Important: Clinical trial participation means you may receive a placebo rather than the active drug. Trials also require regular in-person visits at a designated study site. The drug is provided at no cost to participants.

For information on expected pricing and access after approval, see Retatrutide Cost & How to Get It.

Sources

1. Coskun T, et al. "LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist for glycemic control and weight loss." The Lancet. 2022. Full text
2. Jastreboff AM, et al. "Triple-hormone-receptor agonist retatrutide for obesity." New England Journal of Medicine. 2023. Full text
3. Rosenstock J, et al. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes." The Lancet. 2023. Full text
4. Retatrutide liver fat sub-study. Nature Medicine. 2024. Full text
5. Eli Lilly. "Lilly's triple agonist retatrutide delivered weight loss average..." Investor Relations. December 2025. Press release
6. ClinicalTrials.gov. Retatrutide trials

This page is for informational purposes only and does not constitute medical advice. Retatrutide is an investigational drug that has not been approved by the FDA or any other regulatory agency. Clinical trial results are preliminary and subject to change upon full publication and regulatory review. Always consult a qualified healthcare provider before making decisions about your health or participation in clinical trials.