Investigational · not FDA approved

Editorially reviewed · Last updated July 2026 · How we review

Retatrutide Phase 3 Trials 2026: TRIUMPH & TRANSCEND-T2D Tracker

Retatrutide Clinical Trials & Results

Q: Is retatrutide still in clinical trials?

Yes. Retatrutide is an investigational drug — it has not been approved by the FDA or any other regulator. It is being studied across the Phase 3 TRIUMPH and TRANSCEND programs, which began in 2023 and have enrolled more than 5,800 participants. TRIUMPH-4 (knee osteoarthritis) was the first Phase 3 trial to report results, in December 2025; Lilly has said seven additional Phase 3 trials in obesity and type 2 diabetes are expected to complete in 2026. A search of ClinicalTrials.gov shows retatrutide studies in a range of statuses — recruiting, active, and completed — confirming the program is ongoing.

Q: Is it safe to take retatrutide while it is still in Phase 3?

Retatrutide has not completed Phase 3 testing, and its full safety profile has not been established. The only setting in which it has been administered under medical supervision is clinical trials, where participants receive the drug at no cost and undergo regular in-person monitoring. In its December 2025 announcement, Lilly cautioned that there is "no guarantee that retatrutide will prove to be a safe and effective treatment" or that it "will receive regulatory approval." Anyone weighing retatrutide should discuss its investigational status and known side effects with a qualified healthcare provider. See Retatrutide Side Effects & Safety for the current data.

Q: How much weight did people lose in the pivotal TRIUMPH-1 obesity trial?

In TRIUMPH-1, the pivotal Phase 3 general-obesity trial (2,339 participants), the topline results reported on May 21, 2026 showed average weight loss at 80 weeks of 19.0% on 4 mg, 25.9% on 9 mg, and 28.3% (70.3 lbs) on 12 mg, versus 2.2% on placebo. At the 12 mg dose, 45.3% of participants lost 30% or more of their body weight. In a pre-specified extension to 104 weeks, 12 mg participants reached an average of 30.3% (85.0 lbs) with no weight-loss plateau. This is the largest weight loss reported in any retatrutide Phase 3 trial to date and forms the basis of Lilly's obesity regulatory submission.

Q: When will the retatrutide Phase 3 results be available?

The first Phase 3 results — TRIUMPH-4, in adults with obesity and knee osteoarthritis — were reported in December 2025, followed by TRANSCEND-T2D-1 (type 2 diabetes) in March 2026 and the pivotal TRIUMPH-1 obesity trial on May 21, 2026 (up to -28.3% weight loss at 80 weeks and -30.3% at 104 weeks on the 12 mg dose). Additional Phase 3 readouts, including TRIUMPH-2 and TRIUMPH-3, are still expected to complete through 2026. For how these readouts feed into the regulatory process, see Retatrutide FDA Approval Timeline.

Q: What adverse events were reported in retatrutide clinical trials?

Gastrointestinal events are the most common: in the Phase 2 obesity trial, nausea was reported in up to 45% of participants at the 12 mg maintenance dose (versus 11% on placebo), with vomiting (19%), constipation (16%), and diarrhea (15%) also dose-related. These events were mostly mild to moderate, clustered during dose escalation, and were partially mitigated by starting at 2 mg instead of 4 mg. Discontinuation due to adverse events ranged from 6% to 16% on retatrutide versus 0% on placebo. TRIUMPH-4 later added a dysesthesia signal (abnormal skin sensations) at 20.9% on 12 mg. See the adverse events section above for the full dose-by-dose tables.

Q: Were there any deaths or serious adverse events in the retatrutide trials?

In the Phase 2 obesity trial (NEJM 2023), serious adverse events occurred in 4% of participants in the retatrutide groups overall — the same rate as placebo — and one death was reported among 337 total participants, in a 4 mg group. In the Phase 2 type 2 diabetes trial (Lancet 2023), there were no deaths and no reports of severe hypoglycemia. Larger Phase 3 safety data, including the long-term TRIUMPH-5 cardiovascular outcomes trial, are still accumulating.

Last updated: June 11, 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

Trial	Phase	Indication	N	Duration	Status	Key Result
NCT04143802	1	T2D	—	12 wks	Complete	-8.5 kg weight loss; -0.9% HbA1c
NCT04881760	2	Obesity	338	48 wks	Complete	-24.2% weight loss at 12 mg
NCT04867785	2	Type 2 Diabetes	281	36 wks	Complete	-2.02% HbA1c; -16.94% weight loss at 12 mg
Phase 2 sub-study	2	MASLD/MASH	Sub-study	—	Complete	81-86% liver fat reduction
TRIUMPH-1	3	Obesity (basket: nested OSA/OA)	2,339	80 wks	Complete	-28.3% at 80 wks; -30.3% at 104 wks (12 mg)
TRIUMPH-2	3	Obesity in T2D (nested OSA)	—	—	Active	Results expected ~mid 2026
TRIUMPH-3	3	Obesity in CV disease	—	—	Active	Results expected 2026
TRIUMPH-4	3	Knee Osteoarthritis	445	68 wks	Complete	-28.7% weight loss; 74-76% pain reduction
TRIUMPH-5	3	CV/Renal Outcomes	—	Multi-year	Recruiting	MACE endpoints; long-term
TRIUMPH-6	3b	Weight Maintenance	643	—	Active	No longer recruiting
TRANSCEND-T2D-1	3	Type 2 Diabetes	—	40 wks	Complete	-1.7 to -2.0% HbA1c; -16.8% weight loss at 12 mg
Additional	3	Low back pain, MASLD	—	—	Planned	—

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:

Dose Group	Weight Change
Placebo	-2.1%
1 mg	-8.7%
4 mg (escalated from 2 mg)	-17.1%
4 mg (started at 4 mg)	-17.5%
8 mg (escalated from 2 mg)	-22.8%
8 mg (escalated from 4 mg)	-22.1%
12 mg (escalated from 2 mg)	-24.2%
12 mg (escalated from 4 mg)	-22.8%

Weight loss at 24 weeks (the primary endpoint, combined dose groups):

Dose Group	Weight Change at 24 Weeks
Placebo	-1.6%
1 mg	-7.2%
4 mg (combined)	-12.9%
8 mg (combined)	-17.3%
12 mg	-17.5%

Most of the dose separation was already visible by 24 weeks — and participants on the higher doses were still losing weight at 48 weeks, with no clear plateau.

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:

Dose	HbA1c Change	Achieving HbA1c < 5.7%
Placebo	-0.01%	—
12 mg	-2.02%	67%

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

Full dose-response data (least-squares mean changes):

Arm	HbA1c at 24 Weeks	Body Weight at 36 Weeks
Placebo	-0.01%	-3.00%
Dulaglutide 1.5 mg (active comparator)	-1.41%	-2.02%
Retatrutide 0.5 mg	-0.43%	-3.19%
Retatrutide 4 mg (escalated from 2 mg)	-1.39%	-7.92%
Retatrutide 4 mg (no escalation)	-1.30%	-10.37%
Retatrutide 8 mg (slow escalation)	-1.99%	-16.81%
Retatrutide 8 mg (fast escalation)	-1.88%	-16.34%
Retatrutide 12 mg (escalated from 2 mg)	-2.02%	-16.94%

HbA1c reductions with retatrutide were significantly greater than placebo at every dose except 0.5 mg, and greater than dulaglutide 1.5 mg in the 8 mg slow-escalation and 12 mg groups. Weight reductions at 4 mg and above beat both placebo and dulaglutide. Of 281 randomized participants, 84% completed the study and 79% completed study treatment.

Source: Rosenstock J, et al., The Lancet 2023 (abstract via PubMed)

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 -- RESULTS (May 2026)

Detail	Value
ClinicalTrials.gov	NCT05929066
Indication	Weight management (obesity, without type 2 diabetes)
Design	Phase 3, double-blind, placebo-controlled master trial with nested OSA and OA protocols
Participants	2,339 randomized (532 in a pre-specified 104-week extension)
Doses	4 mg (maintenance), 9 mg, 12 mg
Duration	80 weeks (extension to 104 weeks)
Status	Complete -- topline results reported May 21, 2026

TRIUMPH-1 is the pivotal general-obesity trial that forms the basis of Lilly's weight-management regulatory submission. On May 21, 2026, Lilly reported that it met its primary endpoint, delivering the largest average weight loss of any retatrutide Phase 3 trial to date.

Weight loss at 80 weeks (primary endpoint):

Group	Weight Change	Average Loss
4 mg	-19.0%	-47.2 lbs (-21.4 kg)
9 mg	-25.9%	-64.4 lbs (-29.2 kg)
12 mg	-28.3%	-70.3 lbs (-31.9 kg)
Placebo	-2.2%	-5.5 lbs (-2.5 kg)

At the 12 mg dose, 45.3% of participants achieved 30% or greater weight loss at 80 weeks — a threshold historically associated with bariatric surgery. Waist circumference fell by 6.4 to 9.5 inches across the active-treatment arms, versus 1.4 inches on placebo. In the pre-specified 104-week extension, participants on 12 mg reached an average of -30.3% (-85.0 lbs / -38.5 kg), with no weight-loss plateau observed.

The most common adverse events were gastrointestinal and dose-related: nausea (28.6% / 38.4% / 42.4% at 4 / 9 / 12 mg vs 14.8% on placebo) and diarrhea (25.2% / 34.1% / 32.0% vs 13.5%), mostly mild to moderate and clustered during dose escalation. For the full safety picture see Retatrutide Side Effects & Safety.

Per the trial design paper in Diabetes, Obesity and Metabolism (January 2026), TRIUMPH-1 is structured as a basket trial with nested obstructive-sleep-apnea and osteoarthritis protocols, generating data across multiple indications simultaneously. Lilly has said the TRIUMPH results support regulatory applications for obesity, OSA, and knee osteoarthritis, filed in 2026.

Source: Eli Lilly, "retatrutide delivered powerful weight loss in pivotal Phase 3 obesity trial," May 21, 2026

TRIUMPH-2 -- Obesity in Type 2 Diabetes

Detail	Value
Indication	Weight management in people with type 2 diabetes
Design	Basket trial with nested OSA protocol
Status	Active -- results expected ~mid 2026

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

Detail	Value
Indication	Weight management in people with cardiovascular disease
Status	Active -- results expected 2026

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)

Detail	Value
ClinicalTrials.gov	NCT05931367
Indication	Knee osteoarthritis in adults with obesity
Participants	445
Duration	68 weeks
Design	Double-blind, placebo-controlled
Status	Complete -- results reported December 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:

Group	Weight Change
9 mg	-26.4%
12 mg	-28.7%
Placebo	-2.1%

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):

Group	WOMAC Pain Reduction (points)	WOMAC Pain Reduction (%)	Completely Pain-Free
9 mg	-4.5	75.8%	14.1%
12 mg	-4.4	74.3%	12.0%
Placebo	-2.4	40.3%	4.2%

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

Detail	Value
Indication	Cardiovascular and renal outcomes
Duration	Multi-year
Primary endpoint	MACE (major adverse cardiovascular events)
Status	Recruiting / active

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

Detail	Value
Phase	3b
Indication	Maintenance of weight reduction
Participants	643 planned
Status	Active, no longer recruiting (as of Sep 2025)

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. This program will support a potential T2D indication filing, likely separate from the obesity filing.

TRANSCEND-T2D-1 reported results on March 19, 2026 — the first Phase 3 diabetes readout:

Endpoint	Result (40 weeks)
HbA1c reduction	-1.7% to -2.0% across doses
Weight loss at 12 mg	-16.8% (-36.6 lbs)
Weight-loss curve	No plateau through 40 weeks
Population	Adults with T2D (mean duration 2.5 years), not on other diabetes medications

See the full breakdown in TRANSCEND-T2D-1: Phase 3 Diabetes Results. Additional TRANSCEND trials are expected to read out through 2026.

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

Adverse Events Across Trials

The safety pattern is consistent across the published trials: gastrointestinal events dominate, they are dose-related, mostly mild to moderate, concentrated during dose escalation, and partially mitigated by starting at 2 mg rather than 4 mg.

Phase 2 obesity trial (NEJM 2023) — adverse events by maintenance dose (where a dose had two escalation arms, the range across both arms is shown):

Adverse Event	Placebo	1 mg	4 mg	8 mg	12 mg
Nausea	11%	14%	18–36%	17–60%	45%
Vomiting	1%	3%	12%	6–26%	19%
Diarrhea	11%	9%	12%	20%	15%
Constipation	3%	7%	6–15%	11%	16%
Decreased appetite	9%	13%	18–24%	11–31%	29%
Any adverse event	70%	84%	73–85%	80–94%	92%
Discontinued due to adverse events	0%	7%	6–9%	6–14%	16%

Serious adverse events were reported in 4% of participants in both the retatrutide groups overall and the placebo group. One death occurred among the 337 participants across all groups (in a 4 mg arm). Among adverse events of special interest, hyperesthesia or related events were reported in 6% of participants overall — rising to 13% at 12 mg, versus 1% on placebo — an early version of the sensory signal that later appeared as dysesthesia in TRIUMPH-4 (20.9% at 12 mg).

Phase 2 type 2 diabetes trial (Lancet 2023): mild-to-moderate gastrointestinal adverse events (nausea, diarrhea, vomiting, constipation) were reported in 35% of retatrutide participants — ranging from 13% at 0.5 mg to 50% in the 8 mg fast-escalation group — compared with 13% on placebo and 35% on dulaglutide 1.5 mg. There were no reports of severe hypoglycemia and no deaths during the study.

For what this means in practice — managing nausea, the escalation schedule, and the full side-effect picture — see Retatrutide Side Effects & Safety and Retatrutide Dosage Guide.

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.

Drug	Mechanism	Trial	Duration	Max Weight Loss	HbA1c Reduction
Retatrutide 12 mg	GIP + GLP-1 + Glucagon	Phase 2 (NEJM)	48 wks	-24.2%	N/A (non-T2D)
Retatrutide 12 mg	GIP + GLP-1 + Glucagon	TRIUMPH-4 (Phase 3)	68 wks	-28.7%	N/A
Tirzepatide 15 mg (Mounjaro/Zepbound)	GIP + GLP-1	SURMOUNT-1 (Phase 3)	72 wks	-22.5%	N/A (non-T2D)
Semaglutide 2.4 mg (Wegovy)	GLP-1	STEP 1 (Phase 3)	68 wks	-14.9%	N/A (non-T2D)
Retatrutide 12 mg	GIP + GLP-1 + Glucagon	Phase 2 (Lancet)	36 wks	-16.94% (T2D)	-2.02%
Tirzepatide 15 mg	GIP + GLP-1	SURPASS-1 (Phase 3)	40 wks	—	-2.07%
Semaglutide 1 mg (Ozempic)	GLP-1	SUSTAIN 1-5	30-56 wks	—	-1.5 to -1.8%

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

What's Next: Upcoming Readouts in 2026

As of mid-2026, the pivotal readouts have started to land: TRANSCEND-T2D-1 (type 2 diabetes) reported in March 2026, and TRIUMPH-1 (pivotal obesity) reported topline results on May 21, 2026 (up to -30.3% at 104 weeks). The remaining Phase 3 readouts still expected in 2026 include:

TRIUMPH-2 (obesity in T2D with nested OSA)
TRIUMPH-3 (obesity in CV disease population)
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.

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:

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.
Lilly's trial finder — Visit LillyTrialGuide.com for Lilly-sponsored studies. You can search by condition and location to find sites near you.
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.

Frequently Asked Questions

Is retatrutide still in clinical trials?

Yes. Retatrutide is an investigational drug — it has not been approved by the FDA or any other regulator. It is being studied across the Phase 3 TRIUMPH and TRANSCEND programs, which began in 2023 and have enrolled more than 5,800 participants. TRIUMPH-4 (knee osteoarthritis) was the first Phase 3 trial to report results, in December 2025; Lilly has said seven additional Phase 3 trials in obesity and type 2 diabetes are expected to complete in 2026. A search of ClinicalTrials.gov shows retatrutide studies in a range of statuses — recruiting, active, and completed — confirming the program is ongoing.

Is it safe to take retatrutide while it is still in Phase 3?

Retatrutide has not completed Phase 3 testing, and its full safety profile has not been established. The only setting in which it has been administered under medical supervision is clinical trials, where participants receive the drug at no cost and undergo regular in-person monitoring. In its December 2025 announcement, Lilly cautioned that there is "no guarantee that retatrutide will prove to be a safe and effective treatment" or that it "will receive regulatory approval." Anyone weighing retatrutide should discuss its investigational status and known side effects with a qualified healthcare provider. See Retatrutide Side Effects & Safety for the current data.

How much weight did people lose in the pivotal TRIUMPH-1 obesity trial?

In TRIUMPH-1, the pivotal Phase 3 general-obesity trial (2,339 participants), the topline results reported on May 21, 2026 showed average weight loss at 80 weeks of 19.0% on 4 mg, 25.9% on 9 mg, and 28.3% (70.3 lbs) on 12 mg, versus 2.2% on placebo. At the 12 mg dose, 45.3% of participants lost 30% or more of their body weight. In a pre-specified extension to 104 weeks, 12 mg participants reached an average of 30.3% (85.0 lbs) with no weight-loss plateau. This is the largest weight loss reported in any retatrutide Phase 3 trial to date and forms the basis of Lilly's obesity regulatory submission.

When will the retatrutide Phase 3 results be available?

The first Phase 3 results — TRIUMPH-4, in adults with obesity and knee osteoarthritis — were reported in December 2025, followed by TRANSCEND-T2D-1 (type 2 diabetes) in March 2026 and the pivotal TRIUMPH-1 obesity trial on May 21, 2026 (up to -28.3% weight loss at 80 weeks and -30.3% at 104 weeks on the 12 mg dose). Additional Phase 3 readouts, including TRIUMPH-2 and TRIUMPH-3, are still expected to complete through 2026. For how these readouts feed into the regulatory process, see Retatrutide FDA Approval Timeline.

What adverse events were reported in retatrutide clinical trials?

Gastrointestinal events are the most common: in the Phase 2 obesity trial, nausea was reported in up to 45% of participants at the 12 mg maintenance dose (versus 11% on placebo), with vomiting (19%), constipation (16%), and diarrhea (15%) also dose-related. These events were mostly mild to moderate, clustered during dose escalation, and were partially mitigated by starting at 2 mg instead of 4 mg. Discontinuation due to adverse events ranged from 6% to 16% on retatrutide versus 0% on placebo. TRIUMPH-4 later added a dysesthesia signal (abnormal skin sensations) at 20.9% on 12 mg. See the adverse events section above for the full dose-by-dose tables.

Were there any deaths or serious adverse events in the retatrutide trials?

In the Phase 2 obesity trial (NEJM 2023), serious adverse events occurred in 4% of participants in the retatrutide groups overall — the same rate as placebo — and one death was reported among 337 total participants, in a 4 mg group. In the Phase 2 type 2 diabetes trial (Lancet 2023), there were no deaths and no reports of severe hypoglycemia. Larger Phase 3 safety data, including the long-term TRIUMPH-5 cardiovascular outcomes trial, are still accumulating.

Sources

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
Jastreboff AM, et al. "Triple-hormone-receptor agonist retatrutide for obesity." New England Journal of Medicine. 2023. Full text
Rosenstock J, et al. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes." The Lancet. 2023. Full text
Retatrutide liver fat sub-study. Nature Medicine. 2024. Full text
Eli Lilly. "Lilly's triple agonist retatrutide delivered weight loss average..." Investor Relations. December 2025. Press release
Eli Lilly. "Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial (TRIUMPH-1)." Investor Relations. May 21, 2026. Press release
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.

How we keep this honest

What this is: Educational information, not medical advice. It reports published research — it doesn’t recommend that you use, obtain, or supply anything.
Regulatory status: Retatrutide and similar peptides are investigational — not approved by the FDA or any regulator. Semaglutide and tirzepatide are prescription-only medicines, available only through a licensed prescriber.
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