Retatrutide Phase 3 Results: What the 2026 Trials Found and Its Current FDA Status

Written by the NuLab Editorial Team · Published July 31, 2026 · Last reviewed July 31, 2026

Five Phase 3 studies have now produced positive results, but most of the pivotal obesity findings remain sponsor-reported topline data. Retatrutide is still investigational, is not FDA approved, and has no confirmed U.S. availability date.

Quick answer: Retatrutide is not FDA approved as of July 31, 2026. Lilly has reported positive Phase 3 findings from TRANSCEND-T2D-1 and TRIUMPH-1, -2, -3, and -4. At the highest studied arms, sponsor-reported efficacy-estimand results included average weight changes of -28.3% at 80 weeks in TRIUMPH-1, -20.8% in TRIUMPH-2, -22.6% in TRIUMPH-3, and -28.7% at 68 weeks in TRIUMPH-4. TRANSCEND-T2D-1 also reported A1C reductions of up to 2.0 percentage points at 40 weeks. Lilly says it plans to submit a Biologics License Application to FDA in the first quarter of 2027. A planned submission is not an approval, and neither Lilly nor FDA has announced a U.S. launch date.

Current status: Retatrutide remains an investigational drug. FDA states that it is not a component of an FDA-approved drug, has not been found safe and effective for any condition, and cannot be used in compounding under federal law.

In this review

• What changed in 2026
• How to read the reported numbers
• Phase 3 results through July 31, 2026
• What the safety reports showed
• What the results do not establish
• Is retatrutide FDA approved?
• When will retatrutide be available?
• Retatrutide FAQs

What changed in 2026

Retatrutide is a single investigational peptide designed to activate the receptors for glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1, and glucagon. Its Phase 3 program is divided mainly between the TRIUMPH studies in obesity and related complications and the TRANSCEND studies in type 2 diabetes.

The public evidence changed quickly during the first seven months of 2026:

• On March 19, Lilly announced topline results from TRANSCEND-T2D-1 in adults with type 2 diabetes whose blood glucose was inadequately controlled with diet and exercise.
• On May 21, Lilly reported the main TRIUMPH-1 obesity results and a prespecified extension in a narrower subgroup.
• On June 6, detailed TRANSCEND-T2D-1 results were published in The Lancet, making it the first peer-reviewed Phase 3 retatrutide report identified in this review.
• On July 23, Lilly announced topline findings from TRIUMPH-2 and TRIUMPH-3 and stated that it planned a U.S. regulatory submission in the first quarter of 2027.

TRIUMPH-4, reported in December 2025, remains part of the five-study Phase 3 picture because it was the first successful Phase 3 readout and evaluated obesity with knee osteoarthritis.

“Positive Phase 3 results” is therefore accurate, but it needs a qualifier. TRANSCEND-T2D-1 has a peer-reviewed publication. The evidence cited here for the main TRIUMPH-1, TRIUMPH-2, TRIUMPH-3, and TRIUMPH-4 results is sponsor-reported topline data; complete peer-reviewed trial reports for those findings were not identified in this review.

How to read the reported numbers

Clinical-trial summaries can look inconsistent when different statistical estimands are placed side by side. An estimand defines the treatment effect a trial analysis is trying to estimate, including how it handles events such as discontinuation or use of another treatment.

Lilly's topline tables commonly lead with an efficacy estimand. In the releases reviewed here, that estimates what the average result would have been if all randomized participants had remained on the assigned study intervention, with allowed interruptions or modifications, and had not started prohibited rescue or weight-management treatments.

A treatment-regimen estimand asks a broader, more pragmatic question by estimating the average effect regardless of adherence or certain post-randomization events. It can produce a different number from the efficacy estimand even when both analyses come from the same trial.

The summary table below uses efficacy-estimand results for consistency. It does not imply that this is the only valid analysis. Where the peer-reviewed TRANSCEND-T2D-1 publication provides treatment-regimen results, those are described separately.

The trials also enrolled different populations, ran for different lengths of time, and measured different primary outcomes. Their percentages should not be treated as head-to-head rankings.

Retatrutide Phase 3 results through July 31, 2026

Study	Population and duration	Selected sponsor-reported efficacy-estimand result	Evidence status on July 31, 2026
TRANSCEND-T2D-1	537 adults with type 2 diabetes; 40 weeks	A1C change: -1.7, -2.0 and -1.9 percentage points across the three retatrutide arms, versus -0.8 with placebo; weight change up to -16.8%, versus -2.5%	Full Phase 3 report published in The Lancet; registry showed no posted results table when reviewed
TRIUMPH-1	2,339 randomized adults with obesity or overweight and a weight-related condition, without diabetes; 80 weeks	Weight change: -19.0%, -25.9% and -28.3%, versus -2.2% with placebo	Sponsor topline release; full master-trial publication pending when reviewed
TRIUMPH-2	1,152 adults with obesity or overweight and type 2 diabetes; 80 weeks	Weight change: -12.7%, -19.1% and -20.8%, versus -4.0%; A1C change up to -1.6 points, versus -0.2	Sponsor topline release; full peer-reviewed report pending when reviewed
TRIUMPH-3	1,949 adults with BMI at least 35 and established cardiovascular disease, with or without type 2 diabetes; 80 weeks	Weight change: -21.6% and -22.6%, versus -3.2%	Sponsor topline release; cardiovascular analyses not definitive
TRIUMPH-4	445 adults with obesity or overweight and knee osteoarthritis, without diabetes; 68 weeks	Weight change: -26.4% and -28.7%, versus -2.1%; WOMAC pain change -4.5 and -4.4 points, versus -2.4	Sponsor topline release from December 2025; full peer-reviewed report pending when reviewed

The dose labels are omitted from this overview because the table is a results comparison, not a dosing guide. The linked study reports identify each randomized arm and protocol.

TRANSCEND-T2D-1: glycemic control and weight at 40 weeks

TRANSCEND-T2D-1 randomized 537 adults with type 2 diabetes and inadequate glycemic control with diet and exercise to three retatrutide arms or placebo. The primary endpoint was change in A1C at 40 weeks.

In the sponsor's efficacy-estimand analysis, average A1C changed by -1.7, -2.0 and -1.9 percentage points in the retatrutide arms, compared with -0.8 with placebo. Average body weight changed by -11.5%, -15.5% and -16.8%, compared with -2.5% with placebo.

The peer-reviewed paper's treatment-regimen estimates for body weight were -11.5%, -13.9% and -15.3%, compared with -2.6% for placebo. This difference from the topline efficacy numbers is not a contradiction; the analyses answer different questions about what happens after discontinuation or other intercurrent events.

TRANSCEND-T2D-1 is especially important for evidence quality because a journal article allows readers to examine more of the methods, statistical plan, outcome definitions and safety data than a press release can provide. It still represents a 40-week study in a defined population, not proof of long-term outcomes in every potential population.

TRIUMPH-1: the largest reported obesity percentage

TRIUMPH-1 evaluated adults with obesity or overweight and at least one weight-related condition who did not have diabetes. At 80 weeks, the sponsor reported average weight changes of -19.0%, -25.9% and -28.3% in the three retatrutide arms, compared with -2.2% for placebo under the efficacy estimand. In the highest arm, 45.3% of participants reached at least 30% weight loss.

A prespecified extension followed 532 participants who had started with a BMI of at least 35, completed the 80-week main study, and tolerated their assigned treatment. At 104 weeks, the sponsor reported an average change of -30.3% in the 12 mg arm. That figure applies to the extension subgroup, not the entire original TRIUMPH-1 population, and should not replace the 80-week primary analysis in a general summary.

TRIUMPH-1 also included nested studies of knee osteoarthritis pain and moderate-to-severe obstructive sleep apnea. Those findings broaden the program, but they do not turn the trial into evidence for every obesity-related condition.

TRIUMPH-2: obesity with type 2 diabetes

TRIUMPH-2 enrolled 1,152 adults with obesity or overweight and type 2 diabetes. At 80 weeks, efficacy-estimand average weight changes were -12.7%, -19.1% and -20.8% for the three retatrutide arms, compared with -4.0% for placebo. Average A1C changed by -1.4, -1.6 and -1.5 percentage points, compared with -0.2 for placebo.

The result should be read within its population. Weight-loss percentages in people with type 2 diabetes cannot be compared directly with TRIUMPH-1's results in participants without diabetes because the populations, baseline characteristics and clinical context differ.

TRIUMPH-3: severe obesity and established cardiovascular disease

TRIUMPH-3 enrolled 1,949 adults with a BMI of at least 35 and established cardiovascular disease, with or without type 2 diabetes. At 80 weeks, average weight changed by -21.6% and -22.6% in the two retatrutide arms and by -3.2% with placebo under the efficacy estimand.

Lilly also reported exploratory cardiovascular-event analyses. The prespecified in-study hazard ratio for a five-component major adverse cardiovascular event composite was 0.82, with a 95% confidence interval of 0.55 to 1.22. For the conventional three-component composite of cardiovascular death, heart attack or stroke, the hazard ratio was 1.12, with a 95% confidence interval of 0.64 to 1.96.

Both confidence intervals include 1.0, and Lilly said fewer events occurred than anticipated. The findings therefore do not establish that retatrutide reduces cardiovascular events. The separate, event-driven TRIUMPH-Outcomes trial is designed to answer cardiovascular and kidney outcome questions and is estimated to continue until 2029.

TRIUMPH-4: important context from late 2025

TRIUMPH-4 enrolled 445 adults with obesity or overweight and knee osteoarthritis who did not have diabetes. At 68 weeks, the sponsor's efficacy-estimand analysis reported average weight changes of -26.4% and -28.7% in the retatrutide arms, compared with -2.1% for placebo.

Average WOMAC pain-subscale scores changed by -4.5 and -4.4 points from a baseline of 6.0, compared with -2.4 points for placebo. The percentage reductions in WOMAC pain publicized by the sponsor were post hoc calculations, and several weight-threshold analyses were not controlled for multiplicity. Those details matter when separating prespecified endpoints from later descriptive analyses.

What the safety reports showed

Across the reported Phase 3 trials, gastrointestinal events such as nausea, diarrhea, constipation and vomiting were among the most common adverse events. Dysesthesia—an altered or unpleasant skin sensation—was also reported more often in several retatrutide arms than with placebo.

The rates varied by trial and randomized arm:

• In TRIUMPH-1, nausea ranged from 28.6% to 42.4% across retatrutide arms, compared with 14.8% on placebo. Discontinuation because of adverse events ranged from 4.1% to 11.3%, compared with 4.9%.
• In TRANSCEND-T2D-1, diarrhea ranged from 18.7% to 26.3%, compared with 4.5% on placebo. Adverse-event discontinuation ranged from 2.2% to 5.1%, compared with 0%.
• In TRIUMPH-2, diarrhea ranged from 27.4% to 33.6%, compared with 13.2% on placebo. Adverse-event discontinuation ranged from 3.8% to 11.6%, compared with 4.9%.
• In TRIUMPH-3, diarrhea occurred in 30.1% and 24.4% of the two retatrutide arms, compared with 8.7% on placebo. Adverse-event discontinuation was 9.8% and 13.5%, compared with 4.8%.
• In TRIUMPH-4, nausea occurred in 38.1% and 43.2% of the retatrutide arms, compared with 10.7% on placebo. Adverse-event discontinuation was 12.2% and 18.2%, compared with 4.0%.

This is not a complete safety assessment. Press releases cannot substitute for full adverse-event tables, adjudication details, subgroup analyses, laboratory trends, and longer follow-up. Positive efficacy findings also do not by themselves establish a favorable benefit-risk balance; that is part of the regulator's review of the complete application.

What the results do not establish

The trials do not establish FDA approval

Phase 3 success and FDA approval are separate events. A sponsor can report that a trial met its primary endpoint before it submits an application. FDA then decides whether to accept the application for review and whether the total evidence supports approval for a specific indication, population, formulation and labeling.

The trials do not validate third-party research products

The results concern Lilly's investigational product manufactured, controlled and administered within defined clinical-trial protocols. They do not establish the identity, purity, strength, sterility, stability, safety or clinical performance of a vial sold by a third-party research supplier.

A supplier's chromatogram or mass spectrum may answer analytical questions about its own batch. It does not establish equivalence to the investigational drug used in a sponsor's clinical program. The Journal's guide to HPLC purity and LC-MS identity testing explains why those methods answer narrower quality questions.

The same boundary applies to combination claims. Retatrutide's single-agent trials do not provide evidence for adding MOTS-c or another research peptide. A supplier's labels or marketing cannot bridge that evidence gap; the Journal's research supplier checklist explains how to separate vendor claims from batch documentation.

The trials do not provide personal-use instructions

Protocol arm labels describe what investigators studied. They are not an approved dose, self-administration schedule or recommendation. This article does not provide preparation, reconstitution, titration, administration or personal-use guidance.

Is retatrutide FDA approved?

No. As of July 31, 2026, retatrutide is not FDA approved for obesity, type 2 diabetes, knee osteoarthritis, sleep apnea or any other condition.

FDA's current page on unapproved GLP-1 drugs states that retatrutide is not a component of an FDA-approved drug and has not been found safe and effective for any condition. The agency also states that retatrutide cannot be used in compounding under federal law.

This status should not be confused with the existence of Phase 3 trials. Investigational drugs can be studied in authorized clinical trials before approval. Nor should a “research use only” label be treated as a way to sell an unapproved human drug. FDA says it has warned companies that used research disclaimers while selling retatrutide directly to consumers for human use with dosing instructions.

For a research-peptide website, the defensible line is precise:

• discussion of the molecule, published science and clinical-trial record is legitimate scientific reporting;
• a laboratory research reagent is not the FDA-reviewed investigational product used in Lilly's trials;
• trial results should not be used to market a research vial for human treatment; and
• a disclaimer does not control if the surrounding claims and conduct show an intended human-drug use.

When will retatrutide be available?

There is no confirmed U.S. availability date.

On July 23, 2026, Lilly stated that it planned to submit a Biologics License Application for retatrutide to FDA in the first quarter of 2027. That is a sponsor forecast for filing, not a regulatory decision. Before an FDA-approved product could become available, several separate events would have to occur:

1. Lilly would need to complete and submit the application.
2. FDA would decide whether the application is sufficiently complete to file for review.
3. FDA would evaluate efficacy, safety, manufacturing controls, labeling and the overall benefit-risk profile.
4. The agency could approve the application, issue a complete response requesting additional work, or take another regulatory action.
5. If approval occurred, the company would separately determine its launch and supply timing.

An exact 2027 launch forecast is therefore premature. Standard review clocks also should not be converted into a promised approval date: filing acceptance, review designation, inspection findings, manufacturing questions and requests for additional information can all affect the timeline.

Several studies continue beyond the current regulatory package. ClinicalTrials.gov lists TRIUMPH-Outcomes as an approximately 10,000-participant, event-driven trial that was active, not recruiting, with estimated completion in February 2029. Other TRANSCEND and TRIUMPH studies examine additional populations and comparisons. Approval for one indication, if it occurs, would not automatically approve every condition under study.

Retatrutide Phase 3 and FDA status FAQs

What were the headline retatrutide Phase 3 results?

Through July 31, 2026, Lilly had reported positive results from five Phase 3 studies. The largest sponsor-reported efficacy-estimand average weight change was -28.7% at 68 weeks in TRIUMPH-4 and -28.3% at 80 weeks in the main TRIUMPH-1 trial. TRANSCEND-T2D-1 reported A1C reductions of up to 2.0 percentage points at 40 weeks. These figures came from different populations and cannot be treated as head-to-head comparisons.

Are all the 2026 results peer reviewed?

No. TRANSCEND-T2D-1 has a peer-reviewed Phase 3 publication in The Lancet. The major TRIUMPH findings discussed here were still primarily sponsor-reported topline data when this review was completed.

Is retatrutide FDA approved?

No. FDA states that retatrutide is not a component of an approved drug and has not been found safe and effective for any condition.

Can a compounding pharmacy make retatrutide?

FDA states that retatrutide cannot be used in compounding under federal law. A product described online as “compounded retatrutide” should not be treated as an FDA-approved alternative.

When will retatrutide be available in the United States?

No date has been confirmed. Lilly says it plans to submit an application in the first quarter of 2027. Submission, FDA review, approval and commercial launch are separate events.

Do the trial results apply to retatrutide sold by research-peptide companies?

No. The trials evaluated Lilly's investigational drug under controlled protocols. They do not establish the identity, quality, sterility, safety, equivalence or clinical performance of third-party research products.

Does this article recommend retatrutide for personal use?

No. This is a review of the clinical-development record and regulatory status. It provides no medical, purchasing, preparation, dosing, titration or administration guidance.

The bottom line

Retatrutide's Phase 3 program reached a consequential point in 2026. One diabetes trial now has a peer-reviewed publication, and sponsor-reported obesity trials produced large average weight changes across several defined populations. The results also show why careful reading matters: efficacy and treatment-regimen estimands differ, extension subgroups should not be generalized to whole trials, and exploratory cardiovascular analyses are not outcome proof.

The regulatory conclusion is simpler. Retatrutide is not FDA approved, cannot be used in compounding under federal law, and has no confirmed U.S. availability date. Lilly's planned first-quarter 2027 filing begins another stage of review; it does not predetermine the result or the launch timeline.

References

• Eli Lilly and Company, TRANSCEND-T2D-1 Phase 3 Topline Results (March 19, 2026).
• Bajaj HS, Frías JP, Lingvay I, et al., Efficacy and Safety of Retatrutide in People With Type 2 Diabetes: TRANSCEND-T2D-1, The Lancet (2026), doi:10.1016/S0140-6736(26)00967-0.
• ClinicalTrials.gov, TRANSCEND-T2D-1, NCT06354660.
• Eli Lilly and Company, TRIUMPH-1 Phase 3 Topline Results (May 21, 2026).
• ClinicalTrials.gov, TRIUMPH-1, NCT05929066.
• Eli Lilly and Company, Additional TRIUMPH-1 and TRANSCEND-T2D-1 Results (June 6, 2026).
• Eli Lilly and Company, TRIUMPH-2 and TRIUMPH-3 Phase 3 Topline Results (July 23, 2026).
• ClinicalTrials.gov, TRIUMPH-2, NCT05929079.
• ClinicalTrials.gov, TRIUMPH-3, NCT05882045.
• Eli Lilly and Company, TRIUMPH-4 Phase 3 Topline Results (December 11, 2025).
• ClinicalTrials.gov, TRIUMPH-4, NCT05931367.
• ClinicalTrials.gov, TRIUMPH-Outcomes, NCT06383390.
• U.S. Food and Drug Administration, FDA's Concerns With Unapproved GLP-1 Drugs Used for Weight Loss.

NuLab products are intended strictly for laboratory research use only and are not for human or animal consumption. This article reviews public clinical-trial and regulatory records. It does not provide medical, purchasing, preparation, dosing, titration, administration or personal-use guidance. A third-party research product should not be represented as the investigational drug used in Lilly's clinical trials.