Retatrutide Phase 3 Weight Loss Results: TRIUMPH Data

What Is the TRIUMPH Program?

TRIUMPH is Eli Lilly's phase 3 clinical program for retatrutide, the triple-receptor agonist that targets the GIP, GLP-1, and glucagon pathways at once. The program spans several trials across obesity, type 2 diabetes, cardiovascular outcomes, and osteoarthritis. It builds on the phase 2 trial published by Jastreboff and colleagues in the New England Journal of Medicine in 2023, which enrolled 338 adults over 48 weeks and established the 24.2% benchmark at 12mg that first got the drug noticed.

TRIUMPH-1 is the pivotal obesity trial. It enrolled 2,339 adults with obesity or overweight plus at least one weight-related comorbidity, ran longer than phase 2, and used harder responder thresholds. It is the trial designed to support a regulatory filing. TRIUMPH-4, a separate phase 3 study in adults who also had knee osteoarthritis, reported first, in December 2025. For the broader program scope across every TRIUMPH trial, see the TRIUMPH program overview; this page stays focused on the phase 3 efficacy numbers.

How TRIUMPH-1 Differs from Phase 2

The phase 2 trial was a proof-of-concept study: 338 participants, 48 weeks, designed to show the molecule worked. TRIUMPH-1 is a different animal. It enrolled roughly seven times as many people (2,339), ran to an 80-week primary endpoint with a 104-week extension, and measured responder rates at the 25%, 30%, and 35% weight-loss marks rather than just the average. A bigger sample run for longer against tougher endpoints is what turns promising phase 2 data into the kind of evidence a regulator reviews for approval.

Retatrutide Phase 3 Weight Loss Results: The Pivotal TRIUMPH-1 Trial

In TRIUMPH-1 (n=2,339), adults on 12mg retatrutide lost an average of 28.3% of their body weight, about 70.3 lbs, at 80 weeks by the efficacy estimand. The NEJM paper's primary treatment-regimen analysis, which counts everyone randomized, gave 17.6%, 23.7%, and 25.0% at 4, 9, and 12mg versus 3.9% on placebo. This was the general obesity population: adults with a BMI of 30 or higher, or 27 or higher with a weight-related comorbidity, and without type 2 diabetes. The results were dose-dependent across all three active arms.

At 12mg, 45.3% of participants achieved a weight loss of 30% or more, and 65.3% reached a BMI under 30. The 4mg arm is worth a second look: 19.0% over 80 weeks at the lowest tested dose lands close to what the highest tirzepatide dose produced in its own trial, which suggests retatrutide delivers clinically meaningful loss well below the ceiling dose.

TRIUMPH-1 dose-arm weight loss at the 80-week primary endpoint.

The 104-Week Extension: 30.3%

A subset of participants with a baseline BMI of 35 or above continued on 12mg to 104 weeks, roughly two years of treatment. That extension cohort reached an average of 30.3% body weight loss (85.0 lbs / 38.5 kg), among the largest averages recorded in a pharmaceutical obesity trial. Read it carefully, though: the 30.3% number comes from a smaller subgroup limited to BMI 35 and above, not the full trial population. The primary, registration-grade endpoint remains the 80-week result of 28.3%.

What "Average" Actually Means Here

An average of 28.3% (or 19.0% at 4mg) is a population mean. Some participants lost considerably more, others less. Responder rates give a fuller picture of the spread: the fact that 45.3% of the 12mg group hit 30% or more loss tells you how the drug behaved across a range of people, not just at the midpoint. None of this predicts what any single person would lose. To model dose curves and timing for your own scenario, use the retatrutide pharmacokinetics calculator.

TRIUMPH-4 Results: The Earlier Phase 3 Readout

TRIUMPH-4 (NCT05931367) was the first phase 3 trial to report, in December 2025. It enrolled 445 adults with obesity or overweight (BMI 27 or higher) who also had moderate-to-severe knee osteoarthritis, a notable difference from the general-obesity TRIUMPH-1 population. On 12mg at 68 weeks, participants lost an average of 28.7% of body weight (71.2 lbs / 32 kg) versus 2.1% on placebo. The trial also carried a co-primary endpoint measuring knee pain relief, which sits outside the scope of this efficacy page; the TRIUMPH program overview covers that in full.

Why TRIUMPH-4 and TRIUMPH-1 Differ

The two trials studied different people for different lengths of time. TRIUMPH-4 ran 68 weeks in 445 adults with knee osteoarthritis; TRIUMPH-1 ran 80 weeks in 2,339 adults in the general obesity population. The longer treatment window in TRIUMPH-1 accounts for part of the difference in the high-dose arms. The cleaner way to read the program: TRIUMPH-4 was the first phase 3 signal, and TRIUMPH-1 is the larger, pivotal confirmation that a filing would rest on.

How Phase 3 Results Compare to Phase 2

Putting the readouts on one line shows a clear trajectory. Phase 2 (Jastreboff, NEJM 2023): 24.2% at 48 weeks on 12mg. TRIUMPH-4: 28.7% at 68 weeks on 12mg. TRIUMPH-1: 28.3% at 80 weeks on 12mg as the primary endpoint, then 30.3% at 104 weeks in the BMI 35-plus extension. The pattern confirms what the phase 2 curve hinted at, that weight loss kept going well past the 48-week mark and had not flattened by 80 weeks at the top dose. Longer treatment, in this drug, kept moving the number.

Retatrutide efficacy across phase 2 and the TRIUMPH phase 3 trials, by trial duration.

How Retatrutide Phase 3 Weight Loss Results Compare to Other GLP Drugs

For context, here is how the retatrutide readouts sit next to the pivotal phase 3 trials of two approved GLP-1 class drugs. The numbers come from separate trials, so treat the comparison as illustrative.

For deeper analysis, see retatrutide vs tirzepatide and retatrutide vs semaglutide. The mechanism behind these high numbers is covered in how retatrutide's triple agonist mechanism works.

Phase 3 Safety Profile: What the TRIUMPH Data Shows

Efficacy is only half the readout. The TRIUMPH-1 safety data followed the familiar pattern for this drug class: mostly gastrointestinal, mostly dose-dependent, and most common during titration. The figures below are from TRIUMPH-1 (Jastreboff et al., NEJM, 29 Sep 2026), by dose arm in adults with obesity or overweight without type 2 diabetes.

• Nausea: 28.6% at 4mg, 38.4% at 9mg, 42.4% at 12mg, versus 14.8% on placebo.
• Diarrhea: 25.2% at 4mg, 34.1% at 9mg, 32.0% at 12mg, versus 13.5% on placebo.
• Constipation: 23.8% at 4mg, 25.9% at 9mg, 26.1% at 12mg, versus 10.9% on placebo.
• Vomiting: 10.6% at 4mg, 22.8% at 9mg, 25.3% at 12mg, versus 4.8% on placebo.
• Gastrointestinal effects: the most common adverse events were nausea, diarrhea, constipation, then vomiting (constipation exceeded vomiting at every dose), as with the rest of this drug class, and each was more frequent at 9mg and 12mg than at 4mg.
• Dysesthesia (TRIUMPH-1, general obesity): 5.1% to 12.5% across arms, versus 0.9% on placebo.
• Discontinuation due to adverse events: 4.1% at 4mg, 6.5% at 9mg, 11.2% at 12mg, versus 4.6% on placebo.

Two points need care. First, dysesthesia (an abnormal skin or touch sensation) was reported at 5.1% to 12.5% in TRIUMPH-1, the general obesity population. A separate, higher figure of 20.9% at 12mg (8.8% at 9mg, versus 0.7% on placebo) comes from TRIUMPH-4, adults with obesity or overweight and knee osteoarthritis, and applies only to that trial. These are two different trials in two different groups of people, so do not treat the numbers as interchangeable. Second, the discontinuation rate due to adverse events rose with dose, from 4.1% at 4mg to 11.2% at 12mg; that is a data point relevant to dose selection, not a verdict on the drug. For the fuller side-effect picture and management, see retatrutide side effects.

Most Common Side Effects by Dose

The gastrointestinal effects above mostly scaled with dose: the 4mg arm had the lowest rate of each, and the 12mg arm had the highest rate of nausea, constipation, and vomiting. Diarrhea was the exception, peaking at 9mg (34.1%) rather than 12mg (32.0%). More weight loss came with a heavier side-effect load, which is why titration steps up gradually rather than starting at the top dose.

Retatrutide FDA Approval Status and Timeline

Retatrutide is not FDA-approved as of June 1, 2026. The TRIUMPH-1 results from May 2026 are the pivotal efficacy data Lilly needs to support a Biologics License Application (BLA). Lilly plans to submit a Biologics License Application (BLA) to the FDA in Q1 2027, with approval expected in 2027 or later, depending on how the FDA review proceeds. None of this is a guaranteed date. There is no commercial version of the drug, and in the US, the routes available today are a clinical trial or Lilly's narrow expanded access program (NCT07629401). For the detailed regulatory timeline, see is retatrutide FDA approved.

How to Access Retatrutide Today

Because the drug is investigational, lawful access in the US runs through a clinical trial or Lilly's expanded access program. Enrollment in the TRIUMPH trials has closed: TRIUMPH-1 is completed, and TRIUMPH-5 (versus tirzepatide) and the cardiovascular outcomes trial (NCT06383390) are active but not recruiting. Outside TRIUMPH, a Phase 3 liver-disease (MASLD) master protocol that includes retatrutide, SYNERGY-Outcomes (NCT07165028), was recruiting as of October 2026. Check ClinicalTrials.gov for current retatrutide studies; eligibility criteria and trial sites vary. For the full set of access routes and the caveats around each, see how to get retatrutide.