Retatrutide TRIUMPH-1 Results (May 2026): 30.3% Weight Loss, Phase 3 Primary Trial

Updated July 10, 2026: Added biologic classification lawsuit context (Lilly v. FDA, Case 1:24-cv-01503). See below for what this means for compounders. ADA 86th Scientific Sessions (June 2026) complete: Eli Lilly's TRIUMPH-1 Phase 3 trial, the primary obesity study for retatrutide, has reported results. Across 2,339 adults with obesity, the 12mg dose delivered 28.3% average weight loss at 80 weeks (~70.3 lbs); the 9mg dose delivered 25.9%. In a study extension for BMI ≥35 participants, the 12mg dose reached 30.3% average weight loss at 104 weeks (~85 lbs), the highest sustained weight loss ever recorded in a Phase 3 obesity trial, and the first time any drug has crossed 30% in a pivotal trial. Most striking: 65.3% of participants on the 12mg dose reduced their BMI below 30 by week 80, meaning nearly two-thirds crossed the clinical obesity threshold on a drug alone. ADA 2026 comorbidity data (June 2026): TRIUMPH-4 revealed that retatrutide 9mg reduced WOMAC knee pain scores by ~4.0 points (≈75% improvement from baseline) vs 2.1 points for placebo, and 14.1% of patients on 9mg achieved complete pain relief vs 4.2% on placebo. A secondary analysis of TRIUMPH-1 showed 60.6% reduction in apnea-hypopnea index (AHI), from 58.6 to approximately 23 events per hour, in participants with moderate-to-severe obstructive sleep apnea. Additionally, retatrutide completed its first Phase 3 type 2 diabetes trial (TRANSCEND-T2D-1, 537 patients): A1C fell 1.7-2.0% and weight fell 11.5-16.8% at 40 weeks. Retatrutide is the first triple-agonist: it simultaneously activates GLP-1, GIP, AND glucagon (GCGR) receptors. FDA approval is expected late 2027 to early 2028, retatrutide is NOT available to prescribe today.

Quick answer: what's available right now while you wait for retatrutide:

• •Highest approved-treatment trial result in this list: Zepbound produced up to 20.9% in SURMOUNT-1; LillyDirect starts at $299/mo. Enhance MD from $99 first month is a compounded tirzepatide route, but that branded trial result does not establish outcomes for its product
• •Lowest-cost featured GLP-1: Yucca Health $146/mo, 6-month plan compounded semaglutide
• •Brand Wegovy: NovoCare lists the pen at $199/mo for the first two low-dose fills, then $349/mo at standard strengths ($399 HD), and the pill from $149/mo, prescription required and dose-dependent (checked August 14, 2026). Hers lists the pill medication from $149 and pen from $199 plus required membership ($39 first month, $149/mo ongoing), making its lowest all-in path $188 initially and $298/mo ongoing.
• •Pill (no injection): Foundayo from $149/mo, 12.4% loss
• •Full pipeline: Next weight loss drugs guide covers retatrutide, CagriSema, MariTide, survodutide.

This guide covers retatrutide's mechanism, Phase 3 trial results, side effect profile, expected pricing, and approval timeline, based on Eli Lilly's TRIUMPH clinical program data. Compare all currently-approved GLP-1 providers or take the match quiz to find an option available today.

How Does Retatrutide Work in the Body?

Current GLP-1 medications work by activating one or two hormone receptors. Retatrutide is a first-in-class triple agonist that simultaneously activates three:

The glucagon receptor activation is the key differentiator. Glucagon increases your resting energy expenditure and promotes fat oxidation, essentially, your body burns more fat even at rest. This third mechanism may explain why retatrutide's weight loss numbers exceed anything seen before in clinical trials.

How Much Weight Does Retatrutide Help You Lose?

Retatrutide has been studied in both Phase 2 and Phase 3 trials. The results are striking.

The Phase 2 trial (published in the New England Journal of Medicine, June 2023) enrolled 338 adults with obesity or overweight and tested multiple doses over 48 weeks:

At the 12mg dose, the responder rates were remarkable: 100% of participants achieved at least 5% weight loss, 93% achieved 10%+, 83% achieved 15%+, and 26% lost more than 30% of their body weight.

Then in December 2025, Eli Lilly reported the first Phase 3 results from TRIUMPH-4 (445 participants with obesity and knee osteoarthritis, 68 weeks):

Then on May 21, 2026, Eli Lilly reported results from TRIUMPH-1, the primary Phase 3 obesity trial and the dataset that will anchor the NDA submission. With 2,339 participants over 80 weeks, TRIUMPH-1 is the definitive efficacy record:

How Does Retatrutide Compare to Current GLP-1s?

Retatrutide leads on weight loss at ~28-30% in obesity, versus ~22-26% for tirzepatide and ~15-17% for semaglutide. It is also the only one of the three not yet FDA approved: Phase 3 is complete with an NDA expected Q4 2026, and none of these figures come from head-to-head trials.

Early body composition data suggests retatrutide may also have favorable effects on fat vs. muscle loss. In available analyses, fat mass accounted for approximately 67% of total weight lost with retatrutide, compared to about 61% with semaglutide. Tirzepatide showed the best fat-to-lean ratio at roughly 75% fat loss. These are preliminary comparisons across different trials, not head-to-head data.

Side Effects: What the Trials Show

The side effect profile is similar to existing GLP-1s, with one notable new signal:

Discontinuation rates in TRIUMPH-1 were 11.3% at 12mg, 6.9% at 9mg, and 4.1% at 4mg, versus 4.9% for placebo, lower than TRIUMPH-4's 18.2% at 12mg, likely reflecting the longer titration schedule in TRIUMPH-1 improving tolerability. Most GI side effects were mild to moderate and improved during dose escalation. Retatrutide did not increase serious adverse events versus placebo.

When Will Retatrutide Be FDA-Approved?

• •Current status (June 10, 2026): ADA 86th Scientific Sessions (June 5-8, 2026) complete. Full TRIUMPH-1 and TRANSCEND-T2D-1 datasets presented. Comorbidity highlights: TRIUMPH-4 knee OA, 75% WOMAC pain reduction (9mg), 14.1% pain-free vs 4.2% placebo. TRIUMPH-1 OSA secondary, 60.6% AHI reduction. TRANSCEND-T2D-1 T2D, A1C −2.0%, weight −16.8% at 40 weeks. NOT approved anywhere globally.
• •TRIUMPH-1 Phase 3 complete May 2026, primary obesity trial. TRIUMPH-4 (obesity + osteoarthritis) complete December 2025. TRIUMPH-1 OSA secondary data presented ADA June 2026.
• •NDA submission to FDA: Expected Q4 2026. TRIUMPH-1 completion enables Lilly to finalize the core efficacy data package for filing. Lilly reaffirmed the later-this-year filing plan in reporting picked up by PolitiFact on July 1, 2026, which states plainly that retatrutide 'has not been approved by the Food and Drug Administration.'
• •TRIUMPH-2 is still outstanding. It is a label-broadening dataset rather than a filing gate: TRIUMPH-1 is the trial that anchors the submission, so a TRIUMPH-2 readout after the NDA goes in would expand the indication picture, not delay the file date.
• •Why the not-yet-approved framing keeps mattering: the only person known to have received retatrutide outside a trial got it through the FDA expanded access (compassionate use) pathway, which PolitiFact describes as available to patients with life-threatening disease who cannot access a trial and have no comparable treatment. That is not a route to a prescription, and any site offering retatrutide today is not selling an approved drug.
• •FDA review: Standard review takes 10 months. Priority Review could shorten to 6 months.
• •Potential FDA approval: Late 2027 to early 2028.
• •Commercial launch: Estimated early 2028.

No brand name has been announced yet. Pricing is expected to be in the $1,000-1,500/month range at list price, similar to or slightly above current tirzepatide pricing, given its superior efficacy data.

Expanded Access: What the Registry Record Actually Says (August 2026)

Trade coverage in early August 2026 described Eli Lilly as newly opening early access to retatrutide, with a named set of eligibility criteria. The primary record does not support that framing. Lilly's expanded access record, NCT07629401 on ClinicalTrials.gov, was first posted on June 5, 2026 and last updated the same day, so single-patient pre-approval access has been registered since June rather than opened this month. The registry lists study type EXPANDED_ACCESS, individual patient, overall status AVAILABLE, and a summary reading 'Provide pre-approval single patient expanded access of retatrutide for patients.' Its eligibility section lists no inclusion or exclusion criteria at all, and the only route it gives is the Lilly Answers Center on 1-800-545-5979. We are not repeating the specific criteria reported in trade coverage, because the registry record does not contain them. Expanded access is a physician-initiated request the sponsor and the FDA may decline. It is not a prescription, and retatrutide remains unapproved.

Biologic Classification Lawsuit: What It Means for Compounders (July 2026)

In a move unusual for a drug that hasn't yet been approved, Eli Lilly sued the FDA in 2024 (Case No. 1:24-cv-01503, U.S. District Court, Southern District of Indiana) over a critical regulatory question: should retatrutide be classified as a conventional drug or a biological product? The answer determines whether compounded versions can ever legally exist after approval.

Retatrutide has 41 amino acids. Lilly argued that puts it in the 'analogous to a protein' category under the Public Health Service Act, which would make it a biologic and lock out compounders permanently. The FDA had been using a bright-line rule: greater than 40 amino acids = biologic. On September 30, 2025, Judge Tanya Walton Pratt of the Southern District of Indiana ruled that the FDA's approach was 'arbitrary, capricious, and not in accordance with law,' vacated the drug classification, and remanded to the FDA to establish a proper uniform standard. The court did not mandate a biologic outcome, only that the prior reasoning was legally insufficient.

As of July 2026, the FDA has not issued a new classification decision. Lilly is also appealing portions of the ruling. The outcome will shape whether a compounding market can legally exist after retatrutide's approval. If the FDA reclassifies retatrutide as a biologic, the lower-cost compounding window that characterized semaglutide and tirzepatide would never open for this drug. If it remains a drug, the 503A/503B pathway could activate during any FDA-declared shortage. As it did for tirzepatide beginning in 2023.

What This Means for You

Retatrutide is not available yet, and won't be for at least 18-24 months. If you're considering GLP-1 treatment now, the currently approved options, semaglutide (Wegovy) and tirzepatide (Zepbound), are effective and available today. There's no reason to wait for retatrutide if you qualify for treatment now.

However, if you're already on a GLP-1 and interested in what's next, TRIUMPH-1's completion (May 2026) is the key milestone, Lilly can now compile the primary efficacy dataset for NDA filing. The novel dysesthesia signal (20.9% at 12mg, 8.8% at 9mg) will require explicit patient labeling and likely a structured titration protocol to minimize it. Patients considering the 9mg dose may see a favorable risk-benefit profile: 25.9% weight loss with substantially lower dysesthesia incidence. We'll update this article as the NDA filing and FDA review milestones are announced.

In the meantime, check our provider rankings to find the best GLP-1 program available today, or use our cost calculator to estimate what you'd pay with your insurance.