Retatrutide Clinical Trials: Every Study and What It Found

Six Phase 3 retatrutide clinical trials have reported results, and retatrutide met its main goals in every one. Average weight loss on 12 mg reached 28.7% in TRIUMPH-4 and 28.3% in TRIUMPH-1 (Lilly's efficacy estimand), against about 2% on placebo, and in TRANSCEND-T2D-2, the first Phase 3 head-to-head trial, it was 20.9% against 9.4% on Ozempic 2 mg. As of October 31, 2026, 7 more Lilly Phase 3 trials are running but closed to new volunteers, and 1, a fatty liver study, is still recruiting. A trial, or in rare cases Lilly's expanded access program, is the only legal way to get retatrutide right now, because no approved version exists yet.

As of October 31, 2026, ClinicalTrials.gov lists 33 retatrutide studies: 21 completed, 9 active but not recruiting, 2 recruiting, and Lilly's expanded access program for people who can't get into a trial. By our count from those records, 14 are Phase 3, and Lilly sponsors every one of them. The one recruiting listing that isn't Lilly's is a Phase 2 study in China, covered below.

Retatrutide Phase 3 results so far

Lilly's retatrutide FAQ, updated in October 2026, puts it plainly: "To date, Lilly has disclosed retatrutide Phase 3 data from six clinical trials." All six came out as press releases between December 2025 and October 2026. The chart shows average weight loss on 12 mg in each one, using Lilly's "efficacy estimand", which estimates the result had everyone stayed on the drug as assigned.

The table covers what the chart doesn't: who took part, how long each trial ran, its other main result, and whether a journal has published it.

Add up Lilly's figures for each trial and 7,720 people were randomized across the six; Lilly doesn't state a combined total. Three of the six now have a full peer-reviewed paper. TRANSCEND-T2D-1 came out in The Lancet in June 2026, and on September 29, 2026 TRIUMPH-1 appeared in the New England Journal of Medicine and TRIUMPH-2 in The Lancet. NEJM then published the TRIUMPH-1 and TRIUMPH-2 sleep apnea substudies on October 21. A Europe PMC title search on October 31, 2026 found no paper yet for TRIUMPH-3, TRIUMPH-4 or TRANSCEND-T2D-2, and none of the six has posted results on ClinicalTrials.gov, which is where per-arm side effect tables usually end up.

The journals report a lower headline number because they count differently. NEJM's primary TRIUMPH-1 result counts everyone randomized, whether or not they kept taking the drug (the treatment-regimen estimand): 25.0% on 12 mg against 3.9% on placebo, where Lilly's efficacy figure is 28.3%. The Lancet's TRIUMPH-2 figure on the same basis is 18.8% against 5.1%, where Lilly's is 20.8%.

The spread across trials follows who enrolled and for how long. People with type 2 diabetes lost less at every dose, and the three lowest 12 mg averages (16.8%, 20.8% and 20.9%) all come from diabetes trials. TRANSCEND-T2D-1 lasted only 40 weeks, and TRIUMPH-3 took people with established heart or blood vessel disease. Dose-by-dose weight loss, side effects and dropout rates for each trial are on the retatrutide Phase 3 results page, and the retatrutide weight loss results page turns them into pounds and timelines.

Retatrutide vs Ozempic, the first Phase 3 head-to-head trial

TRANSCEND-T2D-2 is the first Phase 3 trial to put retatrutide against another incretin drug, and Lilly released the topline on October 28, 2026. It randomized 1,298 adults with type 2 diabetes on metformin, with or without an SGLT2 inhibitor, 2:2:1 to retatrutide 9 mg, retatrutide 12 mg or Ozempic 2 mg, Ozempic's highest approved dose, for 80 weeks. It was open label, so everyone knew what they were taking.

From a starting A1C of 8.3%, A1C fell 2.2 points on both retatrutide doses against 1.8 on Ozempic. Weight fell 19.5% on 9 mg and 20.9% (47.4 lb) on 12 mg, against 9.4% on Ozempic, from an average start of 102.4 kg (225.8 lb).

Two limits come with those numbers. Every figure in the release is Lilly's efficacy estimand, with no everyone-randomized figures yet. And the 9 mg advantage over Ozempic on A1C and systolic blood pressure is nominal only, meaning it wasn't protected against the extra chance of a fluke that comes from testing many comparisons; the 12 mg comparisons were. Stomach side effects looked a lot like Ozempic's: diarrhea ran 28.3% and 32.7% against 26.4%, and constipation was less common on retatrutide (14.2% and 13.1% against 19.8%). More people stopped retatrutide because of side effects, though: 4.8% on 9 mg and 7.9% on 12 mg, against 2.7% on Ozempic. The retatrutide diarrhea page lines these rates up with the placebo trials.

The trial isn't over. About 650 people carry on with retatrutide for 24 more weeks, with study completion estimated for February 2027, and Lilly says the full results will come at a medical meeting and in a journal, with no dates given. For how tirzepatide's diabetes brand stacks up against TRANSCEND-T2D-1, see retatrutide vs Mounjaro.

The Phase 2 trials that came first

In the 48-week Phase 2 obesity trial of 338 adults, published in the New England Journal of Medicine in June 2023, people on 12 mg lost an average of 24.2% of their weight, against 2.1% on placebo. The same paper found that starting at 2 mg instead of 4 mg partly eased the stomach side effects, and all six Phase 3 trials started everyone at 2 mg.

A companion trial in type 2 diabetes, published in The Lancet, randomized 281 people to retatrutide, dulaglutide or placebo for 36 weeks, and A1C fell 2.02% on 12 mg at week 24. A liver substudy in Nature Medicine followed 98 people with fatty liver: on 12 mg, their liver fat fell by 86.0% (relative to where it started) at 48 weeks, though fewer than half the group had a week-48 scan. A third Lilly Phase 2 study, in 146 people with chronic kidney disease, finished in October 2025 and hasn't posted results. The retatrutide Phase 2 page covers all of them.

TRIUMPH-4 and knee pain

TRIUMPH-4 came first, in December 2025, and it's the one built around knee pain. All 445 people had knee osteoarthritis, and pain was a main endpoint alongside weight. On a 0 to 10 pain scale (WOMAC) where they started at 6.0, pain fell 4.5 points on 9 mg and 4.4 on 12 mg over 68 weeks, against 2.4 on placebo.

It also had the highest side effect dropout of any Phase 3 trial so far: 18.2% of people on 12 mg stopped because of adverse events, against 4.0% on placebo. Lilly tied it to starting weight: among people who began with a BMI of 35 or more, 12.1% on 12 mg stopped for adverse events. Some people quit because they felt they were losing too much. The TRIUMPH-4 page has the rest.

Retatrutide clinical trials still running, and when they finish

These are the 8 Phase 3 retatrutide trials that haven't reported, with the dates registered on ClinicalTrials.gov as of October 31, 2026. "Primary completion" is when the last participant has the main measurement taken. Results come later.

For the first five trials that reported, the gap between primary completion and Lilly's announcement ran from 27 to 98 days, by our arithmetic from the registry and release dates. TRANSCEND-T2D-2 fit the pattern: it reached primary completion on August 27, 2026, and the topline came 62 days later.

Our read: at that pace, TRIUMPH-5 against tirzepatide would report between late November 2026 and early March 2027, and TRANSCEND-T2D-3, if its October estimate held, between about November 2026 and early February 2027. Registry estimates slip, so treat both as windows, not dates.

How long has retatrutide been in trials?

Since 2019. The first single-dose safety study in healthy volunteers (NCT03841630) finished in July 2019, so retatrutide has been in human trials for more than 7 years. A 12-week Phase 1b study in type 2 diabetes, published in 2022, measured a half-life of about 6 days, which is why it's a once-weekly shot. Phase 2 results followed in June 2023, the TRIUMPH program began in 2023 and TRANSCEND-T2D followed in 2024.

Lilly's second-quarter 2026 results, filed with the SEC, say the clinical data package for obesity, sleep apnea and knee osteoarthritis pain is complete. Lilly last said, on September 29, 2026, that it plans to submit retatrutide to the FDA in the first quarter of 2027 as a Biologics License Application (BLA). On October 2, 2026, the FDA decided that retatrutide is a drug, not a biological product, so an application would need to be filed under section 505 of the Federal Food, Drug, and Cosmetic Act. Lilly's appeal on that question is pending in the Seventh Circuit, and we found no ruling as of October 31, 2026.

Filing isn't approval, and Lilly's own explainer gives no launch date. Retatrutide will stay in clinical trials whatever the FDA decides: the heart and liver outcome studies have estimated primary completion dates in 2029 and 2030. The retatrutide FDA approval page follows the court case and the review rules, and the retatrutide release date page tracks the steps between here and a pharmacy shelf.

Can you still join a retatrutide trial?

Not an obesity trial, for now. On October 31, 2026, every TRIUMPH and TRANSCEND study on ClinicalTrials.gov is either completed or active but not recruiting. Two retatrutide listings are recruiting:

• SYNERGY-Outcomes (NCT07165028), Lilly's Phase 3 fatty liver study. It takes adults with liver fat of 8% or more and a liver stiffness reading of 10 to under 20 kPa on a VCTE scan, runs about 224 weeks, and you might get placebo. It lists 563 sites in 34 countries or territories, 502 of them recruiting and 137 of those in the US. The retatrutide and fatty liver page explains who it's for, and retatrutide near me lists US sites by state.
• NCT07467447, a Phase 2 obesity study sponsored by Hudson Biotech, not Lilly, at 1 site in Shenzhen, China.

SYNERGY-Outcomes also excludes people who lost more than 11 lb in the 3 months before screening, so a recent diet or weight drug can rule you out for a while.

If a trial isn't an option, Lilly runs pre-approval expanded access (NCT07629401) for a narrow group: adults with a BMI of 35 or more despite the highest available dose of a weight management drug, at least 2 serious obesity-related complications, and no trial they can join. Your doctor contacts the Lilly Answers Center; the record asks patients not to call Lilly directly. The how to get retatrutide page goes through each legal route, and retatrutide clinical trials near me shows how to search by location and what to ask a site before screening.

What the trials haven't answered yet

Weight and blood sugar are well covered, and TRANSCEND-T2D-2 has now put retatrutide against Ozempic in type 2 diabetes, on Lilly's efficacy numbers. These four questions are still open:

• How retatrutide compares with tirzepatide. No head-to-head result exists; TRIUMPH-5 is due to reach primary completion in November 2026. Until then, retatrutide vs tirzepatide can only line up separate trials.
• Whether the weight stays off on a maintenance dose, or after stopping. TRIUMPH-6 moves people after 80 weeks on retatrutide to 1 of 2 doses or placebo, and finishes in April 2028.
• Heart outcomes. In TRIUMPH-3, major heart events were rarer than expected in both arms, far too few to call. TRIUMPH-Outcomes, with about 10,000 people, runs to 2029.
• Rare harms. Lilly's Phase 3 releases give no serious adverse event rate, and neither does the TRIUMPH-1 NEJM abstract. The TRIUMPH-2 paper in The Lancet lists low blood pressure (hypotension) in 5% on 9 mg and 6% on 12 mg, against under 1% on placebo, and 7 deaths across its four arms, all judged unrelated to treatment. The longest follow-up Lilly has reported is 104 weeks, in a TRIUMPH-1 extension. The is retatrutide safe page weighs what's known.

Our read: Lilly already calls its filing package complete, so these gaps won't hold up a submission. They'll matter later, when a doctor and patient weigh retatrutide against tirzepatide, and TRIUMPH-5 is the first of them to finish.

Trial results and vials sold online

Every trial result on this page came from Lilly's own retatrutide, given on a fixed dosing schedule with regular clinic visits. Lilly's October 28, 2026 release says retatrutide "has not been approved by FDA or any regulatory organization anywhere in the world" and that "Anyone purporting to sell retatrutide to consumers is breaking the law." In September 2026, Australia's TGA reported testing a vial sold as retatrutide after a serious adverse event report. It held no retatrutide, but it did hold undeclared semaglutide at about 8 times the level in approved semaglutide products.

If you're looking at retatrutide for sale online, none of these trial results carry over to a vial nobody has tested, and the doses in the tables above were given under trial monitoring. A trial, or an approved drug such as tirzepatide or semaglutide prescribed by your doctor, gets you a product whose contents are known.