Retatrutide TRIUMPH Results: Phase 3 Weight-Loss and Diabetes Data (2026)

Retatrutide just posted the biggest weight-loss numbers of any obesity drug tested so far. In 2026 its large Phase 3 trials — the TRIUMPH programme and the TRANSCEND-T2D diabetes study — finally gave us the proper, regulator-grade data everyone had been waiting years for. Here’s what the trials actually showed, in plain English, with the figures checked against Eli Lilly’s own releases and The Lancet.

Key takeaways

TRIUMPH-1 showed 28.3% mean weight loss at 80 weeks on the 12 mg dose, versus 2.2% on placebo.
45.3% of people on 12 mg lost 30% or more of their body weight — the highest proportion ever reported for a weight-loss medicine.
People with a higher starting BMI who carried on to 104 weeks lost an average of 30.3% (about 85 lb).
TRANSCEND-T2D-1 cut HbA1c by up to 1.94% and body weight by up to 16.8% in type 2 diabetes, published in The Lancet.
Retatrutide still has no MHRA or FDA approval — these are trial results, and in the UK it remains a research compound for laboratory use only.

What retatrutide is (the “triple agonist” bit)

Retatrutide (lab code LY3437943) is what scientists call a triple agonist. That sounds like a wrestling move, but it just means the drug switches on three different hunger-and-metabolism receptors at once — GLP-1, GIP, and glucagon — instead of one or two. Semaglutide (Wegovy) hits one. Tirzepatide (Mounjaro) hits two. Retatrutide goes for the full set, like someone who can’t walk past a buy-one-get-one-free sign.

For years the only data came from a small Phase 2 trial. That changed in 2026, when the big Phase 3 results landed — the kind regulators actually look at. (New to the compound? Start with what retatrutide actually is.)

TRIUMPH-1: the headline obesity trial

TRIUMPH-1 enrolled 2,339 adults with obesity, or overweight plus a weight-related health problem, but no diabetes. They were given retatrutide at 4 mg, 9 mg, or 12 mg, or a placebo (a dummy dose used for comparison), once a week for 80 weeks. Eli Lilly announced the topline results on 21 May 2026.

Dose	Mean weight loss at 80 weeks
4 mg	19.0%
9 mg	25.9%
12 mg	28.3%
Placebo	2.2%

The number that made headlines: 45.3% of people on the 12 mg dose lost 30% or more of their body weight — territory previously seen mostly after weight-loss surgery, and the highest share ever reported for an anti-obesity drug. A jab doing a job once reserved for an operating theatre.

It kept going, too. Participants with a higher baseline BMI who stayed on 12 mg through 104 weeks lost an average of 30.3% of their body weight — around 85 lb.

For rough context, tirzepatide came in around 20–22.5% and semaglutide 2.4 mg around 14.9% in their own Phase 3 obesity trials. Different trials with different people, so it isn’t a perfectly fair race — but the trend is clear. For a plain-English look at the numbers on their own, see our retatrutide weight-loss results guide.

TRANSCEND-T2D-1: retatrutide and type 2 diabetes

A separate trial, TRANSCEND-T2D-1, tested retatrutide in 537 adults who do have type 2 diabetes and whose blood sugar wasn’t controlled by diet and exercise alone. Over 40 weeks it:

cut HbA1c (a marker of average blood sugar over months) by 1.69% to 1.94% across the doses, versus 0.81% on placebo;
cut body weight by 11.5% to 16.8%, versus 2.5% on placebo.

The results were published in The Lancet in June 2026 — the medical world’s equivalent of getting your name in lights.

The wider TRIUMPH programme: knee and sleep apnoea

TRIUMPH isn’t a single trial. It’s a family of Phase 3 studies that began in 2023 and has enrolled more than 5,800 participants, testing retatrutide not just for weight but for the conditions that extra weight causes:

Knee osteoarthritis (TRIUMPH-4). People with obesity and knee OA on 12 mg lost an average of 28.7% of body weight at 68 weeks, and knee-pain scores (WOMAC) dropped by up to 75.8%.
Obstructive sleep apnoea (a substudy within TRIUMPH-1). Among participants with severe sleep apnoea, the apnoea-hypopnoea index fell by 60.6% from a severe baseline — a big improvement in overnight breathing.

If those benefits hold up, retatrutide starts to look less like a weight-loss drug with nice side effects and more like a treatment for the diseases that excess weight drives in the first place.

ADA 2026 and where approval stands

The TRIUMPH-1 and TRANSCEND-T2D-1 data were presented at the American Diabetes Association’s 86th Scientific Sessions on 6 June 2026 — think of it as the World Cup of diabetes research, just with more lanyards and fewer penalty shoot-outs.

Worth saying plainly: retatrutide still doesn’t have MHRA or FDA approval. Phase 3 is the stage before approval, not after it. These are trial results, not a green light to prescribe it. In the UK it remains available only as a research compound for laboratory use — not for human consumption — until a regulator says otherwise. If you need lab-tested retatrutide for research, see our UK retatrutide range, all supplied with a batch-specific Certificate of Analysis.

Frequently asked questions

What did the retatrutide TRIUMPH-1 trial find?

In 2,339 adults with obesity and no diabetes, retatrutide produced mean weight loss of 28.3% at 80 weeks on the 12 mg dose, versus 2.2% on placebo. 45.3% of 12 mg participants lost 30% or more of their body weight, and those with a higher baseline BMI who continued to 104 weeks lost an average of 30.3%.

How does retatrutide compare to Mounjaro and Wegovy?

Retatrutide is a triple agonist (GLP-1, GIP and glucagon), whereas tirzepatide/Mounjaro is a dual agonist and semaglutide/Wegovy is a single GLP-1 agonist. In their respective Phase 3 obesity trials tirzepatide reached roughly 20–22.5% and semaglutide 2.4 mg about 14.9%, compared with retatrutide’s 28.3% at 12 mg — though these are separate trials and not head-to-head.

What did TRANSCEND-T2D-1 show?

In 537 adults with type 2 diabetes, over 40 weeks retatrutide reduced HbA1c by up to 1.94% and body weight by up to 16.8%, versus 0.81% and 2.5% on placebo. The results were published in The Lancet in June 2026.

Is retatrutide approved in the UK?

No. It has no MHRA or FDA marketing authorisation. TRIUMPH and TRANSCEND are Phase 3 trial results, not a regulatory approval. In the UK retatrutide is supplied only as a research compound for laboratory use, not for human consumption.

What is the TRIUMPH programme?

A family of Phase 3 trials that began in 2023 and has enrolled more than 5,800 participants, testing retatrutide for weight management and related conditions including knee osteoarthritis (TRIUMPH-4) and obstructive sleep apnoea (a TRIUMPH-1 substudy), with further results expected.

Final thoughts

The 2026 data is genuinely significant: the largest Phase 3 weight-loss numbers published to date, plus real improvements in blood sugar, knee pain and sleep apnoea. It’s still investigational, and nothing here is medical advice — but for anyone following the science, retatrutide has clearly raised the bar.

For the full breakdown of retatrutide’s published weight-loss data, see our clinical trial results guide. If you’re sourcing retatrutide for research purposes, browse our UK retatrutide range and always check for a batch-specific, third-party Certificate of Analysis confirming ≥99% purity — see our quality testing page for how we verify stock.

This article is for informational and research purposes only and reports published clinical-trial data. Retatrutide is an investigational compound with no MHRA or FDA marketing authorisation, supplied for laboratory research use only and not for human consumption. Nothing here is medical advice.

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Retatrutide TRIUMPH Results: Phase 3 Weight-Loss & Diabetes Data (2026)

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