Retatrutide clinical trials: the TRIUMPH timeline and every result so far

Photograph: editorial illustration for this article. It does not show retatrutide.

Retatrutide trial timeline, 2021 to 2029

Phase 1: proof that one weekly peptide could do three jobs

The first human data came from single- and multiple-ascending-dose studies. The multiple-dose phase 1b trial in 72 people with type 2 diabetes, published in The Lancet in 2022, gave weekly injections for 12 weeks and reported a half-life of about six days, glucose lowering, and weight reduction of up to roughly 9 kg in the highest dose group. Gastrointestinal events were the most common adverse effects^[1].

Phase 2: the results that made retatrutide famous

Obesity (NCT04881760)

Registered as NCT04881760, this trial enrolled 338 adults with a BMI of at least 30, or at least 27 with a weight-related condition, and no diabetes. It started on 20 May 2021 and completed on 22 November 2022^[2]. Participants received placebo or retatrutide at 1, 4, 8 or 12 mg once weekly for 48 weeks. Mean weight change at 48 weeks was −8.7%, −17.1%, −22.8% and −24.2% for the four doses, against −2.1% for placebo^[3].

Type 2 diabetes

A separate 36-week trial in 281 people with type 2 diabetes compared retatrutide with placebo and with dulaglutide 1.5 mg. HbA1c at 24 weeks fell by about two percentage points on 8 mg and 12 mg, against a fall of 1.41 points on dulaglutide and essentially no change on placebo. Weight change at 36 weeks was −16.94% on 12 mg, −3.00% on placebo and −2.02% on dulaglutide^[4]. Our diabetes article has the full breakdown.

The TRIUMPH phase 3 program

Lilly registered the phase 3 program under the name TRIUMPH in mid-2023. Each trial has its own identifier, verified against the ClinicalTrials.gov API on 21 September 2026.

The primary endpoint of TRIUMPH-1, 2 and 3 is percent change in body weight at week 80; TRIUMPH-4 measured weight and the WOMAC knee pain score at week 68; TRIUMPH-Outcomes counts major cardiovascular and kidney events over roughly 248 weeks^{[5][6][7][8][9]}.

What have the phase 3 trials shown?

TRIUMPH-4, announced 11 December 2025

The first phase 3 read-out. In 445 adults with obesity and knee osteoarthritis, the 12 mg dose produced a mean weight change of −28.7% at 68 weeks, about 71 lb, with a reduction in WOMAC knee pain score of 4.0 points on 9 mg and 3.7 points on 12 mg against 2.1 points on placebo^[10].

TRIUMPH-1, announced 21 May 2026

In 2,339 randomised adults without diabetes, mean weight change at 80 weeks from a baseline of 112.7 kg was −19.0% on 4 mg, −25.9% on 9 mg and −28.3% on 12 mg, against −2.2% on placebo. On 12 mg, 62.5% of participants lost at least 25% of their body weight and 45.3% lost at least 30%. In a 532-person extension for people with a BMI of 35 or more, weight change reached −30.3% at 104 weeks on the 12 mg arm. Nausea (42.4% on 12 mg versus 14.8% on placebo), diarrhoea and constipation were the most common adverse events, and 11.3% of the 12 mg group stopped because of adverse events, against 4.9% on placebo^[11].

TRIUMPH-2 and TRIUMPH-3, announced 23 July 2026

In TRIUMPH-2, 1,152 adults with type 2 diabetes lost 12.7% (4 mg), 19.1% (9 mg) and 20.8% (12 mg) of body weight at 80 weeks against 4.0% on placebo, and HbA1c fell by 1.4 to 1.6 percentage points from a baseline of 7.7%. In TRIUMPH-3, 1,949 adults with severe obesity and cardiovascular disease lost 21.6% (9 mg) and 22.6% (12 mg) against 3.2% on placebo. Discontinuation for adverse events ranged from 3.8% to 13.5% across retatrutide arms in the two trials, against about 4.9% on placebo. In the same announcement Lilly said it plans to submit a Biologics License Application to the FDA in the first quarter of 2027^[12].

What is still running?

TRIUMPH-Outcomes (NCT06383390) is the long one: an event-driven trial in roughly 10,000 adults with a BMI of at least 27 and established cardiovascular or kidney disease, measuring time to first major cardiovascular event and a composite kidney endpoint. It started on 30 April 2024, is no longer recruiting, and lists an estimated primary completion of February 2029^[9]. Lilly has also referred to further phase 3 read-outs during 2026, including maintenance dosing studies^[12]. Whether and when any of this becomes an approved product is the subject of retatrutide FDA approval.