TRIUMPH-2: retatrutide in type 2 diabetes and obesity

TRIUMPH-2 tested retatrutide in people who have both type 2 diabetes and obesity or overweight. Lilly announced topline results on 23 July 2026. Weight loss was substantial but smaller than in people without diabetes, which is a familiar pattern for this class of drug. The peer-reviewed paper has not been published.

What the trial did

Participants had type 2 diabetes, had been on stable diabetes treatment for at least three months, had a BMI of 27 or more, and had tried and failed to lose weight by diet at least once. People with type 1 diabetes, a history of pancreatitis, or a personal or family history of medullary thyroid cancer were excluded, as was anyone who had taken weight-loss drugs in the previous 90 days.^[1] Registered as NCT05929079.

Everyone assigned to retatrutide began on a low dose that was stepped up every four weeks until they reached their target of 4 mg, 9 mg or 12 mg, a design shared across the TRIUMPH trials.^[2] Like TRIUMPH-1, it was a basket trial, with a nested group of people with moderate-to-severe sleep apnoea whose results have not yet been reported.^[1] The average starting weight was 106.4 kg and the average BMI 38.2.

Weight loss

Figures at 80 weeks from Lilly's announcement, which reported only the efficacy estimand.^[2] Lilly's definition of that figure is the result "had all randomised participants remained on study intervention", so it is the larger of the two numbers the company normally reports. The treatment-regimen figures, which include people who stopped, will be lower and should appear in the full paper. The difference is explained in how to read a trial.

The 4 mg weight result was a key secondary outcome rather than a primary one.^[2]

Blood sugar

HbA1c is a measure of average blood sugar over the previous two to three months. From a starting average of 7.7%, it fell by 1.4 points on 4 mg, 1.6 on 9 mg and 1.5 on 12 mg, against 0.2 on placebo.^[2] Those are large reductions; a fall of one point is considered clinically meaningful in diabetes care. The 12 mg group did not do better than the 9 mg group on blood sugar, which suggests the glucose effect had reached its ceiling below the top dose. Retatrutide's dedicated diabetes trials, the TRANSCEND programme, are covered on the other indications page.

Why weight loss was smaller than in TRIUMPH-1

In TRIUMPH-1, in people without diabetes, the 12 mg arm lost 28.3% on the same efficacy estimand.^[3] In TRIUMPH-2 it lost 20.8%. That gap is not a surprise. People with type 2 diabetes have consistently lost less weight than people without it on every drug in this class, and Lilly's own announcement describes them as "a population with increased difficulties losing weight".^[2] The reasons are not fully settled; differences in metabolism, in the diabetes medicines people are already taking, and in insulin resistance are all thought to play a part.

The practical point is that a headline retatrutide figure from a trial in people without diabetes should not be applied to someone who has it. The two groups were tested separately for a reason.

Side effects and drop-outs

Diarrhoea, nausea and constipation led, rising with dose. Decreased appetite was reported as an adverse event by 5.8%, 12.3% and 17.1% on the three doses versus 4.5% on placebo, and vomiting by 5.5%, 10.2% and 15.7% versus 4.2%.^[2] Lilly described the events as generally mild to moderate, with most resolving during treatment.

Dysesthesia, the altered skin sensation that is new to retatrutide, affected 4.5%, 5.6% and 7.3% against 0.7% on placebo, a lower rate than in TRIUMPH-1 or TRIUMPH-4.^[2] See the dysesthesia page.

The drop-out pattern was odd: 11.6% of the 9 mg group stopped because of side effects, more than the 7.7% on 12 mg, while the 4 mg rate of 3.8% was below placebo. The announcement does not explain this. With about 288 people per arm, differences of this size can be chance, and the full paper may look different. See discontinuation rates.

No heart-rate, rhythm, liver or pancreas figures were included in the announcement.^[2]

What is still unknown

• The treatment-regimen results, and the full side-effect tables by dose.
• Heart-rate and rhythm data, which matter more in a population with a high rate of heart disease.
• The sleep apnoea sub-group results.
• How the results compare with semaglutide in the same kind of people; that is the head-to-head TRANSCEND-T2D-2 trial, due to complete around August 2026.^[4]