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Research answer
What did the retatrutide trials find?
As of 23 September 2026, 5 retatrutide trials have reported. In TRIUMPH-1, a phase 3 trial of adults with obesity or overweight without diabetes, mean body weight fell by up to 28.3% over 80 weeks on the highest dose arm, reported by Eli Lilly.
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Updated 23 September 2026
01
Phase 3: the TRIUMPH programme
In TRIUMPH-1, a phase 3 trial of retatrutide in adults with obesity, or overweight with at least one weight-related condition, without diabetes (n=2,339), mean body weight fell 19.0% on 4 mg, 25.9% on 9 mg and 28.3% on 12 mg over 80 weeks, against 2.2% on placebo (efficacy estimand; Eli Lilly topline release, 21 May 2026).
In TRIUMPH-2, a phase 3 trial of retatrutide in adults with type 2 diabetes and obesity or overweight (n=1,152), mean body weight fell 12.7% on 4 mg, 19.1% on 9 mg and 20.8% on 12 mg over 80 weeks, against 4.0% on placebo (efficacy estimand; Eli Lilly topline release, 23 July 2026).
In TRIUMPH-3, a phase 3 trial of retatrutide in adults with severe obesity (BMI of 35 or more) and established cardiovascular disease, with or without type 2 diabetes (n=1,949), mean body weight fell 21.6% on 9 mg and 22.6% on 12 mg over 80 weeks, against 3.2% on placebo (efficacy estimand; Eli Lilly topline release, 23 July 2026).
In TRIUMPH-4, a phase 3 trial of retatrutide in adults with obesity or overweight and knee osteoarthritis, without diabetes (n=445), mean body weight fell 26.4% on 9 mg and 28.7% on 12 mg over 68 weeks, against 2.1% on placebo (efficacy estimand; Eli Lilly topline release, 11 December 2025).
02
Phase 2
In Retatrutide phase 2 (Jastreboff), a phase 2 trial of retatrutide in adults with a BMI of 30 or more, or 27 to under 30 with at least one weight-related condition (n=338), mean body weight fell 8.7% on 1 mg, 17.1% on 4 mg (pooled), 22.8% on 8 mg (pooled) and 24.2% on 12 mg over 48 weeks, against 2.1% on placebo (Jastreboff AM et al. N Engl J Med 2023;389:514-526).
03
Adverse events and discontinuation
Gastrointestinal events were the most frequent adverse events in both trials that report them by arm. Stopping because of adverse events ranged from 4.1% to 11.3% across the TRIUMPH-1 arms against 4.9% on placebo, and from 12.2% to 18.2% in TRIUMPH-4 against 4.0%.
Every per-event rate, arm by arm, is on the retatrutide side-effects answer and in the adverse events dataset.
Sources
Where every figure comes from
- Eli Lilly topline release, 21 May 2026 · checked 23 September 2026
- Eli Lilly topline release, 23 July 2026 · checked 23 September 2026
- Eli Lilly topline release, 23 July 2026 · checked 23 September 2026
- Eli Lilly topline release, 11 December 2025 · checked 23 September 2026
- Jastreboff AM et al. N Engl J Med 2023;389:514-526 · checked 23 September 2026
Last reviewed 23 September 2026