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Lilly has reported topline Phase 3 results from TRIUMPH-1, a late-stage trial of retatrutide in adults with obesity or overweight and at least one weight-related comorbidity, without diabetes.

Retatrutide is an investigational once-weekly triple hormone receptor agonist. It targets GIP, GLP-1 and glucagon receptors. It is not approved for public use.

Headline results at 80 weeks

Average percentage body-weight change from baseline:

• Retatrutide 4 mg: -19.0%
• Retatrutide 9 mg: -25.9%
• Retatrutide 12 mg: -28.3%
• Placebo: -2.2%

Average absolute weight change at 80 weeks, from Lilly’s reported baseline average of 112.7 kg / 248.5 lb:

• Retatrutide 4 mg: -21.4 kg / -47.2 lb
• Retatrutide 9 mg: -29.2 kg / -64.4 lb
• Retatrutide 12 mg: -31.9 kg / -70.3 lb
• Placebo: -2.5 kg / -5.5 lb

Weight-loss thresholds at 80 weeks

Lilly also reported the proportion of participants reaching larger weight-loss thresholds:

At least 25% body-weight reduction:

• 4 mg: 27.8%
• 9 mg: 52.9%
• 12 mg: 62.5%
• placebo: 2.2%

At least 30% body-weight reduction:

• 4 mg: 15.3%
• 9 mg: 37.9%
• 12 mg: 45.3%
• placebo: 0.5%

At least 35% body-weight reduction:

• 4 mg: 5.9%
• 9 mg: 20.8%
• 12 mg: 27.2%
• placebo: 0.3%

Other reported changes

Lilly reported improvements from baseline in several cardiometabolic markers, including waist circumference, non-HDL cholesterol, triglycerides, systolic blood pressure and high-sensitivity C-reactive protein.

Waist circumference change at 80 weeks, from a baseline average of 118.3 cm / 46.6 in:

• 4 mg: -16.3 cm / -6.4 in
• 9 mg: -21.8 cm / -8.6 in
• 12 mg: -24.1 cm / -9.5 in
• placebo: -3.6 cm / -1.4 in

Extension data

Lilly also reported a pre-specified blinded extension in participants who had baseline BMI ≥35 and completed the main 80-week study while tolerating their assigned dose.

At 104 weeks, average body-weight change in that extension was reported as:

• 4 mg to maximum tolerated dose: -27.9%
• 9 mg to maximum tolerated dose: -29.5%
• 12 mg to maximum tolerated dose: -30.3%
• placebo to retatrutide maximum tolerated dose: -19.2%

For the 12 mg group, that corresponds to an average loss of 38.5 kg / 85.0 lb at 104 weeks, from a reported baseline average of 121.7 kg / 268.3 lb in the extension group.

Safety and tolerability notes

Lilly describes the most common adverse events as gastrointestinal and generally mild-to-moderate. Reuters also reported that dysesthesia, an abnormal skin sensation, occurred in 12.5% of people on the 12 mg dose, and that about 11% of people on the highest dose discontinued because of adverse events.

Important caveats

• These are topline company-reported Phase 3 results.
• The full peer-reviewed paper has not yet been published.
• Trial arms are not dosing instructions.
• Retatrutide remains investigational.
• Retatrutide is not approved by any regulatory agency.
• Lilly says it is legally available only through Lilly clinical trials.
• This is not medical advice, prescribing advice, dosing advice or sourcing discussion.

Sources

Lilly TRIUMPH-1 Phase 3 press release:
https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss

ClinicalTrials.gov listing:
https://clinicaltrials.gov/study/NCT05929066

Lilly retatrutide FAQ:
https://www.lilly.com/news/stories/what-to-know-about-retatrutide

Reuters coverage:
https://www.reuters.com/business/healthcare-pharmaceuticals/patients-lillys-next-gen-obesity-drug-lost-28-body-weight-company-says-2026-05-21/

Please keep comments evidence-led. No sourcing, vendors, sales, dosing instructions, grey-market promotion or personal medical advice.