Retatrutide Results in the Clinical Trials

The short version

The headline retatrutide results figure: in the 48-week Phase 2 obesity trial, the highest dose studied produced a mean -24.2% body-weight change in adults with obesity — compared to -2.1% in the placebo group ^[1]. That is the most-cited published number. It comes from a randomized controlled trial in 338 people, published in the New England Journal of Medicine in 2023.

Beyond weight: the same compound at the same dose produced -82.4% relative liver-fat reduction at 24 weeks in a separate substudy of people with fatty liver disease ^[5], and -2.02% HbA1c reduction in a type 2 diabetes trial ^[2]. All three figures are from different patient populations and study designs.

Retatrutide is investigational. These results come from Phase 2 trials. Phase 3 TRIUMPH results are pending.

Phase 2 obesity results: dose by dose (48 weeks)

Trial: Jastreboff AM, et al. N Engl J Med. 2023;389(6):514-526 ^[1]. Participants: 338 adults, BMI ≥30 or ≥27 with comorbidity, no type 2 diabetes. Duration: 48 weeks, once-weekly subcutaneous injection.

Body-weight change at 48 weeks:

• Placebo: -2.1%
• 1 mg: modest effect (dose-response confirmed across arms)
• 4 mg: dose-dependent reduction
• 8 mg: substantial reduction vs placebo
• 12 mg: -24.2% mean body-weight change

Selected secondary outcomes (12 mg arm):

• Waist circumference: significant reduction
• Blood pressure: significant reduction
• Lipids: improved
• Fasting blood glucose: improved

Adverse events at highest dose:

• GI events (nausea, vomiting, diarrhea, constipation): dose-related, mostly mild-to-moderate
• Nausea: up to 45% at 12 mg
• Heart-rate increase: dose-dependent, mean ~5-7 bpm, peaked week 24
• Discontinuation rate at 12 mg: approximately 18%, predominantly GI-related
• Injection-site reactions: approximately 8%

Phase 2 type 2 diabetes results (36 weeks)

Trial: Rosenstock J, et al. Lancet. 2023;402(10401):529-544 ^[2]. Participants: 281 adults with type 2 diabetes (HbA1c 7.0-10.5%). Duration: 36 weeks, once-weekly subcutaneous injection with stepwise escalation to 12 mg.

Glycemic results at 24 weeks:

• HbA1c change, 12 mg: -2.02% vs -0.01% placebo

Weight results at 36 weeks:

• Body weight change, 12 mg: -16.94% vs -3.00% placebo

Safety: GI AEs in 35%; no severe hypoglycemia; no deaths.

MASLD substudy results (24 and 48 weeks)

Trial: Sanyal AJ, et al. Nature Medicine. 2024;30:2037-2048 ^[5]. Participants: 98 adults with obesity/overweight + MASLD (≥10% liver fat by MRI-PDFF), no type 2 diabetes. Duration: 48 weeks.

Liver fat change (relative %) by dose at 24 weeks:

• Placebo: +0.3%
• 1 mg: -42.9%
• 4 mg: -57.0%
• 8 mg: -81.4%
• 12 mg: -82.4%

12 mg at 24 weeks: 86% of participants reached normal liver fat (<5% by MRI-PDFF). 12 mg at 48 weeks: -86.0% relative liver fat reduction.

Phase 3 TRIUMPH status

The TRIUMPH Phase 3 program is Eli Lilly's pivotal program for retatrutide. As of mid-2026, no Phase 3 results have been published. Registered trials include arms studying obesity (TRIUMPH-1/2), type 2 diabetes, cardiovascular outcomes (NCT06383390), chronic kidney disease (TRANSCEND-CKD; NCT05929066), obstructive sleep apnea, and knee osteoarthritis ^[10]. A head-to-head comparison with tirzepatide is also registered.

The TRIUMPH-1 interim or headline number (approximately 28% weight loss) has been referenced in press coverage, but peer-reviewed data are not yet available. This site will update when primary results are published in a peer-reviewed journal.

No Phase 3 results are cited on this site because none have been published.

Meta-analysis summary

A 2025 systematic review and meta-analysis pooled 3 RCTs covering 878 patients ^[8]. Findings:

• Pooled mean weight difference vs placebo: -14.33%
• Adverse-event rate ratio: RR 1.11, P=0.24 (not statistically significant)
• Authors' conclusion: retatrutide shows an appropriate safety profile for an investigational agent, pending long-term outcome data.