Retatrutide Phase 2 Trial: The Triple-Receptor Agonist Cut HbA1c by 2% and Weight by 17% in Type 2 Diabetes
Retatrutide, a triple GIP/GLP-1/glucagon receptor agonist, reduced HbA1c by up to 2.02% and body weight by up to 16.94% in people with type 2 diabetes, outperforming both placebo and the GLP-1 drug dulaglutide.
Quick Facts
What This Study Found
At 24 weeks, retatrutide produced dose-dependent HbA1c reductions:
• 0.5 mg: −0.43%
• 4 mg (escalation): −1.39%
• 4 mg (no escalation): −1.30%
• 8 mg (slow escalation): −1.99%
• 8 mg (fast escalation): −1.88%
• 12 mg (escalation): −2.02%
• Placebo: −0.01%
• Dulaglutide 1.5 mg: −1.41%
At 36 weeks, body weight decreased dose-dependently:
• 0.5 mg: −3.19%
• 4 mg (escalation): −7.92%
• 4 mg (no escalation): −10.37%
• 8 mg (slow): −16.81%
• 8 mg (fast): −16.34%
• 12 mg: −16.94%
• Placebo: −3.00%
• Dulaglutide: −2.02%
The 8 mg and 12 mg doses significantly outperformed both placebo (p<0.0001) and dulaglutide (p<0.0001 for weight; p≤0.0019 for HbA1c).
Key Numbers
How They Did This
This was a randomized, double-blind, double-dummy, placebo-controlled and active comparator-controlled, parallel-group, phase 2 trial conducted at 42 US research centers. 281 adults (age 18-75) with type 2 diabetes (HbA1c 7.0-10.5%, BMI 25-50 kg/m²) were randomized to eight groups receiving weekly injections of placebo, dulaglutide 1.5 mg, or retatrutide at six dose/escalation regimens. Treatment lasted 36 weeks with stratification by baseline HbA1c and BMI. Primary endpoint was HbA1c change at 24 weeks.
Why This Research Matters
This is a landmark trial for the multi-agonist approach to metabolic disease. While tirzepatide (dual GIP/GLP-1 agonist) has already transformed obesity and diabetes treatment, retatrutide adds a third receptor — glucagon — which drives additional energy expenditure and fat burning. The nearly 17% weight loss achieved in type 2 diabetes patients at 36 weeks rivals results seen in dedicated obesity trials, suggesting the triple-agonist approach could become the next major advance in metabolic medicine.
The Bigger Picture
Retatrutide represents the next frontier in incretin-based therapy. Single GLP-1 agonists (semaglutide) produce ~15% weight loss; dual GIP/GLP-1 agonists (tirzepatide) achieve ~21%; and now triple-receptor agonists are pushing boundaries further. The glucagon component adds energy expenditure and liver fat reduction benefits. Published in The Lancet by Eli Lilly, this phase 2 trial directly informed the phase 3 program (TRIUMPH trials), making retatrutide one of the most anticipated metabolic drugs in development.
What This Study Doesn't Tell Us
This was a phase 2 trial with 281 participants — large enough to establish dose-response but not powered for rare safety events. The trial was conducted only in the US with 84% White participants, limiting generalizability. The 36-week duration doesn't capture long-term safety or weight loss plateau effects. The active comparator was dulaglutide (an older GLP-1 agonist), not semaglutide or tirzepatide, making direct comparisons to newer drugs impossible from this trial alone.
Questions This Raises
- ?How will retatrutide compare directly to tirzepatide in head-to-head trials, given their overlapping but different receptor profiles?
- ?Does the glucagon receptor component cause any long-term safety concerns such as liver effects or lean mass loss?
- ?Will the weight loss plateau or continue beyond 36 weeks with ongoing treatment?
Trust & Context
- Key Stat:
- −16.94% body weight at 36 weeks The 12 mg retatrutide dose produced nearly 17% weight loss in type 2 diabetes patients — significantly more than both placebo and dulaglutide
- Evidence Grade:
- This is a well-designed, randomized, double-blind, placebo-controlled and active comparator-controlled phase 2 clinical trial published in The Lancet. It provides strong evidence for dose-response efficacy and safety, though phase 3 data is needed for definitive conclusions about the drug's benefit-risk profile.
- Study Age:
- Published in 2023 in The Lancet, this is a very recent trial. Phase 3 trials (TRIUMPH program) are currently underway, and retatrutide remains one of the most closely watched drugs in the metabolic pipeline.
- Original Title:
- Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.
- Published In:
- Lancet (London, England), 402(10401), 529-544 (2023)
- Authors:
- Rosenstock, Julio(10), Frias, Juan, Jastreboff, Ania M(5), Du, Yu, Lou, Jitong, Gurbuz, Sirel, Thomas, Melissa K, Hartman, Mark L, Haupt, Axel, Milicevic, Zvonko, Coskun, Tamer
- Database ID:
- RPEP-07323
Evidence Hierarchy
Frequently Asked Questions
How is retatrutide different from semaglutide or tirzepatide?
Semaglutide activates one receptor (GLP-1), tirzepatide activates two (GIP and GLP-1), and retatrutide activates three (GIP, GLP-1, and glucagon). The added glucagon receptor increases energy expenditure and fat burning. In this trial, retatrutide achieved nearly 17% weight loss in type 2 diabetes — suggesting the triple approach may offer even greater metabolic benefits.
When will retatrutide be available?
As of this phase 2 trial (2023), retatrutide is in phase 3 clinical trials (the TRIUMPH program) by Eli Lilly. If successful, it could potentially reach the market in the coming years, but FDA approval depends on the phase 3 results and regulatory review timeline.
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Cite This Study
https://rethinkpeptides.com/research/RPEP-07323APA
Rosenstock, Julio; Frias, Juan; Jastreboff, Ania M; Du, Yu; Lou, Jitong; Gurbuz, Sirel; Thomas, Melissa K; Hartman, Mark L; Haupt, Axel; Milicevic, Zvonko; Coskun, Tamer. (2023). Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.. Lancet (London, England), 402(10401), 529-544. https://doi.org/10.1016/S0140-6736(23)01053-X
MLA
Rosenstock, Julio, et al. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.." Lancet (London, 2023. https://doi.org/10.1016/S0140-6736(23)01053-X
RethinkPeptides
RethinkPeptides Research Database. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for..." RPEP-07323. Retrieved from https://rethinkpeptides.com/research/rosenstock-2023-retatrutide-a-gip-glp1
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Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.