Retatrutide (LY3437943) is a synthetic peptide developed by Eli Lilly that has become one of the most discussed compounds in metabolic research literature. Its defining characteristic is simultaneous activity at three hormone receptors: glucagon-like peptide-1 receptor (GLP-1R), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon receptor (GCGR). This triple agonism distinguishes retatrutide mechanistically from all previously studied single and dual agonists.
GLP-1R activation is the mechanism shared with semaglutide and tirzepatide. It promotes insulin secretion in a glucose-dependent manner, inhibits glucagon release, slows gastric emptying, and activates satiety centers in the CNS.
GIPR activation is shared with tirzepatide. GIP is an incretin hormone released by intestinal K-cells in response to nutrient ingestion. GIPR agonism enhances insulin secretion and has been studied in adipose tissue metabolism contexts. Tirzepatide’s clinical data provided the first large-scale human evidence that dual agonism produces greater metabolic effects than GLP-1R alone.
GCGR agonism is what distinguishes retatrutide from all prior compounds. While glucagon typically raises blood glucose, its receptor also drives hepatic fat oxidation and increases energy expenditure. Researchers have proposed that balanced GCGR agonism combined with GLP-1R and GIPR effects produces a net metabolic benefit exceeding dual agonism.
The landmark published study is a Phase 2 randomized controlled trial by Jastreboff et al., published in the New England Journal of Medicine in 2023. This 48-week trial enrolled adults with obesity and examined multiple retatrutide doses compared to placebo. The highest-dose cohort produced the largest reported body weight reductions of any published GLP-1R agonist or incretin-based trial at 48 weeks. Additional markers including fasting glucose, triglycerides, blood pressure, and waist circumference showed reported improvements in treatment groups compared to placebo.
Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity. N Engl J Med. 2023;389(6):514–526.
At the time of this review, retatrutide is in Phase 3 clinical development and has not received FDA approval. All findings referenced are from published Phase 2 literature. Retatrutide is available through Brava Longevity as a research compound in three formulations — 10mg, 20mg, and 50mg — each third-party tested with full COA documentation available.
For informational purposes only. Not medical advice or treatment guidance.
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