A triple agonist targeting GIP, GLP-1, and glucagon receptors — showing up to 24.2% weight loss in Phase II trials.
Retatrutide (LY3437943) is an investigational triple agonist developed by Eli Lilly that simultaneously activates GIP, GLP-1, and glucagon receptors. It represents the next frontier in incretin-based obesity pharmacotherapy. In Phase II trials (TRIUMPH-1), retatrutide demonstrated up to 24.2% mean body weight reduction at 48 weeks — the highest weight loss ever reported for a pharmacological agent in a controlled trial. This surpasses both semaglutide and tirzepatide, establishing retatrutide as a potential best-in-class agent. The addition of glucagon receptor agonism to the dual GIP/GLP-1 mechanism is believed to drive additional energy expenditure through thermogenesis and hepatic glucose regulation, contributing to the superior weight loss outcomes.
* Benefits based on preclinical/animal research unless otherwise noted.
“A triple agonist targeting GIP, GLP-1, and glucagon receptors — showing up to 24.2% weight loss in Phase II trials.”
Retatrutide’s triple receptor mechanism operates through three complementary pathways. GLP-1 receptor activation (shared with semaglutide) provides appetite suppression through hypothalamic circuits, slows gastric emptying, and stimulates glucose-dependent insulin secretion. GIP receptor activation (shared with tirzepatide) enhances the incretin effect, improves insulin sensitivity, and has direct effects on adipose tissue metabolism. The addition of glucagon receptor agonism is the key differentiator: glucagon receptor activation in the liver increases hepatic glucose output (counterbalanced by the insulin-stimulating effects), promotes lipolysis in adipose tissue, and — most importantly — stimulates thermogenesis by activating brown adipose tissue (BAT) and promoting uncoupled mitochondrial respiration. This thermogenic effect increases basal energy expenditure, which combined with the appetite suppression from GLP-1R and GIPR activation, produces the exceptional weight loss observed in trials. Phase III trials (TRIUMPH program) are ongoing.
Protocol Notes: Currently in Phase III clinical trials. Requires physician supervision. Titrate slowly to minimize GI side effects. Not yet commercially available.
Per compounding pharmacy instructions
When sourcing Retatrutide for research purposes, the following quality benchmarks should be verified before use.
Refrigerate (2–8°C). Do not freeze.
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Strong Evidence — Multiple randomized controlled trials with high confidence in efficacy and safety data.
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