Retatrutide

Retatrutide (LY3437943; development code also referenced as GIP/GLP-1/Glucagon triple agonist) is a synthetic acylated peptide developed by Eli Lilly and Company currently in Phase 3 clinical development. It acts as a simultaneous agonist at three receptors: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GCGR) — a combination that makes it the first triple GI hormone-receptor agonist to reach advanced clinical evaluation. This pharmacological profile distinguishes it fundamentally from semaglutide (GLP-1R only) and tirzepatide (GLP-1R + GIPR dual), placing it at what researchers call the frontier of incretin-axis therapy design.

The mechanistic rationale for triple agonism rests on distinct and partially complementary contributions of each receptor to energy balance. GLP-1R activation suppresses appetite, slows gastric emptying, and enhances glucose-dependent insulin secretion — the core mechanism of approved GLP-1 drugs. GIPR activation contributes additive weight-loss effects and further enhances insulin secretion in the postprandial state; the magnitude of GIPR's contribution became clear only after tirzepatide's Phase 3 data showed weight loss substantially exceeding pure GLP-1R agonism. GCGR activation increases hepatic glucose output (the classical glucagon action) but also significantly increases energy expenditure, lipolysis in adipose tissue, and basal metabolic rate — an effect that GCGR monotherapy cannot exploit without hyperglycemia, but which in the balanced triple-agonist context is counteracted by concurrent GLP-1R and GIPR-driven insulin secretion. The result, in Phase 2 trial data, was a mean weight reduction of approximately 17.5% over 24 weeks at the highest studied dose, and approximately 24% over 48 weeks in an extended arm, figures that exceeded the 15–22% range reported for tirzepatide at equivalent timepoints. Phase 3 data (TRIUMPH program) are ongoing as of September 2026.

Retatrutide's half-life of approximately one week, achieved through an acyl chain that enables fatty-acid binding to albumin, supports once-weekly subcutaneous administration in clinical trials — the same dosing interval as semaglutide and tirzepatide. Peptides.SO tracks 59 Retatrutide listings from 28 distinct suppliers, all currently in stock, with per-mg pricing from $1.15 to $800.00 and a median of $38.00/mg (interquartile range $10.61 – $122.50/mg). CEO authorization for Retatrutide as a research-profile article topic was granted August 6, 2026 (PEP-1484).

Potential Research Applications: Triple receptor pharmacology (GLP-1R, GIPR, GCGR) co-agonism mechanism studies Comparison with monoagonist semaglutide and dual agonist tirzepatide in receptor binding studies Energy expenditure and thermogenic adipose-tissue effects of GCGR co-activation Hepatic glucose output and glycemic regulation under balanced triple-agonist conditions Lipolysis and lipid metabolism in combined incretin/glucagon-receptor activation models Appetite suppression and food-intake behavioral endpoints in rodent models Pharmacokinetic modeling of acylated peptide albumin-binding and half-life extension Once-weekly dosing regimen and subcutaneous depot absorption research Comparative efficacy modeling against dual-agonist incretin frameworks

Marketplace Snapshot (September 2026, Peptides.SO listings data): Tracked listings: 59 from 28 distinct suppliers (59 in stock, all mg-denominated) Median price per mg: $38.00 (interquartile range $10.61 – $122.50/mg) Lowest verified per-mg price: $1.15/mg — Apex Peptides ($1.15 for 1 mg) Second lowest: $3.56/mg — BulkGLP ($1,780 for 500 mg) Third lowest: $4.98/mg — Strate Labs ($299 for 60 mg) Note: Retatrutide is a relatively novel compound and its market price reflects limited manufacturing scale. The interquartile spread is wide because bulk-pack pricing ($1–$5/mg) and small-vial research pricing ($50–$120/mg) coexist in the same market.

Frequently Asked Questions: Q: What makes Retatrutide a triple agonist, and why is that pharmacologically significant? A: Retatrutide simultaneously activates GLP-1R (appetite suppression, insulin secretion), GIPR (additive weight loss, insulin potentiation), and GCGR (energy expenditure, lipolysis). No prior approved drug targets all three. The significance is that GCGR activation — which would cause hyperglycemia as a monotherapy — can be harnessed for its metabolic-rate and fat-mobilization effects when the hyperglycemic risk is offset by concurrent GLP-1R and GIPR-driven insulin secretion, giving the triple combination a theoretical metabolic ceiling above what dual or mono agonism can reach.

Q: How does Retatrutide compare with tirzepatide (Mounjaro/Zepbound) in Phase 2 weight-loss data? A: In Phase 2 data published in 2023, Retatrutide at its highest dose (12 mg weekly) produced approximately 17.5% mean weight reduction at 24 weeks and approximately 24% at 48 weeks. Tirzepatide at its highest approved dose (15 mg weekly) produces approximately 20–22% at 72 weeks in SURMOUNT trials. Direct comparison is difficult because trial populations differ, but the Phase 2 trajectory for Retatrutide at 48 weeks exceeded tirzepatide's benchmark, setting up Phase 3 TRIUMPH trials to confirm or modify that comparison.

Q: How many suppliers offer Retatrutide for research purchase, and at what pricing? A: Peptides.SO tracks 59 listings from 28 suppliers. The median per-mg price is $38.00 with the market's middle half ranging from $10.61 to $122.50/mg. Bulk-purchase options from suppliers like BulkGLP bring the per-mg cost under $5 for large orders, while small research vials (2–5 mg) typically run $50–$120/mg.

Q: What is Retatrutide's half-life, and how does this inform research protocols? A: Retatrutide has an approximately one-week effective half-life, achieved through a fatty-acid acyl chain that binds to albumin in plasma. For in vivo rodent studies, this typically translates to a once-weekly subcutaneous administration schedule that maintains steady-state exposure — similar to the clinical trial protocol. Researchers using weekly dosing in rats typically see a 2–3 week washout period before receptor resensitization.

Q: Is Retatrutide FDA-approved? A: No. Retatrutide is an investigational compound in Phase 3 clinical development by Eli Lilly. It is not approved for human use. Research-use material listed on this platform is sold strictly for preclinical and in vitro laboratory investigation and is not for human consumption.

Related Research on Peptides.SO: peptides.so/learn/retatrutide-triple-agonist-research peptides.so/peptide/tirzepatide peptides.so/peptide/semaglutide peptides.so/learn/best-glp-1-research-sources-2026 peptides.so/peptide/liraglutide peptides.so/tools/calculator

Cited Research: Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PubMed PMID: 37366315. Frías JP, Dahl D, Iyer NN, 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. 2023;402(10401):529-544. PubMed PMID: 37385278.

For laboratory research only. Not for human or veterinary use, diagnosis, treatment, cure, or prevention of any disease. THIS PRODUCT IS NOT FOR HUMAN CONSUMPTION.