For Research Purposes Only. This page summarizes published preclinical and clinical research. It does not constitute medical advice and is not a recommendation for human use. Always consult a qualified healthcare professional.
Retatrutide
Tri-agonist targeting GLP-1, GIP, and glucagon receptors simultaneously. Phase II data reported the highest mean weight loss of any single compound studied to date.
Overview
Retatrutide (LY3437943) is a 36-amino-acid synthetic peptide developed by Eli Lilly that simultaneously activates three receptors: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and the glucagon receptor. This tri-agonist profile represents the next incremental step in the incretin-based drug development trajectory that began with GLP-1 agonists and advanced to dual GIP/GLP-1 agonists with tirzepatide. The addition of glucagon receptor agonism is theorized to further increase energy expenditure through thermogenesis and enhanced fat oxidation, on top of the appetite suppression and insulin sensitization shared with GLP-1-class agents. Glucagon receptor agonism also has established lipid-lowering and hepatic fat-reducing effects, which may be particularly relevant for metabolic liver disease applications.
Phase II clinical trial results published in the New England Journal of Medicine (Jastreboff et al., 2023) generated significant scientific attention. The trial enrolled 338 adults with obesity and randomized participants to five doses of retatrutide (1mg, 4mg, 8mg, or 12mg weekly) or placebo. At 48 weeks, mean weight loss at the 12mg dose reached 24.2%, with a remarkable 26.2% reduction observed in the completer analysis. Simultaneously, significant reductions were observed in waist circumference, liver fat fraction (−81.7% in a subset), triglycerides, and blood pressure. These results exceeded the 68-week Phase III data from semaglutide and the 72-week Phase III data from tirzepatide, both of which had shorter treatment durations — direct comparison requires caution, but the scale of effect was notable.
Retatrutide entered Phase III clinical development in 2023 under multiple registered trials for obesity, type 2 diabetes, and metabolic dysfunction-associated steatohepatitis (MASH). As of early 2026, it has not received FDA approval and remains an investigational compound. Research-grade retatrutide sold by peptide vendors is distinct from the investigational pharmaceutical compound and is intended exclusively for laboratory research purposes.
Research Status
Jastreboff et al. (NEJM 2023): Phase II, 338 adults with obesity. 24.2% mean weight loss at 48 weeks (12mg/week); 81.7% reduction in liver fat in assessed subset. Multiple Phase III trials registered at clinicaltrials.gov (search: retatrutide). Ongoing MASH and T2D trials.
Common Research Protocols
Dosing above is from the published Phase II clinical trial protocol. Retatrutide has not been approved and does not have established prescribing information. Research-grade vials require reconstitution and are not equivalent to the investigational pharmaceutical compound. This is for educational reference only.
Storage & Handling
Store lyophilized research retatrutide at −20°C. Once reconstituted, store at 4°C and use within 28 days. Avoid freeze-thaw cycles after reconstitution.
What to Look for When Buying
Retatrutide is the most structurally complex peptide in the GLP class currently tracked by PepVendors — a 36-amino-acid molecule with a tri-receptor profile. Synthesis complexity means purity and fill accuracy vary more than with simpler compounds. Third-party HPLC testing is essential.
Finnrick Analytics has begun testing retatrutide from vendors. Given that it is newer to market, the number of independently tested batches per vendor may be limited — factor this into your confidence level when assessing quality.
Because retatrutide is still investigational (no FDA approval), it is a newer and less-established market. The vendor landscape is earlier-stage than for semaglutide or tirzepatide. Exercise additional scrutiny on vendor history and COA documentation.
Retatrutide's Phase II data involved escalating doses over 24 weeks to reach the maximum. The research vial sizes (2mg, 5mg) reflect the lower end of this titration range. Verify vial concentration matches the stated label before any research use.
As with all GLP-1 class peptides, verify that the COA specifies HPLC purity (not just mass spec identity) and that it includes fill/quantity accuracy data.
Compare Vendor Pricing
PepVendors tracks live pricing for Retatrutide across multiple vendors, updated weekly. Compare price per mg, available sizes, and purity data side by side.
Compare Retatrutide prices →Third-Party Purity Data
Full data at finnrick.com →Independent HPLC test results from Finnrick Analytics. Purity values are averages across multiple samples. Check the Finnrick vendor page for batch-level detail.
For Research Purposes Only — Not Medical Advice. The information on this page is compiled from published peer-reviewed research, publicly available clinical trial data, and independent third-party testing results. It is intended solely as an educational reference for researchers.
Nothing on this page constitutes medical advice, a diagnosis, or a treatment recommendation. Peptides listed as research chemicals are not approved for human consumption unless explicitly noted as FDA-approved pharmaceuticals. PepVendors is a price comparison and information platform — we do not manufacture, sell, or distribute any compounds. Always consult a qualified and licensed healthcare professional before considering any compound for personal use.