What is RT3?

RT3 (developmental code LY3437943) is a long-acting synthetic peptide developed as a research tool for probing simultaneous signalling across three incretin-related receptors: GLP-1, GIP and glucagon. It is described in the academic literature as the first characterised triple receptor agonist in this class, and has become a reference compound for laboratory groups studying combined incretin biology, energy expenditure and metabolic regulation.

BuyRetaUK supplies RT3 as a sterile lyophilised powder at ≥99% HPLC purity, with a batch-specific Certificate of Analysis, packed for research handling in temperature-controlled UK storage. It is strictly for in-vitro laboratory use and is not approved for human or veterinary administration.

RT3 is a modified peptide whose sequence is engineered to bind the GLP-1, GIP and glucagon receptors simultaneously — a so-called triple agonist. The GLP-1 arm mirrors the mechanism of established compounds such as Sema; the GIP arm adds the second incretin axis leveraged by Tirz; the glucagon arm is unique to the triple class and is the mechanistic feature that distinguishes RT3 from every dual or single incretin agonist currently in wide research use.

In receptor pharmacology experiments RT3 has been characterised as a balanced agonist across the three targets, with a long-acting profile suited to weekly dosing regimens in the studies that reference it. In laboratory settings this profile is of interest for research models that require sustained combined incretin activity rather than repeated acute stimulation.

Published research references RT3 across metabolic, energy-balance and body-composition models — investigating the joint effect of GLP-1, GIP and glucagon receptor activity on food intake, adipose remodelling, glycaemic parameters and energy expenditure. Because it acts on all three receptors simultaneously, RT3 is often used as a reference compound in studies that compare triple, dual and single agonist activity side by side.

For laboratories building comparative datasets, RT3 typically appears alongside Tirz (dual GLP-1 / GIP) and Sema (single GLP-1) so that receptor-level contributions can be attributed. Our dedicated comparison guides at /rt3-vs-tirz and /rt3-vs-sema provide the exact receptor and class differences.

Every BuyRetaUK batch is produced to research-grade specifications, quarantined until analytical release, then dispatched from temperature-controlled UK storage with a batch-specific Certificate of Analysis. Full batch traceability — sequence identity, purity, appearance and cold-chain history — is maintained for every lot.

For a full account of our quality workflow see the Laboratory Quality Standards guide.

Identity and purity are confirmed by independent third-party laboratories using reverse-phase HPLC with UV detection and mass spectrometry. Our release specification is ≥99% HPLC purity. Endotoxin testing is performed via the LAL assay and appearance is recorded against the release specification.

The full anatomy of a peptide COA — how HPLC, mass spectrometry and endotoxin sections are structured, and how to cross-reference the batch printed on your vial — is explained in our COA guide at /knowledge-hub/certificate-of-analysis-guide.

Lyophilised RT3 vials are stored at 2–8°C protected from light. For long-term storage below -20°C is acceptable; repeated freeze-thaw of the lyophilised powder is not recommended.

Once reconstituted with bacteriostatic water the peptide is stored refrigerated (2–8°C) and used within approximately 30 days. Volume-per-dose calculations are handled by our /reconstitution-calculator.