Retatrutide (LY3437943) is a synthetic single-chain peptide developed by Eli Lilly that functions as a simultaneous agonist at three receptors: GIP (glucose-dependent insulinotropic polypeptide), GLP-1 (glucagon-like peptide-1), and GCGR (glucagon receptor). It features a C20 fatty diacid moiety enabling albumin binding and an extended half-life of approximately 6–7 days.

What is the half-life of Retatrutide?

Retatrutide has an extended half-life of approximately 6–7 days in human studies, achieved via its C20 fatty diacid modification that enables non-covalent albumin binding — a similar approach to that used in semaglutide.

Retatrutide (LY3437943) Research Guide — GIP/GLP-1/GCGR Triple Agonist

Retatrutide

LY3437943. A novel single-chain peptide simultaneously agonising GIP, GLP-1, and glucagon (GCGR) receptors. Features a C20 fatty diacid moiety for albumin binding, yielding an extended half-life of approximately 6–7 days. Currently the most advanced triple-agonist compound in published metabolic research.

≥99.4% Purity HPLC MS Identity Confirmed Triple Agonist GIP/GLP-1/GCGR Half-life ~6–7 days

Tri-Receptor Agonism: How Retatrutide Works

Retatrutide's defining characteristic is simultaneous agonism at three distinct but metabolically complementary receptors. Each contributes a distinct component to the compound's observed metabolic profile in research models:

GLP-1 Receptor

Glucose-dependent insulin secretion stimulation. Delayed gastric emptying (reduced caloric absorption rate). Centrally mediated appetite suppression via hypothalamic GLP-1R. Primary driver of glycaemic control in dual-agonist predecessors.

GIP Receptor

Acts synergistically with GLP-1R on beta cells to enhance insulin secretion at physiological glucose concentrations. Additionally modulates adipose tissue directly — GIP-R expression in white adipose tissue influences fatty acid uptake and lipid metabolism regulation.

Glucagon Receptor

Direct stimulation of GCGR in hepatocytes and adipocytes increases energy expenditure and drives lipolysis — bypassing the metabolic adaptation (downregulation of energy expenditure) typically observed in sustained caloric restriction research models.

The Albumin-Binding Modification

The C20 fatty diacid moiety appended to Retatrutide's backbone enables high-affinity, reversible non-covalent binding to serum albumin. This pharmacokinetic strategy — pioneered in semaglutide and expanded here — dramatically extends the plasma half-life from the minutes seen with native GLP-1 to approximately 6–7 days, enabling weekly administration in clinical research protocols. The albumin complex acts as a circulating depot, releasing free peptide gradually over time.

Differentiation from Prior GLP-1 Compounds

Compared to semaglutide (GLP-1R mono-agonist) and tirzepatide (GLP-1R/GIP-R dual agonist), retatrutide introduces glucagon receptor agonism as the third axis. This is pharmacologically significant because GCGR activation directly increases hepatic glucose production and, crucially, stimulates thermogenesis and lipolysis in a manner that does not appear to be counteracted by the GLP-1R component. Phase 2 data (Jastreboff et al., NEJM 2023) demonstrated mean weight reduction of approximately 17.5% at 24 weeks and up to 24.2% at 48 weeks in the highest dose group — exceeding results from dual-agonist predecessors at comparable timepoints in the research timeline.

Research Context: The data referenced above derives from Eli Lilly's Phase 2 SURMOUNT-J trial (NCT05394155) conducted in humans under clinical trial conditions with strict monitoring. Research compound procurement for in vitro or animal model work operates under entirely different conditions. No claims about efficacy in independent research are implied.

Batch Purity Documentation

Verified Purity — Independent Analysis

Retatrutide (LY3437943) · Batch AV-2025-RET-047

99.4%

RP-HPLC (C18) · MS/ESI+

Batch ID

AV-2025-RET-047

Test Date

14 Feb 2025

Method

RP-HPLC C18

Certificate of Analysis — Batch AV-2025-RET-047

Full HPLC chromatogram and mass spectrum confirming identity and purity. Issued by independent accredited laboratory. Available within 24 hours on request.

Laboratory Handling Protocol

Storage

Lyophilised: −20°C, sealed, protected from light and humidity. Stable ≥24 months.
Reconstituted: 2–8°C. Stable for up to 28 days (albumin-binding modification confers greater aqueous stability vs. standard peptides).
Avoid: Temperatures above 25°C for extended periods. Direct UV exposure. Repeated freeze-thaw cycles.

Reconstitution

Solvent: Bacteriostatic Water (0.9% benzyl alcohol) is preferred. Sterile saline (0.9% NaCl) is acceptable for single-use.
Volume: Add 1–2 mL per 5 mg vial. Swirl gently; do not agitate vigorously. The albumin-binding modification increases water solubility — dissolution typically occurs readily.
Stability note: Reconstituted Retatrutide exhibits greater aqueous stability than shorter linear peptides due to structural protection from the fatty acid modification. 28-day refrigerated stability has been documented in formulation research.

pH Sensitivity

Retatrutide is optimally stable between pH 4.0–7.0. Avoid alkaline reconstitution solvents. Standard bacteriostatic water (pH ~5.0–6.0) is appropriate.

Research Use Only. Retatrutide (LY3437943) is an investigational compound. It is not approved for human therapeutic use. For qualified laboratory research only. Handle in accordance with applicable biosafety regulations.

Frequently Asked Questions

Retatrutide (development code LY3437943) is a single-chain synthetic peptide developed by Eli Lilly & Company. It is the first published triple agonist simultaneously targeting GIP, GLP-1, and glucagon receptors. Its C20 fatty diacid modification enables albumin binding, extending plasma half-life to approximately 6–7 days and allowing weekly dosing in clinical protocols.

Tirzepatide (Mounjaro/Zepbound) is a dual GIP/GLP-1 receptor agonist. Retatrutide adds a third agonist activity at the glucagon receptor (GCGR), which directly stimulates lipolysis and energy expenditure. Phase 2 data suggests this additional receptor engagement may produce greater metabolic effects, though direct head-to-head trials have not been published.

Approximately 6–7 days in human Phase 2 studies, achieved via the C20 fatty diacid modification enabling non-covalent albumin binding — the same structural strategy employed in semaglutide (Ozempic/Wegovy), but with modifications specific to the Retatrutide backbone.

Bacteriostatic Water (0.9% benzyl alcohol, sterile) is the recommended reconstitution solvent for multi-use research vials. The albumin-binding fatty acid modification confers significantly greater aqueous solubility compared to unmodified peptides. Reconstituted solutions in bacteriostatic water are stable for up to 28 days at 2–8°C.

As of the date of this publication (2025), Retatrutide is an investigational compound that has completed Phase 2 trials. It is not FDA-approved or commercially available as a therapeutic drug. AVREA supplies Retatrutide exclusively as a research compound for qualified laboratory investigators. All research use must comply with applicable local regulations.