GLP-3 RT is the most structurally elaborate peptide in this catalog: a 39-residue chain carrying three non-standard amino acids and a covalently attached fatty acid. The name needs immediate clarification — there is no human hormone called "GLP-3." It is a catalog shorthand, and the molecule it denotes is the one the research literature indexes as retatrutide. This article is a structural and handling profile: what the molecule is, the chemistry behind its protease resistance and long half-life, how it reads on analytical instruments, and the storage rules specific to a fatty-acylated peptide. It is written for laboratory reference and makes no clinical claims.
What GLP-3 RT actually is — and what "GLP-3" means
Start with the name, because it causes confusion. The endogenous incretin family has two members: glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2). There is no GLP-3. The "GLP-3" label is a catalog shorthand for "the generation past GLP-1" — a triple agonist rather than the single-target GLP-1 analogs most people have heard of. The "RT" is the tell: this is the molecule the peer-reviewed literature calls retatrutide (developmental code LY3437943).
- Sequence (backbone):
Y-Aib-EGTFTSDYSI-Aib-LDKKAQ-Aib-AFIEYLLEGGPSSGAPPPS(39 residues, three of them non-standard). - Average mass: ≈4731.4 g/mol, including the lipid modification.
- Key modifications: three 2-aminoisobutyric acid (Aib) residues at positions 2, 13, and 20, plus a C20 fatty diacid conjugated through a linker to a mid-sequence lysine.
- Origin: Synthetic, made by solid-phase synthesis with post-assembly lipidation. The scaffold is built on the GIP peptide backbone, capped with a C-terminal extension borrowed from exendin-4.
The sequence carries no cysteine, no methionine, and no tryptophan, so disulfide chemistry, methionine-sulfoxide oxidation, and tryptophan photolysis are all off the table. Three tyrosines (positions 1, 10, and 25) give it moderate light sensitivity. The features that define how this molecule behaves are the three Aib residues and the lipid chain, not the standard amino-acid side chains.
One peptide, three receptors
The defining structural fact about GLP-3 RT is that a single chain carries agonist activity at three distinct class-B G-protein-coupled receptors. In the published receptor pharmacology, the molecule binds and activates all three, each coupling through Gs to raise intracellular cAMP in its target cells:
- GLP-1 receptor (GLP-1R). The receptor shared with the single-target GLP-1 analogs most people have heard of.
- GIP receptor (GIPR). The receptor for glucose-dependent insulinotropic polypeptide. Co-agonism at GIPR alongside GLP-1R is the design the dual agonist tirzepatide established; GLP-3 RT retains it.
- Glucagon receptor (GCGR). The third arm, and the one a GIP/GLP-1 dual agonist does not carry. Its presence is what makes the molecule a triple rather than a dual agonist.
What separates one multi-agonist from another is not how many receptors it touches but the relative potency at each. The originating discovery pharmacology characterized GLP-3 RT as a balanced triple agonist, with the glucagon arm weighted to a defined fraction of the incretin-receptor activity rather than left to dominate. The in vitro potency ratios are reported in the receptor-pharmacology papers indexed under retatrutide.
Is GLP-3 RT the same thing as retatrutide?
Functionally, yes. "GLP-3 RT" is a catalog name; the molecule it denotes — a GIP/GLP-1/glucagon triple agonist with three Aib substitutions and a C20 fatty-diacid on a GIP-based backbone — is the compound the scientific literature indexes as retatrutide, developmental code LY3437943. There is no separate hormone or peptide called GLP-3.
The naming matters for a practical reason: it determines whether a researcher can find anything. Searching "GLP-3 RT" in a scientific database returns almost nothing, because that string is a vendor label rather than the molecule's research name. The structural identity above — sequence, Aib positions, lipid modification, and mass — is the reliable way to confirm what a vial actually contains, independent of whatever name is printed on it. A GHRH analog such as tesamorelin makes the same point from the opposite direction: shared design strategies across different molecules mean the exact sequence and modifications, not the marketing name, are the thing to verify.
Engineered for a six-day half-life
Native GLP-1 has a half-life of one to two minutes. It is destroyed almost immediately by dipeptidyl peptidase IV (DPP-4), which clips the N-terminal dipeptide, and cleared rapidly by the kidney. GLP-3 RT solves both problems with two separate pieces of chemistry.
The DPP-4 problem is the same one the GHRH analogs solve. Tesamorelin caps its N-terminus with a lipid group; CJC-1295 substitutes backbone residues. GLP-3 RT uses a third route — Aib substitution at the cleavage site — to defeat the identical enzyme. The albumin-binding fatty-acid strategy, meanwhile, is the same trick used by semaglutide and tirzepatide, and it is why all three are once-weekly molecules rather than daily ones.
Triple, dual, single: how the agonist classes line up
GLP-3 RT sits at the far end of a clear engineering progression. The same albumin-binding, DPP-4-resistant chassis carries a different number of receptor targets in each generation:
| Molecule | Receptor targets | Backbone | Approx. half-life |
|---|---|---|---|
| Semaglutide | GLP-1 only (single) | GLP-1 analog | ~7 days |
| Tirzepatide | GIP + GLP-1 (dual) | GIP-based | ~5 days |
| GLP-3 RT (retatrutide) | GIP + GLP-1 + glucagon (triple) | GIP-based | ~6 days |
The progression single → dual → triple is the headline, but the backbone row is the insider detail. Both the dual and triple agonists are built on the GIP peptide scaffold, not the GLP-1 one, even though GLP-1 is the better-known hormone. The marketing names emphasize GLP-1 because that is what the public recognizes; the chemistry started from GIP. Data from a dual agonist therefore does not transfer cleanly to the triple agonist, because the glucagon arm changes the receptor-activity profile in ways a GIP/GLP-1 molecule never models.
Where the molecule sits in the research record
Unlike the older research peptides in this library, whose literature is predominantly preclinical, the compound corresponding to GLP-3 RT has been characterized in both receptor-level pharmacology and a clinical-stage research program. For laboratory reference the useful point is what kind of record exists and where it is indexed — not the trial outcomes, which belong in their original clinical context.
- Receptor pharmacology. The binding and in vitro potency work across the three receptors, with the supporting preclinical models, was reported by the originating discovery group. This is the entry point for the mechanism described above.
- Clinical-stage research. A phase 2 program and subsequent analyses have been published, with a confirmatory phase 3 program (TRIUMPH) underway as of this writing. The reports are indexed under the molecule's research name, not the catalog label.
This profile is a chemistry-and-handling reference for laboratory use. It does not reproduce trial results or characterize any clinical effect, and the HelixCore product is supplied strictly for research and is not for human use.
Stability and handling for a lipidated peptide
In the sealed, lyophilized state GLP-3 RT follows the standard storage envelope, and the absence of cysteine and methionine means it has no oxidation watchpoint of the kind that constrains TB-500:
- Refrigerated (2–8°C): 24 months as a sealed lyophilized vial is the standard manufacturer-published spec.
- Frozen (−20°C): 36+ months, the research-archive storage temperature.
The complication is the lipid. A fatty-acylated peptide is amphiphilic — it has a water-loving peptide body and a fat-loving tail — which makes it behave partly like a surfactant. Two practical consequences follow, and the broader degradation framework is covered in our storage and stability article.
What the lipid changes:
- It foams aggressively. Surfactant-like molecules concentrate at the air-water interface and whip into foam under agitation. The universal no-shaking rule matters more here than for any unmodified peptide in this catalog.
- It self-associates. At higher concentrations the fatty chains drive the molecules to cluster into micelle-like assemblies. Work at modest concentrations and do not interpret a faint opalescence at high concentration as contamination without analytical confirmation.
Light sensitivity is moderate — three tyrosines, no tryptophan — so foil-wrap of refrigerated vials is sufficient and direct bench lighting between withdrawals should be avoided.
Reconstitution and analytical notes
Reconstitution
The standard reconstitution protocol applies, with the foaming caveat amplified: stream the bacteriostatic water against the glass wall, swirl with extreme gentleness, and never shake. Dissolution is fast at the milligram-per-mL concentrations typical for research use. Reconstituted and refrigerated, working stocks hold for 14–28 days; aliquot and freeze at −20°C for longer studies rather than freeze-thawing one vial repeatedly. The 5 mg/mL working ceiling that suits most peptides is conservative here — push concentration only with a reason, given the self-association behavior. Both the 10 mg and 30 mg formats pair with bacteriostatic water for reconstitution.
HPLC
The C20 diacid makes GLP-3 RT markedly more hydrophobic than its bare backbone, so it retains late on reverse-phase HPLC under a standard water/acetonitrile gradient. Lipidated peptides can show mild peak broadening from the self-association behavior; a competent CoA chromatogram still resolves a dominant main peak. The visual cues for reading one are in our CoA reading guide.
Mass spectrometry — the most important check
The single most diagnostic test for this molecule is mass. The fatty diacid and its linker add substantial mass to the peptide backbone, and the observed mass on ESI-MS must reflect the lipidated molecule at ≈4731.4 g/mol, appearing as multiply-charged ions. A product sold as "GLP-3 RT" whose observed mass matches the bare 39-residue backbone is missing its lipid — it is a different, much shorter-acting molecule regardless of what the label says. Confirm net peptide content and the observed mass against the lot's report in the open CoA library before use.
Common errors to avoid:
- Shaking the vial. A surfactant-like peptide foams instantly and the foam carries aggregated material. Swirl only, and let foam settle before withdrawing.
- Treating dual-agonist data as equivalent. Tirzepatide is a GIP/GLP-1 molecule; the glucagon arm makes GLP-3 RT a different research tool.
- Assuming "GLP-3" is a real hormone. It is a catalog name. The literature is indexed under retatrutide and LY3437943.
- Accepting a CoA mass that matches the naked backbone. The lipid must show up in the observed mass. A backbone-only mass means the material is not the lipidated triple agonist.
- Repeated freeze-thaw of one reconstituted vial. Aliquot first; thaw single portions.
Where to find primary literature
The "GLP-3 RT" string returns almost nothing in the scientific databases — search instead for "retatrutide" and "LY3437943", which together index the whole record. The originating discovery-group pharmacology is the starting point for the receptor-level mechanism, and the published phase 2 reports (Jastreboff et al., 2023; Rosenstock et al., 2023) are the clinical-stage entry points. For the broader engineering context — DPP-4 resistance and albumin-binding half-life extension applied to an endocrine peptide — the tesamorelin profile and the CJC-1295 comparison cover adjacent strategies.
