Comparison
IGF-1 LR3 vs. Mod GRF (1-29)
Two peptides side-by-side — identity, evidence base, legal status and known adverse events.
Identity
Category
Growth
Growth
CAS no.
143045-27-6
863288-34-0
Molecular weight
9117.6 g/mol
3367.9 g/mol
Half-life
21 h
0.5 h
Sequence
MFPAMPLSSLFVNGPRTLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSATyr-D-Ala-Asp-Ala-Ile-Phe-Thr-Gln-Ser-Tyr-Arg-Lys-Val-Leu-Ala-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Leu-Ser-Arg-NH2Mechanism of action
IGF-1 LR3
IGF-1 LR3 is a recombinantly produced variant of human IGF-1. Two changes define its properties: (1) at position 3, glutamic acid is replaced by arginine; (2) a 13-amino-acid sequence is added at the N-terminus ('Long'). Both modifications drastically reduce affinity for the six IGF-binding proteins (IGFBP-1 to -6) that normally bind native IGF-1 in the blood and regulate its availability at the receptor. As a result, a larger fraction of the molecule is freely available to bind the type-1 IGF receptor (IGF-1R) — the same receptor as native IGF-1. In preclinical models and cell culture, LR3 IGF-1 therefore acts as a more potent agonist than unmodified IGF-1. The downstream signalling pathway (PI3K/Akt and MAPK) is identical to that of IGF-1; the modification changes bioavailability, not the receptor target.
Mod GRF (1-29)
Synthetic analogue of the first 29 amino acids of growth-hormone-releasing hormone (GHRH 1-29). Four amino-acid substitutions (D-Ala at position 2, Gln at 8, Ala at 15, Leu at 27) are intended to slow degradation by dipeptidyl peptidase-IV and increase enzymatic stability relative to native GHRH. Like the native hormone and sermorelin, it binds the GHRH receptor on somatotroph cells of the anterior pituitary; mechanistically this is expected to stimulate endogenous growth-hormone release. Unlike the DAC-conjugated CJC-1295 variant, it lacks albumin binding, so its duration of action remains short.
Evidence base
Highest evidence
Animal model
Human trial
Studies
4
4
of which in humans
0
4
Effects recorded
4
3
Open conflicts
1
1
Documented adverse events
1
0
Legal status
Full entries
Frequently asked questions
- What is the difference between IGF-1 LR3 and Mod GRF (1-29)?
- IGF-1 LR3 is classified as "Growth", while Mod GRF (1-29) is classified as "Growth". IGF-1 LR3: Synthetic analogue of insulin-like growth factor 1 (IGF-1) carrying an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. These modifications lower binding to IGF-binding proteins and extend its duration of action relative to native IGF-1. LR3 IGF-1 is primarily an established cell-culture reagent (serum-free media, bioprocessing); it is NOT an approved human medicine. Use in the bodybuilding grey market is described; as an IGF-1 analogue, LR3 IGF-1 falls under the WADA anti-doping prohibition. Mod GRF (1-29): Tetrasubstituted synthetic analogue of GHRH(1-29), traded on the grey market as "CJC-1295 without DAC". Closely related to sermorelin (GHRH 1-29); a short-acting growth-hormone-releasing-hormone analogue often combined with a GHRP/ghrelin mimetic. Not approved as a medicinal product. Direct human trials of this exact analogue are essentially absent; the factual basis relies on related GHRH(1-29) analogues. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
- Which peptide is better supported by science, IGF-1 LR3 or Mod GRF (1-29)?
- The highest available evidence level is "Animal model" for IGF-1 LR3 and "Human trial" for Mod GRF (1-29). A higher evidence level means more robust data, but says nothing about suitability for an individual. The full body of evidence is on each peptide's own page.
- What is the legal status of IGF-1 LR3 and Mod GRF (1-29) in Germany and the United States?
- Germany: IGF-1 LR3 — Unapproved, Mod GRF (1-29) — Unapproved. United States: IGF-1 LR3 — Unapproved, Mod GRF (1-29) — Research only. These are factual summaries with source and review date on the individual pages.