IGF-1 LR3
Engineered insulin-like growth factor 1 variant with extended half-life.
Also known as: Long R3 IGF-1, Long Arg3 IGF-1
IGF-1 LR3 is a modified version of recombinant human insulin-like growth factor 1 used in cell culture research and sold as a research peptide. Its modifications reduce binding to IGF binding proteins and extend its biological half-life compared with native IGF-1.
Key facts
- Class
- Modified growth factor
- Parent molecule
- Insulin-like growth factor 1 (IGF-1)
- Modifications
- Arginine substitution at position 3 plus a 13 amino acid N-terminal extension
- WADA status
- Prohibited under S2 as an IGF-1 mimetic
- Primary use
- Cell culture supplement in research; also sold as a research peptide
What is IGF-1 LR3?
Insulin-like growth factor 1 is a 70 amino acid protein produced mainly by the liver in response to growth hormone. It mediates many of the growth-promoting effects of growth hormone on peripheral tissues. IGF-1 LR3 is an engineered variant with two changes: a substitution of arginine for glutamic acid at position 3, and a 13 amino acid extension at the N-terminus.
These modifications reduce the affinity of IGF-1 LR3 for IGF binding proteins (IGFBPs), which normally bind and sequester circulating IGF-1. The result is a molecule with a longer half-life and higher potency in cell-based assays than unmodified recombinant IGF-1.
Mechanism of action
IGF-1 LR3 binds the IGF-1 receptor on target cells and activates the same downstream signaling pathways as native IGF-1, including the PI3K/Akt pathway and the MAPK pathway. These pathways drive cellular proliferation, protein synthesis, and metabolic effects.
- •Binds the IGF-1 receptor on target cells
- •Activates PI3K/Akt and MAPK intracellular signaling
- •Reduced affinity for IGFBPs extends its half-life compared with native IGF-1
- •Also binds the insulin receptor at higher concentrations
Research context
IGF-1 LR3 has been used extensively as a supplement in mammalian cell culture, particularly in biomanufacturing applications where stable growth factor signaling is needed. Published manufacturing and process development literature describes its advantages over native IGF-1 in reducing the variability associated with IGFBP interactions.
Beyond cell culture, IGF-1 LR3 has not been evaluated in large human clinical trials. Mecasermin (Increlex) is a different, unmodified form of recombinant human IGF-1 that is FDA-approved for severe primary IGF-1 deficiency, but mecasermin is chemically distinct from IGF-1 LR3 and the two should not be confused.
Safety and regulatory context
IGF-1 LR3 is not approved by the FDA or any regulatory agency for human therapeutic use. The World Anti-Doping Agency prohibits IGF-1 and its analogs and mimetics under section S2 of the Prohibited List at all times.
Because IGF-1 signaling is involved in cell proliferation, there are theoretical concerns regarding growth factor administration in the context of cancer risk. Published clinical safety data for IGF-1 LR3 specifically are limited. Material sold as research IGF-1 LR3 is intended strictly for laboratory use and is not cleared for human administration.
Research sourcing
IGF-1 LR3 is listed by our research partner, GLP1 Research Lab, which supplies lyophilized peptides for laboratory use. Listings include product identifiers relevant to research documentation.
View IGF-1 LR3 listing at GLP1 Research LabAffiliate partnership. Metabolic Playbook may earn a commission on purchases made through this link at no additional cost to the researcher.