IGF-1 LR3
A long-acting IGF-1 analog with N-terminal extension and reduced IGFBP binding, studied for sustained IGF-1 receptor signaling in research.
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What is IGF-1 LR3?
IGF-1 LR3 (Long R3 IGF-1) is a synthetic analog of human insulin-like growth factor 1 (IGF-1), modified to dramatically extend its biological half-life and free bioactivity. Native IGF-1 is a 70-amino-acid peptide hormone that mediates most of the anabolic and growth-promoting effects of growth hormone. IGF-1 LR3 differs from native IGF-1 in two specific ways: a 13-amino-acid extension at the N-terminus (the “Long” portion of the name) and an arginine substitution at position 3 (the “R3”) replacing the native glutamic acid.
IGF-1 LR3 is notable in research for its dramatically extended free bioactivity. The arginine substitution at position 3 reduces the peptide’s affinity for IGF binding proteins (IGFBPs), which normally bind and sequester approximately 98% of circulating IGF-1. By escaping IGFBP binding, IGF-1 LR3 remains in its free, bioactive form for substantially longer than native IGF-1, with circulating half-life of approximately 20-30 hours compared to 10-15 minutes for native IGF-1. These modifications were originally developed as research tools for studying IGF-1 signaling without the rapid clearance and IGFBP sequestration that complicate work with native IGF-1.
Mechanism of action
IGF-1 LR3’s mechanisms of action have been investigated across multiple pathways:
- IGF-1 receptor activation: The peptide binds and activates the IGF-1 receptor (IGF-1R) with high affinity, triggering tyrosine kinase signaling cascades including the PI3K/Akt and Ras/MAPK pathways that produce classical anabolic effects.
- Reduced IGFBP binding via Arg³ substitution: The arginine substitution at position 3 dramatically reduces affinity for IGF binding proteins (IGFBP-1 through IGFBP-6), allowing the peptide to circulate predominantly in its free bioactive form rather than being sequestered.
- Extended half-life via N-terminal extension: The combined effect of reduced IGFBP binding and the 13-amino-acid N-terminal extension produces a circulating half-life of 20-30 hours, dramatically exceeding native IGF-1.
- Anabolic and proliferative signaling: Activation of IGF-1R produces effects including increased protein synthesis, cellular proliferation, glucose uptake, and inhibition of apoptosis across multiple tissue types.
- Insulin receptor cross-reactivity: IGF-1 LR3 has some cross-reactivity at the insulin receptor due to structural similarity between IGF-1 and insulin, producing some hypoglycemic potential particularly at higher doses.
Research applications
IGF-1 LR3 has been investigated across several research domains, with the most active areas including:
- IGF-1 signaling research: The compound’s extended half-life and free bioactivity make it useful for research examining IGF-1 receptor signaling, downstream pathway activation, and tissue-level effects of sustained IGF-1 receptor stimulation that would be difficult to study with rapidly cleared native IGF-1.
- Cell culture and bioprocessing applications: IGF-1 LR3 is widely used to support growth and proliferation of various cell lines, with the extended bioactivity reducing the frequency of media changes and providing more consistent growth signaling compared to native IGF-1.
- Muscle and anabolic research: Studies have examined effects in models of muscle growth, recovery, and protein synthesis, with documentation of effects on muscle hypertrophy markers and protein synthesis rates in research contexts.
- Cardiac and neuroprotection research: Models have examined IGF-1 LR3 in contexts including cardiac protection and neuroprotection, drawing on the well-characterized roles of IGF-1 signaling in these tissues.
- Tissue repair research: Studies have examined effects on tissue regeneration processes that depend on IGF-1 receptor signaling, including muscle, tendon, and bone repair contexts.
This compound is intended for laboratory research use only. It has not been approved for human therapeutic use by any regulatory agency.
Storage & reconstitution
In its lyophilized form, IGF-1 LR3 tolerates ambient temperatures during shipping but should be stored long-term at -20°C, protected from light. The compound is sensitive to pH and temperature. Properly stored lyophilized peptide remains stable for 24 months or longer.
Once reconstituted with bacteriostatic water for injection or acidified saline per supplier recommendations, IGF-1 LR3 solutions should be stored refrigerated at 2-8°C and used within 28 days. Avoid repeated freeze-thaw cycles, which can degrade peptide structure and reduce activity.
Visual inspection should be performed before each use. The reconstituted solution should be clear and colorless. Reject any solution that appears cloudy, discolored, or contains visible particulate matter.
For step-by-step reconstitution calculations, see our reconstitution calculator.
For laboratory research use only. The compound described on this page is intended exclusively for in vitro research and laboratory experimentation by qualified researchers and is not for human or veterinary use. It is not a drug, food, dietary supplement, or cosmetic, and has not been approved by the FDA, Health Canada, EMA, or any other regulatory authority for the diagnosis, treatment, cure, mitigation, or prevention of any disease or medical condition. The information provided on this page is for educational and reference purposes only and does not constitute medical advice. By accessing this content you confirm that you are a qualified researcher purchasing for legitimate laboratory purposes.