IGF-1 LR3: A Research Reference Guide to the Long R3 Growth Factor
By Lemon Labs Research Desk · Updated July 10, 2026
In short
IGF-1 LR3 (Long R3 IGF-1) is a modified analog of insulin-like growth factor 1 engineered for extended activity. Two changes — an arginine substitution at position 3 and a 13-amino-acid N-terminal extension — reduce its binding to IGF-binding proteins, which researchers study for prolonged receptor activity. It is a research-use-only reference compound.
What is IGF-1 LR3?
IGF-1 LR3 is an engineered version of insulin-like growth factor 1. "R3" refers to an arginine-for-glutamate substitution at position 3, and "Long" to a 13-residue N-terminal extension. Together these modifications lower its affinity for IGF-binding proteins (IGFBPs), which in research models extends how long it remains active relative to native IGF-1.
Mechanism studied in research
IGF-1 signals through the IGF-1 receptor to influence cell growth and proliferation pathways. Because IGF-1 LR3 evades IGFBP sequestration, researchers use it as a tool to study sustained IGF-1-receptor signaling in cell culture without the buffering effect of binding proteins.
Handling and quality
Supplied lyophilized; store cold, sealed, and protected from light, and reconstitute in the lab. Verify identity and ≥99% purity on the lot Certificate of Analysis.
Research-use-only statement
This compound is supplied strictly for in-vitro research and laboratory use. It is not a drug, supplement, food, or cosmetic, has not been evaluated by the FDA, and is not intended to diagnose, treat, cure, or prevent any disease. It is not for human or veterinary use. All information here summarizes published scientific literature for educational purposes for qualified researchers — it is not medical advice and does not describe human administration.
Reference compounds mentioned
Frequently asked
What does LR3 mean in IGF-1 LR3?
"Long R3" — a 13-amino-acid N-terminal extension plus an arginine substitution at position 3, modifications that reduce binding to IGF-binding proteins and extend activity in research models.
How is it different from regular IGF-1?
The LR3 modifications lower its affinity for IGF-binding proteins, so it stays active longer in cell-culture research than native IGF-1.
Is IGF-1 LR3 for human use?
No. It is a research-use-only reference compound, not for human or veterinary use.