IGF-1 LR3 — 1mg

IGF-1 LR3 (Long R3 IGF-1) is an 83-amino acid engineered analog of recombinant human insulin-like growth factor 1 (IGF-1). Two structural modifications distinguish it from native IGF-1: an arginine substitution at position 3 (R3) that reduces binding affinity to the IGF binding proteins (IGFBPs), and a 13-amino acid N-terminal extension that further stabilizes the peptide against degradation. The combined effect is a dramatic extension of circulating half-life — from approximately 20 minutes for native IGF-1 to 20–30 hours for IGF-1 LR3 — and a significant increase in bioavailable peptide at target tissues since IGFBP sequestration is reduced.

Functionally, IGF-1 LR3 retains full agonist activity at the IGF-1 receptor (IGF1R), driving PI3K/Akt and MAPK signaling cascades that promote protein synthesis, cell proliferation, and survival. The peptide's anabolic effects are most pronounced in skeletal muscle, where it stimulates satellite cell activation and myoblast proliferation, and in connective tissue, where it accelerates fibroblast-mediated collagen synthesis. The extended half-life means that sustained receptor occupancy can be achieved with less frequent administration than native IGF-1 would require — a practical advantage in research protocols.

Because of its potency, IGF-1 LR3 is commonly used in cell culture research at very low concentrations (ng/mL range) as a mitogenic factor and in vivo research focused on muscle hypertrophy, tendon and ligament repair, and anabolic response characterization. Its reduced IGFBP binding also makes it useful in research contexts where IGFBP sequestration would otherwise complicate interpretation — for example, in studies examining tissue-specific IGF-1 signaling independent of systemic IGFBP regulation. The peptide's potent effects on cell proliferation require careful dose handling in any proliferation-sensitive research context.