IGF-1LR3

Overview

IGF-1 LR3 (Long Arginine 3-Insulin-like Growth Factor 1) is a synthetic, 83-amino acid analog of human IGF-1, modified with an arginine substitution at position 3 and a 13-amino acid N-terminal extension. These structural modifications dramatically reduce its binding affinity to IGF-binding proteins (IGFBPs), particularly IGFBP-3, increasing its bioavailability and extending its half-life. IGF-1 LR3 is approximately three times more potent than native IGF-1 and is used in research investigating cellular growth, anabolic signaling, metabolic regulation, and tissue regeneration.

Mechanism of Action

IGF-1 LR3 binds to and activates the IGF-1 receptor (IGF-1R), triggering downstream signaling cascades including the PI3K/Akt/mTOR pathway, which promotes protein synthesis and cell survival, and the MAPK pathway, which stimulates cellular proliferation and differentiation. By evading rapid binding to IGFBPs, it remains biologically active in circulation significantly longer than endogenous IGF-1.

Research and Off-Label Applications

Investigated for skeletal muscle growth, repair, and satellite cell activation, fat metabolism and body recomposition, tissue regeneration and recovery, glucose metabolism and insulin sensitivity, and neurological and anti-aging research.

Administration

Administered via subcutaneous injection. Research cycles typically range from 4–6 weeks. IGF-1 LR3 is not FDA-approved for any indication.

Potential Adverse Effects

Potential concerns include effects on glucose metabolism and insulin sensitivity, risk of cellular proliferation in individuals with existing malignancies, and joint or soft tissue swelling. Long-term safety data in humans is limited.

Pharmacokinetics

Half-life: approximately 20–30 hours, compared to 12–15 hours for native IGF-1.