IGF-1 LR3

IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a recombinant analog of human IGF-1 modified to have significantly enhanced potency and extended half-life. The modifications include a 13-amino acid N-terminal extension and an arginine substitution for glutamic acid at position 3 (R3), which together reduce binding to IGF binding proteins (IGFBPs).

Native IGF-1 circulates bound to IGFBPs (particularly IGFBP-3), which modulate its bioavailability and half-life. By evading IGFBP binding, IGF-1 LR3 maintains a higher free concentration and extended duration of action, making it approximately 2-3 times more potent than standard IGF-1 in cell culture and research applications.

The compound activates the IGF-1 receptor (IGF-1R) with similar affinity to native IGF-1, triggering downstream signaling through PI3K/Akt and MAPK pathways that promote cell survival, proliferation, and protein synthesis. These effects are particularly pronounced in skeletal muscle, where IGF-1 stimulates hypertrophy through both myofiber growth and satellite cell activation.

Research applications include studies of muscle growth, cell biology, and cancer, where IGF-1 signaling plays important roles. The enhanced potency and stability of IGF-1 LR3 provide advantages for in vitro and ex vivo research, though its modified binding profile should be considered when extrapolating to in vivo IGF-1 physiology.