IGF-1 LR3

IGF-1 LR3 (Long R3 IGF-1) is a modified analogue of insulin-like growth factor 1 (IGF-1) incorporating two key structural modifications: (1) an arginine substitution at position 3 (R3) in the IGF-1 sequence, and (2) an extension of the N-terminus with a 13-amino acid 'Long' peptide tail. Both modifications target the same objective as the IGF-1 DES truncation — reducing binding to IGF-binding proteins (IGFBPs) — but through a different structural strategy. The R3 substitution alters the IGFBP contact surface, reducing affinity for IGFBP-3 and other binding proteins, while the Long N-terminal extension sterically hinders IGFBP engagement. The combined effect is a dramatic reduction in IGFBP binding, making IGF-1 LR3 significantly more bioavailable than full-length IGF-1. Additionally, the modifications extend the peptide's half-life from the ~15 minutes of native IGF-1 to approximately 20-30 hours, providing sustained IGF-1 receptor (IGF1R) activation. Like IGF-1 DES, IGF-1 LR3 retains full affinity for the IGF-1 receptor, activating the PI3K/Akt and MAPK/ERK signalling cascades that drive cell proliferation, survival, and differentiation. The extended half-life and enhanced bioavailability make IGF-1 LR3 suitable for research requiring sustained IGF-1 receptor signalling, as opposed to the shorter-acting but highly potent IGF-1 DES.