The polypeptide Long R3 Insulin-like Growth Factor-I (IGF1 LR3) is an 83 amino acid analog of IGF-I actually comprising the complete IGF-1 sequence but with the substitution of an Arginine (Arg) for the Glutamic Acid (Glu) at position 3, as well as a 13 amino acid extension peptide. This sequence change causes IGF-1 LR3 to avoid binding to proteins and allow it to have a much longer half life, around 20-30 hours.