IGF-1 LR3

Long arginine 3-IGF-1, abbreviated as IGF-1 LR3 or LR3-IGF-1, is a synthetic protein and lengthened analogue of human insulin-like growth factor 1. It differs from native IGF-1 in that it possesses an arginine instead of a glutamic acid at the third position in its amino acid sequence, and also has an additional 13 amino acids at its N-terminus, for a total of 83 amino acids. The consequences of these modifications are that IGF-1 LR3 retains the pharmacological activity of IGF-1 as an agonist of the IGF-1 receptor, has very low affinity for the insulin-like growth factor-binding proteins, and has improved metabolic stability. As a result, it is approximately three times more potent than IGF-1, and possesses a significantly longer half-life of about 20–30 hours.
The amino acid sequence of IGF-1 LR3 is MFPAMPLSSL FVNGPRTLCG AELVDALQFV CGDRGFYFNK PTGYGSSSRR APQTGIVDEC CFRSCDLRRL EMYCAPLKPA KSA.