IGF-1 LR3 is a synthetic peptide similar to human insulin-like growth factor 1 with enhanced bioavailability. IGF-1 LR3 is a longer peptide (L) and contains a substitution of arginine for glutamic acid at the third position in the peptide (R3). There is also an additional 13 amino acids added onto the N-terminal of the peptide, making it 83 total amino acids compared to only 70 amino acids in IGF-1.¹ These alterations enhance the half-life of IGF-1 LR3 to 20 to 30 hours, compared to 12 to 15 hours for IGF-1.² IGF-1 LR3 also has three times the potency of IGF-1.³ This increase in potency is driven by decreased binding of insulin-like growth factor binding proteins, which in turn increases the overall biological activity of the peptide.^1,2 IGF-1 is a peptide similar to insulin that binds to its receptor IGFR1 to promote cell growth, along with muscle fiber growth and differentiation.^4,5 IGF-1 LR3 is used both in in vitro and in vivostudies as an alternative to IGF-1, as it mimics the function and receptor binding efficiently. For example, one study looking at the effects of IGF-1 LR3 on fetal myocyte proliferation and heart mass in a sheep model found that the peptide stimulates the proliferation of cardiomyocytes while also increasing blood flow to the heart.⁶ Another study treated C2C12 cells in vitro and mice in an in vivo mouse tumor model with IGF-1 LR3 to demonstrate its role in blocking muscle wasting in cancer.⁵ IGF-1 LR3 activates the PI3K/AKT pathway and blocks the upregulation of muscle wasting factors, along with promoting protein synthesis.⁵

IGF-1 LR3 comes in a lyophilized white powder at a concentration of 1 mg/vial.