IGF-1 LR3 (Long Arginine 3-IGF-1), also known as LR3-IGF-1 (CAS 946870-92-4), is a synthetic 83-amino acid protein and lengthened analogue of human insulin-like growth factor 1 (IGF-1). With a molecular weight of 9117.60 g/mol, IGF-1 LR3 differs from native IGF-1 in two key structural respects: an arginine substitution at position 3 in place of glutamic acid, and an additional 13-amino acid extension at the N-terminus. These modifications confer markedly reduced binding affinity for insulin-like growth factor-binding proteins (IGFBPs). Produced via solid-phase peptide synthesis, Long R3-IGF-1 acts as an agonist at the IGF-1 receptor (IGF-1R).

IGF-1 LR3 has been extensively investigated in preclinical cell biology and growth factor research. Its altered IGFBP binding profile has made Long Arginine 3-IGF-1 a key reference compound in studies examining IGF-1R-mediated signalling independently of IGFBP-dependent regulatory mechanisms. In vitro studies in L6 rat myoblast and fibroblast cell preparations have investigated Long Arginine 3-IGF-1’s receptor activation kinetics, characterising IGF-1R-mediated biological potency relative to native IGF-1 as a function of IGFBP secretion and receptor engagement [1]. In vivo guinea pig studies have examined the pharmacokinetic implications of reduced IGFBP binding, documenting reduced plasma IGF-I, IGF-II and IGF binding protein concentrations alongside organ-selective growth effects following LR3-IGF-1 infusion relative to endogenous IGF-I [2].

IGF-1 LR3 is manufactured in a cGMP compliant laboratory to a guaranteed purity of 98% or above. Every batch is independently tested using HPLC and MS-UPLC analysis before dispatch. Vials are vacuum sealed and stored in a temperature controlled, monitored cold storage system. Certificates of Analysis are available on request.

Sold strictly for in vitro research purposes only. Not for human consumption. Intended for use by qualified researchers in laboratory settings only.

Editorial Team

Dr. Martina Rossi, PhD

Scientific Contributor and Reviewer

Reviewed and approved 14 June 2026

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