IGF-1 LR3 Research Protein

What is IGF-1 LR3?

IGF-1 LR3 is a lab-modified, long-acting version of IGF-1 (insulin-like growth factor 1). Its changes reduce binding to the proteins that normally limit IGF-1, giving researchers a tool to study extended IGF-1 signaling in muscle, fat and growing cells.

• A long-acting IGF-1 with an added sequence at one end
• Reduced binding to IGF-binding proteins gives it a much longer active life
• Studied in animal research for its effects on muscle signaling and satellite cells
• Investigated for its effects on IGF-1 signaling and metabolism

For research use only. Not approved for human therapeutic use.

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 produced to research-grade standards and independently verified by third-party 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.

References

1Francis GL, Ross M, Ballard FJ, Milner SJ, Senn C, McNeil KA, et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992 Jun;8(3):213–23. .PubMed PMID: 13787422Conlon MA, Tomas FM, Owens PC, Wallace JC, Howarth GS, Ballard FJ. Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig. J Endocrinol. 1995 Aug;146(2):247–53. .PubMed PMID: 7561636

Scientific Review

Dr. Martina Rossi, PhD

Scientific Contributor and Reviewer

Reviewed for scientific accuracy, 14 June 2026

View credentials →

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 produced to research-grade standards and independently verified by third-party 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.

References

1Francis GL, Ross M, Ballard FJ, Milner SJ, Senn C, McNeil KA, et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992 Jun;8(3):213–23. .PubMed PMID: 13787422Conlon MA, Tomas FM, Owens PC, Wallace JC, Howarth GS, Ballard FJ. Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig. J Endocrinol. 1995 Aug;146(2):247–53. .PubMed PMID: 7561636

Scientific Review

Dr. Martina Rossi, PhD

Scientific Contributor and Reviewer

Reviewed for scientific accuracy, 14 June 2026

View credentials →CAS Number946870-92-4Molecular Weight9,117.57 g/molPurity≥98%Physical FormLyophilised PowderManufacturingManufactured in an ISO9001 Certified LaboratoryTestingHPLC + MS-UPLCSKUIGF1LR3

Lyophilised powder: store at -20 °C or below, away from light and moisture. Once reconstituted in an appropriate laboratory diluent (e.g. sterile water, PBS, or assay buffer), store at 2–8 °C and use within the validated period for your protocol. Do not refreeze.

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 produced to research-grade standards and independently verified by third-party 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.

References

1Francis GL, Ross M, Ballard FJ, Milner SJ, Senn C, McNeil KA, et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992 Jun;8(3):213–23. .PubMed PMID: 13787422Conlon MA, Tomas FM, Owens PC, Wallace JC, Howarth GS, Ballard FJ. Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig. J Endocrinol. 1995 Aug;146(2):247–53. .PubMed PMID: 7561636

Scientific Review

Dr. Martina Rossi, PhD

Scientific Contributor and Reviewer

Reviewed for scientific accuracy, 14 June 2026

View credentials →CAS Number946870-92-4Molecular Weight9,117.57 g/molPurity≥98%Physical FormLyophilised PowderManufacturingManufactured in an ISO9001 Certified LaboratoryTestingHPLC + MS-UPLCSKUIGF1LR3

Lyophilised powder: store at -20 °C or below, away from light and moisture. Once reconstituted in an appropriate laboratory diluent (e.g. sterile water, PBS, or assay buffer), store at 2–8 °C and use within the validated period for your protocol. Do not refreeze.