Compounds / IGF-1 LR3

IGF-1 LR3

Also known as: Long R3 IGF-1, LR3-IGF-1

No human data Not FDA-approved · research reagent Category: Growth Factors

The compounds described in this library are research-use-labeled chemicals and are not FDA-approved for human use. This content is factual scientific reference drawn from published literature. It is not medical, dosing, or purchasing advice. VialReport does not sell, supply, or distribute any compound.

Short summary

A modified analogue of insulin-like growth factor 1, engineered to resist binding by IGF binding proteins and therefore to remain active longer. It was developed as a cell-culture research reagent, not as a therapeutic, and has no human clinical evidence in that form.

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Origin and Development

Human IGF-1 is a 70-amino-acid hormone produced mainly by the liver under growth hormone stimulation. IGF-1 LR3 is an engineered variant carrying an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. Those changes were made specifically to reduce binding to IGF binding proteins, which normally sequester circulating IGF-1. The analogue was developed for use in cell culture, where it is valued precisely because it stays active in media that would otherwise inactivate native IGF-1.

Mechanism as Understood in the Literature

Agonist at the IGF-1 receptor, the same receptor as native IGF-1. The practical difference is availability rather than signaling: reduced binding-protein affinity means more of the molecule remains free and active. IGF-1 receptor signaling influences cell proliferation, differentiation, and protein synthesis.

Research Status

There is a large clinical literature on native IGF-1, including an approved recombinant product (mecasermin) for severe primary IGF-1 deficiency. There is no comparable human clinical literature for the LR3 analogue, which exists primarily as a laboratory reagent. Research involving IGF-1 LR3 is overwhelmingly in vitro.

Regulatory status

Not FDA-approved for any indication. Recombinant native IGF-1 (mecasermin, brand name Increlex) is separately FDA-approved for a narrow pediatric indication; that approval does not extend to this analogue. Prohibited in competitive sport under World Anti-Doping Agency rules.

Commonly Confused With

Distinct from native IGF-1 and from mecasermin, the approved recombinant product. Also distinct from IGF-1 DES, another engineered variant. And distinct from MGF, which is a different splice variant of the same gene rather than a modified version of the mature hormone.

How This Compound Is Marketed

Vendor marketing for this compound typically references muscle growth, recovery, and body composition. VialReport does not evaluate or endorse these claims. See Research Status above for what the published literature actually establishes.

Analytical Profile

83 amino acids (70 native plus the 13-residue extension), molecular weight approximately 9111 Da. Substantially larger than most compounds in this library, and large enough that analytical characterization is closer to a protein workflow than a short-peptide one. The size difference from native IGF-1 (approximately 7649 Da) is large and unambiguous by mass. Intact mass can distinguish LR3 from native IGF-1, but does not on its own establish correct sequence, disulfide connectivity, folding, aggregation state, or biological activity.

Stability and Handling

Supplied lyophilized. Proteins of this size are more fragile than short peptides, with greater sensitivity to temperature excursions, freeze-thaw cycling, and surface adsorption once reconstituted. Published stability data may not apply to research-channel material.

Key Literature

  1. 01 Tomas FM, et al. Insulin-like growth factor-I (IGF-I) and especially IGF-I variants are anabolic in dexamethasone-treated rats. Biochem J. 1992;282:91-97.
  2. 02 Francis GL, 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;8:213-223.

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Published reports

Reports for IGF-1 LR3

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