What Is IGF-1 LR3? A Research Overview

IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a synthetic, long-acting analog of native IGF-1 used as a reference compound in laboratory growth-factor and IGF-receptor research. It differs from native IGF-1 by an arginine substitution at position 3 (Arg3) and a 13-amino-acid N-terminal extension, modifications that sharply reduce its binding to IGF-binding proteins (IGFBPs) and extend its half-life in experimental systems. IGF-1 LR3 is sold strictly for research use only (RUO). It is not a drug, is not FDA-approved, and is not intended for human or veterinary use. These statements have not been evaluated by the Food and Drug Administration.

Quick facts

• Class: long-acting IGF-1 analog (Arg3 substitution + 13-amino-acid N-terminal extension)
• Research focus: growth-factor and IGF-receptor signaling research; serum-free cell-culture studies
• Form: lyophilized powder, ≥99% HPLC purity, third-party tested
• Status: research use only — not for human or animal use; not FDA-approved

What is IGF-1 LR3?

Native IGF-1 is a 70-amino-acid polypeptide central to studies of cell growth and metabolic signaling. IGF-1 LR3 is an engineered variant designed for laboratory work. Two structural changes define it: the glutamic acid at position 3 is replaced with arginine (the “R3” designation), and a 13-amino-acid extension is added to the N-terminus (the “Long” designation). Together these modifications produce a molecule that behaves differently from native IGF-1 in experimental systems — chiefly by largely escaping the IGFBP family of carrier proteins that normally sequester circulating IGF-1.

What does the research show?

Published preclinical and in-vitro studies have characterized how IGF-1 LR3 behaves in laboratory models. In serum-free culture of human embryonic kidney (HEK293) cells, Long R3 IGF-I supported cell growth and survival at concentrations far lower than insulin and acted as a more potent growth and survival factor than either insulin or native IGF-I, activating the type I IGF receptor in a dose-responsive manner [1]. In in-vitro–produced bovine embryos, long R3 IGF-I and native IGF-I differentially affected early development and the messenger-RNA abundance of IGF-binding proteins and type I IGF receptors — the two molecules showing distinct regulatory patterns [2]. A review of IGF-1 biology notes that the LR3 modifications confer much lower affinity for IGFBPs, a significantly longer half-life, and increased potency relative to wild-type IGF-1 in laboratory measures [3]. These findings describe behavior observed only in cell-culture and animal-research settings.

Mechanisms studied in the lab

• IGF-1 receptor signaling: in experimental systems, IGF-1 LR3 binds and activates the type I IGF receptor (IGF-1R), the entry point for IGF-1 signaling studied in cell models [1].
• Reduced IGFBP binding and extended half-life: the Arg3 substitution and N-terminal extension markedly lower affinity for IGF-binding proteins, so less of the molecule is sequestered by carrier proteins — a property associated with its longer measured half-life in research models [3].

Research status and safety

IGF-1 LR3 is offered exclusively as a research chemical for research use only. It is not a dietary supplement, not a medicine, and not approved by the FDA for any therapeutic indication. It is not intended for human or veterinary use, and nothing here should be interpreted as a recommendation to administer it to people or animals. These statements have not been evaluated by the Food and Drug Administration.

Handling

IGF-1 LR3 is supplied as a lyophilized (freeze-dried) powder, typically kept cold and protected from light and moisture until a study calls for it to be brought into solution. For general laboratory background, see our guide on how to reconstitute a research peptide, and browse related reference compounds in the catalog. Product details for this item are available here: IGF-1 LR3 — research-grade, ≥99% pure.

FAQ

How is IGF-1 LR3 different from native IGF-1? IGF-1 LR3 carries an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. These changes give it much lower affinity for IGF-binding proteins and a longer half-life in laboratory models, whereas native IGF-1 binds IGFBPs strongly and is largely carrier-bound in circulation.

What is IGF-1 LR3 used for? In documented use it is a reference reagent for in-vitro and preclinical growth-factor and IGF-receptor research, including serum-free cell-culture studies. It is for research use only and is not for human or animal use.

Is IGF-1 LR3 approved by the FDA? No. It is not FDA-approved and is not intended for human or veterinary use. It is sold strictly as a research chemical.

References

1. Voorhamme D, Yandell CA. LONG R3IGF-I in serum-free culture of HEK293 cells. Mol Biotechnol. 2006.
2. Prelle K, et al. IGF-I and long R3 IGF-I in bovine embryos. Endocrinology. 2001.
3. Bailes J, Soloviev M. Insulin-Like Growth Factor-1 (IGF-1) (review). Biomolecules. 2021.

For research use only. Not for human or veterinary use. Not FDA-approved. Statements have not been evaluated by the FDA.