Performance · Research Phase
IGF-1 LR3 (Long-Arg3)
No lawful US pathway
01 · Overview
IGF-1 LR3 is a synthetic analogue of insulin-like growth factor 1 with a 13-amino-acid N-terminal extension and arginine substituted for glutamate at position 3 (PMID 1378742). These modifications sharply reduce binding to IGF-binding proteins, which increases potency in cells that secrete binding proteins even though the analogue is cleared from the circulation faster than native IGF-1 (PMID 1378742, PMID 7693845).
In rats, the analogue promoted body weight gain, visceral organ growth and anti-catabolic effects more potently than IGF-1, and in pigs and marmosets it produced more prolonged lowering of blood glucose (PMID 8708565, PMID 9415072). IGF-1 LR3 is not approved for human use and is sold as a research reagent, although it is also found as a black market product used in bodybuilding (PMID 33587816).
02 · Research summary & key findings
No clinical trials of IGF-1 LR3 for safety or efficacy in humans have been published, it has never been approved for human use, and it is prohibited in sport (PMID 33587816, PMID 42395176). The evidence for anabolic and metabolic activity comes from cell culture and animal studies (PMID 1378742, PMID 8708565, PMID 9415072). Products sold through the black market have been shown to contain impure material, including a His-tagged form intended for laboratory work whose effects in humans have never been studied, and oxidized degradation forms (PMID 20675162, PMID 33587816).
03 · Regulatory status
IGF-1 LR3 (Long-Arg3) is in the research phase with limited clinical data in humans. Current evidence is primarily derived from preclinical (animal or in vitro) studies.
No lawful pathway today
IGF-1 LR3 (Long-Arg3) is not FDA-approved and does not currently have a lawful prescription or compounding pathway in the United States, so we do not sell it and will not book a consultation for it. That can change: in 2026 FDA began reviewing several peptides for compounding. If you are working on the goal it is studied for, a licensed clinician can tell you what is lawfully available, which may be something else.
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Looking for a lawful, clinician-prescribed option for athletic performance?
IGF-1 LR3 (Long-Arg3) is a research compound, is not FDA-approved, and has no lawful US compounding pathway, so we do not offer it and no clinician we work with will prescribe it. Products sold online as “research chemicals” are not made or tested to the standards required of medicines. If you are working on athletic performance, a licensed clinician can tell you at a free consultation whether an FDA-approved or lawfully compounded treatment fits you, or whether nothing does.
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04 · Administration routes
- Subcutaneous injection
References
- [1]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. PMID 1378742
- [2]Detection of His-tagged Long-R³-IGF-I in a black market product Growth Horm IGF Res, 2010. PMID 20675162
- [3]Detection of LongR(3) -IGF-I, Des(1-3)-IGF-I, and R(3) -IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes Drug Test Anal, 2021. PMID 33587816
- [4]The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration Front Endocrinol (Lausanne), 2026. PMID 42395176
- [5]Plasma clearance and tissue distribution of labelled insulin-like growth factor-I (IGF-I) and an analogue LR3IGF-I in pregnant rats J Endocrinol, 1993. PMID 7693845
- [6]Superior potency of infused IGF-I analogues which bind poorly to IGF-binding proteins is maintained when administered by injection J Endocrinol, 1996. PMID 8708565
- [7]IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys J Endocrinol, 1997. PMID 9415072
Primary literature
- PubMed: "IGF-1 LR3"
Peer-reviewed literature indexed by the National Library of Medicine.
- ClinicalTrials.gov: "IGF-1 LR3"
Registered interventional and observational studies, including status and phase.
- PubChem: "IGF-1 LR3"
Chemical structure, molecular properties, and bioactivity data.
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