IGF-1 LR3

Mechanism

In plain terms, it is a lab-made version of a natural growth factor, altered so it stays active longer and works more strongly on cells. Technically, Long R3 IGF-1 carries an arginine substitution at position 3 and a 13-amino-acid N-terminal extension; these changes markedly reduce its affinity for IGF-binding proteins, leaving more free peptide available to activate the IGF-1 receptor (a receptor tyrosine kinase) and downstream PI3K/Akt and MAPK signalling that drive cell proliferation and protein synthesis. This pharmacology is characterised in cell and animal systems, not in approved human therapeutics.

Regulatory Status by Region

• United States (FDA)Not approved for any human use; marketed as a research-use-only reagent, not for human administration. It is a distinct molecule from the approved recombinant human IGF-1 drug mecasermin (Increlex).
• Australia (TGA)Not on the Australian Register of Therapeutic Goods (ARTG); an unapproved substance with no registered therapeutic product.
• European Union (EMA)No EMA marketing authorisation; not an approved medicine in the EU.
• WADAProhibited at all times under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics); insulin-like growth factor-1 (IGF-1) and its analogues are explicitly covered.

See the full regulatory status matrix

Key Studies

• 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 (Francis et al.) (opens in a new tab) (J Mol Endocrinol 1992;8(3):213-223; DOI 10.1677/jme.0.0080213; PMID 1378742)
• Superior potency of infused IGF-I analogues which bind poorly to IGF-binding proteins is maintained when administered by injection (Tomas et al.) (opens in a new tab) (J Endocrinol 1996;150(1):77-84; DOI 10.1677/joe.0.1500077; PMID 8708565)

Common Questions

What is IGF-1 LR3?

IGF-1 LR3 (Long R3 IGF-1) is a chemically modified, longer-acting analogue of insulin-like growth factor-1 that is sold as a laboratory research reagent for cell culture, not as a medicine. It is not approved for human use by any regulator, and as an IGF-1 analogue it is prohibited in sport by WADA at all times. It is distinct from mecasermin, the approved recombinant human IGF-1 medicine.

Is IGF-1 LR3 approved for medical use?

IGF-1 LR3 is not approved for medical use and is prohibited in one or more regulatory or anti-doping frameworks. United States (FDA): Not approved for any human use; marketed as a research-use-only reagent, not for human administration. It is a distinct molecule from the approved recombinant human IGF-1 drug mecasermin (Increlex). European Union (EMA): No EMA marketing authorisation; not an approved medicine in the EU. Australia (TGA): Not on the Australian Register of Therapeutic Goods (ARTG); an unapproved substance with no registered therapeutic product.

How does IGF-1 LR3 work?

In plain terms, it is a lab-made version of a natural growth factor, altered so it stays active longer and works more strongly on cells. Technically, Long R3 IGF-1 carries an arginine substitution at position 3 and a 13-amino-acid N-terminal extension; these changes markedly reduce its affinity for IGF-binding proteins, leaving more free peptide available to activate the IGF-1 receptor (a receptor tyrosine kinase) and downstream PI3K/Akt and MAPK signalling that drive cell proliferation and protein synthesis.

Is IGF-1 LR3 legal in Australia?

IGF-1 LR3 in Australia (TGA): Not on the Australian Register of Therapeutic Goods (ARTG); an unapproved substance with no registered therapeutic product.

Is IGF-1 LR3 banned in sport?

IGF-1 LR3 under the World Anti-Doping Agency (WADA) code: Prohibited at all times under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics); insulin-like growth factor-1 (IGF-1) and its analogues are explicitly covered.