IGF-1 LR3
Long-acting IGF-1 analog with ~20-hour half-life versus native IGF-1’s ~10 minutes. Not equivalent to approved mecasermin. WADA-prohibited. Significant oncological safety considerations require prominent acknowledgment in any research context.
IGF-1 LR3 (Insulin-Like Growth Factor-1 Long R3) is a recombinant analog of native human IGF-1, modified by addition of a 13-amino acid N-terminal extension and arginine substitution at position 3. These modifications significantly reduce binding to IGF binding proteins (IGFBPs), extending the half-life from ~10 minutes to ~20 hours.
IGF-1 LR3 should not be confused with FDA-approved mecasermin (Increlex) — approved for growth failure in children with severe primary IGF-1 deficiency. The LR3 modification makes it pharmacologically distinct from both native IGF-1 and mecasermin. It is used as a research compound with no established clinical dosing standard.
The same mechanism that drives anabolic research interest also raises significant oncological safety considerations. IGF-1 signaling has established roles in cancer cell proliferation and tumor growth. This is not a minor consideration — it should factor prominently into any research context involving IGF-axis compounds.
What are you researching?
Tell us your focus area and we’ll send a personalized research guide.
IGF-1 LR3 is not approved for any indication and is WADA-prohibited. The oncological safety concern is significant and established — IGF-1 pathway activation promotes cancer cell proliferation. Research use only. Community-derived bodybuilding protocols are not clinical standards. All information for educational reference only — approach with substantial caution.