Modified version of IGF-1 (13 amino acids added and a change at position 3) created for cell cultures. Sold on the black market for muscle gain, but there are no human studies.
Regulatory status
Not approved
Family
Long-acting synthetic IGF-1 analog
Scientific evidence
Low
Number of findings
2
Where it acts
Bones and muscles · Hormones and metabolism
Also known as
IGF-1 LR3, Long R3 IGF-I, LR3-IGF-1
Regulatory status
FDA (US): Not approved. The only approved IGF-1 is mecasermin (Increlex), for severe primary IGF-1 deficiency in children.
EMA (EU): Not approved
Dose
There is no established dose in humans.
Safety
No human data. Theoretical risks: hypoglycemia and stimulation of tissue growth (concern about tumors, plausible but not shown). Black-market vials have been found with laboratory versions not intended for injection. Banned in sport. Its use only makes sense in research or under medical supervision; buying it is not recommended.
Effect by goal · level of evidence
Adulterated black-market product
worsensLowobservational (A)animals / laboratory
One black-market vial contained a version with a histidine "tag," typical of laboratory reagents, whose effects in humans have never been studied.
A 2026 review concludes that the benefits on performance and body composition are very uncertain and that the concern about mitogenic effects is plausible but unproven.
Changes to its structure keep it from binding to IGF-1 carrier proteins, so it lasts longer and acts more strongly on the IGF-1 receptor, which stimulates the growth of muscle and other tissues.
What the evidence says
In people
Benefit in humans not demonstrated. A 2026 review concludes that the benefits for performance and body composition are very uncertain and that concern about mitogenic effects is plausible but unproven. PubMed 42395176
In animals or the laboratory
Adulterated black-market product. A black-market vial contained a version with a histidine “tag,” typical of laboratory reagents, whose effects in humans have never been studied. PubMed 20675162