Long-acting synthetic analog of insulin-like growth factor 1 (IGF-1)
IGF-1 LR3 is a modified, long-acting version of IGF-1 designed to stay active in the body far longer than natural IGF-1.
| Class / type | Long-acting synthetic analog of insulin-like growth factor 1 (IGF-1) |
|---|---|
| Category | Growth Hormone & Muscle |
| Status (Jul 2026) | Research use only |
An 83-amino-acid analog with an N-terminal extension and an Arg substitution at position 3 that greatly reduces binding to IGF-binding proteins, extending half-life to roughly 20-30 hours and increasing free bioavailability at the IGF-1 receptor to drive cell growth and protein synthesis.
Used in laboratory cell-culture research; promoted anecdotally for muscle growth and recovery, but with no published human clinical trials of the analog itself.
Long duration of action, potent stimulation of cell proliferation and protein synthesis in research settings.
Hypoglycemia, organ and tissue overgrowth, potential to promote tumor growth, and no human safety data; FDA has issued warning letters against marketing it as a supplement.
Users report muscle-growth and recovery effects and localized pumps; anecdotal sentiment only, not a medical endorsement.
NOT FDA-approved. It is sold as a research reagent only, has no approved human use, and is banned by WADA at all times under class S2.2 (Growth Factors).