IGF-1 LR3
Status
No approved product. No FDA-approved labeling exists. Not an approved medicine; it is manufactured and sold as a laboratory reagent rather than for administration to people.
What it is
A long-acting IGF-1 variant studied in cell and animal models.
What published research measured
An 83-amino-acid analogue of IGF-1 carrying an arginine substitution at position 3 and a 13-residue N-terminal extension. Both modifications reduce its binding to the IGF binding proteins that normally sequester circulating IGF-1, so a far larger fraction stays free and active and its effective duration is much longer than native IGF-1. Its main documented use is as a cell-culture reagent in bioprocessing, where it is valued precisely because it is hard for a cell system to switch off. There are no human clinical trials of IGF-1 LR3 for muscle, performance or any other indication. Because it bypasses the binding-protein brake, the safety questions that attach to sustained IGF-1 receptor signalling — including effects on blood glucose and the theoretical concern about promoting growth of existing neoplastic tissue — apply without the physiological buffering that limits native IGF-1. Prohibited at all times in sport under WADA class S2.
Source
Frontiers in Endocrinology 2026 review — performance-enhancing peptides modulating the GH–IGF-1 axis · WADA Prohibited List, class S2
Sources
No linked primary source is on file for this entry yet.
Educational use only, never medical advice. No doses.