IGF-1 LR3 (Long Arginine 3-IGF-1) is a synthetic, potent analog of natural Insulin-Like Growth Factor 1 (IGF-1), modified with extra amino acids for increased biological activity and a significantly longer half-life, making it more stable and effective than native IGF-1 for promoting cell growth and protein synthesis, often used in research (like stem cell maintenance) and controversially in bodybuilding for muscle enhancement, but is a banned performance-enhancing substance by WADA.