IGF-1 LR3, also known as Insulin-like Growth Factor 1 Long R3, is a synthetic analog of human IGF-1. It is engineered to have an extended half-life and increased potency compared to native IGF-1. The modification involves the substitution of arginine for glutamic acid at position 3 and the addition of 13 amino acids to the N-terminus, resulting in a 83-amino acid peptide. Researchers synthesize IGF-1 LR3 using recombinant DNA technology, typically in E. coli expression systems. IGF-1 LR3 is primarily studied in the context of muscle growth and repair, as well as its potential role in metabolic regulation. Researchers have observed that IGF-1 LR3 can stimulate muscle cell proliferation and differentiation, making it of interest in muscle-wasting conditions and athletic performance enhancement. Additionally, its effects on glucose metabolism and insulin sensitivity are under investigation. The mechanism of action of IGF-1 LR3 involves binding to the IGF-1 receptor with high affinity, initiating intracellular signaling cascades such as the PI3K/Akt and MAPK pathways. These pathways are crucial for cellular growth, survival, and metabolism. IGF-1 LR3's pharmacokinetic properties are characterized by a significantly extended half-life compared to native IGF-1, due to reduced binding to IGF-binding proteins. Researchers have reported a half-life of approximately 20-30 hours, allowing for less frequent administration in experimental settings. The compound is stable under physiological conditions, with bioavailability dependent on the route of administration. Current research on IGF-1 LR3 is focused on its therapeutic potential in muscle-wasting diseases and metabolic disorders. However, it is not approved for clinical use by major regulatory agencies, and its use is restricted to research settings. The compound's regulatory status varies by country, and it is often considered a research chemical with limited legal clarity for non-research applications.