IGF-1Lr3 1MG is a 1-milligram format of Long R3 IGF-1, a modified insulin-like growth factor 1 analogue used in laboratory research. It features an Arg3 substitution and an N-terminal extension that researchers study for altered receptor binding and reduced interaction with IGF binding proteins. Studies have examined IGF-1Lr3 in cell culture work involving growth-factor signaling and metabolism-related pathways.