PEG-MGF is the Pegylated form of MGF (Mechano Growth Factor). MGF is a splice variant of IGF-1, which has been shown in vitro as well as in vivo to induce growth and hypertrophy in mechanically stimulated or damaged muscle. This is a process required for growth of adult muscle. Natural MGF is made locally and does not travel into the bloodstream. Synthetic MGF is water based and when administered intramuscularly, travels into the bloodstream. MGF is only stable in the blood stream for only a few minutes.

PEGylation is the act of attaching a Polyethylene glycol (PEG) structure to another larger molecule (in this case, MGF). The PEG acts as a protective coating and the theory here is that this will allow the MGF to be carried through the blood stream without being broken down. Insulin-like growth factor genes appear to have evolved from a single insulin-like gene. This gene can be detected in invertebrates and seems to cause anti-apoptotic effects by maintaining terminally differentiated cells. MGF contains the core protein encoded by the exons 3 and 4, as well as a specific insert encoded by a region of exon 5.