PEG-MGF is mechano growth factor with polyethylene glycol chains attached, a standard pharmaceutical technique for slowing the breakdown of a molecule and extending how long it lasts in the body. The modification is legitimate chemistry. What it modifies is a compound that has never been tested in a human trial, so the result is a longer-acting version of something whose effects in people are unknown. There is no development programme and no published human study. It is prohibited in tested sport under the category covering mechano growth factors, and the pegylation does not change any of that.