I have no idea what it is.
Sounds a bit like Cartman's 'Weight gain 2000' from Southpark.
It looks like you are looking for a magic 'pill' to make muscle, and there isn't one.
There are no myostatin inhibitors that are available commercially.
There is one monoclonal antibody that is in clinical trials, other than that...............
Stop wasting your money on useless supplements and buy more proper food.