ACE-031 is a peptide that is considered a soluble form of activin type IIB receptors that are linked to the domain of IgG1 Fc. ACE-031 is best known for its ability to increase muscle mass regardless of the type of muscle fibers present. ACE-031 works to block the inhibition of muscle growth. The peptide is known to bind to myostatin and other similar ligands that limit muscle and protein synthesis. Numerous studies show that in cases of muscular dystrophy, muscular degeneration, or muscular injury, myostatin deficiency is actually beneficial to the subject due to myostatin’s ability to inhibit muscle growth. In mice subjects that experienced a myostatin deficiency, hypertrophic and hyperplastic muscle growth increased by 200-300%.