Peptides

ACE-031 is a synthetic protein made up of activin receptor type IIB and the immunoglobulin G1-Fc (IgG1-Fc). It binds to myostatin and related proteins within muscle, rendering them inactive. Research shows it to be useful in stabilizing muscle mass and strength in both primary muscle-wasting disorders and neuromuscular conditions.

Dermorphin is a peptide, which is about 30–40 times more potent than morphine but theoretically may be less likely to produce drug tolerance and addiction (due to its high potency)