Decoy Receptors: A Different Strategy

ACE-031 takes an indirect approach to blocking myostatin: rather than occupying the myostatin receptor, it floats freely as a decoy, binding myostatin itself so the muscle receptor never sees it. The Fc domain extends its half-life, giving the decoy time to work.

It's an elegant design, but early clinical trials were paused over safety signals — a reminder that broad TGF-beta family inhibition affects more than just muscle. The ActRIIB receptor also regulates other ligands like activin and GDF-11, so neutralizing it has systemic consequences. Members discuss it as a cautionary case in target breadth: the more ligands you trap, the more off-target risk you accept.