Soluble activin receptor type IIB decoy
ACE-031
Trial Discontinued development
What it is
ACE-031 is a recombinant fusion protein built from the extracellular domain of activin receptor type IIB linked to an antibody Fc region. It works as a soluble decoy that soaks up myostatin and related ligands before they can signal. It is included here because it is often discussed alongside peptides, but it is a much larger engineered protein, not a synthetic short peptide.
Benefits in plain language
What researchers and reference users usually mean when they talk about this compound. These are study themes and common claims — not a promise that it will do this in you.
- This is the “myostatin blocker” people reference when they talk about drug-driven muscle growth.
- Myostatin is a natural brake on muscle size; the idea is to remove the brake rather than press the gas.
- It was tested in boys with Duchenne muscular dystrophy, where trials showed changes in lean mass but also worrying side effects.
- Development was discontinued, so most online claims outrun what was ever shown in humans.
If a branded, FDA-approved product exists, that label is the only dose that is actually authorized. Research-chemical vials are a different object.
Mechanism of action
ACE-031 binds circulating myostatin, GDF-11, and related TGF-β superfamily ligands, preventing them from engaging ActRIIB receptors on muscle. Removing that brake permits greater muscle protein synthesis and fiber growth in animal models. The same pathway touches vascular and epithelial tissue, which is where the safety concerns came from.
Possible side effects / caveats
The Duchenne trial reported nosebleeds and gum bleeding (telangiectasia) attributed to effects on vascular integrity, plus changes in bone-turnover markers. Development was stopped in 2013. There is no established human dose, no approved product, and material circulating as “ACE-031” is unlikely to be the actual clinical candidate.
Protocol ranges
| Source tier | Amount | Frequency / duration | Notes |
|---|---|---|---|
| Trial | 0.5–3 mg/kg | Single or repeated SC dosing in phase 1/2 | Weight-based, supervised; program discontinued |
| Cited range | No accepted community protocol | — | Material rarely authentic; claims unreliable |