ACE-031
Recombinant ActRIIB-Fc fusion protein that binds myostatin and related TGF-β superfamily ligands
- Class
- Myostatin inhibitor
- Half-life
- 10–15 days
- Route
- Subcutaneous (SubQ)
- Cadence
- Weekly
- Evidence
- Human clinical trials
Overview
ACE-031 is a large recombinant fusion protein — not a short-chain peptide — designed to trap myostatin and related muscle-limiting signals before they ever reach your cells. It's the extracellular domain of the activin type IIB receptor fused to the Fc portion of an antibody, creating a soluble decoy that intercepts myostatin, activin A, and several other TGF-β family ligands that naturally put a brake on muscle growth. Single dose in healthy postmenopausal women produced a 3.3% gain in lean mass and 5.1% increase in thigh muscle volume within 29 days — gains comparable to months of strength training, but from one injection.
The compound advanced into Phase 2 trials for Duchenne muscular dystrophy (DMD) after showing those muscle-building effects in healthy adults. Trends favored the drug — maintained walking distance, increased lean mass, better bone density — but the trials were halted in 2013 after participants developed nosebleeds, gum bleeding, and small dilated blood vessels in the skin (telangiectasias). None of these were serious on their own, but Acceleron Pharma and Shire discontinued all human trials to investigate the vascular mechanism. Development never resumed.
The catch is twofold. First, ACE-031 doesn't just block myostatin — it also traps activin A, GDF-11, and several bone morphogenetic proteins (BMPs), including BMP9 and BMP10, which regulate blood vessel development. That broad ligand-binding profile is why the vascular side effects emerged. Second, the research-market material sold as ACE-031 is almost never the real thing — a 2025 study tested 14 black-market products and found zero contained the actual ActRIIB-Fc fusion protein used in trials.
Safety considerations
A few of the safety signals worth knowing — the full list, with dosing context and what to monitor, is inside AIx Core.
- Not approved anywhere. Clinical development was discontinued in 2013 after vascular adverse events (epistaxis, telangiectasias) emerged in DMD trials. The events resolved after stopping, but the mechanism was never fully clarified.
- The vascular side effects are thought to be caused by off-target inhibition of BMP9/BMP10, which regulate blood vessel maintenance. This is a structural risk of any broad-spectrum ActRIIB decoy — not something you can dose around.
- A 2025 anti-doping study (Reichel) tested 14 black-market ACE-031 products and found zero contained the actual ActRIIB-Fc fusion protein. Most research-market material sold as ACE-031 is likely mislabeled or counterfeit — it's a complex recombinant protein that requires mammalian cell expression, not something produced by typical peptide synthesis labs.
+ 3 more safety notes inside AIx Core →
Commonly monitored
Markers and signals people track when researching ACE-031.
- Lean body mass and thigh muscle volume (DXA or MRI)
- Nosebleeds, gum bleeding, or visible telangiectasias (small red spots on skin)
- Blood pressure — vascular effects may manifest as hypertension
- Bone mineral density (secondary effect observed in trials)
- Hematocrit and hemoglobin — anabolic compounds can elevate these
Frequently asked questions
What is ACE-031?
Recombinant ActRIIB-Fc fusion protein that binds myostatin and related TGF-β superfamily ligands. ACE-031 is a large recombinant fusion protein — not a short-chain peptide — designed to trap myostatin and related muscle-limiting signals before they ever reach your cells. It's the extracellular domain of the activin type IIB receptor fused to the Fc portion of an antibody, creating a soluble decoy that intercepts myostatin, activin A, and several other TGF-β family ligands that naturally put a brake on muscle growth. Single dose in healthy postmenopausal women produced a 3.3% gain in lean mass and 5.1% increase in thigh muscle volume within 29 days — gains comparable to months of strength training, but from one injection.
How is ACE-031 administered?
Subcutaneous (SubQ), typically weekly.
What is the half-life of ACE-031?
10–15 days — Long half-life supports infrequent dosing; takes weeks to clear after stopping.
Is ACE-031 approved for human use?
ACE-031 is investigational — not approved by the FDA, EMA, or MHRA for human use at the time of writing.
What does the evidence show for ACE-031?
Evidence tier: Human clinical trials. Attie 2013 (Phase 1, healthy postmenopausal women, n=48): single subcutaneous dose of 3 mg/kg produced 3.3% increase in total lean body mass (p=0.03, DXA) and 5.1% increase in thigh muscle volume (p=0.03, MRI) by day 29. Half-life 10–15 days.
What is commonly monitored when researching ACE-031?
Commonly tracked markers + signals: Lean body mass and thigh muscle volume (DXA or MRI), Nosebleeds, gum bleeding, or visible telangiectasias (small red spots on skin), Blood pressure — vascular effects may manifest as hypertension, Bone mineral density (secondary effect observed in trials), Hematocrit and hemoglobin — anabolic compounds can elevate these.
Open this in AIx Core for the full picture
Mechanism breakdown, receptor pathway diagram, full safety list, monitored items, source citations, and one-tap add-to-protocol. Free with any account.