ACE-031
Also known as: ACVR2B-Fc, ActRIIB-Fc
Myostatin Inhibitor | Experimental Muscle Growth
Overview
ACE-031 is a soluble form of the activin type IIB receptor (ActRIIB) fused to an IgG1 Fc domain. It functions as a decoy receptor, binding and neutralizing myostatin and other TGF-beta superfamily members that normally limit muscle growth. Originally developed by Acceleron Pharma for Duchenne muscular dystrophy (DMD), ACE-031 reached Phase 2 clinical trials before development was halted due to vascular side effects including nosebleeds and telangiectasia. In healthy volunteers, a single dose produced significant increases in lean mass and reductions in fat mass within 29 days.
Key benefits
- Significant lean mass increases (up to 1.7% in 29 days) observed in Phase 1 trials
- Simultaneous reduction in fat mass alongside muscle gains
- Long half-life (12-15 days) allows infrequent dosing
- Broad TGF-beta ligand neutralization for robust anti-catabolic effects
- Dose-dependent increases in thigh muscle volume confirmed by MRI
Mechanism of action
ACE-031 acts as a ligand trap for members of the TGF-beta superfamily. By mimicking the extracellular domain of the ActRIIB receptor, it intercepts myostatin (GDF-8), activin A, activin B, and GDF-11 before they can bind cell-surface receptors and activate Smad2/3 signaling. Blocking this pathway removes the natural brake on muscle protein synthesis and satellite cell proliferation, resulting in rapid skeletal muscle hypertrophy. The Fc fusion domain extends circulating half-life through FcRn-mediated recycling and provides bivalent ligand binding.
Molecular data
- Type
- Soluble activin receptor type IIB-Fc fusion protein
- Half-life
- 12-15 days
Indications
What the research community uses this compound for, with self-reported effectiveness.
Muscle Growth
Body Composition
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Delivery method
| Protocol | Dose | Frequency | Duration |
|---|---|---|---|
| — | 0.1-3 mg/kg | Single IV dose | — |
| — | 0.5-2.5 mg/kg | Every 2 weeks | — |
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Nosebleeds (epistaxis) - most frequently reported adverse event
- Gum bleeding
- Telangiectasia (dilated small blood vessels visible on skin)
- Skin erythema (redness)
- Minor injection site reactions
Contraindications
- NEVER approved for human use - clinical development discontinued
- History of bleeding disorders or vascular malformations
- Concurrent anticoagulant or antiplatelet therapy
- Known hypersensitivity to Fc fusion proteins
- Pregnancy or breastfeeding
Monitoring
- Watch for any signs of bleeding, especially nasal and gingival
- Regular skin examination for new telangiectasia
- Complete blood count to monitor for anemia from chronic bleeding
- Blood pressure monitoring
References
Primary literature and clinical-trial data informing this entry.