ACE-031: The Myostatin Trap Tested in Early Human Trials
Last updated: March 2026
ACE-031 (ActRIIB-Fc) is a soluble decoy receptor designed to intercept myostatin, activin, and GDF-11 before they can suppress muscle growth. A Phase 2 trial in Duchenne muscular dystrophy showed trends toward increased lean mass — until vascular off-target effects forced an early stop.
🧪 View ACE-031 at Swiss Chems (research use only) →DMD Trial, Stopped Early
in Human Trials
Smad Pathway Inhibitor
How ACE-031 Works
ACE-031 is an engineered fusion protein combining the ligand-binding domain of ActRIIB with an IgG1 Fc region for extended half-life. It acts as a circulating decoy receptor, capturing myostatin and related TGF-β family members before they reach muscle tissue — effectively derepressing muscle growth signaling at the pathway level.
ACE-031 consists of the extracellular domain of activin receptor type IIB (ActRIIB) fused to a human IgG1 Fc region. Injected subcutaneously, it circulates in blood and binds target ligands with high affinity — acting as a soluble decoy that competes with cell-surface ActRIIB on muscle fibers. The Fc fusion extends plasma half-life, allowing injections spaced weeks apart.
Unlike antibodies targeting only myostatin (GDF-8), ACE-031 is built from the ActRIIB extracellular domain, and ActRIIB interacts with activin and multiple other ligands including myostatin, GDF-11 and BMP-9 (PMID: 28955765). The Phase 2 trial paper describes ACE-031 as binding "myostatin and related ligands" (PMID: 27462804). This broad capture is the proposed basis for its anabolic effect. BMP signaling helps maintain vascular homeostasis, and a newer modified ActRIIB-Fc trap has been engineered to spare BMP binding (PMID: 42422175), so BMP binding is a suspected — not proven — cause of ACE-031's vascular side effects.
Myostatin normally binds ActRIIB on muscle cells, activating the Smad2/3 signaling cascade, which suppresses protein synthesis and promotes atrophy. ACE-031 sequesters myostatin before receptor binding, effectively silencing Smad2/3 inhibition.
Follistatin is an endogenous binding protein that inhibits activins and myostatin through direct ligand sequestration. ACE-031 is receptor-based, but ActRIIB also interacts with activin (see above), so it is not free of activin-axis effects either.
What the Research Shows
Summary of the published human studies — a single-dose study in healthy volunteers (PMID: 23169607) and a Phase 2 trial in Duchenne muscular dystrophy that was stopped early (PMID: 27462804). Human trial data is from small cohorts — interpret with appropriate caution.
Side Effects & Risks
Key Takeaways
- Lean-mass increases reported at the top single dose in healthy volunteers; only trends in the Phase 2 DMD trial
- ActRIIB-based ligand trap: binds "myostatin and related ligands" (PMID 27462804); ActRIIB's ligands include activin, GDF-11 and BMP-9 (PMID 28955765)
- MRI-measured thigh muscle volume gains vs. placebo at the top single dose in healthy volunteers
- Mechanistically distinct from follistatin — receptor-based vs. binding-protein approach
- The Phase 2 DMD trial was stopped after its second dosing regimen over epistaxis and telangiectasia concerns
- The cause of the vascular effects is not established; off-target BMP binding is suspected, not proven
- No approved clinical indication; research-only compound
- Broad ligand binding means unpredictable systemic effects long-term
- Human data come from small trials, one stopped early
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This page is for educational and research purposes only. It is not medical advice. ACE-031 (ActRIIB-Fc) is not FDA approved for human use. The Phase 2 DMD trial was stopped early due to potential safety concerns of epistaxis and telangiectasia (PMID: 27462804). Vendor links point to material sold for laboratory research use only, not for human use. Research data cited is from small early-phase trials; treat all findings as preliminary. Always consult a qualified physician before considering any experimental compound.
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