ACE-031
A soluble decoy receptor fusion protein that sequesters myostatin and related muscle-suppressing ligands to release multiple brakes on muscle and bone growth at once.
ACE-031 is a fusion protein built from the extracellular domain of the activin type IIA receptor (ActRIIA) linked to a human IgG1 Fc region, developed by Acceleron Pharma. It acts as a soluble decoy that binds and neutralizes circulating myostatin, activin, and GDF-11, removing several negative regulators of muscle mass simultaneously. A Phase 2 trial in boys with Duchenne muscular dystrophy showed increases in lean body mass but was halted early due to vascular adverse events (epistaxis and telangiectasias), and the clinical program was discontinued. It has no FDA approval and is not commercially available.
Class
Recombinant ActRIIA-Fc fusion protein (soluble decoy receptor)
Half-life
~14 days
Routes
Subcutaneous, Intravenous
Category
Growth Hormone & Performance
Researched benefits
What it's studied for
Myostatin and activin inhibition
By acting as a soluble decoy receptor, ACE-031 binds and sequesters circulating myostatin, activin, and GDF-11, blocking their signaling through the Smad2/3 pathway that normally suppresses muscle growth. This simultaneous inhibition of multiple negative regulators is a distinguishing feature versus single-target myostatin blockers.
Increased lean muscle mass
Preclinical models of myopathy showed significant increases in lean mass after ActRIIA blockade, and a Phase 2 trial in boys with Duchenne muscular dystrophy demonstrated significant increases in lean body mass, supporting the mechanism in humans.
Improved bone density
In the Phase 1/2 Duchenne trial, subcutaneous ACE-031 showed trends toward increased bone mineral density alongside lean mass gains, consistent with the role of the ActRIIA/activin pathway in regulating bone as well as muscle.
Potential functional preservation in muscle wasting
The Duchenne trial showed trends toward maintaining 6-minute walk test distance, suggesting possible functional benefit in severe wasting conditions, though the study was discontinued before efficacy could be confirmed.
Mechanism
How it works
ACE-031 is engineered from the extracellular ligand-binding domain of the activin type IIA receptor (ActRIIA) fused to a human IgG1 Fc region. The Fc portion extends circulating half-life to roughly 14 days and allows the molecule to function as a stable, soluble decoy receptor in the bloodstream.
Myostatin (GDF-8), activin, and GDF-11 are members of the TGF-beta superfamily that normally bind the ActRIIA/ActRIIB receptors on muscle cells and activate the Smad2/3 signaling cascade. This signaling suppresses satellite cell activation and muscle protein synthesis, effectively acting as a brake on muscle growth. By competitively binding these circulating ligands before they reach cell-surface receptors, ACE-031 removes several of these brakes at once.
The result is disinhibition of muscle protein synthesis and satellite cell activity, producing increases in lean mass and bone density in preclinical and early clinical settings. However, the same pan-ActRIIA ligand blockade also inhibits TGF-beta family ligands involved in blood vessel homeostasis and angiogenesis. This off-target activity is believed to underlie the vascular adverse events (epistaxis, telangiectasias) observed in trials and represents an unresolved safety concern intrinsic to the mechanism.
Evidence
Research & clinical studies (1)
Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial
In a phase 1/2 randomized placebo-controlled trial in boys with Duchenne muscular dystrophy, subcutaneous ACE-031 showed trends toward maintaining 6-minute walk distance and increasing lean body mass and bone mineral density, but the study was discontinued early due to non-muscle-related safety signals including epistaxis and telangiectasias.
PMID 27462804Safety
Side effects & considerations
Commonly reported effects
Contraindications & cautions
- Cardiovascular disease
- Telangiectasia risk
- Bleeding disorders
- Pregnancy
ACE-031 carries a high-risk profile. The vascular adverse events that halted its clinical program are attributed to off-target inhibition of angiogenic TGF-beta family ligands and are considered inherent to pan-ActRIIA ligand blockade. It is not suitable for self-administration without professional oversight.
FAQ
ACE-031 — common questions
What is ACE-031?
ACE-031 is a soluble decoy receptor fusion protein made from the extracellular domain of the activin type IIA receptor (ActRIIA) linked to a human IgG1 Fc region, developed by Acceleron Pharma. It binds and sequesters myostatin, activin, and related TGF-beta superfamily ligands that suppress muscle mass, with the original goal of promoting muscle growth in severe wasting conditions like Duchenne muscular dystrophy.
What is ACE-031 primarily studied for?
It has been studied for myostatin/activin inhibition, increasing muscle mass, and improving bone density, primarily in the context of muscle-wasting diseases such as Duchenne muscular dystrophy.
How does ACE-031 work?
It acts as a decoy receptor that binds circulating myostatin, activin, and GDF-11 before they can reach cell-surface receptors, reducing signaling through the Smad2/3 pathway that normally suppresses satellite cell activation and muscle protein synthesis. Removing these multiple brakes simultaneously promotes lean mass and bone growth.
What are the side effects of ACE-031?
Reported adverse events and considerations include epistaxis (nosebleeds) and telangiectasias (dilated blood vessels), which led to early termination of its Phase 2 trial. Contraindications include cardiovascular disease, bleeding disorders, telangiectasia risk, and pregnancy.
Why was ACE-031 development discontinued?
Its Phase 2 trial in boys with Duchenne muscular dystrophy was halted in 2013 due to vascular-related adverse events attributed to off-target inhibition of angiogenic TGF-beta family ligands, and Acceleron subsequently discontinued the clinical program.
Is ACE-031 approved or available?
No. ACE-031 has no FDA approval, is not approved for any indication, and is not commercially available. It remains an investigational compound with an unresolved vascular safety concern.
What did the clinical research show?
In the phase 1/2 randomized placebo-controlled trial, subcutaneous ACE-031 showed trends toward maintaining 6-minute walk test distance and increasing lean body mass and bone mineral density, but the study was discontinued early due to non-muscle-related safety signals including epistaxis and telangiectasias.
