ACE-031
ACE-031 (Myostatin Inhibitor)
ACE-031 is a recombinant fusion protein consisting of the extracellular domain of activin receptor type IIB (ActRIIB) linked to a human IgG1 Fc region, designed to inhibit myostatin and related TGF-beta family ligands that suppress muscle growth. It was developed by Acceleron Pharma primarily for treating muscle-wasting diseases such as Duchenne muscular dystrophy and other neuromuscular conditions. In research and performance contexts, it is investigated for its potent anabolic effects on skeletal muscle mass and strength.
Mechanism of Action
ACE-031 acts as a decoy receptor by binding and neutralizing myostatin (GDF-8), activin A, GDF-11, and other TGF-beta superfamily ligands before they can engage endogenous ActRIIB receptors on muscle cells, thereby removing a major inhibitory brake on muscle protein synthesis and satellite cell activation. By blocking ActRIIB signaling, ACE-031 disinhibits downstream anabolic pathways including Akt/mTOR and suppresses SMAD2/3 phosphorylation, resulting in net increases in muscle fiber hypertrophy and hyperplasia. This mechanism is broader than selective myostatin antibodies because it captures multiple ligands simultaneously, producing more pronounced muscle and potentially bone effects.
Evidence by Health Goal(4 goals)
Dosing Protocols
Subcutaneous injection, typically in the abdomen or thigh, at any time of day
Cycle: Clinical trials used 3-month treatment periods; research use often mirrors this with periodic reassessment
Dosing is weight-based. Clinical trials in DMD patients used doses ranging from 0.1 to 3 mg/kg subcutaneously every 4 weeks. Higher doses (>1 mg/kg) produced significant muscle mass increases but were associated with increased adverse events including telangiectasias and epistaxis. Research-use dosing in healthy individuals lacks robust safety data.
Safety & Side Effects
ACE-031's Phase 2 clinical trials in Duchenne muscular dystrophy were halted early due to a higher-than-expected incidence of cutaneous and mucosal vascular side effects (telangiectasias, nosebleeds, gum bleeding), indicating that off-target inhibition of vascular-regulatory TGF-beta ligands poses meaningful safety risks; it is not approved for any indication by any regulatory authority, making its use outside of supervised clinical trials unapproved and legally restricted in most jurisdictions.
Possible Side Effects
- !Cutaneous telangiectasias (dilated small blood vessels visible on skin) - dose-dependent, reported in majority of higher-dose subjects
- !Epistaxis (nosebleeds) - likely due to off-target inhibition of activin and BMP signaling in vascular endothelium
- !Gingival bleeding and gum hyperpigmentation
- !Injection site erythema, swelling, and mild pain
- !Facial flushing and erythema
- !Headache in the days following injection
- !Potential suppression of follicle-stimulating hormone (FSH) and reproductive axis due to activin A inhibition
- !Possible alterations in bone metabolism and remodeling due to BMP pathway inhibition
Interactions
- -Anticoagulants (warfarin, heparin, NOACs) - ACE-031 increases bleeding risk; concurrent use may significantly amplify hemorrhagic complications
- -Antiplatelet agents (aspirin, clopidogrel) - additive mucosal and vascular bleeding risk reported in preclinical and clinical observations
- -Exogenous androgens or anabolic steroids - may produce additive or synergistic muscle hypertrophy but also compound cardiovascular strain and hormonal dysregulation
- -FSH-dependent fertility treatments - activin A inhibition by ACE-031 suppresses FSH, potentially undermining ovarian stimulation protocols and reproductive therapies
- -Corticosteroids (standard of care in DMD) - interaction data limited; both affect muscle and bone metabolism, and combined effects on bone density warrant monitoring
Cost & Where to Buy
ACE-031 is not commercially available as an approved pharmaceutical; pricing reflects research-grade or grey-market synthesis from peptide vendors, where quality and purity vary substantially. Given the once-monthly dosing interval and the complexity of producing a large fusion protein, costs are considerably higher than standard peptides and may be difficult to source reliably.
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