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    Hormonal & Endocrine•Updated 2026-02-01•5 min read

    What Is ACE-031? Benefits, Research & Safety

    A myostatin/activin decoy receptor designed to promote muscle growth, researched for muscular dystrophy but development discontinued.

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    Also known as:
    ActRIIB-Fc
    Activin Receptor Type IIB Fusion Protein
    DAnimal/cell evidence onlyUK: Unlicensed (UK)WADA: Prohibited in sport

    UK summary: Discontinued investigational compound. Acceleron Pharma stopped development of ACE-031 in 2013 after safety signals. Not a licensed UK medicine; not currently in active clinical development. Prohibited under WADA S1.2 / S4.

    Quick Facts

    Category
    Hormonal & Endocrine
    Half-Life
    Extended due to Fc fusion (approximately 10-14 days)
    UK Status
    Not approved. Development discontinued.
    EU Status
    Development discontinued. Not available.

    Overview

    ACE-031 is a soluble fusion protein consisting of the extracellular domain of activin receptor type IIB (ActRIIB) fused to human IgG1 Fc. It functions as a "decoy receptor" or "ligand trap," binding to and neutralising myostatin, activins, and other TGF-β family ligands that normally inhibit muscle growth. By sequestering myostatin and related factors, ACE-031 was designed to remove the natural limits on muscle development, potentially offering benefit for conditions characterised by muscle wasting such as muscular dystrophy, cancer cachexia, and sarcopenia. Acceleron Pharma developed ACE-031 specifically for Duchenne muscular dystrophy (DMD). Early trials showed promising increases in lean body mass. However, development was halted after safety signals emerged, including nosebleeds, gum bleeding, and telangiectasias (dilated blood vessels in skin). Despite ACE-031's discontinuation, the approach of ActRIIB blockade continues to be researched. Related compounds and alternative myostatin inhibitors remain in development for various conditions. ACE-031 represented an important proof-of-concept for myostatin inhibition approaches, even though it did not achieve clinical approval.
    Evidence standards summary

    ACE-031 — evidence and risk at a glance

    Twenty standard modules scored against the Peptide Authority evidence grading methodology. Missing modules indicate the field has not yet been characterised editorially — treat absences as uncertainty rather than reassurance.

    01Evidence snapshot

    DAnimal/cell evidence onlyOverall grade against our evidence grading methodology.

    Discontinued investigational compound. Acceleron Pharma stopped development of ACE-031 in 2013 after safety signals. Not a licensed UK medicine; not currently in active clinical development. Prohibited under WADA S1.2 / S4.

    02Human evidence grade

    DAnimal/cell evidence onlyStrength of evidence from published human trials.

    03Preclinical evidence grade

    BModerate human evidenceAnimal-model and in-vitro evidence quality.

    04Regulatory status

    • UK: Not approved. Development discontinued.
    • EU: Development discontinued. Not available.
    • Notes: ACE-031 development was halted by Acceleron Pharma in 2013 due to vascular safety concerns. It never achieved regulatory approval. Related research continues with modified approaches.

    05Approved medical uses

    None in the UK or EU as a finished medicine. (Or: not yet documented; treat as absence rather than approval.)

    06Unapproved / promotional claims

    • Builds muscle like myostatin gene therapy.
    • Restores muscle mass safely.
    • Undetectable in drug tests.

    07Common internet claims

    • Marketed in bodybuilding stacks despite development halt.
    • Sold by grey-market vendors as 'pharmaceutical-grade research peptide'.

    08Claim vs evidence

    ClaimEvidenceHuman evidence?Regulatory concernSafer wording
    “Available from research suppliers for muscle building”ENoHighDevelopment was halted on safety grounds. Any 'ACE-031' from grey-market suppliers has no provenance verification.

    09Safety uncertainty score

    Very high

    Effectively no human safety data; safety claims are extrapolations from animal work or anecdote.

    10Known adverse signals

    • Development halted in 2013 due to safety signals (nosebleeds, vascular issues).
    • Theoretical reproductive disruption (myostatin / activin pathway).
    • WADA S1.2 / S4 prohibited.

    11Drug-interaction uncertainty

    High

    Interaction picture sparse; meaningful uncertainty when combined with other medicines.

    12Anti-doping status

    WADA: Prohibited in sportWADA strict-liability framing applies.

    13UK legal position

    UK: Unlicensed (UK)

    Not approved. Development discontinued.

    14EU legal position

    Development discontinued. Not available.

    15What this page cannot tell you

    • Whether grey-market 'ACE-031' contains the originally developed compound or a different myostatin-pathway molecule.
    • Long-term safety beyond the trials that ended in 2013.

    16Last reviewed

    Last reviewed:

    Next review due:

    Spotted an error or something out of date? Send a correction.

    17Citation quality score

    CLimited human evidenceQuality of the sources we cite, graded against the evidence grading methodology.

    18Research gaps

    • No active clinical development; only historical Phase 1/2 data available.

    19Safer alternatives / established care pathways

    • Progressive resistance training with adequate protein.
    • Neuromuscular-disease specialist referral for genuine muscle-wasting conditions.

    Related Safety Centre page → Athlete anti-doping risks

    20Doctor discussion prompts

    Questions to ask a qualified clinician

    These are starter questions you can adapt for a GP, specialist, pharmacist, or anti-doping advisor. The aim is to help you have a better-informed conversation — not to replace one.

    • What licensed muscle-wasting treatments are appropriate?

    Discovery & History

    The myostatin inhibition field began with Se-Jin Lee's discovery of myostatin in 1997 and the observation that myostatin-null animals developed massive muscle hypertrophy. This immediately suggested therapeutic potential for muscle wasting conditions. Multiple approaches to myostatin inhibition were developed, including antibodies, propeptides, and decoy receptors. The ActRIIB decoy approach was attractive because it could neutralise not only myostatin but also other inhibitory ligands like activins. Acceleron Pharma developed ACE-031 as a fusion of ActRIIB with an antibody Fc domain, providing good pharmacokinetic properties and allowing subcutaneous administration. Phase I trials in healthy volunteers showed ACE-031 increased lean body mass, confirming proof of concept. Phase II trials in Duchenne muscular dystrophy patients began with encouraging early results. However, in 2013, Acceleron announced discontinuation of ACE-031 development due to safety concerns. Patients experienced nosebleeds and telangiectasias, believed related to effects on BMP9, a ligand involved in blood vessel integrity that also binds to ActRIIB. Acceleron continued developing related compounds with different ligand binding profiles. ACE-083 (local muscle administration) and other agents are being explored. The company's experience with ACE-031 informed development of luspatercept (approved for anemia), which is related but has different activity.

    Mechanism of Action

    ACE-031 functions as a soluble decoy receptor: **Ligand Trap Mechanism** ACE-031 binds to and sequesters multiple TGF-β family ligands: - Myostatin: Primary target for muscle growth inhibition - Activin A and B: Also inhibit muscle growth - GDF11: Related to myostatin - BMP9: Involved in vascular biology (associated with side effects) **Effects on Muscle** By neutralising inhibitory ligands: - Removes brake on muscle protein synthesis - Promotes satellite cell activation - Increases muscle fiber size (hypertrophy) - May also increase muscle fiber number (hyperplasia) - Improves muscle strength proportional to mass gains **Broader TGF-β Effects** Effects beyond muscle due to activin and other ligand binding: - Bone: Activin inhibition may affect bone metabolism - Fat: Potential effects on adipose tissue - Other tissues: Diverse effects possible **Vascular Effects (Safety Concern)** Binding to BMP9 disrupted endothelial function: - BMP9 is important for blood vessel integrity - Loss of BMP9 signaling led to telangiectasias - Nosebleeds and gum bleeding resulted - This led to development discontinuation

    Researched Benefits

    Based on preclinical and clinical research findings:

    • 1
      Significant increases in lean body mass (demonstrated in trials)
    • 2
      Proof of concept for myostatin inhibition
    • 3
      Potential for muscular dystrophy treatment (not realized)
    • 4
      Increased muscle strength parallel to mass gains
    • 5
      Informed development of related therapeutics

    Claim vs Evidence

    How popular claims about ACE-031 stack up against the current research, graded using our public evidence grading methodology.

    ClaimEvidenceHuman evidence?Regulatory concernSafer wording
    “Available from research suppliers for muscle building”ENoHighDevelopment was halted on safety grounds. Any 'ACE-031' from grey-market suppliers has no provenance verification.

    Theoretical Dosing & Protocols

    ⚠️ Educational Only: The following information is derived from research literature and is not a prescription or recommendation. No standardised human dosing exists. Always consult a qualified healthcare professional.
    Theoretical DosageClinical trials used doses up to 3 mg/kg
    FrequencyEvery two weeks in trials
    DurationDevelopment discontinued; no established protocols
    Notes⚠️ ACE-031 development was discontinued due to safety concerns. It is not available for therapeutic use. This information is provided for educational purposes about the history of myostatin inhibition research.

    Administration Routes

    Routes studied in research settings (educational only):

    • Subcutaneous injection (clinical trials)
    Half-LifeStability
    Extended due to Fc fusion (approximately 10-14 days)Standard protein handling requirements

    Safety Profile & Known Risks

    Commonly Reported Side Effects

    • Nosebleeds (epistaxis)
    • Gum bleeding
    • Telangiectasias (dilated blood vessels in skin)
    • Injection site reactions

    Rare Risks & Concerns

    • Development discontinued due to vascular safety signals
    • Long-term effects unknown
    • Effects on other TGF-β pathways

    Contraindications

    • Development discontinued—not available for use
    • History of bleeding disorders would have been concerning

    UK & EU Regulatory Context

    🇬🇧 United Kingdom

    Not approved. Development discontinued.

    🇪🇺 European Union

    Development discontinued. Not available.

    ACE-031 development was halted by Acceleron Pharma in 2013 due to vascular safety concerns. It never achieved regulatory approval. Related research continues with modified approaches.

    Clinical Studies Summary

    Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial.

    ACE-031 use demonstrated trends for pharmacodynamic effects on lean mass, fat mass, BMD, and 6MWT. Non-muscle-related adverse events contributed to the decision to discontinue the study. Myostatin inhibition is a promising therapeutic approach for DMD. Muscle Nerve 55: 458-464, 2017.

    Muscle Nerve. 2017View on PubMed

    A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers.

    Single-dose ACE-031 treatment was generally well-tolerated and resulted in increases in muscle mass in healthy postmenopausal women.

    Muscle Nerve. 2013View on PubMed

    ACE-031, a soluble activin type IIB receptor, increases muscle mass and strength in the common marmoset (Callithrix jacchus).

    The company is no longer active. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

    PLoS One. 2026View on PubMed

    Gel Electrophoretic Detection of Black Market ACE-031.

    In rat serum, BM ACE-031 was detectable up to 48 h post administration. However, due to the relatively high dose applied (10 mg/kg body weight) and possible differences in metabolism, the detection window may be different in humans.

    Drug Test Anal. 2025View on PubMed

    The relationship between myodural bridges, hyperplasia of the suboccipital musculature, and intracranial pressure.

    In contrast, surgically severing the MDB connections resulted in a significant decrease in intracranial pressure. Thus, these results indicated that muscular activation of the MDB may affect CSF circulation, suggesting a potential functional role of the MDB, and providing a new research perspective on CSF dynamics.

    PLoS One. 2022View on PubMed

    Emerging drugs affecting skeletal muscle function and mitochondrial biogenesis - Potential implications for sports drug testing programs.

    Focusing on skeletal muscle and mitochondrial biogenesis, numerous substances exhibiting agonistic or antagonistic actions on different cellular 'control centers' resulting in increased skeletal muscle mass, enhanced performance (as determined with laboratory animal models), and/or elevated amounts of mitochondria have been described. Substances of interest include agonists for REV-ERBα (e.g.

    Rapid Commun Mass Spectrom. 2016View on PubMed

    Registered Trials & Regulatory Status

    Registered trials
    4
    Currently recruiting
    0
    Furthest phase
    Phase 2
    Approved product
    No

    2 of 2 completed trials have never posted results. Unreported trials are not neutral: results that go unpublished are more often negative ones.

    Extension Study of ACE-031 in Subjects With Duchenne Muscular Dystrophy

    PHASE2

    Status: Terminated · 11 participants · Acceleron Pharma, Inc., a wholly-owned subsidiary of Merck & Co., Inc., Rahway, NJ USA

    Conditions: Duchenne Muscular Dystrophy

    No results postedNCT01239758

    Study of ACE-031 in Subjects With Duchenne Muscular Dystrophy

    PHASE2

    Status: Terminated · 24 participants · Acceleron Pharma, Inc., a wholly-owned subsidiary of Merck & Co., Inc., Rahway, NJ USA

    Conditions: Duchenne Muscular Dystrophy

    Results postedNCT01099761

    A Safety, Tolerability, Pharmacokinetic and Pharmacodynamic Study of ACE-031 in Healthy Postmenopausal Women

    PHASE1

    Status: Completed · 70 participants · Acceleron Pharma, Inc., a wholly-owned subsidiary of Merck & Co., Inc., Rahway, NJ USA

    Conditions: Muscular Atrophy

    No results postedNCT00952887

    A Safety, Tolerability, Pharmacokinetic and Pharmacodynamic Study of ACE-031 (ActRIIB-IgG1)in Healthy Postmenopausal Volunteers

    PHASE1

    Status: Completed · 48 participants · Acceleron Pharma, Inc., a wholly-owned subsidiary of Merck & Co., Inc., Rahway, NJ USA

    Conditions: Muscle Loss

    No results postedNCT00755638

    Adverse event reports (FDA FAERS)

    Not applicable: no licensed product contains this peptide, so it is not reported through FAERS. This is an absence of surveillance, not evidence of safety.

    Source: ClinicalTrials.gov and openFDA. Updated automatically.

    Looking for ACE-031?

    Source research-grade ACE-031 from a trusted UK supplier — third-party tested with certificate of analysis.

    View at Supplier

    Frequently Asked Questions

    Questions to ask a qualified clinician about ACE-031

    These are starter questions you can adapt for a GP, specialist, pharmacist, or anti-doping advisor. The aim is to help you have a better-informed conversation — not to replace one.

    • What licensed muscle-wasting treatments are appropriate?

    UK regulatory & safety context

    Athlete anti-doping risks

    Safety Centre guide

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