Side-by-side · Research reference
ACE-031vsP21
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2HUMAN-REVIEWED10/44 cited
BAnimal-MechanisticHUMAN-REVIEWED8/36 cited
ACE-031
ActRIIB-Fc Fusion · Phase 2 Halted
SQ · Weekly dosing investigated
P21
CNTF-Derived Neuropeptide · Animal Model Evidence
Animal onlyEvidence level
SQ · Site unspecified · Frequency unknown
01Mechanism of Action
Parameter
ACE-031
P21
Primary target
Myostatin, GDF11, activin A — TGF-β superfamily ligands
CNTF receptor alpha (CNTFRα) / LIF receptor (LIFR) / gp130 complex on neural stem cells
Pathway
Soluble decoy receptor binds circulating myostatin/TGF-β ligands → prevents ActRIIB activation → SMAD2/3 pathway inhibition
CNTF mimetic → CNTFRα/LIFR/gp130 heterotrimer → JAK/STAT3 signaling → neurogenesis, stem cell proliferation, neuroprotection
Downstream effect
Disinhibition of myogenic signaling, increased skeletal muscle mass and strength
Increased neural stem cell self-renewal, globose basal cell activation (Mash1+ cells), olfactory sensory neuron regeneration, hippocampal neurogenesis, neuroprotection in developmental disorders
Feedback intact?
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Origin
Recombinant fusion protein: human ActRIIB extracellular domain + IgG1-Fc fragmentReichel 2025
Small-molecule peptide mimetic derived from full-length ciliary neurotrophic factor (CNTF), designed to retain receptor activation with improved pharmacokineticsMottolese 2024
Antibody development
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02Dosage Protocols
Parameter
ACE-031
P21
Clinical dosing
Weekly or biweekly SQ injections (exact doses undisclosed pre-halt)
Phase 2 DMD trial protocol not fully published.
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Black market products
Variable purity; 12/14 tested products contained target protein plus contaminantsReichel 2025
SDS-PAGE revealed multiple protein bands; quality control absent.Reichel 2025
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Evidence basis
Phase 2 trial discontinued — incomplete dataset
Animal models only
CDKL5 KO mice, methimazole-induced olfactory injury, CNTF-/- knockout models.Mottolese 2024Cox 2026Jia 2020
Half-life
Days to weeks (Fc-fusion typical kinetics)
IgG1-Fc domain confers extended circulation time.
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Duration investigated
12–24 weeks (trial cut short)
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Human dosing
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No established protocol
No clinical trial data available.
Animal models (mice)
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Dose and route not specified in abstractsMottolese 2024Jia 2020
In vitro and in vivo studies demonstrate efficacy; precise dosing protocols not disclosed.
Duration
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Not specified
Route
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Presumed subcutaneous or intraperitoneal (animal studies)
04Side Effects & Safety
Parameter
ACE-031
P21
Epistaxis (nosebleeds)
Significant incidence in Phase 2 DMD trial — primary safety signal
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Telangiectasia
Dilated capillaries / spider veins observed
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Vascular abnormalities
Mechanism: ActRIIB/ALK1 pathway disruption affects vascular homeostasis
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Injection site reactions
Local erythema, induration (biologics class effect)
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Antibody development
Potential for anti-drug antibodies (Fc-fusion proteins); incidence not reported
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Black market contaminants
12/14 tested products contained multiple unidentified proteins alongside ACE-031Reichel 2025
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Human safety data
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None available
No clinical trials in humans.
Animal tolerability
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Well-tolerated in mouse models; no toxicity reported in available abstracts
Theoretical risks
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Uncontrolled stem cell proliferation, immune response to peptide, unknown long-term CNS effects
Absolute Contraindications
ACE-031
- ·History of vascular disorders (epistaxis, telangiectasia, HHT)
- ·Pregnancy (TGF-β pathway critical for fetal development)
- ·Active malignancy (myostatin inhibition may affect tumour growth)
- ·Use of non-pharmaceutical grade ACE-031 (contamination risk)Reichel 2025
P21
- ·Use in humans not validated
Relative Contraindications
ACE-031
- ·Coagulation disorders or anticoagulant use (epistaxis risk)
- ·Hereditary hemorrhagic telangiectasia (HHT) family history
- ·Cardiovascular disease (vascular remodeling effects unknown)
P21
- ·Active malignancy (theoretical — neurotrophic signaling may affect tumour growth)
- ·Pregnancy or lactation (no safety data)
05Administration Protocol
Parameter
ACE-031
P21
1. Pharmaceutical status
ACE-031 is not FDA-approved or commercially available. Phase 2 development was discontinued in 2011 due to safety concerns. Any ACE-031 on the black market is unregulated research chemical.
Not established. No FDA approval, no clinical trial data.
2. Black market quality
12 of 14 tested black market ACE-031 products contained the target protein but also carried multiple unidentified protein contaminants detectable by SDS-PAGE. Two products contained no ACVR2B-immunoreactive material.Reichel 2025
In vivo studies used systemic administration (route not specified in abstracts) in mouse models of neurodegeneration, olfactory injury, and CDKL5 deficiency disorder. In vitro studies used primary cell cultures.
3. Detection in sport
ACE-031 is prohibited under WADA S4.3 (Myostatin Inhibitors). Gel electrophoresis and Western blotting using ACVR2B-specific antibodies can detect the ~58.4 kDa protein in biological samples.Reichel 2025
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4. Clinical trial route
Phase 2 protocol used subcutaneous injections at weekly or biweekly intervals. Exact dosing protocols remain unpublished.
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