Side-by-side · Research reference
ACE-031vsLL-37
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
BHuman-MechanisticHUMAN-REVIEWED15/35 cited
ACE-031
ActRIIB-Fc Fusion · Phase 2 Halted
SQ · Weekly dosing investigated
LL-37
Cathelicidin · Human AMP
Broad-spectrumAntimicrobial activity
Endogenous · Secreted at inflammation sites
01Mechanism of Action
Parameter
ACE-031
LL-37
Primary target
Myostatin, GDF11, activin A — TGF-β superfamily ligands
Pathway
Soluble decoy receptor binds circulating myostatin/TGF-β ligands → prevents ActRIIB activation → SMAD2/3 pathway inhibition
hCAP-18 precursor → Proteinase-3 cleavage → LL-37 release → Membrane insertion/disruption
Downstream effect
Disinhibition of myogenic signaling, increased skeletal muscle mass and strength
Membrane permeabilization, cytokine induction, autophagy, phagosome-lysosome fusion, chemotaxisAhmad 2026Zhang 2026
Feedback intact?
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Origin
Recombinant fusion protein: human ActRIIB extracellular domain + IgG1-Fc fragmentReichel 2025
Endogenous human cathelicidin (37-AA fragment, residues 134–170 of hCAP-18)
Antibody development
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02Dosage Protocols
Parameter
ACE-031
LL-37
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
In vitro, animal models, human observational
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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Endogenous expression
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Constitutive in neutrophils, epithelial tissues
Upregulated during infection and inflammation.Pinheiro 2026
Exogenous (experimental)
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Dose varies by study; antimalarial ~10–50 μM in vitro
No FDA-approved exogenous formulation.
04Side Effects & Safety
Parameter
ACE-031
LL-37
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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Cytotoxicity (high dose)
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Membrane disruption in host cells at supraphysiological concentrations
Pro-inflammatory signaling
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Can exacerbate inflammation in certain contexts (context-dependent)Pinheiro 2026
Theoretical cancer risk
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Immunomodulatory roles in tumor microenvironment under investigation
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
LL-37
—Relative Contraindications
ACE-031
- ·Coagulation disorders or anticoagulant use (epistaxis risk)
- ·Hereditary hemorrhagic telangiectasia (HHT) family history
- ·Cardiovascular disease (vascular remodeling effects unknown)
LL-37
- ·Active autoimmune disease (theoretical immune dysregulation)
05Administration Protocol
Parameter
ACE-031
LL-37
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.
LL-37 is constitutively expressed in neutrophils and epithelial cells, cleaved from hCAP-18 by proteinase-3 at sites of infection or inflammation.
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
Synthetic LL-37 and derivatives (e.g., SAMP-12aa) tested in vitro and animal models. Administered via topical, intraperitoneal, or intravenous routes in research settings.
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
LL-37 is resistant to pepsin degradation at gastric pH. Synthetic short peptides designed to retain this stability while reducing toxicity.Lu 2026
4. Clinical trial route
Phase 2 protocol used subcutaneous injections at weekly or biweekly intervals. Exact dosing protocols remain unpublished.
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