Side-by-side · Research reference
ACE-031vsGDF-8
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-StrongHUMAN-REVIEWED23/48 cited
ACE-031
ActRIIB-Fc Fusion · Phase 2 Halted
SQ · Weekly dosing investigated
GDF-8
TGF-β Superfamily · Negative Muscle Regulator
15–20%Muscle mass gain (MSTN−/−)
Not administered — research target for inhibition
01Mechanism of Action
Parameter
ACE-031
GDF-8
Primary target
Myostatin, GDF11, activin A — TGF-β superfamily ligands
Activin type II receptors (ActRIIA/B) on skeletal muscleIglesias 2026
Pathway
Soluble decoy receptor binds circulating myostatin/TGF-β ligands → prevents ActRIIB activation → SMAD2/3 pathway inhibition
MSTN → ActRII/TGFBR1 → Smad2/3 signaling → muscle protein synthesis suppression
Downstream effect
Disinhibition of myogenic signaling, increased skeletal muscle mass and strength
Restricts muscle hypertrophy, limits satellite cell activation, increases proteolysis via ubiquitin-proteasome and autophagy pathwaysGong 2026Iglesias 2026
Feedback intact?
—
Yes — part of muscle-pituitary endocrine axis; muscle-derived MSTN influences FSH synthesisIglesias 2026
Origin
Recombinant fusion protein: human ActRIIB extracellular domain + IgG1-Fc fragmentReichel 2025
Endogenous myokine secreted by skeletal muscle; circulates systemically as latent complexIglesias 2026
Antibody development
—
—
02Dosage Protocols
Parameter
ACE-031
GDF-8
Clinical dosing
Weekly or biweekly SQ injections (exact doses undisclosed pre-halt)
Phase 2 DMD trial protocol not fully published.
—
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
—
Evidence basis
Phase 2 trial discontinued — incomplete dataset
—
Half-life
Days to weeks (Fc-fusion typical kinetics)
IgG1-Fc domain confers extended circulation time.
—
Duration investigated
12–24 weeks (trial cut short)
—
Clinical use
—
None — MSTN is a research target for inhibition, not a therapeutic peptide administered to humans
Sold by research suppliers (e.g., CertaPeptides) for in vitro / animal studies only.
Inhibition strategies
—
Monoclonal antibodies, VLP-based active immunotherapy, gene editing (CRISPR)
VLP immunogen (MS2.87-97)
—
Active immunization protocol in mice — elicits anti-MSTN antibodies without GDF11 cross-reactivityJacquez 2026
Reduces body fat, increases muscle mass and grip strength; no major safety concerns in animal models.Jacquez 2026
Dual immunization (MSTN + Activin A)
—
Combined active immunization in GH-deficient miceMansoor 2026
Improves skeletal muscle performance beyond single-target inhibition.Mansoor 2026
Gene editing outcomes
—
Precision CRISPR edits produce double-muscle phenotype, improved carcass quality in livestock
Pleiotropic effects on metabolism, reproduction, and welfare require systematic evaluation.
03Metabolic / Fat Loss Evidence
Parameter
ACE-031
GDF-8
Primary mechanism
—
MSTN loss-of-function reduces fat accumulation independent of muscle mass effects
Human genetic evidence
—
Humans with MSTN function-disrupting variants have increased muscle mass, strength, and reduced adiposityHerman 2026
Animal model outcomes
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VLP-immunized mice: reduced age-associated weight gain, significantly lower body fat by DEXAJacquez 2026
Adipose-muscle crosstalk
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MSTN modulates myostatin-TAZ signaling; inhibition shifts adipose expansion toward hyperplasiaLi 2026
Age-related effects
—
MSTN upregulation linked to age-dependent muscle atrophy and fat accumulation
04Side Effects & Safety
Parameter
ACE-031
GDF-8
Epistaxis (nosebleeds)
Significant incidence in Phase 2 DMD trial — primary safety signal
—
Telangiectasia
Dilated capillaries / spider veins observed
—
Vascular abnormalities
Mechanism: ActRIIB/ALK1 pathway disruption affects vascular homeostasis
—
Injection site reactions
Local erythema, induration (biologics class effect)
—
Antibody development
Potential for anti-drug antibodies (Fc-fusion proteins); incidence not reported
—
Black market contaminants
12/14 tested products contained multiple unidentified proteins alongside ACE-031Reichel 2025
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Genetic null phenotype
—
No known adverse phenotypes in humans or mice with MSTN loss-of-functionJacquez 2026
Antibody cross-reactivity risk
—
Non-selective inhibitors may block GDF11, affecting cardiac and neural function
VLP immunotherapy safety
—
No major safety concerns in mice; rare hypersensitivity possibleJacquez 2026
Pleiotropic effects (gene editing)
—
MSTN editing may affect reproductive performance, metabolic homeostasis, and animal welfare
Assay variability
—
Circulating MSTN levels often fail to mirror intramuscular changes; clinical interpretation challengingIglesias 2026
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
GDF-8
- ·Not applicable — MSTN is not administered as a therapeutic agent
Relative Contraindications
ACE-031
- ·Coagulation disorders or anticoagulant use (epistaxis risk)
- ·Hereditary hemorrhagic telangiectasia (HHT) family history
- ·Cardiovascular disease (vascular remodeling effects unknown)
GDF-8
- ·Inhibition strategies contraindicated in conditions requiring maintained muscle proteostasis (theoretical)
05Administration Protocol
Parameter
ACE-031
GDF-8
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.
GDF-8 (myostatin) is not administered to humans. It is studied as a target for inhibition using monoclonal antibodies, active immunotherapy (VLP-based vaccines), or gene editing (CRISPR). Research-grade peptide supplied by vendors like CertaPeptides is intended for in vitro and animal studies only.
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
Clinical development focuses on blocking MSTN activity via: (1) neutralizing monoclonal antibodies targeting mature MSTN or ActRII receptors; (2) active immunotherapy generating endogenous anti-MSTN antibodies (e.g., MS2.87-97 VLP platform); (3) precision gene editing to disrupt MSTN expression in livestock or therapeutic contexts.
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
MS2.87-97 VLP administered to mice elicits anti-MSTN antibodies targeting a discrete epitope in mature MSTN protein. Immunization schedule and dose optimized for sustained antibody response without GDF11 cross-reactivity. No human protocols established.Jacquez 2026
4. Clinical trial route
Phase 2 protocol used subcutaneous injections at weekly or biweekly intervals. Exact dosing protocols remain unpublished.
CRISPR-mediated MSTN knockout produces double-muscle phenotype in livestock (cattle, swine, sheep). Ethical frameworks and welfare assessments required; pleiotropic effects on reproduction, metabolism, and health must be systematically evaluated before human translation.