ActRIIB-Fc fusion protein for muscle mass - blocks myostatin pathway
Protein Synthesis
Anabolic peptides upregulate mTOR signaling for muscle fiber growth.
Quickstart Highlights
- Dosage: 1mg/kg
- Frequency: Bi-weekly
- Administration: Subcutaneous
- Cycle length: 8-12 weeks
Dosing Plan
| Weeks | Dose | Units |
|---|---|---|
| Standard plan | 1mg/kg bi-weekly | Based on body weight |
| Conservative | 0.5mg/kg bi-weekly | Lower starting dose |
| Clinical Trial Dose | 1-3mg/kg every 2 weeks | As studied in DMD trials |
How This Works
ACE-031 is a soluble form of the Activin Receptor Type IIB (ActRIIB) fused to an IgG1 Fc domain. It acts as a decoy receptor, binding myostatin, activin, GDF-11, and other TGF-β ligands before they can reach their cell surface receptors. By intercepting these muscle-limiting signals, ACE-031 promotes muscle growth and may reduce fat mass. It represents a broader approach than targeting myostatin alone.
Mechanism of Action
How ACE-031 Works in Your Body
Peptide Administered
Enters bloodstream and reaches muscle tissue
mTOR Activation
Triggers the muscle protein synthesis pathway
Protein Synthesis
Cells ramp up production of new muscle fibers
Muscle Growth
Increased lean mass and faster recovery
Benefits & Side Effects
Potential Benefits
- Significant muscle mass increase (shown in animal models)
- Blocks multiple muscle-limiting pathways (not just myostatin)
- Bi-weekly dosing convenience
- Potential for treating muscle-wasting conditions
Potential Side Effects
- Nosebleeds and gum bleeding (noted in clinical trials)
- Telangiectasias (dilated small blood vessels)
- Clinical trials halted due to vascular safety concerns
- Unknown long-term effects
- Very limited human safety data
Good to know
- HIGHLY EXPERIMENTAL - clinical trials were halted for safety concerns.
- Was being developed for Duchenne muscular dystrophy (DMD).
- Blocks the ActRIIB receptor, preventing myostatin and activin signaling.
- May cause nosebleeds, gum bleeding, and telangiectasias (dilated blood vessels).
- Very limited availability - primarily through research chemical suppliers.
- Not recommended without medical supervision.
- Bimagrumab (BYM338) is a related but different approach that went further in trials.
Community Insights
Summarised from 2 sourcesActRIIB-Fc fusion protein for muscle mass - blocks myostatin pathway Experimental. Was in clinical trials for muscular dystrophy. Limited availability
Common Dosages Reported
- 1mg/kg Bi-weekly
- Standard protocol dosing
Side Effects Mentioned
- Generally mild, individual variation expected
- See full guide for detailed safety info
Stacking Suggestions
- Consult research and healthcare provider before stacking
What people are saying
Results vary based on individual response
Consistent dosing and timing important
Reviews & Discussion
Real experiences shared by the community — not medical advice.
ACE-031 Safety and Heart Concerns
One individual cautioned that despite the muscle-building potential of ACE-031, the peptide carries risks such as potential damage to the heart muscle. They emphasized that while it is effective for hypertrophy, the safety profile and potential for long-term health issues are significant concerns.
ACE-031 for Muscle Growth and Physical Transformation
A user reported observing significant muscle growth while using ACE-031, describing the person using it as looking like a 'beast.' They noted that the peptide appeared effective for increasing muscle mass, though they expressed concerns about the potential for extreme muscle growth to outpace tendon strength.
Myostatin inhibitors labeled as useless
A user shared that their research into forums suggests myostatin inhibitors like ACE-031 are not effective for increasing muscle mass. They noted that these proteins often fail to live up to the 'miracle product' claims and are frequently associated with various side effects.
Preclinical Data Summary for ACE-031
A user shared clinical trial data from 2007 indicating that ACE-031 increased muscle mass in preclinical mouse models, even when offset by glucocorticoid-induced muscle loss. The report notes that ACE-031 (an ActRIIB-based protein) demonstrated a 19% increase in lean body mass in mice and was being developed to treat muscular dystrophy and cancer-related atrophy.
Severe Acute Toxic Reaction at 500mcg Dose
A user reported a severe acute toxic reaction after increasing their ACE-031 dosage from 100mcg to 500mcg. Within 15 minutes of administration, the user experienced extreme flu-like symptoms, including nausea, vomiting, diarrhea, and shaking chills that required urgent care medical attention.
Heat Flashes and Activin A Suppression
After one week of use, a user reported side effects consistent with Activin A suppression. They specifically noted feeling very hot after eating large meals.
Effectiveness at Low Doses
A user observed that individuals appear to achieve physical results with low dosages of just a few milligrams. They noted that these results occur even without following the much higher dosing protocols used in clinical settings.
Intense Local Pain and Flu-like Symptoms
A user reported an intense negative reaction to the peptide, including significant local pain at the injection site. They also experienced quick-onset flu-like symptoms that lasted for a day and a half.
Extreme Muscularity and Physiological Limits
A user mentioned that ACE-031, along with other myostatin inhibitors, is capable of producing extreme muscularity. However, they cautioned that such development is often limited by the structural integrity of tendons and the metabolic demands of maintaining excessive muscle mass.
ACE-031 Disappointment and Safety Concerns
A user commented on the lack of effectiveness of ACE-031, describing it as a disappointment despite the high expectations surrounding its development for muscle growth. They noted that clinical trials were discontinued due to safety concerns like nosebleeds and dilated blood vessels.
Myostatin's inhibitors are useless!!!
A user concluded through personal research and forum analysis that myostatin inhibitors like ACE-031 are largely ineffective for muscle growth. They further noted that these proteins often lead to numerous side effects, making them far from the "miracle" products they are sometimes claimed to be.
Preclinical Study Data on ACE-031
A company-provided preclinical study report noted that ACE-031 effectively increased lean body mass in mice, even when combined with muscle-wasting glucocorticoids like dexamethasone. Further clinical development was planned to address neuromuscular diseases and cancer-related muscle loss.
Severe Toxic Reaction to ACE-031 Dosing
A user reported a severe acute toxic reaction after taking a 500mcg dose of ACE-031, despite having no issues with smaller 100mcg doses. Within 15 minutes of the higher dose, the user experienced intense flu-like symptoms, including muscle aches, nausea, chills, vomiting, and diarrhea that required urgent care. The user noted the product had a Certificate of Analysis showing 99% purity, leading to concerns about potential endotoxin contamination.
Efficacy at lower dosages
A user noted that individuals appearing in reports seem to achieve physiological results using dosages of only a few milligrams. This suggests the peptide may be effective at levels much lower than those typically used in clinical trials.
Intense injection site pain and flu symptoms
A user described an intense negative reaction to the peptide, including significant local injection site pain and the rapid onset of flu-like symptoms. These side effects persisted for approximately a day and a half before subsiding.
Heat flashes following large meals
After one week of use, a user reported experiencing side effects consistent with Activin A suppression. Specifically, they noted feeling excessively hot after consuming large meals.
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