ACE-031.

Quick Overview.

ACE-031 (Ramatercept) is an experimental, highly potent muscle-building drug that belongs to a class of compounds called Myostatin Inhibitors. Like Follistatin, its goal is to stop Myostatin from telling your muscles to stop growing. However, ACE-031 does this in a completely different way. Instead of acting as a decoy in the blood, ACE-031 is literally a fake, floating version of the receptor that Myostatin normally binds to on your muscle cells. Myostatin binds to the fake receptor (ACE-031) instead of your actual muscle, neutralizing the "stop growing" signal.[1]

Imagine your muscle cell is a house with a specific keyhole on the front door. Myostatin is the key. When the key goes into the keyhole, the house stops building new rooms. ACE-031 is a drug made of millions of fake keyholes floating around in your blood. The Myostatin keys get stuck in the fake keyholes before they can ever reach the real house. Because the real house never gets the "stop" signal, it just keeps building more and more rooms (muscle).[2]

• Primary Use Case: Extreme muscle hypertrophy by neutralizing Myostatin and Activin.
• Mechanism: A recombinant fusion protein consisting of the extracellular domain of the human Activin receptor type IIB (ActRIIB) fused to an IgG1-Fc domain. It acts as a soluble decoy receptor.[3]
• Who it is for: Nobody. The drug was abandoned in clinical trials due to severe bleeding side effects.
• Who it is NOT for: Anyone who values their health.

The Protocol & Usage Guide.

confidence_tier: well-established

ACE-031 is arguably the most powerful muscle-building peptide ever created, but it is also one of the most dangerous. In 2013, the pharmaceutical companies developing it (Acceleron and Shire) completely halted all clinical trials in boys with Muscular Dystrophy. The drug was causing spontaneous nosebleeds, gum bleeding, and dilated blood vessels in the skin. While it builds muscle like nothing else, the bleeding side effects make it highly risky for biohackers.[4]

Standard Dosing

Note: Because of the incredibly long half-life (10-15 days), frequent injections are not only unnecessary but dangerous, as the drug will accumulate in the blood.

Reconstitution Math (Example for a 1mg vial)

• Add 1 mL of Bacteriostatic Water to the 1mg (1000mcg) vial.
• 1 mg dose = 1.0 mL (100 units on an insulin syringe)

Injection Site Guide

• Where to Inject: Subcutaneous fat in the abdomen. Because it is a systemic decoy receptor, there is no benefit to injecting it directly into a specific muscle.

Cycle Length

• Cycle Length: 4 weeks maximum (e.g., 2 to 4 total injections).
• Time Off: At least 3-4 months. The drug takes over a month to fully clear your system after the last injection.

Nutritional Support & Recommended Supplements.

confidence_tier: well-established

Safety, Interactions & Side Effect Management.

confidence_tier: well-established

The side effects that halted the clinical trials are very real in the bodybuilding community. Users frequently report waking up with blood on their pillows from spontaneous nosebleeds, and bleeding gums when brushing their teeth.

Side Effect Profile

Contraindications

• Absolute: Individuals prone to nosebleeds or taking blood thinners.
• Absolute: Individuals with pre-existing tendon or ligament injuries.
• Absolute: Pregnant or breastfeeding women.

Drug Interactions

• Blood Thinners (Aspirin, Warfarin): SEVERE. Combining ACE-031 with blood thinners drastically increases the risk of severe, uncontrollable bleeding.

Common Stacks & Combinations.

confidence_tier: community

Body Composition & Training Guide.

confidence_tier: community

• Volume over Weight: Because your muscles will get stronger faster than your tendons, you must avoid powerlifting (1-3 reps). Focus on high-volume bodybuilding training to stimulate the muscle without snapping a tendon.
• Tracking Progress: Track body weight daily (it should climb rapidly). Monitor for any signs of unexplained bruising or bleeding.

Storage, Handling & Accessibility.

confidence_tier: well-established

• Storage (Lyophilized): Store in the freezer (-20°C) for up to 3-5 years, or in the fridge (2-8°C) for 1-2 years.
• Storage (Reconstituted): Must be stored in the fridge (2-8°C). Good for 14-21 days.
• WADA Status: Banned in competitive sports under section S4 (Myostatin inhibitors).
• Cost & Accessibility: Extremely high rate of counterfeit products on the market. Legitimate ACE-031 can cost hundreds of dollars per milligram.

Bloodwork Monitoring Guide.

confidence_tier: well-established

• Complete Blood Count (CBC): Monitor platelet levels and red blood cell counts due to the bleeding risks associated with the drug.
• Coagulation Panel (PT/INR): To ensure blood clotting mechanisms are functioning normally.

Comparison to Similar Compounds.

confidence_tier: well-established

Deep Dive (For Advanced Researchers).

confidence_tier: well-established

Mechanism of Action

ACE-031 (Ramatercept) is a recombinant fusion protein. It is engineered by taking the extracellular domain of the human Activin receptor type IIB (ActRIIB) and fusing it to the Fc portion of a human immunoglobulin G1 (IgG1) antibody.[3]

The addition of the IgG1-Fc domain is a common pharmacological trick used to drastically extend the half-life of a protein. It prevents rapid renal clearance and allows the molecule to be recycled by the neonatal Fc receptor (FcRn), extending the half-life of ACE-031 to an incredible 10-15 days.[5]

The TGF-β Superfamily

Muscle growth is negatively regulated by several proteins in the TGF-β superfamily, primarily Myostatin (GDF-8), Activin A, and GDF-11. These proteins normally bind to the ActRIIB receptor on the surface of muscle cells, triggering a Smad2/3 signaling cascade that halts muscle protein synthesis.[6]

ACE-031 acts as a highly potent, circulating decoy receptor. Because it is the ActRIIB receptor (just floating freely in the blood), Myostatin and Activin bind to it with extremely high affinity. By trapping these negative regulators in the blood, ACE-031 prevents them from ever reaching the actual muscle cells. The Smad2/3 inhibition is lifted, and the Akt/mTOR pathway is disinhibited, leading to massive, unchecked muscle hypertrophy.[2]

Clinical Trial Summary

• Phase 1 (Healthy Adults): In a single ascending-dose study in healthy postmenopausal women, a single injection of ACE-031 (3 mg/kg) resulted in a massive 5.1% increase in thigh muscle volume in just 29 days.[7]
• Phase 2 (Duchenne Muscular Dystrophy): Acceleron Pharma and Shire initiated a Phase 2 trial in boys with DMD. The drug was highly effective at building muscle.[4]
• The Halt (2013): The trial was abruptly halted, and development of ACE-031 was abandoned. The boys were experiencing epistaxis (nosebleeds), gingival bleeding, and the development of telangiectasias (small, dilated blood vessels on the skin).[4]

Synergy & Antagonism Analysis

• The Off-Target Effects (Why it bleeds): The ActRIIB receptor doesn't just bind Myostatin; it also binds Bone Morphogenetic Proteins 9 and 10 (BMP-9 and BMP-10). These proteins are crucial for angiogenesis (the formation and maintenance of blood vessels). By acting as a decoy for BMP-9/10, ACE-031 disrupts normal capillary formation, leading to fragile blood vessels that spontaneously rupture and bleed. This off-target effect is the sole reason the drug failed clinical trials.[8]

Frequently Asked Questions (FAQ).

confidence_tier: community

Q: Is the ACE-031 on peptide websites real? A: Almost never. It is a massive fusion protein that is incredibly difficult to manufacture. Most "ACE-031" sold online is either completely fake or just under-dosed Follistatin.

Q: If I take Vitamin K, will it stop the bleeding? A: No. Vitamin K helps with normal blood clotting, but ACE-031 physically disrupts the formation of the capillaries themselves. No amount of vitamins will stop the structural damage to the blood vessels.

Q: How much muscle can I gain? A: In clinical trials, a single injection caused a 5% increase in muscle volume in less than a month. It is arguably the most potent muscle builder in existence, but the side effects make it unusable.

International Regulatory Status.

confidence_tier: well-established

Decision Tree.

confidence_tier: community

[Goal: Extreme Muscle Growth via ACE-031?]
  |
  +-- Are you aware that this drug causes spontaneous bleeding?
        |
        +-- (No) -> STOP: Read the clinical trial data.
        |
        +-- (Yes) -> Are you willing to risk permanent vascular damage?
              |
              +-- (No) -> STOP: Do not use ACE-031.
              |
              +-- (Yes) -> We strongly advise against using this compound.
                           If you proceed, use no more than 1mg every 14 days.

Schema.org Data.

{
  "@context": "https://schema.org",
  "@type": "MedicalEntity",
  "name": "ACE-031",
  "alternateName": ["Ramatercept", "Soluble ActRIIB-Fc"],
  "description": "A recombinant fusion protein that acts as a soluble decoy receptor for Myostatin and Activin, abandoned in clinical trials due to severe bleeding side effects.",
  "legalStatus": {
    "@type": "DrugLegalStatus",
    "description": "Unapproved by FDA; clinical trials halted. Prohibited in-competition by WADA."
  }
}

What we cited.