ACE-031
A muscle-building decoy receptor whose human trials raised lean mass, then stopped over nosebleeds and dilated blood vessels
ACE-031 (ramatercept) is the outer part of the activin type IIB receptor fused to an antibody tail. It soaks up myostatin and related signals that limit muscle growth. A single dose raised lean mass in healthy women, but its trial in boys with Duchenne muscular dystrophy was stopped for nosebleeds and telangiectasias, and it was never approved.
What is it?
Myostatin and its relatives, including GDF11 and the activins, brake muscle growth by signalling through activin type II receptors. A soluble decoy of the receptor binds those ligands before they reach muscle, and in animals the result is more muscle. ACE-031 was the first such decoy tested in people.
It worked as designed on muscle and failed on safety. Because the same receptor family also governs blood vessels and red-cell production, trapping its ligands broadly produced nosebleeds and small dilated vessels in boys with Duchenne muscular dystrophy, and Acceleron ended the programme. Its successors split the job: luspatercept, a related trap, is approved for anaemia, and antibodies such as bimagrumab target the receptor itself.
ACE-031 is still sold online as a research chemical. A 2025 analysis of 14 such products found that none contained ACE-031: twelve held a different, full-length receptor protein mixed with other proteins.
At a Glance
Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Half-Life: How Much Remains
The dataset records a half-life of 10-15 days after a single subcutaneous dose for ACE-031. After each half-life, half of what was in the circulation is gone, so about 3% remains after five. Real clearance varies with the person, the dose, the route and kidney or liver function; this is arithmetic on a published figure, not a dosing tool.
Published Research
The two human trials, a primate study and a test of black-market products, read from their PubMed abstracts on October 4, 2026.
One dose in healthy women
48 healthy postmenopausal women were randomised, double-blind, to one subcutaneous dose of 0.02 to 3 mg/kg or placebo. It was generally well tolerated, with injection-site redness; the half-life was 10 to 15 days. At 3 mg/kg, lean mass rose 3.3% and thigh muscle volume 5.1% by day 29, with bone and fat markers also shifting.
Boys with Duchenne muscular dystrophy
In a randomised, double-blind, placebo-controlled ascending-dose trial, injections every 2 to 4 weeks caused no serious adverse events, but the trial was stopped after the second dose level over nosebleeds and telangiectasias. Walking distance tended to hold up against decline on placebo, and lean mass and bone density tended to rise, none of it statistically significant.
Marmosets
Marmosets given ACE-031 for 14 weeks gained lean mass, larger type I and II fibres in the biceps, and greater absolute and specific force in an isolated leg muscle, while controls did not change, which the authors read as support for primate efficacy.
What black-market vials contain
Of 14 products sold as ACE-031, 12 contained a protein reacting with the receptor, but it was the full-length human receptor, not the Fc fusion, mixed with many other proteins. The authors' detection method for luspatercept also caught these products in serum.
Side Effects & Contraindications
Reported Side Effects
From the two human trials.
Contraindications & Cautions
Never approved, so no label exists.
Legal Status
Never approved; development stopped in 2013.
Frequently Asked Questions
?What is ACE-031?
A decoy receptor fusion protein that binds myostatin and related signals so they cannot limit muscle growth.
?Why was ACE-031 stopped?
Its trial in boys with Duchenne muscular dystrophy was halted over nosebleeds and telangiectasias, and the developer ended the programme.
?Did ACE-031 build muscle in people?
A single 3 mg/kg dose raised lean mass 3.3% and thigh muscle volume 5.1% at day 29 in healthy postmenopausal women.
?Is ACE-031 banned in sport?
Yes. WADA names decoy activin receptors such as ACE-031 under S4.3, prohibited at all times.
References
- [pubmed] Attie KM, et al. "A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers." Muscle Nerve, 2013;47(3):416-23. PMID: 23169607.
- [pubmed] Campbell C, et al. "Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial." Muscle Nerve, 2017;55(4):458-464. PMID: 27462804.
- [pubmed] Cadena SM, et al. "ACE-031, a soluble activin type IIB receptor, increases muscle mass and strength in the common marmoset (Callithrix jacchus)." PLoS One, 2026;21(2):e0342666. PMID: 41686840.
- [pubmed] Reichel C, et al. "Gel Electrophoretic Detection of Black Market ACE-031." Drug Test Anal, 2025;17(10):1934-1946. PMID: 40312924.
- [pubmed] Tsuchida K. "Clinical Applications of Ligand Traps Targeting Activin Type II Receptors." Antiinflamm Antiallergy Agents Med Chem, 2026;25(2):73-78. PMID: 41487000.
Sources & Citations
Trials, the primate study, the product analysis and the review from their PubMed abstracts, October 4, 2026; WADA status from the dataset's List readings.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.