Why was the trial stopped if the drug was working?

Because what it was doing to blood vessels mattered more than what it was doing to muscle. Participants developed nosebleeds and small dilated skin vessels. Everything resolved when dosing stopped, but the signal pointed at an off-target effect nobody had anticipated, in a trial of children. The muscle findings were only trends at that point anyway.

Is this the same as follistatin or myostatin peptides sold elsewhere?

No. Those are different molecules with different mechanisms and different evidence. ACE-031 is a receptor decoy — it intercepts the signal rather than blocking the receptor, and it intercepts several signals at once.

Is it detectable in doping tests?

Myostatin inhibitors are on the WADA prohibited list at all times, and methods for detecting activin receptor traps have been published. Assume yes.

Muscle & performance

ACE-031

ACVR2B-Fc · ActRIIB-IgG1 · Soluble activin receptor type IIB · Ramatercept

Early human trialsReviewed 1 Sept 2026

ACE-031 is not a peptide. It is a fusion protein: the part of the activin receptor type IIB that sticks out of the cell, joined to the tail of a human antibody. The receptor half soaks up the signals; the antibody half keeps it in circulation for weeks.

Myostatin is the body's brake on muscle growth. Animals lacking it — the Belgian Blue cattle, the whippets bred for it, a small number of documented humans — grow conspicuously more muscle. Blocking it pharmacologically has been an obvious idea for twenty-five years, and ACE-031 was one of the more serious attempts.

Acceleron Pharma and Shire took it into a phase 2 trial in ambulatory boys with Duchenne muscular dystrophy. It was stopped after the second dosing regimen. Not for lack of effect, and not for anything that had happened to muscle: participants developed nosebleeds and telangiectasias — small dilated vessels visible in the skin. Both resolved when dosing stopped, and both pointed at the drug doing something to blood vessels that nobody had designed it to do.

Development was halted in 2011 and permanently discontinued in 2013. That is the part worth carrying: this compound was not abandoned for being uninteresting. It was abandoned because a company with a serious safety obligation to children looked at what it was doing off-target and decided not to continue. The material sold as ACE-031 today is the same molecule, without the monitoring.

How it works

The activin type IIB receptor is where myostatin binds to deliver its signal. ACE-031 is a soluble copy of that receptor's binding domain, so it intercepts myostatin before it reaches the real receptor on muscle. A decoy, or a ligand trap.

Blocking that signal releases the brake on muscle growth, which in animals produces substantial increases in lean mass.

The trap is not selective for myostatin. The same receptor binds activin A, GDF-11 and several other members of the TGF-beta superfamily, and ACE-031 soaks up those too. That lack of selectivity is the most likely explanation for what happened in the trial: activin signalling has a role in vascular biology, and the adverse events were vascular.

The antibody Fc portion gives it a long half-life — the trial dosed subcutaneously every two to four weeks rather than daily. Anything that goes wrong therefore cannot be stopped quickly.

Vocabulary on this page

Half-life: The time it takes for half of a compound to be cleared from the body.
Evidence level: The category of human evidence behind a compound, from preclinical through to approved. Stated on every profile here as a category, not an adjective.
Peptide: A short chain of amino acids: the same building blocks as a protein, in a chain short enough to behave differently.
Protocol: One compound, with a dose, a frequency and a length: the plan, as opposed to what was actually taken.

The whole glossary →

Quick reference

Commonly described dose: 1 mg–3 mg
How often: Every 2 to 4 weeks
Route: Subcutaneous
Where: Abdomen, Thigh
Timing: Dosed every two to four weeks in the trial. The long half-life is the point and the problem: an effect that is unwanted cannot be withdrawn quickly.
Storage once mixed: Refrigerated, 14 days

These describe what sources report, not what you should do. Full detail and provenance in the dosing section below.

Price index

$138.95 – $173.00per mg

Across 3 vendors, normalised per milligram and confirmed by a person.

Confirmed listings for this compound, cheapest per milligram first.
Vendor	Size	Price	Per mg
Direct Peptides	1 mg	£76.74	$76.74
Swiss Chems	1 mg	$138.95	$138.95
Biotech Peptides	1 mg	$161.00	$161.00
Core Peptides	1 mg	$173.00	$173.00

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Ranked on price alone. We sell nothing, take no payment for placement, and use no affiliate links — listing a price is not a recommendation to buy. Prices are what the vendor listed when we last looked, not a live quote.

What it is studied for

Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.

Muscle mass in Duchenne muscular dystrophy

Clinical trial

The indication it was actually developed for.

EvidenceIn the phase 2 trial, trends toward maintained six-minute walk distance, increased lean mass and bone mineral density, and reduced fat mass. None reached statistical significance, and the trial was stopped early before it could.

Muscle growth in healthy people

Clinical trial

What it is sold for.

EvidenceNo trial has ever tested ACE-031 for athletic or cosmetic muscle gain. The healthy-adult exposure was a phase 1 safety study, and the vascular adverse events appeared there too.

Regulatory status — United States

Never approved anywhere. Development was halted in 2011 on safety grounds and permanently discontinued in 2013. Prohibited in sport at all times by WADA as a myostatin inhibitor. Material sold as a research chemical is not the clinical product and carries none of the trial's monitoring.

Last reviewed 1 Sept 2026. Regulatory positions in this category change frequently; we date this line so you can see how current it is.

Identity and clearance

Molecule

Class: Fc fusion protein, activin receptor type IIB ligand trap
Molecular weight: 110000 Da

A recombinant glycoprotein of roughly 110 kDa, not a synthetic peptide. It cannot be made by solid-phase synthesis, which is how most of this site's compounds are produced — it requires mammalian cell culture.

Dose protocols reported in sources

Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.

Dose protocols reported in sources, with the source of each.
Goal	Dose	Frequency	Route	Units, 1 mg vial	Source	Start this protocol
Dose used in the phase 2 trial	1 mg – 3 mg	Every 2 to 4 weeks	SubcutaneousPer kilogram in the trial, in boys, with haematological monitoring and a stopping rule that was used. Reproduced to show what a supervised dose looked like, not as a protocol.	from 100 u	Clinical trial	Start this

Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.

Safety

Reported effects

NosebleedsClinical trial
The reason the trial stopped
Epistaxis appeared in both healthy adults and in the boys with Duchenne. It resolved fully on stopping.
TelangiectasiaClinical trial
The reason the trial stopped
Small dilated blood vessels visible in the skin. Together with the nosebleeds this indicated an off-target effect on the vasculature, most likely through activin signalling the trap does not distinguish from myostatin.
Gum bleedingClinical trial
Reported
Part of the same bleeding picture.
Immune response against the proteinPublished review
Unknown outside the trial
Injected recombinant proteins can provoke antibodies against themselves. Where the protein resembles something the body makes, those antibodies can in principle cross-react. This is a class risk that short synthetic peptides do not carry.

When to stop

Any nosebleed, bleeding gums, or unusual bruising.
New small dilated vessels appearing in the skin.
Any allergic response: rash, hives, facial swelling or difficulty breathing. Seek urgent care.
Note that stopping does not clear it quickly. The half-life is measured in weeks.

Interactions and situations that need care

Any bleeding disorder, or anticoagulant useAvoid
The adverse events that ended clinical development were bleeding and vascular. Adding an anticoagulant to that is the obvious way to make it worse.
Pregnancy and breastfeedingAvoid
The trap blocks GDF-11 and activins alongside myostatin, and those signals are central to development.
Competing in a tested sportAvoid
Myostatin inhibitors are prohibited at all times by WADA. This is a sanction, not a health warning.
Using it at allUse caution
A drug company stopped giving this to children with a fatal muscle-wasting disease because of what it did to their blood vessels. That is a stronger signal than an absence of data.

What to expect

The muscle effects in the trial were trends, not significant findings — the trial stopped before it could establish them.
It was stopped for nosebleeds and telangiectasias, which resolved on discontinuation but indicated an off-target vascular effect.
Development was permanently discontinued in 2013 and never resumed.
The trap is not selective: it blocks activins and GDF-11 as well as myostatin, which is the most likely reason for the vascular events.
The half-life is weeks, so an unwanted effect cannot be stopped quickly.
It is a recombinant glycoprotein, not a synthetic peptide, and correct folding is not something a buyer can verify.

Storage and handling

Freeze-dried powder: Refrigerated at 2–8 °C, protected from light. Do not freeze the clinical formulation.
After mixing: Refrigerated at 2–8 °C. Proteins of this size are more fragile than short peptides — avoid shaking, which denatures them.
Long-term, frozen: Repeated freezing and thawing damages proteins of this class.

Printable one-pager How to reconstitute a vial, step by step

Checking your vial

Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it. More on assessing quality and COAs.

No certificate of analysis
For a recombinant protein this matters more than for a synthetic peptide: identity, purity and correct folding are all separate questions, and none is visible.
Cloudiness or visible particles once mixed
Aggregation. Large proteins aggregate readily when shaken or warmed, and aggregates are the form most associated with immune reactions against injected proteins.

Questions

Why was the trial stopped if the drug was working?: Because what it was doing to blood vessels mattered more than what it was doing to muscle. Participants developed nosebleeds and small dilated skin vessels. Everything resolved when dosing stopped, but the signal pointed at an off-target effect nobody had anticipated, in a trial of children. The muscle findings were only trends at that point anyway.
Is this the same as follistatin or myostatin peptides sold elsewhere?: No. Those are different molecules with different mechanisms and different evidence. ACE-031 is a receptor decoy — it intercepts the signal rather than blocking the receptor, and it intercepts several signals at once.
Is it detectable in doping tests?: Myostatin inhibitors are on the WADA prohibited list at all times, and methods for detecting activin receptor traps have been published. Assume yes.

References

Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: results of a randomized, placebo-controlled clinical trial
Muscle & Nerve, 2017 · Randomised, double-blind, placebo-controlled, multiple ascending dose
Ambulatory boys with Duchenne muscular dystrophy · Subcutaneous, every 2 to 4 weeks
Stopped after the second dosing regimen because of epistaxis and telangiectasias. No serious or severe adverse events were recorded. Trends toward maintained six-minute walk distance, increased lean mass and bone mineral density and reduced fat mass, none statistically significant. Development was discontinued permanently in 2013.
10.1002/mus.25268

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Keep this page honest

If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.

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This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice. No clinician reviews these pages.

Page last updated 1 Sept 2026