Human studiesMyostatin and activin trap (decoy receptor)

ACE-031

Ramatercept (INN), ActRIIB-Fc, soluble activin receptor type IIB

Common dose: Trial doses only
Cycle: No set cycle
Form: In trials only

A manufactured protein that pairs the catching part of the activin receptor type IIB with an antibody tail, so it circulates and soaks up myostatin and related signals before they can reach muscle and tell it to stop growing. Blocking them builds muscle.

Evidence. Tested in people, then dropped. Single injections in 48 healthy postmenopausal women raised lean body mass by 3.3% and thigh muscle volume by 5.1% after a month at the top dose (2013). A randomized placebo-controlled trial in boys with Duchenne muscular dystrophy was stopped after its second dosing round because of nosebleeds and small widened blood vessels in the skin, with muscle and walking results that were trends only; no trial has been registered since 2010 and nothing is approved anywhere.

What it’s used for

None of these uses is approved. Uses tested in people come first, then claims that rest on animal studies or user reports.

Building muscle mass: TrialOne injection raised lean body mass 3.3% and thigh muscle volume 5.1% after a month in 48 healthy postmenopausal women, at the top dose only. Strength wasn’t measured.
Duchenne muscular dystrophy in children: TrialStopped early: in 24 boys, lean mass, bone density and walking distance trended better than placebo but missed significance, and nosebleeds and skin vessel changes ended the program.
Muscle wasting and frailty: AnimalUnproven in people beyond the single-dose trial. Related activin-receptor traps built muscle in animals, and no trial in muscle wasting or frailty was completed.
Strength and athletic performance: No studyNo study has measured strength, power or performance. It is banned in sport at all times, and most products sold as ACE-031 are a different protein.
Bone density: TrialBlood markers of bone metabolism shifted in the single-dose trial and bone density trended up in the Duchenne trial, but no trial tested fractures or bone disease.
Fat loss: TrialFat mass trended down in the Duchenne trial and fat-metabolism markers shifted in the single-dose trial. No trial set out to test fat loss.

Trial: tested in people, with the result. Animal: cell or animal studies only. No study: nothing published supports it.

Every compound’s uses, by body system: evidence map, and by condition: conditions A to Z.

Status

Approval: Not approved as a drug in the US, the EU or anywhere else. Two phase 2 trials in Duchenne muscular dystrophy were terminated in 2011 on preliminary safety data, and no trial of ACE-031 has been registered since.
US compounding: Never nominated for pharmacy compounding, so it appears on none of FDA’s 503A or 503B bulk substance category lists (503A list updated May 14, 2026).
European Union: No marketing authorization; development stopped in 2011 and no ACE-031 product is approved anywhere.
United Kingdom: No marketing authorization (MHRA).
Canada: No marketing authorization, though the Duchenne trials ran at Canadian hospitals.
Australia: No marketing authorization. The Poisons Standard (October 2026) doesn’t name ACE-031; follistatin, a related myostatin blocker, is in Schedule 4 and Appendix D.
Sport (WADA 2026): Banned in sportS4.3 agents preventing activin receptor IIB activation: activin receptor IIB competitors, with “decoy activin receptors (e.g. ACE-031)” named. Banned at all times, as a non-Specified substance.

Category 2 is FDA’s list of bulk substances that may present significant safety risks in compounding. The 503A bulks list adds substances that pharmacies may compound with. Advisory committee votes are advice; FDA makes the final decision. Sport status follows the WADA Prohibited List in force since January 1, 2026; athletes should confirm with their anti-doping organization. Checked October 5, 2026. Status outside the US checked October 7, 2026 against EMA, MHRA, Health Canada and TGA records. By country: EU, UK, Canada, Australia. Status of every compound.

How it works

TrialMainly from studies in people.

Not known

Why it caused nosebleeds and widened skin blood vessels was never explained, and whether muscle gains translate into strength or function in people was never shown: the Duchenne results were trends only.

Protocol

Trial

Attie 2013

Single injections under the skin of 0.02 to 3 mg per kg in 48 healthy postmenopausal women. Muscle gains showed up only in the 3 mg per kg group.

Trial

NCT00952887

A second phase 1 trial gave 70 healthy postmenopausal women aged 45–75 either 2–3 injections over a month or 7 over 3 months. Results were never published.

Community

No established dose. It is sold on the black market, but when researchers analyzed 14 such products in 2025, not one contained ACE-031.

Frequency: Single dose, or every 2–4 weeks in trials
Route: Subcutaneous injection (in clinical trials only)
Cycle: No established cycle. The adult trials ran a single dose, a month, or 3 months.
No set cycle, shown over 26 weeks

Common protocols

The ways ACE-031 is most often run, each tagged with where it comes from.

Single-dose phase 1

Trial

Dose: 0.02–3 mg per kg, one injection
How often: Once
How long: Followed about a month

48 healthy postmenopausal women, randomized 3:1 against placebo. Lean mass and thigh muscle volume rose only in the 3 mg per kg group.

Repeat-dose phase 1

Trial

Dose: Eight dosing groups; amounts not published
How often: 2–3 injections over a month, or 7 over 3 months
How long: 1 or 3 months

70 healthy postmenopausal women aged 45–75. Completed in February 2011, with no results published or posted.

Dosing by body weight

Trial

20–3,000 mcg/kg. 0.02 to 3 mg per kg as a single injection under the skin in 48 healthy postmenopausal women (Attie 2013). Muscle gains appeared only at 3 mg per kg.

Taking it

Where it goes

Injection under the skin, given in hospital or clinic by trial staff. No other route has been tested.

If you miss a dose

No published guidance, and no established schedule: the protein was only ever given inside trials.

Missed doses for every compound

What to expect

29 days after one injection, healthy postmenopausal women
Total body lean mass rose 3.3% and thigh muscle volume 5.1% in the 3 mg per kg group, both just reaching significance. Blood markers also suggested changes in bone and fat metabolism.
Trial
Over the Duchenne trial
Lean mass and bone mineral density trended up and fat mass down, and walking distance held steady while the placebo group declined, but none of it reached statistical significance.
Trial
After the second dosing round, Duchenne trial
Nosebleeds and small widened blood vessels in the skin appeared, and the trial was stopped. No serious or severe adverse events were recorded.
Trial

Side effects and what to do

Nosebleeds and telangiectasias, small widened blood vessels in the skin

These stopped the Duchenne program. Any new nosebleeds or spidery skin vessels are a reason to seek medical advice.

Redness at the injection site

The main side effect in the single-dose trial in healthy women.

Effects beyond muscle, on bone and fat

Blood markers of bone and fat metabolism shifted in the single-dose trial. What that means long-term was never established.

Unknown with longer use

The longest adult exposure was 3 months and was never published. Nothing is known beyond that.

Reaction to the wrong protein entirely (black-market vials)

Of 14 products tested in 2025, none held ACE-031; most held full-length activin receptor IIB plus other proteins. Injecting unknown proteins can set off immune reactions.

Stop and get medical help

A nosebleed that won’t stop, or sudden spidery red marks on the skin, needs medical advice. Hives with face or throat swelling or trouble breathing after an injection is an emergency.

Can it cause …?

The side effects people ask about most, answered one by one. Each answer says where it comes from.

Tiredness: Not reportedNot reported in the single-dose trial in 48 women; the Duchenne trial recorded no serious or severe adverse events before it was stopped.
Hair loss: No dataNo human data: hair wasn’t reported in either published trial.
Acne, rash or skin changes: TrialYes. Telangiectasias, small widened blood vessels visible in the skin, appeared in the Duchenne trial and were part of why it stopped. Injection-site redness was common in adults.
Water retention or swelling: No dataNo human data: swelling wasn’t reported in either published trial.
Joint or muscle pain: No dataNo human data: joint or muscle pain wasn’t reported in either published trial.
Anxiety, low mood or irritability: No dataNo human data: mood wasn’t measured in either published trial.
Low or high blood sugar: No dataNo human data on blood sugar, though fat-metabolism markers changed in the single-dose trial.
Fast heartbeat or blood pressure changes: No dataNo human data on heart rate or blood pressure. In mice, a related activin-receptor trap improved heart muscle function in disease models.
More hunger: No dataNo human data: appetite wasn’t measured in either published trial.
Liver strain: No dataNo human data: liver tests weren’t reported in either published trial.
Kidney problems: No dataNo human data: kidney tests weren’t reported in either published trial.
Cancer risk: PrecautionUnknown. It removes a brake on tissue growth, and no study has looked at cancer risk in animals or people.
HeadacheNausea or vomitingDiarrhea or constipationDizzinessTrouble sleeping: Not reportedNot reported in the published trials.

Trial: reported in human studies. Precaution: a concern that follows from how it works or from a related drug, not measured. Not reported: studied in people and not reported. No data: no human safety data. A side effect that hasn’t been reported can still happen, especially with long or high-dose use. Any of these across every compound: the side-effect finder.

Who should avoid it

No product label covers ACE-031, so these come from human studies and from precautions based on how it works. Most important first.

Anyone with a bleeding or blood-vessel disorder: TrialNosebleeds and small widened blood vessels in the skin appeared in the Duchenne trial and ended the program.
Anyone on blood thinners: PrecautionNever studied alongside them, and the one safety signal that stopped development was bleeding from the nose.
Pregnancy or breastfeeding: PrecautionNo human safety data. Only postmenopausal women and boys were ever enrolled, so pregnancy was never studied.
Anyone with active or past cancer: PrecautionIt blocks signals that limit tissue growth and is related to drugs used in blood disorders. No study has tested what it does in cancer.
Anyone relying on product quality: TrialOf 14 black-market products analyzed in 2025, none contained ACE-031; most held a different activin-receptor protein plus others. Injecting unknown proteins can trigger immune reactions.

Interactions

No interaction studies have been published, and no product label exists. The Duchenne trial was run alongside the steroids those boys were already taking, but no interaction was measured.

Trial: seen in human studies, or a group those studies left out. Precaution: follows from how it works or from a related drug, and hasn’t been tested. This isn’t a complete list: a pharmacist or doctor can check a specific medicine or condition. Every documented interaction, by medicine: drug interactions.

Special situations

What’s known about pregnancy, breastfeeding, kidney and liver problems, age and surgery. Where nothing has been studied, the row says so.

Pregnancy: PrecautionNo human safety data. The adult trials enrolled only postmenopausal women, so pregnancy was never studied, and the signals it blocks matter in development.
Breastfeeding: PrecautionNo human data; it isn’t known whether it passes into breast milk.
Kidney problems: PrecautionNot studied in kidney disease. As a large antibody-type protein it isn’t cleared by the kidneys, but nothing was measured.
Liver problems: PrecautionNot studied in liver disease.
Older adults: TrialOnly tested in postmenopausal women aged 45–75, as single doses or over 1–3 months. Nothing longer was published.
Children and teens: TrialNot approved at any age. Trials in boys with Duchenne muscular dystrophy were stopped in 2011 over nosebleeds and skin blood vessel changes; Vial Guide doesn’t publish children’s doses.
Surgery and anesthesia: PrecautionNo data, and it lingers for weeks: its half-life is 10–15 days. Nosebleeds were its main safety signal, so tell the surgical team about any injected compound.

Trial: from human studies. Precaution: not studied, so the caution follows from how it works or from a related drug. Ages are given as approved or studied; this site never gives doses for children. Across every compound: pregnancy, breastfeeding, kidney disease, liver disease, older adults and surgery.

Tracking and pairing

Worth tracking

Nosebleeds and skin blood vessels
Blood count and hemoglobin
Injection sites

Often paired with

Follistatin-344
Both block myostatin, the brake on muscle growth, so the pair would double up on one pathway. No study has combined them, and both are banned in sport under the same section.

Human studies

2 key published human studies, with how many people took part. Animal studies aren’t listed here.

201348 people

At 3 mg per kg, total body lean mass rose 3.3% (p=0.03) and thigh muscle volume 5.1% (p=0.03); generally well tolerated, with injection-site redness; half-life 10–15 days.

Design
Randomized, double-blind, placebo-controlled single ascending-dose phase 1 trial (3:1 against placebo)
Dose
One injection under the skin, 0.02 to 3 mg per kg
Length
Followed about 29 days

Attie et al., Muscle Nerve 2013, PMID 23169607
201724 people

No serious or severe adverse events, but nosebleeds and widened skin blood vessels led to stopping. Lean mass, bone density and walking distance trended better than placebo without reaching significance.

Design
Randomized, double-blind, placebo-controlled ascending-dose phase 2 trial in ambulatory boys, stopped early
Dose
Vial Guide doesn’t publish children’s doses
Length
Stopped after the second dosing round

Campbell et al., Muscle Nerve 2017, PMID 27462804

All human studies on Vial Guide

Trials under way

No ongoing trial of ACE-031 is registered, and none has finished recently without publishing its results. Checked on ClinicalTrials.gov, October 7, 2026. Every compound: trials under way.

Limits of the evidence

The published human evidence is two trials. One gave a single injection to 48 healthy postmenopausal women and measured muscle a month later, so it says nothing about repeated use, men or younger adults. The other, in 24 boys with Duchenne muscular dystrophy, stopped after its second dosing round, with muscle and walking findings that were trends missing significance. A 70-woman repeat-dose trial finished in 2011 and was never published, so nothing is known about longer use, strength or function.

How it’s supplied

Single injections under the skin of 0.02–3 mg per kg in a 48-woman phase 1 trial; up to 7 injections over 3 months in a second. Not sold. Injected under the skin by trial staff, as a single dose or every few weeks over 1–3 months. Development stopped, so nobody is given it now. It’s available only in clinical trials, so the calculator and dose log don’t apply.

Datasheet

Half-life: 10 to 15 days TrialMean terminal half-life after a single injection under the skin in healthy postmenopausal women, across doses of 0.02 to 3 mg per kg. Exposure rose in step with the dose.
Type: Protein
Molecular weight: about 58 g/mol kDa per chain on a gel; the drug is a dimer of two such chains
Storage before use: No approved label exists. Fc-fusion proteins of this kind are normally refrigerated at 2–8 °C and not frozen.
After mixing or opening: Same: refrigerated, used soon after dilution.

Half-life: Attie et al., Muscle Nerve 2013, PMID 23169607
Molecule: FDA GSRS UNII 42HQC6QLEK (ramatercept, CAS 1169766-01-1, INN 9606, DrugBank DB15116): the extracellular part of human activin receptor type IIB joined through a three-glycine link to the Fc tail of human IgG1, as a dimer. The 58 kDa figure is the gel measurement reported by Reichel et al. 2025
Storage: Community General practice for antibody-type proteins; no label or trial storage instruction is public

Every compound side by side: the half-life chart and the storage chart.

Identifiers

CAS number: 1169766-01-1
UNII (FDA): 42HQC6QLEK
DrugBank: DB15116
ATC code: None assigned
Development codes: ACE-031, ramatercept (INN 9606), USAN YY-125, ActRIIB-Fc
Brand names: None; no product is approved anywhere
First described: Developed by Acceleron Pharma, Cambridge, Massachusetts; first human trial began in September 2008.

Every compound’s numbers: the identifiers table.

Product form and quality

Most of what is sold isn’t this molecule: of 14 black-market products analyzed in 2025, 2 held no activin-receptor protein and 12 held full-length activin receptor IIB without the antibody tail, plus many other proteins. Nothing regulates identity or sterility.

Cautions

The Duchenne trial was stopped early over nosebleeds and telangiectasias, small widened blood vessels visible in the skin. The sponsor judged these unrelated to muscle, and they ended the program.
Development stopped after 2011 and the protein has never been approved anywhere, so no regulator has ever reviewed its safety.
What is sold as ACE-031 is usually not ACE-031. Of 14 black-market products analyzed in 2025, 2 contained no activin-receptor protein at all and the other 12 contained full-length activin receptor IIB instead of the Fc fusion, alongside many other proteins.
It blocks signals that also act on blood vessels, bone and fat. The nosebleeds and skin vessel changes are the clearest sign that its effects are not limited to muscle.
Banned in sport at all times: the 2026 Prohibited List names ACE-031 by name under S4.3 as a decoy activin receptor.

Questions

What is ACE-031?

How does ACE-031 work?

Muscle growth is held back by myostatin and related signals that work through the activin receptor type IIB on muscle cells. ACE-031 is the catching end of that receptor, made in the laboratory and joined to an antibody tail so it stays in the blood for weeks. It mops those signals up before they reach muscle, and the brake comes off. The same signals act on bone, fat and blood vessels, so the effect is not confined to muscle. Why it caused nosebleeds and widened skin blood vessels was never explained, and whether muscle gains translate into strength or function in people was never shown: the Duchenne results were trends only.

Is ACE-031 FDA-approved?

Not approved as a drug in the US, the EU or anywhere else. Two phase 2 trials in Duchenne muscular dystrophy were terminated in 2011 on preliminary safety data, and no trial of ACE-031 has been registered since. Never nominated for pharmacy compounding, so it appears on none of FDA’s 503A or 503B bulk substance category lists (503A list updated May 14, 2026).

What is the usual ACE-031 dose?

From human studies (Attie 2013): Single injections under the skin of 0.02 to 3 mg per kg in 48 healthy postmenopausal women. Muscle gains showed up only in the 3 mg per kg group. NCT00952887: A second phase 1 trial gave 70 healthy postmenopausal women aged 45–75 either 2–3 injections over a month or 7 over 3 months. Results were never published. These are the amounts sources reference, not recommendations.

How is ACE-031 given?

Injected under the skin by trial staff, as a single dose or every few weeks over 1–3 months. Development stopped, so nobody is given it now. It isn’t sold: it’s available only in clinical trials.

Who should avoid ACE-031?

No product label covers ACE-031, so these come from human studies and from precautions based on how it works. Anyone with a bleeding or blood-vessel disorder: Nosebleeds and small widened blood vessels in the skin appeared in the Duchenne trial and ended the program. Anyone on blood thinners: Never studied alongside them, and the one safety signal that stopped development was bleeding from the nose. Pregnancy or breastfeeding: No human safety data. Only postmenopausal women and boys were ever enrolled, so pregnancy was never studied. The “Who should avoid it” section lists 2 more groups.

What is the half-life of ACE-031?

10 to 15 days, measured in human studies. Mean terminal half-life after a single injection under the skin in healthy postmenopausal women, across doses of 0.02 to 3 mg per kg. Exposure rose in step with the dose.

How should ACE-031 be stored?

Before mixing: No approved label exists. Fc-fusion proteins of this kind are normally refrigerated at 2–8 °C and not frozen. Same: refrigerated, used soon after dilution. This is common practice; no product label covers it.

Is ACE-031 banned in sport?

Yes. S4.3 agents preventing activin receptor IIB activation: activin receptor IIB competitors, with “decoy activin receptors (e.g. ACE-031)” named. Banned at all times, as a non-Specified substance.

Has ACE-031 been studied in people?

Yes. The human studies section lists 2 published studies. The largest, from 2013, included 48 people. At 3 mg per kg, total body lean mass rose 3.3% (p=0.03) and thigh muscle volume 5.1% (p=0.03); generally well tolerated, with injection-site redness; half-life 10–15 days.

How long has ACE-031 been studied in people?

Trial 3 months, in 70 healthy postmenopausal women; that trial finished in 2011 and was never published.

Does ACE-031 come in other forms, like a pill or nasal spray?

Trial Injected under the skin in every trial. No oral, nasal or skin form exists or has been tested; it is a large protein that the gut would destroy.

Can you drink alcohol while taking ACE-031?

No study No data. No study has looked at the two together.

Can ACE-031 be taken with semaglutide or tirzepatide?

Precaution No study has combined them. GLP-1 drugs cause some muscle loss alongside fat loss, which is why activin-receptor traps are now being trialed with them, but not this one.

What happens if you take too much ACE-031?

Trial No label and no overdose data. Doses up to 3 mg per kg were given once in trials, and it lingers for 10–15 days, so effects wouldn’t be quickly reversible. Call Poison Help (1-800-222-1222), or emergency services for severe symptoms.

Sources

Attie et al., single ascending-dose trial of ACE-031 in 48 healthy postmenopausal women (Muscle Nerve 2013) PMID 23169607
Campbell et al., randomized placebo-controlled trial of ACE-031 in ambulatory boys with Duchenne muscular dystrophy, stopped early (Muscle Nerve 2017) PMID 27462804
Reichel et al., analysis of 14 black-market ACE-031 products, none containing ACE-031 (Drug Test Anal 2025) PMID 40312924
ClinicalTrials.gov records NCT00755638, NCT00952887, NCT01099761 and NCT01239758
WADA 2026 Prohibited List, S4.3 agents preventing activin receptor IIB activation
FDA GSRS UNII 42HQC6QLEK (ramatercept, INN 9606)

For the protocol details

ClinicalTrials.gov records NCT00952887 (70 women, completed, no results posted) and NCT01239758 (extension, terminated)

For how it works, who should avoid it and the limits of the evidence

ClinicalTrials.gov records NCT00755638, NCT00952887, NCT01099761, NCT01239758

For uses, the side-effect questions, special situations, trials, identifiers and status outside the US

Li et al., a related activin-receptor trap in mouse models of neuromuscular disease and heart muscle disease (J Clin Invest 2021) PMID 33586684
ClinicalTrials.gov records NCT00755638, NCT00952887, NCT01099761, NCT01239758 (checked October 8, 2026)
FDA GSRS UNII 42HQC6QLEK (ramatercept); WADA 2026 Prohibited List, S4.3
Australian Poisons Standard, October 2026

Doses tagged Community come from public dosing guides and user reports, checked against at least two of them. Those sites aren’t named here because many of them sell peptides or earn commissions on them.

By Vial Guide editorsLast reviewed October 7, 2026

How we review