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№ 045

ACE-031 (ACVR2B-Fc)

A muscle-building drug that blocks the body's brake on muscle, shelved over safety. A soluble activin receptor IIB fused to Fc that traps myostatin and related TGF-β ligands. Acceleron developed it; Phase 2 dosing was halted in 2011 over vascular safety signals (program permanently discontinued 2013).

GH-axis
Evidence: Limited

ACE-031 (ACVR2B-Fc): A muscle-building drug that blocks the body's brake on muscle, shelved over safety. A soluble activin receptor IIB fused to Fc that traps myostatin and related TGF-β ligands. Acceleron developed it; Phase 2 dosing was halted in 2011 over vascular safety signals (program permanently discontinued 2013). ACE-031 was an anti-myostatin drug Acceleron tested for muscle-wasting diseases.

FDA ⓘ
Not approved
WADA
Banned
Typical dose
Trial doses ranged 1-3 mg/kg
Half-life ⓘ
~10-15 days
Route ⓘ
Subcutaneous
Schedule
Once weekly to once monthly in trials
In plain English

ACE-031 was an anti-myostatin drug Acceleron tested for muscle-wasting diseases. They halted Phase 2 in 2013 because some patients developed nosebleeds and visible capillaries. Educational reference, there's no safe community protocol, just the trial history.

Status & legalityWhat do these mean? →
Natty? ⓘ
Not natty

Anti-myostatin therapy is universally banned in tested sport.

FDA ⓘ
Not approved

Not FDA approved. Acceleron halted Phase 2 in 2013 due to vascular safety signals.

Compounding ⓘ
Not classified

Not formally categorized in the FDA bulks lists.

WADA ⓘ
Banned (S4)

S4 myostatin inhibitors are explicitly listed.

Prescribed ⓘ

Not prescribed. Development discontinued.

Who it's for

  • →Researchers studying myostatin pathway
  • →Educational reference, not for active use
  • →Followers of muscle-wasting drug development history

What to expect

  1. Week 1

    Early reports describe muscle volume increase within days.

  2. Week 4

    Trial endpoint for some Phase 1 cohorts. Safety signals emerged here.

  3. Week 8

    No long-cycle human safety data, Acceleron halted further dosing.

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How it works (mechanism)

Soluble activin receptor IIB fused to immunoglobulin Fc. Acts as a decoy receptor that traps myostatin and other TGF-β superfamily ligands before they can activate native receptors on muscle cells, removing the brake on muscle growth.

Dosing protocol

Members only

Stacks well with

Members only

Side effects

01Epistaxis (nosebleeds), Phase 2 signal that halted development
02Telangiectasias (dilated capillaries near skin)
03Headache
04Theoretical: cardiac and tendon issues with strong myostatin suppression

When NOT to use

  • ⚠All, no current safe-use protocol exists
  • ⚠Pregnancy / nursing
  • ⚠Active malignancy

Bloodwork to monitor

  • • CBC if researching
  • • BUN / creatinine

Common mistakes

  • • Treating it as a drop-in Follistatin replacement (different mechanism, much longer half-life)
  • • Ignoring the halt history
  • • Assuming community-vendor product matches Acceleron's clinical material

What it actually is

ACE-031 is a laboratory-built decoy: the business end of the activin receptor IIB fused to an antibody fragment, so it circulates in the blood and traps myostatin before myostatin can reach real receptors on muscle. It was a serious pharmaceutical programme from Acceleron, tested in Duchenne muscular dystrophy. Dosing was halted in 2011 over vascular safety findings and the programme was discontinued permanently in 2013. That history is the most important thing on this page.

Muscle growth is limited by myostatin and related ligands signalling through the ActRIIB receptor. ACE-031 is a soluble copy of that receptor, so it soaks up those ligands in the bloodstream. It works, in the sense that muscle mass increases. The problem is that ActRIIB does not only bind myostatin: it binds a family of related signals, and some of those are involved in maintaining blood vessels. That is the leading explanation for what stopped the trials — nosebleeds and telangiectasias, small dilated vessels visible at the skin surface.

Forms, and which is which

Clinical trial material (discontinued)Historical reference

Acceleron's product, dosed by weight in trials at 1 to 3 mg/kg. No longer in development.

Verdict: The only material that was ever characterised, and it no longer exists as a programme.

Products sold as ACE-031Nothing

A large Fc-fusion protein sold as a research chemical. Whether such a product is correctly folded and active cannot be assessed by the buyer, and there is no reference product to compare against.

Verdict: The hardest molecule class to verify, for a drug that was withdrawn for safety.

Follistatin 344The other myostatin approach

Binds myostatin directly rather than acting as a receptor decoy. Also carries documented harms in users.

Verdict: Same target, different mechanism, also unsafe on current evidence.

Approved activin-pathway drugsThe legitimate descendants

Related molecules from the same family went on to approval in other diseases, which is why the pathway research continued even though this drug did not.

Verdict: The science survived; this compound did not.

What it is claimed to do, graded

Increases muscle massModerate

Trials did show increases in lean mass and this is the least contested claim about it. It is also why the safety findings matter — it was stopped despite working.

Preserves muscle in wasting conditionsLimited

The animal literature is substantial: cancer cachexia, chemotherapy-induced muscle and bone loss, cardiac protection after ischaemia. Two human trial records are indexed.

Is safeNone shown

Phase 2 dosing was halted in 2011 over epistaxis and telangiectasias, and the programme was permanently discontinued in 2013. This is not an absence of data, it is a negative safety finding.

Community-sourced product matches clinical materialNone shown

There is no basis for assuming this. A correctly folded Fc-fusion protein is not something a research-chemical supply chain reliably produces.

Grades describe how much human evidence exists for that specific claim, not whether it will work for you or whether it is safe.

Pros and cons

Pros
  • • The mechanism works — muscle mass genuinely increased in trials
  • • A real pharmaceutical development history, so the risks are documented rather than guessed
  • • Very long half-life, so dosing would be infrequent
  • • The underlying pathway research led to genuinely useful drugs elsewhere
Cons
  • • Development halted over vascular safety signals and permanently discontinued
  • • Nosebleeds and dilated surface capillaries were the specific findings
  • • No safe community dose exists, because no safe dose was established at all
  • • An Fc-fusion protein from an unregulated supplier is unverifiable
  • • Banned in sport

When to stop

  • • Any nosebleed, or new visible small red vessels on the skin — these are the specific findings that stopped the trials
  • • Any unusual bruising or bleeding
  • • Tendon or joint pain as strength climbs
  • • Any new cancer diagnosis

Interactions

Follistatin or other myostatin inhibitorsAvoid

Same pathway, compounded off-target suppression.

Anticoagulants and antiplatelet drugsAvoid

The halting safety signal was bleeding-related. Adding anything that impairs clotting is the wrong direction.

Active or suspected cancerAvoid

Broad TGF-beta family suppression in a body with a tumour is unstudied in either direction.

Anabolic steroidsCaution

Commonly stacked, makes any effect unattributable, and does nothing about the vascular concern.

Nothing well characterised in current useCaution

There is no interaction literature for non-trial use, because there is no legitimate non-trial use.

Is this for you?

Probably worth reading further if
  • • Nobody. This is on the site as a reference for a myostatin programme that was stopped for cause, not as an option
Skip it if
  • • You are considering using it at all — the trials were halted over bleeding, in supervised patients, with characterised material
  • • You take anticoagulants or antiplatelet drugs
  • • You have active cancer
  • • You are pregnant, nursing, or drug-tested in sport

The one number

Phase 2 dosing halted 2011 over vascular safety; programme permanently discontinued 2013
Acceleron development history; Pepdex evidence index, 2 indexed human-trial records

Sources for the claims above

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AI Coach, live sample
Member answer
is 250mcg of bpc enough for a knee injury?
For a knee, is the standard working dose and a solid place to start. The trick with BPC is consistency, give it weeks, not days. , run it , and don't drop below , results tend to fall off under that line. If nothing's moved by week 3, that's when earns its place.
how much bac water for a 10mg reta vial?
is the standard play for a 10 mg reta vial. That gives you , clean unit math across the whole titration: on a 100-unit insulin syringe. Run instead if you want fewer, more concentrated shots. Most people titrate up over , and that mix keeps the numbers cleanest.
what should i track on bloodwork for tirzepatide?
Lipid panel, ALT/AST (liver enzymes), and an A1C, baseline before you start then every 3 months. If you've got metabolic-syndrome history, add fasting glucose and insulin so you can actually watch insulin sensitivity improve. You don't need a big hormone panel for a GLP-1.

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Frequently asked

What is ACE-031 (ACVR2B-Fc)?+
ACE-031 was an anti-myostatin drug Acceleron tested for muscle-wasting diseases. They halted Phase 2 in 2013 because some patients developed nosebleeds and visible capillaries. Educational reference, there's no safe community protocol, just the trial history.
Is ACE-031 (ACVR2B-Fc) FDA approved?+
Not FDA approved. Acceleron halted Phase 2 in 2013 due to vascular safety signals.
Is ACE-031 (ACVR2B-Fc) legal?+
ACE-031 (ACVR2B-Fc) is not FDA-approved, so there is no approved prescription version. Most supply is sold as "research only" by peptide vendors. A compounding pharmacy may only use substances the FDA permits for compounding, and many research peptides are not permitted — do not assume a compounded prescription is available. Possession is generally not criminalized but distribution without authorization may be. Verify local laws.
Is ACE-031 (ACVR2B-Fc) banned by WADA?+
ACE-031 (ACVR2B-Fc) is on the WADA prohibited list under Banned (S4). S4 myostatin inhibitors are explicitly listed.
Are you still natty after taking ACE-031 (ACVR2B-Fc)?+
No. Anti-myostatin therapy is universally banned in tested sport.
Do doctors prescribe ACE-031 (ACVR2B-Fc)?+
Not prescribed. Development discontinued.
What's the typical dose of ACE-031 (ACVR2B-Fc)?+
Dosing depends on your goal, experience, and tolerance. The full ACE-031 (ACVR2B-Fc) protocol (dose, frequency, and how to titrate) is in the members section on the entry page.
What are the side effects of ACE-031 (ACVR2B-Fc)?+
Common side effects include: Epistaxis (nosebleeds), Phase 2 signal that halted development; Telangiectasias (dilated capillaries near skin); Headache; Theoretical: cardiac and tendon issues with strong myostatin suppression. Less common effects and full safety details are on the entry page.
How long until ACE-031 (ACVR2B-Fc) starts working?+
Early reports describe muscle volume increase within days.
What can you stack with ACE-031 (ACVR2B-Fc)?+
ACE-031 (ACVR2B-Fc) is commonly combined with complementary compounds. The full stacking protocol (what to pair, dosing, and timing) is in the members section on the entry page.
Where do people get ACE-031 (ACVR2B-Fc)?+
Pepdex does not sell, ship, or recommend suppliers. ACE-031 (ACVR2B-Fc) is not FDA-approved; prescription versions require licensed clinical care, and "research only" markets carry real legal and quality risks. /coa explains how to verify a Certificate of Analysis and /guides/scam-vendor-spotting covers the red flags.

Common questions about ACE-031 (ACVR2B-Fc)

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