ACE-031

Last Updated: August 2026

ACE-031 is a recombinant fusion protein — the extracellular domain of the human activin receptor type IIB (ActRIIB) fused to the Fc portion of human IgG1 — developed by Acceleron Pharma as a muscle-building agent, primarily for Duchenne muscular dystrophy (DMD). It works as a circulating "ligand trap." Its clinical development was discontinued after vascular safety events, it was never approved, and it is supplied for research use only. It is a large biologic, not a small synthetic peptide.

What is ACE-031 and how does the ligand-trap mechanism work?

Myostatin and related TGF-β-superfamily ligands normally bind ActRIIB on muscle to restrain growth via SMAD2/3 signaling; ACE-031 is a soluble decoy version of that receptor that mops up those ligands in the bloodstream before they reach muscle, releasing the brake on growth. Because it traps multiple ligands at once — myostatin (GDF-8), activin A, GDF-11 and others — it is broader (and blunter) than selective anti-myostatin antibodies. That breadth is exactly what caused its problems (below).

What does the clinical evidence show?

A Phase 1 single-ascending-dose study in 48 healthy postmenopausal women showed that a single subcutaneous dose produced, at the highest dose, a statistically significant ~3.3% increase in lean body mass and ~5.1% increase in thigh muscle volume at day 29.1 source A Phase 2 randomized, double-blind, placebo-controlled ascending-dose study in ambulatory boys with Duchenne muscular dystrophy showed trends toward increased lean mass but was not associated with serious or severe adverse events; it was stopped after the second dosing regimen because of the vascular safety signals — epistaxis (nosebleeds) and telangiectasias (dilated blood vessels).1 source Evidence level: Phase 1 completed (healthy volunteers); Phase 2 terminated early (DMD); development discontinued.

Why was ACE-031 discontinued?

Because trapping ActRIIB ligands throughout the body also inhibited BMP9/BMP10 — ligands critical for blood-vessel remodeling — producing nosebleeds (epistaxis) and dilated skin vessels (telangiectasias) in trials, which led to termination. These events were reversible on stopping treatment, but Acceleron Pharma and its partner Shire ended the ACE-031 program in 2013 after additional nonclinical and toxicology work did not support further development. No ACE-031 product ever reached market or regulatory approval.2 sources Acceleron redirected toward more selective myostatin-pathway inhibitors. This is a documented safety story, not a footnote. Evidence level: Terminated Phase 2.

What are the safety concerns and regulatory status?

ACE-031 is not approved anywhere, is no longer in development, and carries a documented vascular safety signal; it is also prohibited in sport at all times — the WADA Prohibited List names ACE-031 by example under S4.3 (Agents Preventing Activin Receptor IIB Activation), as a "decoy activin receptor" (as of August 2026)1 source. Anyone encountering research-market ACE-031 should weigh both the counterfeit risk and that vascular signal. See the legal status guide.

Why does vendor verification matter, and how does Peptigrity verify?

As a discontinued recombinant biologic that never reached market, any "ACE-031" sold online is unapproved, unverified material — analytical testing (HPLC, mass-spec, and identity confirmation appropriate to a fusion protein) is the only objective check. Peptigrity collects independent third-party Certificates of Analysis for ACE-031 from shops' official channels and verifies each for authenticity before publishing. Because shops choose which COAs to publish, results reflect the batches shops have made public rather than every production batch — a selection bias we state openly. A community-funded Testing Grant to purchase and test vials anonymously is in development. Tests in the database come from independent labs such as Janoshik Analytical, Freedom Diagnostics, and Chromate; the trust score weights independent lab purity and community reviews equally (50/50). See the independent ACE-031 lab tests on file. See how to read lab results.

Educational information only; not medical advice. ACE-031 was discontinued in development over vascular safety events and is not approved. Any research-market material is unverified. Consult a qualified healthcare provider. Peptigrity does not sell, endorse, or recommend products or vendors.