ACE-031 Clinical Trial Results

What the ACE-031 trials tested

ACE-031 was an experimental myostatin inhibitor from Acceleron Pharma, developed with Shire, that reached two published human trials. Background is in our ACE-031 overview and our page on how ACE-031 works.

ACE-031 Overview

Mechanism

Feature	Description
Type	ActRIIB-IgG1 fusion protein
Target	Myostatin and related ligands
Action	Decoy receptor
Administration	Subcutaneous injection

Clinical Trial History

Phase 1 Studies

Aspect	Finding
Population	48 healthy postmenopausal women
Dose range	One dose, 0.02-3 mg/kg (trial doses)
Muscle effects	At 3 mg/kg: lean mass +3.3%, thigh muscle volume +5.1% at day 29
Fat effects	Biomarker changes only

These results are from Attie et al. (Muscle & Nerve, 2013), who found the drug generally well tolerated.

Phase 2 in DMD

Aspect	Finding
Population	24 walking boys with Duchenne muscular dystrophy
Trial doses	0.5 mg/kg every 4 weeks or 1.0 mg/kg every 2 weeks, for 12 weeks
Safety issue	Nosebleeds, gum bleeding
Vascular concern	Telangiectasias
Outcome	Terminated in 2011

Campbell et al. (Muscle & Nerve, 2017) reported no serious adverse events, but the study stopped after its second dose group over the bleeding findings. The companies said some healthy volunteers had the same minor events, which resolved after treatment stopped.

Efficacy Data

These DMD figures, which the paper calls trends, come from ClinicalTrials.gov (NCT01099761) about 24 weeks after the first dose.

Muscle Mass Effects

Measure	0.5 mg/kg	1.0 mg/kg	Placebo
Lean body mass	+3.6%	+4.1%	+2.6%
Spine bone density	+1.6%	+4.4%	+0.3%

The paper also reports a trend toward lower fat mass, without a registry figure.

Functional Outcomes

Measure	Result	Notes
6-minute walk, age 10+	+4.5 m and -3.2 m vs -47.6 m on placebo	Not significant
Strength	No consistent change	Similar to placebo

With nine or fewer boys per arm, the walking result is a signal, not proof.

Safety Concerns

Issues Leading to Halt

Issue	Nature
Telangiectasias	Dilated skin blood vessels
Epistaxis	Nosebleeds
Gingival bleeding	Gum bleeding

Mechanism of Concern

Factor	Explanation
ActRIIB targets	Binds ligands beyond myostatin
Vascular effects	Thought to follow from that broader binding

Lessons Learned

For Drug Development

Lesson	Implication
Selectivity matters	Broad blocking reached tissues outside muscle
Risk-benefit	Minor bleeding was enough to stop a pediatric program

For Bodybuilding Context

There are no human data for "ACE-031" sold as a research chemical. The trial drug's development ended in 2013, so nobody can confirm what those vials contain. WADA's 2026 Prohibited List names ACE-031 under S4.3, which is banned at all times.

As of October 2026, the field has moved to more targeted antibodies. The FDA approved apitegromab (Isembyld) for spinal muscular atrophy on September 11, 2026, the first approved myostatin-targeted drug. Its label warns of fracture risk, and WADA also lists it under S4.3.

Comparison to Other Approaches

For how this class compares with steroids, see our myostatin inhibitors vs anabolics comparison.

Current Status

Aspect	Status
Development	On hold from February 2011; ended May 2, 2013
Availability	None
Future	Acceleron and Shire said they would not restart it