Peptides Muscle BuildingMetabolic Human clinical data

ACE-031

ActRIIb-Fc

3 days

Half-life

0.5–3 mg

Typical dose

4–8 weeks

Cycle length

Investigational decoy receptor that sequesters myostatin/GDF-11 to drive muscle growth.

Key takeaways

Decoy receptor (ActRIIB-Fc) that traps myostatin and blocks its brake on muscle growth.
Half-life ~3 days; trials dosed subcutaneously every 2–4 weeks.
Human trials showed lean-mass gains, then the DMD trial was halted over safety signals.
Discontinued and never approved; anything sold now is unregulated grey-market material.

Overview

What it is

ACE-031 is a recombinant fusion protein joining the activin receptor type IIB extracellular domain to an antibody Fc backbone. It circulates as a decoy receptor, binding myostatin and related ligands before they can reach muscle and suppress growth. Animal models showed large increases in muscle mass, which drove development for muscle-wasting disease.

Pharmacokinetics

As a large Fc-fusion protein it clears slowly, with a half-life of roughly 3 days and high bioavailability near 80%. Trials dosed every 2 to 4 weeks.

What the evidence says

Human data exists, which is rare here: a healthy-volunteer study showed lean-mass gains, then a randomized trial in Duchenne muscular dystrophy was stopped early over safety signals, including telangiectasia and minor bleeding events. Development was discontinued, and ACE-031 is not an approved medication.

Reported dosing protocols

Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.

Use case	Dose	Route	Frequency	Duration
Muscle growth (trial context)	1–3 mg/kg	SubQ	Every 2–4 weeks	Up to 12 weeks in trials
Muscle growth (community)	0.5–1 mg	SubQ	Once weekly	4–8 weeks

Pharmacokinetic summary

Model tier: Simple (t½ + F, Tmax estimated)
Half-life: 3 days
Bioavailability: 80%
Typical dose: 0.5–3 mg

Frequently asked questions

Why was ACE-031 discontinued?

The pivotal Duchenne muscular dystrophy trial was stopped early after safety signals, mainly telangiectasia (small dilated blood vessels) and minor nose and gum bleeding. The developer shelved the program rather than resolve the mechanism.

Does ACE-031 actually build muscle?

Yes, measurably. The healthy-volunteer ascending-dose study found increased lean mass and thigh muscle volume after a single dose. That biological activity is exactly why grey-market versions circulate, despite the unresolved safety questions.

How does ACE-031 differ from myostatin antibodies?

Both target the myostatin pathway. ACE-031 is a soluble decoy receptor that binds myostatin plus several related ligands (GDF-11, activins); newer antibodies like apitegromab target myostatin precursors more selectively, which may mean a cleaner safety profile.

References

Estimated (preclinical/protein) — Decoy receptor for myostatin; extended protein half-life (~days).
Muscle Nerve 2013 — ACE-031 single ascending-dose study — Healthy-volunteer trial showing lean-mass and thigh-volume gains after one dose.
Muscle Nerve 2017 — ACE-031 Duchenne RCT — Randomized placebo-controlled trial in DMD boys, terminated early over safety signals.

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