Follistatin
The body's natural myostatin trap. Gene-therapy trials have been conducted in muscular dystrophy; injectable follistatin as sold has no human evidence at all.
Bone & Muscle
ACE-031
A myostatin-blocking decoy receptor that increased muscle mass in trials, then had its development halted over vascular bleeding events.
Overview
Myostatin is the brake on muscle growth — animals that lack it are famously overmuscled. ACE-031 is the outer part of the receptor myostatin binds to, fused to an antibody fragment and injected into the bloodstream, where it acts as a sponge. Myostatin binds it instead of the real receptor on muscle, and the brake comes off. It worked: muscle mass increased in healthy volunteers and in boys with Duchenne muscular dystrophy. The trial was stopped anyway, because of nosebleeds and dilated blood vessels in the gums.
A recombinant fusion of the extracellular domain of activin receptor type IIB to a human IgG1 Fc. Acts as a ligand trap for myostatin (GDF-8) and, critically, for other ActRIIB ligands including activin A, GDF-11 and BMPs. Blockade removes SMAD2/3-mediated inhibition of muscle protein synthesis, increasing lean mass and bone mineral density. The phase 2 programme in Duchenne muscular dystrophy was terminated after epistaxis and telangiectasia were observed, attributed to the trap's non-selective binding of BMP9/10 and consequent effects on vascular endothelium — a mechanistic consequence of the decoy's breadth rather than an idiosyncratic reaction.
Research areas
Muscle wastingDuchenne muscular dystrophyMyostatin signalling
Dosing reported in the literature
Every protocol below is reproduced from a published study or approved labelling, with its source named. These are records of what was studied — not recommendations, and not a suggestion that any of them is appropriate for any person.
| Protocol as reported | Source |
|---|---|
| Single subcutaneous doses of 0.02–3 mg/kg in healthy postmenopausal womenDose-dependent increases in lean mass and bone formation markers were observed. | Attie et al., Muscle & Nerve 2013 |
| Repeat dosing in boys with Duchenne muscular dystrophy, stopped before completion | Campbell et al., Muscle & Nerve 2017 |
Trial status
Phase 1 completed in healthy postmenopausal women. Phase 2 in Duchenne muscular dystrophy terminated early for safety.
Reported safety signals
- Epistaxis and gum telangiectasia led to termination of the Duchenne programme. These were considered mechanism-related, not incidental.
- The decoy binds several TGF-beta superfamily ligands beyond myostatin, so effects are not confined to muscle.
- Any material sold under this name is not the clinical product and carries the same mechanistic bleeding concern without any monitoring.
Common questions
Why was ACE-031 stopped if it worked?
Because it worked by trapping a whole family of signalling molecules, not just myostatin. Some of those — BMP9 and BMP10 — maintain blood vessel integrity. Blocking them produced nosebleeds and visible dilated vessels, and there was no way to keep the muscle effect while avoiding it.
Primary sources
- 01
A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers
- 02
Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: results of a randomized, placebo-controlled clinical trial
- 03
Myostatin inhibition in muscle, but not adipose tissue, decreases fat mass and improves insulin sensitivity
Medical disclaimer
This page is for informational and research purposes only. Nothing here constitutes medical advice. The compounds discussed are research chemicals. Consult a qualified clinician before starting any protocol.
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