Origin

Acceleron Pharma fused the ACVR2B ectodomain to IgG1 to build a high-affinity decoy receptor for myostatin and activins, aimed at muscle-wasting diseases like Duchenne muscular dystrophy.

Mechanism

Binds myostatin and activins as a soluble decoy receptor, removing their brake on myogenesis and letting muscle protein synthesis run unopposed.

Research summary

Evidence

A randomized placebo-controlled DMD trial was stopped early after vascular safety signals, epistaxis and telangiectasias, appeared. Before that, it showed non-significant trends toward maintained 6-minute walk distance and increased lean mass.

Evidence tier: Investigational (halted clinical trials) — see the methodology note for how this is assessed.

Citations

Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial — Campbell et al. 2016

Reported benefits

increased lean muscle mass (preclinical/animal)
muscle strength preservation (animal models)

Dosing protocols reported in the literature & community

These are protocols reported by compounding pharmacies, published trials, or self-experimentation communities — not a prescription. Start low, especially for anything new.

Reported dosing protocols
Route	Reported protocol
Subcutaneous injection	Clinical trial dosing every 2-4 weeks, ascending; no community-standard dosing due to trial discontinuation.

Side effects

epistaxis (nosebleeds)
telangiectasias (abnormal blood vessel proliferation)
potential vascular complications

Safety notes

Community & reddit notes (anecdotal — not clinical evidence)

Some still chase it for myostatin inhibition, but manufacturing cost limits underground supply, and most informed users skip it given the safety signal.