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ACE-031

weak data

Also seen as: ramatercept, ACE031, ace

The Dose Guy’s verdict
Aug 28, 2026
3 sources

Skip it. ACE-031 reached human trials, showed real lean-mass gains from a single injection, and then the program was stopped because it caused nosebleeds, gum bleeding, and small dilated blood vessels that pointed to off-target vascular effects. Vendors still sell something labeled ACE-031, but testing shows most of those vials do not contain the actual compound. A drug shelved on safety, sold by vendors who mostly are not even selling it.

Would I take it?No, the trial was killed for a reason.

What it is

ACE-031 is a soluble decoy receptor, a fusion of activin receptor type IIB and an antibody fragment. It floats in the bloodstream and soaks up myostatin and other TGF-beta ligands that normally put the brakes on muscle growth, trapping them before they can reach muscle tissue and signal it to stop growing. Instead of adding a growth signal, you remove the stop signal.

This is not a secretagogue and has nothing to do with the GH axis. It sits on this shelf because the goal is the same, more muscle, but the mechanism is entirely separate. Acceleron Pharma developed it, tested it in humans, and pulled it when the off-target vascular effects showed up. The concept of myostatin inhibition lives on in other drugs, but ACE-031 specifically is done.

What the research shows

Actual human data exists, which makes the story sharper: it worked, and then it was stopped.

A single subcutaneous dose at 3 mg/kg increased total lean mass by 3.3% (P=0.03) and thigh muscle volume by 5.1% (P=0.03) at day 29 in healthy postmenopausal women. One shot, measurable muscle, less than a month.Muscle Nerve 2013 · phase 1 · n=48
No serious or severe adverse events, and they stopped the trial anyway: the Duchenne muscular dystrophy study halted after its second dosing regimen because of epistaxis and telangiectasias, small dilated blood vessels signaling off-target vascular effects.Muscle Nerve 2017 · DMD RCT
Of 14 black-market products sold as ACE-031, 12 contained an ACVR2B-immunoreactive protein, but analysis identified full-length human activin receptor IIB rather than the actual ACE-031 construct. What vendors sell and what the trials tested are not the same molecule.Drug Test Anal 2025 · market survey

Realistic protocols

I am not writing a protocol for a compound whose clinical program was killed on vascular safety signals. The phase 1 used single subcutaneous injections at doses up to 3 mg/kg, and even the DMD trial ran only two dosing cycles before the stop. If you run it anyway, know that most products on the market are not real ACE-031, that the vascular effects were the reason development ended, and that you are past the frontier of what anyone has tested. Go low, go short, and do not confuse the concept of myostatin inhibition with this specific shelved drug. If you want muscle gain with actual data and a protocol behind it, the secretagogue side of this shelf, ipamorelin and CJC-1295, is where people start.

Side effects

The trial data is the side-effect data. The vascular signal ended the program:

monitorEpistaxis and telangiectasias. Nosebleeds and small dilated blood vessels, seen in the DMD trial and attributed to off-target effects on vascular ligands in the ACVR2B family. This is what stopped development.
commonInjection-site erythema, reported in the phase 1 study.
unknownThe program never ran long enough to map what chronic exposure does. The vascular signal appeared early, in a short trial, at a low cumulative dose. Longer runs are uncharted.

Where to buy

RUO.bio–
$88 / 1mg vial$88.00/mg
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