PeptidePeptideFc-fusion biologicMyostatin/activin trap

ACE-031

Also known as Ramatercept · ActRIIB-Fc · ACE031

Written by enwyReviewed 15 Jul 20261 sources0 comments

ACE-031 (ramatercept) is a soluble activin receptor type IIB fused to an antibody Fc fragment, designed to act as a decoy trap for myostatin and related ligands. It was tested clinically for Duchenne muscular dystrophy, where it increased muscle volume but trials were halted over safety signals including nosebleeds and gum bleeding (telangiectasias). It is a large biologic, not a peptide suited to casual subcutaneous dosing.

01 Overview

ACE-031 works by mopping up myostatin and other activin-receptor ligands before they can signal, releasing the brake on muscle growth without directly targeting the receptor on muscle. Acceleron and partners advanced it into human trials for Duchenne muscular dystrophy in boys.

Early-phase results showed increases in lean and muscle mass, but the program was stopped because of vascular safety signals — notably epistaxis (nosebleeds), gum bleeding, and dilated blood vessels (telangiectasias) — consistent with off-target effects on the ActRIIB/BMP pathway in vasculature. Its bodybuilding use is entirely off-label and based on the muscle-mass signal while ignoring the reason its trials ended.

02 Mechanism

A soluble ActRIIB-Fc fusion protein that binds and sequesters myostatin, activins and related TGF-beta ligands, blocking their inhibitory signalling and permitting muscle growth.

03 Dosing

Tier	Dose	Route	Notes
Trial-derived	1–3 mg/wk	SubQ	Trials dosed roughly 1-3 mg/kg every 2-4 weeks; per-kg dosing means figures here are indicative only.

04 Effects

Effect	Magnitude	Evidence
Increased muscle volume / lean massIncreased thigh muscle volume and lean mass observed in DMD trial subjects.	Measurable increases in early trials	Clinical
Raised bone/muscle biomarkersChanges consistent with anabolic and bone effects were seen.	Biomarker-level	Clinical

05 Side effects

Effect	Severity	Frequency	Evidence	Countermeasures
Dilated blood vessels / skin changesTelangiectasias (visible dilated vessels) observed.	Moderate	Reported in trials	Clinical
Vascular bleeding (epistaxis, gum bleeding, telangiectasia)Nosebleeds, gum bleeding and dilated small vessels led to trial suspension.	Severe	Trial-limiting	Clinical

06 Legal status

United States

Investigational; development halted

Never approved; clinical program discontinued over safety. WADA-prohibited. · as of Jan 2026

07 References

A soluble activin type IIB receptor (ACE-031) in Duchenne muscular dystrophyMuscle & Nerve / Neurology (Phase I/II)

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.