PeptideInjectableMyostatin inhibitorActRIIB ligand trapFc-fusion protein

Ramatercept (ACE-031)

Also known as ACE-031 · ActRIIB-IgG1 · Ramatercept

Written by enwyReviewed 15 Jul 20261 sources0 comments

Ramatercept is a soluble activin receptor type IIB (ActRIIB) fusion protein — the ActRIIB extracellular domain linked to a human IgG1 Fc — engineered to act as a ligand trap for myostatin, activin and related GDFs. It reached Phase 2 in Duchenne muscular dystrophy, where it increased lean mass but was halted over vascular safety signals (nosebleeds and telangiectasias).

01 Overview

Ramatercept (developmental code ACE-031) works upstream of the muscle by mopping up the ligands that would otherwise activate ActRIIB. Because it traps not only myostatin but also activin A/B and several bone morphogenetic proteins, it produces robust increases in muscle mass but also engages pathways beyond muscle.

A Phase 2 trial in boys with Duchenne muscular dystrophy was stopped early after nonclinical and clinical vascular events — epistaxis, dilated skin vessels and gum bleeding — raised safety concerns, despite measurable gains in lean tissue. The programme was discontinued, and the ligand-trap approach was later refined into more selective molecules.

02 Mechanism

A dimeric ActRIIB-Fc decoy receptor that binds circulating myostatin, activin A/B and GDF-11 before they can activate cell-surface ActRIIB, de-repressing SMAD2/3-mediated suppression of muscle growth.

03 Dosing

Tier	Dose	Route	Notes
Trial dosing (DMD)	1–3 mg/kg/wk	SubQ	Phase 2 dosing given roughly every 2-4 weeks; programme discontinued.

04 Effects

Effect	Magnitude	Evidence
Increased lean massTrial participants showed increases in lean tissue and thigh muscle volume on imaging.	Measurable via DXA	Clinical
Increased bone density markersActRIIB trapping raised markers of bone formation.	Modest	Clinical

05 Side effects

Effect	Severity	Frequency	Evidence	Countermeasures
Injection-site reactionsLocal redness and irritation at subcutaneous injection sites.	Mild	Common	Clinical
Vascular events (epistaxis, telangiectasia)Nosebleeds, dilated skin capillaries and gum bleeding led to early trial termination.	Severe	Common in trial	Clinical

06 Legal status

United States

Investigational biologic (discontinued)

Never approved; development halted. WADA-prohibited (S4.5 myostatin-affecting agents). · as of Jan 2026

07 References

A soluble activin type IIB receptor (ACE-031) in Duchenne muscular dystrophy: a randomised, double-blind trialMuscle & Nerve, 2015

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.