ACE-031 (ActRIIB Decoy)

Also known as: ramatercept, ACVR2B-Fc, activin receptor type IIB decoy

Wellness

In plain English

ACE-031 is an engineered protein that acts as a "decoy" to soak up myostatin and related signals that normally limit muscle growth, so muscles can get bigger and stronger. It was developed as a drug for muscular dystrophy and reached human trials, but the company halted development after volunteers and patients developed side effects such as nosebleeds, gum bleeding, and small skin blood-vessel changes. It is not FDA-approved.

The science

ACE-031 is a soluble fusion protein combining the extracellular domain of activin receptor type IIB (ActRIIB) with an IgG1-Fc region; it binds myostatin, activin, and related TGF-β superfamily ligands, blocking their negative regulation of muscle mass. A single-ascending-dose study in healthy postmenopausal women showed increases in lean/muscle mass and markers of muscle growth (Attie et al., 2013), and a trial in ambulatory boys with Duchenne muscular dystrophy was conducted (Campbell et al., 2017) but the program was discontinued after off-target vascular adverse effects (epistaxis, gingival bleeding, dilated blood vessels/telangiectasia) reflecting the ligands' roles beyond muscle. Human evidence exists but development was halted for safety; it is not FDA-approved.

References

• Attie KM et al., Muscle Nerve 2013 (single-ascending-dose ACE-031 in healthy volunteers)
• Campbell C et al., Muscle Nerve 2017 (ACE-031 in Duchenne muscular dystrophy)