ACE-031

Overview

ACE-031 (ramatercept) is a soluble fusion protein of the activin receptor IIB (ActRIIB) extracellular domain and human IgG1 Fc, developed by Acceleron Pharma as a myostatin/activin ligand trap for muscle-wasting disorders. Clinical development was HALTED in 2011 after unexpected vascular adverse events (epistaxis, telangiectasia) attributed to off-target BMP-9/10 inhibition. NOT FDA-approved; all further development was terminated. Now sold only as a grey-market research chemical. WADA-prohibited (myostatin inhibitor).

Mechanism of Action

ACE-031 traps myostatin, activin A/B, GDF-11, and BMP-9/10 before they can engage membrane-bound ActRIIB, blocking Smad2/3 signaling and muscle atrophy gene expression (MuRF1, MAFbx). The IgG1-Fc extends half-life to ~10-15 days. The broad binding profile produces potent anabolic effects but also BMP-9/10-related vascular considerations.

Research Summary

Phase 2 in ambulatory boys with Duchenne muscular dystrophy was terminated early in 2011 after unexpected nose-bleeds and telangiectasia were observed (attributed to off-target BMP-9/10 neutralization); published results later showed no significant 6MWT benefit vs. placebo in the truncated trial (Campbell et al., Muscle & Nerve, 2017; PMID 27462804). A single-ascending-dose Phase 1 study in healthy postmenopausal women (Attie et al., Muscle & Nerve, 2013; PMID 23169607) showed dose-dependent modest lean-mass increase but also the same vascular signal. Acceleron formally discontinued ACE-031 in 2013 and pivoted to other ActRII programs. No FDA approval; development TERMINATED for vascular safety. WADA-prohibited.

Dosing Information

Reported Side Effects

• Epistaxis (nosebleeds) — caused trial halt
• Telangiectasias (small dilated blood vessels near skin surface) — caused trial halt
• Gingival bleeding
• Vascular fragility from off-target BMP-9/10 inhibition
• Injection site erythema
• Transient changes in FSH / reproductive hormones
• Theoretical cardiac hypertrophy risk from myostatin inhibition

Research References

• Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial (2017)
• A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers (2013)