# ACE-031

> ACE-031 is an engineered fusion protein combining the extracellular domain of the activin receptor type IIB with an antibody Fc fragment, designed to act as a soluble decoy, or trap, that sequesters myostatin and related ligands before they can bind their natural receptor. It was originally developed by Acceleron Pharma and studied in clinical trials for Duchenne muscular dystrophy and other muscle-wasting conditions. Trial results showed measurable increases in lean muscle mass, but the program was discontinued after unwanted vascular side effects emerged. It remains referenced in muscle-research contexts largely because of this human trial history, unlike many peptides in this category.

- URL: https://www.lifeconverted.com/peptides/ace-031
- Also known as: ACVR2B-Fc, RAP-031
- Primary category: Muscle & Performance
- Effectiveness rank: #7 in Healing & Recovery; #11 in Muscle & Performance
- Evidence level: Moderate evidence
- Route: Subcutaneous
- Dose range: 0.5-3 mg
- Dose tiers: low 0.5 mg; moderate 1 mg; high 3 mg
- Half-life: Approximately 20-30 days, reflecting its Fc-fusion structure
- Timing: Morning
- Cycle: 4-6 weeks on, 12+ weeks off (Original trials used single or infrequent dosing given the long half-life; given documented vascular side effects, cautious and infrequent use is emphasized in discussion of this compound.)
- Storage: Store lyophilized protein frozen; reconstitute per supplier instructions and keep refrigerated, using promptly given limited stability data outside trial conditions.

## Mechanism of action

By presenting a soluble, high-affinity version of the activin type IIB receptor, ACE-031 intercepts myostatin, GDF-11, and certain activins in circulation before they can bind their membrane-bound receptors on muscle cells. This prevents activation of the Smad2/3 pathway that normally restrains muscle fiber growth, shifting the balance toward hypertrophy. The Fc fusion also extends the molecule's circulating half-life relative to a bare receptor fragment.

## Reported benefits

- Documented increases in lean muscle mass in early-phase human trials
- Broad-spectrum trapping of multiple myostatin-family ligands
- Extended circulating half-life due to Fc fusion
- Historical clinical data provide more concrete human evidence than most peptides in this category

## Reported side effects

- Nosebleeds (epistaxis) reported in trial participants
- Gum bleeding and skin telangiectasias (dilated blood vessels) observed in trials
- Discontinued from clinical development due to these vascular safety findings
- Long-term safety beyond the trial period is not established

## Common protocols

- Infrequent (weekly to monthly) subcutaneous dosing based loosely on published trial regimens

## Stacking notes

Its long half-life and broad ligand-trapping action make combination with other myostatin-pathway agents (e.g., follistatin) largely redundant and potentially additive in risk rather than benefit; not established in any published protocol.

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