ACE-031 vs Follistatin 344
A neutral, side-by-side comparison of two performance & growth hormone peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
ACE-031
Soluble form of activin type IIB receptor (ActRIIB-Fc fusion protein) that acts as a myostatin and activin trap. Blocks the primary signals that limit muscle growth by sequestering myostatin, activin, and related ligands before they reach cell surface receptors. Phase 2 trials in Duchenne muscular dystrophy demonstrated significant lean mass increases.
Full profileFollistatin 344
Follistatin 344 is a 344-amino acid isoform of follistatin — an endogenous glycoprotein that functions primarily as a myostatin and activin inhibitor. Myostatin (GDF-8) is the body's primary muscle growth suppressor; follistatin binds and neutralizes it with high affinity, removing this brake on muscle protein synthesis. Research and animal data show dramatic increases in muscle fiber size and strength when follistatin is elevated or myostatin is inhibited.
Full profile| ACE-031 | Follistatin 344 | |
|---|---|---|
| Category | Performance & Growth Hormone | Performance & Growth Hormone |
| Also known as | ACVR2B-Fc, ActRIIB-Fc fusion protein | FST-344, Follistatin isoform 344, FST |
| Evidence | Investigational (in trials) | Research-stage |
| Dosing range | 0.3mg/kg–3mg/kg mg/kg, every 2–4 weeks (subcutaneous injection) | 50mcg–200mcg mcg, Once daily or every other day for 10–30 day cycles |
| Administration | Subcutaneous injection | Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis) |
| Key side effects | Nosebleeds (epistaxis — most common reported AE), Telangiectasia (visible small blood vessel dilation), Gum bleeding, Elevated hemoglobin | Potential FSH suppression (reproductive effects in females — may affect menstrual cycle), Accelerated hair follicle cycling (Wnt pathway involvement — theoretical hair loss concern at high doses), Joint discomfort with rapid muscle tissue growth, Limited long-term human safety data |
| Cited sources | 2 references | 3 references |
Key differences
- Evidence level differs: ACE-031 is investigational (in trials), while Follistatin 344 is research-stage.
- Administration: ACE-031 — Subcutaneous injection; Follistatin 344 — Subcutaneous injection, Intramuscular injection (into target muscle — local effect hypothesis).
- Dosing units differ: ACE-031 is dosed in mg/kg, Follistatin 344 in mcg — they operate at different scales.
- Frequency: ACE-031 is typically every 2–4 weeks (subcutaneous injection); Follistatin 344 is Once daily or every other day for 10–30 day cycles.
- Research depth: this profile cites 2 sources for ACE-031 vs 3 for Follistatin 344.
How each works
ACE-031
ACE-031 functions as a decoy receptor, binding myostatin, activin A/B, GDF-11, and BMP-9 in circulation before they can activate cellular ActRIIB receptors. In the Duchenne muscular dystrophy Phase 2 trial, ACE-031 produced meaningful lean body mass increases but was halted due to vascular side effects (epistaxis, telangiectasia) requiring dose and safety optimization.
Follistatin 344
Follistatin's muscle effects were dramatically illustrated when mice and cattle with follistatin overexpression or myostatin knockouts developed 2–3x normal muscle mass. Human follistatin gene therapy trials (AAV-mediated) are ongoing for Becker Muscular Dystrophy, showing sustained myostatin inhibition and improved muscle function over years from a single injection. Follistatin also inhibits activin A and B (involved in muscle wasting during illness), FSH secretion (reproductive effects), and inflammatory cytokines. The 344 isoform has an extended heparin-binding domain that increases tissue retention compared to the shorter FST-288 isoform.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.