ARIA
Library/muscular/Follistatin-344

Follistatin-344

Not FDA Approved⛔ WADA Banned

FS-344 / Follistatin-like peptide

muscular◆EmergingMyostatin inhibitor / TGF-beta superfamily binding protein

Follistatin is a potent myostatin (GDF-8) and activin inhibitor. Animal knockout models show dramatic muscle hypertrophy. Clinically used in muscular dystrophy trials. Binds and neutralizes myostatin → removes the 'brake' on muscle growth. Also inhibits activin → may affect reproductive hormones.

Confidence
35%
Half-Life ~hours (recombinant); fragments shorter
Cost ~$800/mo
Quick Reference
Routesubcutaneous / intramuscular
MechanismBinds and neutralizes myostatin (GDF-8) → blocks ActRIIB signaling → removes inh...
SequenceFull-length follistatin (344 AA isoform) — fragments used therapeutically
Mol. Weight38000 Da
Reviewed2026-08-08

Mechanism of Action

Binds and neutralizes myostatin (GDF-8) → blocks ActRIIB signaling → removes inhibition of myoblast proliferation/differentiation. Also inhibits activin A → reduces FSH. Activates follistatin-activated satellite cells. Promotes muscle hypertrophy. Reduces TGF-beta-mediated fibrosis.

Dosing Protocol

100-200μg recombinant follistatin SC daily or every other day. Gene therapy approach (rAAV1-FS344) used in Duchenne trials. Cycle 4-8 weeks.

Key Studies

2009

Follistatin: key to muscle growth regulation

PMID 19741699review
2015

Follistatin gene therapy in Duchenne muscular dystrophy

PMID 25684206clinical_trial
2012

Myostatin inhibition enhances muscle mass in primates

PMID 22837538preclinical
2016

ACE-031 and myostatin pathway therapeutics

PMID 27589243review

Adverse Effects

Theoretical: muscle overgrowthPotential cardiac effects (myostatin in heart)Inhibin/activin disruption → reproductive hormone imbalanceLimited human safety data for peptide formPotential liver effects

Contraindications

  • Active malignancy
  • Pregnancy
  • Competitive athletes (WADA banned)
  • Cardiac conditions
  • Hormone-sensitive conditions

Storage

Recombinant protein: 2-8°C, do not freeze. Protect from light. Stable for 12 months refrigerated.

Clinical Applications

  • ["muscle_growth"
  • "muscular_dystrophy"
  • "cachexia"
  • "sarcopenia"]