NO. 038 · STAGE 2 · Lv. 82 · HP 160
FOLLISTATIN-344
Myostatin Antagonist · 344-Residue Isoform
ALIASES
Follistatin-344, FS-344, follistatin 344-residue isoform
CLASS
Synthetic peptide · myostatin and activin antagonist (344-residue isoform)
FORMULA
Complex glycoprotein · 344 amino acids
SEQUENCE
344-residue isoform of the FST gene · contains FSD1-FSD3 follistatin domains (full sequence reproduces UniProt P19883 isoform 2)
HALF-LIFE
Several days (long-acting in animal models)
ROUTES
Subcutaneous (research) · Intramuscular (research)
MECHANISM OF ACTION
344-amino-acid isoform of follistatin, the endogenous antagonist of myostatin (GDF-8) and activin. Binds and neutralizes myostatin to release the brake on skeletal muscle growth. Animal models report substantial lean-mass gains. WADA-prohibited under Section S2.
EVIDENCE GRADES
Well-characterized binding to myostatin and activin. Lee et al. multi-paper evidence base for follistatin antagonism of TGF-beta family ligands.
Kota 2009 (PMID 20371475) follistatin gene therapy in primate model produced substantial muscle pathology improvement in Duchenne muscular dystrophy.
No completed long-term human Phase 3 trials for body-composition endpoints.
MECHANISM CATEGORIES
RESEARCH CONDITIONS
SAFETY
Side effects
- Injection-site reactions
- Theoretical risk of off-target activin pathway inhibition (HPG-axis effects)
- Limited published Western safety data
Known interactions
- Concurrent activin-blocking therapy (theoretical additive effects)
Contraindications
- Active malignancy
- Pregnancy/lactation
- Off-label muscle-wasting indications without clinical supervision
REGULATORY STATUS
FDA · Not FDA-approved. Investigational compound. Research-use only.
WADA · Prohibited at all times under WADA Section S2 (Growth Factors and Myostatin Antagonists sub-category).
STORAGE
Lyophilized · -20 °C 24 months
Reconstituted · 2-8 °C, 14-28 days
PEER-REVIEWED EVIDENCE
- Lee SJ, Lee YS, Zimmers TA, et al.. Regulation of muscle mass by follistatin and activins. Mol Endocrinol 2010. PMID 20801891. link →
- Kota J, Handy CR, Haidet AM, et al.. Follistatin gene delivery enhances muscle growth and strength in nonhuman primates. Sci Transl Med 2009. PMID 20371475. link →
FAQ · 8 QUESTIONS
▶ What is follistatin-344?
Follistatin-344 is the 344-amino-acid isoform of the endogenous protein follistatin, which binds and neutralizes myostatin (GDF-8) and activin. Antagonism of these TGF-beta family ligands releases the brake on skeletal muscle growth in animal models.
▶ Follistatin-344 vs Follistatin-315 · what's the difference?
FST-344 and FST-315 are two isoforms of the FST gene. FST-344 contains an additional N-terminal extension and binds heparan-sulfate proteoglycans on the cell surface, producing extended local tissue retention. FST-315 lacks this extension and circulates more freely. Research selects between them based on local-vs-systemic design.
▶ Is follistatin-344 FDA-approved?
No. Investigational compound. Research-use only.
▶ Is follistatin-344 WADA-prohibited?
Yes. Follistatin-344 is prohibited at all times under WADA Section S2 in the Growth Factors and Myostatin Antagonists sub-category.
▶ How does follistatin work?
Follistatin binds myostatin (GDF-8) and activin in a 2:1 ratio, sequestering them away from their cognate ActRIIB receptor on skeletal muscle. The receptor blockade releases the negative regulation that myostatin normally imposes on muscle hypertrophy, increasing lean mass in animal models.
▶ What were the primate gene-therapy results?
Kota et al. 2009 (PMID 20371475) reported substantial muscle pathology improvement in a primate model of Duchenne muscular dystrophy after AAV-FST344 gene therapy. The work supports follistatin as a candidate for muscle-wasting therapy and is the basis for ongoing investigational gene-therapy programs.
▶ What are the side effects?
Limited published human safety data. Theoretical risks include off-target activin pathway inhibition (HPG-axis disruption from activin antagonism), and injection-site reactions. Animal-model evidence indicates greater safety than direct anti-myostatin antibodies, which have produced cardiac and HPG side effects in clinical trials.
▶ How is follistatin-344 dosed in research?
Animal-model research uses variable subcutaneous and intramuscular dosing. Human-equivalent dosing is not established. This wiki does not recommend any human dose.
SIGNATURE MOVES
Binds and neutralizes circulating myostatin.
Animal-model lean-mass gains. WADA S2 prohibited.
SOURCED FROM PEPPU LABS
Reference compounds documented on this page are available as research-grade material at Peppu Studio · ≥99% purity · per-batch Certificate of Analysis. For laboratory research use only. No human dose is recommended by this wiki.
▶ LAST UPDATED · 2026-05-25