FS-344, Follistatin Preprotein
Evidence Grade E — Very limited evidence. 4 published studies. 0 registered clinical trials.
Follistatin 344 is a natural protein that neutralises the signals limiting muscle growth, including myostatin. Clinical investigation has used gene therapy (viral delivery of the follistatin gene into muscle cells) rather than direct protein injection, because injected follistatin protein is cleared from the body within hours. Small gene therapy trials in muscular dystrophy have shown encouraging results.
4 published studies: 3 human, 0 animal, 0 in-vitro, 0 reviews
Follistatin 344 has no marketing authorisation as a direct pharmaceutical product. Phase I/II gene therapy trials (AAV1-FS344) in Becker muscular dystrophy (6 patients) and sporadic inclusion body myositis (6 patients) have been conducted, delivering the gene for follistatin via intramuscular viral vector injection. Results showed improvements in walking distance and muscle fibre size.
Direct injection of follistatin protein is pharmacologically challenging due to rapid clearance. The gene therapy approach circumvents this by having muscle cells produce follistatin continuously. Products sold as injectable follistatin through unregulated channels face fundamental pharmacokinetic problems that gene therapy is designed to solve. Products from unregulated sources lack pharmaceutical quality assurance.
Research has established that follistatin works by physically wrapping around and neutralising myostatin (the primary brake on muscle growth) and activin (involved in muscle wasting and inflammation). Two follistatin molecules encircle one myostatin or activin dimer, preventing it from activating its receptors. This ligand-trapping mechanism is well characterised structurally.
Research suggests Phase I/II gene therapy trials (6 patients each in Becker muscular dystrophy and inclusion body myositis) showed improvements in walking distance and muscle fibre size. These are small, open-label studies without randomised controls, and a detailed methodological critique has been published. Direct protein injection faces a fundamental pharmacokinetic problem — approximately 2-hour half-life — that gene therapy is designed to solve. Products sold as injectable follistatin through unregulated channels face this same problem. Research suggests chronic follistatin overexpression may weaken bone. Products from unregulated sources lack pharmaceutical quality assurance.
No trials registered on ClinicalTrials.gov for this compound.
The information on this page is provided for educational and research reference purposes only. This is not medical advice. Always consult a qualified healthcare professional before making any health-related decisions.
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