Follistatin-344

Research-Grade

Follistatin-344 (FS344) is the full-length isoform of human follistatin, a single-chain glycoprotein expressed in nearly all tissues. Its primary biological role is to bind and neutralize members of the TGF-β superfamily, most notably myostatin (GDF-8) and activin A — both of which act as powerful negative regulators of skeletal muscle mass. In animal models, overexpression of follistatin produces dramatic muscle hypertrophy even in myostatin-knockout backgrounds, indicating it inhibits additional anti-growth signals beyond myostatin alone. This has made it a major focus of gene therapy research: Nationwide Children's Hospital has conducted phase I/II AAV-follistatin gene therapy trials in Becker muscular dystrophy and inclusion body myositis with encouraging safety and preliminary efficacy data. As an injectable peptide, FS344 is available only as a research compound. Its large molecular size and glycosylation make bioavailability and stability more challenging than typical small peptides. Most practical use is via gene therapy vectors rather than direct peptide injection.