Follistatin

The only real human trial data for follistatin-based therapy comes from a tiny, open-label gene-therapy study — not from anything resembling the injectable peptide vials sold as "follistatin" today, which have no dedicated human trial behind them that we could find.

What it is — and the naming gap here too

Follistatin is an endogenous glycoprotein that neutralizes myostatin and activin, promoting muscle growth by blocking the signals that normally limit it. The only real human clinical program is AAV1-FS344, a gene therapy developed by Nationwide Children's Hospital researchers that delivers the gene for a specific follistatin isoform via a viral vector — a fundamentally different product, route and risk profile from the injectable "follistatin peptide" sold as a research chemical online, which is not what was tested in the trial below.

The trial evidence

A Phase 1/2a, open-label gene-therapy trial in Becker muscular dystrophy patients — direct intramuscular AAV1-FS344 injection into the quadriceps — reported improved six-minute-walk-distance in most treated patients, with accompanying muscle-pathology improvements (Mendell, Sahenk, Malik, Gomez, Flanigan, Lowes, et al., "A Phase 1/2a Follistatin Gene Therapy Trial for Becker Muscular Dystrophy," Mol Ther 2015;23(1):192-201, DOI 10.1038/mt.2014.200, PMID 25322757). This is a real, small, uncontrolled, early-phase signal — not a placebo-controlled confirmatory result.

What this doesn't tell you about the injectable peptide

Because the trial tested a gene therapy, not a synthetic follistatin peptide, none of its findings — encouraging or otherwise — transfer to the injectable products marketed for muscle growth or fat loss. We did not find any human trial of the injectable peptide form itself.

Regulatory status

Neither product is FDA-approved. The gene therapy remains investigational; the injectable peptide is not a studied or lawful ingredient for human use.