Compare prices and buy Follistatin 344 from 4 research peptide vendors - also called suppliers or sources. Updated daily.
The 344-residue precursor of follistatin, which is processed to the mature 315-residue protein, FS315. Follistatin binds activin, myostatin and related TGF-beta superfamily ligands outside the cell and blocks their receptor binding, and it is thought to promote muscle growth both by restraining myostatin and through pathways independent of it. It has been tested in people only as a gene therapy, not as the protein, and is not FDA-approved.
For research purposes only. Not medical advice.
Follistatin 344 is the full-length precursor of follistatin, a secreted glycoprotein far larger than the short synthetic peptides PeptideScouter mostly indexes. UniProt's reference entry for human follistatin (P19883) counts 344 residues. The first 29 form a signal peptide that is cleaved off during secretion, leaving a 315-residue mature chain with two N-linked glycosylation sites. PeptideScouter catalogues it with the growth hormone and muscle compounds because research vendors sell it from the same catalogs, not because it shares their chemistry. That category page also explains why a follistatin listing without an isoform number is hard to interpret.
Alternative splicing of the follistatin gene produces two proteins. UniProt lists isoform 1, known as FS315, and isoform 2, known as FS288, which lacks the last 27 residues of the chain, and it reports FS315 as the predominant isoform in serum. The number in a vendor title counts residues before processing, so "Follistatin 344" names the precursor that becomes FS315. Vendors also abbreviate it FST-344.
Follistatin was first described as a specific inhibitor of follicle-stimulating hormone (FSH) release from the pituitary. In 1990 Nakamura and colleagues at RIKEN purified an activin-binding protein from rat ovary and found it was identical to follistatin (Science, 1990). Activin is a TGF-beta family protein that stimulates FSH release, so the finding linked follistatin's best-known effect to a binding partner.
Lee and McPherron at Johns Hopkins extended the picture to skeletal muscle (PNAS, 2001). They showed that follistatin blocks the binding of myostatin, a negative regulator of muscle mass, to the activin type IIB receptor. Independent lines of transgenic mice expressing high levels of follistatin in skeletal muscle showed increases in muscle mass comparable to those of myostatin knockout mice. UniProt summarizes the mechanism as binding activin, myostatin, GDF11 and bone morphogenetic proteins in the extracellular space and blocking their type II receptor-binding site, so myostatin is one of several ligands it neutralizes.
As of October 21, 2026, every ClinicalTrials.gov record that gives people follistatin delivers its gene, by an adeno-associated virus (AAV) vector or a plasmid, and none administers the protein. The peer-reviewed results come from Jerry Mendell's group at Nationwide Children's Hospital in Columbus, Ohio, which delivered an AAV1 vector carrying the human FS344 gene (rAAV1.CMV.huFollistatin344) to the quadriceps muscles. The investigators chose the FS344 isoform "to avoid potential binding to off target sites."
In each of these trials the material given was a gene vector that has muscle cells make follistatin themselves, a different product from follistatin protein.
No FDA-approved drug contains follistatin. As of October 21, 2026 it appears in no category of FDA's 503A bulk drug substance nominations (file updated May 14, 2026) or its 503B nominations (file updated March 21, 2025), which means it is also absent from Category 2, the substances FDA says raise significant safety risks.
Not in the usual sense. Follistatin 344 is the 344-residue precursor of follistatin, a secreted glycoprotein. UniProt's entry for human follistatin (P19883) shows a 29-residue signal peptide removed during secretion, leaving the 315-residue mature protein known as FS315. PeptideScouter lists it among growth hormone and muscle compounds because research vendors sell it alongside peptides.
Alternative splicing of the follistatin gene produces two proteins, FS315 and FS288, and UniProt reports FS315 as the predominant form in serum. Follistatin 344 is the precursor of FS315 before its 29-residue signal peptide is removed, so the 344 counts residues before processing. FS288 is the shorter splice variant, lacking the last 27 residues of the chain.
Only as gene therapy. Trials led by Jerry Mendell at Nationwide Children's Hospital delivered the human FS344 gene with an adeno-associated virus vector to patients with Becker muscular dystrophy, sporadic inclusion body myositis and Duchenne muscular dystrophy. As of October 21, 2026, no study registered on ClinicalTrials.gov administers follistatin protein.
Follistatin binds myostatin and blocks its binding to the activin type IIB receptor. In a 2001 PNAS study, Lee and McPherron found that transgenic mice expressing high levels of follistatin in skeletal muscle gained muscle mass comparable to myostatin knockout mice. Follistatin also binds activin and other TGF-beta family proteins, and it was first identified as an inhibitor of FSH release from the pituitary.
No. No FDA-approved drug contains follistatin, and as of October 21, 2026 it appears in no category of FDA's 503A or 503B bulk drug substance nominations, including Category 2.
Follistatin 344 is sold by 4 research peptide vendors indexed on PeptideScouter, with 5 tracked listings compared per vendor in the table above. Pricing is normalized and refreshed daily.
2 of the 4 indexed vendors currently have Follistatin 344 in stock. The comparison table marks out-of-stock listings, and stock state is refreshed daily.
Northline Labs currently lists Follistatin 344 at $118.14/mg, the lowest listed price across 4 tracked research peptide vendors. With current vendor discount codes applied, the lowest effective price is $75.79/mg.
Discount codes are issued per vendor rather than per peptide, so any code applies across that vendor's whole catalog. All 4 vendors listing Follistatin 344 publish a PeptideScouter code, worth 10% off. Applied, the lowest effective price falls from $84.21/mg listed to $75.79/mg at Alpha Peptides. Each vendor's code is shown beside its price in the table above.
Follistatin 344 ranges from $84.21/mg to $139.99/mg across 5 listings from 4 research peptide vendors, normalized to USD per milligram and refreshed daily.
4 research peptide vendors currently list Follistatin 344 on PeptideScouter, with 2 in stock right now. We track 5 listings across size and kit variants.
