Read this first: three different things share this name
"Follistatin 344" is attached to three separate objects, and most pages blur them. First, the molecule: 344 is the residue count of the full-length follistatin precursor, while the form that actually circulates is the shorter FS-315 (UniProt P19883). Second, the human evidence: every human study is gene therapy, an AAV1 vector carrying the FS344 gene injected into muscle and dosed in vector genomes, not milligrams of protein (PMID 25322757). Third, the product sold online: a recombinant protein in milligram vials, and when a doping laboratory analysed 17 of them, only nine contained follistatin at all (PMID 31758732). This page keeps the three apart and does not treat the trial evidence as support for the injectable product.
Follistatin-344
The 344 form is the precursor of follistatin, a glycoprotein that antagonizes myostatin, activin and related TGF-beta ligands. Every human study is AAV gene therapy dosed in vector genomes, not the milligram protein vials sold online, and no follistatin formulation is approved anywhere.
Last updated: September 2026
Category
Muscle Growth
Frequency
Not established (research compound)
Research
Preclinical, gene therapy trialsWhat is Follistatin-344?
Follistatin-344 is not really a peptide. It is a 344 residue glycoprotein of about 38 kDa (UniProt P19883), roughly ten times the size of the short peptides in our peptide library. The number 344 counts the amino acids in the follistatin precursor, and that precursor carries a 29 residue signal peptide that is cleaved off during secretion, so the form that actually circulates is the shorter 315 residue protein, FS-315.
Its role is to antagonize members of the TGF-beta superfamily. Follistatin binds activin, myostatin, GDF11 and BMPs and blocks them from reaching their receptors (UniProt P19883). Myostatin is the ligand that made it famous, because myostatin normally limits muscle growth, but follistatin is a broad trap rather than a myostatin-only drug. The FS344 variant was chosen for the gene therapy trials precisely because its FS315 product binds activin much more weakly than the alternative FS288 form, which limits the effect on the pituitary and on follicle stimulating hormone (PMID 27858738).
What is actually sold online is a different object again. A 2026 review in Sports Medicine lists FS-344 among grey market peptides marketed direct to patients, alongside BPC-157 and TB-500 (PMID 41966639). No regulator has approved a follistatin formulation, the substance is prohibited in sport, and when a doping laboratory analysed 17 vials sold as follistatin 344, only nine contained follistatin at all (PMID 31758732). For the myostatin-pathway sibling compound, see the ACE-031 profile.
How It Works
Ligand trap, not a receptor drug. Follistatin binds TGF-beta superfamily ligands, including activin, myostatin, GDF11 and BMPs, in the space outside the cell and blocks their type II receptor binding site, which stops the downstream signal (UniProt P19883).
Myostatin inhibition is one item on that list, not the whole story. Blocking myostatin is the part that connects follistatin to muscle growth, but the same protein also sequesters activin and the other ligands, so its effects are broad rather than muscle-specific (UniProt P19883).
The pituitary is the off-target that shaped the research. Follistatin suppresses follicle stimulating hormone by sequestering activin A, a reproductive-axis effect, so the trials used the FS344 variant whose FS315 product binds activin about 10-fold more weakly than the FS288 form (UniProt P19883, PMID 27858738).
In people, the gene was delivered, not the protein. An AAV1 viral vector carrying the FS344 coding sequence was injected into the quadriceps, and the muscle cells then produced follistatin locally, which is why trial doses are counted in vector genomes per kilogram rather than milligrams (PMID 25322757).
Benefits
- Increased muscle size and strength in monkeys given the AAV gene therapy vector (animal study, cynomolgus macaque, intramuscular, PMID 20368179)
- Improved walking distance in some Becker muscular dystrophy patients after gene therapy, though 2 of 6 did not improve at all (human gene therapy trial, PMID 25322757)
- A higher lean meat percentage in pigs genetically engineered to make follistatin in muscle, 72.95% versus 69.18% (transgenic animal model, PMID 27787698)
- A reported walk-test gain in sporadic inclusion body myositis, which a published critique argues the trial design cannot support (human gene therapy trial, disputed, PMID 28279643, PMID 28927986)
- Mechanistically antagonizes myostatin, activin, GDF11 and BMPs by blocking their type II receptor binding site, the basis for the muscle interest (protein biology, UniProt P19883)
Dosing Described in Research and Labels
| Phase | Dose | Frequency | Duration |
|---|---|---|---|
| Injectable product sold as "follistatin 344" | No approved formulation and no established dose | Grey market milligram vials, subcutaneous | Not a studied drug; contents often do not match the label (PMID 31758732) |
| Human gene therapy trial: Becker muscular dystrophy | 3 x 10^11 then 6 x 10^11 vg/kg per leg, by cohort (trial dose, not a recommendation, PMID 25322757) | AAV1.CMV.FS344 vector, bilateral intramuscular quadriceps injection | n=6; 6-minute walk test primary outcome, 2 of 6 did not improve (PMID 25322757) |
| Human gene therapy trial: sporadic inclusion body myositis | 6 x 10^11 vg/kg (trial dose, not a recommendation, PMID 28279643) | rAAV1.CMV.huFS344 into both quadriceps, with an exercise regimen | n=6 treated; a published critique disputes the outcome (PMID 28279643, PMID 28927986) |
| Trial registry dose escalation, NCT01519349 | 2 x 10^11, 3 x 10^11, then 6 x 10^11 vg/kg across three cohorts (trial registry, not a recommendation, NCT01519349) | Single leg at the low dose, then per quadriceps | 15 enrolled; the registered primary outcome was safety, not walk distance (NCT01519349) |
| Animal study: nonhuman primate | Dose not stated in the abstract (animal study, cynomolgus macaque, intramuscular, PMID 20368179) | AAV1-FS344 injected into the quadriceps | Durable increases in muscle size and strength reported (PMID 20368179) |
| Animal study: transgenic pig | No dose; nothing was administered (transgenic model, PMID 27787698) | Follistatin expressed from the animal genome in muscle, not injected | Higher lean meat percentage than wild type, 72.95% vs 69.18% (PMID 27787698) |
| Grey market use, adverse event series | Users injected complete 1 mg vials (community practice, not a recommendation, PMID 32671599) | Subcutaneous, in the abdomen | 11 bodybuilders who developed a retinal condition, CSCR (PMID 32671599) |
These figures summarise what published research and approved labels describe. They are educational, not a recommendation or a personal protocol. Any dose, schedule, or decision to use a compound belongs with a licensed prescriber.
Side Effects
Reported in humans
- ⚠Central serous chorioretinopathy, a fluid buildup under the retina that blurs vision, in 11 bodybuilders after high-dose subcutaneous injection; it cleared in about 2 months in those who injected once (PMID 32671599)
- ⚠Recurrent retinal fluid in the 3 users who injected more than once (PMID 32671599)
- ⚠No adverse effects were reported in the Becker gene therapy trial, though that is the vector, not the injectable product (PMID 25322757)
Mechanism and trial notes
- •Product identity risk: only 9 of 17 black market vials contained follistatin, and some held other growth peptides such as MGF or GHRP-2 (PMID 31758732)
- •The follistatin that was present was His-tagged and formed oligomers, features of a lab construct rather than natural human follistatin (PMID 31758732)
- •A published critique argued the sporadic IBM trial understated fall frequency, reporting 33% of patients as 6% (PMID 28927986)
- •Reproductive-axis effect by design: follistatin suppresses follicle stimulating hormone through the activin pathway (UniProt P19883, PMID 27858738)
Who Should NOT Use Follistatin-344
- ✕Competitive or drug-tested athletes: follistatin is prohibited in sport under class S4 of the WADA list (PMID 31758732)
- ✕Anyone who cannot verify what is in the vial: fewer than half of tested black market products actually contained follistatin, and some contained other growth peptides (PMID 31758732)
- ✕Anyone concerned about the reproductive axis: the protein suppresses follicle stimulating hormone by design, the effect the researchers deliberately engineered around (UniProt P19883, PMID 27858738)
- ✕Anyone expecting the injectable product to reproduce the trial results: the human trials delivered a gene therapy vector into muscle, a different intervention from a milligram vial injected under the skin (PMID 25322757, PMID 31758732)
What to Expect
The label may not match the contents. In the one forensic analysis, only 9 of 17 vials sold as follistatin 344 contained follistatin, and some held other growth peptides (PMID 31758732).
The human evidence is gene therapy dosed in vector genomes, so it does not tell you what a milligram protein vial will do in a healthy person (PMID 25322757, PMID 28279643).
A case series linked high-dose subcutaneous injection to central serous chorioretinopathy, which recurred in everyone who injected more than once (PMID 32671599).
It is prohibited by WADA under class S4, and a urine test for the His-tagged black market form has been published (PMID 31758732).
Notes from Ho Chi Minh City
Follistatin comes up in Ho Chi Minh City gym conversations as the myostatin story, the idea that you can release the brake on muscle growth. What gets lost is that the human evidence people half-remember is gene therapy, an AAV vector injected into the quadriceps in a muscular dystrophy trial, not the milligram vial sold through grey channels here (PMID 25322757). The vial is a different object: when a doping laboratory actually tested 17 of them, fewer than half contained follistatin, and the ones that did carried a His-tag that natural human follistatin does not have (PMID 31758732). The retinal-fluid case series in bodybuilders is the part that should slow anyone down (PMID 32671599). Dose, route, and whether to touch it at all are decisions for a licensed physician, not a forum thread.
Sourcing in Vietnam
There is no approved follistatin formulation anywhere, so it is not stocked at Long Châu, Pharmacity, or any retail pharmacy in Vietnam, and this page carries no price or vendor figure because the research file records none. What the market sells is a grey market recombinant protein, and the single forensic analysis of it found that only 9 of 17 vials contained follistatin at all, and some of the others contained different growth peptides such as MGF or GHRP-2 (PMID 31758732). The substance is prohibited in sport under WADA class S4, and a urine test for its His-tagged black market form has been published (PMID 31758732).
FAQ
Q: Is follistatin 344 a peptide or a protein?
A: It is a protein. Specifically it is a 344 residue glycoprotein of about 38 kDa (UniProt P19883), roughly ten times the size of the short peptides this library usually covers. The number 344 counts the amino acids in the precursor, including a 29 residue signal peptide that is cleaved off, so the mature form that circulates is FS-315.
Q: Did the human trials inject follistatin protein?
A: No. Every human study delivered a gene, not the protein. An AAV1 viral vector carrying the FS344 coding sequence was injected into the quadriceps, and muscle cells then produced follistatin locally. Doses were measured in vector genomes per kilogram, not milligrams (PMID 25322757, PMID 28279643).
Q: What is actually in a vial sold as follistatin 344?
A: Often not follistatin. When a doping control laboratory analysed 17 black market products, only 9 contained follistatin, and some of the others contained different growth peptides such as MGF or GHRP-2. All 9 that did contain follistatin carried a His-tag, a laboratory purification handle that natural human follistatin does not have (PMID 31758732).
Q: Is there a separate 2020 follistatin 344 study?
A: No. The 2020 record with the same title is a published correction to the 2019 black market analysis, not a second study (PMID 33460286 corrects PMID 31758732).
Q: What side effect has been reported in people who injected it?
A: A retrospective case series described 11 male bodybuilders who developed central serous chorioretinopathy, a fluid buildup under the retina that blurs vision, after high-dose subcutaneous injection of 1 mg vials. It cleared within about two months in those who injected once but recurred in the three who injected repeatedly (PMID 32671599).
Q: Is follistatin 344 approved or legal?
A: No regulator has approved any follistatin formulation, and it is prohibited in sport under class S4 of the WADA list. There is no established human dose for the injectable product, and this page does not provide one (PMID 31758732).
Where to Get Follistatin-344 in Vietnam
See our community-verified supplier list with COA verification and cold-chain shipping to Vietnam.
Related Peptides
Related Guides
Research & Sources
- UniProtKB P19883 (FST_HUMAN): Follistatin, Homo sapiens, reviewed entry · UniProt Knowledgebase (2026) Link
The definitive statement of what 344 counts: a precursor of 344 residues, signal peptide 1 to 29, mature chain 30 to 344, 38007 Da, with isoforms FS-315 and FS-288.
- A phase 1/2a follistatin gene therapy trial for Becker muscular dystrophy · Molecular Therapy (2015) (PMID: 25322757)
First human use of FS344, delivered as an AAV1 gene therapy vector by intramuscular quadriceps injection. Two of six patients did not improve on the walk test.
- Follistatin Gene Therapy Improves Ambulation in Becker Muscular Dystrophy · Journal of Neuromuscular Diseases (2015) (PMID: 27858738)
States the FS344 to FS315 relationship and that the FS315 product binds activin with about 10-fold lower affinity than FS288, which is why FS344 was chosen.
- Follistatin Gene Therapy for Sporadic Inclusion Body Myositis Improves Functional Outcomes · Molecular Therapy (2017) (PMID: 28279643)
Second human use, gene therapy at 6 x 10^11 vg/kg into both quadriceps, with an exercise regimen. The reported outcome is disputed by a published critique.
- Unfounded Claims of Improved Functional Outcomes Attributed to Follistatin Gene Therapy in Inclusion Body Myositis · Molecular Therapy (Letter) (2017) (PMID: 28927986)
Published critique: the registered primary outcome was safety, not the walk test; treated subjects received four possible interventions including prednisone and exercise; one subject had no detectable transgene.
- Central serous chorioretinopathy associated with high-dose follistatin-344: a retrospective case series · International Ophthalmology (2020) (PMID: 32671599)
The only human adverse event series in people who injected the grey market product: 11 male bodybuilders, complete 1 mg vials subcutaneously, CSCR that recurred with repeat injection.
- Detection of black market follistatin 344 · Drug Testing and Analysis (2019) (PMID: 31758732)
Forensic analysis: only 9 of 17 vials contained follistatin; all 9 were His-tagged; some products contained other growth peptides. Prohibited under WADA class S4.
- Detection of black market follistatin 344 (Published Erratum) · Drug Testing and Analysis (2020) (PMID: 33460286)
A correction to the 2019 analysis, not a separate study.
- Follistatin gene delivery enhances muscle growth and strength in nonhuman primates · Science Translational Medicine (2009) (PMID: 20368179)
Cynomolgus macaque, AAV1-FS344 into the quadriceps. Dose not stated in the abstract. The authors state only that therapy may help certain muscle disorders.
- The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs · Transgenic Research (2017) (PMID: 27787698)
A genetic model, not a dosing study: transgenic Duroc pigs expressing follistatin in muscle, higher lean meat percentage. Nothing was administered, so there is no dose or route.
- Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance · Sports Medicine (2026) (PMID: 41966639)
A 2026 narrative review that names FS-344 among grey market peptides marketed direct to patients, alongside BPC-157, CJC-1295 and TB-500.
- NCT01519349: Phase I Intramuscular Gene Transfer of rAAV1.CMV.huFollistatin344 to Patients With Becker Muscular Dystrophy and Sporadic Inclusion Body Myositis · ClinicalTrials.gov registry (2012 to 2017) Link
The registry record: interventional, phase 1, 15 enrolled, three dose cohorts (2E11, 3E11, 6E11 vg/kg). The registered primary outcome is safety, not the walk test.
Important Disclaimer
Educational content only. Not medical advice. Peptides discussed on this page are not approved by Vietnam’s Ministry of Health (Bộ Y Tế) or the Drug Administration of Vietnam (DAV) for the indications described. Research peptides are not stocked at Long Châu, Pharmacity, or any retail pharmacy in Vietnam. Consult a licensed physician before any use.