Follistatin-344
Also known as: FST-344, Follistatin isoform 344
Follistatin-344 (also called FST-344 or Follistatin isoform 344) is a myostatin-binding glycoprotein in the Myostatin inhibitor class. Follistatin-344 is a glycoprotein that acts as a high-affinity binding trap for TGF-beta superfamily ligands, most importantly myostatin and activin A.
For research use only.
Key Facts
- CAS
- 1461868-87-4
- Molecular Weight (MW)
- ≈38–40 kDa (glycosylation dependent)
- Half-life
- Varies; protein biologic
- FDA status
- Not Approved
- Evidence level
- Insufficient Evidence
- Human dose established
- No
- Administration Route
- Not established in humans
- Frequency
- Not established in humans
- Last updated
- Sep 6, 2026
- Reviewed
- Aug 30, 2026
- Targets
- Myostatin (GDF8)Activin A
Vendor price snapshot
Each vendor counts once, at the median price per mg of its own listings; the typical range is the middle half of vendors. From public vendor listings collected in Dec 2025, so confirm the live price on the vendor site. Peptide Library does not sell peptides.
- Vendors listing this peptide
- 8
- Listed offers
- 8
- Median price per mg
- $155.00/mg
- Typical $120.00–$155.00/mg
Research summary
Isoform of follistatin that binds myostatin/activin. Gene-therapy and research-peptide forms exist; no FDA-approved follistatin drug. WADA prohibits myostatin inhibitors (S4).
Peptide Library's Follistatin-344 profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Follistatin-344 dosage: no established human dose
Follistatin-344 has no established human dosage. Human trials that mention follistatin are gene therapy studies - they deliver the follistatin gene by viral vector or plasmid, not injections of the protein - and the large body of human follistatin literature measures the protein the body already produces. No trial has administered follistatin-344 as an injectable peptide at a stated dose.
No established human dosage.
Human clinical evidence: None identified.
Preclinical research: Follistatin is an endogenous glycoprotein that binds and neutralises myostatin and activin, which is why it attracts interest for muscle growth. Follistatin-344 is one of its isoforms. The human research programme has gone almost entirely down the gene therapy route - delivering the coding sequence by viral vector or plasmid so the body produces the protein - rather than injecting the protein itself. That approach has its own dosing units and cannot be translated into a milligram dose of injected peptide.
Animal dosing is not converted into a human dose anywhere on this page. Where research figures appear below, they are reported as studied, not recommended.
| Human dosing established | No |
|---|---|
| Route | Not established in humans |
| Evidence level | Insufficient Evidence |
| Last reviewed | 2026-09-05 |
Preclinical and analog research
Not human dosing evidence. Listed for completeness and never extrapolated to a human dose.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| NCT01519349 - follistatin gene transfer, phase 1Clinical trial · Phase 1 gene therapy trial - delivers the gene, not the proteinStudied an analog, not Follistatin-344 itself | Patients with Becker muscular dystrophy (n=15) | Gene transfer by viral vector; not a peptide dose | Intramuscular gene transfer | — | — | Safety and muscle response | NCT01519349 - Follistatin Gene Transfer to Patients With Becker Muscular Dystrophy |
| NCT06411366 - injectable follistatin plasmid gene therapy, phase 1Clinical trial · Phase 1 gene therapy trial - delivers the gene, not the proteinStudied an analog, not Follistatin-344 itself | Participants (n=43) | Plasmid gene therapy; not a peptide dose | Injection of a plasmid construct | — | — | Safety and efficacy | NCT06411366 - Phase I: Safety and Efficacy of an Injectable Follistatin Plasmid Gene Therapy |
| NCT07443826 - AAV-follistatin for age-related muscle lossClinical trial · Phase 1/2 gene therapy trial, recruitingStudied an analog, not Follistatin-344 itself | Participants (n=12) | AAV vector dose; not a peptide dose | Vector administration | — | — | Age-related loss of muscle | NCT07443826 - CALM-AF-AI: Counteracting Age-related Loss of Muscle With AAV-Follistatin |
Where sources disagree
- Protocols of 100 mcg daily over 10 to 30 day cycles are widely published for follistatin-344. No trial has administered the protein by injection at a stated dose, and no primary source for those figures could be identified.
- Every registered human trial returned for follistatin is gene therapy. Those studies are flagged here as analog evidence because delivering a gene is not the same intervention as injecting a protein, and their dosing does not transfer.
- The large volume of human follistatin publications largely measures circulating endogenous follistatin as a biomarker in exercise and nutrition studies. Those are not studies of administering follistatin.
Reconstitution
Common research vial sizes: 1 mg.
| Vial | Bacteriostatic water | Concentration | Per 0.01 mL |
|---|---|---|---|
| 1 mg | 2 mL | 0.5 mg/mL | 5 mcg per 0.01 mL |
These figures are arithmetic only — they convert a vial and a volume into a concentration. They are not a recommendation to take any dose.
Calculate reconstitution & dose →Handling & administration
- Timing Notes
- Binds myostatin/activin; gene therapy approaches also exist
Sequence & molecular data
| Molecular formula | Protein (glycoprotein); sequence length 344 aa |
|---|---|
| Molecular weight | ≈38–40 kDa (glycosylation dependent) |
| CAS number | 1461868-87-4 |
| Half-life | Varies; protein biologic |
| Appearance | Lyophilized protein powder (research) |
| Formulation | Lyophilized Powder |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
Follistatin-344 is a glycoprotein that acts as a high-affinity binding trap for TGF-beta superfamily ligands, most importantly myostatin and activin A. Myostatin normally restrains skeletal muscle growth by signalling through activin type II receptors and ALK4/5 to activate SMAD2/3; follistatin binds it in the extracellular space so it cannot engage those receptors, relieving the inhibition. In animal models this produces substantial muscle hypertrophy. Two limitations matter: follistatin also neutralises activins with roles in reproduction and inflammation, so the effect is not myostatin-specific, and the 344 isoform binds cell-surface heparan sulfate, which restricts its distribution. There are no controlled human data.
Origin
Recombinant / synthetic glycoprotein isoform.
Targets
Studies
- Detection of black market follistatin 344
- Central serous chorioretinopathy associated with high-dose follistatin-344: a retrospective case series
- Detection of black market follistatin 344
- The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs
- Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance
Regulatory & research status
Follistatin-344 is not an FDA-approved product. It is sold for laboratory research and has no approved medical use.
| FDA status | Not Approved |
|---|---|
| Availability | Research-Only |
| WADA (sport) | Banned in Sport |
| Library classification | Research-Only |
Benefits
Follistatin-344 side effects
Follistatin-344 has no controlled human safety data. The effects below are reported, not established, and absence from the list is not evidence of safety.
Side Effects
- Unknown human peptide-vial safety
- Theoretical activin-related effects
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
Follistatin-344: frequently asked questions
What is Follistatin-344?
Isoform of follistatin that binds myostatin/activin. Gene-therapy and research-peptide forms exist; no FDA-approved follistatin drug. WADA prohibits myostatin inhibitors (S4).
How does Follistatin-344 work?
Follistatin-344 is a glycoprotein that acts as a high-affinity binding trap for TGF-beta superfamily ligands, most importantly myostatin and activin A. Myostatin normally restrains skeletal muscle growth by signalling through activin type II receptors and ALK4/5 to activate SMAD2/3; follistatin binds it in the extracellular space so it cannot engage those receptors, relieving the inhibition.
Is Follistatin-344 FDA approved?
No. Follistatin-344 is not approved by the FDA for any indication and is categorised as research-only. It has not been reviewed for safety or efficacy as a medicine, and published research should be read as investigation rather than established use.
What is the half-life of Follistatin-344?
Reported half-life for Follistatin-344 is Varies; protein biologic. Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.
Is Follistatin-344 banned in sport?
Follistatin-344 is recorded here as prohibited in sport. Athletes subject to anti-doping rules should check the current WADA Prohibited List directly, since it is revised annually and classifications change.
What peptides are similar to Follistatin-344?
Compounds most often compared with Follistatin-344 include ACE-031, GDF-11, MGF and AICAR. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- WADA Prohibited List 2026External reference
- Detection of black market follistatin 344 — Drug Test Anal, 2020External reference
- Central serous chorioretinopathy associated with high-dose follistatin-344: a retrospective case series — Int Ophthalmol, 2020External reference
- Detection of black market follistatin 344 — Drug Test Anal, 2019External reference
- The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs — Transgenic Res, 2017External reference
- Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance — Sports Med, 2026External reference
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Sep 6, 2026 · Version 2
This Follistatin-344 profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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