Follistatin 344
Myostatin Inhibitor | TGF-β Antagonist for Muscle Research
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What is Follistatin 344?
Follistatin 344 is a lab-made version of a naturally occurring protein that blocks myostatin and a related signal (activin A), both of which normally act as brakes on muscle-tissue development. Most of what's known comes from gene-therapy studies in animals and a small human gene-therapy trial for muscular dystrophy — injectable peptide use has very little research behind it by comparison. Research-grade Follistatin 344 sold here is intended strictly for laboratory study, not for use in people or animals.
Key terms:
Follistatin 344 is a glycoprotein with follistatin domains.
Follistatin 344 (FS-344) is a natural protein with a sugar group attached. It blocks myostatin and activin A, two signals in the TGF-β family that hold muscle development back. The FS-344 gene codes for a 344-amino-acid precursor, which the body cuts down to the circulating FS-315 form. In gene-therapy studies in primates, and in human clinical trials for muscular dystrophy, researchers reported large muscle hypertrophy (muscle fibers getting bigger) and strength gains. Injected peptide is a different story: human data is very limited, the half-life is short (about 90 minutes), and most research used gene delivery rather than injected peptide. WADA has banned follistatin since 2019.
Key research areas
- Myostatin and activin A inhibition
- Potential muscle development enhancement
- Studied for muscular dystrophy therapy
Researched dosing
This table shows the injectable dosing researchers have anecdotally proposed for Follistatin 344 — since almost all the controlled research used gene-therapy delivery instead, these ranges are extrapolations, not clinically validated protocols.
| Phase | Dose | Frequency | Route |
|---|---|---|---|
| Community protocol (unverified) | 100 mcg | Once daily | SubQ |
| Higher-dose protocol (unverified) | 200 mcg | Once daily (max recommended) | SubQ |
Commonly cycled 4 weeks on, 3+ weeks off.
How it works
At the cell level, Follistatin 344 research looks at how the protein binds and neutralizes myostatin and activin A before they can reach their receptors on muscle cells — removing two separate brakes on muscle-tissue development rather than adding a growth signal.
Binds and neutralizes myostatin and activin A, preventing their interaction with ActRIIB receptors on muscle cells. This blocks TGF-β signaling that normally suppresses muscle development, allowing enhanced hypertrophy.
Molecular data
These figures — molecular weight, chain length, sequence — are the chemistry ID researchers use to confirm a Follistatin 344 sample's identity; at 344 amino acids, it's a much larger molecule than most compounds in this encyclopedia.
- Weight
- 37800 Da
- Length
- 344 amino acids
- Type
- Glycoprotein with follistatin domains
Full sequence available in UniProt P19883
Pharmacokinetics
This chart shows how quickly a research dose of Follistatin 344 clears the body — notice the short, sub-hour timescale, which is part of why most of the muscle-research literature on this molecule uses sustained gene-therapy delivery rather than periodic injections.
- Peak
- 0.15 hr
- Half-life
- 1.5 hrs
- Cleared
- ~7.5 hrs
Datta-Mannan et al. 2013
Research applications
This section lists the research areas scientists have studied for Follistatin 344 — a summary of what's been studied in gene-therapy and preclinical literature, not medical claims about people.
Muscle Development
Blocks myostatin from binding to muscle cell receptors, removing natural growth suppression. Also inhibits activin A, providing dual-action anti-catabolic effect greater than myostatin-only inhibitors. Research suggests follistatin may directly promote satellite cell proliferation for muscle regeneration.
Recovery
Supports muscle regeneration and recovery through satellite cell activation and anti-catabolic mechanisms.
Dosage reference
- Doses used in research
- No established research dose; unverified community reports mention 100 mcg.
- Frequency in studies
- Once daily during short cycles
- Handling
- Reconstituted solution — research use only; not for administration
- Timeline reported in studies
- Gene therapy studies showed effects in 8-12 weeks. Injectable peptide effects poorly characterized due to short half-life.
- Storage
- Lyophilized: -20°C. Reconstituted: 2-8°C, use within 7 days
- Cycle length
- 10-30 days (anecdotal)
- Break between cycles
- 3-4 weeks minimum between cycles (anecdotal)
Interactions
This list shows which other muscle- and recovery-research peptides are studied alongside Follistatin 344, and why some combinations call for extra caution.
Reconstitution & storage
This is the standard laboratory method for turning freeze-dried Follistatin 344 powder into a liquid research solution.
- Store lyophilized powder at -20°C until use
- Add sterile/bacteriostatic water slowly down vial side
- Gently swirl - do not shake vigorously as protein may denature
- Solution should be clear - discard if cloudy
- Use reconstituted solution within 7 days
Lyophilized: -20°C, use within As per manufacturer specification
Reconstituted: 2-8°C, use within 7 days; never freeze
Open the Follistatin 344 reconstitution calculatorQuality indicators
These are the checks researchers use to confirm a Follistatin 344 sample is pure and correctly identified — quality control matters more here given how little injectable-peptide data exists for this compound.
Extremely limited human peptide data - Most research involves gene therapy, not injectable peptide. Efficacy and safety of subcutaneous peptide poorly established.
Very short half-life (~90 minutes) - Native follistatin is rapidly cleared. Systemic muscle effects from daily injection are questionable without sustained release formulation.
WADA banned substance - Prohibited in sports since 2019. Subject to doping detection methods.
Excessive dosing risk - Case report of central serous chorioretinopathy (vision impairment) at 1mg single dose (10x typical). Never exceed 200mcg/day.
Third-party testing essential - Given limited regulation and high potential for counterfeit, COA verification is critical.
What to expect
This timeline reflects what the gene-therapy and preclinical literature reports at each study stage — research context for comparing studies, not a personal-results promise, and injectable-peptide timelines are far less established.
No reliable timeline established for injectable peptide use
Gene therapy studies showed measurable changes by week 8; injectable peptide effects likely much more modest due to rapid clearance
Safety notes
This section covers regulatory status and handling cautions for Follistatin 344, including its WADA-prohibited status since 2019 — reference context for laboratory researchers, not medical guidance.
- Not recommended for those with active cancer due to growth factor modulation
- Contraindicated in pregnancy - follistatin affects reproductive signaling
- Potential FSH suppression - may affect reproductive function
- WADA banned substance since 2019
- Not FDA-approved for human use
- Most safety data is from gene therapy, not injectable peptide
Regulatory status
- Not approved by the FDA for any indication.
- Prohibited by the World Anti-Doping Agency (WADA) — added to the Prohibited List in 2019.
- Supplied and described for laboratory research use only — not for human or veterinary use.
Community data
Community Insights
Based on data the community reported. Not clinical proof.
References
AAV1-FS344 injection into quadriceps produced 15% circumference increase at 8 weeks, persisting 15+ months. Muscle fiber diameter increased significantly (87.7 μm vs 65.5 μm control). No adverse effects on cardiac, reproductive, or organ systems.
First human gene therapy trial. Patients showed 6-minute walk test improvements up to +125 meters. High-dose patients showed muscle fiber diameter increase (40→59 μm) and 35-43% reduction in fibrosis. No serious adverse events. Hormone levels remained normal.
Transgenic mice expressing high follistatin levels showed 194-327% muscle mass increase. FS-344 produced greatest effects among tested inhibitors. Effects persisted over 2 years without adverse events in animal models.