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
What the studies report
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.
What is not known
The limits of the published work on Follistatin 344, stated plainly. Research use only: none of this is guidance for a person.
The big muscle results come from gene therapy, where a virus carries the follistatin gene into muscle so the body keeps making the protein itself. That is a different thing from injecting the peptide, and one does not show what the other would do.
There is very little published work on injected follistatin peptide in people. The muscle figures quoted for this compound are not from it, so what the injected peptide does is not known.
The first human gene transfer work was a small early trial. A study that size cannot say whether a change came from the treatment or from the natural course of the disease.
Follistatin also affects the pituitary signal that controls follicle stimulating hormone. What repeated exposure does to that system in a healthy body has not been measured.
What happens years after the gene is delivered is not known, beyond the follow up each trial reports.
The terms, in plain words
Every technical term this page leans on, said again in ordinary words.
- Myostatin
- A natural signal that acts as a brake on how big a muscle fibre gets.
- Activin A
- A related natural signal that works through the same kind of brake.
- Gene therapy
- Delivering a gene into cells so the body makes the protein itself, instead of injecting the protein.
- AAV1
- A harmless virus used as the delivery van for that gene.
- Hypertrophy
- Muscle fibres getting bigger.
- Isoform
- One of several slightly different versions of the same protein.
Sources
The published work behind this entry. Each link was opened and each note says what that paper reports, not what it suggests.
- Follistatin gene delivery enhances muscle growth and strength in nonhuman primates Science Translational Medicine, 2009Monkeys. Gene delivery into the thigh muscle, not injected peptide. Reports larger and stronger muscle at the injected site.
- Follistatin Gene Therapy Improves Ambulation in Becker Muscular Dystrophy Journal of Neuromuscular Diseases, 2015A review of the follistatin gene therapy work, including the first gene transfer trial in people with Becker muscular dystrophy. Again gene delivery, not injected peptide.
How it is studied
In the published studies listed below. Each one names the species it was run in, the dose, how long it ran, and what it reported.
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.