Gene-transfer trial
Walking-distance and biopsy endpoints were assessed roughly six months after the single procedure.
Protocol / Research Dosing Guide
Follistatin-344 Research Guide: Evidence Status, Vial Math and Safety
An evidence-organized Follistatin-344 reference. The published human work used a gene-transfer construct, not an injected research vial, so no protocol values are carried over to the vial format sold today.
Last reviewed September 15, 202615 minute readResearch information only
Level 2 — Gene-transfer and animal evidenceNo protein-injection human protocolNot FDA approved
Follistatin-344 Quick Start
FS344 is an alternatively spliced follistatin variant that antagonizes myostatin and other TGF-beta family ligands. Published human experience comes from an AAV1-delivered FS344 gene-transfer trial in Becker muscular dystrophy and inclusion body myositis. Vendor-sold lyophilized follistatin protein has no published human dosing protocol.
Why researchers care
Myostatin and activin pathway research in muscle biology
Class
Follistatin FS344 splice variant; secreted glycoprotein, not a short peptide
Route reported
Published human work used intramuscular gene transfer, not a reconstituted protein vial
Cycle length
Not established
Regulatory status
Not FDA approved; investigational gene-transfer use only
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Follistatin-344 Dosing Protocol and Schedule
The supplied protocol source has not published a dosing page for this compound; it lists the page as in progress. No schedule is reproduced here because none is supported by a primary source for the vial format.
| Phase or study | Amount | Frequency / evidence |
|---|---|---|
| Published human gene transfer, cohort 1 | 3 × 10^11 vg/kg per leg | Single bilateral intramuscular quadriceps injection |
| Published human gene transfer, cohort 2 | 6 × 10^11 vg/kg per leg | Single bilateral intramuscular quadriceps injection |
| Injected protein vial | Not established | No published human schedule |
The published amounts are viral-vector genome copies for a one-time surgical gene-transfer procedure. They cannot be converted into milligrams of a reconstituted protein vial and are not a schedule anyone can repeat at home.
Follistatin-344 Supplies Needed
Neutral research-material planning only. This does not establish an appropriate amount or route.
Research planning item
Exact labeled research vial
Research planning item
Measured diluent volume
Research planning item
U-100 measurement reference
Research planning item
Alcohol swabs
Research planning item
Appropriate sharps container
Research planning item
Written concentration label
Follistatin-344 Reconstitution Calculator
Vial-format concentration math
Concentration
1 mg/mL
Draw volume
0.1 mL
U-100 units
10
Mathematical draws
10
Arithmetic only. The entered amount is not a recommendation and does not establish suitability.
Best Time to Take Follistatin-344: Morning or Night?
Time of day?
Not established. No human protein-dosing study exists.
Frequency?
Not established. The published human work was a single procedure, not a repeating schedule.
With food?
Not applicable to an injected format and not established for any other format.
Missed amount?
Not applicable; no validated schedule exists to miss.
Follistatin-344 Route Comparison
| Route | What is reported | Evidence limit |
|---|---|---|
| Intramuscular gene transfer | Published phase 1/2a human trial | A surgical research procedure, not a vial protocol |
| Subcutaneous protein | Sold by research vendors | No published human exposure, dose, or safety data |
| Oral | Not established | A glycoprotein of this size is not expected to survive digestion intact |
| Route conversion | None available | Gene-transfer amounts and protein amounts are not comparable units |
Routes and amounts are not interchangeable unless a verified study explicitly establishes a conversion.
Follistatin-344 Half-Life and Dosing Frequency
| Measure | Finding | Evidence limit |
|---|---|---|
| Human half-life of injected FS344 protein | Not established | No published human PK study |
| Duration after gene transfer | Expression persisted in trial follow-up | Vector expression is not a protein half-life |
| Animal half-life | Not established for the marketed protein | Preclinical work used vector delivery |
| Frequency implication | Not established | No dosing interval can be derived |
Follistatin-344 Dosage Chart
| Route | Amount | Frequency | Source | Human validation |
|---|---|---|---|---|
| Intramuscular gene transfer | 3 × 10^11 vg/kg per leg | One-time | Published human trial | No |
| Intramuscular gene transfer | 6 × 10^11 vg/kg per leg | One-time | Published human trial | No |
| Subcutaneous protein vial | Not established | Not established | No primary source | No |
| Any other route | Not established | Not established | No primary source | No |
Published study values describe those studies. Community-reported values are not validated dosing recommendations.
Follistatin-344 Reconstitution Guide
Concentration: 1 mg/mL
| Entered amount | Volume | U-100 units |
|---|---|---|
| 0.1 mg | 0.1 mL | 10 units |
| 0.2 mg | 0.2 mL | 20 units |
| 0.3 mg | 0.3 mL | 30 units |
- 1.Confirm the exact vial label and total quantity.
- 2.Record the measured diluent volume.
- 3.Clean the vial stopper.
- 4.Add liquid slowly along the vial wall.
- 5.Swirl gently; do not shake.
- 6.Inspect for cloudiness, discoloration, or particles.
- 7.Label the calculated concentration and preparation date.
- 8.Use the result only for arithmetic, not as a recommendation.
Reconstitution does not establish identity, purity, sterility, stability, or an appropriate amount.
How Follistatin-344 Works
Pathway
Follistatin binds and neutralizes myostatin and related TGF-beta superfamily ligands, removing a brake on muscle growth.
Follistatin-344 Human Trials and FDA Status
Current status · verified September 15, 2026
Not FDA approved; investigational gene-transfer use only
- A phase 1/2a intramuscular AAV1.CMV.FS344 gene-transfer trial enrolled Becker muscular dystrophy participants and reported six-minute-walk and histology changes with no reported adverse effects.
- A registered trial extended follistatin gene transfer to sporadic inclusion body myositis; the study record is completed.
- Preclinical work used viral delivery of the follistatin gene, not injected recombinant protein.
- No human trial of injected recombinant follistatin protein was identified.
- Follistatin has no FDA-approved indication.
Who Should Avoid Follistatin-344?
This is an evidence-gap and precaution list, not an approved prescribing label.
Pregnancy or breastfeeding
No safety data; activin and follistatin biology are central to reproduction
Children or adolescents
No safety data for the protein format
Active or prior cancer
Myostatin and activin pathways interact with tumor biology
Reproductive or endocrine disorders
Activin-inhibin axis effects are a documented concern for follistatin isoforms
Concurrent medicines
No interaction studies
Cardiac or renal disease
Unstudied for this compound and format
Follistatin-344 Side Effects, Risks and Safety
Adverse effects after gene transferNone reported in the small phase 1/2a cohort
Important limitation: Six participants is far too small to characterize safety.
Injection-site reaction with vendor productUnknown
Important limitation: No published safety record.
Endocrine and reproductive effectsTheoretical
Important limitation: FS288 activin binding is why FS344 was selected; human protein data are absent.
ImmunogenicityUnknown
Important limitation: No characterized human data for the protein format.
Drug interactionsUnknown
Important limitation: No interaction studies.
Long-term effectsUnknown
Important limitation: No long-term follow-up for injected protein.
Follistatin-344 Timeline and Monitoring
Injected protein
No onset, peak, or duration is established.
Cycle structure
Not established.
Monitoring
No validated monitoring panel or stopping rule exists for the vial format.
Follistatin-344 Benefits and Results: What the Evidence Shows
| Claim | Evidence level | What research shows | Important limitation |
|---|---|---|---|
| Muscle size | Gene-transfer evidence only | Human histology after AAV1.FS344 | Not transferable to injected protein |
| Walking distance | Limited, uncontrolled | Improvements in some participants, none in others | Six participants, no control group |
| Fibrosis reduction | Gene-transfer evidence only | Biopsy findings | Small, unblinded |
| General strength or physique effects | Not established | Marketing claim | No human protein study |
Follistatin-344 Storage and Handling
Unreconstituted vial
Follow the exact product label; no independent stability study for vendor follistatin was located.
Prepared vial
No validated storage duration exists for this format.
Handling
Glycoproteins are generally handled cold and without agitation; this is general laboratory practice, not compound-specific evidence.
Appearance
Cloudiness or particles mean the material should not be used; clear appearance does not prove identity or purity.
Follistatin-344 Troubleshooting
Gene-transfer amounts quoted as a dose
Vector genome copies are not milligrams and cannot be converted.
Isoform confusion
FS288, FS303, and FS315 differ in binding behavior; the label isoform matters.
The vial size is far smaller than expected
Recombinant protein vials are commonly milligram or sub-milligram; recheck the label before any arithmetic.
Units do not match another chart
Recheck vial quantity, liquid volume, entered amount, and the U-100 conversion.
Product identity is unclear
Request batch-specific analytical documentation; the name alone does not identify the isoform or purity.
Follistatin-344 Comparisons
| Compound | Class or mechanism | Evidence | FDA status |
|---|---|---|---|
| Follistatin-344 (FS344) | Gene-transfer construct and vendor protein | Small human gene-transfer trial; no protein trial | Not approved |
| Follistatin-315 (FS315) | Circulating processed form of FS344 | Biochemical and preclinical characterization | Not approved |
| Myostatin inhibitors in trials | Antibody and receptor decoys | Multiple discontinued clinical programs | None approved for muscle growth |
| ACE-031 | ActRIIB-Fc decoy receptor | Development discontinued | Not approved |
Follistatin-344 Frequently Asked Questions
What is Follistatin-344?
An alternatively spliced follistatin variant, FS344, that antagonizes myostatin and related ligands. It is a glycoprotein, not a short peptide.
Has it been tested in humans?
Yes, but as a gene-transfer construct delivered by an AAV1 vector into thigh muscle, not as an injected vendor vial.
What amounts were used in the human trial?
3 × 10^11 and 6 × 10^11 vector genomes per kilogram per leg, given once.
Can those numbers be converted to milligrams?
No. Vector genome copies and protein milligrams are unrelated units.
Is there a dosing protocol for the vial sold online?
No published human dosing protocol was identified.
Is it FDA approved?
No.
What is its half-life?
Not established for the injected protein format.
Why was FS344 chosen over FS288?
FS344 is processed to FS315, which binds activin less strongly, chosen to limit effects on the pituitary activin-inhibin axis.
Are there safety data?
The six-participant gene-transfer cohort reported no adverse effects. That is not a safety characterization, and it says nothing about injected protein.
What does the calculator do?
It converts entered vial and liquid values into concentration and U-100 volume arithmetic only. It does not suggest an amount.
Sources and Research
Human clinical trial
1. A phase 1/2a follistatin gene therapy trial for Becker muscular dystrophy
Primary human evidence: AAV1.CMV.FS344 intramuscular gene transfer, vector-genome amounts, walking and histology endpoints.
Open direct sourceHuman research review
2. Follistatin gene therapy improves ambulation in Becker muscular dystrophy
Review of the FS344 isoform rationale, the activin-inhibin caution, and trial results.
Open direct sourceTrial registry
3. Follistatin gene transfer to patients with Becker muscular dystrophy and sporadic inclusion body myositis (NCT01519349)
Registry record for the completed intramuscular rAAV1.CMV.huFollistatin344 study.
Open direct sourceCoverage source
4. Follistatin protocol page (in progress)
Supplied coverage source; no dosing content was published at review time, so no schedule was carried over.
Open direct sourceMissing information flagged for review
- Human dosing study of injected follistatin protein: Not established
- Human pharmacokinetics and half-life: Not established
- Validated route, frequency, cycle, and rest period: Not established
- Safety and immunogenicity data for the vial format: Not established
- Independent product identity and isoform verification: Not established
- Long-term outcome data in any format: Not established