Molecular profile
- Molecular Weight
- ~37.8 kDa
- Synonyms
- Activin-binding protein, FSH-suppressing protein, FST-344
Follistatin-344
Follistatin-344 neutralizes myostatin, activin, and FSH, supporting muscle, fibrosis, endocrine, and regenerative research.
Dosing & scaling, explained
The moderated mass amounts below are retained for comparison. Near-duplicates, mix-dependent volumes and device markings are excluded. This is educational source context, not a protocol or recommendation.
Mass amounts available for comparison
- Lower range100 mcgDose
Recorded example with no verified study backing; shown for amount literacy only.
- Mid range300 mcgDose
Recorded example with no verified study backing; shown for amount literacy only.
Only mcg or mg amounts are retained. The calculator derives mL, syringe units or pen clicks from the current vial strength, water volume and device.
No independently verified schedule
Evidence context
No clinical amount or schedule is inferred from this material. Source verification is pending, and every displayed amount remains educational context rather than guidance.
Storage, handling and interpretation
Product identity
Verify the exact compound, formulation and amount against the product label or certificate before calculation.
Storage & handling
Follow the product label, certificate and validated laboratory SOP; no universal storage assumption is applied here.
Prepared solutions
Label concentration and preparation date, use sterile technique where applicable, and follow a validated stability protocol.
Reported protocols for Follistatin-344
What published studies and recent community write-ups report about amounts, timing and course length. 5 clinical, 1 preclinical and 4 community-reported rows, each linked to its source. These are descriptions of what others report, not instructions, and nothing here is medical advice.
| Context | Dose | Frequency | Route | Course | Source |
|---|---|---|---|---|---|
| Clinical5 rows | |||||
| Duchenne muscular dystrophy gene transfer, phase 1/2Boys and young men with Duchenne muscular dystrophy; 3 enrolled against a planned 6 | 2.4 x 10^12 vg/kg in total (1.2 x 10^12 vg/kg per limb) of rAAV1.CMV.huFS344 | Single administration, split between gluteal, quadriceps and tibialis anterior muscles | Intramuscular, multiple direct injections per muscle | One procedure; the study ran from January 2015 to November 2017Not applicable; gene transfer is a single event | ClinicalTrials.gov2015 |
| This is the highest vector dose and the widest muscle distribution of the three follistatin trials, scaled up from the single-muscle Becker work because that trial improved walking distance without adverse events. The registry lists it as completed with results posted and enrolment of 3 rather than the planned 6, and the number of injections per muscle depended on patient size. | |||||
| Registered three-cohort dose escalation15 patients with Becker muscular dystrophy or sporadic inclusion body myositis | 2 x 10^11 vg/kg to one quadriceps, then 3 x 10^11 and 6 x 10^11 vg/kg per quadriceps bilaterally | Single administration per participant | Intramuscular | One procedure, with safety as the primary endpoint over 2 yearsNot applicable | ClinicalTrials.gov2012 |
| The first cohort received a unilateral injection and only included inclusion body myositis patients; the second and third treated both quadriceps and split evenly between the two diseases. The study ran from 2012 to October 2017 and no results have been posted to the registry, although both disease groups were published separately. | |||||
| Becker muscular dystrophy results6 adults with Becker muscular dystrophy, in two cohorts of 3 | 3 x 10^11 vg/kg per leg (cohort 1) or 6 x 10^11 vg/kg per leg (cohort 2) | Single administration into both quadriceps | Intramuscular | One procedure, with the 6-minute walk test as the primary measureNot applicable | Molecular Therapy (PubMed Central)2015 |
| Two patients gained 58 m and 125 m on the walk test and one did not change at the lower dose; at the higher dose two gained 108 m and 29 m and one did not improve. Histology showed less endomysial fibrosis, less central nucleation and fibre hypertrophy, most marked at the high dose, and no adverse effects were reported. Six patients without a control group cannot establish efficacy. | |||||
| Sporadic inclusion body myositis results6 ambulatory adults with sporadic inclusion body myositis, against 8 untreated patients matched for age, sex and baseline | 6 x 10^11 vg/kg of rAAV1.CMV.huFS344 | Single administration to the quadriceps of both legs | Intramuscular | One procedure, with an exercise regimen alongside and results annualized to a median 1 yearNot applicable | Molecular Therapy (PubMed)2017 |
| Walking distance improved 56.0 m per year in treated patients while the comparison group declined 25.8 m per year. Four of the six gained 58 to 153 m and two gained only 5 to 23 m, biopsies showed less fibrosis and better regeneration, and the authors flag advanced disease with established muscle loss as the limit of the approach. Every participant also exercised, so the vector's contribution cannot be separated out. | |||||
| Single plasmid injection in volunteers43 adult volunteers of both sexes, aged 23-88, median age 46 | 50 mcg of FST-344 plasmid complexed with linear polyethyleneimine in 400 microlitres of saline | Single injection | Subcutaneous, into abdominal fat | One injection, with measurements at baseline and 3 monthsNone described | Minicircle Inc. (company preprint, medRxiv)2024 |
| Serum follistatin rose from a mean 8.58 ng/mL to 24.03 ng/mL at three months, which the authors call a largely supraphysiological level, alongside a mean 1.96 lb gain in fat-free mass, a 0.87% fall in body fat and a 7.10 year fall in extrinsic epigenetic age. It was single-arm with no control group, run and reported by the company selling the therapy, approved by a private clinic's own review board, limited to three months, and a minority of participants had a large rise in LDL cholesterol. | |||||
| Preclinical1 row | |||||
| Primate study that carried the approach into peopleCynomolgus macaque monkeys | 1 x 10^13 vector genomes in total per treatment, as three injections into one quadriceps | Single administration | Intramuscular | One procedure, with long-term follow-upNot applicable | Science Translational Medicine (PubMed)2009 |
| Muscle size and strength rose markedly and durably in the injected leg, and long-term expression produced no abnormal changes in the morphology or function of key organs, which was the safety argument for the human trials. The investigators had filed a provisional patent on follistatin gene delivery, and PubMed records an erratum to this paper published in August 2026. | |||||
| Community-reported4 rows | |||||
| Reference chart with no protocol claimed | About 50 mcg at the low end, about 100 mcg most often cited, up to about 200 mcg at the high end | Once daily | Subcutaneous | 10-30 day blocksNot specified beyond ending the block | Community resource2026 |
| This chart models a 1 mg vial in 2 mL of bacteriostatic water, giving 500 mcg/mL so that 100 mcg is 20 units on a U-100 syringe. It opens by stating that no validated human dose exists, that the figures are grey-market reports rather than dose-finding data, and that the only rigorous human data come from gene therapy rather than protein injection. | |||||
| Forum pattern recorded with a pharmacology objection | 50-100 mcg per injection, about 1 mg cumulative per cycle | Once daily | Subcutaneous, abdomen | 10-30 consecutive daysSeveral months between cycles | Community resource2026 |
| This guide documents the most-cited forum pattern and then argues against it: animal work puts the plasma half-life of FST-288 and FST-315 at minutes to roughly an hour, and the engineered Fc-fusion variants designed for sustained activity needed milligram-range doses, often intravenously. It concludes the 50-100 mcg daily pattern is most likely subpharmacologic and may be largely degraded at the injection site. | |||||
| Three tiers with matching on and off periods | 100 mcg (conservative), 100-200 mcg (standard), 200-300 mcg (upper tier) | Once daily, or twice daily at the upper tier; morning timing suggested | Subcutaneous, abdomen, thigh or upper arm | 10-14 days, 10-20 days or 20-30 days by tier20-30 days off after a 10-day block, 40-60 days after 20 days, 60-90 days after 30 days, 1-3 cycles a year | Community resource2026 |
| This chart is the only one that pairs each cycle length with a specific off period and it lists reproductive concerns as the reason the longest block carries the longest break. It describes the upper tier as having more unknowns with no established benefit ceiling, and advises using reconstituted vials within 14 to 21 days. | |||||
| Isoform comparison used to justify choosing 344 | 100-200 mcg per day | Once daily, which the page ties to a circulating half-life of about 90 minutes | Subcutaneous | 10-30 days3-4 weeks off | Community resource2026 |
| This guide argues that FS-344 and FS-315 are functionally equivalent for injection because the 344 precursor is cleaved to FS-315 in the blood, and recommends 344 on the grounds that it is more stable as a recombinant protein, more widely available and backed by the gene therapy literature. The stability and availability claims are the vendor-side argument rather than measurements, and it is clear that the 344 figure is a full-length protein of about 38 kDa rather than a short synthetic chain. | |||||
How a course is commonly described
- Days 1-10Community-reported
The shortest community block is 100 mcg once daily for ten days, presented as the lowest-exposure way to assess tolerance. At the usual reconstitution of a 1 mg vial in 2 mL of bacteriostatic water, that is 20 units on a U-100 syringe.
- Days 10-20Community-reported
The most commonly described block runs 100 to 200 mcg once daily for 10 to 20 days, with daily consistency presented as more important than the time of day. No biomarker or endpoint is given for judging whether it is working.
- Days 20-30Community-reported
The longest block described is 20 to 30 days, with roughly 1 mg of protein in total per cycle, after which guides advise stopping rather than extending. One of them notes in the same breath that this cumulative amount is far below what engineered follistatin needed to do anything measurable in animals.
- Off periodCommunity-reported
Breaks are described as 3 to 4 weeks at the short end and 60 to 90 days after a 30-day block, with one to three cycles a year. The stated reasons are cost and reproductive caution from activin blockade, not any published recovery measurement.
- Clinical comparisonClinical
In people, FS344 has only ever been given once. The Duchenne trial delivered 2.4 x 10^12 vg/kg of vector split across gluteal, quadriceps and tibialis anterior muscles in a single session, and the Becker and inclusion body myositis trials used 2 x 10^11 to 6 x 10^11 vg/kg per quadriceps, with outcomes measured over the following one to two years. There is no repeated-dose protein schedule to compare the charts above against.
- No human study has injected follistatin protein by any route, so there is no validated dose, frequency or cycle length for the vials sold under this name. All human FS344 data are single-event gene transfer measured in vector genomes, or one 50 mcg plasmid injection, neither of which converts into a microgram protein dose.
- The community guides themselves report the pharmacology that undercuts their own figures: a plasma half-life of minutes to roughly an hour in animals, and engineered Fc-fusion follistatins that needed milligram-per-kilogram dosing twice weekly to produce hypertrophy and anti-fibrotic effects in dystrophic mice. A flat 50-200 mcg once a day is several orders of magnitude below that exposure.
- Follistatin interacts with the pituitary activin and inhibin axis and can suppress follicle-stimulating hormone, which is exactly why the gene therapy programme used the 344 variant that matures into the lower-affinity serum form. Follistatin is approved nowhere, raised reproductive and metabolic questions in both the trial literature and the community guides, and is on the WADA prohibited list.
Sources for this section (15)
- Clinical Intramuscular Gene Transfer of rAAV1.CMV.huFollistatin344 Trial to Patients With Duchenne Muscular Dystrophy (NCT02354781)
- Follistatin Gene Transfer to Patients With Becker Muscular Dystrophy and Sporadic Inclusion Body Myositis (NCT01519349)
- A phase 1/2a follistatin gene therapy trial for Becker muscular dystrophy
- Follistatin Gene Therapy for Sporadic Inclusion Body Myositis Improves Functional Outcomes
- Follistatin Gene Therapy Improves Ambulation in Becker Muscular Dystrophy
- Plasmid delivery of follistatin gene therapy safely improves body composition and lowers extrinsic epigenetic age in sex- and age-diverse adult human subjects
- Follistatin gene delivery enhances muscle growth and strength in nonhuman primates
- Myostatin and activin blockade by engineered follistatin results in hypertrophy and improves dystrophic pathology in mdx mouse more than myostatin blockade alone
- Regulation of myostatin activity and muscle growth
- Overcoming Insulin Insufficiency by Forced Follistatin Expression in beta-cells of db/db Mice
- Biological activity of follistatin isoforms and follistatin-like-3 is dependent on differential cell surface binding and specificity for activin, myostatin, and bone morphogenetic proteins
Plus 4 community resources (dosing guides, forum threads and vendor write-ups), reported above but not linked.
Overview
Follistatin-344 is the longer of the two splice variants of the human FST gene: a 344-residue precursor (UniProt P19883, computed mass 38,007 daltons) whose first 29 residues are a signal peptide, so what the cell actually secretes is the 315-residue circulating protein FST-315. Every human study of follistatin has used this variant rather than injected protein, and the choice was deliberate, because the variant matures into the serum form with roughly ten-fold lower activin affinity than FST-288 and was therefore expected to add muscle without suppressing follicle-stimulating hormone through the pituitary activin axis. Nationwide Children's Hospital delivered rAAV1.CMV.huFS344 into the leg muscles of patients with Becker muscular dystrophy, sporadic inclusion body myositis and Duchenne muscular dystrophy between 2012 and 2017, and a company clinic in Honduras injected an FST-344 plasmid into the abdominal fat of 43 volunteers in a study published as a preprint in 2024. PubChem holds no compound record for any follistatin isoform, so there is no molecular formula, CAS number, InChIKey or molar mass to report here; the protein is indexed only under accession P19883, and the identifier quoted on older pages (178101631) is a PubChem substance number rather than a compound record. Vials sold as Follistatin-344 contain recombinant protein rather than the vector or plasmid the studies used, no human study has injected follistatin protein by any route, and follistatin is not approved anywhere and sits on the WADA prohibited list.
What researchers are exploring
These themes organize the educational information currently available. Individual claims remain under source review and are not treatment claims.
- 1
Muscle & Regenerative Research
Applications in dystrophy, fibrosis, and gene therapy
- 2
Oncology & Cell Proliferation
Balancing growth and metastasis suppression
- 3
Additional Research Areas
Barrett’s esophagus, dermatology, and metabolic health
- 4
Summary
Research considerations
What is known and what still needs verification
Available context is organized without assigning unsupported study models or evidence grades.
- Not graded
Muscle & Regenerative Research
Applications in dystrophy, fibrosis, and gene therapy
- Not graded
Oncology & Cell Proliferation
Balancing growth and metastasis suppression
Amounts recorded for Follistatin-344
These amount records are independent from vial strength, reconstitution volume and measuring device. A recorded source is not the same as study backing, and these values are not recommendations.
- 1Dose · lower endpointSign in for schedule, duration and source context.100 mcg
- 2Dose · upper endpointSign in for schedule, duration and source context.300 mcg
Identity, limitations and unknowns
Important limitations
- Individual claims and source links have not yet completed editorial verification.
- Evidence level, applicable study model, formulation, route and population remain unassigned.
Sources
1 link carried over from the earlier page, awaiting verification.