This page shows what was measured, who it was measured in, and what that does not settle.
What Follistatin-344 does in the body
Muscle cells make a protein called myostatin whose job is to stop muscle growing too much.
Follistatin is the natural trap for it: a larger protein that binds myostatin and a related protein called activin A, so neither can reach its receptor. Take the brake off and muscle grows. This is not a theory — cattle breeds with a broken myostatin gene are famously double-muscled. The way it has actually been tested in people is not by injecting the protein but by injecting a virus carrying the gene for it directly into the thigh muscles, so the muscle makes its own supply continuously. That distinction matters, because follistatin is a 344-amino-acid sugar-coated protein with a short life in blood, and a vial of powder is not a plausible way to deliver it.
Why people take it. An experimental gene treatment for muscle disease, also sold online as an untested injection.
What happened in people
In one gene-treatment study, four of six men walked farther after a year and two barely changed.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
No study has injected the online protein product, which may not contain the claimed full molecule.
Where it acts
Extracellular space of skeletal muscle, where myostatin and activin A circulate
Kind of result
The kind of result is not recorded
Supervision
Professional supervision is normally required. It is a prescription or clinician-administered medicine where it is approved.
Where each sentence above came from
A person wrote this explanation into the record, with the studies named in the path below.
A reviewer approved this sentence against this exact record and its sources.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 162 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Biomarker
A biomarker is a number from a test that stands in for something about health.
A picture of it, and where the picture fails
A biomarker is like a fuel gauge.
Where that stops being true. A gauge is wired to the tank. Many biomarkers are only loosely tied to health.
What people get wrong. A better number is read as a better life. Several medicines improved a number and helped nobody.
A measurable indicator used as a substitute for a clinical outcome of interest.
Placebo
A placebo is a dummy treatment given so the real one can be compared with it.
A picture of it, and where the picture fails
A placebo is like a blank control in an experiment.
Where that stops being true. A blank does nothing. People given a placebo often do get better.
What people get wrong. A placebo effect is read as imaginary. The improvement is measured and real.
An inactive intervention matched in appearance to the test intervention, used to control for non-specific effects.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Safety, with six-minute walk distance as the efficacy measure reported
✓ The study showed what it set out to show
Who was studied
NCT01519349 — AAV1.CMV.huFS344 in Becker muscular dystrophy and sporadic inclusion body myositis
How many people
15
Study design
Phase 1, open-label intramuscular gene transfer
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Inclusion body myositis: +56.0 m/year in treated subjects versus -25.8 m/year in 8 matched untreated subjects, p = 0.01; 4 of 6 improved 58-153 m and 2 improved 5-23 m. Becker: +58, +125, +108, +29 m in four patients and no change in two
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. No adverse effects were reported in the Becker cohort. Both cohorts were open-label with no randomised control arm; the inclusion body myositis comparison group was matched rather than randomised, and every treated participant also followed an exercise regimen.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Number of dose-limiting toxicity adverse events as assessed by 21 CFR 312.32
✓ The study showed what it set out to show
Who was studied
NCT02354781 — AAV1.CMV.huFollistatin344 in Duchenne muscular dystrophy
How many people
3
Study design
Phase 1/2, open-label intramuscular gene transfer
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Completed November 2017 with results posted to ClinicalTrials.gov. Three participants; the trial was powered for safety and not for any efficacy conclusion
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Treatment-related adverse events by CTCAE v4.0, and change from baseline in serum follistatin concentration at 3 months
✗ The study did not show it
Who was studied
NCT06411366 — injectable follistatin plasmid gene therapy in healthy subjects
How many people
43
Study design
Phase 1, open-label single dose, conducted in Honduras
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Completed 31 August 2023. No results posted to ClinicalTrials.gov as of August 2026
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Pronounced and durable increases in muscle size and strength; no abnormal changes in morphology or function of key organs on long-term transgene expression
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. No limitation is recorded for this study.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 4 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Follistatin-344
What a person takes: Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them.
The measurement behind this step
The clinical route is a vector injected directly into both quadriceps so that the muscle itself produces follistatin continuously and locally. The FS344 isoform was chosen over FS288 specifically because it lacks the heparan-sulfate-binding tail and therefore stays out of non-muscle tissue. The commercial route is a lyophilised vial reconstituted for subcutaneous injection, which corresponds to nothing in the trial literature.
Getting in
Delivered into muscle as a gene, not as a protein
A virus or a circle of DNA carrying the follistatin gene is injected straight into the thigh muscle, so the muscle makes the protein itself.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
AAV serotype 1 with a CMV promoter driving the human FS344 coding sequence, given by direct bilateral intramuscular quadriceps injection at 3 x 10^11 or 6 x 10^11 vg/kg per leg. AAV1 has strong skeletal muscle tropism and the episomal genome persists in post-mitotic myofibres, giving durable local expression. The plasmid version in the healthy-volunteer study uses non-viral DNA.
The muscle fibres read the delivered gene and start exporting the protein into the space around themselves.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Transduced myofibres transcribe FS344, translate it through the secretory pathway with signal peptide cleavage and N-glycosylation, and release mature follistatin into the extracellular space and the local circulation. Local concentration at the muscle is far higher than anything achievable by systemic dosing, which is the point of the route.
Traps myostatin and activin A before they reach their receptor
The protein wraps around the growth brake and around a second related protein, so neither can dock at the cell surface.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Two follistatin molecules encircle one myostatin or activin A dimer, occluding both the type I and type II receptor epitopes. The ligand can no longer engage ActRIIB, so SMAD2/3 phosphorylation and the downstream atrophy programme are not triggered. Neutralising activin A as well as myostatin is why follistatin produces larger effects than myostatin-selective antibodies did.
With the brake released, muscle fibres grow, fibrous scar tissue decreases and the tissue looks more normal under a microscope.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Loss of SMAD2/3 signalling relieves inhibition of the Akt-mTOR growth pathway and of satellite cell proliferation. In the treated Becker patients, biopsy showed reduced endomysial fibrosis, reduced central nucleation and a more normal fibre size distribution with hypertrophy, most marked at the higher dose; in the inclusion body myositis trial, decreased fibrosis and improved regeneration.
Some patients walked much further; a third did not move at all
The gains were large for the responders and absent for the rest, in trials of six patients with no control group.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Becker muscular dystrophy: +58, +125, +108 and +29 metres in four patients, no change in two. Sporadic inclusion body myositis: +58 to +153 metres in four, +5 to +23 metres in two, against -25.8 metres per year in matched untreated subjects (p = 0.01). Both trials were open-label, both were tiny, and the inclusion body myositis protocol included an exercise regimen for every participant.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
In trials: six patients with Becker muscular dystrophy, six with sporadic inclusion body myositis, three with Duchenne, and 43 healthy volunteers in a plasmid study in Honduras. Outside them: people injecting a lyophilised powder sold as follistatin-344.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
Where the result stopped carrying
Two of six Becker patients and two of six inclusion body myositis patients showed no meaningful change, in trials with no placebo arm
The 43-participant healthy-volunteer plasmid study completed in August 2023 and has posted no results
No follistatin product has advanced beyond phase 1 or phase 1/2 in nearly two decades since the primate data
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Still being tested
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. It is a prescription or clinician-administered medicine where it is approved.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
The identity record classes it as investigational; no register records an approval.
No source is stored against this line.
What is in the pack
The clinical route is a vector injected directly into both quadriceps so that the muscle itself produces follistatin continuously and locally. The FS344 isoform was chosen over FS288 specifically because it lacks the heparan-sulfate-binding tail and therefore stays out of non-muscle tissue. The commercial route is a lyophilised vial reconstituted for subcutaneous injection, which corresponds to nothing in the trial literature.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No register entry is recorded.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
No adverse effects were reported in the six-patient Becker cohort, and long-term transgene expression in macaques produced no abnormal changes in organ morphology or function. The safety dataset is nonetheless twenty-four patients across three registered gene therapy trials plus 43 unreported healthy volunteers. Systemic myostatin and activin A blockade has broader consequences than muscle growth — activin A has roles in reproduction, inflammation and haematopoiesis — and the local delivery route used in the trials exists partly to limit them. Nothing is known about the safety of injecting whatever is sold under this name, because no analysis of those products has been published.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear∅Nothing found in the sources checked
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Direct bilateral intramuscular injection of an AAV1 or plasmid vector in trials; lyophilised powder sold for subcutaneous injection outside them
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
The FS344 isoform was chosen over FS288 specifically because it lacks the heparan-sulfate-binding tail and therefore stays out of non-muscle tissue. The commercial route is a lyophilised vial reconstituted for subcutaneous injection, which corresponds to nothing in the trial literature.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine, investigational agent. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Follistatin-344 studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That injecting a vial sold as follistatin-344 reproduces intramuscular AAV or plasmid gene delivery of the transgene
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That a 38 kDa disulfide-rich glycoprotein can be supplied by a synthetic peptide product
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That gains in a six-minute walk test in a six-patient open-label trial with a concurrent exercise programme establish an effect size
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That results in dystrophin-deficient or inflamed muscle predict anything about healthy muscle, which the one healthy-volunteer study has not reported
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Follistatin-344 are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
Four of six inclusion body myositis patients gained 58 to 153 metres
In plain words
Six men with a progressive muscle-wasting disease received the follistatin gene into both quadriceps. Four walked substantially further at a year; two barely changed. Untreated matched patients got worse.
What was measured
Annualised change in six-minute walk distance in treated subjects against matched untreated subjects
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Mendell et al. delivered rAAV1.CMV.huFS344 at 6 x 10^11 vg/kg to the quadriceps of both legs in six subjects with sporadic inclusion body myositis, with an exercise regimen included in the protocol and the six-minute walk test as the primary outcome. Performance annualised to a median one-year change improved by +56.0 metres per year in treated subjects against a decline of -25.8 metres per year in eight untreated subjects matched for age, sex and baseline measures (p = 0.01). Four of the six treated subjects improved by 58 to 153 metres; two improved minimally, by 5 to 23 metres. Treatment effects included decreased fibrosis and improved regeneration on histology. The authors note that more advanced disease with discernible muscle loss poses challenges. The comparison group was matched, not randomised, and the trial was open-label with a concurrent exercise programme.
Written into the record, not signed off as a reviewed claim
In Becker muscular dystrophy, two of six patients showed no change at all
In plain words
The same gene therapy in six men with Becker muscular dystrophy produced walking gains of 29 to 125 metres in four of them and nothing in the other two.
What was measured
Change in six-minute walk distance per patient, with muscle histology for fibrosis, central nucleation and fibre size
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Mendell et al. delivered AAV1.CMV.FS344 by direct bilateral intramuscular quadriceps injection to six Becker muscular dystrophy patients. Cohort 1 received 3 x 10^11 vg/kg per leg: patients 01 and 02 improved by 58 and 125 metres on the six-minute walk test, and patient 03 showed no change. Cohort 2 received 6 x 10^11 vg/kg per leg: patients 05 and 06 improved by 108 and 29 metres, and patient 04 showed no improvement. No adverse effects were encountered. Histology corroborated benefit with reduced endomysial fibrosis, reduced central nucleation and a more normal fibre size distribution with muscle hypertrophy, particularly at the higher dose. The trial used the alternatively spliced FS344 specifically to avoid binding at off-target sites. Six patients, no control arm, no randomisation, and a third of them did not respond.
Written into the record, not signed off as a reviewed claim
The primate study that justified the human trials
In plain words
Injecting the follistatin gene into monkey thigh muscle produced large, lasting increases in muscle size and strength with no abnormal changes in other organs.
What was measured
Muscle size and strength after intramuscular AAV1-FS344 in cynomolgus macaques, with organ morphology and function
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Kota et al. tested an alternatively spliced form of human follistatin — chosen because it affects skeletal muscle with only minimal effects on non-muscle cells — delivered from an adeno-associated virus serotype 1 vector into the quadriceps of cynomolgus macaques. AAV1-FS344 induced pronounced and durable increases in muscle size and strength. Long-term transgene expression produced no abnormal changes in the morphology or function of key organs. This is the study that carried the programme from rodents into humans, and it is worth reading alongside the disclosure: the investigators and Nationwide Children's Hospital had filed a provisional patent on gene delivery of myostatin inhibitors and follistatin use. An erratum to the paper was published in 2026.
Written into the record, not signed off as a reviewed claim
Every human study delivered a gene, not a protein
In plain words
What is sold online is a vial of powder for injection. What has been studied in people is a virus or a plasmid carrying the follistatin gene into muscle.
What was measured
That a lyophilised vial of "follistatin-344" reproduces the results of intramuscular AAV or plasmid gene delivery of the FS344 transgene
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The complete registered human record for follistatin-344 is gene delivery: NCT01519349 (phase 1, 15 subjects, Becker muscular dystrophy and sporadic inclusion body myositis, Nationwide Children's Hospital, completed October 2017), NCT02354781 (phase 1/2, 3 subjects, Duchenne muscular dystrophy, completed November 2017, results posted), and NCT06411366 (phase 1, 43 healthy subjects, injectable follistatin plasmid gene therapy, Minicircle, Honduras, completed August 2023, no results posted). No trial has administered recombinant follistatin protein to a human being by any route. The reason is mechanical rather than regulatory: follistatin is a 38 kDa disulfide-rich glycoprotein cleared rapidly from circulation, and continuous local production from a transduced muscle is the delivery problem the whole field has been solving.
Source
ClinicalTrials.gov records NCT01519349, NCT02354781 and NCT06411366 — the complete set of registered human follistatin-344 studies, all gene delivery
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
contested
Review state
Written into the record, not signed off as a reviewed claim
What is in the vial is not a 344-residue glycoprotein
In plain words
Follistatin has 344 amino acids and dozens of disulfide bonds. Products sold as follistatin-344 peptide are priced and packaged like short synthetic peptides, which cannot be the same molecule.
What was measured
That a synthetic peptide product can deliver a 38 kDa disulfide-rich glycoprotein, an inference no analysis supports and basic protein chemistry argues against
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Follistatin-344 is a secreted glycoprotein of approximately 38 kDa with three cysteine-rich domains stabilised by an extensive disulfide network and N-linked glycosylation. Producing it correctly folded requires a mammalian or comparable eukaryotic expression system with downstream purification, and the resulting material is a biologic. Solid-phase peptide synthesis, the method behind almost every research-chemical peptide vial, does not reach that length or that folding. Analytical testing of any purchased product should therefore begin with a reducing and non-reducing gel and an intact mass, because the first question is not potency but whether the molecule is present. This page states the mismatch and does not assert what any particular vial contains, because no published chain-of-custody analysis of these products exists.
Source
UniProt P19883 — 344-residue follistatin precursor with 36 cysteines and N-glycosylation sites; the absence of any published content analysis of commercially sold follistatin-344 products
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
A plasmid version was run in 43 healthy people offshore, and never reported
In plain words
A company ran a phase 1 of an injectable follistatin plasmid gene therapy in 43 healthy volunteers in Honduras. It completed in 2023 and no results have been posted.
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
NCT06411366 is registered as a phase 1, open-label, single-dose study to evaluate the safety and efficacy of an injectable follistatin plasmid gene therapy in healthy subjects, sponsored by Minicircle, conducted in Honduras, with 43 actual participants and an actual completion date of 31 August 2023. The primary outcomes are number of participants with treatment-related adverse events by CTCAE v4.0 and change from baseline in serum follistatin concentration at three months. No results have been posted to ClinicalTrials.gov. This is the only registered human study of follistatin in people without a muscle disease, and it is the closest thing that exists to a study of the use the compound is actually sold for.
Source
ClinicalTrials.gov record NCT06411366, Minicircle, Honduras, 43 participants, completed 31 August 2023, no results posted
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
Checks this page had to pass
✓ Passed
Identity resolved
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✓ Passed
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no quarantine open
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Every public sentence names a source
The opening statement carries the origin: Written into the record, not signed off.
✗ Not passed
Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
✓ Passed
No internal keys in reader text
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✓ Passed
Safety mode resolved
The identity record classes it as investigational; no register records an approval.
✓ Passed
Canonical metadata present
slug and display name present
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What is not here
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What was measured, goal by goal — found nothing in the sources checked.
How close this is to real life — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
How this medicine reached us — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
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The older medicine-wide conclusion held in this record
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The most potent natural myostatin inhibitor, delivered by AAV gene therapy in three small open-label trials where four of six inclusion body myositis patients gained 58-153 metres on the six-minute walk and two of six Becker patients gained nothing — and sold online as an injectable protein that no trial has ever administered by that route.
Recorded evidence blocks (0)
Where it is registeredIdentifiers, relations and other names
Trade name
FS344; delivered in trials as AAV1.CMV.huFollistatin344. Sold online as "Follistatin 344" lyophilised powder
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 1 source rows
✓ no critical contamination: no quarantine open
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