Investigational / not FDA-approved

FST 344

Follistatin FS344 coding isoform — FS344 ≠ FS288 ≠ FS315; AAV gene therapy ≠ black-market protein.

Editorial review:

What evidence says

Evidence snapshot

This drawer marks papers. It is not a plan, a dose, or a source. A paper is a bounded report. It is not a protocol. Grades name the object. They are not a safety rating.

Identity lock — isoform-careful. Follistatin (gene FST; UniProt P19883) is an activin/myostatin-binding glycoprotein. The human precursor is commonly described as 344 amino acids (FS344 / FST344 coding frame). Mature circulating and heparin-binding species arise by processing and alternative splicing — principally FS315 (circulating) and FS288 (higher heparan-sulfate affinity). “FST 344” in black-market and analytics papers names recombinant material corresponding to the FS344 coding isoform — not automatically FS288 or FS315 as graded objects, and not ACE-083 / ACE-031 (engineered local follistatin-Fc / ActRIIB-Fc programs). Gene-therapy papers (Mendell line) deliver an AAV-follistatin (FS344) construct — a regulated investigational gene-therapy object, not a vial of recombinant protein. PubChem has no clean small-molecule CID for this protein → do not invent one. Refuse physique / sports-performance glow for unlabeled recombinant FST344. This drawer marks papers. It is not use advice.

Bottom line

Three tracks must stay apart: (1) isoform biochemistry (FS288 vs FS315 binding/distribution); (2) AAV-FS344 gene-therapy clinical series in Becker muscular dystrophy and sporadic inclusion-body myositis; (3) black-market FST344 detection / case-report risk literature. Gene-therapy functional signals do not grade gray-market recombinant “FST 344” vials. Controlled human physique or sports-performance efficacy for unlabeled FST344 protein is not established.

Papers

Isoform identity / biochemistry

PMID 3380788 — Shimasaki 1988

Tested: primary structure of the human follistatin precursor and genomic organization (foundation for 344-aa precursor framing).

Does not show: a modern recombinant FST344 sports product, or gene-therapy approval.

PMID 8340384 — Sugino 1993

Tested: molecular heterogeneity of follistatin — carboxyl-terminal truncated forms show higher heparan-sulfate proteoglycan affinity (FS288-class vs longer forms).

Does not show: that FS344 vials equal FS288 biology.

PMID 15472207 — Schneyer 2004

Tested: differential distribution of follistatin isoforms using an FS315-specific immunoassay in human samples.

Does not show: gray-market FST344 product identity or purity.

PMID 16627583 — Sidis 2006

Tested: biological activity of follistatin isoforms and follistatin-like-3 as a function of cell-surface binding and ligand specificity (activin, myostatin, GDF11).

Does not show: human gene-therapy or physique outcomes.

PMID 19644449 — Cash 2009

Tested: crystal structure of myostatin:follistatin-288 complex — receptor-utilization and heparin-binding insights.

Does not show: FS344 vial efficacy; FS288 structural object ≠ automatic FST344 grade.

AAV-FS344 gene therapy (investigational clinical)

PMID 20368179 — Kota 2009

Tested: follistatin gene delivery enhancing muscle growth and strength in nonhuman primates (preclinical bridge to human gene-therapy programs).

Does not show: human approval or recombinant-protein vial equivalence.

PMID 25322757 — Mendell 2015

Tested: Phase 1/2a follistatin gene-therapy trial in Becker muscular dystrophy (AAV1-FS344 framing; safety/functional exploratory endpoints).

Does not show: that unlabeled recombinant FST344 protein equals the gene-therapy object, or a sports indication.

PMID 27858738 — Al-Zaidy 2015

Tested: follow-on ambulation/functional report in the Becker follistatin gene-therapy context.

Does not show: a pivotal Phase 3 win for recombinant FST344 vials.

PMID 28279643 — Mendell 2017

Tested: follistatin gene therapy in sporadic inclusion-body myositis — functional outcome report.

Does not show: approval for IBM or transfer of results to black-market protein.

Black-market / unregulated FST344 (analytics & risk context)

PMID 31758732 — Reichel 2019

Tested: analytical detection of black-market follistatin 344 preparations.

Does not show: clinical efficacy or pharmaceutical-grade identity.

PMID 33460286 — Reichel 2020

Tested: further detection/characterization of black-market follistatin 344.

Does not show: safety or efficacy establishing medical or performance use.

PMID 32671599 — Dağ 2020

Tested: retrospective case series associating high-dose follistatin-344 exposure framing with central serous chorioretinopathy.

Does not show: causal proof by itself; still a risk-signal context paper, not an efficacy grade.

What is not established

That black-market “FST 344” equals AAV-FS344 gene-therapy trial material. That FS344, FS315, and FS288 are interchangeable grading objects. Human physique or athletic-performance efficacy for recombinant FST344 protein. Equivalence to ACE-083 / ActRIIB ligand-trap programs or to anti-myostatin antibodies. Product identity and purity for unregulated preparations. This drawer does not provide use advice, schedules, or sourcing.

Selected sources

3380788 8340384 15472207 16627583 19644449 20368179 25322757 27858738 28279643 31758732 33460286 32671599

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