Growth ⏱ Half-life: Relatively short, but downstream effects on muscle signaling persist for days. Phase 1

Follistatin-344

Follistatin 344

Updated March 15, 2026

Evidence at a Glance

Regulatory statusPhase 1
AAV1.CMV.FS344 gene therapy reached Phase 1/2a for muscular dystrophy (~18 patients); not approved; the injectable recombinant protein is a separate, untested modality
Human evidenceLimited
Animal evidenceModerate

Follistatin gene therapy (FS344) showed early safety and modest walking gains in small Phase 1/2a muscular-dystrophy trials, but injecting recombinant FS344 protein for muscle building has no human efficacy or safety data.

What the research does not support

  • It is not FDA-approved; the human data are from AAV gene therapy in small muscular-dystrophy trials, not from injecting the peptide.
  • Injecting recombinant FS344 protein for bodybuilding has no human efficacy or safety trials.
  • Follistatin is not a myostatin-only inhibitor — it also neutralizes activins and other TGF-beta family proteins, so its effects are not muscle-specific.
  • Reports of dramatic muscle growth are extrapolated from gene therapy and animals, not proven for the injectable form.
Half-Life
Relatively short, but downstream effects on muscle signaling persist for days.
Mol. Weight
~37,000 g/mol (glycoprotein)

What is Follistatin-344?

Follistatin-344 is a naturally occurring glycoprotein that acts as a powerful antagonist of myostatin — the body’s primary muscle growth limiter. By binding and neutralizing myostatin, follistatin removes the molecular brake on skeletal muscle development.

Research Applications

Myostatin inhibition, muscle hypertrophy research, muscular dystrophy models, and body composition studies.

Dosage Information (Research Use)

Research protocols: 100-300 mcg/day subcutaneously for 10-30 day cycles. Research use only.

Reconstitution & Handling

Reconstitute carefully with BAC water — larger protein requires gentle handling. Do not shake.

Half-Life & Pharmacokinetics

Relatively short, but downstream effects on muscle signaling persist for days.

Reported Observations in Literature

Limited human data. Theoretical concerns about effects on reproductive hormones (activin is involved in FSH regulation).

Key Research References

  • Haidet AM, et al. “Long-term enhancement of skeletal muscle mass and strength by single gene administration of myostatin inhibitors.” Proc Natl Acad Sci. 2008

How Follistatin-344 Works

Follistatin-344 binds and neutralizes myostatin, activin, and other TGF-β superfamily members that limit muscle growth. By removing these growth-inhibitory signals, follistatin permits enhanced muscle hypertrophy and satellite cell proliferation.

Research Findings

Animal models show dramatic muscle mass increases with follistatin overexpression or administration. Gene therapy approaches using follistatin have entered early clinical trials for muscular dystrophies.

Dosage & Administration

Research protocols: 100-300 mcg/day subcutaneously for 10-30 day cycles. Research use only.

Safety & Side Effects

Limited human data. Theoretical concerns about effects on reproductive hormones (activin is involved in FSH regulation).

Important: All safety information is derived from published research, primarily animal studies. No controlled human clinical trial data exists unless explicitly noted. This compound is sold for research purposes only.

Quick Facts

Sequence 344-amino acid glycoprotein
Molecular Weight ~37,000 g/mol (glycoprotein)
Half-Life Relatively short, but downstream effects on muscle signaling persist for days.
Available Sizes 1mg
Storage Lyophilized: -20°C. Reconstituted: 2-8°C, use within 14 days.

Key Research References

  • Haidet AM, et al. "Long-term enhancement of skeletal muscle mass and strength by single gene administration of myostatin inhibitors." Proc Natl Acad Sci. 2008

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