Overview
Following subcutaneous or intramuscular administration, FST 344 distributes systemically due to reduced heparan sulfate proteoglycan binding relative to FST 288. Its interaction with activin A also modulates hypothalamic-pituitary FSH secretion, which may have downstream effects on gonadal hormone axes — particularly relevant in female subjects. Hepatic clearance and renal filtration govern elimination; glycosylation status influences half-life. At the tissue level, blunted Smad2/3 signaling upregulates MyoD, myogenin, and IGF-1 local expression, amplifying hypertrophic response.
Proposed mechanism
FST 344 binds with high affinity to myostatin (GDF-8) and activin A/B, sequestering these TGF-β superfamily ligands and preventing them from engaging their cognate receptors (ActRIIA/ActRIIB). This disinhibits downstream anabolic signaling through the Smad2/3 pathway, shifting the balance toward muscle protein synthesis and satellite cell activation. Simultaneously, FST 344 can modulate FSH signaling in the pituitary axis due to its activin-antagonist properties.
What the evidence supports
Most data comes from preclinical animal studies. Human clinical trial evidence is limited or absent.
Graded Animal
Evidence drawn from in vivo animal models or in vitro systems. Mechanistically informative; translation to humans is unproven.
Key citations
Representative primary sources, including results that did not favour the compound.
- [1]
Follistatin gene therapy for Becker muscular dystrophy: a non-randomized controlled trial
· Molecular Therapy · 2015
- [2]
Inactivation of myostatin does not result in hyper-muscularity in dystrophin-deficient mdx mice
· Journal of Clinical Investigation · 2006
- [3]
Systemic delivery of follistatin 288 promotes muscle hypertrophy and reduces fat accumulation in mice
· Endocrinology · 2008
- [4]
Follistatin isoforms and their roles in muscle and reproductive biology
· Molecular and Cellular Endocrinology · 2011
Citation records in this build are illustrative placeholders for the design.
Reference information for research purposes. Not medical advice, and not a recommendation to use any compound. Many entries describe substances that are not approved for human use.