FGL (FG loop peptide)
FGL (FG loop peptide) is a bioactive peptide derived from the neural cell adhesion molecule (NCAM). It corresponds to the FG loop of the second fibronectin type III module of NCAM, and is studied for its effects on synaptic plasticity and neuronal survival through cell adhesion molecule interactions.
This peptide has been studied in preclinical models for effects on long-term potentiation, amyloid-beta-induced neuronal damage, and cognitive performance. It has not been studied in humans. FGL exhibits unique stability characteristics and maintains bioactivity across various physiological conditions, making it distinctive among neuroprotective peptides.
Overview
FGL demonstrates specific binding affinity for NCAM receptors and associated co-receptors, contributing to its unique neuroprotective profile. The peptide is metabolized primarily in the liver with partial renal elimination, and shows excellent CNS penetration with sustained bioavailability up to 24 hours post-administration using specialized detection methods.
Chemical structure & Properties
- Molecular Formula: C71H116N20O25
- Molecular Weight: ~1,649.8 Da
- Sequence: EVYVVAENQQGKSKA, 15 amino acids
- Half-life: 4-6 hours following subcutaneous administration
- Stability: Enhanced resistance to proteolytic degradation
Mechanism of Action
FGL exerts its therapeutic effects through multiple interconnected molecular pathways:
Areas Investigated in
the Research Literature
Current Clinical Evidence
Safety Profile and Considerations
Regulatory Status and Legal Considerations
Regulatory information current as of 28 August 2026. This is a summary, not legal or medical advice, and status can change.
FDA Status
- Classification: Research peptide, not approved for therapeutic use
- Approval Status: Not approved for human therapeutic use
- Development Stage: Preclinical development with limited human data
- Regulatory Position: Phase I human studies needed for safety determination
WADA Status
- Classification: Potentially prohibited under cognitive enhancement regulations
- Athletic Use: Status unclear for competitive sports
- Testing: Limited detection methods available
Legal Availability
- Commercial Status: Not legally available as prescription medication
- Market Presence: Available as "research chemicals" through specialized providers
- Quality Control: Variable quality and purity from different suppliers
- Clinical Use: Limited to research settings and experimental protocols
Conclusion
What the evidence supports
FGL is a peptide derived from the neural cell adhesion molecule (NCAM) that has been studied only in animal and cell-culture models, where effects on long-term potentiation, protection against amyloid-beta toxicity and cognitive performance have been reported. It has not been studied in humans; there is no human efficacy or safety data and no established dosing. FGL is not FDA approved for any therapeutic use and remains a preclinical research compound. This page summarizes the published research and nothing further.
FGL SCIENTIFIC
DATA SUMMARY
About this library
This library is published for education. It summarizes published research on compounds studied in this field. Many have no approved medical use, and several cannot lawfully be compounded in the United States. The presence of a page here does not mean Paragon offers that compound. Nothing on these pages is an offer to treat.
This page is general education about a compound studied in this field. Nothing here is medical advice, a recommendation, or an offer to prescribe or supply. A page appearing in this library does not mean Paragon Sports Medicine offers that compound.
Disclaimer: This information is provided for educational purposes only and does not constitute medical advice. FGL is not approved by the FDA for human therapeutic use. Patients should consult with qualified healthcare providers before considering any peptide therapy.
Statements on this page have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Many peptides described here are not FDA approved for the uses discussed, and some cannot lawfully be compounded in the United States. Nothing on this page is medical advice or a recommendation for any individual. Whether any therapy is appropriate depends on your history, your laboratory results, and a clinical evaluation. Individual results vary. This page is published for education. Use of this site does not create a physician-patient relationship.