Recovery · Investigational
FGL Peptide
No lawful US pathway
01 · Overview
FGL (FG loop) peptide is a synthetic 15-amino acid peptide corresponding to the binding site of the neural cell adhesion molecule (NCAM) for fibroblast growth factor receptor 1 (FGFR1) (PMID 15115815). By binding and activating FGFR, it mimics NCAM signaling without requiring cell-cell adhesion (PMID 16197499).
The peptide has been investigated for neuroprotective and cognitive-enhancing properties in models of neurological injury and disease.
02 · Research summary & key findings
In rats, FGL given after training produced a long-lasting improvement of memory and promoted synapse formation in cultured hippocampal neurons (PMID 15115815), facilitated hippocampal long-term potentiation in vivo (PMID 21508096), and rescued spatial memory in aged, socially isolated rats (PMID 30928883). It also protected hippocampal neurons from ischemic injury in cell culture and in a gerbil model (PMID 16197499). In the only published human study, single intranasal doses of FGL(L) were well tolerated in 24 healthy men, with transient nasal burning as the main side effect (PMID 17375985); no efficacy trials in patients have been published.
03 · Regulatory status
FGL Peptide is in the investigational stage. While preclinical and early-phase data exist, it has not received regulatory approval for clinical use in the United States.
No lawful pathway today
FGL Peptide is not FDA-approved and does not currently have a lawful prescription or compounding pathway in the United States, so we do not sell it and will not book a consultation for it. That can change: in 2026 FDA began reviewing several peptides for compounding. If you are working on the goal it is studied for, a licensed clinician can tell you what is lawfully available, which may be something else.
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Looking for a lawful, clinician-prescribed option for injury recovery and tissue repair?
FGL Peptide is an investigational compound, is not FDA-approved, and has no lawful US compounding pathway, so we do not offer it and no clinician we work with will prescribe it. Products sold online as “research chemicals” are not made or tested to the standards required of medicines. If you are working on injury recovery and tissue repair, a licensed clinician can tell you at a free consultation whether an FDA-approved or lawfully compounded treatment fits you, or whether nothing does.
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04 · Administration routes
- Subcutaneous injection
- Intranasal
References
- [1]A synthetic neural cell adhesion molecule mimetic peptide promotes synaptogenesis, enhances presynaptic function, and facilitates memory consolidation J Neurosci, 2004. PMID 15115815
- [2]A synthetic NCAM-derived peptide, FGL, protects hippocampal neurons from ischemic insult both in vitro and in vivo Eur J Neurosci, 2005. PMID 16197499
- [3]Tolerability, safety and pharmacokinetics of the FGLL peptide, a novel mimetic of neural cell adhesion molecule, following intranasal administration in healthy volunteers Clin Pharmacokinet, 2007. PMID 17375985
- [4]The neural cell adhesion molecule-derived peptide FGL facilitates long-term plasticity in the dentate gyrus in vivo Learn Mem, 2011. PMID 21508096
- [5]Systemic administration of a fibroblast growth factor receptor 1 agonist rescues the cognitive deficit in aged socially isolated rats Neurobiol Aging, 2019. PMID 30928883
Primary literature
- PubMed: "FGL Peptide"
Peer-reviewed literature indexed by the National Library of Medicine.
- ClinicalTrials.gov: "FGL Peptide"
Registered interventional and observational studies, including status and phase.
- PubChem: "FGL Peptide"
Chemical structure, molecular properties, and bioactivity data.
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Disclaimer: This information is provided for educational and research purposes only. It is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any peptide therapy. The Peptide Association does not endorse or recommend any specific treatment protocol. See our editorial policy for how this content is produced and reviewed. Clinicians: join the network.