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Supplement Monograph

FGL(L)

PeptideNootropic

FGL (FGLL) is a synthetic NCAM-derived research peptide studied in animals for memory and neuroprotection; an early human safety study exists, but it is not an approved drug or supplement.

Work in progress Updated July 2026

What Is FGL?

FGL (also FGLL, the “FG loop” peptide) is a synthetic peptide derived from the neural cell adhesion molecule (NCAM), designed to mimic NCAM’s interaction with the fibroblast growth factor receptor (FGFR). Through FGFR activation it is reported to promote neurite outgrowth, synaptic plasticity, and neuronal survival, and it has been studied as a candidate for memory enhancement and neuroprotection in neurodegenerative and injury models. It was carried into early clinical development (by ENKAM Pharmaceuticals and academic collaborators) but that program does not appear to have advanced to approval. It is a research compound, not an approved medicine or dietary supplement.

Evidence

Most FGL evidence is preclinical (rodent/cell-based), with one notable early human study. In animals, a synthetic NCAM-derived FGL peptide protected hippocampal neurons from ischaemic injury both in vitro and in vivo 1Reference 1Skibo GG et al. · 2005In vitroA synthetic NCAM-derived peptide, FGL, protects hippocampal neurons from ischemic insult both in vitro and in vivo — in vivo/in vitro studyView study →, and improved impaired spatial learning and memory in a rat neurodevelopmental model 2Reference 2Secher T et al. · 2009AnimalEffect of an NCAM mimetic peptide FGL on impairment in spatial learning and memory after neonatal phencyclidine treatment in rats — rat studyView study → — findings consistent with a neurotrophic, memory-supporting mechanism. Uniquely among the research peptides in this section, FGL(L) also has a published Phase 1 human study: an 8-day open-label ascending-dose trial in 24 healthy male volunteers found intranasal FGLL well tolerated across the doses tested, with no notable abnormalities in ECG, vital signs, or laboratory tests 3Reference 3Anand R et al. · 2007Tolerability, safety and pharmacokinetics of the FGLL peptide following intranasal administration in healthy volunteers — Phase 1 studyView study →. That is a safety/tolerability result only — it does not demonstrate a cognitive or clinical benefit in humans, and no efficacy trial establishing memory improvement in people was found in this pass.

Dosage & Safety

There is no established therapeutic human dose for FGL. The Phase 1 study used single intranasal doses of 25, 100, and 200 mg for tolerability assessment 3Reference 3Anand R et al. · 2007Tolerability, safety and pharmacokinetics of the FGLL peptide following intranasal administration in healthy volunteers — Phase 1 studyView study →, but that is not a treatment regimen and this page makes no dosing recommendation. FGL is not FDA-approved and is not an approved dietary supplement. While the early human study reported good short-term tolerability, efficacy, repeat-dose and long-term safety, drug interactions, and pregnancy/lactation safety are not established and were not assessed in this pass. This entry is informational only and is not an endorsement of use.

References

  1. Skibo GG, Lushnikova IV, Voronin KY, et al. (2005). A synthetic NCAM-derived peptide, FGL, protects hippocampal neurons from ischemic insult both in vitro and in vivo — in vivo/in vitro study. Eur J Neurosci. https://pubmed.ncbi.nlm.nih.gov/16197499/
  2. Secher T, Novitskaia V, Berezin V, et al. (2009). Effect of an NCAM mimetic peptide FGL on impairment in spatial learning and memory after neonatal phencyclidine treatment in rats — rat study. Behav Brain Res. https://pubmed.ncbi.nlm.nih.gov/19133297/
  3. Anand R, Seiberling M, Kamtchoua T, Pokorny R. (2007). Tolerability, safety and pharmacokinetics of the FGLL peptide following intranasal administration in healthy volunteers — Phase 1 study. Clin Pharmacokinet. https://pubmed.ncbi.nlm.nih.gov/17375985/