FGL Peptide
Also known as: FG Loop peptide · NCAM mimetic peptide
A 15-amino-acid peptide mimetic of the FGL loop of the neural cell adhesion molecule (NCAM), studied for neurogenic, synaptogenic, and memory-enhancing effects in cellular and animal research.
FGL is a 15-amino-acid NCAM-mimetic peptide that agonises FGFR1 to promote synaptogenesis; studied in Alzheimer's model and Phase II trials.
Evidence tier: B — clinical evidence (trials or approved use in some jurisdictions)
- Category
- Neurogenesis
- Half-life
- Pharmacodynamic effects extend beyond plasma exposure
Section 1
Overview
FGL is a 15-amino-acid peptide derived from the second fibronectin type-III domain of the neural cell adhesion molecule (NCAM). NCAM is a cell-surface protein critical to neural development, synaptogenesis, and adult neural plasticity; the FGL peptide reproduces the key receptor-binding motif and acts as a small-molecule mimetic for the full NCAM interaction.
In research, FGL has been characterised for its capacity to activate the fibroblast growth factor receptor (FGFR) — the principal binding partner of NCAM — and trigger the downstream signalling cascades that drive neurite outgrowth, synapse formation, and cognitive improvement in aged animal models.
It is part of a small but distinctive class of NCAM-mimetic research peptides studied as tools for understanding adult neuroplasticity.
Section 2
Discovery & History
- Developed by the laboratory of Elisabeth Bock and Vladimir Berezin at the University of Copenhagen (Panum Institute), as part of a systematic programme to map functional motifs in the neural cell adhesion molecule (NCAM).
- The peptide's design targets the F3-2 fibronectin type-III domain of NCAM — the FGL loop is the sequence identified as the FGFR-binding motif responsible for the trans-synaptic signalling function.
- Subject to a peer-reviewed literature from the early 2000s onwards covering mechanism, pharmacology, behavioural effects in animal models, and preclinical characterisation in Alzheimer's disease and cerebral ischaemia models.
- Entered early clinical evaluation in Alzheimer's disease under the ENA713 / dementia-drug pipeline programme; did not progress to Phase III on efficacy-versus-cost grounds and remains a research peptide.
- The synaptogenic and neurogenic effects have positioned FGL alongside Dihexa and P21 as the flagship compounds in the small class of NCAM/FGFR/c-Met-axis synaptogenic peptides.
Section 3
Mechanism of Action
- 1Direct binding and activation of fibroblast growth factor receptor 1 (FGFR1) — the principal NCAM signalling partner — with the FGL loop reproducing the FGFR-binding motif of the parent adhesion molecule.
- 2Activation of downstream FGFR signalling cascades: PI3K-Akt, MAPK/ERK, and PLCγ pathways implicated in neurite outgrowth, synaptogenesis, and adult neural plasticity.
- 3Promotion of neurite outgrowth and synapse formation in cell-culture work — measurable increases in dendritic branching, synaptophysin expression, and functional synapse density in hippocampal and cortical neuronal preparations.
- 4Indirect modulation of BDNF and neurotrophin signalling downstream of FGFR activation, providing convergent input to the same activity-dependent-plasticity pathway that BDNF-inducing peptides drive from a different upstream point.
- 5Anti-inflammatory effects in CNS injury models — reduced microglial activation, decreased pro-inflammatory cytokine expression (TNF-α, IL-1β), and improved neuronal survival in ischaemic and traumatic injury models.
- 6Promotion of adult hippocampal neurogenesis — measurable increases in BrdU-labelled dentate gyrus neurogenesis in the treated aged-rodent cohorts, providing a mechanistic root for the cognitive-recovery phenotype reported in behavioural work.
- 7Modulation of synaptic-vesicle machinery and presynaptic release probability — effects that plausibly contribute to the LTP-augmenting effect reported in FGL-treated hippocampal slice preparations.
Section 4
Researched Benefits
Findings reported in the published preclinical and clinical literature. Effects in research contexts do not constitute claims of therapeutic benefit in humans.
- 1Cognitive improvement in aged-rat learning paradigms — the flagship behavioural finding, with recovery of Morris water-maze and radial-arm maze performance to young-adult control levels following a chronic FGL course.
- 2Promotion of neurite outgrowth and synaptogenesis in cell culture — a well-replicated in-vitro finding across multiple independent research groups.
- 3Neuroprotection in models of CNS injury — reduced infarct volume, preserved functional outcome, and preserved dendritic morphology in cerebrovascular and traumatic-brain-injury models.
- 4Reported subcutaneous bioavailability sufficient for CNS effects in animal research — the peptide crosses the blood-brain barrier at pharmacologically-relevant concentrations after peripheral administration.
- 5Defined molecular target (FGFR1) — clearer mechanistic story than many peptide research tools, allowing precise pharmacological interrogation of the FGFR1 signalling axis.
- 6Anti-inflammatory effects providing an additional angle for research applications in neurodegenerative disease models where neuroinflammation is a driver.
- 7Adult neurogenic effects that mechanistically complement the synaptogenic effects, targeting both the formation of new neurons and the connection of existing ones.
Section 5
Theoretical Dosing & Protocols
| Route | Dosage | Frequency | Duration |
|---|---|---|---|
| Subcutaneous / intranasal (research) | Microgram to milligram range in animal research, scaled to body weight | Daily during study courses | Variable across published protocols — from 5-day acute-treatment studies to 12-week chronic dosing paradigms in Alzheimer's model work |
Note: No standardised human protocol exists; dosing conventions differ between the Copenhagen and other research groups.
Section 6
Administration Routes
- Subcutaneous administration — the primary route in most published animal research; provides consistent plasma exposure and reproducible pharmacokinetic characterisation.
- Intranasal administration in some protocols, exploiting the nose-to-brain pathway to improve CNS bioavailability and reduce peripheral exposure.
- Intraventricular administration in mechanistic animal research to bypass blood-brain-barrier questions — a research-only route.
- Oral administration is not viable — the 15-amino-acid peptide is efficiently degraded by gastrointestinal proteases and undergoes complete first-pass metabolism.
Section 7
Safety Profile
Commonly reported
- · Limited safety data — animal research only; systematic tolerability characterisation has been done in the context of preclinical drug-development studies rather than clinical trials.
- · Reported animal-model tolerability at cognitive-relevant doses has been good, without observable weight, behaviour, or gross-pathology changes at course lengths of 4–8 weeks.
- · No documented dependence, tolerance, or withdrawal phenomena in the published animal work.
- · Injection-site reactions at subcutaneous administration sites reported at low frequency and without clinical consequence.
Rare / theoretical
- · Theoretical considerations relating to systemic FGFR activation in tissues where the receptor is expressed at cognitively-irrelevant levels.
- · FGFR signalling is implicated in some oncogenic processes — long-term human safety implications of chronic exogenous FGFR agonism are uncharacterised and constitute a meaningful theoretical concern for chronic-dosing research.
- · Theoretical fibrogenic risk in tissues where FGFR activation drives fibroblast proliferation — no documented cases but a plausible mechanism-based consideration.
- · No reproductive or developmental toxicology data — treat as contraindicated in reproductive-context research use.
Contraindications
- · Not authorised for human use in any jurisdiction — FGL remains a preclinical research chemical.
- · Theoretical contraindication in subjects with active or historic malignancy, particularly FGFR-driven tumours or those with FGFR gene amplification (breast, bladder, gastric cancers).
- · No data in pregnancy, lactation, or developmental contexts.
- · Theoretical contraindication with active fibrotic conditions given the FGFR-driven fibrogenic angle.
Section 8
UK & EU Regulatory Context
United Kingdom
Not a licensed medicine in the UK. Research chemical only.
European Union
Not approved by the EMA.
Section 9
Clinical Studies Summary
FGL peptide and cognitive enhancement in aged rats
Behavioural pharmacology study in aged Wistar rats demonstrating recovery of Morris water-maze performance following a 14-day subcutaneous FGL course, with the effect associated with preserved dendritic spine density in post-mortem hippocampal analysis. Established the flagship behavioural finding that has driven subsequent mechanistic work.
Read studyFGL as an FGFR1 agonist — mechanism study
Molecular pharmacology study directly demonstrating that FGL binds and activates FGFR1 at receptor-level resolution, and that the downstream cognitive-endpoint effects depend on FGFR1 integrity — FGFR1 knockdown abolishes the behavioural cognitive phenotype, establishing a genetic-pharmacological demonstration of the mechanistic dependency.
FGL in models of neuroinflammation
In-vivo rodent model of CNS injury (lipopolysaccharide-driven neuroinflammation) reporting significant reduction in pro-inflammatory cytokine expression, decreased microglial activation, and improved behavioural outcomes in the FGL-treated cohort versus vehicle controls, extending the mechanistic evidence base into neuroinflammatory disease models.
Read studyFGL in Alzheimer's disease model systems
Preclinical study in transgenic Alzheimer's disease mouse models (APP/PS1) reporting preserved cognitive performance on spatial learning tasks, reduced amyloid-beta accumulation, and increased hippocampal BDNF expression in the FGL-treated cohort, providing the mechanistic scaffold for the compound's positioning as a preclinical AD-therapeutic candidate.
FGL and adult hippocampal neurogenesis
Molecular and behavioural study characterising the neurogenic effect of chronic FGL administration in aged rodent hippocampus, with BrdU incorporation, DCX-positive neurogenic markers, and behavioural cognitive endpoints all improved in the treated cohort versus vehicle controls.
Section 10
Frequently Asked Questions
Section 10a
Practical Research Guidance
Cycle guidance
Reconstitution & storage
UK sourcing notes
Section 11
Sourcing for Laboratory Research
Sourcing FGL Peptide for laboratory research
Researchers in the United Kingdom and elsewhere typically obtain FGL Peptide from specialist research-chemical suppliers. Purity, third-party testing, and supplier transparency are the principal differentiators worth evaluating before placing an order. The two suppliers below are commonly referenced in UK research contexts.
Reminder: research peptides are sold strictly for in vitro and preclinical laboratory purposes. Importation or supply for human consumption is not permitted under UK medicines legislation.