FGL
Also known as: Fibroblast Growth Loop, NCAM-derived peptide, Neural cell adhesion molecule peptide
Overview
FGL is a 15-amino acid peptide synthesized from the interconnecting loop region of the second fibronectin type III module in the extracellular domain of the neural cell adhesion molecule (NCAM). It mimics NCAM-fibroblast growth factor receptor 1 (FGFR1) interactions, driving neurotrophic, neuroprotective, and anti-inflammatory effects. Phase I clinical trials have demonstrated safety and acceptable pharmacokinetics after intranasal administration, and it is in clinical development for neurodegenerative diseases.
Mechanism of Action
FGL directly binds NCAM and activates FGFR1 through NCAM-mediated signaling, stimulating downstream cascades governing neuronal survival, cell adhesion, and synaptic stability. This promotes: enhanced long-term potentiation (LTP) in hippocampus and dentate gyrus; neurite outgrowth and axonal regeneration; synaptic plasticity and spinogenesis (aged rat study: significant changes in spine and synapse ultrastructure); and anti-inflammatory effects mediated by increased IL-4 secretion from glial cells, reducing microglia activation and IL-1β production.
Potential Benefits
- Enhanced LTP in hippocampus and dentate gyrus
- Improved spatial and working memory in aged models
- Significant ultrastructural changes in synapses and dendritic spines in aged rats
- Neuroprotection against amyloid-beta and stress-induced damage
- Anti-inflammatory effects via IL-4/CD200 pathway
- Phase I safety established with intranasal delivery
- Potential for Alzheimer's disease, stroke, and TBI applications
Dosage Protocols
The following reflects doses used in published research studies. This is not medical advice. Consult a qualified healthcare professional.
| Beginner | Research-only — human dosing not established |
| Intermediate | N/A |
| Advanced | N/A |
| Cycle Duration | 2-8 weeks in preclinical studies |
FG Loop peptide — NCAM mimetic. Preclinical only. Human protocols not established.
Use our Reconstitution Calculator to determine exact syringe units for your protocol.
Routes of Administration
Subcutaneous Injection Moderate
Used in preclinical rodent studies.
Intranasal Better CNS delivery
Preferred route for CNS-targeted NCAM mimetic effects.
Read our full Routes of Administration Guide for detailed comparison of all delivery methods.
Stacking Protocols
Popular research stacks involving FGL:
Experimental Neuroplasticity Stack
Research-only combination targeting NCAM-FGFR signaling plus broader neurotrophic support.
Explore our complete Peptide Stacking Guide for more combinations and safety considerations.
Reconstitution
| Storage | Refrigerate at 2-8°C after reconstitution. Do not freeze reconstituted solution. |
|---|
Typical vial sizes: 1-5 mg. Add bac water slowly down the side of the vial, swirl gently — do not shake. Use insulin syringe for precise dosing.
Need exact syringe measurements?
Amino Acid Sequence
Thr-Val-Ser-Lys-Glu-Lys-Glu-Lys-Lys-Glu-Gln-Lys-Lys-Val-Ala (15 amino acids from NCAM FNIII-2 loop)
Side Effects & Safety
- Well-tolerated in Phase I
- Preclinical seizure threshold concern noted in epilepsy models at high doses
- Intranasal delivery with good brain penetration reduces systemic risks
Safety & Contraindications
This information is for educational purposes only. Consult a qualified healthcare provider before using any peptide.
Pregnancy / Lactation
Bleeding Disorders
Active Skin Infection at Injection Site
Pharmacokinetics
| Half-Life | Not well characterized for this peptide; consult primary literature |
|---|---|
| Storage | Store lyophilized peptide at -20°C (long-term) or 2-8°C (short-term, under 30 days). Reconstituted: refrigerate at 2-8°C and use within 28-30 days. Protect from light. Do not freeze reconstituted solution. |
Synergistic Compounds
The following compounds have been studied alongside FGL for potential complementary or synergistic effects:
Learn More
References & Further Reading
Latest News & Research
View all articles →
FDA Staff Reviewers Say ‘No’ to 7 Compounded Peptides Ahead of July PCAC Vote
FDA staff reviewers urged against adding seven popular peptides to the 503A bulks list ahead of the July PCAC meeting, citing weak human data and safety uncertainty.
FDA reviewers urge ‘no’ on BPC-157, TB-500, MOTS-c ahead of July 2026 compounding vote
FDA reviewers’ June 29 briefings recommend against listing seven popular peptides for 503A compounding, citing limited human data and immunogenicity risk.
Medicare Starts Paying for Obesity Drugs Today — Bridge Program Opens $50 Access for Millions
Medicare's new $50 Bridge program covering Wegovy, Zepbound, Foundayo, and oral Wegovy for obesity launched July 1 — the first Medicare weight-loss benefit.
FDA staff urges caution on compounded peptides ahead of July advisory meeting
Ahead of the July 23–24 Pharmacy Compounding Advisory Committee meeting, FDA staff briefings recommend against listing seven popular peptides for compounding.