FGL

Last Updated: August 2026

FGL (FG Loop peptide) is a synthetic 15-amino-acid peptide corresponding to the FG loop region of the second fibronectin type III module of the neural cell adhesion molecule (NCAM) — the exact site where NCAM binds the fibroblast growth factor receptor 1 (FGFR1). Developed by the laboratory of Elisabeth Bock and Vladimir Berezin at the University of Copenhagen, it reproduces a key functional motif of NCAM so that its central pharmacology can be studied without the full protein. It is not approved and is supplied for research use only.

What is FGL and how does it work?

FGL binds and activates FGFR1 — the principal receptor partner of NCAM — triggering downstream signaling that drives neurite outgrowth, presynaptic function, synapse formation, and neuronal survival; in animal work it mobilizes endogenous neural stem cells, promotes neurogenesis and remyelination, and reduces neuroinflammation.1 source NCAM is central to brain development, synaptic plasticity, and adult learning, and FGL captures that receptor-binding activity in a small peptide.

What does the research on FGL show?

Preclinical studies report that FGL enhances spatial learning and memory in rats, improves synaptic and dendritic structure in the aged hippocampus, attenuates age-related glial activation, and mobilizes neural stem cells with neuroprotective effects after experimental stroke. The mechanism (FGFR1 dependence) has been directly demonstrated. There are The one human study on record is a Phase 1 trial in healthy volunteers that tested an intranasal formulation for tolerability, safety, and pharmacokinetics — it was well tolerated but was not designed to measure efficacy.1 source There are no controlled human efficacy trials of FGL. Evidence level: Preclinical (in vitro and rodent) efficacy; one Phase 1 human safety/PK study (intranasal), no efficacy trials.

What are the safety and regulatory considerations?

FGL is not approved for human use. The only human safety data is a single Phase 1 tolerability/pharmacokinetics study of an intranasal formulation in healthy volunteers (well tolerated, with minor transient nasal effects); beyond that limited setting — and for the injectable research-grade material sold today — its safety is not established.1 source; as an FGFR-activating peptide, growth-factor-pathway effects warrant caution. See the legal status guide.

Why does vendor verification matter, and how does Peptigrity verify?

As a synthetic 15-mer research peptide, FGL is subject to synthesis impurities and mislabeling, so HPLC purity and mass-spec identity are the objective checks. Peptigrity collects independent third-party Certificates of Analysis for FGL from shops' official channels and verifies each for authenticity before publishing. Because shops choose which COAs to publish, results reflect the batches shops have made public rather than every production batch — a selection bias we state openly. A community-funded Testing Grant to purchase and test vials anonymously is in development. Tests in the database come from independent labs such as Janoshik Analytical, Freedom Diagnostics, and Chromate. See how to read lab results.

Educational information only; not medical advice. FGL is not approved for human use. Consult a qualified healthcare provider. Peptigrity does not sell, endorse, or recommend products or vendors.