Fyn Kinase Modulators for Neurodegeneration

Fyn Kinase Modulators for Neurodegeneration

Overview

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Fyn Kinase Modulators for Neurodegeneration</th>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Dual Src/Abl kinase inhibitor</td>
</tr>
<tr>
<td class="label">IC50 for Fyn</td>
<td>~10 nM</td>
</tr>
<tr>
<td class="label">Clinical Status</td>
<td>Phase II completed for AD</td>
</tr>
<tr>
<td class="label">Company</td>
<td>AstraZeneca</td>
</tr>
<tr>
<td class="label">Route</td>
<td>Oral</td>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Broad Src family kinase inhibitor</td>
</tr>
<tr>
<td class="label">IC50 for Fyn</td>
<td>~50 nM</td>
</tr>
<tr>
<td class="label">Clinical Status</td>
<td>FDA-approved for CML, repurposing potential</td>
</tr>
<tr>
<td class="label">Company</td>
<td>Bristol-Myers Squibb</td>
</tr>
<tr>
<td class="label">Route</td>
<td>Oral</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Specificity</td>
</tr>
<tr>
<td class="label">PP1</td>
<td>Src family selective</td>
</tr>
<tr>
<td class="label">PP2</td>
<td>Src family selective</td>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Src/Abl inhibitor</td>
</tr>
<tr>
<td class="label">Clinical Status</td>
<td>FDA-approved for CML</td>
</tr>
<tr>
<td class="label">Brain Penetration</td>
<td>Moderate</td

Fyn Kinase Modulators for Neurodegeneration

Overview

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Fyn Kinase Modulators for Neurodegeneration</th>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Dual Src/Abl kinase inhibitor</td>
</tr>
<tr>
<td class="label">IC50 for Fyn</td>
<td>~10 nM</td>
</tr>
<tr>
<td class="label">Clinical Status</td>
<td>Phase II completed for AD</td>
</tr>
<tr>
<td class="label">Company</td>
<td>AstraZeneca</td>
</tr>
<tr>
<td class="label">Route</td>
<td>Oral</td>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Broad Src family kinase inhibitor</td>
</tr>
<tr>
<td class="label">IC50 for Fyn</td>
<td>~50 nM</td>
</tr>
<tr>
<td class="label">Clinical Status</td>
<td>FDA-approved for CML, repurposing potential</td>
</tr>
<tr>
<td class="label">Company</td>
<td>Bristol-Myers Squibb</td>
</tr>
<tr>
<td class="label">Route</td>
<td>Oral</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Specificity</td>
</tr>
<tr>
<td class="label">PP1</td>
<td>Src family selective</td>
</tr>
<tr>
<td class="label">PP2</td>
<td>Src family selective</td>
</tr>
<tr>
<td class="label">Mechanism</td>
<td>Src/Abl inhibitor</td>
</tr>
<tr>
<td class="label">Clinical Status</td>
<td>FDA-approved for CML</td>
</tr>
<tr>
<td class="label">Brain Penetration</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Strategy</td>
<td>Advantages</td>
</tr>
<tr>
<td class="label">Small molecule inhibitors</td>
<td>Oral bioavailability, BBB penetration</td>
</tr>
<tr>
<td class="label">Brain-penetrant prodrugs</td>
<td>Enhanced CNS exposure</td>
</tr>
<tr>
<td class="label">Antisense oligonucleotides</td>
<td>High selectivity</td>
</tr>
<tr>
<td class="label">Trial</td>
<td>Compound</td>
</tr>
<tr>
<td class="label">NCT02167256</td>
<td>Saracatinib</td>
</tr>
<tr>
<td class="label">—</td>
<td>Dasatinib + Quercetin</td>
</tr>
</table>

Fyn kinase (encoded by the [FYN gene](/genes/fyn)) is a member of the Src family of non-receptor tyrosine kinases (SFKs) that has emerged as a promising therapeutic target across multiple neurodegenerative diseases. Fyn connects several key pathological mechanisms including [tau](/proteins/tau) phosphorylation, [NMDA receptor](/entities/nmda-receptor) excitotoxicity, [microglial](/cell-types/microglia-neuroinflammation) activation, and [alpha-synuclein](/proteins/alpha-synuclein) phosphorylation[@kaufman2015].

The strategic importance of Fyn inhibition stems from its central position in multiple disease-relevant signaling cascades. Unlike single-target approaches, modulating Fyn activity addresses downstream effects of multiple upstream pathologies, making it an attractive cross-disease therapeutic strategy for [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), [CBS/PSP](/diseases/corticobasal-syndrome), and [ALS/FTD](/diseases/amyotrophic-lateral-sclerosis).

Fyn Biology in Neurodegeneration

Alzheimer's Disease Mechanisms

Fyn plays a critical role in AD pathogenesis through several interconnected pathways:

Parkinson's Disease Mechanisms

In PD, Fyn participates in:

CBS/PSP Mechanisms

Fyn contributes to tau propagation and spread in tauopathies:

ALS/FTD Mechanisms

Therapeutic Compounds

Saracatinib (AZD0530)

Saracatinib is the most advanced Fyn kinase inhibitor in clinical development for neurodegeneration:

Clinical Trial Results:

• Phase I showed good tolerability and brain penetration
• Phase II (NCT02167256) in mild-to-moderate AD demonstrated target engagement but no significant cognitive benefit at 12 months
• Post-hoc analyses suggested potential benefit in specific patient subgroups

Dasatinib

Dasatinib is an FDA-approved broad SFK inhibitor (originally for CML):

Considerations for Neurodegeneration:

• Limited brain penetration may restrict CNS efficacy
• Synergy with other kinase inhibitors being explored
• Combination approaches with BBB-penetrant agents under investigation

PP1 and PP2

These are research-grade selective Fyn inhibitors:

Both compounds have been used extensively in preclinical models but lack the pharmaceutical properties for clinical development.

Bosutinib

Another FDA-approved SFK inhibitor with potential for repurposing:

Therapeutic Strategies

Monotherapy Approach

Fyn kinase inhibition as a single-agent therapy addresses the downstream convergence point of multiple pathological triggers. The monotherapy approach is best suited for:

• Early-stage disease where tau and synaptic pathology are primary drivers
• Patients with biomarkers indicating Fyn pathway activation
• Prevention settings in genetically at-risk individuals

Combination Therapy

Fyn modulators may be combined with:

Delivery Strategies

Clinical Development Landscape

Ongoing and Planned Trials

Biomarkers for Target Engagement

• Phospho-tau (Tyr181) in CSF as downstream marker
• Fyn autophosphorylation in peripheral blood mononuclear cells
• PET ligands for tau pathology

Mechanism Diagram

Adverse Effects and Safety

Class Effects

• Hematological: Thrombocytopenia, neutropenia
• Gastrointestinal: Nausea, diarrhea
• Edema: Peripheral fluid retention
• Hepatic: Elevated transaminases

CNS Considerations

• Headache and dizziness reported
• Potential for increased infection risk with long-term use

Future Directions

Next-Generation Fyn Inhibitors

Combination Approaches

• Fyn inhibition + anti-amyloid immunotherapy
• Fyn inhibition + tau-targeted therapy
• Fyn inhibition + neurotrophic factor delivery

See Also

• [FYN Gene](/genes/fyn)
• [Fyn Protein](/proteins/fyn-protein)
• [Tyrosine Kinase Signaling](/mechanisms/tyrosine-kinase-signaling)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [NMDA Receptor Signaling](/mechanisms/nmda-receptor-signaling)
• [Tau Reduction Therapies](/therapeutics/tau-reduction-therapies)

References