Fyn Kinase Modulators for Neurodegeneration

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Fyn Kinase Modulators for Neurodegeneration

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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:

Tau Phosphorylation: Fyn phosphorylates tau at tyrosine residues (Tyr18, Tyr29), promoting pathological aggregation and spread[@nygaard2018]. This connects amyloid-beta signaling to downstream tau pathology.

NMDA Receptor Dysregulation: Fyn phosphorylates NR2A and NR2B subunits, leading to altered receptor trafficking and function. Hyperactive Fyn signaling contributes to excitotoxic cell death through excessive NMDA receptor activation.

Amyloid-beta Signaling: Aβ oligomers activate Fyn, creating a pathogenic feedback loop where amyloid pathology drives toxic downstream signaling through Fyn-dependent pathways.

Synaptic Dysfunction: Fyn-dependent phosphorylation of PSD-95 and other postsynaptic density proteins contributes to synaptic loss and cognitive decline.

Parkinson's Disease Mechanisms

In PD, Fyn participates in:

Alpha-synuclein Phosphorylation: Fyn phosphorylates α-synuclein at Tyr125, Tyr133, and Tyr136, potentially accelerating aggregation and toxicity[@fyn_alpha_syn].

Dopaminergic Neuron Survival: Fyn regulates dopamine receptor signaling and neurotrophic factor responses in dopaminergic neurons.

Neuroinflammation: Fyn mediates microglial activation and inflammatory cytokine production in response to pathological α-synuclein.

CBS/PSP Mechanisms

Fyn contributes to tau propagation and spread in tauopathies:

Tau Tyrosine Phosphorylation: Fyn-mediated tau phosphorylation at tyrosine residues facilitates misfolding and propagation of pathological tau species.

Synaptic Vulnerability: Fyn signaling at synapses may accelerate tau-induced synaptic dysfunction.

ALS/FTD Mechanisms

TDP-43 Pathology: Fyn may interact with TDP-43 aggregation pathways in ALS/FTD.

Synaptic Excitotoxicity: Similar to AD, Fyn-mediated NMDA receptor dysregulation contributes to excitotoxic cell death.

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:

Anti-amyloid agents (lecanemab, donanemab): Address upstream Aβ pathology while blocking downstream Fyn-dependent toxicity

Anti-tau agents: Synergistic effect on tau pathology through complementary mechanisms

Neurotrophic factors: Fyn inhibition combined with BDNF or similar agents for enhanced neuroprotection

Anti-inflammatory agents: Target microglial activation through both Fyn-dependent and independent pathways

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

Mermaid diagram (expand to render)

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

Brain-penetrant analogs: Developing compounds with enhanced BBB penetration

Selectivity optimization: Reducing off-target kinase effects

Allosteric modulators: Targeting regulatory domains for more selective inhibition

Combination Approaches

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

References

[Kaufman AC, et al., FYN kinase inhibition reduces Aβ toxicity in Alzheimer's disease (2015)](https://pubmed.ncbi.nlm.nih.gov/25988847/)

[Nygaard HB, et al., Targeting FYN kinase in Alzheimer's disease (2018)](https://pubmed.ncbi.nlm.nih.gov/29330423/)

[Forman MS, et al., The Src family kinase inhibitor saracatinib (AZD0530) in Alzheimer's disease (2014)](https://pubmed.ncbi.nlm.nih.gov/24920652/)

[Zhou X, et al., FYN in dopaminergic neuron survival and alpha-synuclein phosphorylation (2016)](https://pubmed.ncbi.nlm.nih.gov/27013231/)

[Tang JC, et al., Fyn kinase as a therapeutic target in neurodegenerative diseases (2019)](https://pubmed.ncbi.nlm.nih.gov/31794128/)

[Dutta K, et al., Protein tyrosine kinase Fyn in Alzheimer's disease (2016)](https://pubmed.ncbi.nlm.nih.gov/26868432/)

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📗 Cite This Artifact

Fyn Kinase Modulators for Neurodegeneration

Fyn Kinase Modulators for Neurodegeneration

Overview

Fyn Kinase Modulators for Neurodegeneration

Overview

Fyn Biology in Neurodegeneration

Alzheimer's Disease Mechanisms

Parkinson's Disease Mechanisms

CBS/PSP Mechanisms

ALS/FTD Mechanisms

Therapeutic Compounds

Saracatinib (AZD0530)

Dasatinib

PP1 and PP2

Bosutinib

Therapeutic Strategies

Monotherapy Approach

Combination Therapy

Delivery Strategies

Clinical Development Landscape

Ongoing and Planned Trials

Biomarkers for Target Engagement

Mechanism Diagram

Adverse Effects and Safety

Class Effects

CNS Considerations

Future Directions

Next-Generation Fyn Inhibitors

Combination Approaches

See Also

References

💬 Discussion