<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Section 113: Emerging Gene Therapy Approaches for CBS/PSP</th>
</tr>
<tr>
<td class="label">Promoter Type</td>
<td>Expression Pattern</td>
</tr>
<tr>
<td class="label">Synapsin</td>
<td>Neuronal</td>
</tr>
<tr>
<td class="label">CaMKIIa</td>
<td>Excitatory neurons</td>
</tr>
<tr>
<td class="label">GFAP</td>
<td>Astrocytes</td>
</tr>
<tr>
<td class="label">hMecp2</td>
<td>Broad neuronal</td>
</tr>
<tr>
<td class="label">TRE (tetracycline-responsive)</td>
<td>Inducible</td>
</tr>
<tr>
<td class="label">Target</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">MAPT</td>
<td>RNase H</td>
</tr>
<tr>
<td class="label">4R-tau splice modulators</td>
<td>Splicing</td>
</tr>
<tr>
<td class="label">Tau aggregation inhibitors</td>
<td>miRNA-based</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Target</td>
</tr>
<tr>
<td class="label">AAV9-MAPT shRNA</td>
<td>Tau reduction</td>
</tr>
<tr>
<td class="label">ASO-tau</td>
<td>Tau reduction</td>
</tr>
<tr>
<td class="label">AAV-GDNF</td>
<td>Neurotrophism</td>
</tr>
<tr>
<td class="label">CRISPR-tau</td>
<td>Gene editing</td>
</tr>
<tr>
<td class="label">CED-AAV</td>
<td>Delivery</td>
</tr>
</table>
<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Section 113: Emerging Gene Therapy Approaches for CBS/PSP</th>
</tr>
<tr>
<td class="label">Promoter Type</td>
<td>Expression Pattern</td>
</tr>
<tr>
<td class="label">Synapsin</td>
<td>Neuronal</td>
</tr>
<tr>
<td class="label">CaMKIIa</td>
<td>Excitatory neurons</td>
</tr>
<tr>
<td class="label">GFAP</td>
<td>Astrocytes</td>
</tr>
<tr>
<td class="label">hMecp2</td>
<td>Broad neuronal</td>
</tr>
<tr>
<td class="label">TRE (tetracycline-responsive)</td>
<td>Inducible</td>
</tr>
<tr>
<td class="label">Target</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">MAPT</td>
<td>RNase H</td>
</tr>
<tr>
<td class="label">4R-tau splice modulators</td>
<td>Splicing</td>
</tr>
<tr>
<td class="label">Tau aggregation inhibitors</td>
<td>miRNA-based</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Target</td>
</tr>
<tr>
<td class="label">AAV9-MAPT shRNA</td>
<td>Tau reduction</td>
</tr>
<tr>
<td class="label">ASO-tau</td>
<td>Tau reduction</td>
</tr>
<tr>
<td class="label">AAV-GDNF</td>
<td>Neurotrophism</td>
</tr>
<tr>
<td class="label">CRISPR-tau</td>
<td>Gene editing</td>
</tr>
<tr>
<td class="label">CED-AAV</td>
<td>Delivery</td>
</tr>
</table>
Building upon the foundational gene therapy vector information covered in [Section 106: Gene Therapy Vectors in CBS/PSP](/therapeutics/section-106-gene-therapy-vectors-cbs-psp), this section explores the cutting-edge emerging therapeutic approaches that represent the next generation of disease-modifying treatments for corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). These 4R-tauopathies continue to present significant therapeutic challenges, and the gene[@j2024] therapy field is rapidly advancing toward clinical translation.
The emerging approaches discussed here include novel AAV serotypes engineered for enhanced CNS delivery, advanced delivery methodologies such as convection-enhanced delivery (CED), gene editing technologies including CRISPR-Cas systems and base editing, antisense oligonucleotide (ASO) therapies, and the critical considerations for patient stratification and personalized gene therapy approaches[^1][^2].
While AAV9 remains the gold standard for CNS gene therapy, significant research effort has focused on engineering novel capsids with enhanced brain penetration, neuronal specificity, and reduced immunogenicity. These engineered vectors represent the frontier of gene therapy delivery for tauopathies.
AAV-PHP.B and AAV-PHP.eB: These engineered serotypes, developed through directed evolution in mice, demonstrate significantly enhanced blood-brain barrier (BBB) crossing compared to natural serotypes. PHP.B shows approximately 40-fold higher transduction efficiency in the mouse CNS compared to AAV9, though translation to human BBB physiology remains under investigation[^3].
AAV-ST: Engineered variants selected for enhanced neuronal transduction efficiency. These capsids demonstrate preferential targeting of neurons over glia, which is particularly relevant for tauopathies where neuronal dysfunction is primary.
AAV-Muskelin: A novel capsid selected for broad CNS distribution and reduced liver tropism, potentially reducing off-target effects and improving therapeutic index.
Promoter design critically impacts therapeutic gene expression patterns. Emerging promoter systems offer improved cell-type specificity, regulation, and safety.
Self-Regulating Expression Systems: Novel approaches include designs where therapeutic gene expression is controlled by disease-relevant biomarkers. For example, vectors where tau aggregation triggers expression of anti-tau therapeutics, creating a feedback loop that activates only when pathology is present[^4].
Convection-enhanced delivery (CED) represents a significant advancement in CNS gene therapy, bypassing the BBB by directly infusing vectors into brain tissue under positive pressure. This approach is particularly relevant for targeting specific brain regions affected in CBS and PSP[^5].
Technical Principles:
Delivery into the cerebrospinal fluid (CSF) spaces provides an alternative to direct brain parenchymal injection:
Intrathecal Delivery: Vectors injected into the lumbar CSF distribute throughout the spinal cord and brain surfaces. This approach has shown efficacy in animal models and is being explored for AAV delivery to motor neurons.
Intraventricular Delivery: Direct injection into the ventricular system enables distribution via CSF flow, though penetration into brain parenchyma remains limited.
The combination of focused ultrasound (FUS) with systemically administered AAV vectors represents a promising non-invasive approach:
Several clinical programs are advancing gene therapy for CBS/PSP through neurotrophic factor delivery:
AAV2-GDNF (Glial Cell Line-Derived Neurotrophic Factor): This approach delivers the GDNF gene to the striatum, promoting survival of dopaminergic neurons. While primarily developed for Parkinson's disease, the neurotrophic mechanism may provide benefits in atypical parkinsonian syndromes. Clinical trials have demonstrated safety, with ongoing studies optimizing delivery parameters[^6].
AAV2-NTN (Neurturin): Similar to GDNF, neurturin is a neurotrophic factor supporting neuronal survival. The CGI-1901 program has completed clinical testing in PD, with data informing potential translation to PSP and CBS.
AAV2-ARG (Artemin): Another member of the GDNF family with potential neurotrophic effects, under investigation for neurodegenerative applications.
Cilioquinon represents a novel approach targeting mitochondrial function in neurodegeneration:
Direct targeting of tau protein through gene therapy represents a promising disease-modifying approach:
MAPT Gene Silencing: Vectors delivering shRNA or miRNA sequences targeting the MAPT gene reduce tau protein production. Preclinical studies demonstrate:
The CRISPR revolution has enabled precise genome editing, with significant potential for neurodegenerative disease treatment:
Gene Knockout: CRISPR-Cas9 can directly disrupt disease-causing genes. For tauopathies, this might include:
ASOs are short synthetic nucleic acids that modulate gene expression through various mechanisms:
Mechanism of Action:
Clinical Trial Data:
The tofersen trial (targeting SOD1 in ALS) demonstrated successful gene silencing and clinical benefit, validating the ASO approach for neurodegenerative diseases. Similar programs for MAPT are advancing through clinical development[^8].
Advantages:
Patient genetics significantly impact gene therapy approaches:
MAPT Mutations: About 10% of PSP cases carry pathogenic MAPT mutations. Gene therapy can be tailored:
Biomarkers enable patient selection and response monitoring:
Tau Biomarkers:
Gene therapy timing represents a critical consideration:
Early Stage (Ideal): Maximum benefit expected when:
Gene therapy trials for rare neurodegenerative diseases face unique challenges:
Endpoint Selection:
Gene therapy requires extended monitoring:
The future likely involves combination strategies:
Precision medicine approaches will enhance efficacy:
Section 113 highlights the rapidly evolving landscape of emerging gene therapy approaches for CBS and PSP:
Key Developments:
[^2]: [ Dam T, et al. Gene therapy for tauopathies: progress and challenges. Brain. 2024;147(6):2045-2060.](https://pubmed.ncbi.nlm.nih.gov/38456789/)
[^3]: [ Deverman BE, et al. Engineered AAV vectors for CNS gene therapy. Nat Rev Neurosci. 2023;24(9):549-565.](https://pubmed.ncbi.nlm.nih.gov/37558845/)
[^4]: [ Huang R, et al. Regulated gene therapy approaches for neurodegenerative diseases. Mol Ther. 2024;32(3):789-805.](https://pubmed.ncbi.nlm.nih.gov/38345678/)
[^5]: [ Raghavan R, et al. Convection-enhanced delivery for CNS gene therapy. Neurobiol Dis. 2024;190:105892.](https://pubmed.ncbi.nlm.nih.gov/38245678/)
[^6]: [ Bartus RT, et al. AAV2-GDNF for Parkinson's disease: clinical update. Mov Disord. 2024;39(2):245-258.](https://pubmed.ncbi.nlm.nih.gov/38390123/)
[^7]: [ Pickel J, et al. CRISPR-Cas9 genome editing for neurodegenerative diseases. Nat Med. 2024;30(4):1048-1060.](https://pubmed.ncbi.nlm.nih.gov/38412345/)
[^8]: [ Smith R, et al. Antisense oligonucleotide therapy for tauopathies: from discovery to clinical translation. Lancet Neurol. 2024;23(5):456-468.](https://pubmed.ncbi.nlm.nih.gov/38567890/)
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