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Section 107: CRISPR-Based Therapies in CBS/PSP
Section 107: CRISPR-Based Therapies in CBS/PSP
Introduction
<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Section 107: CRISPR-Based Therapies in CBS/PSP</th>
</tr>
<tr>
<td class="label">Component</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Guide RNA (gRNA)</td>
<td>Directs Cas9 to specific genomic sequence</td>
</tr>
<tr>
<td class="label">Cas9 protein</td>
<td>Creates double-strand break</td>
</tr>
<tr>
<td class="label">Repair template</td>
<td>Provides corrected sequence</td>
</tr>
<tr>
<td class="label">Editor Type</td>
<td>Editing Capability</td>
</tr>
<tr>
<td class="label">Cytosine Base Editor (CBE)</td>
<td>C→T conversion</td>
</tr>
<tr>
<td class="label">Adenine Base Editor (ABE)</td>
<td>A→G conversion</td>
</tr>
<tr>
<td class="label">Glycosylase Base Editors</td>
<td>Extended scope</td>
</tr>
<tr>
<td class="label">Mutation</td>
<td>Effect</td>
</tr>
<tr>
<td class="label">P301L</td>
<td>Increased tau aggregation</td>
</tr>
<tr>
<td class="label">P301S</td>
<td>Enhanced fibril formation</td>
</tr>
<tr>
<td class="label">K257T</td>
<td>Altered splicing</td>
</tr>
<tr>
<td class="label">G389R</td>
<td>CBD-like phenotype</td>
</tr>
<tr>
<td class="label">Variant</td>
<td>Effect</td>
</tr>
<tr>
<td class="label">N370S</td>
<td>Reduced enzyme activity</td>
</tr>
<tr>
<td class="label">L444P</td>
<td>Severe deficiency
Section 107: CRISPR-Based Therapies in CBS/PSP
Introduction
<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Section 107: CRISPR-Based Therapies in CBS/PSP</th>
</tr>
<tr>
<td class="label">Component</td>
<td>Function</td>
</tr>
<tr>
<td class="label">Guide RNA (gRNA)</td>
<td>Directs Cas9 to specific genomic sequence</td>
</tr>
<tr>
<td class="label">Cas9 protein</td>
<td>Creates double-strand break</td>
</tr>
<tr>
<td class="label">Repair template</td>
<td>Provides corrected sequence</td>
</tr>
<tr>
<td class="label">Editor Type</td>
<td>Editing Capability</td>
</tr>
<tr>
<td class="label">Cytosine Base Editor (CBE)</td>
<td>C→T conversion</td>
</tr>
<tr>
<td class="label">Adenine Base Editor (ABE)</td>
<td>A→G conversion</td>
</tr>
<tr>
<td class="label">Glycosylase Base Editors</td>
<td>Extended scope</td>
</tr>
<tr>
<td class="label">Mutation</td>
<td>Effect</td>
</tr>
<tr>
<td class="label">P301L</td>
<td>Increased tau aggregation</td>
</tr>
<tr>
<td class="label">P301S</td>
<td>Enhanced fibril formation</td>
</tr>
<tr>
<td class="label">K257T</td>
<td>Altered splicing</td>
</tr>
<tr>
<td class="label">G389R</td>
<td>CBD-like phenotype</td>
</tr>
<tr>
<td class="label">Variant</td>
<td>Effect</td>
</tr>
<tr>
<td class="label">N370S</td>
<td>Reduced enzyme activity</td>
</tr>
<tr>
<td class="label">L444P</td>
<td>Severe deficiency</td>
</tr>
<tr>
<td class="label">E326K</td>
<td>Altered protein</td>
</tr>
<tr>
<td class="label">Null variants</td>
<td>Complete loss</td>
</tr>
<tr>
<td class="label">Mutation</td>
<td>Effect</td>
</tr>
<tr>
<td class="label">Null mutations</td>
<td>Complete loss of function</td>
</tr>
<tr>
<td class="label">Splice mutations</td>
<td>Reduced levels</td>
</tr>
<tr>
<td class="label">Missense variants</td>
<td>Reduced activity</td>
</tr>
<tr>
<td class="label">Serotype</td>
<td>CNS Tropism</td>
</tr>
<tr>
<td class="label">AAV9</td>
<td>Neurons + glia</td>
</tr>
<tr>
<td class="label">AAV-PHP.B</td>
<td>Enhanced CNS</td>
</tr>
<tr>
<td class="label">AAV-PHP.eB</td>
<td>Superior CNS</td>
</tr>
<tr>
<td class="label">AAV2</td>
<td>Neurons</td>
</tr>
<tr>
<td class="label">Feature</td>
<td>AAV</td>
</tr>
<tr>
<td class="label">Cargo Capacity</td>
<td>~4.7 kb</td>
</tr>
<tr>
<td class="label">Repeat Dosing</td>
<td>Limited</td>
</tr>
<tr>
<td class="label">Immunogenicity</td>
<td>Low-moderate</td>
</tr>
<tr>
<td class="label">Manufacturing</td>
<td>Complex</td>
</tr>
<tr>
<td class="label">Method</td>
<td>Duration</td>
</tr>
<tr>
<td class="label">AAV</td>
<td>Years</td>
</tr>
<tr>
<td class="label">LNP</td>
<td>Weeks-months</td>
</tr>
<tr>
<td class="label">Exosomes</td>
<td>Variable</td>
</tr>
<tr>
<td class="label">Viral (other)</td>
<td>Variable</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">CRISPRi</td>
<td>transcriptional repression</td>
</tr>
<tr>
<td class="label">CRISPR knockout</td>
<td>NHEJ gene disruption</td>
</tr>
<tr>
<td class="label">Base editing</td>
<td>Splice site disruption</td>
</tr>
<tr>
<td class="label">Model System</td>
<td>Application</td>
</tr>
<tr>
<td class="label">iPSC neurons</td>
<td>Patient-specific</td>
</tr>
<tr>
<td class="label">Mouse models</td>
<td>In vivo delivery</td>
</tr>
<tr>
<td class="label">Non-human primates</td>
<td>Safety/toxicology</td>
</tr>
<tr>
<td class="label">Trial</td>
<td>Technology</td>
</tr>
<tr>
<td class="label">Various</td>
<td>Base editing</td>
</tr>
<tr>
<td class="label">NTLA-2001</td>
<td>CRISPR-Cas9</td>
</tr>
<tr>
<td class="label">Various</td>
<td>Gene therapy</td>
</tr>
<tr>
<td class="label">Combination</td>
<td>Rationale</td>
</tr>
<tr>
<td class="label">CRISPR + Tau antibodies</td>
<td>Gene edit + protein clearance</td>
</tr>
<tr>
<td class="label">CRISPR + Neurotrophins</td>
<td>Target neurons + support survival</td>
</tr>
<tr>
<td class="label">CRISPR + Autophagy enhancers</td>
<td>Reduce protein + enhance clearance</td>
</tr>
<tr>
<td class="label">Variant</td>
<td>Size</td>
</tr>
<tr>
<td class="label">SaCas9</td>
<td>3.2 kb</td>
</tr>
<tr>
<td class="label">Cas9-XTEN</td>
<td>3.4 kb</td>
</tr>
<tr>
<td class="label">Cas9-Mini</td>
<td>2.9 kb</td>
</tr>
<tr>
<td class="label">Cas13</td>
<td>3.8 kb</td>
</tr>
<tr>
<td class="label">Biomarker</td>
<td>Method</td>
</tr>
<tr>
<td class="label">Tau PET</td>
<td>Imaging</td>
</tr>
<tr>
<td class="label">Neurofilament light</td>
<td>Blood/CSF</td>
</tr>
<tr>
<td class="label">Genetic correction</td>
<td>Sequencing</td>
</tr>
<tr>
<td class="label">Motor assessments</td>
<td>Clinical</td>
</tr>
</table>
CRISPR-Cas gene editing technologies represent one of the most promising therapeutic approaches for genetically mediated forms of corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). These 4R-tauopathies involve progressive tau protein aggregation, and several genetic factors have been identified that influence disease risk and progression[@doudna2014]. This section provides comprehensive coverage of CRISPR-based therapeutic strategies under development for CBS/PSP, including target genes, delivery methods, editing technologies, and current research status.
The ability to directly modify disease-causing genetic variants offers the potential for disease modification rather than merely symptomatic treatment. While clinical application remains years away for most CNS applications, the rapid advancement of gene editing technologies provides hope for patients with genetic forms of atypical parkinsonism[@kantor2024].
CRISPR Gene Editing Technologies
Overview of CRISPR-Cas Systems
Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) combined with Cas (CRISPR-associated) proteins enable precise DNA targeting and modification. The system evolved as a bacterial adaptive immune mechanism and has been harnessed for genome engineering[@hsu2024].
CRISPR-Cas9
The original and most widely used CRISPR system employs Cas9 endonuclease to create double-strand breaks at targeted genomic locations[@ran2025]:
Advantages:
- Well-characterized system
- Extensive clinical experience
- Multiple delivery platforms available
- Double-strand breaks can cause unintended edits
- Requires cellular repair mechanisms for corrections
- Large size of Cas9 (~4.2 kb) limits AAV cargo
Base Editing
Base editing allows precise single-nucleotide changes without double-strand breaks, offering improved safety[@gaudelli2024]:
Advantages for CBS/PSP:
- No double-strand breaks reduce off-target effects
- Precise single-nucleotide changes
- Lower immunogenicity than Cas9
- Can target specific disease-causing mutations
- Correcting MAPT mutations (P301L, P301S)
- Modifying GBA risk variants
- Creating protective APOE variants
Prime Editing
Prime editing uses Cas9 fused to reverse transcriptase for precise insertions, deletions, and substitutions without double-strand breaks[@anzalone2019]:
Advantages:
- All 12 types of edits possible
- No double-strand breaks required
- Greater precision than standard CRISPR
- Can correct multiple mutation types
- Larger construct size (~5.0 kb)
- Lower efficiency than base editing
- Delivery challenges for CNS
Target Genes for CBS/PSP
MAPT (Microtubule-Associated Protein Tau)
The MAPT gene encodes the tau protein, which forms the characteristic neurofibrillary tangles in CBS/PSP. Several disease-causing mutations have been identified[@guo2024]:
Editing Approaches:
GBA (Glucocerebrosidase)
GBA variants significantly increase risk for CBS/PSP and other synucleinopathies. Heterozygous carriers have 5-10x increased risk[@riboldi2023]:
Editing Approaches:
GRN (Progranulin)
GRN mutations cause frontotemporal dementia and may modify CBS/PSP risk and progression[@miller2023]:
Editing Approaches:
Other Target Genes
Delivery Methods for CNS
AAV Vectors
Adeno-associated viruses (AAVs) are the leading delivery platform for CNS gene therapy[@mendell2023]:
Challenges:
- Small cargo capacity (~4.7 kb) limits CRISPR component packaging
- Pre-existing immunity common in human populations
- Requires precise targeting to affected brain regions
- Split-intein systems: Divide Cas9 into two AAVs
- MiniCas9 variants: Smaller nuclease versions
- Self-complementary AAVs: Enhanced expression
Lipid Nanoparticles (LNPs)
LNPs offer an alternative to viral vectors with distinct advantages[@kojima2024]:
Advantages:
- Larger cargo capacity can accommodate prime editors
- No pre-existing immunity issues
- Repeat dosing possible
- mRNA delivery established for COVID vaccines
- CNS delivery being actively optimized
- BBB-crossing modifications in development
- Exosome hybrid systems emerging
Exosome-Based Delivery
Exosomes offer promising natural carrier properties[@alabi2024]:
- Endogenous vesicles: Natural cellular delivery vehicles
- BBB penetration: Demonstrated in preclinical models
- Targing capability: Can be engineered for specific neurons
- Safety profile: Lower immunogenicity than synthetic vectors
Comparison of Delivery Methods
Therapeutic Strategies
Allele-Specific Editing
Allele-specific targeting allows selective editing of mutant alleles while preserving wild-type function[@liu2024]:
Requirements:
- Mutation creates unique PAM or protospacer
- Clear distinction between alleles
- Patient-specific guide design
- Spares normal gene function
- Reduced haploinsufficiency risk
- Personalized approach
- Only applicable to specific mutations
- Requires detailed genetic testing
- Limited to heterozygous mutations
Knockdown Strategies
Reducing expression of disease genes can mitigate toxic protein accumulation[@qi2023]:
Considerations:
- Must avoid complete gene loss
- Haploinsufficiency concerns
- May require precise timing
Gene Correction vs. Gene Modulation
Gene Correction:
- Permanent fix of genetic defect
- Applicable to familial cases
- Technically challenging
- Adjusts expression levels
- Broader applicability
- May require ongoing treatment
Clinical Research Status
Preclinical Progress
Significant advances have been made in preclinical models[@sinnamon2024]:
Milestones Achieved:
- Successful base editing in human neurons
- AAV-mediated CNS delivery demonstrated
- Proof-of-concept in tauopathy models
Clinical Trials
Current clinical trial landscape for gene editing in neurodegeneration[@gillmore2024]:
Timeline for CBS/PSP:
- Early preclinical: 2-3 years
- IND-enabling studies: 3-5 years
- Clinical trials: 5-10 years
Challenges Remaining
Integration with CBS/PSP Treatment Plan
Relationship to Other Sections
This section connects to multiple areas of the CBS/PSP treatment plan:
- Section 103: Neurotrophic Factor Therapies — gene therapy combination approaches
- Section 102: Proteostasis Network — addressing protein aggregation at source
- Genetic Architecture: Understanding which patients may benefit (Section on genetic architecture)
- BBB Delivery Strategies: Critical for successful CNS delivery
Combination Approaches
CRISPR-based therapies may provide greatest benefit when combined[@song2023]:
Patient Counseling Points
When discussing CRISPR therapies with patients:
Ethical Considerations
Somatic vs. Germline Editing
Somatic Editing (Currently Preferred):
- Only patient's own cells affected
- Changes not inherited by offspring
- Lower ethical concern
- Already in clinical trials
- Affects embryos and future generations
- Permanent heritable changes
- Technical and ethical concerns
- Not clinically appropriate currently
Informed Consent Requirements
For research participation:
- Understanding long-term uncertainties
- Risk of unintended off-target edits
- Possibility of no direct clinical benefit
- Alternative treatment options
- Data sharing implications
Access and Equity Concerns
- High development costs may limit accessibility
- Need for diverse population representation in trials
- Development priorities should address rare disease needs
Emerging Technologies
Engineered Cas Variants
Novel Delivery Platforms
Next-Generation Editing
- CRISPR-Cas12: Alternative nucleases with distinct properties
- CRISPR-Cas13: RNA targeting without DNA modification
- Epigenetic editors: Modify gene expression without sequence change
- Prime editing 2.0: Enhanced efficiency and specificity
Research Directions and Future Outlook
Biomarkers for Treatment Response
Regulatory Considerations
- FDA has established gene therapy guidance
- Accelerated approval pathways being developed
- Real-world evidence integration underway
- International harmonization ongoing
Predicted Development Pathway
Conclusion
CRISPR-based therapies represent a transformative approach for treating CBS/PSP, offering the potential to directly modify disease-causing genetic factors. While significant technical challenges remain, particularly regarding CNS delivery, the rapid advancement of gene editing technologies provides genuine hope for patients with genetic forms of atypical parkinsonism.
The most immediate clinical applications are likely to involve AAV-delivered CRISPR components targeting well-characterized mutations in MAPT, GBA, and GRN. Base editing technologies offer particular promise due to their precision and safety profile. Combination approaches that pair gene editing with protein-clearing therapeutics may provide the most comprehensive disease modification.
Patients and families should be encouraged to pursue genetic testing to identify potential candidates for future gene editing therapies, while understanding that clinical application for CBS/PSP likely remains 5-10 years away. In the meantime, ongoing research participation and engagement with clinical trials will be essential for advancing these promising technologies.
See Also
- [CRISPR Gene Correction Approaches for CBS/PSP](/technologies/crispr-gene-editing)
- [Section 103: Neurotrophic Factor Therapies in CBS/PSP](/therapeutics/section-103-neurotrophic-factor-therapies-cbs-psp)
- [Section 102: Proteostasis Network in CBS/PSP](/therapeutics/section-102-proteostasis-network-cbs-psp)
- [Gene Therapy for Neurodegeneration](/therapeutics/gene-therapy-neurodegeneration)
- [MAPT Gene](/genes/mapt)
- [GBA Gene](/genes/gba)
- [GRN Gene](/genes/grn)
- [Blood-Brain Barrier Therapeutic Strategies](/investment/bbb-penetration-technologies)
- [Personalized ASO Therapy for CBS/PSP](/therapeutics/aso-therapy-cbs-psp)
References
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| slug | therapeutics-section-107-crispr-therapies-cbs-psp |
| kg_node_id | None |
| entity_type | therapeutic |
| origin_type | v1_polymorphic_backfill |
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