Gene therapy offers the potential for durable, potentially curative treatment of neurodegenerative diseases by delivering genetic material into target cells to modify disease processes at their source. Using vectors—primarily adeno-associated viruses (AAV)—to deliver therapeutic genes, this approach can replace deficient proteins, overexpress neurotrophic factors, or silence disease-causing genes["@hudry2022"]. While still in early-stage clinical development for most neurodegenerative conditions, the technology has achieved remarkable successes in related neurological disorders, including spinal muscular atrophy and inherited retinal diseases.
Mechanism of Action
Gene therapy approaches for neurodegeneration include:
Gene Replacement
Deliver functional copies of mutated genes
Particularly relevant for monogenic forms of disease
Examples: [GBA](/proteins/gba-protein) for Gaucher disease-associated Parkinson's
Overexpression of Protective Proteins
Deliver genes encoding neurotrophic factors
Enhance cellular resilience and function
Examples: GDNF, BDNF, NRTN (Neurturin)
Gene Silencing
RNA interference (shRNA) to reduce toxic protein expression
CRISPR-based approaches for permanent editing
Examples: [Huntingtin](/genes/htt)-lowering for Huntington's disease
Genetic Reprogramming
Modulate gene expression patterns
Convert glial cells to neuronal-like cells
Enhance cellular regeneration capacity
Clinical Programs
Approved and Late-Stage Programs
Key Development Programs
Parkinson's Disease:
VY-AADC (Voyager Therapeutics): Delivers aromatic L-amino acid decarboxylase gene to convert levodopa to dopamine in the brain. Phase 1b trial showed sustained improvements in motor function and reduced levodopa requirements[@mittermeyer2012].
AAV-GBA1: Gene therapy for Parkinson's associated with [GBA](/proteins/gba-protein) mutations, delivering functional glucocerebrosidase enzyme.
Cere-120 (NTN): AAV-neurturin (NRTN) to provide trophic support to dopaminergic [neurons](/entities/neurons).
CDNF (Herantis Pharma): Cerebral Dopamine Neurotrophic Factor delivered via intraparenchymal infusion. Phase 1-2 trial (NCT01362994) completed, demonstrating safety and tolerability with no serious adverse events related to treatment. 12-month treatment period completed; patients now in 1-year follow-up study.
Alzheimer's Disease:
AAV-[BACE1](/entities/bace1): Delivering BACE1 antisense to reduce amyloid production.
AAV-APOE4: Delivering APOE2 to carriers of risk alleles.
AAV-GRN (Biogen): For frontotemporal dementia with [GRN](/proteins/grn-protein) mutations.
AAV-ARS (Sangamo): For Amyotrophic Lateral Sclerosis with SOD1 mutations.
AAV-ATXN2 (UniQure): For Spinocerebellar Ataxia type 2.
CBS/PSP Gene Therapy Programs
Corticobasal syndrome (CBS) and Progressive Supranuclear Palsy (PSP) represent Tauopathies where gene therapy approaches are being explored:
MAPT-Targeting Approaches:
AAV-antisense to MAPT: Reducing tau protein expression to address tau pathology which is central to both CBS and PSP
CRISPR-based MAPT regulation: Using CRISPRi to allele-specifically reduce mutant MAPT expression
Tau phosphorylation modulators: Gene therapy delivering kinases or phosphatases to modify tau phosphorylation state
GRN-Related Therapy:
AAV-GRN (Biogen): Progranulin replacement therapy for CBS/PSP cases with [GRN](/proteins/grn-protein) mutations. Progranulin deficiency leads to increased tau pathology, making GRN restoration a rational approach.
Neurotrophin-Based Approaches:
CDNF/CERF: Cerebral Dopamine Neurotrophic Factor may provide neuroprotection for subcortical structures affected in PSP (basal ganglia, brainstem)
AAV-BDNF: Brain-derived neurotrophic factor for protecting corticospinal tract neurons affected in CBS
Current Status:
No CBS/PSP-specific gene therapy has entered clinical trials yet
Preclinical work is focused on AAV delivery to subcortical structures and allele-specific silencing of pathogenic MAPT mutations
The close relationship between FTD (with GRN mutations) and CBS provides a translational pathway
Advantages
Potential for Long-Term Effect
Single administration may provide years of benefit
Avoids repeated invasive procedures
May reduce lifetime treatment burden
Genetic Root Targeting
Addresses underlying genetic causes
Particularly valuable for monogenic forms
May prevent disease onset in at-risk individuals
Precise Molecular Delivery
Can deliver any gene sequence
Engineered for specific expression patterns
Tissue-specific promoters enable precision
Disease Modification Potential
Unlike symptomatic treatments, may alter disease course
Potential for prevention in pre-symptomatic individuals