Antisense and Gene Therapies
This category includes therapies designed to directly target the genetic root of disease, rather than downstream pathways or symptoms. The most established approach is antisense oligonucleotides (ASOs), but the category also includes RNA interference (RNAi), gene replacement, and emerging gene-editing strategies.
In the neurodegeneration landscape, this represents one of the clearest shifts toward precision, disease-modifying treatment. Instead of asking which pathways are broken, these therapies ask: can we directly reduce or correct the toxic gene product?
Clinically, this approach is already in use in certain neurological diseases (for example, spinal muscular atrophy) and is now being actively translated into neurodegenerative conditions such as ALS and Huntington’s disease.
Biological Rationale
The rationale is unusually direct compared to most other therapies. Many neurodegenerative diseases are driven, at least in part, by toxic gain-of-function proteins (mutant SOD1, mutant huntingtin, C9orf72 repeat products).
ASOs are short synthetic strands of nucleic acids that bind to specific RNA sequences. Once bound, they can promote degradation of the target RNA, alter splicing, reduce production of the toxic protein. This allows selective reduction of disease-driving proteins upstream of downstream damage like aggregation, mitochondrial dysfunction, or inflammation.
In contrast to broad pathway modulation, gene-targeted therapies aim to intervene at the source of toxicity.
Evidence Strength
Emerging to Strong
This category has some of the strongest proof-of-concept data in neurology. In ALS, SOD1-targeted ASO therapy (tofersen) has shown clear target engagement and biological effects. In Huntington’s disease, HTT-lowering approaches have demonstrated the ability to reduce huntingtin levels in humans. There remain many new approaches still in preclinical stages as well.
However, clinical outcomes have been mixed so far. Some trials have shown biomarker improvement without clear functional benefit, especially in symptomatic patients.
Limitations
Delivery is challenging. Many of these therapies require intrathecal administration (direct injection into cerebrospinal fluid), which is invasive and must be repeated. Timing also matters. By the time symptoms appear, significant neuronal loss has already occurred. Lowering a toxic protein may slow progression but not reverse damage, which complicates clinical trial outcomes.
Not all diseases are equally targetable. This approach works best for conditions with a clear, dominant toxic gene product. It is less straightforward in complex, multifactorial diseases like sporadic Alzheimer’s or Parkinson’s.
Finally, long-term safety remains an active area of study, especially when partially reducing proteins that also have normal functions.
Sources
- Bennett, C. F., Krainer, A. R., & Cleveland, D. W. (2019). Antisense Oligonucleotide Therapies for Neurodegenerative Diseases.
- Tabrizi, S. J., Leavitt, B. R., Landwehrmeyer, G. B., et al. (2019). Targeting Huntingtin Expression in Patients with Huntington’s Disease.
- Miller, T. M., Cudkowicz, M. E., Genge, A., et al. (2022). Trial of Antisense Oligonucleotide Tofersen for SOD1 ALS.
- Schoch, K. M., & Miller, T. M. (2017). Antisense Oligonucleotides: Translation from Mouse Models to Human Neurodegenerative Diseases.
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