L13 Gene Therapy for Neurodegenerative Diseases Flashcards
What are ATMPs?
Advanced Therapy Medicinal Products.
These are highly specialised treatments based on cell and gene therapy. You can target specific mutations in a patient and develop therapies for that specific mutation.
What is the aim of gene therapy and what does it involve?
- The aim is to modify genetic material of living things for therapeutic purposes.
- This involves the insertion of a functional gene or another molecule that contains an information sequence into a cell to achieve a therapeutic effect.
How is insertion of genetic material done?
- Non-viral vectors (plasmids, nanoparticles, ribosomes).
- Viral vectors (lentiviral vectors, adeno-associated vectors (AAVs), adenoviruses). These are mainly used in the spinal cord.
What are lentiviral vectors?
These are a type of retrovirus and can be split into two groups:
1) Primate-based lentiviruses (HIV).
2) Non-primate derived-lentiviruses.
Who were the first patients to receive lentiviral vector treatment?
PD patients.
The glia and neurons were both infected - the vectors integrated genes into the chromosome of the target cells and expressed continuously after one dose.
What is three-plasmid co-transfection?
This is where you transfect plasmids into HEK cells and once transfected, a virus is made and released into the media.
This virus can then be concentrated and used in research applications or clinical trials.
What is the biggest issue with gene therapy?
Insertional mutagenesis. This is where mutations are induced in the DNA. In some studies this has shown to lead to cancers such as leukaemia.
What are the current strategies dealing with the issue of insertional mutagenesis?
- Use of non-integrating vectors.
- Use of vectors with preferred genomic sites of integration (e.g. AAV).
- Development of vectors with targeted/specific chromosomal sites of integration.
- AAV integration at a known location.
What areas are targeted for PD patients and why?
The striatum and the substantia nigra. This is because dopaminergic neurons are located within the substantia nigra and their axon terminals are in the striatum.
What are the barriers and challenges of gene therapy?
- Only 8% of drugs tested in the clinic will enter the market as new medicines.
- Inefficiency of therapy delivered to the CNS because of the BBB.
How can we overcome the issues with the BBB?
- By using intra-CSF delivery via the cisterna magna. This allows for delivery into the brain.
- Lentiviral particles in vivo = these are taken up by nerve terminals of motor neurons, transported up the axon and then express the therapeutic gene.
- Black copolymer nanoparticles that have an analogy with virus structures = you coat nanoparticles with ligands that target specific receptors and channels in the BBB.
What group of diseases can be easily targeted with gene therapies?
Eye retinopathies. You just inject a tiny amount of viral vectors into the eye and they target the affected cells.
What are two approaches in targeting PD?
- Neuroprotective approach. You can introduce GDNF (a trophic factor well know to protect dopaminergic neurons and prevent disease progression) by an antiviral vector.
- Dopamine replacement strategy. This is where a lentiviral vector is injected to provide three dopamine
biosynthesis
enzymes in an attempt to increase the amount of dopamine being produced. This therapy has entered clinical trials.
What gene therapy has been used to treat ALS?
SOD1 silencing. This has shown to rescue motor neurons and increase survival in mouse models.
What gene therapy has been used for SMA?
As a marked pathology of SMA is the loss of the SMN protein, gene therapy has been used to increase the levels of SMN.
This has shown to prolong survival in mouse models.
