Gene therapy Flashcards
(10 cards)
What disorders are antisense oligonucleotide therapies used in?
1) Spinal muscular atrophy: Nusinersen
2) Duchenne muscular dystrophy: Casimersen
3) Batten disease: Milasen (example of personalised ASO)
5) Amyotrophic lateral scleroisis (ALS): Tofersen
7) Familial hypercholesterolemia: Mipomersen
Discuss potential use for antisense oligonucleotides in neurodegenerative disorders
1) Huntingtons disease: IONIS-HTTRx or Tominsersen reduced mutant HTT mRNA, improving phenotype in mice
2) Parkinsons disease: target SNP in SNCA and LRRK2 genes, reduced aSyn production in rodents; target PARK2 for exon skipping (ie rare PD)
3) SOD1-related ALS: Tofersen reduces SOD1 protein (toxic) production, slowing decline of ALS
ASO for HD and PD in clinical trials, not currently available
PARK2 ASO therapy needs to be validated in animal models, bc it is only small percentage of PD, it could be regarded as an orphan drug, and fast-tracked
Discuss use of antisense oligonucleotides in neuromuscular diseases
1) Spinal muscular atrophy: Nusinersen targets SMN2 pre-mRNA to include exon 7, produces functional SMN protein, improving motor function/survival
2) Duchene musclar dystrophy: ASOs target DMD pre-mRNA to skip exons (eg Casimersen: exon 45) (one drug one patient potential)
3) Myotonic dystrophy type 1: Baliforsen targets DMPK exon 9, reducing CUG repeats, but improved drug delivery is needed since ASOs dont cross BBB
Myotonic dystrophy type 1 is an autosomal dominant disease resulting from expansion of CTG repeats in the 3ʹ non-coding region of the DM1 protein kinase (DMPK) gene
The disease mechanism involves a toxic gain-of-function of DMPK transcripts that carry expanded CUG repeats (CUGexp), which form nuclear foci in myotonic dystrophy type 1-affected tissues, such as muscle, heart, and brain, among others
Discuss use of antisense oligonucleotides in neurodevelopmental disorders
1) Timmothy syndrome: skip exon 8A, ASO intrathecal admin in rats w organoid transplant downregulated 8A, decreased impaired calcium signalling and dendritic morphology
2) Rett/MECP2 duplication syndrome: block miRNA repression of MECP2 (inc expression+ BDNF)/ reduce MECP2 expression
2) Angelman syndrome: supress UBE3A antisense transcript to increase UBE3A expression
ALL in preclinical development
Problem w Rett syndrome gene therapy: can result in MECP2 overexpression which can result in phenotype in MECP2 duplication syndrome
What are ASOs?
antisense oligonucleotides
Synthetic single-stranded DNA that interact with pre-mRNA, targetting it for degradation
They can target heterozygous single-nucleotide polymorphisms for silencing, useful as therapeutics (gene therapy)
Other examples of RNA-based therapies include miRNAs and siRNAs
What are downsides of ASOs
- Not permenant because dont affect DNA, so require multiple doses
- Delivery limitations (doesnt penetrate BBB, intrathecal admin is painful)
- Off target effects: potential to bind similar RNA, or activate immune respones
- Bc personalised (batten syndrome, DMD), SUPER high cost
How is gene therapy used in Sickle cell disease?
Lentiviral transduction of autologus hematopoietic stem and progenitor cells (HSPCs) can be reinfused after myeloblation
CRISPR/Cas9 can also be used in the same context, correcting HBB gene (targeting it for DBS and HDR), or to promote fetal hemoglobin production (BCL11A enhancer KO- Casgevy, or disrupt repressor binding site on HBG1/HBG2 promotor- EDIT-301)
Base editing (GTG to GCG to make HBBG which has same function as healthy adult B-globin) is also being explored
Compare and contrast EDIT-301 and Casgevy
Both: ex vivo editing of CD34 autologus hemotopoietic stem cells, increase fetal hemoglobin production, treat SCD and beta-thalassemia
Casgevy: SpCas9, knocks out BCL11A enhancer, FDA approved, blunt ends
EDIT-301: AsCas12a, disrupts repressor binding sites on HBG1/HBG2 promotor region, in clinical trials, sticky ends
EDIT-301’s use of Cas12a may result in higher precision, fewer off-target effects, and improved editing at AT-rich sites like the HBG promoters.
How is gene therapy used in cancer?
Adoptive T cell therapy
- CAR T-cell: engineered to express synthetic chimeric antigen receptor, (combined with anti-IL-6 receptor for CAR T-cell toxicity)
- TCR T-cell therapy: engineered to express specific TCR that recognises known antigen to induce cytotoxic T-cell effector functions
- TCR neoantigen T-cell therapy: engineered to express TCR against neoantigen (can be specific to patient’s tumor) (example of personalised medicine)
TIL= tumor infilrating lymphocytes
Identification of neoantigens was made possible by NGS and advancements in bioinformatic technologies
How is gene therapy used in Rett syndrome?
Prescion medicine approach:
- ASOs
- Lentiviral vectors expressing MECP2
- AAV9 vectors administered intracerebrally
