Emerging Treatments Flashcards
What are unborn errors of metabolism?
Largest group of genetic disorders
Affect variety of pathways e.g. carbohydrates, fatty acids, protein metabolism
They’re caused by lack of an enzyme in that pathways which leads to increased substrate levels
What is phenylketonuria (PKU)?
Lack of phenylalanine hydroxylase which is needed for phenylalanine to tyrosine conversion
Instead we get phenylalanine to phenylketones
What are symptoms of untreated PKU genes?
Major cognitive impairment
Behavioural difficulties
Fairer skin, hair and eyes- lack of melanin
Recurrent vomiting
How is PKU treated?
Treated with low protein diet
Tyrosine supplements
What is haemophilia?
Blood clotting disorder- causes uncontrollable bleeding
Bleeding occurs in joints which causes excruciating pain
You can get bleeding into brain and internal bleeding
What haemophilia treatments are there?
Cryoprecipitate transfusion:
FVIII concentrate
Freeze-dried plasma-derived factor concentrates
What is the haemophilia blood scandal?
1970-1980
3000- 5000 given clotting factors contaminated with HIV and Hepatitis
2500 died so far
How are clotting factors now treated to make them safe for transfusion?
Use of recombinant factor VIII treatment- genetically engineered
Donor and blood screening
Heat treated product to kill virus
What other diseases are treated by replacement therapy?
Growth hormone deficiency- GH now recombinant
Lysosomal storage diseases- effect lysosomal breakdown e.g. Fabry’s disease (treated with recombinant alpha galactosidase A) and pompe disease (treated with alpha glucosidase)
Who approves drugs for the NHS?
England and Wales: National institute for health and care excellence (NICE)
Scotland: Healthcare improvement Scotland
What are pharmacological chaperones?
Protein folding is complex and sometimes fails
System in ER degrades misfolded protein
A pharmacological chaperone binds to the misfiled protein and folds it into the correct shape
What is an example of a pharmacological chaperone?
In Fabrey’s disease theres a deficiency of alpha galactosidase A
This leads to a build up of globotriaosylceramide
Migalostat is a small molecule chaperone,
It binds to the misfolded enzyme and stabilises the enzyme in the correct shape
Mutation specific
What are pharmacological modulators?
Receptor agonists/ antagonists
Ion channel activators/ blockers
Have an effect on a specific mutant channels or receptors
What is an example of a pharmacological modulator?
Cystic fibrosis leads to defective chloride channels - mutation causes channel not to open
Ivacaftor is a drug designed to open these channels
It’s mutation specific
What is an example of combination therapy?
Some cases of CF are due to mutation as a cause of misfolding which leads to inactive channel
They’re treated with a combination of chaperone and activator (pharmacological modulator)
e.g. Orkambi (Ivacaftor / lumacaftor)
How do drugs cause stop codon read through?
Some diseases are caused by a non-sense mutation- premature stop codon
This prevents protein production
Aminoglycoside antibiotics bind to 30S ribosome subunit and cause mistranslation - it reads through the stop codon
What is an example of a stop codon read through drug?
Duchenne muscular dystrophy is a result of a premature stop codon
Becker MD is caused by a missing section
If we read through the premature stop in DMD we get BMD
E.g. Ataluren
Non-sense specific mutation
What are mitochondrially inherited disease therapies?
Performed In- vitro
Takes DNA from fertilised egg that has mutated mitochondrial DNA
Transfer to donor egg with nucleus removed
Fused egg is fertilised in vitro
Its known as 3 parent babies
What is virus gene therapy?
We can engineer viruses to carry therapeutic gene
Wide variety of uses: Adenovirus, lentivirus
Virus choice depends on target tissue
What is SCID?
Severe combined Immuno-deficiency
Bubble boy disease
Lack both B and T cell mediated response
Severe forms includes: X- linked SCID and Adensosine deaminase deficiency (ADA-SCID)
How is SCID treated?
Can be treated with bone marrow transplant
Not possible for all children however
What therapy is used for ADA-SCID?
Treatment called strimvelis Autologous transplant Isolate patient's haematopoietic stem cells Isolate and expand CD34+ Transfect with ADA- lentivirus Grow transformed cells Treat patient with busulfan (kills HSC) Reinfuse transformed cells into patient
How do in- vivo therapy supplements work?
There useful for conditions where theres a lack of a functional gene
Uses a virus to carry in a working copy of the gene
Can be injected systemically and injected locally
What is an example of a disease treated with in-vivo therapy supplements?
Leber congenital amaurosis type 2
Recessive disease caused by mutation of RPE65
Leads to loss of retinal cells- progressive blindness
Treatment: Luxturna rAAV2 expressing RPE65
Not a cure but improves vision
Patients need sufficient remaining cells
How are anti-sense oligonucleotides used for gene therapy?
They’re short modified nucleic acids, complimentary to target
Modification prevents degradation and allows entry to cell
It binds to the target and blocks translation. It can also alter splicing
Relatively cheap to make
What is an example of an anti-sense oligonucleotide treatment?
Useful for diseases caused by a gain of function
E.g. inotersen
Used in treatment of transthyretin - related hereditary amyloidosis
Caused by mutation in transthyretin (TTH)
TTH cant form tetramers, this forms aggregates which damage tissues
Inotersin binds to mRNA which encodes mutant transthyretin and degrades them
Slows progression of disease
How can anti-sense oligonucleotides be used for exon skipping?
During pre-mRNA processing, oligonucleotides can cause exons to be skipped
This can be used to skip disease causing exon
Anti-sense oligonucleotide binds to acceptor site of exon and blocks it from acting as an acceptor site
Treatment is limited:
- exon skipped must not be vital
- Generally only large proteins
What is an example of exon skipping treatment?
In DMD exon skipping used to convert DMD to BMD
E.g. Eteplirsen- oligonucleotide used to skip exon 51. Will result in partially active dystrophin
What is CRISPR- cas9
Bacterial system disables bacteriophages (viruses that infect bacteria)
Clustered Regularly Interspaced Short Palindromic Repeats
CRISPR- derived from previous bacteriophage infection in bacteria
Cas9- CRISPR associated protein 9- its an endonuclease so will cut DNA sequences
Recognises and cleaves DNA CRISPR hybrids
What is CRISPR-Cas9 used for?
Gene correcting relatively small changes
Cannot correct large changes (deletions, triplet expansion)
Many have off-target effects
Not currently used in humans- controversial and illegal in most of world
How has CRISPR-Cas9 been used in in-vitro gene editing?
Used to alter the genome of IVF embryo
Deleted CCR5 in twins
