Emerging Treatments Flashcards
How do errors in metabolism lead to disease
Lacks enzyme
Can’t make product
Leads to excess substrate
Leads to alternative product which may cause disease
Examples of metabolic error diseases
PKU ( Protein Ketone Urea)
MCAD Deficiency
Maple Syrup urine disease
Homocystinuria
PKU ( phenylketonuria) cause
Caused by a lack of phenylalanine hydroxylase ( enzyme) and this leads to the creation of phenylketones which are neurotoxic and kills brain cells.
Symptoms of untreated PKU
Major cognitive impairment Behavioural difficulties Fairer skin , hair and eyes than siblings Lack of melanin Recurrent vomiting
Treatment of PKU
Treatment with low protein diet - tyrosine supplements
Haemophilia symptoms
Uncontrolled bleeding Bleeding into joints Excruciating pain Bleeding into brain Internal bleeding
Can be fatal if untreated
Haemophilia treatment
Fresh Frozen Plasma
Solutions to contaminated blood scandals for FFP
Heat treat products kills virus
Factor 8 can be cloned
Recombinant factor 7 treatment
Pompe disease treatment
Injection of alpha glucosidase
Lysol also storage disease
Injection recombinant alpha galactosidase A/ agalsisase beta ( faradenzyme)
Do therapies targeting proteins cure the disease
No they are treatments not cures as they try to normalise the function of mutant proteins - they treat the condition not the symptoms so need to take these treatments for as long as you live
What are pharmacological chaperones
Protein folding is complex sometime fails
System in endoplasmic reticulum degrades misfolded proteins
Some mutations prevent proteins folding properly > so they are subject degradation pathway
If folded correctly would be active
Chaperones can stabilise the shape of the protein so it folds properly and does not get degraded. (It’s acts as a competitor to the original defective enzyme)
Example of a pharmacological chaperone
Fairy disease - deficiency of alpha galactosidase A
Build up of glonotriaosylceramide
Some mutations cause misfolding of proteins
Migalastat small molecule chaperone
Stabilises enzyme in correct shape
Pharmacological modulators
Pharmacological modulators are commonly used drugs
Receptor agonists/antagonist
Ion channel activators/blockers
Can design one that has these effects on mutant receptor or channel
Bcl-abl Kinase inhibitors (Philadelphia chromosome)
Cystic fibrosis
Defective chloride channel
Mutations (33) cause channel not to open
Design a drug which causes activation - Ivacaftor
Is mutation specific
Example of combination therapy
Cystic fibrosis
Defective chloride channel + One mutation (f508del) misfolded, inactive channel
Treat with combination chaperone and activator (turns it on in situations when it wouldn’t be on)
Orkambi (Ivacaftor/lumacaftor) – NICE approved Oct ’19
Not cure but does improve lung function
Diseases caused by stop codon read through
Some diseases are caused by non sense mutations where there is a premature stop codon
This prevents protein production
Example of a drug which treats non sense mutation
Mutation causes release factors to bind prematurely and so there is a shorter protein formed. Aminoglycoside antibiotics bind to the ribosome and causes mistranslation . Drugs based on these prevent the release factors from binding and so a full length DNA is produced
Aminoglycoside Abs is an example as it binds to ribosome causing mistranslation so skip the nonsense in a loss of function
Duchenne muscular dystrophy
DMD premature stop codon and Becker Muscular dystrophy has a missing section
If read through premature stop codon DMD-> BMD
Atalurenis an example
But it is non sense mutation specific and so doesn’t cure but reduces the symptoms
In vivo
In living
Ex vivo
Out of the living
In vitro
In glass ( foetus)
How to fix a recessive diseases by gene therapy
Recessive disease - rePlace defective gene
Dominant disease - delete defective gene
Why is in vivo hard
Very difficult to achieve in practice Achieving specificity Getting therapy to right place Maintaining expression Much easier to achieve in vitro than in vivo
In vivogene therapy means that therapy is administered directly the patient. The targeted cells remain in the body of the patient. Withex vivogene/cell therapy the targeted cells are removed from the patient and gene therapy is administered to the cellsin vitrobefore they are returned to the patient’s body.
How does mitochondrially inherited disease therapy work
It is ex vivo / in vitro
Only effective therapy
Requires IVF
Take DNA from fertilised patient egg
Transfer to donor egg normal mitochondria
Virus gene therapy
Can Engineer virus to carry therapeutic gene Wide variety of virus used AAV Adenovirus Lentivirus – HIV Vaccinia
Virus choice depends on target tissue : virus tropism has affinity of injecting certain viral phenotypes
Amount of DNA limited depends on virus
In vitro gene therapy SCID
X linked
Can be treated with bone marrow transplant as it is caused by adenosine dealings deficiency
But not possible for all children (90% ADa -SCID) no match
Has own risks
Process of treating in vitro gene therapy ADa -SCID
Strimevelis Autologous transplant Isolate patients Haemopoietic stem cells Isolate and expand CD34+ Transferred with ADA -lentivirus Grow transformed cells Treat patient with busulfan (kills HSC) Reinfused transformed cells into patients
In vivo therapy supplement
Lever congenital amaurosis type 2
Recessive disease caused by mutation REP65
Progressive blindness - loss of rentinal cells
Luxturna rAAV2 expressing RPE65
Not cure ; greatly improves vision
Patients need sufficient remaining cells
Anti sense oligonucleotides
Shortnmodifies nucleic acid complementary to target
Modification prevents degredation allow entry to cell
Binds to target
Block translation
Can also alter splicing
Relatively cheap
In vivo therapy knockdown
Useful for disease caused by gain of function
Inotersen -
Transthyretin- related hereditary amyloidosis
Mutation in transthyretin ( TTH)
TTH cannot form tetramers , forms aggregates
Mutation specific
Transthyretin related hereditary amyloidosis
Symptoms between 20-40
Pain muscle weakness and this eventually leads to heart and brain problems
Insotersen binds to wildtype mRNA and stop production /slows down overall rate of production
Exon skipping
During pre-RNA processing
Oligonucleotides cause exon to be skipped
Can be used to skip disease causing exon
To put RNA back in reading-frame
Useful in limited circumstances
Exons skipped mustn’t be vital otherwise worse damage
Generally only large proteins - small proteins will lose too much
Exon skipping in duchenne muscular dystrophy
Duchenne muscular dystrophy – premature stop (nonsense)
Becker muscular dystrophy – missing section
If prevent incorporation mutant exon DMD → BMD
It skips an exon and moves it back into frame.
Drug used to treat exon skipping in duchenne muscular dystrophy
Eteplirsen – oligonucleotide cause skipping exon 51
Will result in production partially active dystrophin
Gene editing CRISPR- Cas 9
Bacterial system disable bacteriophages
Clustered Regularly Interspaced Short Palindromic Repeats
CRISPR – derived from previous bacteriophage
CAS9- Crispr associated protein 9- Endonuclease
Recognises and Cleaves DNA CRISPR hybrids
Gene editing correct relatively small errors
Cannot correct large changes
Large deletions OR triplet expansion
May have off target effects Not currently used in humans (1 exception) Same problem as other methods Targeting Getting into cell
