Emerging Treatments

Question 1

What are in born errors of metabolism?

Missing factors = treatments based on diet and enzyme replacement, not mutation specific

Answer 1

Usually lacking an enzyme

Usually affects Carbs, Fatty acid and protein pathways

Question 2

What disease examples of in born errors of metabolism are there? ( 4 )

Answer 2

PKU

MCAD deficiency
( Medium-chain acyl-CoA dehydrogenase )

HCU ( homocystinuria )

Maple Syrup Urine disease

Question 3

What are the characteristics of PKU? Disease and symptoms?

Answer 3

Phenylketonuria:

There are no Phenylalanine hydroxylases to create Tyrosine . decreased tyrosine and more phenylalanine turning to phenylketones

Symptoms: Major Cog-impairment, behavioural difficulties.
Fair skin, hair, eyes than siblings
Recurrent vomiting

Question 4

What PKU treatment is available?

Answer 4

Low protein diet : Tyrosine supplements

• Can identify enzyme deficiency : Km is increases and Vmax decreased on a graph

Question 5

What are the characteristics of Haemophilia?

Answer 5

Blood clotting disorder causing uncontrolled bleeding into joints, brain, internal bleeds.

Treatments started in 1940s and developed overtime from whole blood transfusions to Factor 8 plasma, F8 concentration

Currently use: Recombinant factor 8 treatment

Question 6

What are the characteristics of Lysosomal storage diseases?

What replacement injections are there for both types?

Answer 6

Effect lysosomal breakdown
e.g.
Fabry disease = injection of recombinant α-galactosidase A
Pompe disease = injection of α-glucosidase

Question 7

What do Pharmacological therapies do?

Answer 7

They treat conditions not symptoms. NOT CURE

They aim to normalise mutant protein function

Question 8

What do Pharmacological chaperones do to help?

Answer 8

When protein folding fails due to mutation degradation can occur
Chaperones can stabilise enzyme in correct shape

Question 9

What is the Pharmacological chaperone used in Fabry disease?

Answer 9

A deficiency of α-galactosidase A due to muatation caused misfolding
Causes build up of globotriaosylceramide

Migalastat = small molecule chaperone

Stabilises enzyme in correct shape

Question 10

What do Pharmacological modulators do to help?

Answer 10

Act as receptor agonists/antagonists so can activate or block ion channels

( can use effects on mutant receptor or channel )

e.g. bcr abl kinase inhibitor CML

Question 11

Pharmacological modulator use in Cystic Fibrosis?

Answer 11

Has defective chloride channel due to Mutation ( 33 ) ∴ channel does not open

Ivacaftor is a mutation specific drug : activates channel

Question 12

How is combination therapy used to treat Cystic Fibrosis?

Answer 12

mutation : f508del, misfolded inactive channel

Chaperone ( misfolded) and activator (ion channel ) combination

Orkambi ( ivacaftor / lumacaftor )

does NOT CURE but improve lung function

Question 13

How does stop codon read through help?

Answer 13

Pharmacological modulator

Stop codons cause premature proteins

Drugs can bind to ribosome - cause mistranslation and read pass the non-sense mutations to rescue protein

.e.g aminoglycoside antibiotics bind to ribosomes

Question 14

Use DMD as an example of stop codon read through?

Answer 14

Duchenne muscular dystrophy = premature stop
Becker muscular dystrophy = missing section

Can turn DMD –> BMD by reading through stop codon

Drug: Ataluren

• BMD has a less severe phenotype so px can live longer

Question 15

What does Gene therapy do?

Answer 15

Blocks genes skipping disease exons = mutation specific
May or may not be a cure

Recessive : need to replace defective gene
Dominant : delete defective gene

Question 16

Why is Gene therapy easier in vitro followed by ex vivo and lastly in vivo?

Answer 16

In vitro : in glass

ex vivo : out of living ( virus + px stem cells = new cells which are introduced to px )

in vivo : in living ( inject viral vector )

Question 17

Describe mitochondrially inherited disease therapy? And the two methods involved

Answer 17

Take DNA from fertilised px egg
Transfer donor egg to normal mitochondria

Method 1 - Maternal spindle transfer:
Chromosomes removed from egg which has mutated mDNA
Added to donor enucleated egg cell which is fertilised in vitro = embryo

Method 2 - Pronuclear transfer:
Mutated mDNA egg fertilised. Resulting pronucleus removed and transferred to fertilised enucleated donor egg = embryo NOT APPROVED in UK, 3 parent babies

Question 18

How does virus gene therapy work?

Answer 18

Can engineer virus to carry therapeutic gene

e.g. AAV, Adenovirus, HIV, Vaccina depending on target tissue

Question 19

What are the characteristics of SCID?

Answer 19

Severe combined immuno-deficiency ( bubble baby disease )
Lack T and B cell response

Mostly X linked 70%
Adenosine deaminase deficiency ( ADA- SCID ) 15%

Treatment: Bone marrow transplant
* ADA-SCID 80%x does not match for transplant

In vitro gene therapy

Question 20

Describe In vitro gene therapy ADA-SCID?

Answer 20

Drug: Strimvelis

Autologous transplant
Isolate px hemopoietic stem cells
Isolate and expand CD34+
Transfected with ADA-lentivirus
Grow transformed cells
treat px with bulsulfan - kills HSC
Reinfused transformed cells into Px

Question 21

What is an example of In vivo therapy supplement?

In vitro therapy can supplement is a px is lacking a working gene, can inject systemically, or locally in eye spine brain etc

Answer 21

Leber congenital Amaurosis Type 2 is a recessive genes caused by mutation RPE65 = progressive blindness

Luxturna rAAV2 expresses RPE65 which improves vision

patients require sufficient remaining cells, not a cute but greatly improves vision

Question 22

What are Anti-sense oligonucletotides used for?

Answer 22

In vivo

Short nucleic acids complementary to targets.
Once bound to target it blocks translation = can alter splicing.

• Pre-RNA processing
• can skip disease causing exon
• RNA back into reading frame
• usually for larger proteins

( - ) useful in limited situations
( + ) cheap

Question 23

What are the characteristics of Transthyretin-related hereditary amyloidosis?

( in vivo knockdown therapy )

Answer 23

Mutation in Transthyretin ( TTH )
So cannot form tetramers : forms aggregates

Aggregate –> deposits in tissues –> damage tissue –> progressive and fatal heart, kidney, muslce weakness and pain.

Treated by Inotersen : binds to mRNA, activates RNase H1, cleaves mRNA into fragments

Question 24

How can Exon skipping be applied to DMD?

Answer 24

Can prevent the incorporation of mutant exon so phenotype is BMD.

Drug: Eteplirsen ( oligonucleotide skips exon 51 )
Results in partially active dystrophin

Question 25

Why may Gene editing be used?

Answer 25

Gene editing corrects relatively small errors, but can’t correct large changes -

( - ) May have off-target effects and struggles to get into the cell.

Not currently used on humans except one exception.

Question 26

How is gene editing currently used on humans?

Answer 26

Use of CRISPR-Cas to alter genome of IVF embryos
Deleted CCR5 gene in twins
Controversial - illegal in most of the world
Could use to prevent genetic disease
( - ) Need to identify prior to conception

Used in Russia to prevent heritable deafness

Question 27

in born errors of metabolism growth hormone deficiency?

Answer 27

Give recombinant injection

Question 28

Extra missed info?

Answer 28

.