Emerging Treatments

Question 1

Inborn errors of metabolism

Answer 1

The largest group of genetic diseases that affect various pathways including carbohydrate, fatty acid and protein metabolism
For example PKU MCAD deficiency maple syrup urine disease and homocystinuria

Question 2

PKU

Answer 2

lack of phenylaline hydroxylase which converted phenylaline to tyrosine
Untreated PKU causes major cognitive impairment,behavioural difficulties,fairer skin and hair
Treated with low protein diet and tyrosine supplements

Question 3

Haemophilia

Answer 3

• Blood clotting disorder known since ancient times
• Causes uncontrolled bleeding
• Bleeding into joints (Causes excruciating pain), into brain and internal bleeding occurs

Question 4

Stages of drug development

Answer 4

• Phase I: first in healthy volunteers less than 100 to see safety
• Phase II: check therapeutic effect on few patients 100-300
• Phase III: large scale therapeutic trials 200-3000

Question 5

Pharmacological chaperones

Answer 5

Fix misfolded proteins

• Some mutations prevent proteins folding properly
• Chaperones aid in folding process and sometimes proteins misfold after which it is subject to degradation by various pathways
• If correctly folded, protein is active and moved down secretory pathway and then moved into cytoplasm or out of cell

Question 6

Fabrys disease

Answer 6

Deficiency of alpha galactosidase A causing build up of globotriaosylceramide
Cause protein misfold
Treat with small molecule chaperone migalastat which is a substrate for for alpha galactosidase A
Mutation specific

Question 7

Pharmacological modulators

Answer 7

• Commonly used drugs
• Can be receptor agonists/antagonists
• Can be ion channel activators/blockers
• Firstly designed to have these effects on mutant receptor or channel e.g. Bcl-abl Kinase inhibitors for treatment of cancers caused by Ph chromosome

Question 8

How have pharmacological modulators helped with cystic fibrosis treatment

Answer 8

Defective chloride ion channel can open if we make a drug that causes activation called Ivacaftor
combination therapy of chaperone and activator can be used for treatment

Question 9

What does stop codon readthrough treat?

Answer 9

• Diseases caused by a non-sense mutation (aka stop mutation) that introduces a stop codon prematurely in the protein sequence
  
  • This prevents protein production.

Question 10

What drugs red through premature stop codons

Answer 10

Eg aminoglycosides that bind to bacterial ribosomes and cause mistranslations

Question 11

DMD involvement in stop codon read through

Answer 11

• DMD caused by a premature stop codon and you get truncated dystrophin
• In BMD there is a missing section
• Theory is if we read through premature stop codon we get a phenotype more like BMD which is much more mild phenotype

Question 12

What is gene therapy

Answer 12

• For a recessive disease we replace defective gene
• For a dominant disease we delete the defective gene

Much easier in vitro (in glass in a lab) + ex vivo (out of the living) than in vivo (in the living)

Question 13

Mitochondrial inherited disease therapy

Answer 13

Requires IVF chromosomes from unfertilised egg with mutated mitochondrial DNA and transfer to unfertilised donor egg with removed nucleus which is then fertilised in vitro and develops to form an embryo (maternal spindle transfer)

Second way is fertilising egg with mutated mitochondrial DNA, removing the resulting pronucleus and transferring it to a fertilised donor egg with a removed pronucleus and letting it develop normally (pronucleur transfer)

Question 14

How does viral gene therapy work

Answer 14

Can engineer a virus’s DNA to carry a therapeutic gene

Question 15

Ex vivo gene therapies

Answer 15

Tread diseases Affecting haemopoitetc cells
Eg SCID aka bubble baby disease where both B and T cell mediated responses are lacking
Treated with bone marrow transplant

Question 16

In vivo gene therapies

Answer 16

Can insert genes in vivo to replace defective genes, useful for treating recessive diseases

Can use injection systemically but most successful in vivo therapies have been local injections in eye, brain or spine

Treats for lack of defective gene

Question 17

Leber congenital amaurosis (in vivo)

Answer 17

It’s a recessive disease cause by mutation in RPE65 (retinal pigment epithelium-specific kilodalton 65 which is involved in generation of visual pigment) which causes progressive blindness through loss of retinal cells
Inject luxturna into eye behind retina which is taken up by cells to make RPE65 proteins

Question 18

Anti sense oligonucleotides

Answer 18

Target against gene
Used for dominant disease caused by gain of function
Are short modified nucleic acids that are complementary to mRNA of gene were interested in. They bind to and block translation of target mRNA destroying it
Cheap

Question 19

Exon skipping using oligonucleotides

Answer 19

Treats deletions for large proteins

Question 20

DMD therapy exon skipping

Answer 20

• DMD is caused by a small deletion that shifts the reading frame and causes a truncated protein
• BMD is caused by a large deletion but the reading frame is left intact
• So exon skipping tries to convert DMD into BMD - much more mild and survivable phenotype

Eteplirsen drug does this- oligonucleotide causes skipping of exon 51 which results in a partially active form of dystrophin

Question 21

Lentivirus

Answer 21

Infected in humans for use in gene therapy

Question 22

RNAi

Answer 22

Regulates activity of gene by silencing or downregulating activity through dSRNA molecules

Question 23

In vitro gene therapy for ADA-SCID

Answer 23

• Treatment called strimvelis and is similar to autologous transplant
• Take bone marrow from patient, isolate HSCs and isolate and expand CD34+ cells
• Transfect them with a lentivirus that encodes ADA and grow transformed cells
• Treat patient with busulfan to kill their own HSCs then reinfuse transformed cells into patient to replace the faults HSCs with healthy ones

Question 24

All functions

Answer 24

Pharmacological chaperons are used to treat protein misfolding. Pharmacological modulators activate or inhibit ion channels. Stop codon read through treats mutations that introduce an early stop codon.ex vivo treats haemopoetic cells via reading and then inserting functional gene. In vivo gene therapy directly introduce the functions, gene which treats recessive disorders. Anti sense oligonucleotides treats dominant disease by destroying faulty mRNA. Exon skipping treats deleterious for large proteins RNAi treats dominant disorders by silencing genes