FDA approved gene therapies

Question 1

why are gene therapeutic used?

Answer 1

for managing difficult to treat diseases- using nanoplexes and other carriers

Question 2

what is gene therapy?

Answer 2

Human genetic disease= result of mutation or
deletion of gene (s)

Question 3

what is the aim of gene therapy?

Answer 3

To treat the cause rather than the
symptoms of the diseases= caused by single
gene mutation or deletion (e.g. Haemophilia,
Cystic fibrosis, Muscular dystrophy)

Question 4

when would gene therapy be used?

Answer 4

more than one
gene affected and no clear identification of the
position (s) of the defect (e.g. cancer,
Parkinson’s & Alzheimer’s disease )

Question 5

how does gene therapy work?

Answer 5

Delivery of replacement or insertion gene
sequence into cell nucleus

Question 6

how may dna reach its site of action?

Answer 6

must pass a number of compartments
ie gene transfection

Question 7

how is DNA and RNA made up?

Answer 7

DNA= deoxyribonucleic acid, carbohydrate unit
2-D-Deoxyribose
= represents genetic material
RNA= ribonucleic acid, carbohydrate unit 2-D-
Ribose
= essential for biosynthesis of proteins
=different types; here important mRNA

Question 8

what are the two principle ways of gene delivery to the cell nucleus?

Answer 8

viral and non-viral vectors

Question 9

what are the risks associated with viral vectors?

Answer 9

safety risks
high immunogenicity after repeated admin
potential oncogenicity due to mutagenesis

Question 10

what size must dna be in viral vectors?

Answer 10

small size

Question 11

how do non- viral vectors work?

Answer 11

coupling on polymers

Question 12

what size molecules can be carried by non-viral vectors?

Answer 12

large DNA molecules can be carried

Question 13

what are the benefits of non-viral vectors?

Answer 13

can be produced in large quantities easily and inexpensively
significantly lower safety risk

Question 14

do non-viral vectors have a low or high transfection efficiency?

Answer 14

low

Question 15

what are the problematic properties of DNA?

Answer 15

*Highly charged polyelectrolyte
*Due to extra- and intracellular electrolyte concentrations stretched out
*Due to negative charge repulsive electrostatic interaction between DNA and negatively charged cell surface
*DNA size 800 nm to 10 μm
*Maximum possible size of DNA complex <1000 nm
*Carrier systems (DNA complexes)
*strong enough to protect DNA from blood plasma DNases
*weak enough to release DNA inside the target cells

Question 16

what are the problems associated with in vivo-gene delivery by cationic liposome dna complexes?

Answer 16

*Net positive charge
- when administered, for example, i.v. complexes will encounter negatively charged entities: serum proteins, lipoproteins and blood cells
- risk of flocculation and embolism
- positively charged particles are cleared from the circulation via reticuloendothelial system
*Pulmonary delivery
- encounter of lung surfactants
*Loss of positive charge leads to deterioration of transfection performance

Question 17

what is PEI?

Answer 17

Gene delivery using cationic polymers
Polyethylene imine (PEI)
*Gold standard of non viral vectors

Question 18

what are the properties of PEI?

Answer 18

*Can complex large DNA molecules
*Homogeneous spherical particles (~ 100 nm in size)
*Protection against nuclease degradation
*Fairly toxic

Question 19

what are obsticles to gene therapy?

Answer 19

immune reactions

Question 20

when is VEGR used?

Answer 20

For cardiovascular diseases
Gene therapy with VEGF has shown in
clinical trials to increase formation of new
vessels (angiogenesis) in ischaemic tissues
*Angiogenesis has therapeutic potential to
improve vascularisation in areas of
decreased blood flow caused by ischaemic
heart disease.

Question 21

what is chitosan?

Answer 21

Chitosans are biodegradable, linear amino
polysaccharides with a random distribution of b–
1,4–N–acetyl–D–glucosamine and D–
glucosamine.

Question 22

is chitosan safe?

Answer 22

They are derived from the biopolymer chitin and
are used in food preparations.
Hence, their use is safe.

Question 23

what are the properties of chitosan?

Answer 23

The polyplexes formed are stable, small and
toroidal in shape i.e. their appearance is similar
to a tyre or a hollow ring.

Question 24

how does chitosan protect DNA?

Answer 24

The DNA is entrapped in the inner cavity
and hence protected from degeneration by
DNase.

Question 25

how does chitosan stay stable and transfect target cells?

Answer 25

the amount of positively
charged monomer units in the polyplexes
must be greater than 65%.