FDA approved gene therapies Flashcards
why are gene therapeutic used?
for managing difficult to treat diseases- using nanoplexes and other carriers
what is gene therapy?
Human genetic disease= result of mutation or
deletion of gene (s)
what is the aim of gene therapy?
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)
when would gene therapy be used?
more than one
gene affected and no clear identification of the
position (s) of the defect (e.g. cancer,
Parkinson’s & Alzheimer’s disease )
how does gene therapy work?
Delivery of replacement or insertion gene
sequence into cell nucleus
how may dna reach its site of action?
must pass a number of compartments
ie gene transfection
how is DNA and RNA made up?
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
what are the two principle ways of gene delivery to the cell nucleus?
viral and non-viral vectors
what are the risks associated with viral vectors?
safety risks
high immunogenicity after repeated admin
potential oncogenicity due to mutagenesis
what size must dna be in viral vectors?
small size
how do non- viral vectors work?
coupling on polymers
what size molecules can be carried by non-viral vectors?
large DNA molecules can be carried
what are the benefits of non-viral vectors?
can be produced in large quantities easily and inexpensively
significantly lower safety risk
do non-viral vectors have a low or high transfection efficiency?
low
what are the problematic properties of DNA?
*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
what are the problems associated with in vivo-gene delivery by cationic liposome dna complexes?
*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
what is PEI?
Gene delivery using cationic polymers
Polyethylene imine (PEI)
*Gold standard of non viral vectors
what are the properties of PEI?
*Can complex large DNA molecules
*Homogeneous spherical particles (~ 100 nm in size)
*Protection against nuclease degradation
*Fairly toxic
what are obsticles to gene therapy?
immune reactions
when is VEGR used?
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.
what is chitosan?
Chitosans are biodegradable, linear amino
polysaccharides with a random distribution of b–
1,4–N–acetyl–D–glucosamine and D–
glucosamine.
is chitosan safe?
They are derived from the biopolymer chitin and
are used in food preparations.
Hence, their use is safe.
what are the properties of chitosan?
The polyplexes formed are stable, small and
toroidal in shape i.e. their appearance is similar
to a tyre or a hollow ring.
how does chitosan protect DNA?
The DNA is entrapped in the inner cavity
and hence protected from degeneration by
DNase.
how does chitosan stay stable and transfect target cells?
the amount of positively
charged monomer units in the polyplexes
must be greater than 65%.
