NUCLEIC ACID THERAPEUTICS

2. Nucleic acid therapeutics
BY
DR. QURESHI JALIB

3. Nucleic acid therapeutics
These compounds contain nucleic acids or closely
related chemical compounds.
These are used in the treatment of diseases where
inhibition of function of a particular gene is
therapeutically desirable.
It includes:
1)DNA based therapeutics
2)RNA based therapeutics
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4. PROPERTIES OF NUCLEIC ACID
THERAPEUTICS
 Highly specific
 Defined chemical structure
 Easy to synthesize
 Diverse route of administration
 Less toxic
 Non infectious
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5. DNA based therapeutics

6. DNA based therapeutics
• Plasmids
• Oligonucleotides/DNA antisense
• DNA Aptamers
• DNA- zymes
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7. Plasmids
Plasmids are high molecular weight , double stranded
DNA molecules.
Plasmid DNA molecules are administered as prodrugs,
that provide DNA transcription and translation
apparatus for protein synthesis.
Plasmids can also be used as DNA vaccines to treat
allergic reactions.
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8. Oligonucleotides
These are short single stranded DNA molecules that
inhibit the expression of a single protein.
Oligonucleotides provides antisense and antigenic
applications.
1) Antisense applications:
For antisense applications oligonucleotides interact
with mRNA and form a duplex or pre-mRNA and inhibit
its translaion,thereby inhibiting the protein synthesis.
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9. Continued…
2) Antigenic applications:
For these applications oligonucleotides enter the cell
nucleus, forms a triplex with double stranded genomic
DNA and inhibit transcription as well as translation
process of protein synthesis. First antisense drug,
Fomivirsen sodium used for cytomegalovirus retinitis in
AIDS patients was approved in 1998.
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11. DNA Aptamers
DNA Aptamers are double stranded nucleic acid segments
that can directly interact with proteins.
Aptamers are preferred over antibodies in protein
inhibition due to their high specificity, non
immunogenicity and stability of formulation.
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13. DNA-zymes
These are analogs of ribozymes with greater
biological stability.
DNA-zymes contain 10-23 nucleic acids.
They have advantage over ribozymes because
ribozymes can be effected by RNAse but DNA-
zymes can not be effected by RNAse due to the
presence of DNA backbone.
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15. RNA based therapeutics

16. RNA based therapeutics
• RNA Aptamers
• Antisense RNA
• Ribozymes
• Micro RNAs
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17. RNA Aptamers
RNA Aptamers are single stranded nucleic acid segments
that can directly interact with proteins. Aptamers recognize
their target on the basis of shape.
Their binding affinity and specificity for target are extremely
high , similar to monoclonal antibodies.
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18. Antisense RNA
Antisense drugs are short strands of
deoxyribonucleotide that bind to specific areas of
mRNA to block gene expression.
Newer antisense oligonucleotides may have
improved pharmacokinetic and safety profiles.
Another major advantage is the lack of
immunogenicity, as oligonucleotides and cells
producing them will not be affected by host immune
response.
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20. Ribozymes
Ribozymes are enzymatic RNA strands which break the target
RNA once the RNA-RNA duplex has formed.
Ribozymes can be destroyed by RNAse.
Two types of ribozymes have been used because of their small
size and rapid kinetics.
1)Hammer head ribozymes.
2)Hairpin ribozymes.
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21. Micro RNA
Micro RNAs naturally occurring , small non coding
RNA molecules with 21-25 nucleotides in length.
These molecules are partially complementary to mRNA
and their main function is inhibition of gene
expression through inhibition of translation or mRNA
cleavage.
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23. GENE TRANSFER TECHNOLOGIES

24. Gene transfer technologies
These are classified into three types:
1) Mechanical technique.
2) Electrical technique.
3) Vector assisted delivery system.
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25. Mechanical and electrical technique
Mechanical and electrical techniques for transferring
gene into cell include following methods:
1) Micro injection.
2) Particle bombardment.
3) Use of pressure.
4) Electroporation.
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26. 1)Microinjection:
Microinjection is highly efficient since one cell at a
time is targeted for DNA transfer, but it is time
consuming.
2)Particle bombardment:
gene guns are used for particle bombardment.
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27. 3) Electroporation:
In this method an electric current is applied to living
cells (as skin or cell membrane) in order to open pores
or channels through which something (as drug or DNA)
may pass.
In this method high voltage electric current is required
for gene transfer.
Due to high voltage electric current the cell mortality
may high and this method is not suitable for clinical
use.
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28. Vector assisted delivery system
Vector assisted delivery system is classified into
two types;
1) Biological viral delivery system.
2) Chemical nonviral delivery system.
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29. Viral delivery system
In Viral Delivery Systems, nonpathogenic attenuated
viruses can be used as delivery systems for genes/DNA
molecules, especially plasmids. These viral DNA-delivery
vectors include both RNA and DNA viruses.
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30. The viruses used as gene therapy vectors can
be classified into four types:
• Retroviruses.
• Adenoviruses.
• Adeno-associated viruses.
• Herpes simplex viruses.
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31. Uses of viral delivery system
Viral delivery system is used in the treatment of
following diseases
 Muscular dystrophy.
 AIDS.
 Cancer.
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32. Nonviral delivery system
Commonly used nonviral vectors for delivery of
nucleic acid therapeutics can be classified into three
major types:
i. Naked DNA delivery system.
ii. Polymeric delivery system.
iii. Liposomal delivery system.
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33. Polymeric delivery system
In polymeric delivery systems, cationic polymers are
used in gene delivery because they can easily
complex with the anionic DNA molecules.
Encapsulation of a DNA molecule or even a
therapeutic viral vector within a biodegradable
polymer has been demonstrated to permit the
controlled release of the DNA in a targeted cell
over a period of weeks or months.
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34. Commonly used polymers
Commonly used polymers include:
Polyethylenimine
Poly-L-lysine
Chitosans
Dendrimers.
Some polymers have inherent potent pharmacological
properties (such as hypercholesterolemia induced
by chitosans) that make them extremely unfavorable for
human use.
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35. Liposomal drug delivery system
Liposomes are one of the most versatile tools for the
delivery of DNA therapeutics.
Liposome can also be used to provide:
 long circulation half-life.
 sustained drug delivery.
 targeted delivery.
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36. references
 Agarawal S, Tang JY (1992) GEM-91-an antisense
oligonucleotide phosphorothioate as a therapeutic agent
for AIDS. Antisense Res Dev 2:261–266.
 Anil A (2003) Undercover genes slip into the brain.
http://www.newscientist.com/section/sciencenews/.
22 Mar 2003.
 Caplen NJ (2004) Gene therapy progress and prospects.
Downregulating gene expression: the
impact of RNA interference. Gene Ther 11:1241–1248.
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