3. Introduction
● Aptamers – single stranded DNA / RNA molecules that bind to
protein targets by folding into a three dimensional conformation,
similar to antibodies
● APTUS – fit ; MEROS – part or region
3
4. History
● HIV – RNA has specific sequence -“Trans Activation Response (TAR)”
● TAR RNA binds with cellular/viral proteins (Cyclin T1 & Tat
responsible for gene expression and viral replication)
4
5. SELEX
● Basic principle : DNA/RNA act as ligands and that modulates target
protein activity
● Aptamers – most often isolated by a method called “SELEX”
● SELEX – Systematic Evolution of Ligands by Exponential enrichment
5
7. SELEX
Optimization :
● Aptamers undergo chemical modification – to modulates their
pharmacokinetic profile
● 2’ hydroxyl position – target for nuclease; To prevent degradation,
○ Fluoro modification at 2’ position of pyrimidines
○ O-methyl modification at 2’ position of purines
7
8. SELEX
● Mutant T7 RNA polymerase – used to facilitate the RNA
transcription
● Addition of polyethylene glycol & cholesterol – increases half life
● Antidote oligonucleotides – avoids patient’s own clearance
mechanism
8
10. ADVANTAGES
● Easier & more economical to produce aptamers
● Less toxicity & less or no immunogenicity
● Greater specificity & affinity
● More stable & reversibly denatured
● Can be easily modified chemically
● Inactivate proteins without altering genetic material
10
11. DISADVANTAGES
● Aptamer identification is more expensive & labour intensive
● Variable pharmacokinetic properties
● Low affinity to some target proteins
● Unmodified aptamers are highly susceptible to serum degradation
● Short half life
● Smaller size – more prone to renal filtration
11
12. CLINICAL IMPORTANCE
● Pegaptanib :
○ Only FDA approved RNA aptamer (2006)
○ Target is vascular endothelial growth factor (VEGF)
○ Used for age-related macular degeneration of the eye
12
13. CLINICAL IMPORTANCE
● Pegpleranib :
○ DNA aptamer
○ Target is platelet derived
growth factor
○ Under phase II studies
● Avacinaptad pegol :
○ Modified RNA aptamer
○ Under phase II studies
● Nucleolin :
○ DNA aptamer; phase II
○ Cancer cells targeting
13
14. NEWER TARGETS
● Bleeding disorders :
○ Factor IXa
○ Von williebrand factor
○ Thrombin
○ CCL2
○ Complement (C5)
● Cancer diseases :
○ Prostate-Specific Membrane
Antigen (prostate)
○ Human Epidermal Growth
Factor Receptor 2 (Breast)
○ AXL tyrosine kinase receptor
- myeloid leukemia etc. 14
15. APPLICATIONS
● New drug development
● Bio-imaging
● As therapeutic tool
● As diagnostic tool
● As drug delivery system
● Hazard detection
● Food inspection
● Drug discovery
15
16. SUMMARY
● Aptamers - RNA/DNA or Protein oligonucleotide molecules
● Ability to bind to proteins with high affinity and specificity
● Can be prepared using SELEX
● Chemical modification improves pharmacokinetic profile
● Aptamers are poised to successfully compete with monoclonal Abs
in therapeutics and drug development within the next few decades.
16
17. REFERENCES
● Nimjee SM, White RR, Becker RC, Sullenger BA. Aptamers as
therapeutics. Annual review of pharmacology and toxicology. 2017
Jan 6;57:61-79.
● Rusconi CP, Yeh A, Lyerly HK, Lawson JH, Sullenger BA. Blocking the
initiation of coagulation by RNA aptamers to factor VIIa Thromb.
Haemost. 2000; 84:841–48
● Achyut bora and Neelotpal sharma, Concept of aptamer and its
appliction, ppt.
17
