Aptamer-related technologies represent a revolutionary advancement in the capacity to rapidly\ndevelop new classes of targeting ligands. Structurally distinct RNA and DNA oligonucleotides, aptamers\nmimic small, protein-binding molecules and exhibit high binding affinity and selectivity. Although their\nmolecular weight is relatively smallââ?¬â?approximately one-tenth that of monoclonal antibodiesââ?¬â?their\ncomplex tertiary folded structures create sufficient recognition surface area for tight interaction with\ntarget molecules. Additionally, unlike antibodies, aptamers can be readily chemically synthesized\nand modified. In addition, aptamersââ?¬â?¢ long storage period and low immunogenicity are favorable\nproperties for clinical utility. Due to their flexibility of chemical modification, aptamers are conjugated\nto other chemical entities including chemotherapeutic agents, siRNA, nanoparticles, and solid\nphase surfaces for therapeutic and diagnostic applications. However, as relatively small sized\noligonucleotides, aptamers present several challenges for successful clinical translation. Their short\nplasma half-lives due to nuclease degradation and rapid renal excretion necessitate further structural\nmodification of aptamers for clinical application. Since the US Food and Drug Administration\n(FDA) approval of the first aptamer drug, MacugenÃ?® (pegaptanib), which treats wet-age-related\nmacular degeneration, several aptamer therapeutics for oncology have followed and shown promise\nin pre-clinical models as well as clinical trials. This review discusses the advantages and challenges\nof aptamers and introduces therapeutic aptamers under investigation and in clinical trials for\ncancer treatments.
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