Aptamers: a new class of oligonucleotides in the drug discovery pipeline?

Aptamers are oligonucleotides identified in a randomly synthesized library containing up to 10(15) different molecules that fold into defined three-dimensional structures. Following their selection for predetermined properties at the end of an iterative process known as SELEX (Systematic Evolution of Ligands by Exponential enrichment) they can be chemically modified in order to provide them with additional properties. These molecules display both high affinity and specificity for their target. Aptamers constitute promising molecules for therapeutic applications as exemplified by pegaptanib, an aptamer-derived anti-VEGF compound shown to be effective in treating age-related macular degeneration.