Biodrugs 2004; 18 (6): 351-359

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 1. Aptamers and Target Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 2. Aptamers as Detection Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 3. Therapeutic Aptamers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 4. Drug Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 Aptamers are short single-stranded oligonucleotides that fold into well defined three-dimensional shapes Abstract allowing them to bind to and inhibit their targets with high affinity and specificity. Aptamers can be considered truly multifunctional tools, because they can be generated rapidly and applied for specific detection, inhibition, and characterization of proteins. Recent publications impressively confirm that aptamers can be used either as surrogate inhibitors for the identification of small molecule lead compounds or as biopharmaceuticals. Aptamers represent a novel class of ligands that optimally fit 1. Aptamers and Target Validation different requirements. As short single-stranded oligonucleotides A key step in drug discovery is determining the biological they fold into well defined three-dimensional conformations caparelevance of a given protein for a particular disease. Researchers ble of binding their targets with high affinity and specificity have developed manifold technologies to face this challenge in the past decades. The validation of genes and their encoded proteins through complementary shape interactions. Since the discovery of can be accomplished by interfering either directly at the protein aptamers in the early 1990s[1,2] we have seen their use as pharmalevel (e.g. with small molecules, antibodies, or aptamers), or the ceutical leads, detection reagents, and functional proteomic mRNA level (e.g. with ribozymes, antisense oligonucleotides, or tools.[3,4] Aptamers have proved to inhibit the function of their RNA interference), or alternately by knocking out the respective targets in many cases in vitro, in cell culture, or in living anigene in animals (figure 1). mals.[5,6] Since functional knockdown studies are the The conventional gene knock-out strategy is an established method allowing the characterization of a particular gene in living best-described application in the literature, we will discuss the use organisms.[9] However, the protocols are laborious and time conof aptamers for analyzing protein function compared with other suming and interpretation of gene knock-out data is often difficult technologies. Such aptamers have often provided the starting point because of ontological and pleiotropic effects. Alternative methfor further developments into therapeutics or as molecular biology ods are provided by antisense oligonucleotides[10] and tools, as confirmed by the growing number of publications coverribozymes[11] that bind to the mRNA sequence of the encoded ing the use of aptamers in target validation, diagnostics, therapy, target protein and subsequently inhibit translation either by mRNA and drug discovery.[7,8] degradation or by blocking ribosome scanning. The third, and