A theoretical approach to select effective antisense oligodeoxyribonucleotides at high statistical probability

Up to now, out of approximately 20 antisense oligodeoxyribonucleotides (asO DN) selected and tested against a given target gene, only one species shows substantial suppression of target gene expression. In part, this seems to be related to the general assumption that the structures of local target se quences or antisense nucleic acids are unfavorable for efficient annealing. Experimental approaches to find effective asODN are extremely expensive wh en including a large number of antisense species and when considering their moderate success. Here, we make use of a systematic alignment of computer- predicted secondary structures of local sequence stretches of the target RN A and of semi-empirical rules to identify favorable local target sequences and, hence, to design more effective asODN. The intercellular adhesion mole cule 1 (ICAM-1) gene was chosen as a target because it had been shown earli er to be sensitive to antisense-mediated gene suppression. By applying the protocol described here, 10 ICAM-1-directed asODN species were found that s howed substantially improved inhibition of target gene expression in the en dothelial cell line ECV304 when compared with the most effective published asODN. Further, 17 out of 34 antisense species (50%) selected on the theore tical basis described here showed significant (>50%) inhibition of ICAM-1 e xpression in mammalian cells.