Small oligonucleotides have been used for several years to regulate gene expression by RNaseH-dependent RNA degradation (11) , blocking translation (12) , or re-directing splicing (13) . More recently, microRNAs (miRNAs) (14) and small interfering RNAs (siRNAs) have appeared on the scene of post-transcriptional gene regulation (15) . siRNAs may be effective in treatment of chronic hepatitis-B virus infection (16) , HIV infection (17) , cancer (18) and age-related macular degeneration (19) . Very few antisense oligonucleotides, for example against the bcl-2 oncogene have reached the stage of clinical trials (20) or have actually been approved by the FDA, for instance for the treatment of human cytomegalovirus retinitis (21) .