Synthesis and bioactivity of daunomycin-oligonucleotide conjugates as inhibitors of Gene Expression through a triple helix formation

In a previous work we showed that the stability of a triple helix can be markedly enhanced by the conjugation of an anthracycline moiety to the TFO, provided that the correct orientation of the anthracycline be obtained. To this end, the TFO was bound thorugh a hexamethylene spacer to the 4-OH of the carminomycin molecule. The general synthetic scheme involves conversion of daunomycin to a alkylaitng intermediate that is allowed to react with the appropriate oligonucleotide bearing a thiophosphate rsidue at one end. Using this methodology we have prepared oligonucleotide conjugates targeted to polypurine regions in different gene targets, such as mdr-1, HIV, and c-myc. Binding of the anthracycline moiety of the TFO's significantly increases triple helix stability, that reaches values compatible with an interaction of the oligonucleotide conjugates with the corresponding polypurine sequences in biological systems. In particular, anti c-myc conjugates were able to selectively inhibit the transcription of c-myc genes both in a cell-free system and in cells. These results encourage further development of this approach for the discovery of novel anti-gene pharmacological agents.