The synthesis of novel phosphate diester prodrugs of combretastatin A4; DNA cleavage with a metal ion-iminodiacetic acid linked deoxyoligonucleotide system or by photoreaction with 4-amino-1,8-naphthalimides

We have incorporated iminodiacetic acid groups via modified phosphoramidite esters of iminodiacetic acid thymidine into DNA oligonucleotides (oligos) in an effort to achieve sequence selective DNA cleavage. These systems resemble the Fe2+-EDTA tethered oligonucleotide cleavage systems developed by Dervan and others, where the sequence selectivity of the system is based upon complementary base pair recognition of the Fe2+-EDTA-linked oligo with a target DNA or RNA sequence. In our system, instead of a metal ion chelating EDTA ligand attached to an oligonucleotide, an EDTA-like ligand is formed in situ by the assembly of two (a 5 ′- and a 3′-) iminodiacetic acid linked oligos to the target sequence by adjacent complementary base pairing. This system should position metal ions by chelation in such a way that they cause either the hydrolytic or oxidative cleavage of the target strand with very sensitive sequence selectivity. Such modified ODNs have the potential to function as artificial restriction enzymes as well as agents for the targeted scission of DNA and RNA in antiviral and gene therapy.; We have also been involved in the synthesis of novel phosphate diester prodrugs of the vascular targeting agent (VTA) combretastatin A4 disodium phosphate (CA4DP), a water soluble prodrug of the antitumor antimitotic agent combretastatin A4 (CA4). CA4DP is a promising VTA agent that is currently in Phase II clinical trials by Oxigene, Inc., but has also shown a limited plasma half-life of only 30 minutes. We synthesized several phosphate diesters of CA4 with the hope that they would be effective prodrugs of CA4 with longer plasma lifetimes than CA4DP. The diesters synthesized were tested in an initial vascular targeting assay, with promising results. One of our compounds was even more effective at vascular shutdown than CA4DP.; Finally, we have also performed preliminary evaluations of the efficiency of DNA photocleavage by a variety of 4-amino-1,8-naphthalimide dyes, which may have applications in photodynamic therapy (PDT) and as potential DNA photonuclease agents. We also performed studies aimed at clarifying the mode of interaction and photocleavage of these dyes with DNA.