Several lanthanide(III) derivatives of texaphyrin are being developed as agents for magnetic resonance imaging, photodynamic therapy and as radio-sensitizers. The investigator has discovered that some lanthanide(III)texa-phyrins act as unique agents for effecting site specific hydrolysis of RNA. The objectives of the Phase I application are to improve the synthesis to give large amounts of lanthanide(III)texaphyrin- oligonucleotide analogue conjugates for in vitro studies. DNA will be synthesized and modified with the commercial aminohexyl- amidite at the 5'-end of the silica-attached polymer. The MMT group protecting the amine is removed on the support and the amide-forming coupling reaction carried out to give column-bound conjugate. The ribozyme analogue is released and deprotected with ammonia to afford 5'-aminohexyl-linked DyTx-DNA conjugate. In case this method fails, a phoshoramidite derivative of DyTX will be prepared and coupled as the last "monomer" in the automated synthesis. The DyTx OH groups will be protected as esters and deprotected by treatment with ammonia. This ribozyme analogue will differ from the earlier preparation in its structure having no amide bonds in the linker. Methods will have to be developed for the large scale purification of the ribozyme analogues by HPLC followed by dialysis or ion exchange chromatography. The second part of the application seeks to test the efficiency at which RNA hydrolysis is carried out by the agent in the presence of competing secondary and higher order structure or competing proteins. Hybridization and cleavage studies will be taken up on synthetic RNA substrate of about 30-40 base length. Cleavage fragments generated by the ribozyme analogue will be assayed by electrophoresis and quantitated by densitometry. The synthesized ribozyme analogues will be directed against c-myc oncogene in cell culture to evaluate the in vitro efficacy. Biodistribution, pharmacokinetics, activity and safety are planned in the Phase II study.National Cancer Institute (NCI)
