Antiviral and anticancer ribozymes.

Molecular biologists are beginning to apply the site-specific RNase properties of ribozymes to gene therapy for HIV infection and cancer. Requirements for substrate recognition and cleavage are being finely mapped. Methods of augmenting intracellular cleavage and of dissecting observed discrepancies between in vitro and cellular activity are being explored. Antiviral efficacy against HIV type 1 has been seen in tissue culture for both hammerhead and hairpin ribozymes, and a phase I clinical trial for ex vivo T-cell gene therapy is planned. Oncogene transcripts, such as the bcr/abl fusion messenger RNA and ras, have also been targeted with ribozymes.