Abstract
Oncolytic viruses infect, replicate in and lyse tumor cells while sparing normal cells. In addition to direct lysis, viruses induce antitumor immunity and some viruses express cytotoxic proteins.
Oncolytic viruses can be divided into three categories: 1) naturally occurring viruses that selectively replicate in tumor cells; 2) virus mutants in which some genes essential for replication in normal cells but unnecessary in cancer cells have been deleted; and 3) virus mutants modified by the introduction of tissue-specific transcriptional elements that drive viral genes. Preclinical studies have shown that reovirus proliferates only in tumor cells with activated genes of the RAS family or its pathway.
Activated RAS or its pathway can be found in 60-80% of human malignancies. Oncolytics Biotech is currently conducting clinical studies with the human reovirus-based cancer therapy Reolysin(R).
Four completed studies in cancer patients demonstrated that intratumoral (including intracranial and intravenous) application of Reolysin(R) is well tolerated.