Oncolytic Viruses Move Forward in Clinical Trials

A specially engineered strain of measles virus produced promising, albeit preliminary, results in patients with recurrent ovarian cancer in a phase I trial reported by researchers at the Mayo Clinic in Rochester, Minn. The measles virus, one of few oncolytic viruses currently in clinical trials, putatively works by selectively entering cancer cells, altering their gene expression, and causing them to fuse with neighboring cells, which leads to apoptosis. In the trial, physicians treated 21 patients via intraperitoneal administration with a measles virus altered to express carcinoembryonic antigen, a marker protein that can allow real-time monitoring of viral gene expression. The median survival of the patients was 12.15 months, which appeared to be about double the expectation based on historical control subjects, according to the Mayo researchers, writing in the February Cancer Research . They observed no dose-limiting toxic effects. Researchers hope that the first oncolytic virus cancer treatment could be approved in the U.S. in the next few years. Ever since safety trials allayed initial apprehensions about using viruses, researchers have been seeking a viral treatment that offers both selectivity for cancer cells and potency in killing them. The oncolytic virus farthest along so far is a modified herpesvirus now being tested in a phase III trial for patients with stage III or IV melanoma. Two other viruses are in phase II trials ( seesidebar ), and others, such as the measles virus, are in preclinical and early clinical studies.