British researchers injected reovirus into the bloodstreams of 10 patients with bowel cancer that had spread to the liver and found the virus set up deadly "reproduction factories" in the tumors but not in healthy tissue.
"It seems that reovirus is even cleverer than we had thought," study author Dr. Alan Melcher, professor of clinical oncology and biotherapy at Leeds University in the U.K. said in a statement. "By piggybacking on blood cells, the virus is managing to hide from the body's natural immune response and reach its target intact. This could be hugely significant for the uptake of viral therapies like this in clinical practice."
The findings, published today in the journal Science Translational Medicine, suggest cancer-killing viruses can target hard-to-treat tumors after being injected into the bloodstream like standard chemotherapies.
"It would have been a significant barrier to their widespread use if they could only have been injected into the tumor, but the finding that they can hitch a ride on blood cells will potentially make them relevant to a broad range of cancers," study co-author Dr. Kevin Harrington of the Institute of Cancer Research said in a statement. "We also confirmed that reovirus was specifically targeting cancer cells and leaving normal cells alone, which we hope should mean fewer side-effects for patients."
Other viral cancer therapies, some of which require direct injection into tumors, are currently in phase 3 testing. But this is the first time reovirus has been shown to safely and effectively home in on tumors through the blood.
In an accompanying editorial, John Bell of the Ottawa Hospital Research Institute in Canada said the study provides an "important proof-of-concept" for intravenous viral cancer therapies.
"The authors and, more importantly, the patients who participated in this trial have made crucial contributions to the translation of [oncolytic virus]-based therapies," he wrote.