Engineered virus selectively infects tumours in early trial

In collaboration with the Press Association

In an experimental trial, scientists have shown that an engineered virus can infect and multiply within a patient's tumour without harming the rest of the body.

Although the technique was not shown to affect the growth of the tumours or improve the patient's disease, the researchers suggest that it could be used to target treatments to patient's tumours in the future.

Researchers at the Ottawa Hospital Research Institute and the University of Ottawa - working with researchers from several other organisations - found that, when injected into the bloodstream, the virus infected tumours but not healthy tissue.

The study, published in the journal Nature, is the first to show that a virus can selectively infect and multiply within a tumour after being injected into the bloodstream.

The trial involved 23 patients with very advanced cancer who had not responded to conventional treatment.

Each patient was given an intravenous infusion containing a virus called JX-594, at one of five dose levels.

The virus was genetically engineered to boost its ability to target cancer cells, and a foreign gene was added to the virus to help researchers detect its spread within the body.

Samples taken eight to 10 days after treatment revealed that the virus had spread in the tumours of 87 per cent of patients in the two highest dose groups.

In these patients, the virus and its foreign gene were detected in the tumour but not in healthy tissue throughout the rest of the body.

The most common side effect of the treatment was mild to moderate flu-like symptoms lasting less than one day.

Senior researcher Dr John Bell said: "We are very excited because this is the first time in medical history that a viral therapy has been shown to consistently and selectively replicate in cancer tissue after intravenous infusion in humans.

He also said the study provides preliminary evidence that we can use viruses to deliver foreign genes directly to tumours, opening the door to a "whole new suite of targeted cancer therapies."

"We're still in the early stages of testing these viruses in patients, but I believe that someday, viruses and other biological therapies could truly transform our approach for treating cancer."

Cancer Research UK oncologist Professor Nick Lemoine, director of Barts Cancer Institute, said: "Viruses that multiply in just tumour cells - avoiding healthy cells - are showing real promise as a new biological approach to target hard-to-treat cancers. But up until now they have had to be directly injected into individual tumours to avoid being immediately cleared by the immune system.

"This new study is important because it shows that a virus previously used safely to vaccinate against smallpox in millions of people can now be modified to reach cancers through the bloodstream - even after cancer has spread widely through the patient's body. It is particularly encouraging that responses were seen even in tumours like mesothelioma, a cancer which can be particularly hard to treat."

Copyright Press Association 2011

References

  • Breitbach, C. J. et al. Intravenous delivery of a multi-mechanistic cancer-targeted oncolytic poxvirus in humans. Nature DOI: 10.1038/nature10358