`Anti-cancer virus` may help fight tumours

London: Scientists have engineered a virus that can selectively target tumour cells throughout the body when injected into the blood, a breakthrough they say could
one day "truly transform" cancer therapies.

In a small trial on 23 patients, the modified vaccinia virus, which is known for being used to develop a smallpox vaccine, was found attacking only tumours, leaving the healthy
tissue alone, the University of Ottawa researchers said.

Using viruses to attack cancers is not a new concept, but they have needed to be injected directly into tumours in order to evade the immune system. The finding could one day "truly transform" cancer therapies, they said.

Prof John Bell, lead researcher of the study, 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."

"Intravenous delivery is crucial for cancer treatment because it allows us to target tumours throughout the body as opposed to just those that we can directly inject," Prof Bell was quoted as saying by the BBC.

According to the researchers, the virus, named JX-594, is dependent upon a chemical pathway, common in some cancers, in order to replicate.

For their study, published in the journal Nature, the researchers injected the modified virus at different doses into the blood of 23 patients with cancers which had spread to
multiple organs in the body.

In the eight patients receiving the highest dose, seven had the virus replicating in their tumours, but not in healthy tissue.

The virus was found to be able to prevent further tumour growth in six patients for a time, although it didn`t cure the disease. Patients were given only one dose of the virus as the
trial was designed to test the safety of the virus.

It is thought that the virus could be used to deliver treatments directly to cancerous cells in high concentrations.

Noting that the research is still in the very early stages, Prof Bell said: "I believe that some day, viruses and other biological therapies could truly transform our approach
for treating cancer."

Cancer Research UK`s Prof Nick Lemoine 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.

"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."