Cancer trial world’s first to deploy two viruses

Researchers have launched a clinical trial that seeks to use the combined power of two viruses to trigger a sustained assault on the cancer cells of patients with advanced tumours.

The clinical trial, which will be led by The Ottawa Hospital, is the first in the world to deploy two viruses at the same time in a biological siege of cancer cells.

If the trial duplicates the results that researchers have seen in mice and other lab models, it holds “profound implications” for the treatment of cancer, said Dr. David Stojdl, a senior scientist at the Children’s Hospital of Eastern Ontario and one of the researchers who developed the novel therapy.

“The potential is staggering.”

The clinical trial will use modified versions of the Maraba virus — first isolated from Brazilian sandflies — in combination with the Adenovirus, derived from the common cold virus.

“By using two types of viruses, or multiple types of biological agents, you’re really attacking the cancer in multiple ways at the same time,” said Dr. John Bell, a senior scientist at The Ottawa Hospital and another of the researchers involved in the project.

“It doesn’t give cancer cells a chance to escape and so the chances of success are much higher.”

Viruses are ancient, highly-evolved infectious agents that can take over and destroy cells. For more than a century, scientists have sought to harness that power in the fight against hardtocancer cells, which can replicate wildly, but are strangely vulnerable to infection.

“We all know that cancer hides,” said Stojdl. “It hides among our normal, healthy cells. It hides from our immune response.”

The Maraba virus, genetically modified in Ottawa laboratories, has the ability to sense the difference between tumour cells and normal ones, then attack the cancer with the help of the body’s own immune system.

Hospitals in Ottawa, Toronto, Hamilton, Ont., and Vancouver are taking part in the trial, which is being funded by the Ontario Institute for Cancer Research.

Stojdl, Bell and another researcher involved in the project, Dr. Brian Lichty, began investigating cancer-fighting viruses when they worked together at The Ottawa Hospital 15 years ago. The clinical trial, unveiled Friday, is the culmination of their enduring collaboration.

The trial is scheduled to run until November 2017 and will enrol up to 79 patients whose cancerous tumours have resisted conventional treatment. Some of the patients will receive one of the viruses, but most will receive both in doses administered two weeks apart.

It will take up to a year after the end of the trial for the researchers to analyze all of their data and publish their findings.

Adult patients are now being sought for participation in the clinical trial, which will concentrate on people with solid tumours. Researchers also want to find patients whose cancer cells express a specific protein, MAGE-A3, which makes them vulnerable to the engineered viruses. More than 30 per cent of cancerous tumours express the protein.

“I’m very excited about this trial because I think it represents in many ways the future of cancer therapy,” said Lichty, associate professor at McMaster University. “I think in five or 10 years there will be more and more cancer immunotherapies coming on board as we learn how to engage the patient’s own immune system to attack and fight cancer.”