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Update on research on viral therapy for cancer

February 19, 2016

A number of media stories have recently highlighted research on viral therapy for cancer. These stories helped to educate the Canadian public about important Canadian research. They have also generated a lot of hope and many questions. Answers to some of the most common questions are provided below.

1. Are viral therapies approved to treat cancer patients in Canada?

No, there are no viral therapies approved to treat cancer in Canada. The Unites States recently approved a viral therapy called T-Vec for limited use in melanoma. We don’t know if or when it will become available in Canada.

2. Are viral therapies available for cancer patients through clinical trials in Canada?

Yes, there are a small number of clinical trials of viral therapies for cancer in Canada. It is difficult to keep a current list, but patients can ask their oncologist and also search on websites like www.clinicaltrials.gov, www.canadiancancertrials.ca and www.ontariocancertrials.ca. You can use search terms like “cancer” and “virus” and “Canada”.

It is also important to note that there are many other promising experimental cancer therapies available through clinical trials in Canada. Patients should speak with their oncologist about options.

3. What is the Maraba trial?

The Maraba trial is the world’s first clinical trial of a novel investigational therapy that uses a combination of two viruses to attack and kill cancer cells, and stimulate an anti-cancer immune response. It is being conducted at The Ottawa Hospital, the Juravinski Cancer Centre of Hamilton Health Sciences, Princess Margaret Cancer Centre of the University Health Network in Toronto and the Vancouver Centre of the BC Cancer Agency through the Canadian Cancer Trials Group. As indicated in this media release announcing its launch, the trial will evaluate a combination of two viruses in people with advanced cancer who are not responding to standard therapies.

One of the viruses is a form of Maraba virus that was originally isolated from Brazilian sandflies. The other is a form of adenovirus, which can cause the common cold. The Maraba virus is given into a vein and the adenovirus is injected into a muscle. The approach has not previously been tested in people.

Other details and eligibility criteria are available at https://www.clinicaltrials.gov/ct2/show/NCT02285816.

4. Do we have any results from the Maraba trial?

No, the trial is ongoing and results will not be publicly released until after they have been published in a peer-reviewed journal or presented at a scientific conference.

The story on The National included images of tumours from patients who had participated in past clinical trials with other viruses that were directly injected in the cancer– not patients from the Maraba trial. These past trials have had successes in some patients, but no effect in others. More research is required to understand why some patients respond to viral therapies while others do not.

5. How can I participate in the Maraba trial?

The Maraba trial is very small, with space for up to 79 patients at the four participating hospitals mentioned above. In addition, the eligibility criteria are very narrow, so the vast majority of people with cancer will not be able to participate. Potential trial participants are selected from the pool of patients already being treated at the participating hospitals, so it is not possible to be referred from another region for the trial.

If you are a patient at one of the participating hospitals, you can speak with your oncologist about standard or experimental therapies that may be appropriate for you.

6. How promising is viral therapy for cancer?

Viral therapies have shown great promise in laboratory studies, but we need much more research to know if they will work in humans, and if so, which viruses might be best, how they should be given and in which cancers they might work.

Recent clinical successes with drugs that stimulate the immune system to attack cancer cells (e.g. pembrolizumab, nivolumab, ipilumumab, etc.) have renewed the interest of researchers in looking at other ways to stimulate the immune system. Viruses can stimulate an immune response, and one virus (T-VEC) is now approved in the U.S. for treatment of certain patients with melanoma. There is hope that other viral therapies may eventually be useful to treat cancers.

About The Ottawa Hospital


The Ottawa Hospital is one of Canada’s largest learning and research hospitals with over 1,100 beds, approximately 12,000 staff and an annual budget of over $1.2 billion. Our focus on research and learning helps us develop new and innovative ways to treat patients and improve care. As a multi-campus hospital, affiliated with the University of Ottawa, we deliver specialized care to the Eastern Ontario region, but our techniques and research discoveries are adopted around the world. We engage the community at all levels to support our vision for better patient care.

Media contact


Jennifer Ganton
Director, Communications and Public Relations
Ottawa Hospital Research Institute
Office: 613-798-5555 x 73325
jganton@ohri.ca