After hearing news about an exciting new treatment for incurable cancer using the measles virus, I couldn’t help but wonder whether it could potentially save the life of a young family member with end-stage leukemia. Other cancer patients and their loved ones are likely pondering the same question.
Mayo Clinic researchers published a report on Thursday detailing the first successful treatment of cancer using a genetically engineered measles virus administered at high doses. Two women with multiple myeloma — a rare cancer of white blood cells found in the bone marrow — were treated with a high dose of the virus, from a strain used in vaccines, after their cancers failed to respond to traditional treatments.
One patient, a 65-year-old woman, had some tumor shrinkage from the treatment without a full remission of her cancer while the other, a 49-year-old woman, experienced dramatic benefits: She had a complete remission of her multiple tumors and remained cancer-free for nine months. Now 11 months after the treatment, she is doing well after a malignancy that returned on her forehead was successfully treated with radiation.
I asked Dr. Stephen Russell, a Mayo Clinic hematologist and co-developer of the therapy, to discuss what these promising results mean for other patients. Here are edited excerpts from the interview.
Where do you go from here?
We’re planning a trial with 20 patients that will begin in September. We can only give the measles virus to those without any measles antibodies in their blood so the antibodies won’t destroy the virus before it reaches cancer cells. In the general population, about 95 percent of people have antibodies because they were vaccinated or exposed to the wild virus. Multiple myeloma patients tend to have lower levels of antibodies due to their cancer; about one-third of them have no antibodies, making them eligible for this treatment.
Does this mean patients with other cancers won’t ever benefit from measles virus treatments?
We’re working on ways to use cells to carry the virus directly to the tumor site. Cells would protect the virus from being attacked by antibodies. We have other methods we’re testing as well, including one that involves plasma exchange. These approaches are effective in mice but we need to get them to work in humans.
What are the side effects from the treatment?
Both women had fever, low blood pressure, and a racing heartbeat. Vomiting and headaches can also occur. Side effects usually go away after a few days.
Is using a virus to treat cancer — which is also a virus — a new concept?
Scientists have been thinking about it since a case was reported in the 1970s of a boy in Uganda whose lymphoma regressed after he developed measles. The cancer came back four months later, but it got the medical community thinking about how to use viruses to infiltrate a cancer cell and kill it.
We chose measles to study because it naturally infects blood cells and is already out there in the population, so we know the worst it can do. The kind we use is a vaccine strain, so it’s not contagious. But we have to give a massive dose, so we’re not using this as a vaccine.
Other cancer centers are studying therapies using different viruses. We now know this can work, but the dose of the virus needs to be high, much higher than what we thought previously.
What’s the biggest challenge that could keep this from becoming a breakthrough treatment?
It’s really quite challenging to make the amount of virus we need. The viruses are hard to grow in lab cells. That’s why we have to wait until September to begin our next trial; it takes time for the virus to replicate on cells in order to have a high enough dose, at a good enough quality to meet the requirements of the Food and Drug Administration.
We still have room to push the dose higher than we used previously — if we can make enough of the virus — while staying within our safety range, so we may be able to improve the effectiveness. The side effects we’ve seen so far have been mild and temporary.
What happens if cancer learns to outsmart the measles virus like it does with chemotherapies?
If we can’t get long-term effectiveness from one virus, like measles, we may have to explore sequential treatments where patients first get a measles treatment and then get treated with another virus later on if their cancer recurs.
Each virus can only be used once since the body will develop antibodies to it.