by Matthew Hilburn– A new study has, for the first time, demonstrated that a specific kind of virotherapy can infect and kill cancer in humans, leaving healthy cells unharmed.
The study, conducted by the Mayo Clinic in Minnesota, involved just two patients, both of whom received a “single intravenous dose of an engineered measles virus (MV-NIS) that is selectively toxic to myeloma plasma cells,” researchers said.
Multiple myeloma affects the plasma cells in the bone marrow and causes skeletal or soft tissue tumors. It is rarely cured.
The therapy brought about a complete remission in one of the patients, while only improving the second patient.
“This is the first study to establish the feasibility of systemic oncolytic virotherapy for disseminated cancer,” said Dr. Stephen Russell, a Mayo Clinic hematologist, and first author of the paper and co-developer of the therapy in a statement. “These patients were not responsive to other therapies and had experienced several recurrences of their disease.”
In an interview with VOA, Russell called viruses “the last untapped bioresource as destructive bioagents against cancer.”
The two patients in the trial were given enough measles virus to vaccinate 100 million people. In a video about the treatment, Mayo doctors say the modified measles virus makes cancer cells join together and “essentially explode.”
The therapy also may boost the patient’s immune system, allowing it to “mop up” any remaining cancer, they said.
Using re-engineered viruses to fight cancer, also known as oncolytic virotherapy, is nothing new, dating back to the 1950s, according to the Mayo Clinic. But, according to researches, this study provides the “first well documented case of a patient with disseminated cancer having a complete remission at all disease sites after virus administration.”
Good results with this kind of therapy have been seen with rodents, but this is the first time success has been reported in a human being. However, remission was only achieved in one of the two patients.
Mixed results for patients
The other patient did not respond as well. Nonetheless, by using a sophisticated imaging technique, doctors were able to tell that the virus had targeted cancerous cells.
Russell said he and his colleagues found the difference in reaction between the two patients “puzzling,” but had some theories about why.
He said the patient who’d gone into remission had less myeloma in her body and that the second patient’s cancer was in a “very advanced state” with “massive tumors in the legs and abdomen.”
Another theory was that the second patient had more tumors in the muscles.
“If we’d treated her earlier, we’d have done better, Russell said, adding that they might also have seen better results at a higher dose.
There were negative side effects, he said, such as severe flu-like symptoms almost immediately upon dosing. Despite that, one patient called the side effects “trivial,” compared to other treatments they’d received, according to Russell.
William Phelps, Director of the Preclinical and Translational Cancer Research Program at the American Cancer Society, said the study is exciting because it shows efficacy with humans.
“Viruses are very good at disseminating throughout the body,” he said, adding that they’re also adept at hunting, detecting and infecting metastatic tumors.
Another advantage of using viruses is that they’re mutable, said Phelps.
“We can make a lot of changes to change what cells they infect,” he said. “We can change their payloads to specifically kill cancer.”
According to an editorial accompanying the paper, Dr. John C. Bell of the Centre for Innovative Cancer Research in Ottawa, Canada, described the findings as a “benchmark to strive for and improve upon.”
When asked if the study had implications for other types of cancer, Russell answered with an emphatic yes.
“There’s no real reason why it can’t work on other cancers,” said Bell, adding that cancer provides the “perfect substrate” for viruses because they’re metabolically active, fast growing and, “don’t know how to turn off.
“Once the virus gets in there, it can just move,” he said. “There are a lot of reasons they’re happier growing in cancer.”
More trials are planned.
“We want to take this virus and test it much more efficiently in a larger group to determine how often it works,” said Russell.
According to the Mayo Clinic, more of the MV-NIS therapy is being manufactured for a larger, phase 2 clinical trial later this year.
Phelps said his one concern about the study was that the two patients did not have any antibodies for measles, making them very rare because most people have been vaccinated against or had the measles.
One possible next step is “trying to engineer the virus so that it wouldn’t be neutralized by your antibodies,” said Phelps. “Intuitively, you should be able to do that.”
Russell believes that what this study has proved is valuable and can be built upon.
“We recently have begun to think about the idea of a single shot cure for cancer, and that’s our goal with this therapy,” he said.
The findings appear in the peer-reviewed journal Mayo Clinic Proceedings