The first instance of a virus-based cancer treatment within the United States was approved by the FDA this week, raising researchers’ hopes that similar cancer-fighting methods will soon follow. The genetically engineered herpes virus known as “T-VEC” is an oncolytic viruses, a group of viruses that cause the body to target cancer cells with an immune response.
Clinical trials of other oncolytic viruses are underway, as Mayo Clinic cancer researcher Stephen Russell described, “The era of the oncolytic virus is probably here. I expect to see a great deal happening over the next few years.”
The fact that some viruses could preferentially infect cancer cells was first noticed in the 1800s when cancer patients who became sick with a viral infection were sometimes known to go into remission. Doctors researched the phenomenon further in the 50s and 60s by testing a variety of viral infections on cancer patients, with mixed results.
Researchers who developed the T-VEC reduced its ability to cause herpes while adding a gene that increases immune system response. Russell described an instance of a patient’s full remission of myeloma using the treatment after two failed instances of stem-cell transplants.
In a large clinical trial of T-VEC that was performed this year by Amgen, patient survival was shown to increase by over four months.
Although T-VEC is the first approved oncolytic virus in the U.S. China approved the world’s first oncolytic virus in 2005, intended to treat head and neck cancers.
Current methods of application require that the T-VEC be directly injected near the site of the cancer, although trials have shown that these treatments were also able to fight cancer that was not located near the injection site. Researchers are now attempting to find a way to administer the therapy generally, for when the cancer site is hard to reach by injection, but this will require that they first prevent the body’s immune system from targeting the T-VEC before it finds the cancer cells.
Oncolytics Biotech is a firm that is investigating potential oncolytic viruses that can evade the body’s immune system as they search for cancer cells. Oncologists may soon be able to choose from a list of oncolytic viruses depending on the cancer to be treated.