Research shows that an experimental viral treatment might prolong the lives of patients with near-untreatable brain cancer.
In the experimental treatment, which is in Phase 1, patients with recurrent glioblastoma – the most common and aggressive form of brain tumor – were injected with an engineered virus that was then combined with an antifungal drug to kill infected cancer cells. The results showed that the survival rate among 43 patients injected was 13.6 months, compared to 7.1 months for patients who did not receive injections. Some patients who received the experimental treatment lived for more than two years with few side effects, the study noted.
Dr. Timothy Cloughesy, co-lead on the study and director of the neuro-oncology program at the University of California, Los Angeles, says, “For the first time, this clinical data shows that this treatment, used in combination with an antifungal drug, kills cancer cells and appears to activate the immune system against them while sparing healthy cells.”
This approach also has potential in additional types of the disease, such as metastatic colorectal and breast cancers.
Cloughesy is a consultant for Tocagen, the biopharmaceutical company that developed the treatment and funded most of the research.
Dr. Michael Vogelbaum, co-lead on the study and associate director of the brain tumor neuro-oncology center at the Cleveland Clinic, says, “Brain cancer is a deadly disease, and when it returns there are extremely few treatment options, and survival is usually measured in months.”
The treatment works by using the injectable Toca 511 treatment to infect actively dividing cancer cells and deliver a gene for an enzyme called cytosine deaminase to these cells. Inside the tumor, Toca 511 then programs the cancer cells to make cytosine deaminase in order to get them ready for the second part of the treatment.
The patient then takes the antifungal drug Toca FC, which relies on the changes created by Toca 511 to convert Toca FC into the anti-cancer drug 5-fluorouracil (5-FU). This targets infected cancer cells and cells that hide the tumors from the immune system, killing them while leaving healthy cells alone.
According to the press release from the research team, these are the first published clinical trial results of this new type of virus called a retroviral replicating vector (RRV).
Phase 1 studies are to assess a treatment’s safety and tolerability. A medication needs to pass three phases before it gets approved by the US Food and Administration.
Vogelbaum says, “The collective results from this virus study, include encouraging survival and excellent safety data, support the ongoing randomized phase 2/3 trial called Toca 5, and offer hope for a new treatment option for patients with brain cancer.”
The study was published in the journal Science Translational Medicine.