What Is Virotherapy?
Virotherapy uses genetically or naturally produced viruses to attack cancer cells. Researchers have always known of the potential to use viruses to confront malignant (cancerous) cells, but for years they didn’t have the technology to test their theory.
Now, virotherapy is a leading treatment used to delay the spread of mesothelioma. In the early 1990s, doctors speculated about the appropriate method and dosage for using virotherapy and tested ways to target cancerous cells specifically without damaging healthy cells. Virotherapy now uses tactics such as oncolytic viruses to do just that. Today’s advancements in virotherapy for mesothelioma preserve healthy cells—the exact outcome doctors are looking for as they expand their understanding of how to effectively treat—and one day cure—patients with mesothelioma.
Oncolytic and Other Types of Viruses
Oncolytic viruses are genetically engineered viruses used in virotherapy to target tumor cells. These viruses can also be reactivated in the immune system to work naturally. Oncolytic viruses produce interferons (proteins that signal cancer cells), which then kill diseased cells. There are several types of viruses now being tested in virotherapy, all of which have produced various results.
The vaccinia virus is a specific form of oncolytic virus that was developed to treat the smallpox epidemic. Using this virus’ core, experts have been able to modify this virus into GL-ONC1, which is part of an ongoing clinical trial being used to test its effects on mesothelioma.
The measles virus has been studied by the Mayo Clinic as a form of oncolytic virus, and was proven as successful treatment for ovarian cancer. Because of its success, doctors have implemented this virus into virotherapy trials for mesothelioma.
The herpes virus has also been modified to attack mesothelioma cells. HSV1717, the newly titled herpes virus, is currently being tested on patients with inoperable pleural mesothelioma.
Unlike two types of viruses for mesothelioma treatment (viruses for gene therapy and immunotherapy), oncolytic virotherapy is not a new idea. However, due to the limited technology available, only animal trials were conducted with very minimal human studies. It wasn’t until recent years that doctors have been able to fully test and study oncolytic viruses and determine their efficiency as a form of virotherapy.
How Does Virotherapy Work?
Virotherapy works by injecting mutated genes into the body. The purpose of the mutated genes, such as those used in gene therapy, is to activate an antitumor response within the immune system. Essentially, this involves the immune system recognizing and killing the pathogens within the cell. The virus then injects itself into malignant tumors where it then replicates itself. The virus then spreads, causing destruction to the cancerous cells (a process labeled oncolysis).
Because of the mesothelioma location in the pleura, administering the virus is relatively simple. Previous issues using Intravenous injection (through the vein), led doctors to primarily use direct intratumor injection. Direct administration of virotherapy treatments into the affected areas ensures more effective treatment. Direct, local administration is recommended because it activates an innate immune system response.
Benefits of Virotherapy for Mesothelioma
Like other new mesothelioma treatments, virotherapy works to target cancer cells specifically, leaving healthy cells unaffected so that the immune system remains intact. The remaining healthy cells then work with the virus to restore the immune system and fight off cancer in the body.
Virotherapy also stimulates the effects of chemotherapy and radiation, which typically hinder healthy cells. Virotherapy acts as a natural defense mechanism—a process needed to attack not only the injected tumor, but the surrounding pathogens as well.
Doctors emphasize three main benefits of virotherapy:
- Directly infects tumor cells and its antitumor efficiency
- Allows for healthy cells to remain intact by only targeting those cells with pathogens
- Preserves and stimulates the immune system, signaling a viral antitumor response to destroy remaining cancerous cells
Virotherapy is also an exemplary treatment to use for patients with advanced or inoperable mesothelioma. Its limited side effects are ideal for patients in these situations. Since virotherapy prevents mesothelioma from spreading, it is one of the limited options that will help prolong the life of patients with advanced-stage mesothelioma.
Current and Ongoing Research Into Virotherapy
Doctors continue to test new viruses to use in virotherapy for mesothelioma. The varying types of diseases that can be modified and issued to patients may eventually be a major break in treating patients with this aggressive type of cancer.
Currently, HSV (herpes simplex virus) and the measles are being evaluated and modified as mesothelioma treatment.They’re currently in their first and second phases of clinical trials. Both viruses are injected intrapleurally (into the chest cavity).
The HSV virus is being tested and evaluated to determine its biological effects and safety profile. Researchers testing the measles virus for mesothelioma cells are currently looking for the best dosage method. They’re also evaluating the safety of the measles virus and if there are any potential side effects. Ongoing clinical trials are paving a pathway to understanding and modifying virotherapy treatment so that doctors can find the most effective mesothelioma treatments.
According to the NCBI (National Center for Biotechnology Information), in a study submitted by the Health Research Institute of the University of Nantes, Paris,
“one can expect that some of these oncolytic viruses will be routinely used to treat clinically challenging malignancies within a few years.”
Virotherapy Side Effects
Virotherapy has been praised as highly tolerable for most patients, limiting the list of side effects. The most severe side effect may include an inflammatory response to the treatment. Doctors at the Department of Molecular Genetics and Microbiology at the University of Florida noted that because virotherapy targets cancerous cells and spares non-cancerous tissues it produces few side effects. They stated,“this cancer cell selectivity should make oncolytic viruses safe and nonpathogenic to patients with minimal or no side effects upon local or systemic administration.”
Some minor side effects of virotherapy may include flu-like symptoms such as fever, chills, nausea, and muscle aches.
Seeking Mesothelioma Treatment With Virotherapy
Virotherapy is an important, emerging mesothelioma treatment with the potential to extend patient survival. With the ability to natively select and eliminate tumor cells, it is one of the most prominent treatments in expanding research for mesothelioma.
Clinical trials are currently testing virotherapy approaches on mesothelioma patients. For more information on emerging mesothelioma treatments, contact our Patient Advocates today.