Virotherapy for Mesothelioma

Unlocking the Potential of Viruses

As far back as the early 20th century, doctors understood the cancer-fighting potential of viruses. However, because scientists hadn’t developed technology to harness the power of viruses safely, they relied upon other approaches to battling cancer —mainly, chemotherapy and surgery.

Viruses used in cancer treatment are modified by removing the part of the genetic material in the virus that is necessary for it to spread. This modification makes it safe for patients. The virus, however, doesn’t lose the ability to infect mesothelioma cells.

This genetic modification also makes targeted therapy possible. Healthy cells are left unharmed by targeting mesothelioma cells, which means fewer side effects for patients. The destruction of healthy cells is usually responsible for treatment-related side effects such as nausea and fatigue.

Three types of virotherapy are available:

• 1
  Oncolytic Viruses — These types of modified viruses directly kill cancer cells and may also stimulate the immune system to fight back. Oncolytic viruses have shown serious potential for fighting mesothelioma.
• 2
  Viral Vectors for Gene Therapy — Gene therapy involves reprogramming the genetic material in cancerous cells so they die off. Viral vectors are modified viruses that deliver genetic material to cells.
• 3
  Viral Immunotherapy — Immunotherapy uses the immune system to kill mesothelioma cells. Viral immunotherapy activates the immune system with the help of modified viruses.

Oncolytic Viruses

Oncolytic viruses make up the majority of virotherapy options for mesothelioma patients. These viruses are useful because they directly infect mesothelioma cells rather than stimulating a separate biological response to attack the cells.

Vaccinia Virus and Mesothelioma

Smallpox, once one of the world’s most terrible epidemics, was stopped with a vaccine developed with a virus known as vaccinia. Researchers have since modified this virus to help tackle mesothelioma. The modified virus, GL-ONC1, is part of a clinical trial taking place at Memorial Sloan-Kettering.

Measles and Mesothelioma

Researchers at the Mayo Clinic began studying the use of the measles virus for cancer treatment in 1998. After seven years, MV-NIS was developed and tested in patients with ovarian cancer. These trials were a success, and the drug has since been tested in the treatment of other cancers, including mesothelioma. One patient with multiple myeloma even experienced complete remission with MV-NIS. Clinical trials for use of this drug in mesothelioma patients are still underway.

Herpes Simplex and Mesothelioma

Herpes simplex is the virus responsible for causing cold sores. Doctors in the United Kingdom have modified it to attack mesothelioma cells. The resulting drug, HSV1716, is being used for patients with inoperable mesothelioma.

Virotherapy, Immunotherapy and Gene Therapy: The Common Link

Virotherapy has a complex relationship with immunotherapy and gene therapy. Viruses have an effect on both the immune system and the genetic material within cells. This means virotherapy can either cause an immune response, corrupt genetic material within cells, or do both in fighting mesothelioma.

Viral Immunotherapy

Crossing both the realms of virotherapy and immunotherapy are the cancer vaccines that use modified bacteria or viruses to stimulate the immune system to attack mesothelioma cells. We call this viral immunotherapy.

An example of a recent viral immunotherapy is Trovax. This drug is developed from the vaccinia virus, much like GL-ONC1, but the difference lies in how they initiate the immune system. Trovax has been modified specifically to induce an immune system response, whereas GL-ONC1 is modified to infect mesothelioma cells directly.

The immune system is trained to search for and eliminate virally infected cells. The immune system destroys the cancerous cells that become infected with a drug such as Trovax. This is an important and helpful development as the immune system on its own has a hard time recognizing mesothelioma cells.

Virotherapy Clinical Trials

Clinical trials are the only way for mesothelioma patients to take advantage of innovative treatments like virotherapy. Several trials are testing promising virotherapy treatments, such as the measles virus (MV-NIS) and the vaccinia virus (GL-ONC1).

Patients with mesothelioma may want to consider a virotherapy clinical trial if:

• Their mesothelioma has reached an advanced stage.
• Their tumors are inoperable.
• They haven’t responded well to chemotherapy or radiation.

Mesothelioma is a rare form of cancer with limited treatment options available. This makes clinical trials an important tool in the fight to control this disease. If you are ready to take control of your prognosis, we can help you connect with a virotherapy clinical trial.

Common Questions About Virotherapy for Mesothelioma

How does virotherapy work for mesothelioma?

Virotherapy inserts viruses into the tumor site to disrupt cancer cells from growing. The virotherapy drug either attacks tumors or escalates the immune system’s ability to fight cancer by activating the T-cells and other cancer-fighting mechanisms to recognize mesothelioma tumors.

What are the types of virotherapy?

There are three main types of virotherapy used for mesothelioma where a virus is used as a vector to put a therapeutic agent into the body:

• Oncolytic virus, which directly kills cancer cells.
• Virotherapy with gene therapy, which transfers a gene therapy drug into the tumor site and reprograms cancer cells to die.
• Viral immunotherapy, which stimulates the immune system by putting an unwanted virus in the body.

Does virotherapy improve survival for mesothelioma patients?

Virotherapy is featured in quite a few clinical trials, but more research is needed before declaring any objective survival benefit for mesothelioma patients. ONCOS-102, for instance, is an oncolytic adenovirus that activates the immune system. In the latest study, requiring further investigation, ONCOS-102 plus chemotherapy improved mesothelioma survival by six months.