Rabbit Virus Could be Key to Fighting Brain Cancer

Existing medications and myxoma virus combination shows promise against glioblastoma.

A rabbit virus may be the answer patients with brain cancer are looking for in terms of managing their disease, recent research indicates.

The virus is being developed for cancer therapy, which can be paired with existing therapies to combat deadly brain tumor cells.

The researchers found 6 compounds that make brain tumors more susceptible to treatment with the virus, while findings show that the combination of a drug and the myxoma virus gives better anti-cancer results against glioblastoma, the most common form of brain cancer.

The myxoma virus is found in wild rabbits throughout Australia and Europe and showed some efficacy against cells that cause glioblastoma tumors to recur in humans. Currently, there is no effective long-term treatment for patients with glioblastoma.

The expected life span of a patient with the disease post-diagnosis is 12 to 15 months, according to the National Cancer Institute.

The myxoma virus in combination with the drug rapamycin was already known to be slightly effective in combatting brain tumor-initiating cells, according to Peter Forsyth, MD, the study’s principal investigator. However, there was much room for improvement with the treatment regimen.

So Forsyth teamed up with a group that included Grant McFadden, PhD, a myxoma virus expert, and professor in the UF College of Medicine’s department of molecular genetics and microbiology.

“We want to make a difference with patients. One of the ways we can do that is by repurposing drugs, which holds a lot of promise,” Forsyth said.

The myxoma virus needs help in reaching its maximum potential in the fight again brain cancer, so pairing it with pre-existing medications should allow it to reach that potential.

“Brain tumor-initiating cells are not as susceptible as you would like them to be,” Forsyth said.

Previously, researchers tried the combination of rapamycin with the myxoma virus and found that it gave the virus the boost it needed to be slightly more effective in combatting the disease, according to McFadden.

However, researchers did not know if this was the best course of action to take or if there were better drug-virus combinations that could give the virus a bigger boost in efficacy. That’s when Forsyth got the idea to test the virus against 73 compounds that are in various stages of clinical development.

In performing this test, scientists were surprised to find 3 compounds that had never effectively interacted with a cancer-killing virus in the past actually had the best synergy. The drugs—axitinib, rofecoxib, and premetrexed—when paired with the virus reduced the viability of tumor-initiating cells by 20% or more compared with using just the virus alone.

Axitinib is already approved by the FDA for the treatment of kidney cancer, and was the most effective against a range of cancer cells. It significantly increased cell death when tested on 4 different cell lines, researchers found.

The drug is of particular interest to researchers as it is currently in phase 2 clinical trials for the treatment of tumors known as gliomas, which begin formation in the brain and spine.

The research did not determine the exact mechanics of the virus-drug interaction, but noted that several of the tested compounds target a particular signaling pathway known to promote cancer cell growth and survival.

If the pathway is blocked before the virus is introduced, this may be a crucial step in killing off the cancer cells.

These findings are an important first step in identifying potential drug-virus combinations for various forms of cancer. The next step for researchers, according to McFadden, is to take the most effective compounds and combine them with the virus to study their efficacy in animal models.

“It’s clearly true that viruses will be just one of the elements in the new repertoire of treatments for brain cancer in the future,” McFadden said.