Zika virus wipes out two types of brain tumors in mice

Zika research
At very low concentrations, Zika virus shrank brain tumors in mice without showing a propensity to cause side effects by spreading throughout the body. (NIAID)

The mosquito-borne virus Zika ignited fears around the world more than two years ago due to its link to children born with the brain malformation known as microcephaly. But a handful of cancer researchers see potential in exploiting the Zika virus' ability to infect the brain. Among them is a team at the University of São Paulo in Brazil, which is reporting promising evidence that the virus may be useful in treating two types of childhood brain tumors.

The researchers tested a low concentration of purified Zika virus in mice with medulloblastoma and atypical teratoid rhabdoid tumor (AT/RT): two types of central nervous system tumors that typically occur in children under age 5. The tumors shrank in 20 out of the 29 animals treated, they reported in the journal Cancer Research. They disappeared completely in two mice with medulloblastoma and in five with AT/RT.

In addition to testing the virus in brain tumors, the researchers examined its effects in cells from prostate, breast, and colon tumors. But the virus had no effect on those tumor types. That means the virus specifically targets cancers of the nervous system. What’s more, the new particles of virus that formed in the tumors after infection had defects that prevented them from spreading throughout the body—a key attribute for ensuring safety.

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This is not the first group to report progress studying Zika as a cancer weapon. Last year, researchers from Washington University School of Medicine in St. Louis and the University of California at San Diego reported that the virus slowed the growth of aggressive glioma tumors in mice. It was especially effective when combined with temozolomide, a chemotherapy drug.

RELATED: Merck inks $394M takeover of oncolytic virus play Viralytics

Cancer-killing viruses, known in cancer research as “oncolytic” viruses, are growing in stature in the field of immuno-oncology. The first FDA-approved oncolytic virus, Amgen’s Imlygic derived from herpes, is effective in a small subset of melanoma patients but may prove more useful in combination with other immune-boosting drugs.

Smaller oncolytics players have attracted interest from investors recently. Among them is Australia’s Viralytics, which is developing Cavatak, a drug derived from a common cold virus that’s showing early promise against melanoma and other cancers. In February, Merck paid $394 million to acquire the company.

Meanwhile, researchers in Canada are studying the potential of Maraba virus in treating breast cancer, while a team in the U.K. is looking at reovirus in brain cancer. Both reported promising preclinical data in January.

The next step for the Brazilian team is to develop a way to produce purified Zika in large enough quantities for clinical trials, they said in a statement. They are currently looking for partners to help bring the virus into clinical trials in children.