Herpes virus could soon be approved to treat severe skin cancer

A cancer-killing virus could soon be approved for use after shrinking tumours in a third of people with late-stage melanoma

By Michael Le Page

8 July 2025

Melanoma is a type of skin cancer that can spread elsewhere in the body

ARTUR PLAWGO/Getty Images/Science Photo Library

Despite many decades of effort and numerous human trials, only one virus that is designed to kill cancers has ever been approved by regulators in the US and Europe. But a second could get the green light at the end of the month, after getting good results for treating melanoma, a particularly serious type of skin cancer.

A genetically modified herpes virus, called RP1, was injected into the tumours of 140 people with advanced melanoma for whom standard treatments had failed. The participants also took a drug called nivolumab, which is designed to boost the immune response to tumours.

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In 30 per cent of those treated, tumours shrank, including those that were not injected. In half of these cases, the tumours disappeared altogether.

“Half the responders had complete responses, meaning the complete disappearance of all tumours,” says Gino Kim In at the University of Southern California. “We’re very excited about these results.” The other options for treating people at this stage don’t work as well and have more serious side effects, he says.

A later-stage trial that will involve 400 people is now under way, but RP1 could be approved by the Food and Drug Administration (FDA) in the US for treating advanced melanoma in combination with nivolumab long before this trial finishes, In told New Scientist. “The FDA is supposed to give us a decision at the end of this month.”