Herpes virus could be a new way to treat skin cancer

A new treatment for melanoma, a type of skin cancer, is being studied in the United States using a modified herpes virus called HSV-1. Scientists have turned the virus, known for causing cold sores, into a tool to fight tumors.

HSV-1 was not chosen by chance. First, it is a fairly large virus, which allows replacing or adding new genes without much problem to precisely attack cancer cells. Second, HSV-1 does not integrate into the human genome, which eliminates the risk of certain mutations. In addition, herpes is usually not life-threatening and is well treated with antiviral drugs - this makes it safer to use.

The study involved 140 patients with advanced melanoma that had not responded to conventional treatment. They were given a weakened, genetically modified herpes virus RP1 along with the immunotherapy drug nivolumab. The course lasted for up to four months, and those who showed a positive effect continued treatment with nivolumab alone for up to two years.

The results showed that in a third of the participants, the tumors shrank by at least 30%, and in one in six, they disappeared completely. Interestingly, RP1 acted not only at the injection site, but also on other tumors in the body, indicating an enhanced immune response. Side effects were minor - fatigue or cold-like symptoms.

RP1 is also currently being tested for other types of cancer. If proven effective, this approach opens up the possibility of a new class of treatment: viral oncotherapy.

The U.S. Food and Drug Administration (FDA) will decide whether to approve RP1 on July 22, 2025. If approved, the new treatment could be available before large-scale clinical trials are complete.