The world's first virus therapy drug targeting malignant brain tumors won approval in Japan in June 2021. It contains a virus that kills only cancer cells. It was known since the 1970s that tumors shrank after patients were infected with a virus, but nobody was able to develop a cancer drug for many years. Many years later, a US neurosurgeon paved the way for the creation of such a drug for brain tumors, and a Japanese neurosurgeon who saw his paper made further adjustments.