Viruses can be used as a form of targeted anti-cancer therapy, and human trials are soon set to start: "Particular parvoviruses normally infect rodents, but they are also infectious for human cells. However, they do not cause any disease symptoms in humans. Most importantly, these viruses have an astonishing property: They kill infected tumors cells without causing any damage to healthy tissue. ... Many different viruses have been tested before in cancer therapy, particularly for treating those types of cancer for which there are no effective established treatment methods. The [researchers] realized early on that parvovirus H-1 has important advantages over other viruses. Now they have been the first to prove that malignant glioblastomas regress completely as a result of treatment with these viruses. ... Parvoviruses pass the blood brain barrier so that they can be administered via the blood stream. In addition, they reproduce in cancer cells, which is particularly important for successful treatment of glioblastoma with its diffuse growth. Thus, the second generation viruses reach and eliminate even those cancer cells that have already settled at some distance from the primary tumor. ... researchers [expect] to be able to admit the first patients to the trial by the end of the year."