Replication-competent, nonneuroinvasive genetically engineered herpes virus is highly effective in the treatment of therapy-resistant experimental human tumors.

A genetically engineered, nonneurotropic herpes simplex virus (R7020) with a proven safety profile in both animals and humans was found effective in the treatment of large xenotransplanted tumors arising from a radiation- and chemotherapy-resistant human epidermoid carcinoma and a hormone-refractory prostate adenocarcinoma. R7020 replicated to high titer and caused rapid regression of the human tumor xenografts. Tumor destruction was accelerated in animals given both R7020 and fractionated ionizing radiation.