*3.1. G47*∆

G47∆ was first described by Todo et al. in 2001: It is based on the G207 virus and contains an additional deletion in the region of the ICP47 gene, which eventually mitigates enhanced expression of MHC I on virus-infected cells [46]. Preclinical evaluation indeed showed positive effects on MHC I expression, T-cell stimulation of melanoma cells as well as increased cytolytic potency in melanoma and glioblastoma cell lines in vitro and survival in a immunocompetent neuroblastoma model in vivo [46]. Promising results with this agent have also been obtained for the treatment of breast cancer cell lines [47]. G47∆ has been tested for safety and efficacy in patients with recurrent or progressive glioblastoma (UMIN000002661) and castration resistant prostate cancer (UMIN000010463) in Japan. An interim analysis of the phase 2 glioblastoma study in 2019 presented with encouraging data, i.e., a one-year-survival rate of 92.3% compared to control (15%) [48]. Currently, this agent is also being tested in recurrent olfactory neuroblastoma (UMIN000011636) and malignant pleural mesothelioma (UMIN000034063).
