Currently, a few clinical trials are under way to assess the efficacy and toxicity of HSV-TK/VCV gene therapy in combination with radiotherapy in recurrent glioblastoma multiforme or anaplastic astrocytoma (NCT03596086) and the efficacy and toxicity of HSV-TK/VCV gene therapy in combination with androgen deprivation therapy, brachytherapy, external beam radiotherapy, and prostatectomy in previously untreated high-risk prostate cancer (NCT03541928). The gene discussed is TKT; the disease is glioblastoma.