Oncolytic Virus Therapies in Malignant Gliomas: Advances and Clinical Trials

The overall survival rate of brain malignancies such as glioblastoma is currently a little under two years, at most, and treatment options for malignant brain tumors have demonstrated limited efficacy. The current standard of care to treat brain cancer includes surgical resection, radiation, and chemotherapy. Historically, an observed interaction between malignancies and concurrent viral infection has shown therapeutic potential that can perhaps be better leveraged in brain cancer with the technological advances that we have today. We aim to discuss a variety of viral vector designs to harness their oncolytic potential and explore how some of these ideas have performed in clinical trials. In our review, three major viral candidates that have gained traction in this field of research—Herpes simplex virus-1, adenovirus, and poliovirus—are highlighted. How the field has manipulated aspects of their virology and combined these viral platforms with other immune modulating strategies to treat both adult and pediatric tumors is also surveyed. Finally, the work exploring the possibility of other neurotropic viral candidates has been elaborated. More insight into the biological interactions between tumor, brain, and body is needed to address this particularly difficult clinical challenge. While there is still no clear, effective treatment for brain malignancies, the utilization of oncolytic viruses shows potential both as a treatment and as a tool to better understand the immune microenvironment of this pathology.