Breaking the barriers in cancer care: The next generation of herpes simplex virus-based oncolytic immunotherapies for cancer treatment

Since the US Food and Drug Administration first approved talimogene laherparepvec for the treatment of melanoma in 2015, the field of oncolytic immunotherapy (OI) has rapidly evolved. There are numerous ongoing clinical studies assessing the clinical activity of OIs across a wide range of tumor types. Further understanding of the mechanisms underlying the anti-tumor immune response has led to the development of OIs with improved immune-mediated preclinical efficacy. In this review, we discuss the key approaches for developing the next generation of herpes simplex virus-based OIs. Modifications to the viral genome and incorporation of transgenes to promote safety, tumor-selective replication, and immune stimulation are reviewed. We also review the advantages and disadvantages of intratumoral versus intravenous administration, summarize clinical evidence supporting the use of OIs as a strategy to overcome resistance to immune checkpoint blockade, and consider emerging opportunities to improve OI efficacy in the combination setting.