Immunotherapy for Recurrent Glioma—From Bench to Bedside

SIMPLE SUMMARY: Glioma is the most common and aggressive brain tumor worldwide, and most patients suffer from a recurrence. Additionally, recurrent glioma is often resistant to chemotherapies and radiotherapy. Hence, immunotherapy has come into people’s sights. The most-used immunotherapy is immune checkpoint blockade (ICB), which has shown encouraging efficacy when combined with other immune strategies, especially with antiangiogenetic antibodies. Other promising immune regimes include multiple immunotherapies which function through different mechanisms, such as oncolytic viruses, chimeric antigen receptor T cell therapies and vaccination strategies. In this review, we discuss current immune therapies applied to recurrent glioma, based on the literature of preclinical animal models, and current ongoing clinical trials published in the last 5 years. These immunotherapies have been proved to be safe and tolerant, while some combinational regimes have provided satisfying efficacy on a subgroup of patients with specific gene mutation backgrounds. Though great progress has been made, further exploration of different combination strategies is needed. ABSTRACT: Glioma is the most aggressive malignant tumor of the central nervous system, and most patients suffer from a recurrence. Unfortunately, recurrent glioma often becomes resistant to established chemotherapy and radiotherapy treatments. Immunotherapy, a rapidly developing anti-tumor therapy, has shown a potential value in treating recurrent glioma. Multiple immune strategies have been explored. The most-used ones are immune checkpoint blockade (ICB) antibodies, which are barely effective in monotherapy. However, when combined with other immunotherapy, especially with anti-angiogenesis antibodies, ICB has shown encouraging efficacy and enhanced anti-tumor immune response. Oncolytic viruses and CAR-T therapies have shown promising results in recurrent glioma through multiple mechanisms. Vaccination strategies and immune-cell-based immunotherapies are promising in some subgroups of patients, and multiple new tumor antigenic targets have been discovered. In this review, we discuss current applicable immunotherapies and related mechanisms for recurrent glioma, focusing on multiple preclinical models and clinical trials in the last 5 years. Through reviewing the current combination of immune strategies, we would like to provide substantive thoughts for further novel therapeutic regimes treating recurrent glioma.