Dendritic cell vaccination in combination with TLR-7 agonist, imiquimod, following radio-chemotherapy for newly diagnosed glioblastoma

Abstract

2021 Background: Standard therapy for glioblastoma, which includes surgery followed by radiation and concurrent chemotherapy, creates a low tumor burden environment that could be ideal for immunotherapeutic approaches. We conducted a Phase I study to assess the safety and immunologic responses of tumor lysate-pulsed dendritic cell (DC) therapy plus topical imiquimod, in combination with standard radio-chemotherapy. Methods: Thirteen patients with newly diagnosed glioblastoma were immunized using autologous tumor lysate-pulsed DC. Each patient initially received 3 immunizations at 2-week intervals, following completion of a 6-week course of radio- chemotherapy. Four patients received 1 million DC, 4 received 5 million, and 5 received 10 million DC per immunization. Patients without tumor progression subsequently received booster vaccinations combined with topical administration of the TLR-7 agonist imiquimod. Immunologic responses to tumor antigens were monitored by HLA-restricted tetramer staining, CTL assays, and quantitation of T-regulatory cells. Clinical tumor growth was monitored by brain MRI scans every 2 months, and the primary clinical endpoint was 2-year survival. Results: All immunizations were well tolerated, with only mild side effects attributable to the DC vaccination and imiquimod adjuvant. Increased levels of CD8+ T cells reactive against tumor antigens, (e.g., gp100, TRP-2, her-2, survivin, and CMV antigens), were detected in 5 patients. Median PFS and OS have not been reached in this trial. To date, 6 of the 13 patients have progressed, and 4 of those have died. The median PFS to date is 18.1 mos. and median OS is 33.8 mos. This compares favorably with controls from the published literature, with a median PFS of 6.9 mos and OS of 14.6 mos. Conclusions: This study demonstrates the safety and clinical/immunologic effects of an autologous tumor lysate-pulsed DC vaccine for patients with newly diagnosed glioblastoma. The adjunctive use of the TLR-7 agonist imiquimod with DC vaccination appears to be non-toxic, and deserves further study. We demonstrate that this active immunotherapy strategy can generate antigen-specific immunologic responses in brain tumor patients following standard radio-chemotherapy. No significant financial relationships to disclose.