EXTH-11. TREATMENT WITH DELTA-24-RGDOX OF SUBCUTANEOUS TUMORS RESULTS IN ABSCOPAL EFFECT ERADICATING INTRACRANIAL MELANOMAS

Abstract

Abstract Immune checkpoint blockade has revolutionized cancer therapy; however the therapeutic benefit is limited to only a subset of patients with immunogenic (“hot”) tumors and is compromised by immune-related adverse events. We have reported the efficacy of oncolytic adenovirus Delta-24-RGDOX (DNX-2440) in syngeneic glioma mouse models. We hypothesized that localized treatment with the virus is effective against disseminated melanomas, including intracranial melanomas. We tested the hypothesis in the subcutaneous (s.c.)/s.c. and s.c./intracranial (i.c.) melanoma models derived from luciferase-expressing B16-Red-FLuc cells in C57BL/6 mice. First, through monitoring tumor growth with bioluminescence imaging, we found that, in both s.c./s.c. and s.c./i.c. models, three injections of Delta-24-RGDOX significantly inhibited the growth of both the virus-injected s.c. tumor and untreated distant s.c. or i.c. tumor, thereby prolonging survival. Next, through cell profiling with flow cytometry, we observed that the virus increased the presence of T cells and effector T cell frequency in the virus-injected tumor and mediated the same changes in T cells from peripheral blood, tumor-draining lymph nodes (TDLNs), spleens, and brain hemispheres with untreated tumor. Moreover, Delta-24-RGDOX decreased the frequency of exhausted T cells and regulatory T cells in the virus-injected and untreated i.c. tumors. Consequently, the virus promoted recruitment and/or in situ expansion of antigen-specific T cells in tumors expressing the target antigen. Therefore, we concluded that local intratumoral injection of Delta-24-RGDOX resulted in systemic immune activity against the disseminated tumors. Furthermore, we speculate that given the immunogenicity, cancer-selectivity and intratumoral administration of the virus, Delta-24-RGDOX is expected to have an improved safety profile when compared to immune checkpoint blockade treatment strategies. This is the first report demonstrating that local administration of oncolytic adenovirus results in eradication of intracranial tumors, suggesting Delta-24-RGDOX could be used to manage brain metastases of melanoma.