There is an urgent need for improved therapy for advanced ovarian carcinoma, which may be met by administering immune-modulatory monoclonal antibodies (mAbs) to generate a tumor-destructive immune response. Using the ID8 mouse ovarian cancer model, we investigated the therapeutic efficacy of various mAb combinations in mice with intraperitoneal (i.p.) tumor established by transplanting 3 × 106 ID8 cells 10 days previously. While most of the tested mAbs were ineffective when given individually or together, the data confirm our previous finding that 2 i.p. injections of a combination of anti-CD137 with anti-PD-1 mAbs doubles overall survival. Mice treated with this mAb combination have a significantly increased frequency and total number of CD8+ T cells both in the peritoneal lavage and spleens, and these cells are functional as demonstrated by antigen-specific cytolytic activity and IFN-γ production. While administration of anti-CD137 mAb as a single agent similarly increases CD8+ T cells, these have no functional activity, which may be attributed to up-regulation of co-inhibitory PD-1 and TIM-3 molecules induced by CD137. Addition of the anti-cancer drug cisplatin to the 2 mAb combination increased overall survival >90 days (and was probably curative) by a mechanism which included a systemic CD8+ T cell response with tumor specificity and immunological memory. Strikingly, combined treatment of cisplatin and CD137/PD-1 mAb also gave rise to the long-term survival of mice with established TC1 lung tumors. A similar combination of the 2 mAbs and cisplatin should be considered for clinical ‘translation’.

Mice with intraperitoneal ID8 ovarian carcinoma or subcutaneous SW1 melanoma were injected with monoclonal antibodies (mAbs) to CD137+PD-1+CTLA4 7-15 days following tumor initiation. Survival of mice with ID8 tumors tripled and >40% of mice with SW1 tumors remain healthy >150 days after later treatment and are probably cured. Therapeutic efficacy was associated with a systemic immune response with memory and antigen specificity and required CD4+ cells and involved CD8+ cells and NK cells to a less extent. The 3 mAb combination significantly decreased CD19+ cells at tumor sites, increased IFNγ and TNFα producing CD4+ and CD8+ T cells and mature CD86+ DC, and it increased the ratios of effector CD4+ and CD8+ T cells to CD4+Foxp3+ regulatory T cells and to CD11b+Gr-1+ myeloid suppressor cells. This is consistent with shifting the tumor microenvironment from an immunosuppressive Th2 to an immunostimulatory Th1 type and is further supported by PCR data. Adding an anti-CD19 mAb to the 3 mAb combination in the SW1 model further increased therapeutic efficacy. Data from ongoing experiments show that intratumoral injection of a combination of mAbs to CD137+PD-1+CLA4+CD19 can induce complete regression and dramatically prolong survival also in the TC1 carcinoma and B16 melanoma models, suggesting that the approach has general validity.

Purpose Immunomodulatory mAbs can treat cancer, but cures are rare except for small tumors. Our objective was to explore whether the therapeutic window increases by combining mAbs with different modes of action and injecting them into tumors. Experimental Design Combinations of mAbs to CD137/PD-1/CTLA4 or CD137/PD-1/CTLA4/CD19 were administrated intratumorally to mice with syngeneic tumors (B16 and SW1 melanoma, TC1 lung carcinoma), including tumors with a mean surface of ~80mm2. Survival and tumor growth were assessed. Immunological responses were evaluated using flow cytometry and qRT-PCR. Results Over 50% of tumor-bearing mice had complete regression and long-term survival after tumor injection with mAbs recognizing CD137/PD-1/CTLA4/CD19 with similar responses in 3 models. Intratumoral injection was more efficacious than i.p. injection to cause rejection also of untreated tumors in the same mice. The 3 mAb combination could also induce regression but was less efficacious. There were few side-effects and therapy resistant tumors were not observed. Transplanted tumor cells rapidly caused a Th2 response with increased CD19 cells. Successful therapy shifted this response to the Th1 phenotype with decreased CD19 cells and increased numbers of long term memory CD8 effector cells and T cells making IFNγ and TNFα. Conclusion Intratumoral injection of mAbs recognizing CD137/PD-1/CTLA4/CD19 can eradicate established tumors and reverse a Th2 response with tumor-associated CD19 cells to Th1 immunity while a combination lacking anti-CD19 is less effective. There are several human cancers where a similar approach may provide clinical benefit.