Activation of innate and adaptive immunity as an effective combined strategy for cancer immunotherapy

Immunotherapeutic approaches can demonstrate some antitumor benefit, but their efficacy is limited when they are used as a single modality. We asked if a combinatory approach activating both innate and adaptive immunity would improve cancer immunotherapy. We have previously shown that an agonistic anti-CD40 monoclonal antibody (anti-CD40) in combination with a toll-like receptor 9 agonist, CpG, can activate macrophages in mice, leading to tumor cell killing. Separately, we have shown that a direct intratumoral injection of an immunocytokine (IC) consisting of anti-GD2 antibody linked to interleukin-2 can activate NK and T cells, resulting in antitumor effects. We hypothesize that activation of macrophages (with anti-CD40/CpG) and NK cells (with IC) will increase tumor destruction and presentation of tumor antigens, leading to T cell activation, which in turn could be further augmented by anti-CTLA-4 antibody, resulting in tumor eradication and prevention of tumor recurrence. Using the mouse GD2⁺ B78 melanoma model, we show that anti-CD40/CpG and IC/anti-CTLA-4 synergistically induced regression of established subcutaneous tumors, resulting in the cure of 50% of mice and development of immunological memory against B78 as well as wild type B16 tumors. While the antitumor effect of anti-CD40/CpG was T cell independent, the antitumor effect of IC/anti-CTLA-4 required T cells. Anti-CD40/CpG treatment led to upregulation of T cell activation markers in draining lymph nodes. Finally, the combined treatment with anti-CD40/CpG and IC/anti-CTLA-4 was effective against B16 lung metastases. We suggest that a combination of anti-CD40/CpG and IC/anti-CTLA-4 should be tested as a clinically relevant novel treatment strategy.