Improving methods for cytokine immunotherapy of cancer

Abstract

Cytokine therapy can activate potent antitumor responses, yet collateral toxicity often limits dosages. Although immunocytokines have been designed with the intent to localize cytokine activity, systemic dose-limiting side effects are not fully ameliorated by attempted tumor targeting. In the first part of this work, we used the B 1 6F 10 melanoma model to demonstrate that a nontoxic dose of IL-2 immunocytokine synergized with tumor-specific antibody to significantly enhance therapeutic outcomes compared to monotherapy with immunocytokine, concomitant with increased tumor saturation and intratumoral cytokine responses. Examination of cell subset biodistribution showed that the immunocytokine associated mainly with IL-2R-expressing innate immune cells, with more bound immunocytokine present in systemic organs than in the tumor microenvironment. More surprisingly, immunocytokine antigen specificity and Fc[gamma]R interactions did not appear necessary for therapeutic efficacy or biodistribution patterns, as immunocytokines with irrelevant specificity and/or inactive mutant Fc domains behaved similarly to tumor-specific immunocytokine. IL-2-IL-2R interactions, rather than antibody-antigen targeting, dictated immunocytokine localization; however, the lack of tumor targeting did not preclude successful antibody combination therapy. This study presents a safe, straightforward strategy for augmenting immunocytokine efficacy via supplementary antibody dosing and explores underappreciated factors that can subvert efforts to purposefully alter cytokine biodistribution. Numerous studies have identified cancer immunotherapy combinations that exhibit synergistic antitumor activity, but surprisingly, these studies rarely consider the effects of relative dose timing. In the second part of this work, using established syngeneic tumor models, we found that staggering IFN[alpha] administration after, rather than simultaneously with, serum-persistent IL-2 and tumor-specific antibody significantly increased long-term survival and generated immunological memory. Successful combination therapy required IFNa-induced activation of cross-presenting CD8[alpha]+ DCs following release of antigenic tumor debris by the IL-2-and-antibody-mediated immune response. Due to decreased phagocytic ability post-maturation, DCs activated too early captured much less antigen and could not effectively prime CD8+ T cells. Temporally programming DC activation to occur after tumoricidal activity enhanced tumor control by multiple combination immunotherapies that act through distinct mechanistic pathways, presenting a facile strategy for augmenting efficacy in the combinatorial treatment setting and highlighting dose schedule as an overlooked factor that can profoundly affect the success of multi-component immunotherapies.