Local Modulation of Immune Receptors to Enhance the Response to Dendritic Cell Vaccination in Metastatic Melanoma

A variety of trials of immunotherapy in metastatic melanoma have clearly demonstrated that immune responses against melanoma can be induced, but only a few patient have responded clinically, suggesting that new strategies to enhance anti-cancer immune responses are needed. Most of these immunotherapy trials have focused on antigen delivery and providing stimulatory antigen-specific signals to T cells. However, the induction of antigen-specific T cell-mediated immune responses is regulated not only by stimulatory signals, but also by inhibitory receptor-mediated signals. Studies have demonstrated that administering mAbs targeting such immune-modulating receptors on T cells enhances vaccine-induced anti-tumor immunity, suggesting that such an approach might improve the efficacy of clinical cancer vaccines. However, systemic administration such mAbs has been associated with severe, sometimes fatal, autoimmunity. We have developed an approach for targeted delivery of such immune modulatory proteins and mAbs, using immune modulator RNA-transfected dendritic cells (DC), to sites where anti-tumor T cells are induced. Our preliminary studies indicate that this approach may eliminate the adverse effects associated with systemic administration immune modulators, while also enhancing vaccine-induced immune responses. Therefore, the objective of this proposed Phase I immunotherapy trial is to determine the safety and obtain preliminary data on the efficacy of vaccination of human subjects with melanoma tumor associated antigen (TAA) RNA-transfected mature monocyte-derived DC coadministered with additional untransfected DC (Study Arm A), DC transfected with RNA encoding a soluble GITR-L fusion protein (Study Arm B), DC transfected with RNA encoding the humanized heavy and light chains of an antagonistic anti-CTLA-4 mAb (Study Arm C), or DC transfected with combined GITR-L and anti-CTLA-4 mAb RNA (Study Arm D). All study subjects will undergo leukapheresis for collection of peripheral blood mononuclear cells (PBMC) and purified monocytes will be cultured with the cytokines GM-CSF and IL-4 to produce immature DC. After the induction maturation with a standard cytokine cocktail, half of the DC will then be transfected with RNA encoding melanoma TAAs MART, tyrosinase, and gp100, and MAGE-3, while the remaining half of the DC will be either untransfected (Study Arm A) or will be transfected with immune modulator RNA (Study Arm B, C, and D). DC will be cryopreserved. Subjects will then be immunized with these DC, weekly for six intranodal injections. For each subject, safety and toxicity will be assessed, and anti-tumor immune responses will be measured.