PROJECT SUMMARY/ABSTRACT Immune checkpoint inhibitors (ICI) such as anti-PD-1 antibodies, have improved the survival of patients with metastatic head and neck squamous cell carcinoma (HNSCC). However, only a subset (<20%) of patients responds to single agent ICI. Since ICI acts by blocking the negative regulators of pre-existing anti-tumor T cell immunity, the lack of response of the majority of HNSCC patients to anti-PD-1 mAb suggests that most HNSCC patients either do not have pre-existing anti-tumor immunity or that other immunosuppressive pathways play a dominant role. Therefore, combining anti-PD-1 mAb with a vaccination approach that can induce anti-tumor T cell immunity is likely to be more effective than single agent ICI. However, patient-to-patient variation in target antigens makes HNSCC one of the most challenging cancers for developing an effective therapeutic vaccine. To address this, we propose to develop a novel vaccine immunotherapy to treat HNSCC using an approach that is personalized, thus incorporating patient-to-patient variation in antigenic signature. Our autologous therapeutic vaccine consists of tumor membrane vesicles (TMVs) made from the patients’ tumors conjugated to potent immunostimulatory molecules (ISMs) by protein transfer. In contrast to previous autologous tumor lysate vaccines, the tumor antigens are physically linked to ISMs via a TMV scaffold in our vaccines, thus simultaneously presenting the patient’s unique tumor antigen signature and ISMs to the immune cells to induce effective anti-tumor responses. Such a physical linkage of antigens and adjuvants has been shown to induce a more effective immune response than a mixture of unconjugated antigens and adjuvants. Furthermore, unlike whole cell vaccines, TMV vaccines do not secrete immunosuppressive factors. TMVs are particulate in nature and carry membrane associated tumor antigens, altered carbohydrate antigens, and antigenic epitopes derived from cytosolic proteins in the form of major histocompatibility complex associated peptides. Our preliminary studies show that TMV vaccine in combination with ICI is more effective than ICI alone in murine oral cancer models. We hypothesize that a personalized vaccine immunotherapy will expand tumor-specific T cells and the addition of ICI prevents the exhaustion of tumor antigen-specific T cells to induce robust anti-tumor T cell responses and significantly enhance the clinical response against HNSCC tumors that are not responsive to currently approved immunotherapies. The hypothesis will be tested in the following specific aims: Aim 1: To determine whether the dose and schedule can be altered to increase the anti-tumor immune response and efficacy of TMV vaccine in a mouse model of HNSCC, Aim 2: To investigate whether TMV vaccine inhibits metastasis/recurrence and extends the survival of mice in a clinically relevant setting, and Aim 3: To conduct a phase 1b dose-escalation clinical trial of TMV-based immunotherapy alone and in combination with pembrolizumab in patients with recurrent or metastatic HNSCC. Completion of the proposed work will advance a novel, personalized vaccine immunotherapy approach for patients with recurrent and/or metastatic HNSCC.

PROJECT NARRATIVE: Head and neck cancer is one of the major causes of cancer related death in the US and worldwide and exhibits a high degree of interpersonal and intratumoral heterogeneity, making it difficult to treat. Our grant application proposes to develop a novel personalized immunotherapy approach using membrane vesicles prepared from patients’ own surgically excised tumor tissue, modifying them by protein transfer to express immunostimulatory molecules and administering them to patients along with immune checkpoint inhibitor to boost the immune response against cancer cells. The proposed approach does not require establishment of cell lines, identification of tumor antigens or in vitro manipulation of immune cells, thus making it applicable to wide number of patients in a cost-effective manner.