Feasibility study of a personalized tumor membrane vesicle vaccine immunotherapy for head and neck squamous cell carcinoma (HNSCC).

e14673 Background: Head and neck cancer exhibits a high degree of heterogeneity, with lack of common therapeutic targets. Our phase 1 clinical trial will evaluate a novel personalized immunotherapy approach using tumor membrane vesicles (TMV) prepared from the patients’ own surgically excised tumor tissue and modifying them by attaching GPI-B7-1 and GPI-IL-12 as immune boosting molecules. This personalized vaccine will then be administered to boost the tumor-specific immunity. We report here the feasibility of developing an effective personalized therapeutic cancer vaccine from surgically collected tumor tissue from patients with HNSCC. Methods: After obtaining informed consent, a total of 10 tumor specimens from 10 patients with HNSCC of various sites were collected (0.29-1.23 grams) and graded for cellularity by a pathologist. Tumor samples were then homogenized using sterile, disposable probes. The homogenate was ultracentrifuged over a sucrose gradient to enrich tumor membrane vesicles (TMV). Yield was evaluated by protein concentration and particle size was assessed by dynamic light scattering. TMV preparations were incorporated with GPI-B7-1 and GPI-IL-12 to generate the TMV vaccine using protein transfer, a spontaneous process. For the in vivo murine studies, TMV vaccine is prepared from murine oral cancer (MOC1) tumors and incorporated with murine GPI-B7-1 and GPI-IL-12. To investigate the protective anti-tumor immune response of TMV vaccine in combination with anti-PD1 antibody therapy, we used established murine oral cancer models. We administered two doses of TMV vaccine to naïve C57BL/6 mice and four doses of anti-PD-1 mAb. Mice were monitored for 21 months and then challenged with MOC1 tumor cells 1 week prior to euthanasia. Spleens were flash frozen in liquid nitrogen and stored in -80oC until RNA is isolated for RNA-seq analysis. Results: The yields of TMV were 2.5 – 5 mg per gram of tumor tissue from four human tumor samples. Further refinement of the TMV production process yielded up to 6 mg of TMV/gram of tumor tissue. All samples passed for incorporation of GPI-B7-1 and GPI-IL-12. GPI-B7-1 is able to bind to a natural ligand, CTLA-4 suggesting it is biologically active. All samples also demonstrated biologic activity for GPI-IL-12 as tested using a reporter cell line for IL-12 and displayed acceptable endotoxin levels in a range of 1-34 EU/mg TMV vaccine. The remaining 6 tumor samples are being processed. RNA-seq data from mouse model suggests that the TMV vaccine showed synergistic activity when combined with anti-PD1 antibody, with enhanced T cell responses. Conclusions: TMV vaccine production is feasible for a phase 1 clinical trial for patients whose resected tumor is at least 0.5 g in weight and 40% cellularity. Data in mice show that TMV vaccine synergizes with anti-PD1 in inducing tumor responses.