Abstract 580: Detailed analysis of immune responses induced against patient-specific neoantigens using theex-vivoinduction protocol, NEO-STIM™

Background: Neoantigens are tumor-specific antigens that have been shown to be critical in the anti-tumor immune response. These antigens are not subject to central immune tolerance and are therefore potentially more immunogenic than tumor-associated antigens. The goal of our studies is to assess the immunogenic potential of high-quality neoantigen targets, as defined through our bioinformatic engine RECON®, as well as perform detailed characterization of the induced T cell responses towards these neoantigen targets. Methods: Patient-specific neoantigens were predicted using our bioinformatic engine RECON. The predicted high quality neoantigens were utilized in our proprietary ex-vivo stimulation protocol NEO-STIM to assess immunogenicity. NEO-STIM is used to prime, activate and expand memory and de novo T cell responses from both the CD4+ as well as the CD8+ compartment. In-depth analysis was performed to characterize the specificity, functionality (cytokine production and cytolytic capacity) and diversity of the induced T cell responses. Results: Here we present the successful induction of memory and de novo CD8+ T cell responses in PBMCs isolated by leukapheresis from three patients using NEO-STIM (2 with melanoma & 1 with NSCLC). We then deeply characterize the induced CD8+ T cell responses of one of the melanoma patients and show that these responses are functional, specific and have cytolytic capacity. Furthermore, we use paired single cell RNA and TCR sequencing to assess the diversity and gene expression profile of these responses. Conclusions: NEO-STIM is a novel platform to understand the immunogenic potential of high-quality neoantigen-targets in detail. Moreover, this platform can be utilized to generate T cell products for adoptive cell therapy for patients with a variety of solid and liquid tumors. Citation Format: Divya Lenkala, Jessica Kohler, Brian McCarthy, Michael Nelson, Rachel DeBarge, Yvonne Ware, Yuting Huang, Janani Sridar, Yusuf Nasrullah, Dewi Hartjano, Asaf Poran, Sejuti Sengupta, Joost H. van den Berg, Matt Goldstein, Richard B. Gaynor, Marit M. van Buuren. Detailed analysis of immune responses induced against patient-specific neoantigens using the ex-vivo induction protocol, NEO-STIM™ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 580.