Abstract LB_B16: Quantification of immune-oncology drug responses in autologous co-cultures of ex vivo patient tumor tissues with PBMCs

Abstract Introduction Immuno-oncology drug treatments, including immune checkpoint inhibitors, represent a huge promise for cancer patients and have been clinically approved for some cancer indications. However, patient response rates stay relatively low (about 10-20% responders across indications) hampering the success of such drugs in clinical trials. In addition, current in vitro and in vivo pre-clinical models often lack the (immunological) complexity necessary to predict the clinical effectiveness of such drugs or drug combinations. To bridge this gap in translational models, we have recently developed the 3D Ex vivo Patient Tissue (EVPT) platform. The EVPT platform is leveraging short-term 3D ex vivo tumor culture system containing micro-tissues generated from fresh human tumor material and high content imaging analysis. The platform is preserving the innate tumor microenvironment including resident immune cells, which are crucial for addressing immunological drug responses. In this study we aimed to further boost immune compartment of the assay by addition of autologous immune cells (PBMCs) isolated from whole blood of the patient in parallel with ex vivo tumor processing. Methods Patient tumor tissues from resected NSCLC and muscle-invasive bladder cancer (MIBC) tumors and matching peripheral blood were obtained from commercial tissue providers and processed within 24 hours to preserve the TME. PBMCs were isolated from whole blood and pre-stained with cell tracker. Fresh, minimally processed tumor material was embedded in a protein-rich hydrogel with or without matching PBMCs and exposed to mono- and combination immunotherapies at various doses. Next, the phenotypic screening using our proprietary automated HCI analysis platform was performed. Where applicable, IHC biomarker, flow cytometry and cytokine measurements were performed on fixed tissues or culture supernatants. Results 3D ex vivo co-cultures were executed in 22 NSCLC and 5 MIBC patient samples. Immunological treatment responses varied between tested patients. When comparing co-culture to mono-culture conditions, one third of the samples showed baseline killing associated with PBMCs addition. About 20% of tissues from both indications responded to antiPD1 treatment (Pembrolizumab) and on average 50% of tissues responded to immunostimulatory control SEA. Overall best effects were observed for one test article that was used in three doses in combination with antiPD1. Five out five tested NSLCLC samples showed functional responses in these conditions as wells as two out five MIBC samples. In addition, it induced immunostimulatory effects on the PBMCs in the assay – increased numbers and tumor infiltration rates compared to vehicle control. Conclusions 3D Ex vivo Patient Tissue platform combined with autologous PBMCs offers supplementary readouts such as tumor infiltration and immune cell proliferation while providing TME-rich environment for functional immune-oncology drug testing. Citation Format: Niels Meesters, Sander Basten, Ezgi Kaya Aksoy, Mariusz Madej, Kuan Yan, Emma Spanjaard, Leo S. Price, Nataliia Beztsinna. Quantification of immune-oncology drug responses in autologous co-cultures of ex vivo patient tumor tissues with PBMCs [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_B16.