Abstract 6555: A method for preparing tumor tissues for ex vivo culture that retains T cells within live tumor fragments while preserving tissue viability and T cell function

Characterization of response to immunotherapy ex vivo requires preservation of the live tumor microenvironment (TME), including the sequestration of immune cells. Elephas has developed a methodology that incorporates proprietary cutting instruments designed to optimally fragment live tumor resections and core needle biopsies (CNBs), and a proprietary hydrogel that supports the viability of tumor fragments in ex vivo culture while sequestering T cells in their native TME. In this study, tumor specimens (human tumors and humanized PDX) were fragmented using one of two proprietary cutting instruments designed to cut tumor resections into 300 x 300 x 300μm fragments or CNBs into 300μm thick slices. Both tissue form factors were then encapsulated in a propriety hydrogel. Tissue viability was assessed via the Cell Counting Kit 8 (CCK8) assay and in some cases a lactate dehydrogenase assay. Conditioned media from culture plates harboring encapsulated fragments was collected for multiplex cytokine analysis. At the end of ex vivo experimentation tissue was paraffin embedded and formalin fixed for H&E staining and immunohistochemistry was performed to assess T cell retention. Elephas proprietary cutting instruments produced tumor fragments of consistent size and volume. These fragments retained histological characteristics of the original tumor resections from which they were derived and their encapsulation in a proprietary hydrogel improved T cell retention over 2 days of ex vivo culture. Preservation of the native TME was further demonstrated following αPD-1 treatment of tumor fragments with known CDx biomarker status where an enriched cytokine response profile was observed in biomarker positive samples. In CNBs processed on the Elephas platform, overall viability and T cell function were maintained following simulated overnight shipment at 4°C. To overcome challenges associated with the limited amount of tissue in CNBs (e.g. heterogeneity), we developed a treatment strategy where control and treatments were performed sequentially on the same tissue within a single well. Fold changes in the rate of cytokine secretion following sequential (1) control and (2) αPD-1 + STING agonist treatment exhibit improved CVs (%) relative to an inter-well treatment design (control and treatment wells). Additionally, live tumor biopsies were shown to exhibit comparable IFNγ response following treatment with αPD-1 + STING agonist at the experiment start vs. following 20 hrs of control treatment. The Elephas platform preserves overall cell viability and T cell function in the TME of CNBs ex vivo using proprietary cutting instruments and hydrogel encapsulation techniques. Using this preparation method, the Elephas platform optimally captures the heterogeneity in human tumors (resections and CNBs) while allowing for comparisons between treatment conditions. Citation Format: Michael Korrer, Christina Scribano, Pichet Adstamongkonkul, Todd Bakken, Torey Browning, Christian Baltes, Sean Caenepeel, Nicholas Dana, Jackie Derrick, Thomas Dietz, Evan Flietner, Hilary Hernan, Christin Johnson, Payton McDonnell, Jacob Nesemeier, Josh Porter, Abhijeet Prasad, Jordyn Richardson, Sidney Schneider, Rebecca Tarlazzi, Noah Van Der Weide, Lindsey Vedder, Ming (Veronica) Wang, Hinco Gierman, Andreas Friedl, Laura Hrycyniak, T.S. Ramasubramanian. A method for preparing tumor tissues for ex vivo culture that retains T cells within live tumor fragments while preserving tissue viability and T cell function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6555.