Abstract 3301: A sequential treatment strategy for ex vivo profiling of live tumor fragments that mitigates tumor heterogeneity and tissue scarcity from core needle biopsies to characterize response to immunotherapies

Abstract Immunotherapies are highly effective treatment options for cancer; yet they do not work in all patients, and current companion diagnostic (CDx) biomarkers do not always align with response. Ex vivo profiling of live tumor samples provides the ability to measure T cell activity in response to treatment and is a potential means of improving response prediction. The limited amount of tumor tissue available from core needle biopsies (CNBs) presents a challenge when split into control and treatment groups for ex vivo profiling, as tumor heterogeneity causes increased variability and sampling errors. Elephas has developed a treatment strategy where control (IgG) and immune checkpoint inhibitor (ICI) treatments are performed sequentially on the same tissue within a single well. Changes in the rate of cytokine secretion are then compared between ICI and IgG treatment to characterize response to therapy. For these experiments, human CNBs (n>150) were collected from diverse tumor types during standard of care diagnostic procedures and sliced using a proprietary cutting instrument. Each biopsy was profiled for response to ICI using a multiplexed cytokine immunoassay. Sequential aliquots of conditioned media were collected from cultured biopsy slices at three time points: ∼4 hrs post-encapsulation with a proprietary hydrogel, following ∼16 hrs of IgG treatment and following ∼28 hrs of treatment with ICI. Cytokine results were assessed for data quality to inform inclusion/exclusion of data points for analysis/algorithm development. CDx biomarker status (PD-L1, MMR/MSI and TMB) for individual biopsies was obtained from medical records. Our results show live tumor fragments, obtained from resections where tumor tissue amount was sufficient to address inter-well heterogeneity, exhibit comparable cytokine response profiles when stimulated with CD3/CD28 at experiment start vs. following 20 hrs of IgG treatment. An algorithm to define ex vivo response to ICI treatment in CNBs was then developed using tissue viability measurements and treatment-induced changes in cytokines. Response on the Elephas platform was subsequently compared to CDx biomarker status and clinical response from patient medical records. A sequential treatment strategy for the assessment of response to immunotherapy is an effective approach to capture treatment-induced changes in cytokine response. Sequential treatment of CNBs circumvents issues of tumor heterogeneity inherent to cross-well comparison in settings of limited tissue availability. Implementation of this strategy enables the Elephas platform to differentiate potential responder and non-responder CNB specimens to immunotherapy ex vivo. Citation Format: Christina Scribano, Pichet Adstamongkonkul, Sean Caenepeel, Nicholas Dana, Jackie Derrick, Evan Flietner, Hilary Hernan, Christin Johnson, Nathan Marhefke, Payton McDonnell, Betsy Mulligan, Amreen Nasreen, Josh Porter, Jordyn Richardson, Sidney Schneider, Mikaela Schultz, Mike Smith, Chetan Sood, Aishwarya Sunil, Lindsey Vedder, Ellen Wargowski, Hinco Gierman, Andreas Friedl, Laura Hrycyniak, Michael Korrer, T.S. Ramasubramanian. A sequential treatment strategy for ex vivo profiling of live tumor fragments that mitigates tumor heterogeneity and tissue scarcity from core needle biopsies to characterize response to immunotherapies [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 3301.