Work

1079 Development of a biologically aligned ex vivo TumorGraft3D platform to evaluate STC-1010-mediated immune priming and colorectal tumor killing

Year: 2026

Type: conference-abstract

Abstract: Background Microsatellite-stable metastatic colorectal cancer (MSS mCRC) remains poorly responsive to immune checkpoint blockade, supporting immunotherapies that broaden tumor antigen recognition. STC-1010 is an allogeneic multi-antigen active immunotherapy generated from the Stimulated Ghost Cell platform and composed of stressed, haptenated and inactivated colorectal cancer cell lines. We designed a human ex vivo workflow reflecting the proposed STC-1010 mechanism of action, linking dendritic-cell antigen capture/presentation, CD8+ T-cell activation and tumor-cell killing. This workflow was advanced toward a patient-aligned translational assay using clinically annotated TumorGraft3D models derived from well-characterized PDX models. While multiclonal 3D organ-like tumor cultures are increasingly used for ex vivo drug testing, their application in active immunotherapy workflows remains largely unexplored.Methods Monocyte-derived dendritic cells (DCs) from HLA-A2 + healthy donor PBMCs were matured, exposed to STC-1010 or vehicle, and co-cultured with autologous CD8+ T cells. DC activation was assessed by phenotyping, cytokine secretion and RNA-seq pathway analysis. Tumor killing was evaluated in HCT116 2D cultures by live-cell caspase-3/7 apoptosis imaging and in HCT116 3D spheroids using GFP viability and DRAQ7 dead-cell readouts. The workflow is being implemented in clinically annotated patient-derived TumorGraft3D models. To this end, a confirmed MSS, HLA-A2-positive CRC TumorGraft3D model, characterized by WES/RNA-seq and carrying key mutations (KRAS, APC, TP53 and PIK3CA) was selected to evaluate STC-1010 induced T-cell activation and tumor killing.Results STC-1010-treated mature DCs showed selective detection of haptenated material and enrichment of antigen-processing/presentation, phagosome, lysosome and cytokine–receptor pathways, supporting APC activation. Functionally, STC-1010-primed CD8 + T cells significantly increased HCT116 tumor-cell apoptosis in 2D culture by 1.9-fold versus vehicle (P = 0.0003). In HCT116 3D spheroids, STC-1010-primed immune cells significantly reduced viable tumor signal by 55–60% and increased dead tumor cells from 35–40% to 50–55% at Day 7 (figure 1). A clinically annotated MSS, HLA-A2-positive CRC TumorGraft3D model was confirmed for implementation. Its WES/RNA-seq data, enabling molecular alignment with the STC-1010 first-in-human clinical trial (NCT06934538) population and future integration of tumor-intrinsic features with immune-mediated killing readouts. Feasibility experiments using cryopreserved PBMCs confirmed distinct monocyte, immature DC and mature DC phenotypes, supporting compatibility of the T-cell-priming workflow for downstream TumorGraft3D-based applications.Conclusions These data support a stepwise translational assay strategy for STC-1010, progressing from mechanistically informed 2D killing assays to 3D spheroids and clinically aligned TumorGraft3D testing. This approach links STC-1010 mechanism-of-action readouts with clinically relevant tumor-killing endpoints, supporting the use of TumorGraft3D models to evaluate active immunotherapies in MSS mCRC.Acknowledgements We thank Claudia Carenza from Champions Oncology for her support with flow cytometry analysis, BanuPriya Sridharan from Champions Oncology for her scientific and operational guidance on the ex vivo work, and Romain Boidot from Centre Georges-François Leclerc for his support and scientific input.Ethics Approval Human PBMCs were obtained from BioIVT from HLA-A2 + healthy donors under IRB-approved collection protocols with donor informed consent. TumorGraft3D models were provided by Champions Oncology and derived from de-identified, clinically annotated patient-derived TumorGraft/PDX models generated from donor tumor specimens collected with informed consent under applicable IRB/ethical approvals. No new human participants or animal procedures were enrolled or performed by Brenus Pharma for this study.Abstract 1079 Figure 1STC-1010 induces tumor killing in 3D model and significantly reduces viable tumor cells and increases % of dead tumor cells. DRAQ7 Imaging : Identification and quantification of dead cells during tumor killing assay. HCT116 Tumor Microtissue (TuMT) in co-culture with CD8+ T at day 7: end of co-culture) (Scale bar 100 µm). GFP Intensity measurement during the co-culture

Source: Journal for ImmunoTherapy of Cancer

DOI: 10.1136/jitc-2026-sitc2026.1079