Abstract 620: Intratumoral microdosing via the CIVO® Platform reveals anti-tumor immune responses induced by the STING Agonist TAK-676 alone and in combination with chemotherapies

Abstract Purpose/Objectives: Individual tumor complexity and the emergence of treatment resistance mechanisms have proven challenging for oncology drug development, and methods for prioritizing combination therapy approaches are needed. The CIVO (Comparative In Vivo Oncology) platform can simultaneously deliver up to 8 drugs and combinations in microdose amounts to distinct, trackable regions within a single intact tumor, enabling studies that can assess multiple drugs and combinations directly in patients during early drug development. This study employed CIVO to assess two combination strategies incorporating the STING (Stimulator of Interferon Genes) agonist TAK-676 and chemotherapies capable of inducing immunogenic cell death. We evaluated TAK-676’s ability to elicit pharmacodynamic (PD) changes suggestive of anti-tumor immune activation within the tumor microenvironment (TME) in a syngeneic mouse model, both as monotherapy and in combination with cisplatin and 5-FU or cisplatin and paclitaxel chemotherapy doublets. Materials/Methods: TAK-676 and chemotherapy combinations were simultaneously microdosed via CIVO in a syngeneic mouse melanoma model (YUMM1.7). Successful injections were visualized after administration, during sample processing, and in biomarker-stained tissue sections via a fluorescent tracking marker co-injected through each needle, and PD responses were assessed via immunohistochemistry and in situ hybridization following tumor resection. Results: Drug mechanism of action-specific biomarker activity was evident as early as 4 hours after injection. TAK-676 induced robust elevation of pIRF3 and CXCL10 along with IFNγ from both T and NK cell compartments, indicating STING pathway activation. Phospho-histone H3 accumulation was noted in response to paclitaxel-induced mitotic arrest. 5-FU and cisplatin induced localized DNA damage, visible via elevated phospho-histone H2AX-positive nuclei. Cytotoxic T lymphocyte (CTL) accumulation was detected around TAK-676 injection sites, likely recruited from the local TME via induction of chemokines such as CXCL10. Early tumor cell apoptosis and induction of pro-inflammatory cytokines such as CXCL10 were detected in response to both triplet combinations. CTL activation was enhanced in response to both triplet combinations by 24 hours, whereas CTL enrichment at levels greater than induced by TAK-676 alone was noted specifically in response to the triplet combination with cisplatin and paclitaxel by 72 hours. Conclusion: These studies highlight TAK-676’s potential to promote anti-tumor immunity and the utility of the CIVO platform to reveal and characterize combination-specific responses. This application of CIVO is being further evaluated in an ongoing Phase 0 trial in patients with head and neck squamous cell carcinoma (NCT04541108). Citation Format: Beryl A. Hatton, Marc Grenley, Sally Ditzler, Richard A. Klinghoffer, Allison J. Berger, Karim S. Malek, Richard C. Gregory, Neil B. Lineberry. Intratumoral microdosing via the CIVO® Platform reveals anti-tumor immune responses induced by the STING Agonist TAK-676 alone and in combination with chemotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 620.