Abstract 4246: SENTI-101, a novel genetically modified allogeneic cell product expressing IL12 and IL21, elicits a tumor-localized, robust, and multimodal immune response in preclinical models of solid tumors
Authors: Gonzalez Alba , Liu Frances D. , Nagaraja Archana , Mullenix Alyssa , Gordley Russell M. , Frimannsson Daniel O. , Benabbas Anissa , Lee Chen-Ting , Truong Tiffany A. , Quach Allison , Tian Mengxi , Martinez Rowena , Savur Rishi , Perry-McNamara Alyssa , Wang Don-Hong , Maller Ori , Iyer Dharini , Magal Ashita , Mangalampalli Sravani , Huynh Christina J. , Blanco Carmina C. , Lin Jack T. , Garrison Brian S. , Lee Philip , Lu Timothy K. , Lee Gary 
Published: September 2020

Abstract
While immunotherapies based on single recombinant cytokines such as IL12 and IL21 have shown great promise in preclinical models of solid tumors, clinical translation has proven challenging due to limited mechanisms of action, narrow therapeutic windows upon systemic administration, and short half-lives resulting in poor pharmacokinetics and distribution. Thus, there is a need for tumor-localized cytokine therapies capable of driving sustained efficacy with a wide therapeutic window.
SENTI-101 is a cell-based immunotherapy comprising allogeneic bone marrow-derived mesenchymal stromal cells (BM-MSCs) genetically modified to express IL12 and IL21. Consistent with prior studies, we demonstrated that SENTI-101 innately homes to disseminated tumors in the peritoneal cavity and induces durable anti-tumor responses and immune memory in various preclinical models of peritoneal tumors.
In this study, we investigated the mechanisms of action of SENTI-101. Our results demonstrate that the IL12 and IL21 combination elicits pleiotropic and complementary effects that drive a multi-modal immune response across various steps of the cancer immunity cycle.
Treatment of preclinical murine models of peritoneal tumors (e.g., CT26 and B16F10) with SENTI-101 significantly increased the local production of IFNg by more than 40-fold (p&lt;0.02). Concurrently, mice treated with SENTI-101 had significantly increased levels of cytokines and chemokines such as CXCL9 (p&lt;0.02), which have previously been associated with better prognosis and response to immunotherapy in multiple cancer types. We used flow cytometry and multiplexed IHC to characterize the immune landscape in response to SENTI-101. The number of antigen-presenting cells (F4/80negCD11c+MHC-II+CD103+) more than doubled in peritoneal lymph nodes 72 h after treatment with SENTI-101 (p=0.016). We also observed an increase in pSTAT1 positivity in the myeloid compartment, indicating a favorable immune phenotype. This change was accompanied by an increase in T-cell infiltrates into tumors (p=0.0003) that were in close proximity with B-cells and that were organized in tertiary lymphoid structures, which are known to correlate with improved prognosis in cancer patients. T-cell activation markers (CD38, CD25, IFNg, GranzymeB) also increased by more than 6 times (p=0.015) in the tumor microenvironment (TME) and peritoneal fluid after treatment with SENTI-101. In accordance with increased T-cell infiltration and activation in the TME, SENTI-101 showed a synergistic anti-tumor effect when combined with checkpoint inhibitor anti-PD1.
Overall, our preclinical studies show that SENTI-101 modulates the tumor immune landscape via multiple complementary modes of action, resulting in long-term anti-tumor immunity. Furthermore, this work demonstrates the therapeutic potential of tumor-localized cell therapies armed with gene circuits expressing combinatorial immune effectors to trigger a multi-factorial anti-tumor response.
Citation Format: Alba Gonzalez, Frances D. Liu, Archana Nagaraja, Alyssa Mullenix, Russell M. Gordley, Daniel O. Frimannsson, Anissa Benabbas, Chen-Ting Lee, Tiffany A. Truong, Allison Quach, Mengxi Tian, Rowena Martinez, Rishi Savur, Alyssa Perry-McNamara, Don-Hong Wang, Ori Maller, Dharini Iyer, Ashita Magal, Sravani Mangalampalli, Christina J. Huynh, Carmina C. Blanco, Jack T. Lin, Brian S. Garrison, Philip Lee, Timothy K. Lu, Gary Lee. SENTI-101, a novel genetically modified allogeneic cell product expressing IL12 and IL21, elicits a tumor-localized, robust, and multimodal immune response in preclinical models of solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4246.