Abstract A096: Blockade of LAIR1-collagen interaction enhances the therapeutic activity of BiTE-secreting T cells in ovarian cancer
Authors: Werner Sarah , Gaulin Nicole , Chiello Jessie , Giridharan Theja , Khan Anm Nazmul , Suzuki Sora , Hess Suzanne , Langermann Sol , Zsiros Emese , Segal Brahm H. , McGray A.J. Robert 
Published: March 2024

Abstract
Introduction: The tumor microenvironment (TME), abundant with collagen produced by cancer associated fibroblasts (CAFs), plays a critical role in evading the immune system and limiting the efficacy of cell therapies. High levels of collagen and CAF expression correlate with malignant potential, decreased T cell accumulation, and overall unfavorable clinical outcomes in ovarian cancer (OC). Finding ways to address this immunosuppressive TME is therefore critical to improving therapeutic options. We recently reported on the therapeutic potential of adoptively transferred T cells engineered to secrete a folate receptor alpha (FRα)-targeted bispecific T cell engager (FR-B T cells) to target a tumor antigen commonly overexpressed in OC. Transcriptional profiling following ACT revealed that effector-like FR-B T cells (FR-BE T cells) upregulated genes associated with extracellular matrix interaction, suggesting interaction with the tumor stroma may limit antitumor immunity by FR-B T cells. Our goal was to improve the effectiveness of FR-B T cells by inhibiting LAIR-1, a widely present immune checkpoint receptor that sends T cell inhibitory signals after binding to collagen-like domains, leading to T cell exhaustion. We hypothesized that interrupting the LAIR1-collagen pathway using a LAIR1 decoy (NC410, supplied by NextCure Inc.) could amplify the FR-BE T cell effector function, thereby improving the response. Methods: We utilized in vitro co-culture assays to understand the phenotype and mechanistic changes occurring at the level of the T cell/tumor interface when exposed to collagen, as well as effects of LAIR 1 pathway blockade with the addition of NC410. In vivo murine models were used to determine disease progression and overall survival (OS) following treatment with bispecific T cell engager-armed T cells ± LAIR1 blockade. Results: Phenotypic analysis of FR-B T cells revealed elevated LAIR-1 expression on FR-BE T cells. FRα+ OC lysis by FR-BE T cells was diminished in the presence of collagen, suggesting LAIR-1 signaling can suppress tumor attack. In vitro, the addition of NC410 enhanced the activity of FR-BE T cells when exposed to collagen, improving both FRα+ target cell lysis and partially restoring the production of IFN-γ by FR-BE T cells. In vivo, the combination of NC410 with FR-BE T cells led to improved tumor control compared to FR-BE T cell therapy alone. Conclusions: Our results highlight understanding the interactions between infiltrating immune cells and the immunosuppressive TME to better design combination therapies that improve duration and magnitude of immune attack on tumors. By blocking T cell/stromal interactions, FR-B T cell therapy can be further enhanced, creating a promising opportunity to improve the impact of adoptive cell therapy in OC.
Citation Format: Sarah Werner, Nicole Gaulin, Jessie Chiello, Theja Giridharan, Anm Nazmul Khan, Sora Suzuki, Suzanne Hess, Sol Langermann, Emese Zsiros, Brahm H. Segal, A.J. Robert McGray. Blockade of LAIR1-collagen interaction enhances the therapeutic activity of BiTE-secreting T cells in ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr A096.