Abstract A022: Therapeutic inhibition of TREX1 elicits type I interferon–mediated antitumor immunity with minimal autoimmune toxicity

Abstract Background: Three-prime repair exonuclease 1 (TREX1) is a cytosolic DNase that suppresses cGAS–STING–mediated type I interferon (IFN-I) responses by degrading self-DNA. While this function is essential for immune homeostasis—highlighted by the fact that TREX1 loss causes autoimmune disorders such as Aicardi-Goutières syndrome—many cancers exploit TREX1 upregulation to evade immune surveillance, particularly following genotoxic therapies. Therapeutically inhibiting TREX1 offers an opportunity to re-engage IFN-I–driven antitumor immunity, but it also raises concerns about triggering immune-related adverse events. Here, we aimed to define the therapeutic benefit and immune safety of targeting TREX1 in vivo. Methods: We employed a multimodal strategy to assess the therapeutic potential and safety of targeting TREX1. First, we conducted a high-throughput screen to identify small-molecule inhibitors of TREX1 and evaluated lead compound #296 in syngeneic mouse tumor models. Second, we tested TREX1-deficient tumor cells as autologous cancer vaccines. Finally, we generated inducible whole-body Trex1 knockout mice to model systemic TREX1 inhibition and assess its long-term immune safety. Results: Lead compound #296 selectively inhibited TREX1 enzymatic activity, triggered IFN-I signaling in tumor cells, and significantly suppressed tumor growth in multiple syngeneic mouse models. Treatment with #296 enhanced CD8+ T cell infiltration and reversed resistance to anti–PD-1 therapy in poorly immunogenic B16-F10 melanoma, without inducing systemic inflammation or elevated CRP. TREX1-deficient tumor cells activated tumor-intrinsic cGAS–STING signaling and functioned as effective autologous cancer vaccines, eliciting durable systemic antitumor immunity that protects against both tumor rechallenge and metastasis. Importantly, systemic TREX1 deletion in adult mice using an inducible knockout model led to sustained tumor suppression across diverse tumor models, while maintaining immune safety over 6 months with minimal immune toxicity. Conclusions: Our study reveals TREX1 as a druggable target to stimulate IFN-I–driven antitumor immunity. Across three distinct therapeutic approaches—small-molecule inhibitor, cell-based vaccination, and systemic gene knockout—TREX1 targeting elicited durable tumor control with minimal autoimmune toxicity, supporting its translational potential as a safe and effective cancer immunotherapy. Citation Format: Cong Xing, Nan Yan. Therapeutic inhibition of TREX1 elicits type I interferon–mediated antitumor immunity with minimal autoimmune toxicity abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Mechanisms of Cancer Immunity and Cancer-related Autoimmunity; 2025 Sep 24-27; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(9 Suppl):Abstract nr A022.