Abstract B025: The innate immune checkpoint TREX1 is a safe, effective, and druggable target for cancer immunotherapy

Abstract Background: The DNA exonuclease TREX1 acts as an innate immune checkpoint by degrading cytosolic DNA and suppressing cGAS–STING–IFN-I signaling. While cancers exploit TREX1 to evade innate immune sensing, its therapeutic potential has not been fully explored. We investigated multiple modalities for therapeutically targeting TREX1 and demonstrated their efficacy and immunologic safety. Methods: A high-throughput screen of 295,000 compounds using a cell-free DNase assay identified small-molecule inhibitors of TREX1. Lead compound #296 was evaluated for IFN-I induction, tumor growth inhibition, and synergy with immune checkpoint blockade (ICB). In parallel, TREX1-knockout tumor cells were tested as autologous cancer vaccines. An inducible whole-body Trex1 knockout mouse model was developed to mimic systemic TREX1 inhibition and assess therapeutic efficacy and immune safety. Results: Compound #296 selectively inhibited TREX1 and robustly activated IFN-I signaling in cancer cells, resulting in CD8+ T cell infiltration and tumor regression. It synergized with anti–PD-1 therapy in resistant B16-F10 melanoma models without causing 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. Systemic TREX1 deletion in adult mice using an inducible knockout model significantly inhibited growth of MC38, E0771, LLC, and B16-F10 tumors, and slowed tumor metastasis, while maintaining immune safety over 6 months with minimal immune-related toxicity. Conclusions: Our study reveals TREX1 as a druggable innate immune checkpoint and presents three distinct and complementary therapeutic strategies: small-molecule inhibitors, tumor-cell-based vaccines, and systemic inactivation. Each approach elicited potent antitumor responses with favorable immune safety, establishing TREX1 as a promising target to reprogram the tumor-immune microenvironment and overcome resistance in immunologically cold tumors. Citation Format: Cong Xing, Nan Yan. The innate immune checkpoint TREX1 is a safe, effective, and druggable target for cancer immunotherapy [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr B025.