Dai, Xing-JieLi, YingXiong, Xiao-PengWang, Jun-JieLu, Guo-LiangLi, YanLiu, Cong-JunWang, NingZheng, Yi-ChaoYang, Zheng-HongWang, Bo2026-02-262026-02-262026-02-12Chinese Chemical Letters, ISSN: 1001-8417 (Print), Elsevier BV, 112523-112523. doi: 10.1016/j.cclet.2026.1125231001-8417http://hdl.handle.net/10292/20685Lysine-specific demethylase 1 (LSD1), the first identified histone lysine-specific demethylase, plays a crucial role in mediating immune responses in gastric cancer. Most LSD1 inhibitors undergoing clinical trials are irreversible, which has driven significant interest in developing structurally diverse reversible inhibitors. In this study, we present a potent 1,3,5-triazine-based LSD1 inhibitor, XP-2, discovered through high-throughput screening (HTS) of our in-house compound library and subsequent structure-activity relationship (SAR) studies, exhibiting a half maximal inhibitory concentration (IC50) of 0.116 μmol/L. XP-2 enhanced the susceptibility of gastric cancer cells to T cell-mediated cytotoxicity by downregulating programmed cell death ligand 1 (PD-L1) expression, thereby disrupting the programmed cell death protein 1 (PD-1)/PD-L1 interaction. Furthermore, XP-2 significantly inhibited the proliferation of gastric cancer cells without inducing notable toxicity. Pharmacokinetic evaluation revealed favorable oral exposure and a moderate half-life in mice. In conclusion, this study provided a promising LSD1 inhibitor with a novel scaffold and promising pharmacokinetic properties, supporting its further development as an immunomodulator for gastric cancer treatment.This is the Author's Accepted Manuscript of an article published in Chinese Chemical Letters © 2026 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. The Version of Record will be available at DOI: 10.1016/j.cclet.2026.11252334 Chemical SciencesStomach CancerImmunotherapyDigestive DiseasesOrphan DrugBiotechnologyCancerRare Diseases5.1 PharmaceuticalsCancer03 Chemical SciencesGeneral Chemistry34 Chemical sciencesJournal ArticleOpenAccess10.1016/j.cclet.2026.112523