GTSE1-IN-1 (compound Y18), an orally active GTSE1 inhibitor, exhibits notable anticancer properties. It effectively represses the proliferation of cancer cells by downregulating GTSE1 transcription and expression, which leads to DNA damage and promotes persistent cell cycle arrest and cellular senescence. Moreover, GTSE1-IN-1 substantially reduces the adhesion, migration, and invasion of colorectal cancer HCT116 cells and non-small cell lung cancer A549 cells in vitro.