DB-2B, a Novel and Selective STAT3 Inhibitor Inhibits Colorectal Cancer Progression In Vitro and In Vivo

Activation of signal transducer and activator of transcription 3 (STAT3) is implicated in tumor progression and correlates with poor prognosis and reduced survival. In colorectal cancer (CRC), STAT3 activation serves as a key indicator of unfavorable outcomes. However, the scarcity of clinically available STAT3 inhibitors hinders the development of personalized treatment strategies targeting STAT3. Therefore, we aimed to develop a novel STAT3 inhibitor based on the molecular structure of STAT3 and our previously reported STAT3 inhibitor LY17 to inhibit the progression of CRC. The binding of the novel STAT3 inhibitor DB-2B to STAT3 was confirmed by computational docking, surface plasmon resonance, isothermal titration calorimetry, and cellular thermal shift assays. Western blotting and immunofluorescent staining demonstrated that DB-2B specifically inhibited STAT3 activation and nuclear translocation. In vitro studies revealed that DB-2B significantly suppressed proliferation, induced apoptosis, arrested cell cycle progression, and attenuated stemness by inhibiting STAT3 activation and its downstream signaling pathways. In vivo, DB-2B exhibited favorable oral bioavailability and safety, while significantly inhibiting the progression of CRC. Collectively, this study presents DB-2B as a promising small-molecule STAT3 inhibitor for the targeted treatment of CRC.