FL-118

Addition of fluorine atoms into chemical compounds is a validated strategy to enhance their physical, chemical and biological properties. In this study, FL118, a novel camptothecin-related small molecule known for its unique mechanism of action and superior antitumor efficacy, was utilized as a foundational drug platform. By replacing the hydrogen atom at position 7 of FL118 with a fluoroaryl group, a diverse array of FL118 derivatives were synthesized. Our investigations revealed that the majority of these newly synthesized compounds exhibited improved cytotoxicity compared to FL118, with some demonstrating enhanced in vivo antitumor efficacy. Among these derivatives, compound 7h stood out and was subjected to detailed analysis. Compound 7h demonstrated a remarkable ability to inhibit colorectal cancer (CRC) cell colony formation and cell migration, while also promoting reactive oxygen species (ROS) production and CRC cell apoptosis. Notably, our studies unveiled that the presence of DDX5 could modulate Topoisomerase I (Top1) activity, a process effectively reversed by a low concentration of 7h, but not SN38. Moreover, only 7h was able to decrease DDX5 expression, SN38 was not. Molecular docking studies further supported the binding of 7h to DDX5. Interestingly, although both 7h and SN38 exhibited similar inhibitory effects on Top1 activity, only 7h, and not SN38, could inhibit DDX5. These findings not only pave the way for deeper mechanistic explorations of FL118 and its derivatives in cancer research but also position the identified compound 7h as a promising candidate for further development.

The treatment of bladder cancer is limited by low drug efficacy and drug resistance. Hence, this study aimed to screen and identify potential drug precursors and investigate their mechanism of action. A set of camptothecin derivatives showing high anti-tumor potential was selected from early-stage research or literature and synthesized to construct a compound library. A total of 135 compounds were screened in T24 and J82 cells, revealing that FL118 significantly inhibited the proliferation of GC (gemcitabine + cisplatin)-sensitive/insensitive cells. FL118 exhibited excellent penetration and killing ability in organoids and three GC-insensitive patient-derived xenografts. Chemical proteomic and docking calculations were employed to identify binding proteins, indicating that FL118 can bind into H2A.X and its entwined DNA. The results of Cellular thermal shift assay and surface plasmon resonance (K_d = 3.77E-6) support the above findings. Fluorescence localization revealed widespread binding of FL118 within the cell nucleus. Furthermore, WB showed that FL118 increased cellular DNA damage, resulting in significant cell cycle inhibition. The binding of FL118 to H2A.X hindered the damage repair process, leading to apoptosis. Controllable adverse reactions were observed in mice treated with FL118. In conclusion, FL118 may be a superior anti-bladder cancer compound that acts as a molecular glue binding to both H2A.X and DNA. The resistance mediated by the DNA damage repair to DNA damage caused by GC regimen can be reversed by FL118. This distinct mechanism of FL118 has the potential to complement existing mainstream treatment approaches for bladder cancer.