A novel 5-FU derivative chemotherapy: a promising pan-cancer treatment to improve antitumor efficacy and overcome therapy resistance

Abstract Management of advanced solid cancers remains challenging, particularly after the development of therapeutic resistance. Here, we synthesized a library of phosphonium-substituted 5-fluorouracil (5-FU) derivatives and evaluated their anticancer activity across multiple tumor models. Among fourteen compounds, EB-18 emerged as the lead candidate, displaying sub-micromolar cytotoxicity in both androgen receptor (AR)-negative PC-3 and AR-positive C4-2 castration-resistant prostate cancer (CRPC) cells and activity across several other malignant solid-tumor cell lines. EB-18 inhibited proliferation, migration, and three-dimensional spheroid growth and induced cell-cycle perturbation and apoptosis. Mechanistic studies in vitro showed that EB-18 disrupted HSP27-associated survival signaling, promoted ubiquitination and proteasome-dependent degradation of DDX5, and suppressed AKT/mTOR signaling. In addition, EB-18 also increased γ-H2AX and reduced Ku70/Ku80 expression, consistent with perturbation of the DNA damage response. AR downregulation was additionally observed in AR-positive C4-2 cells. EB-18 retained activity in patient-derived organoids and multidrug-resistant CRPC cells and significantly inhibited tumor growth in PC-3 xenografts. Collectively, these findings identify EB-18 as a promising anticancer candidate with activity in treatment-resistant CRPC and provide a rationale for further pharmacological, mechanistic, and translational evaluation. Graphical Abstract EB-18, a novel 5-FU derivative, demonstrates superior anticancer activity compared with 5-FU and clinically used chemotherapies (Docetaxel, Cabazitaxel, and Mitoxantrone) across multiple preclinical models, including 2D/3D CRPC cell models, prostate cancer patient-derived organoids, PC-3 xenografts, and multidrug-resistant PC-3 cells, supporting its potential to overcome acquired drug resistance. Mechanistically, EB-18 exerts multifaceted antitumor effects by disrupting the HSP27/DDX5 axis and DNA damage-response machinery, promoting DNA damage and apoptosis, while suppressing AKT/mTOR prosurvival signaling. In AR-positive CRPC cells, EB-18 additionally reduces AR expression. Together, these effects inhibit cancer cell proliferation and survival and support EB-18 as a promising therapeutic candidate for treatment-resistant cancer.