The CDK4/6 inhibitor dalpiciclib augments the antitumor efficacy of enzalutamide in preclinical models of castration-resistant prostate cancer through inhibition of MCM4-mediated DNA replication.

Castration-resistant prostate cancer (CRPC) is a fatal malignancy often associated with alterations in cell cycle regulation, particularly within the Cyclin/CDK/RB axis. Despite ongoing clinical trials assessing CDK4/6 inhibitors in prostate cancer, clinical evidence remains limited. Although the androgen receptor (AR) inhibitor enzalutamide (ENZ) initially demonstrates therapeutic efficacy, resistance develops over time, and monotherapy offers limited antitumor benefits, highlighting the need for effective combination therapies. In this study, pharmacological profiling, genetic dependency analysis, RNA sequencing, and functional validation were conducted across various in vitro and in vivo preclinical CRPC models. The combination of ENZ and the CDK4/6 inhibitor dalpiciclib (DAL) exhibited potent antitumor activity in CRPC cell lines, a cell-derived xenograft (CDX) model, and a lymphatic metastatic model. Moreover, ENZ plus DAL inhibited cell cycle progression, migration, and DNA replication, while promoting apoptosis in CRPC cells. Mechanistically, ENZ blocked AR-mediated transcriptional activation of MCM4, a critical component of the DNA helicase complex, thereby enhancing the effect of CDK4/6 inhibition on DNA replication and inducing a pronounced synergistic antitumor response. These results suggest that the ENZ-DAL combination is a promising therapeutic approach that warrants further clinical evaluation in CRPC patients.