An inhibitor of PCNA; binds to PCNA trimers (Kd = 0.41 μM) and reduces the level of chromatin-associated PCNA in PC3 cells; preferentially inhibits growth of a variety of human and mouse cancer cell lines (IC50s = 0.05-0.3 μM) over non-transformed cells (IC50s = 0.99-2 μM); reduces tumor growth in an LNCaP prostate cancer mouse xenograft model at 10 mg/kg administered five days per week for two weeks