XK-469 (NSC 697887) is a synthetic quinoxaline phenoxypropionic acid derivative that possesses unusual solid tumor selectivity and activity against multidrug-resistant cancer cells. XK469 acts as a selective topoisomerase IIβ inhibitor. Other proposed mechanisms include XK469-induced inhibition of cyclin B1 ubiquitination and apoptosis via binding of the peripheral benzodiazepine receptor. A phase I study was performed to determine the safety and pharmacokinetics of XK469R in patients with various neoplasms.