Definition

The racemic form of a synthetic quinoxaline phenoxypropionic acid derivative with antineoplastic properties. XK469R selectively inhibits topoisomerase II by stabilizing the enzyme-DNA intermediates in which topoisomerase subunits are covalently linked to DNA through 5-phosphotyrosyl linkages, thereby interfering with DNA repair and replication, RNA and protein synthesis. This agent possesses unusual solid tumor selectivity and activity against multidrug-resistant cancer cells. XK469R is more water soluble and active than the pure isomers, R(+)XK469 and S(-)XK469.