Self-immolative anthracycline prodrugs for suicide gene therapy

Four novel potential prodrugs derived from daunorubicin (8, 10) and doxorub icin (12, 14) were designed and synthesized. They are self-immolative prodr ugs for suicide gene therapy activation by the enzyme carboxypeptidase G2 ( CPG2) subsequently releasing the corresponding anthracyclines, by a 1,6-eli mination mechanism. A mammary carcinoma cell line (MDA MB 361) was engineer ed to express CPG2 intracellularly (CPG2*) or extracellularly, tethered to the outer cell membrane (stCPG2(Q)3). The prodrugs derived from doxorubicin showed prodrug/drug cytotoxicity differentials of 21-fold (compound 12) an d 23-fold (compound 14). Prodrug 12 underwent an 11-fold activation when as sayed in the cell line expressing externally surface-tethered CPG2.