A strategy for tumor-selective chemotherapy by enzymatic liberation of seco-duocarmycin SA-derivatives from nontoxic prodrugs Original Research Article

Immuno-conjugates obtained by linking enzymes with appropriate monoclonal antibodies, which bind to tumor-associated antigens, can be employed in a tumor-selective antibody directed enzyme prodrug therapy (ADEPT). For this strategy the glycosides 17a–c were prepared as prodrugs of CI-TMI 14 which is a structurally simplified analogue of the highly potent antitumor agent duocarmycin SA 2. Exposure of 17a–c to cultured carcinoma cells of line A549 displayed a very low toxicity; however, after addition of the corresponding enzymes and exposure for 24 h at prodrug concentrations of <0.1 μM the proliferation of the carcinoma cells was inhibited almost completely with ED50prodrug/ED50drug of up to 270 in the presence and in the absence of the enzyme. The synthesis of 17a–c was achieved by transformation of nitroanisidine 6 into 12 which was glycosidated to give 16a–c. Removal of the silyl groups, introduction of a chlorine atom and solvolysis of the acetal groups led to 17a–c, of which 17a and 17c are promising candidates for further elaboration.