Novel prodrugs which are activated to cytotoxic alkylating agents by carboxypeptidase G2.

The synthesis of three novel prodrugs, 4-[bis[2-(mesyloxy)ethyl]amino]benzoyl-L-glutamic acid (7), 4-[(2-chloroethyl)[2-(mesyloxy)ethyl]amino]benzoyl-L-glutamic acid (8), and 4-[bis(2-chloroethyl)amino]benzoyl-L-glutamic acid (9), for use as anticancer agents, is described here. Each is a bifunctional alkylating agent in which the activating effect of the ionized carboxyl function is masked through an amide bond to the glutamic acid residue. These relatively inactive prodrugs are designed to be activated to their corresponding nitrogen alkylating agents (10, 11, and 12, respectively) at a tumor site by prior administration of a monoclonal antibody conjugated to the bacterial enzyme carboxypeptidase G2 (CPG2). The viability of two different tumor cell lines was monitored with each prodrug in the presence of CPG2. All three compounds showed substantial prodrug activity--with conversion to the corresponding active drug leading to greatly increased cytotoxicity.