A formulation of a plasmid DNA encoding an inactivated form of the carcinogen activator cytochrome P450 1B1 (CYP1B1) encapsulated in biodegradable poly-DL-lactide-coglycolide microparticles with potential antineoplastic activity. CYP1B1, an extrahepatic monooxygenase of the cytochrome P450 family, is overexpressed in many cancers with only restricted expression in normal tissues. Vaccination with ZYC300 may stimulate the immune system to elicit a cytotoxic T lymphocyte (CTL) response against the tumor associated antigen CYP1B1, thereby causing lysis of tumor cells expressing CYP1B1. [ ]