One of the approaches that can be applied to enhance targeted-tissue specificity and to improve drug delivery to selected cell types is the design of prodrugs . Prodrugs are themselves inactive, but through chemical or enzymatic cleavage, the bioactive form of drugs can be released. Also, by exploiting tumor-intrinsic factors, a cancer-specific release might be obtained . One of these factors is hypoxia, which is a deficiency in oxygen supply reaching the tissues and contributes to the chemotherapeutic resistance of tumors . Hypoxia induces high expression of reductase enzymes; therefore, hypoxia has evolved as a promising approach in the design of anticancer agents . Additionally, several hypoxiaactivated chemotherapeutic agents are currently in clinical development . The directed enzyme prodrug therapy (DEPT) principle is one of the strategies that can be applied for the selective targeting of exogenous enzymes to cancer cells. This approach allows site-specific release of the active drug by an exogenous enzyme that is either linked to an antibody (ADEPT) or encoded by a gene that is targeted to the tumor site (GDEPT) . Nitroreductase (NTR) is one of the enzymes that can be used for the DEPT approach . NTR is a bacterial oxygen-insensitive homodimeric flavoenzyme encoded by the nfsB gene . The NTR catalyzes the reduction of the nitro group of various nitroaromatic substrates such as 4-nitrobenzyl and 1-methyl-2-nitroimidazolyl carbamates of cytotoxic amines to the corresponding nitroso intermediate, which is further reduced to the hydroxylamine derivative, followed by self-immolation and fragmentation to release the active inhibitor, in addition to a Michael acceptor and CO2 as side products (Fig. ) .