Strategies for enzyme/prodrug cancer therapy.

The selective activation of prodrug(s) in tumor tissues by exogenous enzyme(s) for cancer therapy can be accomplished by several ways, including gene-directed enzyme prodrug therapy (GDEPT), virus-directed enzyme prodrug therapy (VDEPT), and antibody-directed enzyme prodrug therapy (ADEPT). The central part of enzyme/prodrug cancer therapy is to deliver drug-activating enzyme gene or functional protein to tumor tissues, followed by systemic administration of a prodrug. Although each approach (GDEPT, VDEPT, and ADEPT) has been tested in clinical trials, there are some potential problems using the current delivery systems. In this article, disadvantages and advantages associated with each approach (GDEPT, VDEPT, and ADEPT) and future perspective for improving current systems are discussed.