In vitro and in vivo prodrug therapy of prostate cancer using anti-gamma-Sm-scFv/hCPA fusion protein.

Background: Raising selectivity to tumor cells is a major challenge for most chemotherapy drugs. One of approaches to realizing this goal is antibody-directed enzyme prodrug therapy (ADEPT). This study was done to investigate the curative effect of a new ADEPT system for the treatment of prostate cancer.
Methods: Methotrexate (MTX) prodrugs were synthesized and anti-seminoprotein (SM) single-chain antibody/human carboxypeptidase-A fusion protein (scFv/hCPA) was prepared. Therapeutic effects of this ADEPT system were evaluated.
Results: The synthesis of prodrugs was successful and the prodrugs were confirmed no cytotoxicity, but hydrolysis with tumor-targeted scFv/hCPA fusion protein gave 1,000-fold higher cytotoxicity than MTX-alpha-Phe only. Cell cycle assays showed that tumor cells were arrested in the S phase after ADEPT treatment; furthermore, tumors were inhibited significantly in scFv/hCPA and MTX-alpha-Phe treated mice.
Conclusions: Our results suggest that targeted activation cytotoxicity against established prostate cancer by scFv/hCPA mediated ADEPT is tumor-specific and has no systemic toxicity in vitro and in vivo.