Phase I - Pre-Radical Prostatectomy RTVP-1 Gene Therapy for Prostate Cancer

The purpose of this study is to conduct a Phase I clinical trial involving in situ RTVP-1 gene therapy for prostate cancer. We will conduct necessary safety evaluations on a new adenovirus that contains the human genes for RTVP-1. This virus will then be evaluated for safety in men with prostate cancer prior to radical prostatectomy. Based on the preclinical data, we hope that this treatment will induce not only a local cytotoxic and antiangiogenic effect but also, a systemic antitumor immune response capable of eradicating micrometastatic disease (the reason for recurrence in many of these patients).

The population selected for this study includes patients with locally advanced and/or poorly differentiated tumors. These patients have an unacceptably high failure rate when treated by radical prostatectomy alone (over 50% fail within 5 years). The pattern of failure varies. While some patients present with a local recurrence, many have both a local recurrence and distant metastases, or just distant metastases. It is reasonable to assume that many, if not most of these patients, actually harbor micrometastases, present but undiagnosed clinically, at the time of their radical prostatectomy. Our hypothesis is that the cytotoxic, proapoptotic, antiangiogenic and immune stimulatory activities of in-situ RTVP-1 gene therapy will lower the incidence of local tumor recurrences when given to patients prior to surgery. The second part of our hypothesis is that RTVP-1 gene therapy will induce a systemic anti-tumor immune response, which will eliminate pre-existing micrometastases in some of these patients and lower the overall failure rate. While this Phase I study is not designed to answer these questions, we hope to obtain mechanistic evidence in support of this hypothesis. A Phase II study will then be proposed (and properly powered), to study the efficacy of this approach. Based on our experience with HSV-tk and GCV in-situ gene therapy, it appears that maximal immune stimulation occurs about 2 weeks following vector injection. Furthermore, repeat injections of an adenoviral vector do not result in excess toxicity or in the generation of anti-adenoviral antibodies sufficient to suppress vector activity. We propose here an intraprostatic injection of RTVP-1 in an adenoviral vector 4-6 weeks prior to radical prostatectomy, in order to allow full expression of the gene therapy tissue effects.