Background: We have previously reported the results from a phase I trial using a PAP-encoding DNA vaccine (pTVG-HP) in men with PSA-recurrent, non-metastatic, non-castrate, prostate cancer (clinical stage D0/M0). In that trial, patients received six intradermal immunizations, with GM-CSF co-administered as an adjuvant, over 12 weeks. No significant adverse events were detected, and CD4+ and CD8+ T cell immune responses to the PAP target antigen were elicited. The development of persistent Th1-type immunity was associated with favorable changes in PSA doubling time. A second trial, conducted in men with PSA-recurrent, non-metastatic, castrate-resistant prostate cancer (D0.5/M0) evaluated this vaccine administered over a 2-year period. In that trial there were no significant adverse events, the development of persistent Th1-biased PAP-specific immunity was detected, and many patients experienced a prolongation of PSA doubling time. Based on these results, we are currently conducting a multi-center trial using pTVG-HP plus GM-CSF adjuvant, versus GM-CSF adjuvant only, in patients with stage D0/M0 prostate cancer. Methods: Patients with non-castrate, non-metastatic prostate cancer (negative CT and bone scans), with rising PSA and a doubling time of < 12 months, are being randomly assigned to receive pTVG-HP + GM-CSF versus GM-CSF adjuvant. Treatments are being delivered intradermally every 2 weeks x 6, and then quarterly for up to 24 months. The primary endpoint is 2-year metastasis-free survival. Secondary endpoints include median progression-free survival, and determining whether immunization affects PSA doubling time. Laboratory endpoints include determining whether PAP-specific T-cell immunity is associated with progression-free survival. The trial was expanded in 2014 to include a total of 106 patients allowing for further exploratory biomarker analyses and to increase the statistical power, now enabling a > 90% power to detect an anticipated difference of 40% versus 70% in 2-year metastasis-free survival at the one-sided 5% significance level. Clinical trial information: NCT01341652