Background: Patients with rapidly rising PSA alone after definitive therapy for prostate cancer are at high risk for metastatic progression and ultimately death from prostate cancer. This is a stage of disease for which there are no standard therapies, although androgen deprivation is often used. We have previously reported that a DNA vaccine encoding PAP (pTVG-HP) was safe and could elicit antigen-specific CD4+ and CD8+ T cells in this population (NCT00582140). Patients who developed persistent Th1-type immunity tended to have favorable changes in serum PSA doubling time. The safety, immunological activity, and changes in PSA doubling time were observed in a second pilot clinical trial evaluating different schedules of administration (NCT00849121).
Methods: 106 patients with high-risk PSA-recurrent prostate cancer, PSA doubling time < 12 months, and no metastases by standard radiographic imaging, are being randomized to DNA vaccine with GM-CSF adjuvant versus GM-CSF adjuvant alone in this multicenter trial (NCT01341652). The primary endpoint is 2-year radiographic progression-free survival (PFS). Secondary and exploratory endpoints include median PFS, predictive and early response immune biomarkers, association of T-cell immunity with PFS, and change in tumor growth rates as measured by PSA and quantitative bone imaging using NaF PET imaging.
Results: To our knowledge, this is the first randomized, phase II trial using an anti-tumor DNA vaccine. Enrollment is ongoing, but expected to be complete in 2015. The clinical and biomarker plan of evaluation will be presented, as well as descriptions of other pilot clinical trials ongoing with this DNA vaccine.
Citation Format: Douglas G. McNeel, Lawrence Fong, Emmanuel S. Antonarakis, Glenn Liu. Randomized phase II trial of a DNA vaccine encoding prostatic acid phosphatase (PAP) in patients with recurrent prostate cancer (NCT01341652). [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B147.
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