Abstract A45: Preliminary results of a phase 1 clinical trial of a PSA, IL-2, GM-CSF containing prostate cancer vaccine in PSA defined biochemical recurrent prostate cancer patients

Immunotherapy for cancer has had two main approaches that have led to clinical applications. The first is stimulating immune responses to tumor cells with cytokines or cellular immunotherapy and the second is blocking tumor immune evasion and the associated inhibition of T-cell activation with antibodies to the CTLA-4 receptor, PD-1 receptor or PD-L1. We have taken a different approach and have developed therapeutic cancer vaccines that are a combination of tumor antigens (proteins overexpressed by tumors) with biological adjuvants (the cytokines IL-2 and GM-CSF). This study is a Phase 1a/1b clinical trial of a PSA/IL-2/GM-CSF vaccine in recurrent prostate cancer in hormone-naive and hormone-independent patients. Major inclusion criteria include adenocarcinoma of the prostate, rising serum PSA and no measurable disease. Phase 1a examines the rate of dose limiting adverse events (DLAEs) in an initial course of 6 vaccinations (“induction vaccination”). The patients will receive intradermal injections of the PSA/IL-2/GM-CSF vaccine at weeks 1, 2, 3, 7, 11 and 15. Enrollment of the twenty patients in the Phase 1a has been completed. To date, 14 patients in the Phase 1a portion of the trial have received all 6 vaccines. Twelve of the 15 patients who have received vaccines have increased immune responses to PSA in a lymphocyte blastogenesis assay by week 19. After 6 vaccines, 9 of 14 patients had an increase in the doubling time of their serum PSA, suggesting a slowing of the progression of the cancer. Median follow up after the first vaccine is 33 months. None of the patients vaccinated in the Phase 1a portion have had a DLAE. Citation Format: Jonathan F. Head, Gregory A. Daniels, Michelle McKinney, Weg Ongkeko, Kyoko Sakamoto, Jessica Wang-Rodriguez. Preliminary results of a phase 1 clinical trial of a PSA, IL-2, GM-CSF containing prostate cancer vaccine in PSA defined biochemical recurrent prostate cancer patients [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A45.