Abstract CT208: Preliminary results of a phase II trial of an adenovirus/PSA vaccine in men with recurrent prostate cancer

Abstract

Abstract Introduction and Objectives: A phase II clinical trial of an adenovirus/PSA (Ad/PSA) vaccine was carried out in men with recurrent prostate cancer using two protocols. The objectives of the study were to determine whether the vaccine produced beneficial immune and clinical responses in men with a low burden of tumor. Methods: In Protocol #1 men with recurrent prostate cancer following definitive initial treatment for their disease were placed in one of two arms: Arm A; men received the vaccine alone at days 0, 30, and 60; Arm B; men received the vaccine 14 days after the initiation of androgen deprivation therapy (ADT). In Protocol #2 men with hormone refractory disease received the vaccine alone using the same 3 injection schedule. Each injection consists of 108 pfu of the Ad/PSA vaccine suspended in a collagen matrix. All patients returned at regular intervals for physical, chemical, radiologic, and immunologic evaluations. Results: We enrolled all of our targeted 82 patients, 50 in protocol 1 (25 Arm A, 25 Arm B) and 32 in protocol 2. All patients have been followed a minimum of 12 months with the longest being over 6 years. Eighty nine percent (89%) of all patients produced anti-PSA T cell immune responses; 71% in protocol 1 Arm A, 100% in protocol 1 Arm B, and 100% in protocol 2. Clinically, 58% of patients in protocol 1 Arm A and 75% of patients in protocol 2 demonstrated a decrease in serum PSA or an increase in PSA doubling times (PSADT). As of the submission date the PSA levels of 2 patients declined to 0.07 ng/ml and undetectable (<0.03). Conclusions: Preliminary results of patients thus far studied in a phase II clinical trial of the Ad/PSA vaccine are very encouraging, demonstrating both immunologic and clinical responses to the 3-vaccination therapy. PSA responses indicate at least a decline in the growth and perhaps a destruction of recurrent prostate tumors in men immunized in two separate protocols. Data collection continues that include completion of immune assays on all 82 patients as well as monitoring PSA levels, PSADT, and radiologic changes. Citation Format: David M. Lubaroff, Daniel Vaena, James Brown, Kenneth Nepple, Pamela Zehr, Karen Griffith, Erica Brown, Julie Eastman, Gideon Zamba, Richard Williams. Preliminary results of a phase II trial of an adenovirus/PSA vaccine in men with recurrent prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT208. doi:10.1158/1538-7445.AM2015-CT208