Abstract 2692: An ongoing Phase II trial of an adenovirus/PSA vaccine for prostate cancer

Abstract

Abstract Introduction and Objectives: Our Phase I adenovirus/PSA vaccine trial has proved that this vaccine is safe. We are conducting a Phase II clinical trial with two separate protocols for patients with recurrent or hormone refractory prostate cancer assessing toxicity, immune responses, and changes in PSA levels. 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 receive the vaccine alone at days 0, 30, and 60; Arm B; men receive the vaccine 14 days after the initiation of androgen deprivation therapy (ADT). In Protocol #2 men with hormone refractory disease receive 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 return at regular intervals for physical, chemical, radiologic, and immunologic evaluations. Results: To date forty four patients have been enrolled and have been followed a median of 12 months. The patients have a median age of 71.3 years, and median enrollment PSA levels of 0.62 ng/ml in Protocol #1 and 5.45 ng/ml in Protocol #2. In our preliminary results at this early stage of the trial, 100% of the patients in Protocol #1 and 67% of the patients in Protocol #2 demonstrated anti-PSA T cell responses above preinjection levels. Sixty four percent of the patients demonstrated an increase in PSA doubling time (PSADT). Conclusions: In an attempt to follow up on the success of our Phase I clinical trial of the Ad/PSA vaccine we have initiated a Phase II trial to investigate the therapeutic efficacy of the vaccine in men with recurrent prostate cancer, either following definitive therapy prior to other treatments or hormone refractory. Early results from the first four four patients demonstrate the induction of anti-PSA T cells responses in a high percentage of the vaccinated patients and increase in PSADT in more than half of the patients. No serious vaccine-related toxicities have been identified in the patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2692. doi:1538-7445.AM2012-2692