Adenovirus-PSA vaccination in recurrent and castration-resistant prostate cancer: Phase II trial interim results.

Abstract

e15070 Background: Our prior phase I adenovirus/PSA vaccine trial in patients with advanced CRPC showed the safety of this approach. We are currently conducting two phase II trials for patients with rising PSA after local therapy and for patients with CRPC and small amount of disease bulk to determine toxicity, immune response, and outcomes. Methods: In Protocol #1 men with rising PSA after local therapy and negative bone scan and CT are randomized to vaccine alone at days 0, 30, and 60 or vaccine 14 days after the initiation of androgen deprivation therapy (ADT). In Protocol #2 men with CRPC and negative bone scan (or positive bone scan with slow PSADT and PSA < 10) receive the vaccine using the same 3 injections schedule. Each injection consists of 10E8 pfu of the Ad/PSA vaccine suspended in a collagen matrix. Results: To date 20 patients have been enrolled in both protocols and have been followed a median of 10.5 months. The median age is 70 years, and median enrollment PSA levels are 1.45 ng/mL in Protocol #1 and 8.70 ng/mL in Protocol #2. Median duration of follow-up at this time is 10.5 months. Preliminary results show that 77% of the patients in both protocols demonstrated anti-PSA T cell responses (by Ellispot) above preinjection levels and 72% of patients demonstrated an increase in PSA doubling time (100% of patients in protocol # 1 and 62% of patients in protocol # 2). No grade 3 or 4 toxicities have been seen to date. Progression-free and overall survival data is premature at this time, with one patient deceased from disease progression in the CRPC trial to date. Conclusions: Early results from the first fifteen 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. No significant financial relationships to disclose.