Antigen-Specific Immune Responses Through 24 Months In The Stand Trial: A Randomized Phase 2 Study Evaluating Optimal Sequencing Of Sipuleucel-T (Spin-T) And Androgen Deprivation Therapy (Adt) In Biochemically-Recurrent Prostate Cancer (Brpc)

171 Background: Sip-T is an autologous cellular immunotherapy targeting prostatic acid phosphatase (PAP), approved for treatment of asymptomatic/minimally symptomatic metastatic castration-resistant prostate cancer. STAND evaluates sequencing of sip-T and ADT in men with BRPC at high risk of metastases. Here we report interim assessments of cellular and humoral responses through 24 mos. Methods: Men (n=68)were randomized 1:1 to sip-T followed by ADT (2 wks after 3rd infusion; Arm 1) or ADT (3-mo lead-in) followed by sip-T (Arm 2). Product parameters (total nucleated cell [TNC] count, antigen presenting cell [APC] count, APC activation) were determined with each product manufacture. Cellular and humoral immune responses were analyzed through 24 mos with a repeated measures statistical model. Results: Sample size ranged 8–28 for cellular responses and 34–64 for humoral responses. PA2024 ELISPOT count increased vs baseline at most timepoints (pu003c0.05) and was lower in Arm 2 vs Arm 1 (p=0.015). PA2024 antigen-...