CYT107 After Vaccine Treatment (Provenge®) in Patients With Metastatic Castration-Resistant Prostate Cancer

PRIMARY OBJECTIVES: I. To determine whether CYT107 administration increases the vaccine-induced antigen-specific T-cell immune response to the sipuleucel-T fusion protein vaccine construct prostatic acid phosphatase granulocyte-macrophage colony-stimulating factor (PAP-GM-CSF) (PA2024). SECONDARY OBJECTIVES: I. To determine whether CYT107 administration increases the vaccine-induced antigen-specific T-cell immune response to PAP. II. To assess the character of the T-cell immune response to PAP and PA2024. III. To determine whether CYT107 administration increases the vaccine-induced antigen-specific antibody immune responses to PAP and PA2024. IV. To quantify the effects of CYT107 on T-cell repertoire diversity. V. To assess the effects of CYT107 on the immune competence of patients with advanced prostate cancer. VI. To assess the clinical efficacy and tolerability of sipuleucel-T plus CYT107 compared with sipuleucel-T alone. OUTLINE: Patients are randomized to 1 of 2 cohorts. COHORT I: Patients receive no treatment (observation) after completion of standard sipuleucel-T therapy. COHORT II: Patients receive glycosylated recombinant human interleukin-7 subcutaneously (SC) every week for 4 weeks (on days 0, 7, 14, and 21) beginning 3-7 days after completion of standard sipuleucel-T therapy. Treatment continues in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up for 53 weeks. Patients are followed by phone, once a year, after completion of Week 53 for overall survival.