Lymphoid and myeloid biomarkers for clinical outcome of combined immunotherapy with granulocyte-macrophage colony-stimulating factor-tranduced allogeneic prostate cancer cells (GVAX) and ipilimumab in castration-resistant prostate cancer patients.

2562 Background: In a phase-I dose escalation trial in patients with castration-resistant prostate cancer we showed that GVAX and ipilimumab had an acceptable safety profile. Moreover, we observed tumor responses and prolonged survival as compared to the Halabi predicted overall survival (OS). However, ipilimumab can also lead to severe immune-related adverse events. To avoid unnecessary exposure to this risk, it is essential to identify biomarkers that correlate with clinical activity. Methods: Patients had castration-resistant prostate cancer and were chemotherapy-naive. They received bi-weekly GVAX for a 24 week period combined with monthly intravenous administrations of ipilimumab. Each cohort of 3 patients received an escalating dose of ipilimumab at 0·3, 1·0, 3·0 or 5·0 mg/kg. In an expansion cohort 16 patients were treated with GVAX and 3·0 mg/kg ipilimumab. Flowcytometric monitoring of lymphoid and myeloid subsets in blood were performed. Results: We observed a significantly prolonged OS for patie...