Background: DN24-02 is an investigational HER2-targeted autologous cellular immunotherapy (ACI) based on the same manufacturing platform as sipuleucel-T, an ACI approved by the FDA and EMA for certain patients (pts) with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer. DN24-02 consists of antigen presenting cells (APC) cultured with BA7072, a recombinant HER2-derived antigen (HER500) linked to GM-CSF. NeuACT (N10-1; NCT01353222) compares the efficacy and safety of adjuvant DN24-02 to surveillance in HER2+ urothelial cancer (UC) pts at high risk of relapse after resection. Preliminary product potency, immune response and safety data are reported. Methods: Pts randomized to DN24-02 received 3 infusions at 2 week intervals. Primary endpoint is overall survival. Secondary objectives include disease-free survival, antigen-specific immune response, product potency (measured by APC activation) and safety. Results: As of November 2013, 38 pts completed DN24-02 infusions and were assessed for product potency. APC activation was observed for each infusion and the profile was indicative of a prime boost effect, with a greater magnitude at infusions 2 (median 15.26; range: 6.42–23.97) and 3 (14.69; 7.38–30.86) than 1 (6.73; 3.47–14.34). T-cell associated cytokines were greater at infusions 2 and 3 than 1. Following treatment, significant increases were observed in peripheral immune responses (p<0.01), and were comparable in pts with and without neoadjuvant chemotherapy. Adverse events (AEs) occurring in >15% of 48 pts receiving ≥1 leukapheresis were fatigue (41.7%), chills (37.5), nausea (25.0), pyrexia (18.8) and headache (16.7). Three pts had treatment-related grade ≥3 AEs or SAEs. No clinically significant changes were reported in left ventricular ejection fraction. Conclusions: This preliminary analysis suggests a pattern of DN24-02 APC activation and T-cell cytokines consistent with immunological prime-boost similar to that of sipuleucel-T. DN24-02 appears well-tolerated in UC pts, and the most common AEs are similar to those reported with sipuleucel-T. Clinical trial information: NCT01353222.