Background: Phase I data have demonstrated induction of antibody responses to a polyvalent vaccine conjugate (Globo-H, GM2, MUC1-TN, TF) with adjuvant OPT-821. We sought to determine if this combination decreases the hazard of progression versus OPT-821 alone in patients with EOC in second or third clinical complete remission (cCR) following chemotherapy. Secondary objectives were overall survival (OS), safety and immunogenicity. Methods: Patients were randomized (1:1) to receive OPT-821 + vaccine conjugate subcutaneously at weeks 1, 2, 3, 7, 11 and then every 12 weeks (total 11) Dose delay or reduction was not permitted. Patients were removed for pre-defined DLT. Randomized patients were evaluated for efficacy. Results: Between 2010 and 2013 171 patients were randomized; 170 treated. Most received 2 prior regimens (68%), had serous carcinoma (85%), stage 3 disease at diagnosis (77%), and no bevacizumab (67%). 54% received > 6 cycles treatment [median 6 in each arm (p = 0.33)]. 77% of patients discontinued due to progression, 4% due to toxicity, and 1 due to MDS. Maximum toxicity was grade 5 (n = 1, unrelated), grade 4 MDS and depression (n=2, unlikely), grade 3 GI disorders + others (n = 20, 4 related). Most common lesser adverse events were injection site reactions (84%) and fever (19%). (+) immunogenicity is defined as 1:40 or two fold increase. Estimated hazard ratio for PFS of vaccine conjugate + OPT-821 to OPT-821 arm was 0.98 (95% CI: 0.71-1.36). At followup of 34 months, median OS for OPT-821 is 47 months and not reached for vaccine conjugate + OPT-821. Conclusions: Vaccination with this polyvalent construct was modestly immunogenic and does not prolong PFS when compared to OPT-821 alone. The secondary OS endpoint requires additional followup. The second and third remission cohort is a feasible and well defined population to explore innovative consolidation or maintenance approaches. Clinical trial information: NCT00857545