Introduction Oregovomab, a murine IgGκ1 MAb, binds to the circulating tumor associated antigen CA125, resulting in development of immunogenic complexes with CA125, which are subsequently processed by dendritic cells and macrophages leading to downstream CA125-specific antitumor activity by T and B lymphocytes. In a randomized Phase 2 study in previously untreated EOC patients, immunization with oregovomab with paclitaxel and carboplatin (PC) demonstrated significant improvement in mPFS (months) 41.8 for PCO and 12.2 for PC (p = 0.0027, HR 0.46) and mOS has not yet been reached (NE) for PCO and was 43.2 months for PC (p = 0.043, HR 0.35).

Methods This Phase 3, double-blind, placebo-controlled, multicenter trial, has enrolled patients from 14 countries. Patients with optimally debulked with FIGO III/IV EOC and serum CA125 ≥ 50 U/ml receiving adjuvant (Cohort 1) or neoadjuvant (Cohort 2) chemotherapy were randomized post-surgery to PCO or PCP. Patients with germline BRCA1/2 mutations were excluded. Chemotherapy will be administered every 3 weeks in both cohorts. In cohort 1, oregovomab/placebo is administered simultaneously at cycles 1, 3, and 5 of chemotherapy with an additional dose at 12 weeks following cycle 5. In cohort 2, oregovomab/placebo is administered post interval debulking surgery at cycles 4 and 6 with an additional dose at 6- and 18-weeks following cycle 6. The primary objective is PFS determined by RECIST 1.1 criteria.

Current Trial Status At the time of abstract submission, 618 patients were enrolled and target enrolment Cohort 1 (378) and Cohort 2 (240) was achieved.