Background: Veliparib, a poly-(ADP-ribose)-polymerase inhibitor, increases anti-tumor activity when combined with platinum chemotherapy and has monotherapeutic activity in BRCA1 or BRCA2 deficient tumors. This study was done to determine the recommended phase II dose (RP2D) of continuous veliparib in combination with initial treatment for epithelial ovarian, fallopian tube, or primary peritoneal cancer. Methods: Eligible patients had newly diagnosed, untreated, stage II-IV epithelial ovarian, fallopian tube, or primary peritoneal carcinoma or carcinosarcoma. Three regimens (six 21 day cycles) were evaluated: 1, IV q3week carboplatin (AUC 6) and paclitaxel (175mg/m²); 2, IV q3week carboplatin (AUC 6) and weekly paclitaxel (80mg/m²); and 3, IV paclitaxel (135mg/m², day 1), IP cisplatin (75mg/m², day 1 or 2) and IP paclitaxel (60mg/m², day 8). Bevacizumab 15mg/kg started in cycle 2 and continued as monotherapy for cycles 7-22. Veliparib continuous oral BID dosing in cycles 1-6 started at 30mg. A 3+3 dose escalation design evaluated dose-limiting toxicities (DLTs) in cycles 1 and 2. Once <2/6 patients experienced a DLT, that dose level was expanded to evaluate feasibility over 4 cycles. Results: We enrolled 189 patients; 32 were not evaluable. DLTs at ≥RP2D levels were as seen in the table. Conclusions: The RP2D for all regimens is veliparib 150mg BID. Clinical trial information: NCT00989651