Background: Poly(ADP-ribose) polymerases (PARP) are activated by DNA strand breaks and important for DNA repair in response to platinum-based chemotherapy. PARP inhibition with Vel might enhance anti-tumor effects of Cap with Ox. This phase I study (NCI 8604) examines the tolerability, safety and preliminary efficacy of the combination of Vel with Cap and Ox. Methods: This is a phase I dose escalation protocol testing escalating doses of Vel with Cap and Ox every 28 days (Table 1). Pts were treated in cohorts of 3-6 pts until cycle 1 DLTs were defined. Key eligibility criteria included age ≥ 18 with histologically confirmed malignancy meeting at least one of the following: documented BRCA1/2 mutation and a BRCA related malignancy; a 20% probability of harboring a BRCA mutation; metastatic colorectal cancer; mucinous ovarian cancer; other GI malignancy in which Ox has demonstrated activity. Results: 17 pts (median age 52 [range 19-71]; 14 female, 3 male) were treated at 4 dose levels (DL) (Table 1). Pts had cholangiocarcinoma (6), breast (4), ovarian (4), neuroendocrine (1), pancreas (1), and colon (1) cancers. 7 pts (4 breast, 3 ovarian) are BRCA1+. Dose escalation was initiated at DL1. One DLT (mucositis) occurred at this dose level. At DL2, two DLTs (mucositis with neutropenic fever and thrombocytopenia) were noted. The protocol was amended for escalation to begin at DL1A. At DL2A, a grade 2 DLT of fatigue requiring dose delay occurred in one pt. Pts were on study for median 10 weeks (range 1 – 88). 24% of pts remained on study ≥ 6 months. Of the 14 pts with measurable disease, 5 had PR (2 ovarian, 2 breast, 1 colon) and 4 had SD (3 cholangiocarcinoma, 1 pancreas). Common AEs include nausea/vomiting (94%), diarrhea (47%), mucositis (41%), anemia (35%), neutropenia (24%), and thrombocytopenia (18%). Conclusions: Vel in combination with Cap and Ox is safe and well tolerated in pts with advanced solid malignancies. The recommended phase II dose is DL2A Vel 40mg BID (D 1-7, 15-21), Cap 1000mg/m² BID (D 1-7, 15-21), and Ox 85mg/m² (D 1 and 15). Clinical trial information: NCT01233505