Harvey, Harold A.

1024 Background: The combination of platinum agents and PARP inhibitors may benefit patients (pts) with BRCA-associated metastatic breast cancer (MBC). We report on the response and clinical benefit rates when combining the PARP inhibitor veliparib (V) and carboplatin (carb) in a phase I trial. Methods: BRCA carriers with MBC were eligible. Carb starting at an AUC of 6 was given IV in 21-day cycles (C) and V was given orally twice daily (BID) at dose levels (L) L1 through L5. Results: Twenty-eight pts (26 eligible) carrying BRCA1 (12) or BRCA2 (15), or both (1) mutations were accrued between June 2010 and June 2012. The median age (32-66) was 45 years. The number (#) of prior chemotherapy regimens given for MBC was 1 (0-5); 70% of BCs were ER+, and 7% were HER2+. The schema, dose limiting toxicities (DLT) during C 1, median # of Cs on trial, and maximum tolerated dose (MTD) are shown. There were 3 (12%) complete and 9 (35%) partial responses (PR). Unconfirmed PR or stable MBC (median duration: 8 months [6-10+]) were seen in 7 pts (27%); the clinical benefit rate was74%. The median progression-free survival (PFS) is 7.8 months (95% CI 7.3-9.5). The pt with Fallopian tube cancer had a CR. DLTs with C 1 were seen in 2/6 evaluable pts at L1 (1 pt w/grade 3 hyponatremia and dehydration, and 1pt w/grade 4 thrombocytopenia [PLT]), leading to de-escalation of carb. At L2, 1 pt had grade 4 PLT. At L5, 1 pt had grade 4 PLT, and 2 pts grade 3 PLT (1 pt also experienced grade 4 granulocytopenia [ANC]), defining the MTD at carb AUC 5 and V 150 mg BID (L4). Dose delays and/or dose adjustments due to grade ≥ 2 toxicities for ANC or PLT were seen during the first 3 Cs at L1 (100%), L2 (50 %), L3 (67%), L4 (83 %), and at L5 (67%). Conclusions: The combination of carb and V is active, and is associated with substantial clinical benefit rate and managable hematologic toxicities in BRCA carriers with MBC. Further definition of the role of V is warranted. [Table: see text]

Abstract Purpose: We aimed to establish the MTD of the poly (ADP-ribose) (PAR) polymerase inhibitor, veliparib, in combination with carboplatin in germline BRCA1- and BRCA2- (BRCA)-associated metastatic breast cancer (MBC), to assess the efficacy of single-agent veliparib, and of the combination treatment after progression, and to correlate PAR levels with clinical outcome. Experimental Design: Phase I patients received carboplatin (AUC of 5–6, every 21 days), with escalating doses (50-20 mg) of oral twice-daily (BID) veliparib. In a companion phase II trial, patients received single-agent veliparib (400 mg BID), and upon progression, received the combination at MTD. Peripheral blood mononuclear cell PAR and serum veliparib levels were assessed and correlated with outcome. Results: Twenty-seven phase I trial patients were evaluable. Dose-limiting toxicities were nausea, dehydration, and thrombocytopenia [MTD: veliparib 150 mg po BID and carboplatin (AUC of 5)]. Response rate (RR) was 56%; 3 patients remain in complete response (CR) beyond 3 years. Progression-free survival (PFS) and overall survival (OS) were 8.7 and 18.8 months. The PFS and OS were 5.2 and 14.5 months in the 44 patients in the phase II trial, with a 14% RR in BRCA1 (n = 22) and 36% in BRCA2 (n = 22). One of 30 patients responded to the combination therapy after progression on veliparib. Higher baseline PAR was associated with clinical benefit. Conclusions: Safety and efficacy are encouraging with veliparib alone and in combination with carboplatin in BRCA-associated MBC. Lasting CRs were observed when the combination was administered first in the phase I trial. Further investigation of PAR level association with clinical outcomes is warranted. Clin Cancer Res; 23(15); 4066–76. ©2017 AACR.