Veliparib With Temozolomide or Carboplatin/Paclitaxel Versus Placebo With Carboplatin/Paclitaxel in Patients With BRCA1/2 Locally Recurrent/Metastatic Breast Cancer: Randomized Phase II Study

Abstract

Background

Homologous recombination defects in BRCA1/2-mutated tumors result in sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors, which interfere with DNA damage repair. Veliparib, a potent PARP inhibitor, enhanced the antitumor activity of platinum agents and temozolomide in early phase clinical trials. This phase II study examined the safety and efficacy of intermittent veliparib with carboplatin/paclitaxel (VCP) or temozolomide (VT) in patients with BRCA1/2-mutated breast cancer.

Patients and methods

Eligible patients ≥18 years with locally recurrent or metastatic breast cancer and a deleterious BRCA1/2 germline mutation were randomized 1:1:1 to VCP, VT, or placebo plus carboplatin/paclitaxel (PCP). Primary endpoint was progression-free survival (PFS); secondary endpoints included overall survival (OS) and overall response rate (ORR).

Results

Of 290 randomized patients, 284 were BRCA+, confirmed by central laboratory. For VCP versus PCP, median PFS was 14.1 and 12.3 months, respectively (hazard ratio [HR], 0.789; 95% CI, 0.536–1.162; P=0.227), interim median OS 28.3 and 25.9 months (HR, 0.750; 95% CI, 0.503–1.117; P = 0.156), and ORR 77.8% and 61.3% (P = 0.027). For VT (versus PCP), median PFS was 7.4 months (HR, 1.858; 95% CI, 1.278–2.702; P=0.001), interim median OS 19.1 months (HR, 1.483; 95% CI, 1.032–2.131; P=0.032), and ORR 28.6% (P<0.001). Safety profile was comparable between carboplatin/paclitaxel arms. Adverse events (all grades) of neutropenia, anemia, alopecia, and neuropathy were less frequent with VT versus PCP.

Conclusion

Numerical but not statistically significant increases in both PFS and OS were observed in patients with BRCA1/2-mutated recurrent/metastatic breast cancer receiving VCP compared to PCP. The addition of veliparib to carboplatin/paclitaxel significantly improved ORR. There was no clinically meaningful increase in toxicity with VCP versus PCP. VT was inferior to PCP. An ongoing phase III trial is evaluating VCP versus PCP, with optional continuation single-agent therapy with veliparib/placebo if chemotherapy is discontinued without progression, in this patient population.Clinical trial information: NCT01506609.

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