Veliparib monotherapy following carboplatin/paclitaxel plus veliparib combination therapy in patients with germline BRCA-associated advanced breast cancer: results of exploratory analyses from the phase III BROCADE3 trial

In the BROCADE3 trial, addition of the poly(ADP-ribose) polymerase inhibitor, veliparib, to carboplatin/paclitaxel improved progression-free survival (PFS) (hazard ratio 0.71, 95% confidence interval 0.57-0.88; P = 0.002) in patients with advanced human epidermal growth factor receptor 2-negative, germline BRCA1/2-mutated breast cancer. A subset of patients discontinued both carboplatin and paclitaxel before progression and continued on veliparib/placebo maintenance monotherapy until progression. Analyses in this patient subgroup are reported.Patients were randomized 2 : 1 to veliparib plus carboplatin/paclitaxel or placebo plus carboplatin/paclitaxel. Veliparib (120 mg twice daily) or placebo was given on days -2 to 5, carboplatin (area under the curve 6 mg/ml) on day 1, and paclitaxel (80 mg/m2) on days 1, 8, and 15 of 21-day cycles. Patients who discontinued both carboplatin and paclitaxel before progression received blinded study drug monotherapy at an increased dose of 300-400 mg twice daily continuously. PFS was the primary endpoint. Exploratory analyses were carried out in the subgroup of patients who received blinded study drug as monotherapy. A time-varying Cox model including data from all patients was also used to evaluate treatment effect in the combination and monotherapy phases.A total of 136 of 337 patients randomized to veliparib plus carboplatin/paclitaxel and 58/172 patients randomized to placebo plus carboplatin/paclitaxel discontinued both carboplatin and paclitaxel before progression and continued on blinded veliparib or placebo monotherapy. In this blinded monotherapy subgroup, investigator-assessed median PFS from randomization was 25.7 months with veliparib versus 14.6 months with placebo. Hazard ratios from a time-varying Cox model favored veliparib during both combination therapy and monotherapy. Any-grade adverse events occurring in the monotherapy phase were primarily gastrointestinal. The most common grade ≥3 adverse events were neutropenia and anemia (4% each with veliparib; 5% and 2%, respectively, with placebo).Veliparib maintenance monotherapy had a tolerable safety profile and may extend PFS following combination chemotherapy.