Mace Rothenberg, MD
The FDA has granted a priority review to a new drug application (NDA) for talazoparib for the treatment of patients with germline BRCA
mutation–positive, HER2-negative locally advanced or metastatic breast cancer, according to Pfizer, the manufacturer of the PARP inhibitor.
Among patients with measurable disease, the complete response (CR) rate in the talazoparib arm was 5.5%, the partial response (PR) rate was 57.1%, and the stable disease rate was 21.0%. The corresponding rates in the physician’s choice arm were 0, 27.2%, and 31.6%, respectively.
The median duration of response was 5.4 months (95% CI, 4.2-6.3) with talazoparib and 3.1 months (95% CI, 2.8-5.6) with chemotherapy (HR, 0.43; 95% CI, 0.27-0.70; P
= .0005). The 1-year probability of sustained response was 23% vs 0%, respectively.
The OS data are not yet mature; however, an interim OS analysis found a positive trend favoring talazoparib, with a 24% reduction in the risk of death. The median OS was 22.3 months (95% CI, 18.1-26.2) with the PARP inhibitor versus 19.5 months (95% CI, 16.3-22.4) with chemotherapy (HR, 0.76; 95% CI, 0.54-1.06; P
The investigators considered talazoparib to be well tolerated overall. The safety analysis included 286 patients from the talazoparib arm and 126 patients from the control arm.
Grade 3 hematologic AEs in the talazoparib group included anemia (38.5% vs 4.0% with chemotherapy), neutropenia (17.8% vs 19.8%, respectively), thrombocytopenia (11.2% vs 1.6%), and lymphopenia (3.1% vs 0).
In the talazoparib arm, grade 4 hematologic AEs included anemia (0.7% vs 0.8% with chemotherapy), neutropenia (3.1% vs 15.1%, respectively), thrombocytopenia (3.5% vs 0), and febrile neutropenia (0.3% vs 0.8%).
The most common grade 3 nonhematologic AEs with talazoparib included vomiting, back pain, and dyspnea, at 2.4% each. There were no grade 4 nonhematologic AEs in either arm. Grade 3/4 serious AEs occurred in approximately 25% of patients in each arm.
The investigators also examined QoL using the EORTC QLQ-C30 questionnaire, which was completed by 262 patients receiving the PARP inhibitor and 114 patients receiving chemotherapy.
The results showed that in patients receiving talazoparib, there was a statistically significant improvement from baseline in estimated overall mean change in global health status (GHS)/QoL: 3.0 (95% CI, 1.2-4.8) versus -5.4 (95% CI, -8.8 to -2.0) in patients receiving physician’s choice of therapy (P
The results also found a significant delay in the median time to clinically meaningful deterioration in GHS/QoL with talazoparib versus chemotherapy: 24.3 months (95% CI, 13.8 to not reached) versus 6.3 months (95% CI, 4.9-12.2; HR, 0.38; 95% CI, 0.26-0.55; P
In January 2018, olaparib (Lynparza) became the first PARP inhibitor approved for breast cancer. The agency specifically approved the drug for the treatment of patients with germline BRCA
–positive, HER2-negative metastatic breast cancer who have previously received chemotherapy. Additionally, HR-positive patients should have prior endocrine therapy or not be considered appropriate for such treatment.
Litton JK, Rugo HS, Ettl J, et al. A phase 3 trial comparing talazoparib, an oral PARP inhibitor, to physician’s choice of therapy in patients with advanced breast cancer and a germline BRCA-mutation. Presented at: 2017 San Antonio Breast Cancer Symposium; December 5-9, 2017; San Antonio, TX. Abstract GS6-07.