High rate of adverse events
The rate of treatment-emergent adverse events was higher among patients who received talazoparib plus enzalutamide; 71.9% of the patients who received talazoparib plus enzalutamide experienced grade 3-4 TEAEs versus 40.6%. The most common grade 3 or greater TEAEs in the talazoparib group were anemia, low neutrophil counts, and low platelet counts. Hypertension, anemia, and fatigue were the most common in the placebo group. Talazoparib was discontinued in 19.1% of patients because of TEAEs. Enzalutamide was discontinued in 10.8% of patients in the combination group versus 11.0% in the placebo group.
Dr. Agarwal pointed out that there were TEAEs of special interest for talazoparib. “Myelodysplastic syndrome was reported in one patient during the safety reporting period, and acute myeloid leukemia was reported in one patient during the follow-up period,” he said.
Additionally, pulmonary embolism was reported in 10 (2.5%) patients (grade 3 in 9 patients) in the talazoparib arm and in 3 (0.7%) patients (all grade 3) in the placebo arm.
Results less relevant
Commenting on the study, Matthew Zibelman, MD, associate professor, department of hematology/oncology, Fox Chase Cancer Center, Philadelphia, noted that these results represent an “intriguing finding for men with mCRPC, particularly in conjunction with the previously reported PROPEL study results.
“However, given that many patients receive an androgen receptor inhibitor now for metastatic castration-sensitive prostate cancer, these results are less relevant to current practice,” Dr. Zibelman said.
“Demonstration of an overall survival benefit of the combination would be optimal to change standard of care vs potential sequential therapy.”
The study was sponsored by Pfizer, manufacturer of enzalutamide and talazoparib. Dr. Agarwal has relationships with numerous pharmaceutical companies. Dr. Castro has relationships with Astellas Pharma, AstraZeneca, Bayer, Clovis Oncology, Janssen-Cilag, Merck, MSD Oncology, Novartis and Pfizer, and Roche. Dr. Zibelman has relationships with Bristol-Myers Squibb, Exelixis, Pfizer, Jannsen, EMD Serono, and Blue Earth.
A version of this article first appeared on Medscape.com.