Emens LA, et al. - In this phase 1 study of 116 patients with metastatic triple-negative breast cancer (mTNBC), researchers assessed the safety, clinical activity, and biomarkers associated with the use of single-agent atezolizumab (anti–programmed cell death ligand 1). In a multicohort open-label, phase 1 study at US and European academic medical centers, women with mTNBC (defined by investigator assessment) were enlisted between January 2013 and February 2016. For this investigation, atezolizumab was given intravenously every 3 weeks until unacceptable toxic effects or loss of clinical benefit. The findings suggested that in mTNBC patients with stable or reactive disease, single-agent atezolizumab was well tolerated and provided long-lasting clinical benefit and earlier treatment lines.