Among the 21 efficacy-evaluable patients who were selected based on their PD-L1 expression level, the overall response rate was 19% (95% CI, 5%-42%), which included 2 patients who experienced a partial response and 2 who experienced a complete response; 3 out of 4 of the responses were ongoing. The 24-week progression-free survival rate was 27% (95% CI, 7 to 47%).

In addition, 3 patients who were classified as having progressive disease appeared to have pseudoprogression, as the target lesion and new lesions regressed after the initial evaluation.

Although the median duration of response was ongoing (current range, 18 to more than 56 weeks), the median duration of survival follow-up was 40 weeks (range, more than 2 to more than 85 weeks).

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During the median safety follow-up of 9 weeks, adverse events (AEs) occurred in 63% of safety-evaluable patients, with 11% of patients having experienced grade 3 to 5 events.

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Common AEs included fatigue (22%), pyrexia (15%), neutropenia (15%), nausea (15%), asthenia (11%), decreased appetite (11%), and diarrhea (9%). Grade 3 events included neutropenia, anemia, nausea, and vomiting. Two treatment-related deaths occurred and are currently under investigation.

“Further evaluation of this agent is ongoing in both PD-L1 expressing and PD-L1 nonexpressing patients with TNBC,” said Dr. Emens.


  1. Emens LA, Braiteh FS, Cassier P, et al. Inhibition of PD-L1 by MPDL3280A leads to clinical activity in patients with metastatic triple-negative breast cancer (TNBC). Abstract 2859. Presented at: 2015 American Association for Cancer Research (AACR) Meeting; April 18-22, 2015; Philadelphia, PA.