Adams S, et al. - In this phase 1b trial for metastatic triple-negative breast cancers, researchers investigated the safety, tolerability, and preliminary clinical activity of atezolizumab plus nab-paclitaxel. Investigators found that there was a manageable safety profile for atezolizumab plus nab-paclitaxel combination. Antitumor responses, including in patients previously treated with a taxane, have been observed.

Methods

• Study participants included 33 women with stage IV or locally recurrent triple-negative breast cancers and 0 to 2 lines of prior chemotherapy in the metastatic setting from December 8, 2014, to April 30, 2017, at 11 sites in the US.
• The median follow-up period was 24.4 months (95% CI, 22.1-28.8 months).
• Interventions included patients received concurrent intravenous atezolizumab and intravenous nab-paclitaxel (minimum 4 cycles).
• Safety and tolerability was the primary end point.
• Best overall response rate by Response Evaluation Criteria in Solid Tumors, version 1.1; objective response rate; duration of response; disease control rate; progression-free survival; overall survival; and biomarker analyses were the included secondary end points.

Results

• For this investigation, 33 women had a median age of 55 years (range, 32-84 years) and received 1 or more doses of atezolizumab.
• In this analysis, all subjects (100%) experienced at least 1 treatment-related adverse event, 24 subjects (73%) experienced grade 3/4 adverse events, and 7 subjects (21%) had grade 3/4 adverse events of special interest.
• There were no deaths related to treatment for study.
• Findings revealed that the objective response rate was 39.4% (95% CI, 22.9%-57.9%), and the median duration of response was 9.1 months (95% CI, 2.0-20.9 months).
• Data reported that the disease control rate was 51.5% (95% CI, 33.5%-69.2%).
• Investigators discovered that median progression-free survival and overall survival were 5.5 months (95% CI, 5.1-7.7 months) and 14.7 months (95% CI, 10.1-not estimable), respectively.
• They observed that that concurrent nab-paclitaxel neither significantly changed biomarkers of the tumor immune microenvironment (programmed death-ligand 1, tumor-infiltrating lymphocytes, CD8) nor impaired atezolizumab systemic immune activation (expansion of proliferating CD8+ T cells, increase of CXCL10 chemokine).