Breast Cancer Coverage from Every Angle

Combination of Abemaciclib, Pembrolizumab, and Anastrozole in Metastatic Breast Cancer

By: Kelly M. Hennessey, PhD
Posted: Wednesday, July 29, 2020

Patients with hormone receptor–positive, HER2-negative metastatic breast cancer experienced elevated transaminase levels and pneumonitis when treated with abemaciclib in combination with pembrolizumab and anastrozole than when given individual treatments. These findings were presented by Sara M. Tolaney, MD, MPH, of Dana-Farber Cancer Institute, Boston, and colleagues during the 2020 American Association for Cancer Research (AACR) Virtual Annual Meeting I (Abstract CT108). At the time of the presentation, assessment of anticancer activity was premature.

In a multicenter, nonrandomized, open-label, multicohort phase Ib study, researchers enrolled 26 postmenopausal patients with hormone receptor–positive, HER2-negative metastatic breast cancer. The primary study objective was to characterize the safety of the triplet therapy consisting of abemaciclib, pembrolizumab, and anastrozole. Of the total study population, half previously received systemic anticancer therapy, 12 of whom had received adjuvant endocrine therapy. Most of the patients (65%) had visceral disease, and more than half of them (54%) had at least three metastatic sites.

Patients experienced grade 3 or 4 adverse events, including elevated alanine aminotransferase levels and neutropenia (n = 8) and higher aspartate aminotransferase levels (n = 6). Pneumonitis resulted in two deaths. The preliminary response rate showed that five patients achieved a partial response, and the disease control rate was 77%; however, 27% of patients achieved a complete response, partial response, or stable disease for 6 months or more.

“With higher rates of transaminase levels and pneumonitis than reported for individual treatments, and two fatal adverse events, evaluation of anticancer activity is premature,” concluded the researchers.

Disclosure: For full disclosures of the study authors, visit

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