Abstract
Triple-negative breast cancer (TNBC) is an aggressive subtype defined by lack of hormone receptor expression and non-amplified HER2. Adavosertib (AZD1775) is a potent, small-molecule, ATP-competitive inhibitor of the Wee1 kinase that potentiates the activity of many DNA-damaging chemotherapeutics and is currently in clinical development for multiple indications. The purpose of this study was to investigate the combination of AZD1775 and capecitabine/5FU in preclinical TNBC models. TNBC cell lines were treated with AZD1775 and 5FU and cellular proliferation was assessed in real-time using IncuCyte® Live Cell Analysis. Apoptosis was assessed via the Caspase-Glo 3/7 assay system. Western blotting was used to assess changes in expression of downstream effectors. TNBC patient-derived xenograft (PDX) models were treated with AZD1775, capecitabine, or the combination and assessed for tumor growth inhibition. From the initial PDX screen, two of the four TNBC PDX models demonstrated a better response in the combination treatment than either of the single agents. As confirmation, two PDX models were expanded for statistical comparison. Both PDX models demonstrated a significant growth inhibition in the combination versus either of the single agents. (TNBC012, p < 0.05 combo vs. adavosertib or capecitabine, TNBC013, p < 0.01 combo vs. adavosertib or capecitabine.) An enhanced anti-proliferative effect was observed in the adavosertib/5FU combination treatment as measured by live cell analysis. An increase in apoptosis was observed in two of the four cell lines in the combination when compared to single-agent treatment. Treatment with adavosertib as a single agent resulted in a decrease in p-CDC2 in a dose-dependent manner that was also observed in the combination treatment. An increase in γH2AX in two of the four cell lines tested was also observed. No significant changes were observed in Bcl-xL following treatment in any of the cell lines. The combination of adavosertib and capecitabine/5FU demonstrated enhanced combination effects both in vitro and in vivo in preclinical models of TNBC. These results support the clinical investigation of this combination in patients with TNBC, including those with brain metastasis given the CNS penetration of both agents.
Highlights
Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype defined by a lack of hormone receptor expression and non-amplified HER2 [1]
In an effort to minimize the number of animals required to evaluate multiple combinations with AZD1775, we performed an initial screen using four TNBC patient-derived xenograft (PDX) models treated with AZD1775, capecitabine, paclitaxel, gemcitabine, doxorubicin, navitoclax (BCL-2 inhibitor), VX970 (ATR inhibitor), and romidepsin (HDAC inhibitor) or combinations of these agents with AZD1775
15% of breast cancers in the United States are classified as TNBC and, despite recent advances in local and systemic therapies, patients with TNBC continue to be at increased risk of metastatic recurrence and have inferior outcomes compared to other breast cancer subtypes [16]
Summary
Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype defined by a lack of hormone receptor expression and non-amplified HER2 [1]. TNBC accounts for approximately 15% of breast cancer cases but is associated with an increased risk of cancer recurrence, brain metastasis, and death due to metastatic breast cancer [1]. The luminal androgen receptor, mesenchymal, basal-like immunosuppressed and basal-like immune-activated subtypes have been described [2]. Mutations in p53 are common in TNBC, occurring in approximately 85%. While immunotherapy with the PD-L1-inhibitor atezolizumab prolongs progression-free survival in patients with PD-L1-positive TNBC when added to nab-paclitaxel, chemotherapy remains the standard treatment for metastatic disease and results in a median survival of 12–18 months [1]. There remains an unmet need for active targeted therapies in TNBC
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