Neutralization of BCL-2/XL Enhances the Cytotoxicity of T-DM1 In Vivo
Abstract One of the most recent advances in the treatment of HER2+ breast cancer is the development of the antibody–drug conjugate, T-DM1. T-DM1 has proven clinical benefits for patients with advanced and/or metastatic breast cancer who have progressed on prior HER2-targeted therapies. However, T-DM...
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Published in | Molecular cancer therapeutics Vol. 18; no. 6; pp. 1115 - 1126 |
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Main Authors | , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
01.06.2019
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Online Access | Get full text |
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Summary: | Abstract
One of the most recent advances in the treatment of HER2+ breast cancer is the development of the antibody–drug conjugate, T-DM1. T-DM1 has proven clinical benefits for patients with advanced and/or metastatic breast cancer who have progressed on prior HER2-targeted therapies. However, T-DM1 resistance ultimately occurs and represents a major obstacle in the effective treatment of this disease. Because anti-apoptotic BCL-2 family proteins can affect the threshold for induction of apoptosis and thus limit the effectiveness of the chemotherapeutic payload, we examined whether inhibition of BCL-2/XL would enhance the efficacy of T-DM1 in five HER2-expressing patient-derived breast cancer xenograft models. Inhibition of BCL-2/XL via navitoclax/ABT-263 significantly enhanced the cytotoxicity of T-DM1 in two of three models derived from advanced and treatment-exposed metastatic breast tumors. No additive effects of combined treatment were observed in the third metastatic tumor model, which was highly sensitive to T-DM1, as well as a primary treatment-exposed tumor, which was refractory to T-DM1. A fifth model, derived from a treatment naïve primary breast tumor, was sensitive to T-DM1 but markedly benefited from combination treatment. Notably, both PDXs that were highly responsive to the combination therapy expressed low HER2 protein levels and lacked ERBB2 amplification, suggesting that BCL-2/XL inhibition can enhance sensitivity of tumors with low HER2 expression. Toxicities associated with combined treatments were significantly ameliorated with intermittent ABT-263 dosing. Taken together, these studies provide evidence that T-DM1 cytotoxicity could be significantly enhanced via BCL-2/XL blockade and support clinical investigation of this combination beyond ERBB2-amplified and/or HER2-overexpressed tumors. |
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ISSN: | 1535-7163 1538-8514 |
DOI: | 10.1158/1535-7163.MCT-18-0743 |