Abstract C49: Combination treatment with metronomic cyclophosphamide and the EGFR monoclonal antibody nimotuzumab is efficacious and non-toxic in a preclinical model of advanced triple negative breast cancer
Authors: Mutsaers Anthony J. , Man Shan , Xu Ping , Tikhomirov Ilia , Kerbel Robert S. 
Published: June 2012

Abstract
Low dose, metronomic chemotherapy with cyclophosphamide has shown activity in the treatment of advanced breast cancer, and has been paired with targeted agents such as trastuzumab and bevacizumab for long term therapy, with encouraging results. The epidermal growth factor receptor (EGFR) pathway may be a relevant target for the treatment of triple-negative breast cancer, a tumor type with an aggressive behavior and limited therapeutic options. Nimotuzumab is a humanized monoclonal antibody targeting EGFR with an affinity that is lower than currently approved agents, such as cetuximab and panitumumab. This leads to preferential targeting of EGFR-overexpressing tumors, minimizing toxicity, making it well suited for long term dosing, including possible combination therapy with minimally toxic chemotherapeutic regimens, when treating tumors with high EGFR expression. The objective of this study was to evaluate nimotuzumab in combination with metronomic cyclophosphamide in a preclinical model of advanced, triple negative breast cancer. Increasingly aggressive metastatic variants of the MDA-MB-231 human breast cancer cell line were selected through passage in vivo, resulting in a line termed 164/8-1B, characterized as highly metastatic to many organs, including lymph nodes, lung, and brain. This variant also had increased EGFR expression compared to the parental cell line. Combination therapy with nimotuzimab twice weekly and continous low-dose cyclophosphamide resulted in significant primary tumor growth delay in the metastatic variant, compared to the parental cell line. In addition, the combination resulted in a significant survival advantage over cyclophosphamide alone in the advanced metastatic model. Nimotuzumab displayed single agent activity in primary tumor xenografts but not in the treatment of advanced metastatic disease. Primary tumor regrowth in the mammary fat pad occurred with similar frequency across treatment groups, however the resulting tumor size was decreased in mice receiving combination treatment. Lymph node metastasis was observed in 40–60% of mice in each treatment group, with the exception of those that received combination therapy, where no gross evidence of lymphadenomegaly was observed. Finally, cell lines established from lung metastases from 3 mice receiving combination therapy showed EGFR expression, suggesting that resistance to treatment was not associated with loss of target expression. In conclusion, combination therapy with low dose, continuous cyclophosphamide and the EGFR monoclonal antibody nimotuzumab was an efficacious regimen in this advanced, metastatic, triple negative, EGFR overexpressing breast cancer model, and would be expected to be minimally toxic to patients. This combination approach should be considered for this patient population in future clinical trials.
Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C49.