Ixabepilone development across the breast cancer continuum: a paradigm shift

The epothilone analog ixabepilone exhibits reduced susceptibility to several important tumor survival mechanisms that limit the efficacy of taxanes and anthracyclines. As a single agent, ixabepilone has shown promise in metastatic breast cancer when anthracyclines, taxanes, or capecitabine have failed; and in early-stage breast cancer that is taxane-naïve or has previously received taxanes in the adjuvant or metastatic setting. Compared with capecitabine alone, ixabepilone used in combination with capecitabine in patients previously treated with and resistant to anthracyclines and taxanes produced a 25% reduction in the risk of disease progression. Triple-negative tumors showed particular susceptibility to this doublet. Ixabepilone has also demonstrated efficacy as first-line therapy in combination with targeted agents such as bevacizumab and trastuzumab. Ongoing investigations should provide insight as to how this agent could be integrated into treatment of early-stage disease. In clinical studies, toxicities with ixabepilone were manageable and reversible through dose reduction or delay, even in patients with extensive or heavily-pretreated disease. Thus, ixabepilone represents a useful addition to the therapeutic options available for advanced breast cancer, and it may extend progression-free survival in patients with limited treatment options.