CI-1033, an irreversible pan-erbB receptor inhibitor and its potential application for the treatment of breast cancer.

The erbB family of cell surface receptor proteins consists of four members, all of which play a role in the development and growth of the normal breast. The activity of this signaling pathway is normally tightly controlled, and dysregulation has been shown to play a significant role in the pathogenesis and progression of breast and other cancers. The potent transforming potential of these receptors is further enhanced by the coexpression of multiple members of this receptor family, which worsens prognosis. Therapeutic blockade of erbB-2 receptor signaling has to date been shown to be effective in only a subset of chemotherapy-resistant breast cancer patients. CI-1033 is a highly potent and selective pan-erbB inhibitor that efficiently blocks signal transduction through all four members of the erbB receptor family. In addition, it covalently binds to these receptors, irreversibility inhibiting them, and thereby provides for prolonged suppression of erbB receptor-mediated signaling. Clinically, it has been shown to have an acceptable side effect profile at potentially therapeutic doses and schedules. Biomarker studies have shown target inhibition in patients, and evidence of antitumor activity has also been observed in phase I studies. Given the broad expression pattern of the erbB family of receptors in solid tumors, and the important proliferative effect of co-expression of multiple erbB receptors, CI-1033, as an irreversible, pan-erbB inhibitor, has the potential to have an important role in the future treatment of breast and other cancers.