Abstract

Elucidation of molecular pathways that promote malignancies has led to the identification of the epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) as key components involved in regulation of tumor proliferation and angiogenesis, respectively. Biologic agents that target these individual pathways have proven effective in treating patients with advanced non-small-cell lung cancer (NSCLC), adding to previously available therapies and often with fewer side effects. However, inhibition of a single molecular pathway does not account for alternate pathways or biologic adaptations that eventually lead to resistance. Therefore, combining EGFR and VEGF inhibition is currently under investigation as a means to overcome resistance and promote synergy. Erlotinib, an anti-EGFR agent, and bevacizumab, an anti-VEGF agent, are both approved in NSCLC, demonstrating single-agent activity. The phase II trials evaluating the combination of erlotinib and bevacizumab have shown efficacy as first-line therapy or in patients with previously treated NSCLC either alone or with chemotherapy. Dual inhibition of EGFR and VEGF pathways has also been accomplished by the novel agents vandetanib and XL647, which are able to target both pathways. Vandetanib has also demonstrated activity in patients with advanced NSCLC either alone or with chemotherapy in phase I/II studies. Another novel agent, XL647, has demonstrated promising single-agent activity in patients who have been resistant to previous anti-EGFR therapy. Further evaluation of combined EGFR and VEGF inhibition is under investigation.