Panitumumab: the evidence of its therapeutic potential in metastatic colorectal cancer care

INTRODUCTION: Colorectal cancer is the fourth most common malignant disease. Of newly diagnosed patients, 40% have metastatic disease at diagnosis, and approximately 25% of patients with localized disease at diagnosis will ultimately develop metastatic disease. The benefits of systemic chemotherapy in the treatment of metastatic colorectal cancer over best supportive care have been established. Panitumumab (ABX-EGF) is the first fully human monoclonal antibody developed for use in colorectal cancer that targets the extracellular domains of epidermal growth factor receptor. AIMS: The goal of this article is to review the published evidence for the use of panitumumab in the treatment of metastatic colorectal cancer to define its therapeutic potential. EVIDENCE REVIEW: The major evidence of panitumumab activity in colorectal cancer has appeared in meeting report abstracts. One phase II study in monotherapy, one in combination with chemotherapy, and one phase III study have included only patients with metastatic colorectal cancer. CLINICAL POTENTIAL: To date, in phase II clinical studies panitumumab has demonstrated antitumor activity in advanced, refractory colorectal cancer. As monotherapy it resulted in a 10% response rate with 38% of patients having stable disease, and a 36% response rate with 46% stable disease when combined with chemotherapy. A phase III study indicates a clinically significant advantage of panitumumab as third-line monotherapy over best supportive care. Panitumumab appears to have a good tolerability profile, with no maximum tolerated dose yet defined.