Spotlight on Panitumumab in Metastatic Colorectal Cancer

Panitumumab (Vectibix (R)) is a recombinant, fully human, IgG2 anti-epidermal growth factor receptor (EGFR) monoclonal antibody. This spotlight reviews the clinical efficacy of intravenous panitumumab in combination with chemotherapy in the first- and second-line treatment of metastatic colorectal cancer and as monotherapy in chemotherapy-refractory metastatic colorectal cancer, as well as summarizing its pharmacologic properties and tolerability. Panitumumab is indicated for use in patients with wild-type rather than mutant KRAS tumors. The efficacy of intravenous panitumumab 6 mg/kg administered every 2 weeks was examined in randomized, open-label, multicenter, phase III trials in patients with metastatic colorectal cancer. When administered as first- or second-line treatment in combination with chemotherapy, panitumumab plus chemotherapy prolonged progression-free survival to a significantly greater extent than chemotherapy alone in patients with wild-type KRAS tumors; no significant between-group difference in overall survival was seen in the second-line treatment trial. In patients with mutant KRAS tumors, progression-free survival was significantly shorter with panitumumab plus oxaliplatin-based chemotherapy (FOLFOX4) than with FOLFOX4 alone in the first-line treatment trial, with no significant difference between patients receiving panitumumab plus irinotecan-based chemotherapy (FOLFIRI) and those receiving FOLFIRI alone in the second-line treatment trial. In chemotherapy-refractory patients with metastatic colorectal cancer, panitumumab monotherapy plus best supportive care prolonged progression-free survival to a significantly greater extent than best supportive care alone in both the overall population and in patients with wild-type KRAS tumors, but not in those with mutant KRAS tumors. Intravenous panitumumab has an acceptable tolerability profile when administered as monotherapy or in combination with chemotherapy. It is associated with the skin-related toxicities characteristic of EGFR inhibitors and appears to have a low risk of immunogenicity. In conclusion, in patients with wild-type KRAS tumors, panitumumab is a useful option in combination with chemotherapy for the first- and second-line treatment of metastatic colorectal cancer or as monotherapy for the treatment of chemotherapy-refractory metastatic colorectal cancer.