Background: Panitumumab is a fully human monoclonal IgG2 antibody targeting the epidermal growth factor receptor (EGFR).
Aim: To review the efficacy of panitumumab in the treatment of metastatic colorectal cancer (mCRC).
Methods: Available literature identified from PubMed and conference websites was reviewed.
Results: In phase 2-3 studies, panitumumab monotherapy achieved objective response rates (ORRs) of 8-13% in relapsed/refractory EGFR-expressing mCRC. In a randomized phase 3 study (463 patients), panitumumab almost halved the risk of disease progression/death vs. a control group receiving only best supportive care (hazard ratio 0.54; 95% CI: 0.44-0.66; P < 0.0001). Objective response was achieved in 22/231 (10%) patients randomized to panitumumab--and also in 20/176 (11%) patients assigned to the control group who received panitumumab in a separate crossover protocol after disease progression. Response was confined to patients with tumours harbouring wild-type KRAS (ORR approximately equal to 20%). Panitumumab is also being evaluated in earlier lines of treatment. Panitumumab monotherapy is generally well tolerated; the most common toxicities are skin toxicity (approximately equal to 90%) and diarrhoea (<30%). Development of anti-panitumumab antibodies (0.3% by ELISA) and grade 3-4 infusion reactions (<1%) are rare.
Conclusion: Panitumumab is an effective monotherapy option for patients with relapsed/refractory EGFR-expressing mCRC harbouring wild-type KRAS.