Inclusion Criteria: - Pathologic diagnosis of colorectal adenocarcinoma (diagnostic tissue obtained by tissue biopsy) - Metastatic colorectal carcinoma - Eastern Cooperative Oncology Group of 0, 1 or 2 - Documented evidence of disease progression during, or following treatment, with fluoropyrimidine, irinotecan and oxaliplatin chemotherapy for metastatic colorectal cancer - Radiographic documentation of disease progression during or within 6 months following the most recent chemotherapy regimen is required - Bidimensionally measurable disease - Tumor expressing EGFr by immunohistochemistry - At least 2 but no more than 3 prior chemotherapy regimens for metastatic colorectal cancer - Adequate hematologic, renal and hepatic function Exclusion Criteria: - Symptomatic brain metastases requiring treatment - Patient with a history of interstitial pneumonitis or pulmonary fibrosis or evidence of interstitial pneumonitis or pulmonary fibrosis - Use of systemic chemotherapy or radiotherapy within 30 days before enrollment - Prior epidermal growth factor receptor targeting agents - Prior anti-tumor therapies including prior experimental agents or approved anti-tumor small molecules and biologics of short (less than 1 week) serum half-life within 30 days before enrollment, or prior experimental or approved proteins with longer serum half-life (e.g., AvastinTM) within 6 weeks before enrollment