Dual Inhibition of the Epidermal Growth Factor Receptor with Cetuximab, an IgG1 Monoclonal Antibody, and Gefitinib, A Tyrosine Kinase Inhibitor, in Patients with Refractory Non-small Cell Lung Cancer (NSCLC): A Phase I Study

Abstract

To determine the optimal doses of the antiepidermal growth factor receptor (anti-EGFR) monoclonal antibody cetuximab and the EGFR tyrosine kinase inhibitor gefitinib when administered as a combination for patients with advanced/metastatic non-small cell lung cancer (NSCLC) previously treated with platinum-based chemotherapy. Patients with advanced/metastatic NSCLC treated with prior platinum-based chemotherapy received escalating doses of weekly cetuximab (100, 200, and 250 mg/m(2), IV) and fixed doses of gefitinib (250 mg/d, PO) until disease progression or unacceptable toxicity. Available tumor samples were analyzed for EGFR expression, EGFR gene copy number and mutations, and K-RAS mutations. Thirteen patients were enrolled in three cohorts. Treatment was generally well-tolerated at all doses. One grade 3 headache, observed on the first treatment cycle was initially considered dose-limiting toxicity (DLT); this event was eventually determined to be caused by a brain metastasis, not toxicity. Three cases of grade 3/4 hypomagnesemia and 1 case of grade 3 skin rash occurred in the highest-dose cohort. Grade 1/2 infusion reactions occurred in three patients without requiring treatment discontinuation. Four patients (31%) achieved stable disease, no responses were observed. None of the patients had EGFR mutations or gene amplification in their tumor samples. Dual EGFR inhibition with cetuximab and gefitinib is feasible; the combination can be safely administered and may have modest activity in advanced/metastatic NSCLC. Cetuximab 250 mg/m(2) weekly IV and gefitinib 250 mg/d PO is the recommended phase II dose, although the potential for late-onset hypomagnesemia warrants close monitoring of patients receiving this combined dosage.