Abstract

Anaplastic lymphoma kinase (ALK)-positive non–small-cell lung cancer most commonly arises through EML4 (Echinoderm Microtuble Like 4)-ALK chromosomal fusion. We have previously demonstrated that combination of the ALK inhibitor crizotinib with the MEK inhibitor selumetinib was highly effective at reducing cell viability of ALK-positive non–small-cell lung cancer (H3122) cells. In this study, we further investigated the efficacy of crizotinib and selumetinib combination therapy in an in vivo xenograft model of ALK-positive lung cancer. Crizotinib decreased tumor volume by 52% compared with control, and the drug combination reduced tumor growth compared with crizotinib. In addition, MEK inhibition alone reduced tumor growth by 59% compared with control. Crizotinib and selumetinib alone and in combination were nontoxic at the dose of 25 mg/kg, with values for ALT (<80 U/l) and creatinine (<2 mg/dl) within the normal range. Our results support the combined use of crizotinib with selumetinib in ALK-positive lung cancer but raise the possibility that a sufficient dose of an MEK inhibitor alone may be as effective as adding an MEK inhibitor to an ALK inhibitor.