Antitumor activity of the selective ALK inhibitor alectinib in models of intracranial metastases.

Abstract

The clinical efficacy of the anaplastic lymphoma kinase (ALK) inhibitor crizotinib has been demonstrated in ALK fusion-positive non-small cell lung cancer (NSCLC); however, brain metastases are frequent sites of initial failure in patients due to poor penetration of the central nervous system by crizotinib. Here, we examined the efficacy of a selective ALK inhibitor alectinib/CH5424802 in preclinical models of intracranial tumors. We established intracranial tumor implantation mouse models of EML4-ALK-positive NSCLC NCI-H2228 and examined the antitumor activity of alectinib in this model. Plasma distribution and brain distribution of alectinib were examined by quantitative whole-body autoradiography administrating a single oral dose of (14)C-labeled alectinib to rats. The drug permeability of alectinib was evaluated in Caco-2 cell. Alectinib resulted in regression of NCI-H2228 tumor in mouse brain and provided a survival benefit. In a pharmacokinetic study using rats, alectinib showed a high brain-to-plasma ratio, and in an in vitro drug permeability study using Caco-2 cells, alectinib was not transported by P-glycoprotein efflux transporter that is a key factor in blood-brain barrier penetration. We established intracranial tumor implantation models of EML4-ALK-positive NSCLC. Alectinib showed potent efficacy against intracranial EML4-ALK-positive tumor. These results demonstrated that alectinib might provide therapeutic opportunities for crizotinib-treated patients with brain metastases.