Metixene is an incomplete autophagy inducer in preclinical models of metastatic cancer and brain metastases.

Abstract

A paucity of chemotherapeutic options for metastatic brain cancer limits patient survival and portends poor clinical outcomes. Using a central nervous system (CNS) small-molecule inhibitor library of 320 agents known to be blood-brain barrier permeable and approved by the U.S. Food and Drug Administration, breast cancer brain metastases vulnerabilities were interrogated to identify an effective agent. Metixene, an antiparkinsonian drug, was identified as a top therapeutic agent that was capable of decreasing cellular viability and inducing cell death across different metastatic breast cancer subtypes. This agent significantly reduced mammary tumor size in orthotopic xenograft assays and improved survival in an intracardiac model of multiorgan site metastases. Metixene further extended survival in mice bearing intracranial xenografts and in an intracarotid model of multiple brain metastases. Functional analysis revealed that metixene induced incomplete autophagy through N-Myc Downstream Regulated 1 (NDRG1) phosphorylation thereby leading to caspase-mediated apoptosis in both primary and brain metastatic cells, regardless of cancer subtype or origin. CRISPR Cas9 knockout of NDRG1 led to autophagy completion and reversal of the metixene apoptotic effect. Metixene is a promising therapeutic agent against metastatic brain cancer, with minimal reported side effects in humans, which merits consideration for clinical translation.