Novel Indirect AMP-Activated Protein Kinase Activators: Identification of a Second-Generation Clinical Candidate with Improved Physicochemical Properties and Reduced hERG Inhibitory Activity

The therapeutic potential of mitochondrial toxins

When screening active compounds by phenotypic assays, we often encounter mitochondrial toxins, which are compounds that can affect mitochondrial functions. In normal cells, these toxins may have relatively low toxicity but can nonetheless show measurable effects even at low concentrations. On the other hand, in animals, mitochondrial toxins can exert severe toxicity. Mitochondrial toxins that act as inhibitors of respiratory chain complexes in oxidative phosphorylation (OXPHOS) are typically avoided during drug discovery efforts, as such compounds can directly promote lethal inhibition of pulmonary respiration. However, mitochondrial toxins could in fact have beneficial therapeutic effects. Anti-cancer strategies that target mitochondrial functions, particularly OXPHOS, have received increasing attention in recent years. In this review article we examine the significance of OXPHOS inhibitors as anti-cancer drug candidates and discuss compounds having microbial origins.

AMPK activation by ASP4132 inhibits non-small cell lung cancer cell growth

Activation of adenosine monophosphate-activated protein kinase (AMPK) is able to produce significant anti-non-small cell lung cancer (NSCLC) cell activity. ASP4132 is an orally active and highly effective AMPK activator. The current study tested its activity against NSCLC cells. In primary NSCLC cells and established cell lines (A549 and NCI-H1944) ASP4132 potently inhibited cell growth, proliferation and cell cycle progression as well as cell migration and invasion. Robust apoptosis activation was detected in ASP4132-treated NSCLC cells. Furthermore, ASP4132 treatment in NSCLC cells induced programmed necrosis, causing mitochondrial p53-cyclophilin D (CyPD)-adenine nucleotide translocase 1 (ANT1) association, mitochondrial depolarization and medium lactate dehydrogenase release. In NSCLC cells ASP4132 activated AMPK signaling, induced AMPKα1-ACC phosphorylation and increased AMPK activity. Furthermore, AMPK downstream events, including mTORC1 inhibition, receptor tyrosine kinases (PDGFRα and EGFR) degradation, Akt inhibition and autophagy induction, were detected in ASP4132-treated NSCLC cells. Importantly, AMPK inactivation by AMPKα1 shRNA, knockout (using CRISPR/Cas9 strategy) or dominant negative mutation (T172A) almost reversed ASP4132-induced anti-NSCLC cell activity. Conversely, a constitutively active AMPKα1 (T172D) mimicked and abolished ASP4132-induced actions in NSCLC cells. In vivo, oral administration of a single dose of ASP4132 largely inhibited NSCLC xenograft growth in SCID mice. AMPK activation, mTORC1 inhibition and EGFR-PDGFRα degradation as well as Akt inhibition and autophagy induction were detected in ASP4132-treated NSCLC xenograft tumor tissues. Together, activation of AMPK by ASP4132 potently inhibits NSCLC cell growth in vitro and in vivo.