GNS561, a clinical-stage PPT1 inhibitor, is efficient against hepatocellular carcinoma via modulation of lysosomal functions

Abstract: Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer. Autophagy inhibitors have been extensively studied in cancer but, to date, none has reached efficacy in clinical trials.

Approach & Results: To explore the antitumor effects of GNS561, a new autophagy inhibitor, we first achieved in vitro assays using various human cancer cell lines. Having demonstrated that GNS561 displayed high liver tropism using mass spectrometry imaging, the potency of GNS561 on tumor was evaluated in vivo in two HCC models (human orthotopic patient-derived xenograft mouse model and diethylnitrosanime-induced cirrhotic immunocompetent rat model). Oral administration of GNS561 was well tolerated and decreased tumor growth in these two models. GNS561 mechanism of action was assessed in an HCC cell line, HepG2. We showed that due to its lysosomotropic properties, GNS561 could reach and inhibited its enzyme target, palmitoyl-protein thioesterase 1, resulting in lysosomal unbound Zn2+ accumulation, impairment of cathepsin activity, blockage of autophagic flux, altered location of mTOR, lysosomal membrane permeabilization, caspase activation and cell death.

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