Small molecule screen employing patient-derived iPS hepatocytes identifies LRRK2 as a novel therapeutic target for Alpha1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency is a life-threatening condition caused by inheritance of the SERPINA1 gene Z variant. This single base pair mutation leads to protein misfolding, ER entrapment and gain of toxic function. Despite the significant unmet medical need presented by this disorder, there remain no approved medicines and the only curative option is liver transplantation. We hypothesized that an unbiased screen of human hepatocytes harbouring the Z mutation (ATZ) using small molecules targeted against protein degradation pathways would uncover novel biological insights of therapeutic relevance. Here we report the results of that screen performed in a patient-derived iPSC model of ATZ. Starting from 1,041 compounds we identified 14 targets capable of reducing polymer burden, including Leucine-rich repeat kinase-2 (LRRK2), a well-studied target in Parkinsons. Genetic deletion of LRRK2 in ATZ mice reduced polymers and associated fibrotic liver disease leading us to test a library of commercially available LRRK2 kinase inhibitors in both patient iPSC and CHO cell models. One of the molecules tested, CZC-25146, reduced polymer load, increased normal AAT secretion and reduced inflammatory cytokines with pharmacokinetic properties supporting its potential use for treating liver diseases. We therefore tested CZC-25146 in the ATZ mouse model and confirmed its efficacy for polymer reduction without signs of toxicity. Mechanistically, in both human and mouse models, our data show CZC-25146 inhibits LRRK2 kinase activity and induces autophagy. Cumulatively, these findings support the use of CZC-25146 and LRRK2 inhibitors in general in hepatic proteopathy disease research and as potential new treatment approaches for patients. One Sentence SummaryA small molecule screen in patient iPSCs with in vivo validation in mice identifies LRRK2 as a new therapeutic target for Alpha-1 Antitrypsin Deficiency.