MO019: Preclinical Efficacy of Direct AMPK Activation with a Novel Small Molecule–PXL770–For the Treatment of Autosomal Dominant Polycystic Kidney Disease
Authors: Gluais Dagorn Pascale , Buchholz Bjoern , Bange Hester , Blockken Laura , Moller David E , Hallakou-Bozec Sophie 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease. It is caused by mutations in the PKD1 gene, and to a lesser extent PKD2. In this context, accumulating evidence has suggested a potential role of reduced AMP-activated protein kinase (AMPK) signaling in modulating cyst growth. We assessed the potential effects of PXL770, a clinical stage direct allosteric AMPK activator in conventional ADPKD models—3D cyst growth/swelling in vitro and efficacy in an ADPKD mouse model.

METHOD
In vitro, PXL770 (0.5–50 µM) was tested in 3D cyst assays using: (i) principal-like Madin-Darby Canine Kidney cells (plMDCK) activated by forskolin 10 µM and (ii) ADPKD patient-derived primary cells activated by desmopressin 2.5 µM. In both assays AMPK activation was also assessed by western blotting.
In vivo, a kidney specific P18 tamoxifen induced Pkd1 KO mouse model (KspCad-CreERT2, Pkd1lox, lox—‘ADPKD mice’ [Lantinga-van Leeuwen IS, Hum Mol Genet 2007]) was used. Following Pkd1 inactivation at age 18–20 days, mice (n = 22 per group) received PXL770 75 mg/kg by oral gavage twice daily from 42 to 103 days old of age. Mice were treated until 50% of the untreated ADPKD group showed renal failure (blood urea level ≥20 mmol/L). Kidney weight and kidney histology were evaluated.

RESULTS
In plMDCK cysts, PXL770 dose dependently reduced cyst growth induced by forskolin by 30%, 65% and 82% at 10, 25 and 50 µM, respectively, compared with untreated control cysts (P &lt; 0.05). These results were confirmed in human cysts where PXL770 inhibited desmopressin induced cyst swelling measured by cyst area, −67% at 15 µM compared with untreated control cysts (P &lt; 0.001), and −115% at 50 µM (P &lt; 0.0001)—below cyst area observed in solvent unstimulated condition. Similar result was achieved with tolvaptan. PXL770-mediated AMPK activation was confirmed in both cyst assay systems.
Untreated ADPKD mice exhibited a significantly elevated level of blood urea compared with wild-type mice (+105%, P &lt; 0.01). The blood urea level was lowered in PXL770-treated mice compared with untreated animals (−47%, P &lt; 0.01). PXL770 significantly reduced total kidney weight (−29%, P &lt; 0.01) and total kidney to body weight ratio (−35%, P &lt; 0.01) compared with untreated ADPKD mice, without modifying the body weight. Untreated ADPKD mice demonstrated extensive renal epithelial cyst formation, with a cystic area and a cystic index of 9.4 mm2 and 33%, respectively. In PXL770-treated ADPKD mice, the mean cystic area and the cystic index were lowered to 7.1 mm2 and 28%, respectively.

CONCLUSION
Direct AMPK activation with PXL770 strongly reduced cyst growth and swelling in vitro in canine and human models and was shown to produce considerable efficacy in an orthologous genetic mouse model of ADPKD. These results show the potential of direct allosteric AMPK activation in ADPKD and support the further development of PXL770 in this indication.