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Inhibitor treatment of peripheral mononuclear cells from Parkinson's disease patients further validates LRRK2 dephosphorylation as a pharmacodynamic biomarker.

ABSTRACT: Activating mutations in leucine-rich repeat kinase 2 (LRRK2) are strongly associated with increased risk of Parkinson's disease (PD). Thus, LRRK2 kinase inhibitors are in development as potential Parkinson's disease therapeutics. A reduction in the constitutive levels of phosphorylation on leucine-rich repeat kinase 2 (LRRK2) is currently used to measure target engagement of LRRK2 kinase inhibitors in cell and animal models. We aimed to determine if reduced phosphorylation of LRRK2 following inhibitor treatment is also a valid measure of target engagement in peripheral mononuclear cells from Parkinson's disease patients. Peripheral mononuclear cells from idiopathic Parkinson's disease patients and controls were treated ex vivo with two structurally distinct inhibitors of LRRK2, at four different doses, and immunoblotting was used to assess the reduction in LRRK2 phosphorylation at Ser910, Ser935, Ser955 and Ser973. Both inhibitors showed no acute toxicity in primary cells and both inhibitors reduced the constitutive phosphorylation of LRRK2 at all measured residues equally in both control and Parkinson's disease groups. Measuring the reduction in LRRK2 phosphorylation resulting from LRRK2 kinase inhibition, is thus a valid measure of acute peripheral target engagement in Parkinson's disease patients. This is important if LRRK2 kinase inhibitors are to be used in a clinical setting.

SUBMITTER: Perera G

PROVIDER: S-EPMC4977566 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Inhibitor treatment of peripheral mononuclear cells from Parkinson's disease patients further validates LRRK2 dephosphorylation as a pharmacodynamic biomarker.

Perera G G Ranola M M Rowe D B DB Halliday G M GM Dzamko N N

Scientific reports 20160809

Activating mutations in leucine-rich repeat kinase 2 (LRRK2) are strongly associated with increased risk of Parkinson's disease (PD). Thus, LRRK2 kinase inhibitors are in development as potential Parkinson's disease therapeutics. A reduction in the constitutive levels of phosphorylation on leucine-rich repeat kinase 2 (LRRK2) is currently used to measure target engagement of LRRK2 kinase inhibitors in cell and animal models. We aimed to determine if reduced phosphorylation of LRRK2 following inh ...[more]

PMID: 27503089

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Project description:Poly(ADP-ribose) polymerase (PARP) facilitates DNA repair and PARP inhibitors may potentiate the effect of DNA-damaging chemotherapeutic agents in patients with cancer. Collection of peripheral blood mononuclear cells (PBMCs) as a surrogate tissue to monitor PARP inhibitor pharmacodynamic effects has several advantages over tumor biopsy collection, including minimally invasive sample collection and the ability to collect multiple samples for longitudinal assessment of drug effect.Using our previously validated immunoassay for measuring poly(ADP-ribose) (PAR), a product of PARP, in tumor biopsies, we validated a method to quantify PAR levels in PBMCs to monitor the pharmacodynamic effects of the PARP inhibitor ABT-888 in clinical trials. The inter-individual variation in PAR levels was large. No significant difference (P?=?0.67) was measured between median baseline PAR levels in 144 healthy volunteers (131.7 pg/1×10(7) PBMCs [interquartile range, 79.5-241.6]) and 49 patients with cancer (149.2 pg/1×10(7) PBMCs [interquartile range, 83.2-249.3]). In addition, PAR levels monitored in healthy volunteers over 3 weeks had considerable intra- and inter-individual variation (range, 44-1073 pg PAR/1×10(7) PBMCs). As a pharmacodynamic model, we quantified changes in PAR levels in human PBMCs treated ex vivo with clinically relevant concentrations of ABT-888. Of 40 healthy volunteer PBMC samples treated with ABT-888, 47.5% had greater than 50% PAR reduction compared to vehicle-treated controls. Considerable inter-sample heterogeneity in PAR levels was measured, and several ABT-888-insensitive samples were identified.Our results emphasize the importance of using a validated method to measure PAR levels, and support further investigation into the role of PARP in PBMCs. To this end, the PAR immunoassay has been validated for use with PBMCs and incorporated into clinical trials to assess PBMCs as a potential pharmacodynamic surrogate for tumor biopsies in clinical trials of PARP inhibitors.

Project description:Leucine-rich repeat kinase 2 (LRRK2) is a complex, multidomain protein which is considered a valuable target for potential disease-modifying therapeutic strategies for Parkinson's disease (PD). In mammalian cells and brain, LRRK2 is phosphorylated and treatment of cells with inhibitors of LRRK2 kinase activity can induce LRRK2 dephosphorylation at a cluster of serines including Ser910/935/955/973. It has been suggested that phosphorylation levels at these sites reflect LRRK2 kinase activity, however kinase-dead variants of LRRK2 or kinase activating variants do not display altered Ser935 phosphorylation levels compared to wild type. Furthermore, Ser910/935/955/973 are not autophosphorylation sites, therefore, it is unclear if inhibitor induced dephosphorylation depends on the activity of compounds on LRRK2 or on yet to be identified upstream kinases. Here we used a panel of 160 ATP competitive and cell permeable kinase inhibitors directed against all branches of the kinome and tested their activity on LRRK2 in vitro using a peptide-substrate-based kinase assay. In neuronal SH-SY5Y cells overexpressing LRRK2 we used compound-induced dephosphorylation of Ser935 as readout. In silico docking of selected compounds was performed using a modeled LRRK2 kinase structure. Receiver operating characteristic plots demonstrated that the obtained docking scores to the LRRK2 ATP binding site correlated with in vitro and cellular compound activity. We also found that in vitro potency showed a high degree of correlation to cellular compound induced LRRK2 dephosphorylation activity across multiple compound classes. Therefore, acute LRRK2 dephosphorylation at Ser935 in inhibitor treated cells involves a strong component of inhibitor activity on LRRK2 itself, without excluding a role for upstream kinases. Understanding the regulation of LRRK2 phosphorylation by kinase inhibitors aids our understanding of LRRK2 signaling and may lead to development of new classes of LRRK2 kinase inhibitors.

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Inhibitor treatment of peripheral mononuclear cells from Parkinson's disease patients further validates LRRK2 dephosphorylation as a pharmacodynamic biomarker.

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Inhibitor treatment of peripheral mononuclear cells from Parkinson's disease patients further validates LRRK2 dephosphorylation as a pharmacodynamic biomarker.

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