Pharmacodynamic Markers of LRRK2 Inhibition in Biofluids

Abstract

<jats:title>Abstract</jats:title><jats:p>Hyper-activated LRRK2 is linked to Parkinson’s disease susceptibility and progression. Quantitative measures of LRRK2 inhibition, especially in the brain, may be critical in the clinical development of successful LRRK2-targeting therapeutics. In this study, three different brain-penetrant and selective LRRK2 small-molecule kinase inhibitors (PFE-360, MLi2, and RA283) were orally administered to groups of cynomolgus macaques at different doses. Biofluid markers with proposed pharmacodynamic properties for assessing LRRK2 inhibition were measured from samples of blood, urine, and cerebral-spinal fluid (CSF). LRRK2 kinase inhibition led to consistent reduced pS935-LRRK2 and pRab10 proteins in blood mononuclear cells, reduced exosome LRRK2 protein and di-docosahexaenoyl (22:6) bis (monoacylglycerol) phosphate in urine, and reduced exosome LRRK2 and autophosphorylated pS1292-LRRK2 protein in CSF. Incomplete LRRK2 kinase inhibition reduced LRRK2 protein secretion in exosomes whereas high drug exposures may reduce both exosome and tissue levels of LRRK2 protein. These orthogonal markers for LRRK2 inhibition in urine and CSF can be used in combination with blood markers to non-invasively monitor the potency of LRRK2-targeting therapeutics in the brain and periphery.</jats:p>

Pharmacodynamic Biomarkers for Emerging LRRK2 Therapeutics

“…However, this phospho-to-total measure would be confounded in cases where total protein levels become low due to inhibitor treatment. A recent study evaluating LRRK2 inhibitors in non-human primate biofluids found that LRRK2 protein is unchanged in brain tissue but is diminished at varying levels in the periphery following acute treatment (Wang et al, 2020).…”

“…Studies using acute drug dosing strategies and kinase-dead LRRK2 mutants have provided evidence that the subcellular localization of LRRK2 is altered and reductions in kinase activity can lead to LRRK2 protein destabilization and degradation. A recent study in non-human primates showed that acute dosing with structurally distinct LRRK2 kinase inhibitors PFE-360 or MLi2 reduces total LRRK2 detection within exosomes isolated from urine and cerebral spinal fluid (CSF) (Wang et al, 2020). Additionally, there is evidence that LRRK2 kinase activity is crucial for maintaining steady-state levels of LRRK2.…”

“…Our recent efforts in non-human primates treated with LRRK2 kinase inhibitors revealed that no single biomarker in any single biofluid is likely to detail the complexity of drug interactions across the body (Wang et al, 2020). The usage of informative panels of biomarkers, rather than reliance on an individual marker, is commonplace in fields with relatively mature validated biomarkers such as those used in acute kidney injury (Siew et al, 2011).…”