Effect of selective LRRK2 kinase inhibition on nonhuman primate lung.

Inhibition of the kinase activity of leucine-rich repeat kinase 2 (LRRK2) is under investigation as a possible treatment for Parkinson's disease. However, there is no clinical validation as yet, and the safety implications of targeting LRRK2 kinase activity are not well understood. We evaluated the potential safety risks by comparing human and mouse LRRK2 mRNA tissue expression, by analyzing a Lrrk2 knockout mouse model, and by testing selective brain-penetrating LRRK2 kinase inhibitors in multiple species. LRRK2 mRNA tissue expression was comparable between species. Phenotypic analysis of Lrrk2 knockout mice revealed morphologic changes in lungs and kidneys, similar to those reported previously. However, in preclinical toxicity assessments in rodents, no pulmonary or renal changes were induced by two distinct LRRK2 kinase inhibitors. Both of these kinase inhibitors induced abnormal cytoplasmic accumulation of secretory lysosome-related organelles known as lamellar bodies in type II pneumocytes of the lung in nonhuman primates, but no lysosomal abnormality was observed in the kidney. The pulmonary change resembled the phenotype of Lrrk2 knockout mice, suggesting that this was LRRK2-mediated rather than a nonspecific or off-target effect. A biomarker of lysosomal dysregulation, di-docosahexaenoyl (22:6) bis(monoacylglycerol) phosphate (di-22:6-BMP), was also decreased in the urine of Lrrk2 knockout mice and nonhuman primates treated with LRRK2 kinase inhibitors. Our results suggest a role for LRRK2 in regulating lysosome-related lamellar bodies and that pulmonary toxicity may be a critical safety liability for LRRK2 kinase inhibitors in patients.

Which dyskinesia scale best detects treatment response?

Numerous scales assess dyskinesia in Parkinson's disease (PD), variably focusing on anatomical distribution, phenomenology, time, severity, and disability. No study has compared these scales and their relative ability to detect change related to an established treatment. We conducted a randomized placebo-controlled trial of amantadine, assessing dyskinesia at baseline and at 4 and 8 weeks using the following scales: Unified Dyskinesia Rating Scale (UDysRS), Lang-Fahn Activities of Daily Living Dyskinesia Rating Scale (LF), 26-Item Parkinson's Disease Dyskinesia scale (PDD-26), patient diaries, modified Abnormal Involuntary Movements Scale (AIMS), Rush Dyskinesia Rating Scale (RDRS), dyskinesia items from the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS), and Clinical Global Impression (severity and change: CGI-S, CGI-C). Scale order was randomized at each visit, but raters were aware of each scale as it was administered. Sensitivity to treatment was assessed using effect size. Sixty-one randomized dyskinetic PD subjects (31 amantadine, 30 placebo) completed the study. Four of the 8 scales (CGI-C, LF, PDD-26, and UDysRS) detected a significant treatment. The UDysRS Total Score showed the highest effect size (η(2) = 0.138) for detecting treatment-related change, with all other scales having effect sizes < 0.1. No scale was resistant to placebo effects. This study resolves 2 major issues useful for future testing of new antidyskinesia treatments: among tested scales, the UDysRS, having both subjective and objective dyskinesia ratings, is superior for detecting treatment effects; and the magnitude of the UDysRS effect size from amantadine sets a clear standard for comparison for new agents.