Effect of selective LRRK2 kinase inhibition on nonhuman primate lung

Abstract

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.

MLi-2, a Potent, Selective, and Centrally Active Compound for Exploring the Therapeutic Potential and Safety of LRRK2 Kinase Inhibition

“…Consistent with observations made in LRRK2 KO rodents and nonhuman primates treated with less selective LRRK2 kinase inhibitors (Fuji et al, 2015), enlargement of type II pneumocytes (defined as very slight) was found in the lungs of all mice that received MLi-2 for 15 weeks. In addition to Ser935 dephosphorylation, we observed a significant reduction in total LRRK2 protein levels in the lung, although total LRRK2 levels were not completely ablated.…”

“…That LRRK2 inhibition by MLi-2 is well-tolerated by rodents agrees well with a recent report demonstrating good tolerability with another LRRK2 kinase inhibitor (PFE-06447475) after chronic administration (Daher et al, 2015). Both MLi-2 and PFE-06447475 have higher potency and selectivity for LRRK2 (Henderson et al, 2015) compared with GNE-0877 and GNE-7915 (Fuji et al, 2015), thus it seems probable that adverse effects observed with GNE-0877 and GNE-7915 are not LRRK2-mediated and are most probably the result of an as yet to be determined off target activity.…”

“…The lack of potency shift between unbound brain versus plasma underscores the lack of Pgp sensitivity and high brain penetration of MLi-2.Treatment with MLi-2 was found to be well tolerated, and no adverse effects of MLi-2 on body weight, food intake, or behavioral activity were observed at brain and plasma exposures .100Â the in vivo IC 50 for CNS LRRK2 kinase inhibition. The excellent tolerability of MLi-2 after subchronic dosing is particularly encouraging as a recent publication by Fuji et al, (2015) raised significant concerns over the tolerability of repeated administration of LRRK2 kinase inhibitors. That LRRK2 inhibition by MLi-2 is well-tolerated by rodents agrees well with a recent report demonstrating good tolerability with another LRRK2 kinase inhibitor (PFE-06447475) after chronic administration (Daher et al, 2015).…”

“…The utility of these molecules is, however, largely confined to in vitro assays owing to poor pharmacokinetic qualities and a lack of brain penetration. More recently, two novel LRRK2 kinase inhibitors (GNE-7915 and GNE-0877) were disclosed and used to probe the safety and tolerability profile of LRRK2 kinase inhibition in rodents and nonhuman primates (Estrada et al, 2012;Fuji et al, 2015). However, despite possessing improved biodistribution properties, both compounds inhibit several off-target kinases, and GNE-0877 has been associated with dose limiting toxicity in rats (Fuji et al, 2015).…”

Structural model of the dimeric Parkinson’s protein LRRK2 reveals a compact architecture involving distant interdomain contacts

“…However, the value of this therapeutic approach has been challenged by the observation that treatment with LRRK2 kinase inhibitors results in significant lung toxicity in primates (16). In addition, LRRK2 knockout rodent models display severe kidney phenotypes (17,18).…”