There is a high demand for potent, selective, and brain-penetrant small molecule inhibitors of leucine-rich repeat kinase 2 (LRRK2) to test whether inhibition of LRRK2 kinase activity is a potentially viable treatment option for Parkinson's disease patients. Herein we disclose the use of property and structure-based drug design for the optimization of highly ligand efficient aminopyrimidine lead compounds. High throughput in vivo rodent cassette pharmacokinetic studies enabled rapid validation of in vitro-in vivo correlations. Guided by this data, optimal design parameters were established. Effective incorporation of these guidelines into our molecular design process resulted in the discovery of small molecule inhibitors such as GNE-7915 (18) and 19, which possess an ideal balance of LRRK2 cellular potency, broad kinase selectivity, metabolic stability, and brain penetration across multiple species. Advancement of GNE-7915 into rodent and higher species toxicity studies enabled risk assessment for early development.

Leucine-rich repeat kinase 2 (LRRK2) has drawn significant interest in the neuroscience research community because it is one of the most compelling targets for a potential disease-modifying Parkinson's disease therapy. Herein, we disclose structurally diverse small molecule inhibitors suitable for assessing the implications of sustained in vivo LRRK2 inhibition. Using previously reported aminopyrazole 2 as a lead molecule, we were able to engineer structural modifications in the solvent-exposed region of the ATP-binding site that significantly improve human hepatocyte stability, rat free brain exposure, and CYP inhibition and induction liabilities. Disciplined application of established optimal CNS design parameters culminated in the rapid identification of GNE-0877 (11) and GNE-9605 (20) as highly potent and selective LRRK2 inhibitors. The demonstrated metabolic stability, brain penetration across multiple species, and selectivity of these inhibitors support their use in preclinical efficacy and safety studies.

ABSTRACT:The modulation of LRRK2 kinase activity by a selective small molecule inhibitor has been proposed as a potentially viable treatment for Parkinson's disease. By using aminopyrazoles as aniline bioisosteres, we discovered a novel series of LRRK2 inhibitors. Herein, we describe our optimization effort that resulted in the identification of a highly potent, brain-penetrant aminopyrazole LRRK2 inhibitor (18) that addressed the liabilities (e.g., poor solubility and metabolic soft spots) of our previously disclosed anilinoaminopyrimidine inhibitors. In in vivo rodent PKPD studies, 18 demonstrated good brain exposure and engendered significant reduction in brain pLRRK2 levels post-ip administration. The strategies of bioisosteric substitution of aminopyrazoles for anilines and attenuation of CYP1A2 inhibition described herein have potential applications to other drug discovery programs. KEYWORDS: LRRK2, kinase inhibitor, Parkinson's disease, CYP1A2 inhibition P arkinson's disease (PD) is a neurodegenerative disorder that affects approximately 1% of the world's population over the age of 65. 1 Identification of a disease-modifying or neuroprotective therapeutic for PD patients remains a significant challenge. Recently, genetic research has revealed a connection between a missense mutation (G2019S) in the leucine-rich repeat kinase 2 (LRRK2) gene and a number of familial and idiopathic PD cases. 2−9 Significantly, multiple reports have shown that this mutation enhances the kinase activity of LRRK2. 10−17 The modulation of LRRK2 kinase activity by a selective small molecule inhibitor has therefore been proposed as a potential treatment for PD. 18−23 We recently reported the first disclosure of a series of highly potent, selective, and brain-penetrable anilino-pyrimidine LRRK2 inhibitors as exemplified by compound 1. 22,23 Examination of the liabilities of 1 and structurally similar analogues revealed (a) moderate to poor aqueous solubility (thermodynamic solubility of 1 at pH 7.4 < 0.9 μg/mL), (b) potential for ortho-quinoneimine reactive metabolite formation, and (c) a morpholinocarboxamide motif as a major site of metabolism as indicated by metabolite identification studies (MetID). In an effort to improve upon 1 and mitigate potential safety risks, we initiated a campaign to identify a suitable bioisosteric replacement for the aniline functionality. This approach resulted in the discovery of a novel series of highly selective aminopyrazole LRRK2 inhibitors.Docking experiments using a JAK-2-derived homology model of LRRK2 suggested that compound 1 binds in the ATP binding site of LRRK2 as shown in Figure 1. 22,23 In designing anilino-carboxamide replacements, we chose to retain the hinge binding diaminopyrimidine core as well as the C-5 trifluoromethyl group that interacts favorably with the methionine gatekeeper through van der Waal contacts. Additionally, our lead optimization efforts toward 1 established the importance of occupying the vector adjacent to the hingebinding anilino N-H motif (methoxy group in...

A conceptually novel approach to hetero Diels-Alder adducts of carbonyl compounds is described using as the key steps an antibody-mediated kinetic resolution of hydroxyenones followed by a ring-closure process. Various beta-hydroxyenones proved to be very good substrates for antibodies 84G3- and 93F3-catalyzed retro-aldol reactions, allowing the preparation of highly enantiomerically enriched (up to 99% ee) precursors of pyranones. An attractive feature of this methodology is the possibility to convert these acyclic-enantioenriched beta-hydroxyenones into tetrahydropyranones by a conventional Michael-type addition procedure or into the corresponding dihydropyranones using an alternative palladium-catalyzed oxidative ring closure. For the palladium-mediated cyclization, a biphasic system has been implemented that allows the direct preparation of enantiopure dihydropyranones from the corresponding racemic aldol precursors using a sequential antibody-resolution/palladium-cyclization strategy, without isolation of the intermediate enantioenriched hydroxyenones. This bioorganic route is best applied to the preparation of hetero Diels-Alder adducts otherwise derived from less nucleophilic dienes and unactivated dienophiles.