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

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common genetic cause of familial and sporadic Parkinson's disease (PD). That the most prevalent mutation, G2019S, leads to increased kinase activity has led to a concerted effort to identify LRRK2 kinase inhibitors as a potential disease-modifying therapy for PD. An internal medicinal chemistry effort identified several potent and highly selective compounds with favorable drug-like properties. Here, we characterize the pharmacological properties of cis-2,6-dimethyl-4-(6-(5-(1-methylcyclopropoxy)-1H-indazol-3-yl)pyrimidin-4-yl)morpholine (MLi-2), a structurally novel, highly potent, and selective LRRK2 kinase inhibitor with central nervous system activity. MLi-2 exhibits exceptional potency in a purified LRRK2 kinase assay in vitro (IC50 = 0.76 nM), a cellular assay monitoring dephosphorylation of LRRK2 pSer935 LRRK2 (IC50 = 1.4 nM), and a radioligand competition binding assay (IC50 = 3.4 nM). MLi-2 has greater than 295-fold selectivity for over 300 kinases in addition to a diverse panel of receptors and ion channels. Acute oral and subchronic dosing in MLi-2 mice resulted in dose-dependent central and peripheral target inhibition over a 24-hour period as measured by dephosphorylation of pSer935 LRRK2. Treatment of MitoPark mice with MLi-2 was well tolerated over a 15-week period at brain and plasma exposures >100× the in vivo plasma IC50 for LRRK2 kinase inhibition as measured by pSer935 dephosphorylation. Morphologic changes in the lung, consistent with enlarged type II pneumocytes, were observed in MLi-2-treated MitoPark mice. These data demonstrate the suitability of MLi-2 as a compound to explore LRRK2 biology in cellular and animal models.

A chemoenzymatic strategy for site-selective functionalization of native peptides and proteins.

The emergence of new therapeutic modalities requires complementary tools for their efficient syntheses. Availability of methodologies for site-selective modification of biomolecules remains a long-standing challenge, given the inherent complexity and the presence of repeating residues that bear functional groups with similar reactivity profiles. We describe a bioconjugation strategy for modification of native peptides relying on high site selectivity conveyed by enzymes. We engineered penicillin G acylases to distinguish among free amino moieties of insulin (two at amino termini and an internal lysine) and manipulate cleavable phenylacetamide groups in a programmable manner to form protected insulin derivatives. This enables selective and specific chemical ligation to synthesize homogeneous bioconjugates, improving yield and purity compared to the existing methods, and generally opens avenues in the functionalization of native proteins to access biological probes or drugs.

Discovery and Optimization of Potent, Selective, and Brain-Penetrant 1-Heteroaryl-1H-Indazole LRRK2 Kinase Inhibitors for the Treatment of Parkinson's Disease.

Inhibition of leucine-rich repeat kinase 2 (LRRK2) kinase activity represents a genetically supported, chemically tractable, and potentially disease-modifying mechanism to treat Parkinson's disease. Herein, we describe the optimization of a novel series of potent, selective, central nervous system (CNS)-penetrant 1-heteroaryl-1H-indazole type I (ATP competitive) LRRK2 inhibitors. Type I ATP-competitive kinase physicochemical properties were integrated with CNS drug-like properties through a combination of structure-based drug design and parallel medicinal chemistry enabled by sp3-sp2 cross-coupling technologies. This resulted in the discovery of a unique sp3-rich spirocarbonitrile motif that imparted extraordinary potency, pharmacokinetics, and favorable CNS drug-like properties. The lead compound, 25, demonstrated exceptional on-target potency in human peripheral blood mononuclear cells, excellent off-target kinase selectivity, and good brain exposure in rat, culminating in a low projected human dose and a pre-clinical safety profile that warranted advancement toward pre-clinical candidate enabling studies.

Synthesis and structure-activity relationship of 7-azaindole piperidine derivatives as CCR2 antagonists.

The synthesis and structure-activity relationship of a series of 7-azaindole piperidine derivatives are described. SAR studies led to the discovery of the potent CCR2 antagonists displaying IC(50) values in the nanomolar range. The representative compound 15 showed reasonable P450 and pharmacokinetics profile.

Substituted dipiperidine alcohols as potent CCR2 antagonists.

The synthesis and biological evaluation of a series of substituted dipiperidine alcohols are described. Structure-activity relationship studies led to the discovery of potent CCR2 antagonists displaying IC(50) values in the nanomolar or subnanomolar range. The cinnamoyl compounds had higher binding affinities than the corresponding urea analogs.

Structure-Activity Relationship of Novel and Selective Biaryl-Chroman GPR40 AgoPAMs.

A series of biaryl chromans exhibiting potent and selective agonism for the GPR40 receptor with positive allosteric modulation of endogenous ligands (AgoPAM) were discovered as potential therapeutics for the treatment of type II diabetes. Optimization of physicochemical properties through modification of the pendant aryl rings resulted in the identification of compound AP5, which possesses an improved metabolic profile while demonstrating sustained glucose lowering.

Synthesis, structure-activity relationship and in vivo antiinflammatory efficacy of substituted dipiperidines as CCR2 antagonists.

A series of substituted dipiperidine compounds have been synthesized and identified as selective CCR2 antagonists. Combining the most favorable substituents led to the discovery of remarkably potent CCR2 antagonists displaying IC50 values in the nanomolar range. Compound 7a had outstanding selectivity over CCR1, CCR3, CCR4, CCR5, CCR6, CCR7, and CCR8 and showed excellent efficacy in adjuvant-induced arthritis model, collagen-induced arthritis model, and allergic asthma model.

Discovery of a 3-(4-Pyrimidinyl) Indazole (MLi-2), an Orally Available and Selective Leucine-Rich Repeat Kinase 2 (LRRK2) Inhibitor that Reduces Brain Kinase Activity.

Leucine-rich repeat kinase 2 (LRRK2) is a large, multidomain protein which contains a kinase domain and GTPase domain among other regions. Individuals possessing gain of function mutations in the kinase domain such as the most prevalent G2019S mutation have been associated with an increased risk for the development of Parkinson's disease (PD). Given this genetic validation for inhibition of LRRK2 kinase activity as a potential means of affecting disease progression, our team set out to develop LRRK2 inhibitors to test this hypothesis. A high throughput screen of our compound collection afforded a number of promising indazole leads which were truncated in order to identify a minimum pharmacophore. Further optimization of these indazoles led to the development of MLi-2 (1): a potent, highly selective, orally available, brain-penetrant inhibitor of LRRK2.

The discovery of N-((2H-tetrazol-5-yl)methyl)-4-((R)-1-((5r,8R)-8-(tert-butyl)-3-(3,5-dichlorophenyl)-2-oxo-1,4-diazaspiro[4.5]dec-3-en-1-yl)-4,4-dimethylpentyl)benzamide (SCH 900822): a potent and selective glucagon receptor antagonist.

A novel series of spiroimidazolone-based antagonists of the human glucagon receptor (hGCGR) has been developed. Our efforts have led to compound 1, N-((2H-tetrazol-5-yl)methyl)-4-((R)-1-((5r,8R)-8-(tert-butyl)-3-(3,5-dichlorophenyl)-2-oxo-1,4-diazaspiro[4.5]dec-3-en-1-yl)-4,4-dimethylpentyl)benzamide (SCH 900822), a potent hGCGR antagonist with exceptional selectivity over the human glucagon-like peptide-1 receptor. Oral administration of 1 lowered 24 h nonfasting glucose levels in imprinting control region mice on a high fat diet with diet-induced obesity following single oral doses of 3 and 10 mg/kg. Furthermore, compound 1, when dosed orally, was found to decrease fasting blood glucose at 30 mg/kg in a streptozotocin-treated, diet-induced obesity mouse pharmacodynamic assay and blunt exogenous glucagon-stimulated glucose excursion in prediabetic mice.

A novel method for the preparation of 4-arylimidazolones.

A series of 4-arylimidazolones have been accessed via late-stage, palladium-mediated arylation of acetone- and cyclohexanone-derived 4-chloroimidazolones. The 4-chloroimidazolones were prepared via a novel rearrangement of the corresponding imidazolone N-oxides. This communication serves as an expansion of chemistry originally developed for our glucagon receptor antagonist program.

Synthesis and biological evaluation of phenyl piperidine derivatives as CCR2 antagonists.

A series of phenyl piperidine derivatives possessing potent and selective CCR2 antagonist activity is reported. Structure-activity relationship (SAR) studies have established that incorporation of a second ring system adjacent to the aryl piperidine plays an important role in determining the CCR2 potency. Both a second piperidine ring and a 1,3-substituted cyclopentylamine have been probed as linkers. For the cyclopentylamine series, the 1S,3R-configuration exhibits much higher affinity for hCCR2 than the 1R,3S-configuration. Compound 3g shows good selectivity over CCR1, CCR3, 5-HT and has an excellent P450 profile.

Asymmetric synthesis of (2S,3R)-capreomycidine and the total synthesis of capreomycin IB.

A 27 step total synthesis of the tuberculostatic macrocyclic peptide antibiotic capreomycin IB has been accomplished. The synthesis features the use of an enolate-aldimine condensation between a chiral glycine aluminum enolate and the benzyl imine of 3-tert-butyldimethylsiloxy-propanal as a means of preparing the cyclic guanidine amino acid (2S,3R)-capreomycidine. Additionally, a Hofmann rearrangement was exacted on a late-stage pentapeptide in order to transform an asparagine residue into a diaminopropanoic acid residue.