Automated algorithm development to assess survival of human neurons using longitudinal single-cell tracking: Application to synucleinopathy.

The development of phenotypic assays with appropriate analyses is an important step in the drug discovery process. Assays using induced pluripotent stem cell (iPSC)-derived human neurons are emerging as powerful tools for drug discovery in neurological disease. We have previously shown that longitudinal single cell tracking enabled the quantification of survival and death of neurons after overexpression of α-synuclein with a familial Parkinson's disease mutation (A53T). The reliance of this method on manual counting, however, rendered the process labor intensive, time consuming and error prone. To overcome these hurdles, we have developed automated detection algorithms for neurons using the BioStation CT live imaging system and CL-Quant software. In the current study, we use these algorithms to successfully measure the risk of neuronal death caused by overexpression of α-synuclein (A53T) with similar accuracy and improved consistency as compared to manual counting. This novel method also provides additional key readouts of neuronal fitness including total neurite length and the number of neurite nodes projecting from the cell body. Finally, the algorithm reveals the neuroprotective effects of brain-derived neurotrophic factor (BDNF) treatment in neurons overexpressing α-synuclein (A53T). These data show that an automated algorithm improves the consistency and considerably shortens the analysis time of assessing neuronal health, making this method advantageous for small molecule screening for inhibitors of synucleinopathy and other neurodegenerative diseases.

Patient-derived three-dimensional cortical neurospheres to model Parkinson's disease.

There are currently no preventive or disease-modifying therapies for Parkinson's Disease (PD). Failures in clinical trials necessitate a re-evaluation of existing pre-clinical models in order to adopt systems that better recapitulate underlying disease mechanisms and better predict clinical outcomes. In recent years, models utilizing patient-derived induced pluripotent stem cells (iPSC) have emerged as attractive models to recapitulate disease-relevant neuropathology in vitro without exogenous overexpression of disease-related pathologic proteins. Here, we utilized iPSC derived from patients with early-onset PD and dementia phenotypes that harbored either a point mutation (A53T) or multiplication at the α-synuclein/SNCA gene locus. We generated a three-dimensional (3D) cortical neurosphere culture model to better mimic the tissue microenvironment of the brain. We extensively characterized the differentiation process using quantitative PCR, Western immunoblotting and immunofluorescence staining. Differentiated and aged neurospheres revealed alterations in fatty acid profiles and elevated total and pathogenic phospho-α-synuclein levels in both A53T and the triplication lines compared to their isogenic control lines. Furthermore, treatment of the neurospheres with a small molecule inhibitor of stearoyl CoA desaturase (SCD) attenuated the protein accumulation and aberrant fatty acid profile phenotypes. Our findings suggest that the 3D cortical neurosphere model is a useful tool to interrogate targets for PD and amenable to test small molecule therapeutics.

A Brain-Penetrant Stearoyl-CoA Desaturase Inhibitor Reverses α-Synuclein Toxicity.

Increasing evidence has shown that Parkinson's disease (PD) impairs midbrain dopaminergic, cortical and other neuronal subtypes in large part due to the build-up of lipid- and vesicle-rich α-synuclein (αSyn) cytotoxic inclusions. We previously identified stearoyl-CoA desaturase (SCD) as a potential therapeutic target for synucleinopathies. A brain-penetrant SCD inhibitor, YTX-7739, was developed and has entered Phase 1 clinical trials. Here, we report the efficacy of YTX-7739 in reversing pathological αSyn phenotypes in various in vitro and in vivo PD models. In cell-based assays, YTX-7739 decreased αSyn-mediated neuronal death, reversed the abnormal membrane interaction of amplified E46K ("3K") αSyn, and prevented pathological phenotypes in A53T and αSyn triplication patient-derived neurospheres, including dysregulated fatty acid profiles and pS129 αSyn accumulation. In 3K PD-like mice, YTX-7739 crossed the blood-brain barrier, decreased unsaturated fatty acids, and prevented progressive motor deficits. Both YTX-7739 treatment and decreasing SCD activity through deletion of one copy of the SCD1 gene (SKO) restored the physiological αSyn tetramer-to-monomer ratio, dopaminergic integrity, and neuronal survival in 3K αSyn mice. YTX-7739 efficiently reduced pS129 + and PK-resistant αSyn in both human wild-type αSyn and 3K mutant mice similar to the level of 3K-SKO. Together, these data provide further validation of SCD as a PD therapeutic target and YTX-7739 as a clinical candidate for treating human α-synucleinopathies.

Non-clinical Pharmacology of YTX-7739: a Clinical Stage Stearoyl-CoA Desaturase Inhibitor Being Developed for Parkinson's Disease.

Stearoyl-CoA desaturase (SCD) is a potential therapeutic target for Parkinson's and related neurodegenerative diseases. SCD inhibition ameliorates neuronal toxicity caused by aberrant α-synuclein, a lipid-binding protein implicated in Parkinson's disease. Its inhibition depletes monounsaturated fatty acids, which may modulate α-synuclein conformations and membrane interactions. Herein, we characterize the pharmacokinetic and pharmacodynamic properties of YTX-7739, a clinical-stage SCD inhibitor. Administration of YTX-7739 to rats and monkeys for 15 days caused a dose-dependent increase in YTX-7739 concentrations that were well-tolerated and associated with concentration-dependent reductions in the fatty acid desaturation index (FADI), the ratio of monounsaturated to saturated fatty acids. An approximate 50% maximal reduction in the carbon-16 desaturation index was observed in the brain, with comparable responses in the plasma and skin. A study with a diet supplemented in SCD products indicates that changes in brain C16 desaturation were due to local SCD inhibition, rather than to changes in systemic fatty acids that reach the brain. Assessment of pharmacodynamic response onset and reversibility kinetics indicated that approximately 7 days of dosing were required to achieve maximal responses, which persisted for at least 2 days after cessation of dosing. YTX-7739 thus achieved sufficient concentrations in the brain to inhibit SCD and produce pharmacodynamic responses that were well-tolerated in rats and monkeys. These results provide a framework for evaluating YTX-7739 pharmacology clinically as a disease-modifying therapy to treat synucleinopathies.

Inhibiting Stearoyl-CoA Desaturase Ameliorates α-Synuclein Cytotoxicity.

The lack of disease-modifying treatments for neurodegenerative disease stems in part from our rudimentary understanding of disease mechanisms and the paucity of targets for therapeutic intervention. Here we used an integrated discovery paradigm to identify a new therapeutic target for diseases caused by α-synuclein (α-syn), a small lipid-binding protein that misfolds and aggregates in Parkinson's disease and other disorders. Using unbiased phenotypic screening, we identified a series of compounds that were cytoprotective against α-syn-mediated toxicity by inhibiting the highly conserved enzyme stearoyl-CoA desaturase (SCD). Critically, reducing the levels of unsaturated membrane lipids by inhibiting SCD reduced α-syn toxicity in human induced pluripotent stem cell (iPSC) neuronal models. Taken together, these findings suggest that inhibition of fatty acid desaturation has potential as a therapeutic approach for the treatment of Parkinson's disease and other synucleinopathies.

Potent PDZ-Domain PICK1 Inhibitors that Modulate Amyloid Beta-Mediated Synaptic Dysfunction.

Protein interacting with C kinase (PICK1) is a scaffolding protein that is present in dendritic spines and interacts with a wide array of proteins through its PDZ domain. The best understood function of PICK1 is regulation of trafficking of AMPA receptors at neuronal synapses via its specific interaction with the AMPA GluA2 subunit. Disrupting the PICK1-GluA2 interaction has been shown to alter synaptic plasticity, a molecular mechanism of learning and memory. Lack of potent, selective inhibitors of the PICK1 PDZ domain has hindered efforts at exploring the PICK1-GluA2 interaction as a therapeutic target for neurological diseases. Here, we report the discovery of PICK1 small molecule inhibitors using a structure-based drug design strategy. The inhibitors stabilized surface GluA2, reduced Aß-induced rise in intracellular calcium concentrations in cultured neurons, and blocked long term depression in brain slices. These findings demonstrate that it is possible to identify potent, selective PICK1-GluA2 inhibitors which may prove useful for treatment of neurodegenerative disorders.

Discovery of a highly selective chemical inhibitor of matrix metalloproteinase-9 (MMP-9) that allosterically inhibits zymogen activation.

Aberrant activation of matrix metalloproteinases (MMPs) is a common feature of pathological cascades observed in diverse disorders, such as cancer, fibrosis, immune dysregulation, and neurodegenerative diseases. MMP-9, in particular, is highly dynamically regulated in several pathological processes. Development of MMP inhibitors has therefore been an attractive strategy for therapeutic intervention. However, a long history of failed clinical trials has demonstrated that broad-spectrum MMP inhibitors have limited clinical utility, which has spurred the development of inhibitors selective for individual MMPs. Attaining selectivity has been technically challenging because of sequence and structural conservation across the various MMPs. Here, through a biochemical and structural screening paradigm, we have identified JNJ0966, a highly selective compound that inhibited activation of MMP-9 zymogen and subsequent generation of catalytically active enzyme. JNJ0966 had no effect on MMP-1, MMP-2, MMP-3, MMP-9, or MMP-14 catalytic activity and did not inhibit activation of the highly related MMP-2 zymogen. The molecular basis for this activity was characterized as an interaction of JNJ0966 with a structural pocket in proximity to the MMP-9 zymogen cleavage site near Arg-106, which is distinct from the catalytic domain. JNJ0966 was efficacious in reducing disease severity in a mouse experimental autoimmune encephalomyelitis model, demonstrating the viability of this therapeutic approach. This discovery reveals an unprecedented pharmacological approach to MMP inhibition, providing an opportunity to improve selectivity of future clinical drug candidates. Targeting zymogen activation in this manner may also allow for pharmaceutical exploration of other enzymes previously viewed as intractable drug targets.

Addendum: The antibody aducanumab reduces Aß plaques in Alzheimer's disease.

This corrects the article DOI: 10.1038/nature21361.

The antibody aducanumab reduces Aß plaques in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by deposition of amyloid-ß (Aß) plaques and neurofibrillary tangles in the brain, accompanied by synaptic dysfunction and neurodegeneration. Antibody-based immunotherapy against Aß to trigger its clearance or mitigate its neurotoxicity has so far been unsuccessful. Here we report the generation of aducanumab, a human monoclonal antibody that selectively targets aggregated Aß. In a transgenic mouse model of AD, aducanumab is shown to enter the brain, bind parenchymal Aß, and reduce soluble and insoluble Aß in a dose-dependent manner. In patients with prodromal or mild AD, one year of monthly intravenous infusions of aducanumab reduces brain Aß in a dose- and time-dependent manner. This is accompanied by a slowing of clinical decline measured by Clinical Dementia Rating-Sum of Boxes and Mini Mental State Examination scores. The main safety and tolerability findings are amyloid-related imaging abnormalities. These results justify further development of aducanumab for the treatment of AD. Should the slowing of clinical decline be confirmed in ongoing phase 3 clinical trials, it would provide compelling support for the amyloid hypothesis.

Pharmacodynamics of Dimethyl Fumarate Are Tissue Specific and Involve NRF2-Dependent and -Independent Mechanisms.

AIMS: Gastro-resistant dimethyl fumarate (DMF) is an oral therapeutic indicated for the treatment of relapsing multiple sclerosis. Recent data suggest that a primary pharmacodynamic response to DMF treatment is activation of the nuclear factor (erythroid-derived 2)-like 2 (NRF2) pathway; however, the gene targets modulated downstream of NRF2 that contribute to DMF-dependent effects are poorly understood. RESULTS: Using wild-type and NRF2 knockout mice, we characterized DMF transcriptional responses throughout the brain and periphery to understand DMF effects in vivo and to explore the necessity of NRF2 in this process. Our findings identified tissue-specific expression of NRF2 target genes as well as NRF2-dependent and -independent gene regulation after DMF administration. Furthermore, using gene ontology, we identified common biological pathways that may be regulated by DMF and contribute to in vivo functional effects. INNOVATION: Together, these data suggest that DMF modulates transcription through multiple pathways, which has implications for the cytoprotective, immunomodulatory, and clinical properties of DMF. CONCLUSION: These findings provide further understanding of the DMF mechanism of action and propose potential therapeutic targets that warrant further investigation for treating neurodegenerative diseases. Antioxid. Redox Signal. 24, 1058-1071.

BIIB042, a novel γ-secretase modulator, reduces amyloidogenic Aß isoforms in primates and rodents and plaque pathology in a mouse model of Alzheimer's disease.

Reducing the production of larger aggregation-prone amyloid ß-peptides (Aß) remains an untested therapeutic approach for reducing the appearance and growth of Aß plaques in the brain, which are a hallmark pathological feature of Alzheimer's disease. γ-Secretase modulators (GSMs) are therapeutics that impact γ-secretase-dependent cleavage of amyloid precursor protein to promote the production of shorter Aß peptides that are less prone to aggregation and plaque deposition. This is accomplished without inhibiting overall γ-secretase function and cleavage of other substrates, which is believed to be a source of deleterious side effects. Here, we report the pharmacokinetic and pharmacodynamic properties of BIIB042, a novel bioavailable and brain-penetrant GSM. In cell-based assays, BIIB042 reduced the levels of Aß42, increased the levels of Aß38 and had little effect on the levels of Aß40, the most abundant Aß species. Similar pharmacodynamic properties were confirmed in the central nervous system and in plasma of mice and rats, and also in plasma of cynomolgus monkeys after a single oral dose of BIIB042. BIIB042 reduced Aß42 levels and Aß plaque burden in Tg2576 mice, which overexpress human amyloid precursor protein and serve as a model system for Alzheimer's disease. BIIB042 did not inhibit cleavage of other γ-secretase substrates in cell-based and in vivo signaling and cleavage assays. The pharmacodynamic effects of lowering Aß42 in the central nervous system coupled with demonstrated efficacy in reducing plaque pathology suggests modulation of γ-secretase, with molecules like BIIB042, is a compelling therapeutic approach for the treatment of Alzheimer's disease.

Dimethyl fumarate and monoethyl fumarate exhibit differential effects on KEAP1, NRF2 activation, and glutathione depletion in vitro.

Delayed-release dimethyl fumarate (also known as gastro-resistant dimethyl fumarate), an oral therapeutic containing dimethyl fumarate (DMF) as the active ingredient, is currently approved for the treatment of relapsing multiple sclerosis. DMF is also a component in a distinct mixture product with 3 different salts of monoethyl fumarate (MEF), which is marketed for the treatment of psoriasis. Previous studies have provided insight into the pharmacologic properties of DMF, including modulation of kelch-like ECH-associated protein 1 (KEAP1), activation of the nuclear factor (erythroid-derived 2)-like 2 (NRF2) pathway, and glutathione (GSH) modulation; however, those of MEF remain largely unexplored. Therefore, the aim of this study was to evaluate the in vitro effects of DMF and MEF on KEAP1 modification, activation of the NRF2 pathway, and GSH conjugation. Using mass spectrometry, DMF treatment resulted in a robust modification of specific cysteine residues on KEAP1. In comparison, the overall degree of KEAP1 modification following MEF treatment was significantly less or undetectable. Consistent with KEAP1 cysteine modification, DMF treatment resulted in nuclear translocation of NRF2 and a robust transcriptional response in treated cells, as did MEF; however, the responses to MEF were of a lower magnitude or distinct compared to DMF. DMF was also shown to produce an acute concentration-dependent depletion of GSH; however, GSH levels eventually recovered and rose above baseline by 24 hours. In contrast, MEF did not cause acute reductions in GSH, but did produce an increase by 24 hours. Overall, these studies demonstrate that DMF and MEF are both pharmacologically active, but have differing degrees of activity as well as unique actions. These differences would be expected to result in divergent effects on downstream biology.

JNJ-40255293, a novel adenosine A2A/A1 antagonist with efficacy in preclinical models of Parkinson's disease.

Adenosine A2A antagonists are believed to have therapeutic potential in the treatment of Parkinson's disease (PD). We have characterized the dual adenosine A2A/A1 receptor antagonist JNJ-40255293 (2-amino-8-[2-(4-morpholinyl)ethoxy]-4-phenyl-5H-indeno[1,2-d]pyrimidin-5-one). JNJ-40255293 was a high-affinity (7.5 nM) antagonist at the human A2A receptor with 7-fold in vitro selectivity versus the human A1 receptor. A similar A2A:A1 selectivity was seen in vivo (ED50's of 0.21 and 2.1 mg/kg p.o. for occupancy of rat brain A2A and A1 receptors, respectively). The plasma EC50 for occupancy of rat brain A2A receptors was 13 ng/mL. In sleep-wake encephalographic (EEG) studies, JNJ-40255293 dose-dependently enhanced a consolidated waking associated with a subsequent delayed compensatory sleep (minimum effective dose: 0.63 mg/kg p.o.). As measured by microdialysis, JNJ-40255293 did not affect dopamine and noradrenaline release in the prefrontal cortex and the striatum. However, it was able to reverse effects (catalepsy, hypolocomotion, and conditioned avoidance impairment in rats; hypolocomotion in mice) produced by the dopamine D2 antagonist haloperidol. The compound also potentiated the agitation induced by the dopamine agonist apomorphine. JNJ-40255293 also reversed hypolocomotion produced by the dopamine-depleting agent reserpine and potentiated the effects of l-dihydroxyphenylalanine (L-DOPA) in rats with unilateral 6-hydroxydopamine-induced lesions of the nigro-striatal pathway, an animal model of Parkinson's disease. Extrapolating from the rat receptor occupancy dose-response curve, the occupancy required to produce these various effects in rats was generally in the range of 60-90%. The findings support the continued research and development of A2A antagonists as potential treatments for PD.

Synapto-depressive effects of amyloid beta require PICK1.

Amyloid beta (Aß), a key component in the pathophysiology of Alzheimer's disease, is thought to target excitatory synapses early in the disease. However, the mechanism by which Aß weakens synapses is not well understood. Here we showed that the PDZ domain protein, protein interacting with C kinase 1 (PICK1), was required for Aß to weaken synapses. In mice lacking PICK1, elevations of Aß failed to depress synaptic transmission in cultured brain slices. In dissociated cultured neurons, Aß failed to reduce surface α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit 2, a subunit of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors that binds with PICK1 through a PDZ ligand-domain interaction. Lastly, a novel small molecule (BIO922) discovered through structure-based drug design that targets the specific interactions between GluA2 and PICK1 blocked the effects of Aß on synapses and surface receptors. We concluded that GluA2-PICK1 interactions are a key component of the effects of Aß on synapses.

Substituted thieno[2,3-d]pyrimidines as adenosine A2A receptor antagonists.

A novel series of benzyl substituted thieno[2,3-d]pyrimidines were identified as potent A2A receptor antagonists. Several five- and six-membered heterocyclic replacements for the optimized methylfuran were explored. Select compounds effectively reverse catalepsy in mice when dosed orally.

Design and characterization of optimized adenosine A2A/A1 receptor antagonists for the treatment of Parkinson's disease.

The design and characterization of two, dual adenosine A(2A)/A(1) receptor antagonists in several animal models of Parkinson's disease is described. Compound 1 was previously reported as a potential treatment for Parkinson's disease. Further characterization of 1 revealed that it was metabolized to reactive intermediates that caused the genotoxicity of 1 in the Ames and mouse lymphoma L51784 assays. The identification of the metabolites enabled the preparation of two optimized compounds 13 and 14 that were devoid of the metabolic liabilities associated with 1. Compounds 13 and 14 are potent dual A(2A)/A(1) receptor antagonists that have excellent activity, after oral administration, across a number of animal models of Parkinson's disease including mouse and rat models of haloperidol-induced catalepsy, mouse and rat models of reserpine-induced akinesia, and the rat 6-hydroxydopamine (6-OHDA) lesion model of drug-induced rotation.

Fumarates promote cytoprotection of central nervous system cells against oxidative stress via the nuclear factor (erythroid-derived 2)-like 2 pathway.

Oxidative stress is central to the pathology of several neurodegenerative diseases, including multiple sclerosis, and therapeutics designed to enhance antioxidant potential could have clinical value. The objective of this study was to characterize the potential direct neuroprotective effects of dimethyl fumarate (DMF) and its primary metabolite monomethyl fumarate (MMF) on cellular resistance to oxidative damage in primary cultures of central nervous system (CNS) cells and further explore the dependence and function of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway in this process. Treatment of animals or primary cultures of CNS cells with DMF or MMF resulted in increased nuclear levels of active Nrf2, with subsequent up-regulation of canonical antioxidant target genes. DMF-dependent up-regulation of antioxidant genes in vivo was lost in mice lacking Nrf2 [Nrf2(-/-)]. DMF or MMF treatment increased cellular redox potential, glutathione, ATP levels, and mitochondrial membrane potential in a concentration-dependent manner. Treating astrocytes or neurons with DMF or MMF also significantly improved cell viability after toxic oxidative challenge in a concentration-dependent manner. This effect on viability was lost in cells that had eliminated or reduced Nrf2. These data suggest that DMF and MMF are cytoprotective for neurons and astrocytes against oxidative stress-induced cellular injury and loss, potentially via up-regulation of an Nrf2-dependent antioxidant response. These data also suggest DMF and MMF may function through improving mitochondrial function. The clinical utility of DMF in multiple sclerosis is being explored through phase III trials with BG-12, which is an oral therapeutic containing DMF as the active ingredient.

Discovery of 4-aminomethylphenylacetic acids as γ-secretase modulators via a scaffold design approach.

Starting from literature examples of nonsteroidal anti-inflammatory drugs (NSAIDs)-type carboxylic acid γ-secretase modulators (GSMs) and using a scaffold design approach, we identified 4-aminomethylphenylacetic acid 4 with a desirable γ-secretase modulation profile. Scaffold optimization led to the discovery of a novel chemical series, represented by 6b, having improved brain penetration. Further SAR studies provided analog 6q that exhibited a good pharmacological profile. Oral administration of 6q significantly reduced brain Aß42 levels in mice and rats.

Discovery of novel Cobactin-T based matrix metalloproteinase inhibitors via a ring closing metathesis strategy.

The discovery of potent N-hydroxyl caprolactam matrix metalloproteinase (MMP) inhibitors (6) based on the natural product Cobactin-T (2) is described. The synthetic method, which utilizes the ring closing metathesis reaction, is compatible to provide complementary (R) and (S) enantiomers. These compounds tested against MMP-2 and 9, show that the R stereochemistry (i.e., 16), which is opposite for that found in the natural product Cobactin-T is >1000-fold more active with IC(50) values of 0.2-0.6nM against both enzymes. The variation in the incorporation of the sulfonamide enzyme recognition element (Ar(2)XAr(1)SO(2)N(R(1)), 6), along with alterations in the RCM/double bond chemistry (R(2)) provided a series of sub nanomolar MMP inhibitors. For example, compounds 16 and 34 were found to be the most potent with IC(50) values against MMP-2 and MMP-9 found to be between 0.2 and 0.6nM with 34 being the most potent compound discovered (MMP-2 IC(50)=0.39nM and MMP-9 IC(50)=0.22nM). Compounds 16 and 34 showed acceptable drug-like properties in vivo with compound 34 showing oral bioavailability.