A Proposed Roadmap for Parkinson's Disease Proof of Concept Clinical Trials Investigating Compounds Targeting Alpha-Synuclein.
ABSTRACT: The convergence of human molecular genetics and Lewy pathology of Parkinson's disease (PD) have led to a robust, clinical-stage pipeline of alpha-synuclein (?-syn)-targeted therapies that have the potential to slow or stop the progression of PD and other synucleinopathies. To facilitate the development of these and earlier stage investigational molecules, the Michael J. Fox Foundation for Parkinson's Research convened a group of leaders in the field of PD research from academia and industry, the Alpha-Synuclein Clinical Path Working Group. This group set out to develop recommendations on preclinical and clinical research that can de-risk the development of ?-syn targeting therapies. This consensus white paper provides a translational framework, from the selection of animal models and associated end-points to decision-driving biomarkers as well as considerations for the design of clinical proof-of-concept studies. It also identifies current gaps in our biomarker toolkit and the status of the discovery and validation of ?-syn-associated biomarkers that could help fill these gaps. Further, it highlights the importance of the emerging digital technology to supplement the capture and monitoring of clinical outcomes. Although the development of disease-modifying therapies targeting ?-syn face profound challenges, we remain optimistic that meaningful strides will be made soon toward the identification and approval of disease-modifying therapeutics targeting ?-syn.
Project description:Neurodegenerative disorders with alpha-synuclein (?-syn) accumulation (synucleinopathies) include Parkinson's disease (PD), PD dementia, dementia with Lewy bodies and multiple system atrophy (MSA). Due to the involvement of toxic ?-syn aggregates in the molecular origin of these disorders, developing effective therapies targeting ?-syn is a priority as a disease-modifying alternative to current symptomatic treatments. Importantly, the clinical and pathological attributes of MSA make this disorder an excellent candidate as a synucleinopathy model for accelerated drug development. Recent therapeutic strategies targeting ?-syn in in vivo and in vitro models of MSA, as well as in clinical trials, have been focused on the pathological mechanisms of ?-syn synthesis, aggregation, clearance, and/or cell-to-cell propagation of its neurotoxic conformers. Here we summarize the most relevant approaches in this direction, with emphasis on their potential as general synucleinopathy modifiers, and enumerate research areas for potential improvement in MSA drug discovery.
2016-01-01 | S-EPMC4785838 | BioStudies
Project description:Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons located in the substantia nigra pars compacta and the presence of proteinaceous inclusions called Lewy bodies and Lewy neurites in numerous brain regions. Increasing evidence indicates that Lewy pathology progressively involves additional regions of the nervous system as the disease advances, and the prion-like propagation of ?-synuclein (?-syn) pathology promotes PD progression. Accordingly, the modulation of ?-syn transmission may be important for the development of disease-modifying therapies in patients with PD. Here, we demonstrate that ?-syn fibrils induce c-src activation in neurons, which depends on the Fc?RIIb-SHP-1/-2-c-src pathway and enhances signals for the uptake of ?-syn into neurons. Blockade of c-src activation inhibits the uptake of ?-syn and the formation of Lewy body-like inclusions. Furthermore, the blockade of c-src activation also inhibits the release of ?-syn via activation of autophagy. The brain permeable c-src inhibitor, saracatinib efficiently reduces ?-syn propagation into neighboring regions in an in vivo model system. These results suggest a new therapeutic target against progressive PD.
Project description:Increasing evidence suggests that the process of alpha-synuclein (?-syn) aggregation from monomers into amyloid fibrils and Lewy bodies, via oligomeric intermediates plays an essential role in the pathogenesis of different synucleinopathies, including Parkinson's disease (PD), multiple system atrophy and dementia with Lewy bodies (DLB). However, the nature of the toxic species and the mechanisms by which they contribute to neurotoxicity and disease progression remain elusive. Over the past two decades, significant efforts and resources have been invested in studies aimed at identifying and targeting toxic species along the pathway of ?-syn fibrillization. Although this approach has helped to advance the field and provide insights into the biological properties and toxicity of different ?-syn species, many of the fundamental questions regarding the role of ?-syn aggregation in PD remain unanswered, and no therapeutic compounds targeting ?-syn aggregates have passed clinical trials. Several factors have contributed to this slow progress, including the complexity of the aggregation pathways and the heterogeneity and dynamic nature of ?-syn aggregates. In the majority of experiment, the ?-syn samples used contain mixtures of ?-syn species that exist in equilibrium and their ratio changes upon modifying experimental conditions. The failure to quantitatively account for the distribution of different ?-syn species in different studies has contributed not only to experimental irreproducibility but also to misinterpretation of results and misdirection of valuable resources. Towards addressing these challenges and improving experimental reproducibility in Parkinson's research, we describe here a simple centrifugation-based filtration protocol for the isolation, quantification and assessment of the distribution of ?-syn monomers, oligomers and fibrils, in heterogeneous ?-syn samples of increasing complexity. The protocol is simple, does not require any special instrumentation and can be performed rapidly on multiple samples using small volumes. Here, we present and discuss several examples that illustrate the applications of this protocol and how it could contribute to improving the reproducibility of experiments aimed at elucidating the structural basis of ?-syn aggregation, seeding activity, toxicity and pathology spreading. This protocol is applicable, with slight modifications, to other amyloid-forming proteins.
Project description:Animal models that accurately recapitulate the accumulation of alpha-synuclein (?-syn) inclusions, progressive neurodegeneration of the nigrostriatal system and motor deficits can be useful tools for Parkinson's disease (PD) research. The preformed fibril (PFF) synucleinopathy model in rodents generally displays these PD-relevant features, however, the magnitude and predictability of these events is far from established. We therefore sought to optimize the magnitude of ?-syn accumulation and nigrostriatal degeneration, and to understand the time course of both. Rats were injected unilaterally with different quantities of ?-syn PFFs (8 or 16??g of total protein) into striatal sites selected to concentrate ?-syn inclusion formation in the substantia nigra pars compacta (SNpc). Rats displayed an ?-syn PFF quantity-dependent increase in the magnitude of ipsilateral SNpc inclusion formation at 2?months and bilateral loss of nigral dopamine neurons at 6?months. Unilateral 16??g PFF injection also resulted in modest sensorimotor deficits in forelimb adjusting steps associated with degeneration at 6?months. Bilateral injection of 16??g ?-syn PFFs resulted in symmetric bilateral degeneration equivalent to the ipsilateral nigral degeneration observed following unilateral 16??g PFF injection (~50% loss). Bilateral PFF injections additionally resulted in alterations in several gait analysis parameters. These ?-syn PFF parameters can be applied to generate a reproducible synucleinopathy model in rats with which to study pathogenic mechanisms and vet potential disease-modifying therapies.
Project description:Background:Leucine-rich kinase 2 (LRRK2)-linked Parkinson's disease (PD) is clinically indistinguishable from idiopathic PD (IPD). A pleiotropic neuropathology has been recognized but the majority of studies in LRRK2 p.G2019S patients reveal Lewy-type synucleinopathy as its principal histological substrate. To date no in vivo biomarkers of synucleinopathy have been found in LRRK2 mutation carriers. Objectives:We used real-time quaking-induced conversion (RT-QuIC) technique to assess the presence of alpha-synuclein (a-syn) aggregates in cerebrospinal fluid (CSF) of LRRK2 p.G2019S carriers. Methods:CSF samples of 51 subjects were analyzed: 15 LRRK2 p.G2019S PD, 10 IPD, 16 LRRK2 p.G2019S nonmanifesting carriers (NMC) and 10 healthy controls. The presence of parkinsonism and prodromal symptoms was assessed in all study subjects. Results:Forty percent (n = 6) LRRK2-PD, and 18.8% (n = 3) LRRK2-NMC had a positive a-syn RT-QuIC response. RT-QuIC detected IPD with 90% sensitivity and 80% specificity. No clinical differences were detected between LRRK2-PD patients with positive and negative RT-QuIC. A positive RT-QuIC result in LRRK2-NMC occurred in a higher proportion of subjects meeting the Movement Disorder Society research criteria for prodromal PD. Interpretation:RT-QuIC detects a-syn aggregation in CSF in a significant number of patients with LRRK2-PD, but less frequently than in IPD. A small percentage of LRRK2-NMC tested also positive. If appropriately validated in long-term studies with large number of mutation carriers, and hopefully, postmortem or in vivo confirmation of histopathology, RT-QuIC could contribute to the selection of candidates to receive disease modifying drugs, in particular treatments targeting a-syn deposition.
Project description:The pathologic accumulation and aggregation of ?-synuclein (?-syn) underlies Parkinson's disease (PD). The molecular mechanisms by which pathologic ?-syn causes neurodegeneration in PD are not known. Here, we found that pathologic ?-syn activates poly(adenosine 5'-diphosphate-ribose) (PAR) polymerase-1 (PARP-1), and PAR generation accelerates the formation of pathologic ?-syn, resulting in cell death via parthanatos. PARP inhibitors or genetic deletion of PARP-1 prevented pathologic ?-syn toxicity. In a feed-forward loop, PAR converted pathologic ?-syn to a more toxic strain. PAR levels were increased in the cerebrospinal fluid and brains of patients with PD, suggesting that PARP activation plays a role in PD pathogenesis. Thus, strategies aimed at inhibiting PARP-1 activation could hold promise as a disease-modifying therapy to prevent the loss of dopamine neurons in PD.
Project description:?-Synuclein (?-Syn) forms toxic intracellular protein inclusions and transmissible amyloid structures in Parkinson's disease (PD). Preventing ?-Syn self-assembly has become one of the most promising approaches in the search for disease-modifying treatments for this neurodegenerative disorder. Here, we describe the capacity of a small molecule (ZPD-2), identified after a high-throughput screening, to inhibit ?-Syn aggregation. ZPD-2 inhibits the aggregation of wild-type ?-Syn and the A30P and H50Q familial variants in vitro at substoichiometric compound:protein ratios. In addition, the molecule prevents the spreading of ?-Syn seeds in protein misfolding cyclic amplification assays. ZPD-2 is active against different ?-Syn strains and blocks their seeded polymerization. Treating with ZPD-2 two different PD Caenorhabditis elegans models that express ?-Syn either in muscle or in dopaminergic (DA) neurons substantially reduces the number of ?-Syn inclusions and decreases synuclein-induced DA neurons degeneration. Overall, ZPD-2 is a hit compound worth to be explored in order to develop lead molecules for therapeutic intervention in PD.
Project description:Intensive research efforts in the field of Parkinson's disease (PD) are focusing on identifying reliable biomarkers which possibly help physicians in predicting disease onset, diagnosis, and progression as well as evaluating the response to disease-modifying treatments. Given that abnormal alpha-synuclein (?-syn) accumulation is a primary component of PD pathology, this protein has attracted considerable interest as a potential biomarker for PD. Alpha-synuclein can be detected in several body fluids, including plasma, where it can be found as free form or in association with exosomes, small membranous vesicles secreted by virtually all cell types. Together with ?-syn accumulation, lysosomal dysfunctions seem to play a central role in the pathogenesis of PD, given the crucial role of lysosomes in the ?-syn degradation. In particular, heterozygous mutations in the GBA1 gene encoding lysosomal enzyme glucocerebrosidase (GCase) are currently considered as the most important risk factor for PD. Different studies have found that GCase deficiency leads to accumulation of ?-syn; whereas at the same time, increased ?-syn may inhibit GCase function, thus inducing a bidirectional pathogenic loop. In this study, we investigated whether changes in plasma total and exosome-associated ?-syn could correlate with disease status and clinical parameters in PD and their relationship with GCase activity. We studied 39 PD patients (mean age: 65.2 ± 8.9; men: 25), without GBA1 mutations, and 33 age-matched controls (mean age: 61.9 ± 6.2; men: 15). Our results showed that exosomes from PD patients contain a greater amount of ?-syn compared to healthy subjects (25.2 vs. 12.3 pg/mL, p < 0.001) whereas no differences were found in plasma total ?-syn levels (15.7 vs. 14.8 ng/mL, p = 0.53). Moreover, we highlighted a significant increase of plasma exosomal ?-syn/total ?-syn ratio in PD patients (1.69 vs. 0.89, p < 0.001), which negatively correlates with disease severity (p = 0.014). Intriguingly, a significant inverse correlation between GCase activity and this ratio in PD subjects was found (p = 0.006). Additional and large-scale studies comparing GCase activity and pathological protein levels will be clearly needed to corroborate these data and determine whether the association between key players in the lysosomal system and ?-syn can be used as diagnostic or prognostic biomarkers for PD.
Project description:Phosphorylated alpha-synuclein (p-alpha-syn) deposits, one of the neuropathological hallmarks of Parkinson's disease (PD), have recently been detected in dermal nerve fibres in PD patients with good specificity and sensitivity. Here, we studied whether p-alpha-syn may serve as a biomarker in patients with a high risk of developing PD, such as those with REM sleep behaviour disorder (RBD). We compared the presence and distribution of p-alpha-syn deposits in dermal nerve fibres in 18 patients with RBD, 25 patients with early PD and 20 normal controls. Skin biopsy was taken at C7, Th10, and the upper and lower leg. Presynaptic dopamine transporter imaging using FP-CIT-SPECT was performed in all patients with RBD and in 11 patients with PD. All RBD patients underwent olfactory function testing. The likelihood ratio (LR) for prodromal PD was calculated for each patient based on published research criteria. Skin serial sections were assessed by double-immunofluorescence labelling with antibodies to pSer129-alpha-syn under blinded conditions. P-alpha-syn was visualized in 10/18 patients with RBD (sensitivity of 55.6%) and in 20/25 early PD patients (sensitivity of 80%) but in none of the controls (specificity of 100%). The percentage of dermal structures innervated by p-alpha-syn-positive fibres was negatively correlated with dopamine transporter binding in the FP-CIT-SPECT (? = -0.377, p = 0.048), with olfactory function (? = -0.668, p = 0.002), and positively correlated with the total LR for RBD to present prodromal PD (? = 0.531, p = 0.023). Dermal p-alpha-syn can be considered a peripheral histopathological marker of synucleinopathy and can be detected in a subgroup of RBD patients presumably representing prodromal PD. Dermal p-alpha-syn is detectable in RBD patients without PD motor symptoms, thereby stratifying a patient group that is of great interest for clinical trials testing disease-modifying drugs.
Project description:Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are progressive neurodegenerative diseases for which there is no disease-modifying treatment. PD and DLB are characterized by aggregation of the synaptic protein ?-synuclein, and there is compelling evidence to suggest that progression of these diseases is associated with the trans-cellular spread of pathogenic ?-synuclein through the brains of afflicted individuals. Therapies targeting extracellular, pathogenic ?-synuclein may therefore hold promise for slowing or halting disease progression. In this regard, it has been suggested that highly-selective antibodies can be administered as therapeutic agents targeting pathogenic proteins. In the current study, we screened a series of antibodies using multiple selection criterion to identify those that selectively bind pathogenic ?-synuclein and show potent inhibition of pathology seeding in a neuronal model of ?-synucleinopathy. A lead antibody was tested in a mouse model of PD, and it was able to reduce the spread of ?-synuclein pathology in the brain and attenuate dopamine reductions in the striatum. This study highlights the therapeutic potential of ?-synuclein immunotherapy for the treatment of PD and DLB, and provides a framework for screening of ?-synuclein antibodies to identify those with preferred properties.