An exploratory clinical study of p38α kinase inhibition in Alzheimer's disease

miRNAs in cerebrospinal fluid associated with Alzheimer's disease: A systematic review and pathway analysis using a data mining and machine learning approach

Alzheimer's disease (AD) is the most common type and accounts for 60%-70% of the reported cases of dementia. MicroRNAs (miRNAs) are small non-coding RNAs that play a crucial role in gene expression regulation. Although the diagnosis of AD is primarily clinical, several miRNAs have been associated with AD and considered as potential markers for diagnosis and progression of AD. We sought to match AD-related miRNAs in cerebrospinal fluid (CSF) found in the GeoDataSets, evaluated by machine learning, with miRNAs listed in a systematic review, and a pathway analysis. Using machine learning approaches, we identified most differentially expressed miRNAs in Gene Expression Omnibus (GEO), which were validated by the systematic review, using the acronym PECO-Population (P): Patients with AD, Exposure (E): expression of miRNAs, Comparison (C): Healthy individuals, and Objective (O): miRNAs differentially expressed in CSF. Additionally, pathway enrichment analysis was performed to identify the main pathways involving at least four miRNAs selected. Four miRNAs were identified for differentiating between patients with and without AD in machine learning combined to systematic review, and followed the pathways analysis: miRNA-30a-3p, miRNA-193a-5p, miRNA-143-3p, miRNA-145-5p. The pathways epidermal growth factor, MAPK, TGF-beta and ATM-dependent DNA damage response, were regulated by these miRNAs, but only the MAPK pathway presented higher relevance after a randomic pathway analysis. These findings have the potential to assist in the development of diagnostic tests for AD using miRNAs as biomarkers, as well as provide understanding of the relationship between different pathophysiological mechanisms of AD.

Neuroinflammation of Microglial Regulation in Alzheimer's Disease: Therapeutic Approaches

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system that is clinically characterized by a progressive decline in memory and cognitive function. The pathogenesis of AD is intricate and not yet fully understood. Neuroinflammation, particularly microglial activation-mediated neuroinflammation, is believed to play a crucial role in increasing the risk, triggering the onset, and hastening the progression of AD. Modulating microglial activation and regulating microglial energy metabolic disorder are seen as promising strategies to intervene in AD. The application of anti-inflammatory drugs and the targeting of microglia for the prevention and treatment of AD has emerged as a new area of research interest. This article provides a comprehensive review of the role of neuroinflammation of microglial regulation in the development of AD, exploring the connection between microglial energy metabolic disorder, neuroinflammation, and AD development. Additionally, the advancements in anti-inflammatory and microglia-regulating therapies for AD are discussed.

A microglia clonal inflammatory disorder in Alzheimer's Disease

Somatic genetic heterogeneity resulting from post-zygotic DNA mutations is widespread in human tissues and can cause diseases, however few studies have investigated its role in neurodegenerative processes such as Alzheimer's Disease (AD). Here we report the selective enrichment of microglia clones carrying pathogenic variants, that are not present in neuronal, glia/stromal cells, or blood, from patients with AD in comparison to age-matched controls. Notably, microglia-specific AD-associated variants preferentially target the MAPK pathway, including recurrent CBL ring-domain mutations. These variants activate ERK and drive a microglia transcriptional program characterized by a strong neuro-inflammatory response, both in vitro and in patients. Although the natural history of AD-associated microglial clones is difficult to establish in human, microglial expression of a MAPK pathway activating variant was previously shown to cause neurodegeneration in mice, suggesting that AD-associated neuroinflammatory microglial clones may contribute to the neurodegenerative process in patients.

Phase 2A Learnings Incorporated into RewinD-LB, a Phase 2B Clinical Trial of Neflamapimod in Dementia with Lewy Bodies

BACKGROUND

In an exploratory 91-participant phase 2a clinical trial (AscenD-LB, NCT04001517) in dementia with Lewy bodies (DLB), neflamapimod showed improvement over placebo on multiple clinical endpoints. To confirm those results, a phase 2b clinical study (RewinD-LB, NCT05869669 ) that is similar to AscenD-LB has been initiated.

OBJECTIVES

To optimize the choice of patient population, primary endpoint, and biomarker evaluations in RewinD-LB.

DESIGN

Evaluation of the efficacy results from AscenD-LB, the main results of which, and a re-analysis after stratification for absence or presence of AD co-pathology (assessed by plasma ptau181), have been published. In addition, the MRI data from a prior phase 2a clinical trial in Early Alzheimer's disease (AD), were reviewed.

SETTING

22 clinical sites in the US and 2 in the Netherlands.

PARTICIPANTS

Probable DLB by consensus criteria and abnormal dopamine uptake by DaTscan™ (Ioflupane I123 SPECT).

INTERVENTION

Neflamapimod 40mg capsules or matching placebo capsules, twice-a-day (BID) or three-times-a-day (TID), for 16 weeks.

MEASUREMENTS

6-test Neuropsychological Test Battery (NTB) assessing attention and executive function, Clinical Dementia Rating Sum-of-Boxes (CDR-SB), Timed Up and Go (TUG), International Shopping List Test (ISLT).

RESULTS

Within AscenD-LB, patients without evidence of AD co-pathology exhibited a neflamapimod treatment effect that was greater than that in the overall population and substantial (cohen's d effect size vs. placebo ≥ for CDR-SB, TUG, Attention and ISLT-recognition). In addition, the CDR-SB and TUG performed better than the cognitive tests to demonstrate neflamapimod treatment effect in comparison to placebo. Further, clinical trial simulations indicate with 160-patients (randomized 1:1), RewinD-LB conducted in patients without AD co-pathology has >95% (approaching 100%) statistical power to detect significant improvement over placebo on the CDR-SB. Preliminary evidence of positive treatment effects on beta functional connectivity by EEG and basal forebrain atrophy by MRI were obtained in AscenD-LB and the Early AD study, respectively.

CONCLUSION

In addition to use of a single dose regimen of neflamapimod (40mg TID), key distinctions between phase 2b and phase 2a include RewinD-LB (1) excluding patients with AD co-pathology, (2) having CDR-SB as the primary endpoint, and (3) having MRI studies to evaluate effects on basal forebrain atrophy.

Targeting protein kinases for the treatment of Alzheimer's disease: Recent progress and future perspectives

Alzheimer's disease (AD) is a serious neurodegenerative disease characterized by memory impairment, mental retardation, impaired motor balance, loss of self-care and even death. Among the complex and diverse pathological changes in AD, protein kinases are deeply involved in abnormal phosphorylation of Tau proteins to form intracellular neuronal fiber tangles, neuronal loss, extracellular β-amyloid (Aβ) deposits to form amyloid plaques, and synaptic disturbances. As a disease of the elderly, the growing geriatric population is directly driving the market demand for AD therapeutics, and protein kinases are potential targets for the future fight against AD. This perspective provides an in-depth look at the role of the major protein kinases (GSK-3β, CDK5, p38 MAPK, ERK1/2, and JNK3) in the pathogenesis of AD. At the same time, the development of different protein kinase inhibitors and the current state of clinical advancement are also outlined.

Cancer drugs with high repositioning potential for Alzheimer's disease

INTRODUCTION

Despite the recent full FDA approval of lecanemab, there is currently no disease modifying therapy (DMT) that can efficiently slow down the progression of Alzheimer's disease (AD) in the general population. This statement emphasizes the need to identify novel DMTs in the shortest time possible to prevent a global epidemic of AD cases as the world population experiences an increase in lifespan.

AREAS COVERED

Here, we review several classes of anti-cancer drugs that have been or are being investigated in Phase II/III clinical trials for AD, including immunomodulatory drugs, RXR agonists, sex hormone therapies, tyrosine kinase inhibitors, and monoclonal antibodies.

EXPERT OPINION

Given the overall course of brain pathologies during the progression of AD, we express a great enthusiasm for the repositioning of anti-cancer drugs as possible AD DMTs. We anticipate an increasing number of combinatorial therapy strategies to tackle AD symptoms and their underlying pathologies. However, we strongly encourage improvements in clinical trial study designs to better assess target engagement and possible efficacy over sufficient periods of drug exposure.

Emerging drugs for dementia with Lewy Bodies: a review of Phase II & III trials

INTRODUCTION

Despite faster cognitive decline and greater negative impact on patients and family caregivers, drug development efforts in Dementia with Lewy Bodies (DLB) fall behind those for Alzheimer's Disease (AD). Current off-label drug DLB treatment options are limited to symptomatic agents developed to address cognitive deficits in AD, motor deficits in Parkinson's Disease, or behavioral symptoms in psychiatric disease. Aided by recent improvements in DLB diagnosis, a new focus on the development of disease-modifying agents (DMA) is emerging.

AREAS COVERED

Driven by evidence supporting different pathological mechanisms in DLB and PDD, this review assesses the evidence on symptomatic drug treatments and describes current efforts in DMA development in DLB. Specifically, our goals were to: (1) review evidence supporting the use of symptomatic drug treatments in DLB; (2) review the current DMA pipeline in DLB with a focus on Phase II and III clinical trials; and (3) identify potential issues with the development of DMA in DLB. Included in this review were completed and ongoing drug clinical trials in DLB registered on ClinicalTrials.gov (no time limits set for the search) or disseminated at the 2023 international conference on Clinical Trials in AD. Drug clinical trials registered in non-US clinical trial registries were not included.

EXPERT OPINION

Adoption of current symptomatic drug treatments used off-label in DLB relied on efficacy of benefits in other disorders rather than evidence from randomized controlled clinical trials. Symptoms remain difficult to manage. Several DMA drugs are currently being evaluated as either repurposing candidates or novel small molecules. Continued improvement in methodological aspects including development of DLB-specific outcome measures and biomarkers is needed to move the field of DMA drug development forward.

Alzheimer's Disease: Novel Targets and Investigational Drugs for Disease Modification

Novel agents addressing non-amyloid, non-tau targets in Alzheimer's Disease (AD) comprise 70% of the AD drug development pipeline of agents currently in clinical trials. Most of the target processes identified in the Common Alzheimer's Disease Research Ontology (CADRO) are represented by novel agents in trials. Inflammation and synaptic plasticity/neuroprotection are the CADRO categories with the largest number of novel candidate therapies. Within these categories, there are few overlapping targets among the test agents. Additional categories being evaluated include apolipoprotein E [Formula: see text] 4 (APOE4) effects, lipids and lipoprotein receptors, neurogenesis, oxidative stress, bioenergetics and metabolism, vascular factors, cell death, growth factors and hormones, circadian rhythm, and epigenetic regulators. We highlight current drugs being tested within these categories and their mechanisms. Trials will be informative regarding which targets can be modulated to produce a slowing of clinical decline. Possible therapeutic combinations of agents may be suggested by trial outcomes. Biomarkers are evolving in concert with new targets and novel agents, and biomarker outcomes offer a means of supporting disease modification by the putative treatment. Identification of novel targets and development of corresponding therapeutics offer an important means of advancing new treatments for AD.

Alzheimer's disease and neuroinflammation: will new drugs in clinical trials pave the way to a multi-target therapy?

Despite extensive research, no disease-modifying therapeutic option, able to prevent, cure or halt the progression of Alzheimer's disease [AD], is currently available. AD, a devastating neurodegenerative pathology leading to dementia and death, is characterized by two pathological hallmarks, the extracellular deposits of amyloid beta (Aβ) and the intraneuronal deposits of neurofibrillary tangles (NFTs) consisting of altered hyperphosphorylated tau protein. Both have been widely studied and pharmacologically targeted for many years, without significant therapeutic results. In 2022, positive data on two monoclonal antibodies targeting Aβ, donanemab and lecanemab, followed by the 2023 FDA accelerated approval of lecanemab and the publication of the final results of the phase III Clarity AD study, have strengthened the hypothesis of a causal role of Aβ in the pathogenesis of AD. However, the magnitude of the clinical effect elicited by the two drugs is limited, suggesting that additional pathological mechanisms may contribute to the disease. Cumulative studies have shown inflammation as one of the main contributors to the pathogenesis of AD, leading to the recognition of a specific role of neuroinflammation synergic with the Aβ and NFTs cascades. The present review provides an overview of the investigational drugs targeting neuroinflammation that are currently in clinical trials. Moreover, their mechanisms of action, their positioning in the pathological cascade of events that occur in the brain throughout AD disease and their potential benefit/limitation in the therapeutic strategy in AD are discussed and highlighted as well. In addition, the latest patent requests for inflammation-targeting therapeutics to be developed in AD will also be discussed.

MPC-n (IgG) improves long-term cognitive impairment in the mouse model of repetitive mild traumatic brain injury

BACKGROUND

Contact sports athletes and military personnel who suffered a repetitive mild traumatic brain injury (rmTBI) are at high risk of neurodegenerative diseases such as advanced dementia and chronic traumatic encephalopathy (CTE). However, due to the lack of specific biological indicators in clinical practice, the diagnosis and treatment of rmTBI are quite limited.

METHODS

We used 2-methacryloyloxyethyl phosphorylcholine (MPC)-nanocapsules to deliver immunoglobulins (IgG), which can increase the delivery efficiency and specific target of IgG while reducing the effective therapeutic dose of the drug.

RESULTS

Our results demonstrated that MPC-capsuled immunoglobulins (MPC-n (IgG)) significantly alleviated cognitive impairment, hippocampal atrophy, p-Tau deposition, and myelin injury in rmTBI mice compared with free IgG. Furthermore, MPC-n (IgG) can also effectively inhibit the activation of microglia and the release of inflammatory factors.

CONCLUSIONS

In the present study, we put forward an efficient strategy for the treatment of rmTBI-related cognitive impairment and provide evidence for the administration of low-dose IgG.

Inhibition of p38α MAPK restores neuronal p38γ MAPK and ameliorates synaptic degeneration in a mouse model of DLB/PD

Alterations in the p38 mitogen-activated protein kinases (MAPKs) play an important role in the pathogenesis of dementia with Lewy bodies (DLB) and Parkinson's disease (PD). Activation of the p38α MAPK isoform and mislocalization of the p38γ MAPK isoform are associated with neuroinflammation and synaptic degeneration in DLB and PD. Therefore, we hypothesized that p38α might be associated with neuronal p38γ distribution and synaptic dysfunction in these diseases. To test this hypothesis, we treated in vitro cellular and in vivo mouse models of DLB/PD with SKF-86002, a compound that attenuates inflammation by inhibiting p38α/β, and then investigated the effects of this compound on p38γ and neurodegenerative pathology. We found that inhibition of p38α reduced neuroinflammation and ameliorated synaptic, neurodegenerative, and motor behavioral deficits in transgenic mice overexpressing human α-synuclein. Moreover, treatment with SKF-86002 promoted the redistribution of p38γ to synapses and reduced the accumulation of α-synuclein in mice overexpressing human α-synuclein. Supporting the potential value of targeting p38 in DLB/PD, we found that SKF-86002 promoted the redistribution of p38γ in neurons differentiated from iPS cells derived from patients with familial PD (carrying the A53T α-synuclein mutation) and healthy controls. Treatment with SKF-86002 ameliorated α-synuclein-induced neurodegeneration in these neurons only when microglia were pretreated with this compound. However, direct treatment of neurons with SKF-86002 did not affect α-synuclein-induced neurotoxicity, suggesting that SKF-86002 treatment inhibits α-synuclein-induced neurotoxicity mediated by microglia. These findings provide a mechanistic connection between p38α and p38γ as well as a rationale for targeting this pathway in DLB/PD.

Chemical Knockdown of Phosphorylated p38 Mitogen-Activated Protein Kinase (MAPK) as a Novel Approach for the Treatment of Alzheimer's Disease

Targeted protein degradation (TPD) provides unique advantages over gene knockdown in that it can induce selective degradation of disease-associated proteins attributed to pathological mutations or aberrant post-translational modifications (PTMs). Herein, we report a protein degrader, PRZ-18002, that selectively binds to an active form of p38 MAPK. PRZ-18002 induces degradation of phosphorylated p38 MAPK (p-p38) and a phosphomimetic mutant of p38 MAPK in a proteasome-dependent manner. Given that the activation of p38 MAPK plays pivotal roles in the pathophysiology of Alzheimer's disease (AD), selective degradation of p-p38 may provide an attractive therapeutic option for the treatment of AD. In the 5xFAD transgenic mice model of AD, intranasal treatment of PRZ-18002 reduces p-p38 levels and alleviates microglia activation and amyloid beta (Aβ) deposition, leading to subsequent improvement of spatial learning and memory. Collectively, our findings suggest that PRZ-18002 ameliorates AD pathophysiology via selective degradation of p-p38, highlighting a novel therapeutic TPD modality that targets a specific PTM to induce selective degradation of neurodegenerative disease-associated protein.

Thymol improves autism-like behaviour in VPA-induced ASD rats through the Pin1/p38 MAPK pathway

Inflammation plays an essential role in the pathogenesis of autism spectrum disorder (ASD). Thymol is a bioactive monoterpene isolated from Thymus vulgaris that has anti-inflammatory properties and is helpful in neurodevelopmental disorders. The purpose of this study was to investigate the effects of thymol on autism-like behaviours in rats with VPA-induced ASD and to assess the related molecular mechanisms. In the prefrontal cortex (PFC) of the valproic acid (VPA)-exposed rat model, the levels of Pin1, phosphorylated p38 MAPK, interleukin-1β (IL-1β) and tumour necrosis factor (TNF)-α, were increased, and the levels of PSD95 and synaptophysin (SYP) decreased. After thymol treatment (30 mg/kg), the VPA-induced autism-like behaviours were alleviated. Moreover, thymol also rescued the dysregulated levels of Pin1, phosphorylated p38 MAPK, IL-1β, TNF-α, PSD95, and SYP. In addition, immunofluorescence experiments showed that thymol treatment decreased the correlation between Pin1 and phosphorylated p38 MAPK. Mechanistically, Pin1 knockdown by RNA interference confirmed that Pin1 promotes inflammation via phosphorylation of p38 MAPK in the VPA exposure rat model. In conclusion, thymol improved autism-like behaviours in VPA-induced ASD rats by reducing inflammation and improving neurodevelopment. This effect was mediated by the Pin1/p38 MAPK pathway. These results experimentally provide the potential for thymol in new therapeutic avenues for autism.

Drug Discovery and Development Targeting Dementia

Dementia, most often associated with neurodegenerative diseases, affects millions of people worldwide, predominantly the elderly. Unfortunately, no treatment is still available. Therefore, there is an urgent need to address this situation. This review presents the state of the art of drug discovery and developments in targeting dementia. Several approaches are discussed, such as drug repurposing, the use of small molecules, and phosphodiesterase inhibitors. Furthermore, the review also provides insights into clinical trials of these molecules. Emphasis has been placed on small molecules and multi-target-directed ligands, as well as disease-modifying therapies. Finally, attention is drawn to the possibilities of applications of nanotechnology in managing dementia.

Synaptic degeneration in Alzheimer disease

Alzheimer disease (AD) is characterized by progressive cognitive decline in older individuals accompanied by the presence of two pathological protein aggregates - amyloid-β and phosphorylated tau - in the brain. The disease results in brain atrophy caused by neuronal loss and synapse degeneration. Synaptic loss strongly correlates with cognitive decline in both humans and animal models of AD. Indeed, evidence suggests that soluble forms of amyloid-β and tau can cause synaptotoxicity and spread through neural circuits. These pathological changes are accompanied by an altered phenotype in the glial cells of the brain - one hypothesis is that glia excessively ingest synapses and modulate the trans-synaptic spread of pathology. To date, effective therapies for the treatment or prevention of AD are lacking, but understanding how synaptic degeneration occurs will be essential for the development of new interventions. Here, we highlight the mechanisms through which synapses degenerate in the AD brain, and discuss key questions that still need to be answered. We also cover the ways in which our understanding of the mechanisms of synaptic degeneration is leading to new therapeutic approaches for AD.

Calcium-dependent cytosolic phospholipase A2 activation is implicated in neuroinflammation and oxidative stress associated with ApoE4

BACKGROUND

Apolipoprotein E4 (APOE4) is associated with a greater response to neuroinflammation and the risk of developing late-onset Alzheimer's disease (AD), but the mechanisms for this association are not clear. The activation of calcium-dependent cytosolic phospholipase A2 (cPLA2) is involved in inflammatory signaling and is elevated within the plaques of AD brains. The relation between APOE4 genotype and cPLA2 activity is not known.

METHODS

Mouse primary astrocytes, mouse and human brain samples differing by APOE genotypes were collected for measuring cPLA2 expression, phosphorylation, and activity in relation to measures of inflammation and oxidative stress.

RESULTS

Greater cPLA2 phosphorylation, cPLA2 activity and leukotriene B4 (LTB4) levels were identified in ApoE4 compared to ApoE3 in primary astrocytes, brains of ApoE-targeted replacement (ApoE-TR) mice, and in human brain homogenates from the inferior frontal cortex of persons with AD dementia carrying APOE3/4 compared to APOE3/3. Higher phosphorylated p38 MAPK but not ERK1/2 was found in ApoE4 primary astrocytes and mouse brains than that in ApoE3. Greater cPLA2 translocation to cytosol was observed in human postmortem frontal cortical synaptosomes with recombinant ApoE4 than ApoE3 ex vivo. In ApoE4 astrocytes, the greater levels of LTB4, reactive oxygen species (ROS), and inducible nitric oxide synthase (iNOS) were reduced after cPLA2 inhibition.

CONCLUSIONS

Our findings implicate greater activation of cPLA2 signaling system with APOE4, which could represent a potential drug target for mitigating the increased neuroinflammation with APOE4 and AD.

Disease-Modifying Therapies for Alzheimer's Disease: More Questions than Answers

Scientific advances over the last four decades have steadily infused the Alzheimer's disease (AD) field with great optimism that therapies targeting Aβ, amyloid, tau, and innate immune activation states in the brain would provide disease modification. Unfortunately, this optimistic scenario has not yet played out. Though a recent approval of the anti-Aβ aggregate binding antibody, Aduhelm (aducanumab), as a "disease-modifying therapy for AD" is viewed by some as a breakthrough, many remain unconvinced by the data underlying this approval. Collectively, we have not succeeded in changing AD from a largely untreatable, inevitable, and incurable disease to a treatable, preventable, and curable one. Here, I will review the major foci of the AD "disease-modifying" therapeutic pipeline and some of the "open questions" that remain in terms of these therapeutic approaches. I will conclude the review by discussing how we, as a field, might adjust our approach, learning from our past failures to ensure future success.

Recent advances in molecular pathways and therapeutic implications targeting neuroinflammation for Alzheimer's disease

Alzheimer's disease (AD) is a major contributor of dementia leading to the degeneration of neurons in the brain with major symptoms like loss of memory and learning. Many evidences suggest the involvement of neuroinflammation in the pathology of AD. Cytokines including TNF-α and IL-6 are also found increasing the BACE1 activity and expression of NFκB resulting in generation of Aβ in AD brain. Following the interaction of Aβ with microglia and astrocytes, other inflammatory molecules also get translocated to the site of inflammation by chemotaxis and exaggerate neuroinflammation. Various pathways like NFκB, p38 MAPK, Akt/mTOR, caspase, nitric oxide and COX trigger microglia to release inflammatory cytokines. PPARγ agonists like pioglitazone increases the phagocytosis of Aβ and reduces inflammatory cytokine IL-1β. Celecoxib and roficoxib like selective COX-2 inhibitors also ameliorate neuroinflammation. Non-selective COX inhibitor indomethacin is also potent inhibitor of inflammatory mediators released from microglia. Mitophagy process is considered quite helpful in reducing inflammation due to microglia as it promotes the phagocytosis of over activated microglial cells and other inflammatory cells. Mitophagy induction is also beneficial in the removal of damaged mitochondria and reduction of infiltration of inflammatory molecules at the site of accumulation of the damaged mitochondria. Targeting these pathways and eventually ameliorating the activation of microglia can mitigate neuroinflammation and come out as a better therapeutic option for the treatment of Alzheimer's disease.

Current Insights of Inhibitors of p38 Mitogen-Activated Protein Kinase in Inflammation

BACKGROUND

The inflammatory process is one of the mechanisms by which our body upholds us from pathogens such as parasites, bacteria, viruses, and other harmful microorganisms. Inflammatory stimuli activate many intracellular signaling pathways such as the nuclear factor-kB (NF-kB) pathway and three mitogen-activated protein kinase (MAPK) pathways, which are mediated through extracellular-signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38. The p38 has evolved as an enticing target in treating many persistent inflammatory diseases. Hence, designing novel p38 inhibitors targeting MAPK pathways has acquired significance.

OBJECTIVE

Peruse to identify the lead target to discover novel p38MAPK inhibitors with different scaffolds having improved selectivity over the prototype drugs.

METHODS

Structure and the binding sites of p38MAPK were focused. Various scaffolds designed for inhibition and the molecules which have entered the clinical trials are discussed.

RESULTS

This review aspires to present the available information on the structure and the 3D binding sites of p38MAPK, various scaffolds designed for imidazole, urea, benzamide, azoles, quinoxaline, chromone, ketone as a potent p38MAPK inhibitors and their SAR studies and the molecules which have entered the clinical trials.

CONCLUSION

The development of successful selective p38MAPK inhibitors in inflammatory diseases is in progress despite all challenges. It was speculated that p38MAPK also plays an important role in treating diseases such as neuroinflammation, arterial inflammation, vascular inflammation, cancer and so on, which are posing the world with treatment challenges. In this review, clinical trials of drugs are discussed related to inflammatory and its related diseases. Research is in progress to design and develop novel p38MAPK inhibitors with minimal side effects.

Differential Effects of Toll-Like Receptor Activation and Differential Mediation by MAP Kinases of Immune Responses in Microglial Cells

Microglial activation is believed to play a role in many psychiatric and neurodegenerative diseases. Based largely on evidence from other cell types, it is widely thought that MAP kinase (ERK, JNK and p38) signalling pathways contribute strongly to microglial activation following immune stimuli acting on toll-like receptor (TLR) 3 or TLR4. We report here that exposure of SimA9 mouse microglial cell line to immune mimetics stimulating TLR4 (lipopolysaccharide-LPS) or TLR7/8 (resiquimod/R848), results in marked MAP kinase activation, followed by induction of nitric oxide synthase, and various cytokines/chemokines. However, in contrast to TLR4 or TLR7/8 stimulation, very few effects of TLR3 stimulation by poly-inosine/cytidine (polyI:C) were detected. Induction of chemokines/cytokines at the mRNA level by LPS and resiquimod were, in general, only marginally affected by MAP kinase inhibition, and expression of TNF, Ccl2 and Ccl5 mRNAs, along with nitrite production, were enhanced by p38 inhibition in a stimulus-specific manner. Selective JNK inhibition enhanced Ccl2 and Ccl5 release. Many distinct responses to stimulation of TLR4 and TLR7 were observed, with JNK mediating TNF protein induction by the latter but not the former, and suppressing Ccl5 release by the former but not the latter. These data reveal complex modulation by MAP kinases of microglial responses to immune challenge, including a dampening of some responses. They demonstrate that abnormal levels of JNK or p38 signalling in microglial cells will perturb their profile of cytokine and chemokine release, potentially contributing to abnormal inflammatory patterns in CNS disease states.

Therapy for Alzheimer's disease: Missing targets and functional markers?

The development of the next generation therapy for Alzheimer's disease (AD) presents a huge challenge given the number of promising treatment candidates that failed in trials, despite recent advancements in understanding of genetic, pathophysiologic and clinical characteristics of the disease. This review reflects some of the most current concepts and controversies in developing disease-modifying and new symptomatic treatments. It elaborates on recent changes in the AD research strategy for broadening drug targets, and potentials of emerging non-pharmacological treatment interventions. Established and novel biomarkers are discussed, including emerging cerebrospinal fluid and plasma biomarkers reflecting tau pathology, neuroinflammation and neurodegeneration. These fluid biomarkers together with neuroimaging findings can provide innovative objective assessments of subtle changes in brain reflecting disease progression. A particular emphasis is given to neurophysiological biomarkers which are well-suited for evaluating the brain overall neural network integrity and function. Combination of multiple biomarkers, including target engagement and outcome biomarkers will empower translational studies and facilitate successful development of effective therapies.

Learning from the Past: A Review of Clinical Trials Targeting Amyloid, Tau and Neuroinflammation in Alzheimer's Disease

Alzheimer's Disease (AD) is the most common neurodegenerative disease and cause of dementia. Characterized by amyloid plaques and neurofibrillary tangles of hyperphosphorylated Tau, AD pathology has been intensively studied during the last century. After a long series of failed trials of drugs targeting amyloid or Tau deposits, currently, hope lies in the positive results of one Phase III trial, highly debated, and on other ongoing trials. In parallel, some approaches target neuroinflammation, another central feature of AD. Therapeutic strategies are initially evaluated on animal models, in which the various drugs have shown effects on the target (decreasing amyloid, Tau and neuroinflammation) and sometimes on cognitive impairment. However, it is important to keep in mind that rodent models have a less complex brain than humans and that the pathology is generally not fully represented. Although they are indispensable tools in the drug discovery process, results obtained from animal models must be viewed with caution. In this review, we focus on the current status of disease-modifying therapies targeting amyloid, Tau and neuroinflammation with particular attention on the discrepancy between positive preclinical results on animal models and failures in clinical trials.

A phase 2 double-blind placebo-controlled 24-week treatment clinical study of the p38 alpha kinase inhibitor neflamapimod in mild Alzheimer's disease

BACKGROUND

In preclinical studies, p38⍺ kinase is implicated in Alzheimer's disease (AD) pathogenesis. In animal models, it mediates impaired synaptic dysfunction in the hippocampus, causing memory deficits, and is involved in amyloid-beta (Aβ) production and tau pathology.

METHODS

The REVERSE-SD (synaptic dysfunction) study was a multi-center phase 2, randomized, double-blind, placebo-controlled trial of the p38⍺ kinase inhibitor neflamapimod; conducted December 29, 2017, to June 17, 2019; 464 participants screened, and 161 randomized to either 40 mg neflamapimod (78 study participants) or matching placebo (83 study participants), orally twice daily for 24 weeks. Study participants are as follows: CSF AD-biomarker confirmed, Clinical Dementia Rating (CDR)-global score 0.5 or 1.0, CDR-memory score ≥0.5, and Mini-Mental State Examination (MMSE) 20-28. The primary endpoint was the improvement in episodic memory, assessed by combined change in Z-scores of Hopkins Verbal Learning Test-Revised (HVLT-R) Total and Delayed Recall. Secondary endpoints included change in Wechsler Memory Scale-IV (WMS) Immediate and Delayed Recall composites, CDR-SB, MMSE, and CSF biomarkers [total and phosphorylated tau (T-tau and p-tau₁₈₁), Aβ_1-40, Aβ_1-42, neurogranin, and neurofilament light chain].

RESULTS

At randomization, the mean age is 72, 50% female, 77% with CDR-global score 0.5, and mean MMSE score 23.8. The incidence of discontinuation for adverse events and serious adverse events (all considered unrelated) was 3% each. No significant differences between treatment groups were observed in the primary or secondary clinical endpoints. Significantly reduced CSF levels with neflamapimod treatment, relative to placebo, were evident for T-tau [difference (95% CI): -18.8 (-35.8, -1.8); P=0.031] and p-tau₁₈₁ [-2.0 (-3.6, -0.5); P=0.012], with a trend for neurogranin [-21.0 (-43.6, 1.6); P=0.068]. In pre-specified pharmacokinetic-pharmacodynamic (PK-PD) analyses, subjects in the highest quartile of trough plasma neflamapimod levels demonstrated positive trends, compared with placebo, in HLVT-R and WMS.

CONCLUSIONS AND RELEVANCE

A 24-week treatment with 40 mg neflamapimod twice daily did not improve episodic memory in patients with mild AD. However, neflamapimod treatment lowered CSF biomarkers of synaptic dysfunction. Combined with PK-PD findings, the results indicate that a longer duration study of neflamapimod at a higher dose level to assess effects on AD progression is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03402659 . Registered on January 18, 2018.

Calcium-dependent cytosolic phospholipase A2 activation is implicated in neuroinflammation and oxidative stress associated with ApoE4

BACKGROUND

Apolipoprotein E4 (APOE4) is associated with a greater response to neuroinflammation and the risk of developing late-onset Alzheimer's disease (AD), but the mechanisms for this association are not clear. The activation of calcium-dependent cytosolic phospholipase A2 (cPLA2) is involved in inflammatory signaling and is elevated within the plaques of AD brains. The relation between APOE4 genotype and cPLA2 activity is not known.

METHODS

Mouse primary astrocytes, mouse and human brain samples differing by APOE genotypes were collected for measuring cPLA2 expression, phosphorylation, and activity in relation to measures of inflammation and oxidative stress.

RESULTS

Greater cPLA2 phosphorylation, cPLA2 activity and leukotriene B4 (LTB4) levels were identified in ApoE4 compared to ApoE3 in primary astrocytes, brains of ApoE-targeted replacement (ApoE-TR) mice, and in human brain homogenates from the inferior frontal cortex of patients with AD carrying APOE3/E4 compared to APOE3/E3. Greater cPLA2 phosphorylation was also observed in human postmortem frontal cortical synaptosomes and primary astrocytes after treatment with recombinant ApoE4 ex vivo. In ApoE4 astrocytes, the greater levels of LTB4, reactive oxygen species (ROS), and inducible nitric oxide synthase (iNOS) were reduced after cPLA2 inhibition.

CONCLUSIONS

Our findings implicate greater activation of cPLA2 signaling system with APOE4, which could represent a potential drug target for mitigating the increased neuroinflammation with APOE4 and AD.

Experimental Disease-Modifying Agents for Frontotemporal Lobar Degeneration

Frontotemporal dementia is a clinically, genetically and pathologically heterogeneous neurodegenerative disorder, enclosing a wide range of different pathological entities, associated with the accumulation of proteins such as tau and TPD-43. Characterized by a high hereditability, mutations in three main genes, MAPT, GRN and C9orf72, can drive the neurodegenerative process. The connection between different genes and proteinopathies through specific mechanisms has shed light on the pathophysiology of the disease, leading to the identification of potential pharmacological targets. New experimental strategies are emerging, in both preclinical and clinical settings, which focus on small molecules rather than gene therapy. In this review, we provide an insight into the aberrant mechanisms leading to FTLD-related proteinopathies and discuss recent therapies with the potential to ameliorate neurodegeneration and disease progression.

A nuclear factor-kappa B inhibiting peptide suppresses innate immune receptors and gliosis in a transgenic mouse model of Alzheimer's disease

A disproportionate increase in activated nuclear factor-kappa B (NF-κB) has been shown to drive the Aβ deposition, neuroinflammation and neurodegeneration in Alzheimer's disease (AD). Hence, selective targeting of activated p65 represents an attractive therapeutic approach for AD. Glucocorticoid induced leucine zipper (GILZ) is a NF-κB interactant that binds and sequesters the activated p65 in the cytoplasm. The p65 binding domain of GILZ adopts a polyproline type II helical conformation, a motif that acts as an adaptable glove in the interface with the binding partner and constitutes an excellent template for drug design. Previously, peptide analogs of the p65 binding domain of GILZ, referred to as GA have been shown to suppress pathology in the lipopolysaccharide induced model of neuroinflammation. In this study, we investigated the CNS delivery of labeled GA administered intraperitoneally in adult mice for a period of upto 24 h. Further, we evaluated the suppressive potential of GA in 5xFAD mice, an aggressive model with five genetic mutations closely associated with human AD. Groups of 5xFAD mice administered GA or control peptide intraperitoneally on alternate days for six weeks were evaluated for Aβ deposition, microglia, inflammation and innate immune responses by immunohistochemistry and real time polymerase reaction. GA was observed in proximity with NeuN positive neurons suggesting that the compound crossed the blood brain barrier to reach the brain parenchyma. Further, GA treatment decreased Aβ load, reduced Iba1 + microglia and glial fibrillary acidic protein (GFAP)+ astrocytes, inhibited inflammatory cytokines and suppressed toll like receptor (TLR-2, TLR-4) expressions in 5xFAD mice.

The PKR/P38/RIPK1 Signaling Pathway as a Therapeutic Target in Alzheimer's Disease

Neuropathological lesions in Alzheimer’s disease (AD) include amyloid plaques formed by the accumulation of amyloid peptides, neurofibrillary tangles made of hyperphosphorylated tau protein, synaptic and neuronal degenerations, and neuroinflammation. The cause of AD is unknown, but according to the amyloid hypothesis, amyloid oligomers could lead to the activation of kinases such as eukaryotic translation initiation factor 2-alpha kinase 2 (PKR), p38, and receptor-interacting serine/threonine-protein kinase 1 (RIPK1), which all belong to the same stress-activated pathway. Many toxic kinase activations have been described in AD patients and in experimental models. A p38 mitogen-activated protein kinase inhibitor was recently tested in clinical trials but with unsuccessful results. The complex PKR/P38/RIPK1 (PKR/dual specificity mitogen-activated protein kinase kinase 6 (MKK6)/P38/MAP kinase-activated protein kinase 2 (MK2)/RIPK1) is highly activated in AD brains and in the brains of AD transgenic animals. To delineate the implication of this pathway in AD, we carried out a search on PubMed including PKR/MKK6/p38/MK2/RIPK1, Alzheimer, and therapeutics. The involvement of this signaling pathway in the genesis of AD lesions, including Aβ accumulations and tau phosphorylation as well as cognitive decline, is demonstrated by the reports described in this review. A future combination strategy with kinase inhibitors should be envisaged to modulate the consequences for neurons and other brain cells linked to the abnormal activation of this pathway.

Pseudomonas aeruginosa induces p38MAP kinase-dependent IL-6 and CXCL8 release from bronchial epithelial cells via a Syk kinase pathway

Pseudomonas aeruginosa (Pa) infection is a major cause of airway inflammation in immunocompromised and cystic fibrosis (CF) patients. Mitogen-activated protein (MAP) and tyrosine kinases are integral to inflammatory responses and are therefore potential targets for novel anti-inflammatory therapies. We have determined the involvement of specific kinases in Pa-induced inflammation. The effects of kinase inhibitors against p38MAPK, MEK 1/2, JNK 1/2, Syk or c-Src, a combination of a p38MAPK with Syk inhibitor, or a novel narrow spectrum kinase inhibitor (NSKI), were evaluated against the release of the proinflammatory cytokine/chemokine, IL-6 and CXCL8 from BEAS-2B and CFBE41o- epithelial cells by Pa. Effects of a Syk inhibitor against phosphorylation of the MAPKs were also evaluated. IL-6 and CXCL8 release by Pa were significantly inhibited by p38MAPK and Syk inhibitors (p<0.05). Phosphorylation of HSP27, but not ERK or JNK, was significantly inhibited by Syk kinase inhibition. A combination of p38MAPK and Syk inhibitors showed synergy against IL-6 and CXCL8 induction and an NSKI completely inhibited IL-6 and CXCL8 at low concentrations. Pa-induced inflammation is dependent on p38MAPK primarily, and Syk partially, which is upstream of p38MAPK. The NSKI suggests that inhibiting specific combinations of kinases is a potent potential therapy for Pa-induced inflammation.

Diversity and versatility of p38 kinase signalling in health and disease

The ability of cells to deal with different types of stressful situations in a precise and coordinated manner is key for survival and involves various signalling networks. Over the past 25 years, p38 kinases — in particular, p38α — have been implicated in the cellular response to stress at many levels. These span from environmental and intracellular stresses, such as hyperosmolarity, oxidative stress or DNA damage, to physiological situations that involve important cellular changes such as differentiation. Given that p38α controls a plethora of functions, dysregulation of this pathway has been linked to diseases such as inflammation, immune disorders or cancer, suggesting the possibility that targeting p38α could be of therapeutic interest. In this Review, we discuss the organization of this signalling pathway focusing on the diversity of p38α substrates, their mechanisms and their links to particular cellular functions. We then address how the different cellular responses can be generated depending on the signal received and the cell type, and highlight the roles of this kinase in human physiology and in pathological contexts.

p38α — the best-characterized member of the p38 kinase family — is a key mediator of cellular stress responses. p38α is activated by a plethora of signals and functions through a multitude of substrates to regulate different cellular behaviours. Understanding context-dependent p38α signalling provides important insights into p38α roles in physiology and pathology.

Modulation of Brain Hyperexcitability: Potential New Therapeutic Approaches in Alzheimer's Disease

People with Alzheimer's disease (AD) have significantly higher rates of subclinical and overt epileptiform activity. In animal models, oligomeric Aβ amyloid is able to induce neuronal hyperexcitability even in the early phases of the disease. Such aberrant activity subsequently leads to downstream accumulation of toxic proteins, and ultimately to further neurodegeneration and neuronal silencing mediated by concomitant tau accumulation. Several neurotransmitters participate in the initial hyperexcitable state, with increased synaptic glutamatergic tone and decreased GABAergic inhibition. These changes appear to activate excitotoxic pathways and, ultimately, cause reduced long-term potentiation, increased long-term depression, and increased GABAergic inhibitory remodelling at the network level. Brain hyperexcitability has therefore been identified as a potential target for therapeutic interventions aimed at enhancing cognition, and, possibly, disease modification in the longer term. Clinical trials are ongoing to evaluate the potential efficacy in targeting hyperexcitability in AD, with levetiracetam showing some encouraging effects. Newer compounds and techniques, such as gene editing via viral vectors or brain stimulation, also show promise. Diagnostic challenges include identifying best biomarkers for measuring sub-clinical epileptiform discharges. Determining the timing of any intervention is critical and future trials will need to carefully stratify participants with respect to the phase of disease pathology.

Continuous administration of a p38α inhibitor during the subacute phase after transient ischemia-induced stroke in the rat promotes dose-dependent functional recovery accompanied by increase in brain BDNF protein level

There is unmet need for effective stroke therapies. Numerous neuroprotection attempts for acute cerebral ischemia have failed and as a result there is growing interest in developing therapies to promote functional recovery through increasing synaptic plasticity. For this research study, we hypothesized that in addition to its previously reported role in mediating cell death during the acute phase, the alpha isoform of p38 mitogen-activated protein kinase, p38α, may also contribute to interleukin-1β-mediated impairment of functional recovery during the subacute phase after acute ischemic stroke. Accordingly, an oral, brain-penetrant, small molecule p38α inhibitor, neflamapimod, was evaluated as a subacute phase stroke treatment to promote functional recovery. Neflamapimod administration to rats after transient middle cerebral artery occlusion at two dose levels was initiated outside of the previously characterized therapeutic window for neuroprotection of less than 24 hours for p38α inhibitors. Six-week administration of neflamapimod, starting at 48 hours after reperfusion, significantly improved behavioral outcomes assessed by the modified neurological severity score at Week 4 and at Week 6 post stroke in a dose-dependent manner. Neflamapimod demonstrated beneficial effects on additional measures of sensory and motor function. It also resulted in a dose-related increase in brain-derived neurotrophic factor (BDNF) protein levels, a previously reported potential marker of synaptic plasticity that was measured in brain homogenates at sacrifice. Taken together with literature evidence on the role of p38α-dependent suppression by interleukin-1β of BDNF-mediated synaptic plasticity and BDNF production, our findings support a mechanistic model in which inhibition of p38α promotes functional recovery after ischemic stroke by blocking the deleterious effects of interleukin-1β on synaptic plasticity. The dose-related in vivo efficacy of neflamapimod offers the possibility of having a therapy for stroke that could be initiated outside the short time window for neuroprotection and for improving recovery after a completed stroke.

Pharmacological management of dementia with Lewy bodies with a focus on zonisamide for treating parkinsonism

INTRODUCTION

Dementia with Lewy bodies (DLB) has no approved symptomatic or disease-modifying treatments in the US and Europe, despite being the second most common cause of neurodegenerative dementia.

AREAS COVERED

Herein, the authors briefly review the DLB drug development pipeline, providing a summary of the current pharmacological intervention studies. They then focus on the anticonvulsant zonisamide, a benzisoxazole derivative with a sulfonamide group and look at its value for treating parkinsonism in DLB.

EXPERT OPINION

Several new compounds are being tested in DLB, the most innovative being those aimed at decreasing brain accumulation of α-synuclein. Unfortunately, new drug testing is challenging in terms of consistent diagnostic criteria and lack of reliable biomarkers. Few randomized controlled trials (RCTs) are well-designed, with enough power to detect significant drug effects. Levodopa monotherapy can treat the parkinsonism in DLB, but it can cause agitation or visual hallucination worsening. Two Phase II/III RCTs of DLB patients recently reported a statistically significant improvement in motor function in those receiving zonisamide as an adjunctive treatment to levodopa. New biomarker strategies and validated outcome measures for DLB or prodromal DLB may enhance clinical trial design for the development of specific disease-modifying treatments.

Neuronal deficiency of p38α-MAPK ameliorates symptoms and pathology of APP or Tau-transgenic Alzheimer's mouse models

Alzheimer's disease (AD) is the leading cause of dementia with very limited therapeutic options. Amyloid β (Aβ) and phosphorylated Tau (p-Tau) are key pathogenic molecules in AD. P38α-MAPK is specifically activated in AD lesion sites. However, its effects on AD pathogenesis, especially on p-Tau-associated brain pathology, and the underlying molecular mechanisms remain unclear. We mated human APP-transgenic mice and human P301S Tau-transgenic mice with mapk14-floxed and neuron-specific Cre-knock-in mice. We observed that deletion of p38α-MAPK specifically in neurons improves the cognitive function of both 9-month-old APP and Tau-transgenic AD mice, which is associated with decreased Aβ and p-Tau load in the brain. We further used next-generation sequencing to analyze the gene transcription in brains of p38α-MAPK deficient and wild-type APP-transgenic mice, which indicated that deletion of p38α-MAPK regulates the transcription of calcium homeostasis-related genes, especially downregulates the expression of grin2a, a gene encoding NMDAR subunit NR2A. Cell culture experiments further verified that deletion of p38α-MAPK inhibits NMDA-triggered calcium influx and neuronal apoptosis. Our systemic studies of AD pathogenic mechanisms using both APP- and Tau-transgenic mice suggested that deletion of neuronal p38α-MAPK attenuates AD-associated brain pathology and protects neurons in AD pathogenesis. This study supports p38α-MAPK as a novel target for AD therapy.

A selective p38α/β MAPK inhibitor alleviates neuropathology and cognitive impairment, and modulates microglia function in 5XFAD mouse

Background

Chronic neuroinflammation, aggressive amyloid beta (Aβ) deposition, neuronal cell loss, and cognitive impairment are pathological presentations of Alzheimer’s disease (AD). Therefore, resolution of neuroinflammation and inhibition of Aβ-driven pathology have been suggested to be important strategies for AD therapy. Previous efforts to prevent AD progression have identified p38 mitogen-activated protein kinases (MAPKs) as a promising target for AD therapy. Recent studies showed pharmacological inhibition of p38α MAPK improved memory impairment in AD mouse models.

Methods

In this study, we used an AD mouse model, 5XFAD, to explore the therapeutic potential of NJK14047 which is a novel, selective p38α/β MAPK inhibitor. The mice were injected with 2.5 mg/kg NJK14047 or vehicle every other day for 3 months. Morris water maze task and histological imaging analysis were performed. Protein and mRNA expression levels were measured using immunoblotting and qRT-PCR, respectively. In vitro studies were conducted to measure the cytotoxicity of microglia- and astrocyte-conditioned medium on primary neurons using the MTT assay and TUNEL assay.

Results

NJK14047 treatment downregulated phospho-p38 MAPK levels, decreased the amount of Aβ deposits, and reduced spatial learning memory loss in 9-month-old 5XFAD mice. While the pro-inflammatory conditions were decreased, the expression of alternatively activated microglial markers and microglial phagocytic receptors was increased. Furthermore, NJK14047 treatment reduced the number of degenerating neurons labeled with Fluoro-Jade B in the brains of 5XFAD mice. The neuroprotective effect of NJK14047 was further confirmed by in vitro studies.

Conclusion

Taken together, a selective p38α/β MAPK inhibitor NJK14047 successfully showed therapeutic effects for AD in 5XFAD mice. Based on our data, p38 MAPK inhibition is a potential strategy for AD therapy, suggesting NJK14047 as one of the promising candidates for AD therapeutics targeting p38 MAPKs.

Amyloid-β-independent regulators of tau pathology in Alzheimer disease

The global epidemic of Alzheimer disease (AD) is worsening, and no approved treatment can revert or arrest progression of this disease. AD pathology is characterized by the accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles in the brain. Genetic data, as well as autopsy and neuroimaging studies in patients with AD, indicate that Aβ plaque deposition precedes cortical tau pathology. Because Aβ accumulation has been considered the initial insult that drives both the accumulation of tau pathology and tau-mediated neurodegeneration in AD, the development of AD therapeutics has focused mostly on removing Aβ from the brain. However, striking preclinical evidence from AD mouse models and patient-derived human induced pluripotent stem cell models indicates that tau pathology can progress independently of Aβ accumulation and arises downstream of genetic risk factors for AD and aberrant metabolic pathways. This Review outlines novel insights from preclinical research that implicate apolipoprotein E, the endocytic system, cholesterol metabolism and microglial activation as Aβ-independent regulators of tau pathology. These factors are discussed in the context of emerging findings from clinical pathology, functional neuroimaging and other approaches in humans. Finally, we discuss the implications of these new insights for current Aβ-targeted strategies and highlight the emergence of novel therapeutic strategies that target processes upstream of both Aβ and tau.

Clinical drug development for dementia with Lewy bodies: past and present

Introduction: Dementia with Lewy bodies (DLB) is an under-researched area despite being the second most common type of degenerative dementia after Alzheimer's disease. It is an area of unmet need with no approved symptomatic or disease-modifying therapies. The pharmacological management of DLB is complex and challenging because early trials of drugs for DLB have resulted in no demonstrable efficacy. Randomized controlled trials (RCTs) in the DLB population have only recently been initiated. Understanding results from previous and current clinical trials in DLB can provide insights for future research and development.Areas covered: We provide an overview of the DLB drug development landscape and the current treatment strategies. We reviewed ClinicalTrials.gov to identify all clinical trials for the treatment of DLB.Expert opinion: DLB drug development has significantly improved in recent years with eight agents now in clinical trials. However, more rigorous RCTs are urgently needed. Diagnostic criteria must be optimized to accurately diagnose patients for clinical trials and care. New biomarker strategies are necessary to improve diagnostic capabilities and trial designs, and novel drug targets should be identified to develop DLB specific disease-modifying therapies. Evaluating the current drug development landscape can provide insight into how best to optimize development practices.

Prion neurotoxicity

Although the mechanisms underlying prion propagation and infectivity are now well established, the processes accounting for prion toxicity and pathogenesis have remained mysterious. These processes are of enormous clinical relevance as they hold the key to identification of new molecular targets for therapeutic intervention. In this review, we will discuss two broad areas of investigation relevant to understanding prion neurotoxicity. The first is the use of in vitro experimental systems that model key events in prion pathogenesis. In this context, we will describe a hippocampal neuronal culture system we developed that reproduces the earliest pathological alterations in synaptic morphology and function in response to PrP^Sc . This system has allowed us to define a core synaptotoxic signaling pathway involving the activation of NMDA and AMPA receptors, stimulation of p38 MAPK phosphorylation and collapse of the actin cytoskeleton in dendritic spines. The second area concerns a striking and unexpected phenomenon in which certain structural manipulations of the PrP^C molecule itself, including introduction of N-terminal deletion mutations or binding of antibodies to C-terminal epitopes, unleash powerful toxic effects in cultured cells and transgenic mice. We will describe our studies of this phenomenon, which led to the recognition that it is related to the induction of large, abnormal ionic currents by the structurally altered PrP molecules. Our results suggest a model in which the flexible N-terminal domain of PrP^C serves as a toxic effector which is regulated by intramolecular interactions with the globular C-terminal domain. Taken together, these two areas of study have provided important clues to underlying cellular and molecular mechanisms of prion neurotoxicity. Nevertheless, much remains to be done on this next frontier of prion science.

Dephosphorylated rather than hyperphosphorylated Tau triggers a pro-inflammatory profile in microglia through the p38 MAPK pathway

Tauopathies are a broad set of neurodegenerative dementias characterized by the aggregation of Tau protein. Activated microglia and elevated levels of pro-inflammatory molecules are also pathological hallmarks of tauopathies. In these diseases, intracellular Tau is secreted to the extracellular space, where it interacts with other cells, such as neurons and glia, promoting inflammation. However, the mechanism through which extracellular Tau triggers pro-inflammatory responses in microglia remains unknown. Primary microglia cultures were treated with extracellular Tau in its hyperphosphorylated, dephosphorylated or non-phosphorylated form. Protein cytokine arrays, real-time PCR, inhibition of the p38 MAPK pathway, phosphatase assays, and quantification of proteins through immunoblotting were used to analyze the effect of extracellular Tau on the pro-inflammatory response of microglia. The main finding of this work is that extracellular non-phosphorylated and dephosphorylated forms of Tau, rather than hyperphosphorylated Tau, activate the p38 MAPK pathway in microglia, thus triggering a pro-inflammatory response in these cells.