Randomized, Double-Blind, Placebo-Controlled Study of Encenicline, an α7 Nicotinic Acetylcholine Receptor Agonist, as a Treatment for Cognitive Impairment in Schizophrenia

Advancements in Non-Dopaminergic Treatments for Schizophrenia: A Systematic Review of Pipeline Developments

INTRODUCTION

Conventional antipsychotic drugs that attenuate dopaminergic neural transmission are ineffective in approximately one-third of patients with schizophrenia. This necessitates the development of non-dopaminergic agents.

METHODS

A systematic search was conducted for completed phase II and III trials of compounds for schizophrenia treatment using the US Clinical Trials Registry and the EU Clinical Trials Register. Compounds demonstrating significant superiority over placebo in the primary outcome measure in the latest phase II and III trials were identified. Collateral information on the included compounds was gathered through manual searches in PubMed and press releases.

RESULTS

Sixteen compounds were identified; four compounds (ulotaront, xanomeline/trospium chloride, vabicaserin, and roluperidone) were investigated as monotherapy and the remaining 12 (pimavanserin, bitopertin, BI 425809, encenicline, tropisetron, pregnenolone, D-serine, estradiol, tolcapone, valacyclovir, cannabidiol, and rimonabant) were examined as add-on therapy. Compared to the placebo, ulotaront, xanomeline/trospium chloride, vabicaserin, bitopertin, estradiol, cannabidiol, rimonabant, and D-serine showed efficacy for positive symptoms; roluperidone and pimavanserin were effective for negative symptoms; and encenicline, tropisetron, pregnenolone, tolcapone, BI 425809, and valacyclovir improved cognitive function.

DISCUSSION

Compounds that function differently from existing antipsychotics may offer novel symptom-specific therapeutic strategies for patients with schizophrenia.

Development and Evaluation of a Cognitive Battery for People With Schizophrenia in Ethiopia

BACKGROUND AND HYPOTHESIS

Cognitive difficulties significantly burdened people with schizophrenia (PWS). However, cognitive assessment is often unavailable in low- and middle-income counties (LMICs) due to a lack of validated and culturally adapted cognitive assessment tools. In this study, we developed and evaluated a culturally sensitive cognitive battery for PWS in Ethiopia.

STUDY DESIGN

This study was conducted in three phases. First, we selected appropriate tests through an instrument selection procedure and created a new battery. Then, we rigorously adapted the tests using culturally competent procedures, including cognitive interviewing and expert meetings. Finally, we tested the new battery in 208 PWS and 208 controls. We evaluated its psychometric properties using advanced statistical techniques, including Item Response Theory (IRT).

STUDY RESULTS

The Ethiopian Cognitive Assessment battery for Schizophrenia (ECAS) was developed from three different batteries. Participants reported tests were easy to complete, and the raters found them easy to administer. All tests had good inter-rater reliability, and the composite score had very high test-retest reliability (ICC = 0.91). One-factor structure better represented the data with excellent internal consistency (α = .81). ECAS significantly differentiated PWS from controls with 77% sensitivity and 62% specificity at a Z-score ≤0.12 cut-off value. IRT analysis suggested that the battery functions best among moderately impaired participants (difficulty between -0.06 and 0.66).

CONCLUSIONS

ECAS is a practical, tolerable, reliable, and valid assessment of cognition. ECAS can supplement current assessment tools in LAMICs for PWS and can be used to measure cognitive intervention outcomes.

A computational account of the development and evolution of psychotic symptoms

The mechanisms of psychotic symptoms like hallucinations and delusions are often investigated in fully-formed illness, well after symptoms emerge. These investigations have yielded key insights, but are not well-positioned to reveal the dynamic forces underlying symptom formation itself. Understanding symptom development over time would allow us to identify steps in the pathophysiological process leading to psychosis, shifting the focus of psychiatric intervention from symptom alleviation to prevention. We propose a model for understanding the emergence of psychotic symptoms within the context of an adaptive, developing neural system. We will make the case for a pathophysiological process that begins with cortical hyperexcitability and bottom-up noise transmission, which engenders inappropriate belief formation via aberrant prediction error signaling. We will argue that this bottom-up noise drives learning about the (im)precision of new incoming sensory information because of diminished signal-to-noise ratio, causing an adaptive relative over-reliance on prior beliefs. This over-reliance on priors predisposes to hallucinations and covaries with hallucination severity. An over-reliance on priors may also lead to increased conviction in the beliefs generated by bottom-up noise and drive movement toward conversion to psychosis. We will identify predictions of our model at each stage, examine evidence to support or refute those predictions, and propose experiments that could falsify or help select between alternative elements of the overall model. Nesting computational abnormalities within longitudinal development allows us to account for hidden dynamics among the mechanisms driving symptom formation and to view established symptomatology as a point of equilibrium among competing biological forces.

Types of memory, dementia, Alzheimer's disease, and their various pathological cascades as targets for potential pharmacological drugs

Alzheimer's disease (AD) is the most common type of dementia accounting for 90% of cases; however, frontotemporal dementia, vascular dementia, etc. prevails only in a minority of populations. The term dementia is defined as loss of memory which further takes several other categories of memories like working memory, spatial memory, fear memory, and long-term, and short-term memory into consideration. In this review, these memories have critically been elaborated based on context, duration, events, appearance, intensity, etc. The most important part and purpose of the review is the various pathological cascades as well as molecular levels of targets of AD, which have extracellular amyloid plaques and intracellular hyperphosphorylated tau protein as major disease hallmarks. There is another phenomenon that either leads to or arises from the above-mentioned hallmarks, such as oxidative stress, mitochondrial dysfunction, neuroinflammation, cholinergic dysfunction, and insulin resistance. Several potential drugs like antioxidants, anti-inflammatory drugs, acetylcholinesterase inhibitors, insulin mimetics or sensitizers, etc. studied in various previous preclinical or clinical reports were put as having the capacity to act on these pathological targets. Additionally, agents directly or indirectly targeting amyloid and tau were also discussed. This could be further investigated in future research.

Characterizing the binding of TC-5619 and encenicline on the alpha7 nicotinic acetylcholine receptor using PET imaging in the pig

The alpha7 nicotinic acetylcholine receptor (α7-nAChR) has has long been considered a promising therapeutic target for addressing cognitive impairments associated with a spectrum of neurological and psychiatric disorders, including Alzheimer's disease and schizophrenia. However, despite this potential, clinical trials employing α7-nAChR (partial) agonists such as TC-5619 and encenicline (EVP-6124) have fallen short in demonstrating sufficient efficacy. We here investigate the target engagement of TC-5619 and encenicline in the pig brain by use of the α7-nAChR radioligand 11C-NS14492 to characterize binding both with in vitro autoradiography and in vivo occupancy using positron emission tomography (PET). In vitro autoradiography demonstrates significant concentration-dependent binding of 11C-NS14492, and both TC-5619 and encenicline can block this binding. Of particular significance, our in vivo investigations demonstrate that TC-5619 achieves substantial α7-nAChR occupancy, effectively blocking approximately 40% of α7-nAChR binding, whereas encenicline exhibits more limited α7-nAChR occupancy. This study underscores the importance of preclinical PET imaging and target engagement analysis in informing clinical trial strategies, including dosing decisions.

Pharmacological management of neurocognitive impairment in schizophrenia: A narrative review

BACKGROUND

Cognitive impairment are among the core features of schizophrenia, experienced by up to 75% of patients. Available treatment options for schizophrenia including dopamine antagonists and traditional antipsychotic medications have not been shown to confer significant benefits on cognitive deficits. Contrary to the focus on management of positive symptoms in schizophrenia, cognitive abilities are main predictor of independent living skills, functional abilities, employment, engagement in relapse prevention, and patients' subjective sense of well-being and quality of life. This review aims to provide a summary of recent literature on pharmacological options for the treatment of cognitive deficits in schizophrenia.

METHODS

We conducted a literature search of studies from 2011 to 2021 across four electronic databases including PubMed, PsycInfo, MEDLINE, and Embase. Human studies using a pharmacological treatment for cognitive impairment in schizophrenia were included.

RESULTS

Fifty-eight eligible publications, representing 11 pharmacological classes, were included in this review. Major limitations involved small sample size, methodological limitations as well as heterogeneity of participants and outcome measures.

CONCLUSIONS

Overall evidence remains inconclusive for any pharmacological classes studied for the treatment of cognitive deficits in schizophrenia. Methodological limitations in a majority of the studies rendered their findings preliminary. We further discuss possible explanations for these findings that could guide future research.

Metformin improves cognitive impairment in patients with schizophrenia: associated with enhanced functional connectivity of dorsolateral prefrontal cortex

Cognitive impairment is a core feature of schizophrenia, which is aggravated by antipsychotics-induced metabolic disturbance and lacks effective pharmacologic treatments in clinical practice. Our previous study demonstrated the efficiency of metformin in alleviating metabolic disturbance following antipsychotic administration. Here we report that metformin could ameliorate cognitive impairment and improve functional connectivity (FC) in prefrontal regions. This is an open-labeled, evaluator-blinded study. Clinically stable patients with schizophrenia were randomly assigned to receive antipsychotics plus metformin (N = 48) or antipsychotics alone (N = 24) for 24 weeks. The improvement in cognition was assessed by the MATRICS Consensus Cognitive Battery (MCCB). Its association with metabolic measurements, and voxel-wise whole-brain FC with dorsolateral prefrontal cortex (DLPFC) subregions as seeds were evaluated. When compared to the antipsychotics alone group, the addition of metformin resulted in significantly greater improvements in the MCCB composite score, speed of processing, working memory, verbal learning, and visual learning. A significant time × group interaction effect of increased FC between DLPFC and the anterior cingulate cortex (ACC)/middle cingulate cortex (MCC), and between DLPFC subregions were observed after metformin treatment, which was positively correlated with MCCB cognitive performance. Furthermore, the FC between left DLPFC A9/46d to right ACC/MCC significantly mediated metformin-induced speed of processing improvement; the FC between left A46 to right ACC significantly mediated metformin-induced verbal learning improvement. Collectively, these findings demonstrate that metformin can improve cognitive impairments in schizophrenia patients and is partly related to the FC changes in the DLPFC. Trial Registration: The trial was registered with ClinicalTrials.gov (NCT03271866). The full trial protocol is provided in Supplementary Material.

Imaging Cholinergic Receptors in the Brain by Positron Emission Tomography

Cholinergic receptors represent a promising class of diagnostic and therapeutic targets due to their significant involvement in cognitive decline associated with neurological disorders and neurodegenerative diseases as well as cardiovascular impairment. Positron emission tomography (PET) is a noninvasive molecular imaging tool that has helped to shed light on the roles these receptors play in disease development and their diverse functions throughout the central nervous system (CNS). In recent years, there has been a notable advancement in the development of PET probes targeting cholinergic receptors. The purpose of this review is to provide a comprehensive overview of the recent progress in the development of these PET probes for cholinergic receptors with a specific focus on ligand structure, radiochemistry, and pharmacology as well as in vivo performance and applications in neuroimaging. The review covers the structural design, pharmacological properties, radiosynthesis approaches, and preclinical and clinical evaluations of current state-of-the-art PET probes for cholinergic receptors.

Microglia and cognitive impairment in schizophrenia: translating scientific progress into novel therapeutic interventions

Cognitive impairment is a core clinical feature of schizophrenia, exerting profound adverse effects on social functioning and quality of life in a large proportion of patients with schizophrenia. However, the mechanisms underlying the pathogenesis of schizophrenia-related cognitive impairment are not well understood. Microglia, the primary resident macrophages in the brain, have been shown to play important roles in psychiatric disorders, including schizophrenia. Increasing evidence has revealed excessive microglial activation in cognitive deficits related to a broad range of diseases and medical conditions. Relative to that about age-related cognitive deficits, current knowledge about the roles of microglia in cognitive impairment in neuropsychiatric disorders, such as schizophrenia, is limited, and such research is in its infancy. Thus, we conducted this review of the scientific literature with a focus on the role of microglia in schizophrenia-associated cognitive impairment, aiming to gain insight into the roles of microglial activation in the onset and progression of such impairment and to consider how scientific advances could be translated to preventive and therapeutic interventions. Research has demonstrated that microglia, especially those in the gray matter of the brain, are activated in schizophrenia. Upon activation, microglia release key proinflammatory cytokines and free radicals, which are well-recognized neurotoxic factors contributing to cognitive decline. Thus, we propose that the inhibition of microglial activation holds potential for the prevention and treatment of cognitive deficits in patients with schizophrenia. This review identifies potential targets for the development of new treatment strategies and eventually the improvement of care for these patients. It might also help psychologists and clinical investigators in planning future research.

Increased Metabolic Potential, Efficacy, and Safety of Emerging Treatments in Schizophrenia

Patients with schizophrenia experience a broad range of detrimental health outcomes resulting from illness severity, heterogeneity of disease, lifestyle behaviors, and adverse effects of antipsychotics. Because of these various factors, patients with schizophrenia have a much higher risk of cardiometabolic abnormalities than people without psychiatric illness. Although exposure to many antipsychotics increases cardiometabolic risk factors, mortality is higher in patients who are not treated versus those who are treated with antipsychotics. This indicates both direct and indirect benefits of adequately treated illness, as well as the need for beneficial medications that result in fewer cardiometabolic risk factors and comorbidities. The aim of the current narrative review was to outline the association between cardiometabolic dysfunction and schizophrenia, as well as discuss the confluence of factors that increase cardiometabolic risk in this patient population. An increased understanding of the pathophysiology of schizophrenia has guided discovery of novel treatments that do not directly target dopamine and that not only do not add, but may potentially minimize relevant cardiometabolic burden for these patients. Key discoveries that have advanced the understanding of the neural circuitry and pathophysiology of schizophrenia now provide possible pathways toward the development of new and effective treatments that may mitigate the risk of metabolic dysfunction in these patients. Novel targets and preclinical and clinical data on emerging treatments, such as glycine transport inhibitors, nicotinic and muscarinic receptor agonists, and trace amine-associated receptor-1 agonists, offer promise toward relevant therapeutic advancements. Numerous areas of investigation currently exist with the potential to considerably progress our knowledge and treatment of schizophrenia.

Early auditory processing dysfunction in schizophrenia: Mechanisms and implications

Schizophrenia is a major mental disorder that affects approximately 1% of the population worldwide. Cognitive deficits are a key feature of the disorder and a primary cause of long-term disability. Over the past decades, significant literature has accumulated demonstrating impairments in early auditory perceptual processes in schizophrenia. In this review, we first describe early auditory dysfunction in schizophrenia from both a behavioral and neurophysiological perspective and examine their interrelationship with both higher order cognitive constructs and social cognitive processes. Then, we provide insights into underlying pathological processes, especially in relationship to glutamatergic and N-methyl-D-aspartate receptor (NMDAR) dysfunction models. Finally, we discuss the utility of early auditory measures as both treatment targets for precision intervention and as translational biomarkers for etiological investigation. Altogether, this review points out the crucial role of early auditory deficits in the pathophysiology of schizophrenia, in addition to major implications for early intervention and auditory-targeted approaches.

Cross-diagnostic determinants of cognitive functioning: the muscarinic cholinergic receptor as a model system

Cognitive impairment is a predictor of disability across different neuropsychiatric conditions, and cognitive abilities are also strongly related to educational attainment and indices of life success in the general population. Previous attempts at drug development for cognitive enhancement have commonly attempted to remedy defects in transmitters systems putatively associated with the conditions of interest such as the glutamate system in schizophrenia. Recent studies of the genomics of cognitive performance have suggested influences that are common in the general population and in different neuropsychiatric conditions. Thus, it seems possible that transmitter systems that are implicated for cognition across neuropsychiatric conditions and the general population would be a viable treatment target. We review the scientific data on cognition and the muscarinic cholinergic receptor system (M1 and M4) across different diagnoses, in aging, and in the general population. We suggest that there is evidence suggesting potential beneficial impacts of stimulation of critical muscarinic receptors for the enhancement of cognition in a broad manner, as well as the treatment of psychotic symptoms. Recent developments make stimulation of the M1 receptor more tolerable, and we identify the potential benefits of M1 and M4 receptor stimulation as a trans-diagnostic treatment model.

Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na²⁺ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.

Beyond monoamines: II. Novel applications for PET imaging in psychiatric disorders

Early applications of positron emission tomography (PET) in psychiatry sought to identify derangements of cerebral blood flow and metabolism. The need for more specific neurochemical imaging probes was soon evident, and these probes initially targeted the sites of action of neuroleptic (dopamine D₂ receptors) and psychoactive (serotonin receptors) drugs. For nearly 30 years, the centrality of monoamine dysfunction in psychiatric disorders drove the development of an armamentarium of monoaminergic PET radiopharmaceuticals and imaging methodologies. However, continued investments in monoamine-enhancing drug development realized only modest gains in efficacy and tolerability. As patent protection for many widely prescribed and profitable psychiatric drugs lapsed, drug development pipelines shifted away from monoamines in search of novel targets with the promises of improved efficacy, or abandoned altogether. Over this period, PET radiopharmaceutical development activities closely parallelled drug development priorities, resulting in the development of new PET imaging agents for non-monoamine targets. In part two of this review, we survey clinical research studies using the novel targets and radiotracers described in part one across major psychiatric application areas such as substance use disorders, anxiety disorders, eating disorders, personality disorders, mood disorders, and schizophrenia. Important limitations of the studies described are discussed, as well as key methodologic issues, challenges to the field, and the status of clinical trials seeking to exploit these targets for novel therapeutics.

A review of therapeutic failures in late-stage clinical trials

INTRODUCTION

The process of drug approval involves extensive and expensive preclinical and clinical examination. Most drugs entering late-stage clinical trials get terminated for a variety of reasons including inability to achieve the primary endpoints or intolerable adverse effects. Only one-tenth of the drugs that enter clinical trials progress to Food and Drug Administration (FDA) regulatory submission.

AREAS COVERED

This review offers insight into some of the attributes that may be responsible for a drug's failure in late-stage trials. Information from multiple open sources including PubMed articles published between 1989 and 2019, recent articles from authentic websites like www.ClinicalTrials.gov, www.fda.gov, and pharmaceutical news articles for the years between 2017 and 2021 were accumulated and summarized. Further, a few drug candidates that reached the phase III clinical trials but were discontinued at later stages have been presented as case studies.

EXPERT OPINION

Ineluctable failures were observed due to insufficient knowledge about the mechanism of action where the disease progression stages are unclear. Other reasons were choice of patient population, late-stage treatment, and dosage. Adhering to the guidelines and recommendations provided by the regulatory authorities and learning from past failures, considerably reduce failure rates.

Experimental Medicine Approaches in Early-Phase CNS Drug Development

Traditionally, Phase 1 clinical trials were largely conducted in healthy normal volunteers and focused on collection of safety, tolerability, and pharmacokinetic data. However, in the CNS therapeutic area, with more drugs failing in later phase development, Phase 1 trials have undergone an evolution that includes incorporation of novel approaches involving novel study designs, inclusion of biomarkers, and early inclusion of patients to improve the pharmacologic understanding of novel CNS-active compounds early in clinical development with the hope of improving success in later phase pivotal trials. In this chapter, the authors will discuss the changing landscape of Phase 1 clinical trials in CNS, including novel trial methodology, inclusion of pharmacodynamic biomarkers, and experimental medicine approaches to inform early decision-making in clinical development.

Strategies for Treatment of Disease-Associated Dementia Beyond Alzheimer's Disease: An Update

Memory, cognition, dementia, and neurodegeneration are complexly interlinked processes with various mechanistic pathways, leading to a range of clinical outcomes. They are strongly associated with pathological conditions like Alzheimer's disease, Parkinson's disease, schizophrenia, and stroke and are a growing concern for their timely diagnosis and management. Several cognitionenhancing interventions for management include non-pharmacological interventions like diet, exercise, and physical activity, while pharmacological interventions include medicinal agents, herbal agents, and nutritional supplements. This review critically analyzed and discussed the currently available agents under different drug development phases designed to target the molecular targets, including cholinergic receptor, glutamatergic system, GABAergic targets, glycine site, serotonergic targets, histamine receptors, etc. Understanding memory formation and pathways involved therein aids in opening the new gateways to treating cognitive disorders. However, clinical studies suggest that there is still a dearth of knowledge about the pathological mechanism involved in neurological conditions, making the dropouts of agents from the initial phases of the clinical trial. Hence, a better understanding of the disease biology, mode of drug action, and interlinked mechanistic pathways at a molecular level is required.

Cholinergic Functioning, Cognition, and Anticholinergic Medication Burden in Schizophrenia

Acetylcholine (ACh) signaling is critical for central nervous function and is known to be abnormal in schizophrenia (SZ), a chronic neuropsychiatric disorder in which cognitive deficits persist, despite treatment. This review provides a summary of the clinical evidence linking ACh abnormalities to SZ-associated cognitive deficits, an overview of ACh-based pro-cognitive strategies attempted in SZ, and a survey of recent studies that describe the impact of anticholinergic medication burden on cognitive outcomes in SZ. Methodological challenges that currently limit more substantial investigation of ACh in SZ patients and future directions are also discussed.

The contribution of ion channels to shaping macrophage behaviour

The expanding roles of macrophages in physiological and pathophysiological mechanisms now include normal tissue homeostasis, tissue repair and regeneration, including neuronal tissue; initiation, progression, and resolution of the inflammatory response and a diverse array of anti-microbial activities. Two hallmarks of macrophage activity which appear to be fundamental to their diverse cellular functionalities are cellular plasticity and phenotypic heterogeneity. Macrophage plasticity allows these cells to take on a broad spectrum of differing cellular phenotypes in response to local and possibly previous encountered environmental signals. Cellular plasticity also contributes to tissue- and stimulus-dependent macrophage heterogeneity, which manifests itself as different macrophage phenotypes being found at different tissue locations and/or after different cell stimuli. Together, plasticity and heterogeneity align macrophage phenotypes to their required local cellular functions and prevent inappropriate activation of the cell, which could lead to pathology. To execute the appropriate function, which must be regulated at the qualitative, quantitative, spatial and temporal levels, macrophages constantly monitor intracellular and extracellular parameters to initiate and control the appropriate cell signaling cascades. The sensors and signaling mechanisms which control macrophages are the focus of a considerable amount of research. Ion channels regulate the flow of ions between cellular membranes and are critical to cell signaling mechanisms in a variety of cellular functions. It is therefore surprising that the role of ion channels in the macrophage biology has been relatively overlooked. In this review we provide a summary of ion channel research in macrophages. We begin by giving a narrative-based explanation of the membrane potential and its importance in cell biology. We then report on research implicating different ion channel families in macrophage functions. Finally, we highlight some areas of ion channel research in macrophages which need to be addressed, future possible developments in this field and therapeutic potential.

An Update on Treatment of Cognitive Impairment Associated with Schizophrenia

Cognitive impairment associated with schizophrenia (CIAS) is widely regarded as a critically important treatment target for schizophrenia. Despite major efforts and a number of promising findings, we do not yet have an approved drug for CIAS. Similarly, promising cognitive remediation approaches are limited in their ability to help patients achieve real-world functional gains on a wide scale. This article provides an update and critical evaluation of recent treatment development activities for CIAS. First, we provide update on pharmacological approaches, which include a glutamatergic drug that is currently in Phase III trials for CIAS, and discuss factors that may have impacted past efforts to identify efficacious drugs. Second, we review positive findings, limitations, and current trends involving cognitive remediation approaches. Third, we consider newer transdiagnostic approaches aimed at looking beyond, or identifying more homogenous subgroups within, the diagnostic category schizophrenia to advance treatment development. Despite its many challenges, treatment development for CIAS remains a major public health issue and research continues to push forward on several encouraging fronts.

TOBACCO USE DISORDER AND DUAL DISORDERS Joint statement by the Spanish Psychiatry Society and the Spanish Dual Disorders Society

Tobacco Use Disorder (TUD) is a health problem of the first order in the world population, affecting a vulnerable population, such as people with other mental disorders, whose morbidity and mortality are increased as a result.

Selective 5HT3 antagonists and sensory processing: a systematic review

Ondansetron is a selective serotonin (5HT3) receptor antagonist that is under evaluation as an adjunctive treatment for schizophrenia, and a novel treatment for hallucinations in Parkinson's disease. Ondansetron reverses sensory gating deficits and improves visuoperceptual processing in animal models of psychosis, but it is unclear to what extent preclinical findings have been replicated in humans. We systematically reviewed human studies that evaluated the effects of ondansetron and other 5HT3 receptor antagonists on sensory gating deficits or sensory processing. Of 11 eligible studies, eight included patients with schizophrenia who were chronically stable on antipsychotic medication; five measured sensory gating using the P50 suppression response to a repeated auditory stimulus; others included tests of visuoperceptual function. Three studies in healthy participants included tests of visuoperceptual and sensorimotor function. A consistent and robust finding (five studies) was that ondansetron and tropisetron (5HT3 antagonist and α7-nicotinic receptor partial agonist) improved sensory gating in patients with schizophrenia. Tropisetron also improved sustained visual attention in non-smoking patients. There was inconsistent evidence of the effects of 5HT3 antagonists on other measures of sensory processing, but interpretation was limited by the small number of studies, methodological heterogeneity and the potential confounding effects of concomitant medication in patients. Despite these limitations, we found strong evidence that selective 5HT3 antagonists (with or without direct α7-nicotinic partial agonist effects) improved sensory gating. Future studies should investigate how this relates to potential improvement in neurocognitive symptoms in antipsychotic naive patients with prodromal or milder symptoms, in order to understand the clinical implications.

Progress and Pitfalls in Developing Agents to Treat Neurocognitive Deficits Associated with Schizophrenia

Cognitive impairments associated with schizophrenia (CIAS) represent a central element of the symptomatology of this severe mental disorder. CIAS substantially determine the disease prognosis and hardly, if at all, respond to treatment with currently available antipsychotics. Remarkably, all drugs presently approved for the treatment of schizophrenia are, to varying degrees, dopamine D₂/D₃ receptor blockers. In turn, rapidly growing evidence suggests the immense significance of systems other than the dopaminergic system in the genesis of CIAS. Accordingly, current efforts addressing the unmet needs of patients with schizophrenia are primarily based on interventions in other non-dopaminergic systems. In this review article, we provide a brief overview of the available evidence on the importance of specific systems in the development of CIAS. In addition, we describe the promising targets for the development of new drugs that have been used so far. In doing so, we present the most important candidates that have been investigated in the field of the specific systems in recent years and present a summary of the results available at the time of drafting this review (May 2022), as well as the currently ongoing studies.

The molecular mechanism, targets, and novel molecules in the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurological illness that causes dementia mainly in the elderly. The challenging obstacles related to AD has freaked global healthcare system to encourage scientists in developing novel therapeutic startegies to overcome with the fatal disease. The current treatment therapy of AD provides only symptomatic relief and to some extent disease-modifying effects. The current approach for AD treatment involves designing of cholinergic inhibitors, Aβ disaggregation inducing agents, tau inhibitors and several antioxidants. Hence, extensive research on AD therapy urgently requires a deep understanding of its pathophysiology and exploration of various chemical scaffolds to design and develop a potential drug candidate for the treatment. Various issues linked between disease and therapy need to be considered such as BBB penetration capability, clinical failure and multifaceted pathophisiology requires a proper attention to develop a lead candidate. This review article covers all probable mechanisms including one of the recent areas for investigation i.e., lipid dyshomeostasis, pathogenic involvement of P. gingivalis and neurovascular dysfunction, recently reported molecules and drugs under clinical investigations and approved by FDA for AD treatment. Our summarized information on AD will attract the researchers to understand and explore current status and structural modifications of the recently reported heterocyclic derivatives in drug development for AD therapy.

HTS-based discovery and optimization of novel positive allosteric modulators of the α7 nicotinic acetylcholine receptor

HTS campaign of the corporate compound collection resulted in a novel, oxalic acid diamide scaffold of α7 nACh receptor positive allosteric modulators. During the hit expansion, several derivatives, such as 4, 11, 17 demonstrated not only high in vitro potency, but also in vivo efficacy in the mouse place recognition test. The advanced hit molecule 11 was further optimized by the elimination of the putatively mutagenic aromatic-amine building block that resulted in a novel, aminomethylindole compound family. The most balanced physico-chemical and pharmacological profile was found in case of compound 55. Docking study revealed an intersubunit binding site to be the most probable for our compounds. 55 demonstrated favorable cognitive enhancing profile not only in scopolamine-induced amnesia (place recognition test in mice) but also in natural forgetting (novel object recognition test in rats). Compound 55 was, furthermore, active in a cognitive paradigm of high translational value, namely in the rat touch screen visual discrimination test. Therefore, 55 was selected as a lead compound for further optimization. Based on the obtained favorable results, the invented aminomethylindole cluster may provide a viable approach for cognitive enhancement through positive allosteric modulation of α7 nAChRs.

Aged rhesus monkeys: Cognitive performance categorizations and preclinical drug testing

Rodent models have facilitated major discoveries in neurobiology, however, the low success rate of novel medications in clinical trials have led to questions about their translational value in neuropsychiatric drug development research. For age-related disorders of cognition such as Alzheimer' disease (AD) there is interest in moving beyond transgenic amyloid-β and/or tau-expressing rodent models and focusing more on natural aging and dissociating "healthy" from "pathological" aging to identify new therapeutic targets and treatments. In complex disorders such as AD, it can also be argued that animals with closer neurobiology to humans (e.g., nonhuman primates) should be employed more often particularly in the later phases of drug development. The purpose of the work described here was to evaluate the cognitive capabilities of rhesus monkeys across a wide range of ages in different delayed response tasks, a computerized delayed match to sample (DMTS) task and a manual delayed match to position (DMTP) task. Based on specific performance criteria and comparisons to younger subjects, the older subjects were generally less proficient, however, some performed as well as young subjects, while other aged subjects were markedly impaired. Accordingly, the older subjects could be categorized as aged "cognitively-unimpaired" or aged "cognitively-impaired" with a third group (aged-other) falling in between. Finally, as a proof of principle, we demonstrated using the DMTP task that aged cognitively-impaired monkeys are sensitive to the pro-cognitive effects of a nicotinic acetylcholine receptor (nAChR) partial agonist, encenicline, suggesting that nAChR ligands remain viable as potential treatments for age-related disorders of cognition.

Efficacy and safety of the novel glycine transporter inhibitor BI 425809 once daily in patients with schizophrenia: a double-blind, randomised, placebo-controlled phase 2 study

BACKGROUND

Cognitive impairment associated with schizophrenia predicts poor functional outcomes, but currently no approved pharmacotherapy is available. This study investigated whether the glycine transporter-1 inhibitor BI 425809 improves cognition in patients with schizophrenia.

METHODS

This phase 2, randomised, double-blind, placebo-controlled, parallel-group trial (81 centres, 11 countries), randomly assigned outpatients (aged 18-50 years) with schizophrenia on stable treatment to add-on once-daily oral BI 425809 2 mg, 5 mg, 10 mg, or 25 mg or placebo (1:1:1:1:2) for 12 weeks. Treatment was assigned in blocks using interactive response technology; patients, investigators, and all trial personnel were masked to group assignment. The primary endpoint was change from baseline in MATRICS Consensus Cognitive Battery (MCCB) overall composite T-score at week 12. Six predefined dose-response models were evaluated using a multiple comparison procedure and modelling approach with mixed model repeated measures to assess evidence for a non-flat dose-response relationship for cognitive improvements with BI 425809. Adverse events were monitored. Safety analyses included all randomly allocated patients who received one or more doses of trial medication; efficacy analyses included patients from this set who also had available baseline data and at least one post-baseline on-treatment measurement for the primary or secondary endpoint. This study is registered with ClinicalTrials.gov, number NCT02832037.

FINDINGS

509 patients were randomly assigned between April 25, 2018, and Oct 4, 2019 (BI 425809 2 mg, n=85; 5 mg, n=84; 10 mg, n=85; 25 mg, n=85; placebo, n=170 444 (87%) completed the 12-week treatment. Five of six dose-response models showed a statistically significant benefit of BI 425809 over placebo (linear [t=2·55, p=0·015], linear in log [t=2·56, p=0·015]; Emax [t=2·75, p=0·0089], sigmoid Emax [t=2·98, p=0·0038], logistic [t=2·77, p=0·0085]). Pairwise comparisons showed greater mean improvement from baseline in MCCB overall composite T-score at week 12 with BI 425809 10 mg and 25 mg versus placebo (adjusted mean difference 1·98 [95% CI 0·43-3·53] for 10 mg and 1·73 [0·18-3·28] for 25 mg; standardised effect size 0·34 for 10 mg and 0·30 for 25 mg). Adverse events were balanced across groups, reported in 50 (59%) of 85 patients on BI 425809 2 mg, 44 (52%) of 84 on 5 mg, 35 (41%) of 85 on 10 mg, 36 (42%) of 85 on 25 mg, and 74 (44%) of 170 on placebo.

INTERPRETATION

BI 425809 improved cognition after 12 weeks in patients with schizophrenia; doses of 10 mg and 25 mg showed the largest separation from placebo. If these encouraging results are confirmed in phase 3 trials, BI 425809 could provide an effective treatment for cognitive impairment associated with schizophrenia.

FUNDING

Boehringer Ingelheim.

Cognitive Enhancers in Schizophrenia: A Systematic Review and Meta-Analysis of Alpha-7 Nicotinic Acetylcholine Receptor Agonists for Cognitive Deficits and Negative Symptoms

Background: Schizophrenia is a severe and enduring disease and is one of the leading causes of disability worldwide. Cognitive impairment is a core clinical symptom that plays a crucial role in functional outcomes and prognosis, thus making it a relevant treatment target. The aim of this study was to assess the efficacy of alpha-7 nicotinic acetylcholine receptor agonists (α7 nAChR) as adjunctive treatment to enhance cognition and ameliorate negative symptoms in patients with schizophrenia. Methods: A search strategy was developed for MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials up to May 2019. We included randomized controlled trials (RCTs) that compared antipsychotic treatment plus α7 nAChR agonists with antipsychotic treatment plus placebo and determined their effects on the main cognitive domains proposed by the MATRICS initiative and on negative symptoms. Two authors independently reviewed study eligibility and data extraction and assessed the risk of bias of the studies included. According to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework, we used a random-effects model and assessed the quality of the evidence. Results: Thirteen studies were included in the quantitative analysis. No differences were found in any of the cognitive domains assessed in four RCTs (n = 414). In contrast, nine RCTs (n = 978) presented a small effect in support of α7 nAChR agonists for negative symptoms [standardized mean difference -0.28, 95% CI (-0.56 to -0.00); P = 0.05], even though the confidence to support this evidence is low according to the GRADE system. Conclusions: Current evidence is too weak to consider α7 nAChR agonists as an effective add-on treatment to antipsychotics to enhance cognition and negative symptoms.

Alpha7 nicotinic-N-methyl-D-aspartate hypothesis in the treatment of schizophrenia and beyond

Development of novel treatments for positive, cognitive, and negative symptoms continue to be a high-priority area of schizophrenia research and a major unmet clinical need. Given that all randomized controlled trials (RCTs) conducted to date failed with one add-on medication/mechanism of action, future RCTs with the same approach are not warranted. Even if the field develops a medication for cognition, others are still needed to treat negative and positive symptoms. Therefore, fixing one domain does not completely solve the problem. Also, targeting the cholinergic system, glutamatergic system, and cholinergic plus alpha7 nicotinic and N-methyl-D-aspartate (NMDA) receptors failed independently. Hence, targeting other less important pathophysiological mechanisms/targets is unlikely to be successful. Meta-analyses of RCTs targeting major pathophysiological mechanisms have found some efficacy signal in schizophrenia; thus, combination treatments with different mechanisms of action may enhance the efficacy signal. The objective of this article is to highlight the importance of conducting RCTs with novel combination treatments in schizophrenia to develop antischizophrenia treatments. Positive RCTs with novel combination treatments that target the alpha7 nicotinic and NMDA receptors simultaneously may lead to a disease-modifying therapeutic armamentarium in schizophrenia. Novel combination treatments that concurrently improve the three domains of psychopathology and several prognostic and theranostic biomarkers may facilitate therapeutic discovery in schizophrenia.

The Role of Estrogen Receptors and Their Signaling across Psychiatric Disorders

Increasing evidence suggests estrogen and estrogen signaling pathway disturbances across psychiatric disorders. Estrogens are not only crucial in sexual maturation and reproduction but are also highly involved in a wide range of brain functions, such as cognition, memory, neurodevelopment, and neuroplasticity. To add more, the recent findings of its neuroprotective and anti-inflammatory effects have grown interested in investigating its potential therapeutic use to psychiatric disorders. In this review, we analyze the emerging literature on estrogen receptors and psychiatric disorders in cellular, preclinical, and clinical studies. Specifically, we discuss the contribution of estrogen receptor and estrogen signaling to cognition and neuroprotection via mediating multiple neural systems, such as dopaminergic, serotonergic, and glutamatergic systems. Then, we assess their disruptions and their potential implications for pathophysiologies in psychiatric disorders. Further, in this review, current treatment strategies involving estrogen and estrogen signaling are evaluated to suggest a future direction in identifying novel treatment strategies in psychiatric disorders.

Meta-analysis of randomized controlled trials of galantamine in schizophrenia: significant cognitive enhancement

Cognitive impairments are core features of schizophrenia and the best predictor of functional outcome. Cholinergic system and alpha-7 nicotinic acetylcholine (α7nACh) receptors are strongly implicated in the pathophysiologic mechanisms associated with cognitive impairments in schizophrenia. Galantamine is not only a reversible, competitive inhibitor of acetylcholinesterase but also a type I positive allosteric modulator of α7nACh receptors. The objective of this meta-analysis was to examine the efficacy of galantamine for cognitive symptoms of schizophrenia. In the meta-analysis that included six randomized controlled trials (RCTs, N=226), cognitive impairments significantly improved with galantamine compared to placebo, with a small Hedges' g effect size of 0.233. This finding is consistent with other RCTs in schizophrenia with medications with a similar mechanism of action. On the basis of the results from all the failed (although some efficacy has been shown) RCTs to date in schizophrenia, targeting only one pathophysiologic mechanism may be insufficient to detect a clinically meaningful signal. Nicotinergic medications, like any other add-on medications, are unlikely to be effective as stand-alone medications. Hence, these medications may have to be combined with other medications with complementary mechanisms such as glutamatergic/N-methyl-D-aspartate systems to detect a meaningful effect size for the three domains of psychopathology.

N-Acetylcysteine Inhibits Kynurenine Aminotransferase II

The tryptophan metabolite kynurenic acid (KYNA) may play an important role in normal and abnormal cognitive processes, most likely by interfering with α7 nicotinic and NMDA receptor function. KYNA is formed from its immediate precursor kynurenine either by non-enzymatic oxidation or through irreversible transamination by kynurenine aminotransferases. In the mammalian brain, kynurenine aminotransferase II (KAT II) is the principal enzyme responsible for the neosynthesis of rapidly mobilizable KYNA, and therefore constitutes an attractive target for pro-cognitive interventions. N-acetylcysteine (NAC), a brain-penetrant drug with pro-cognitive efficacy in humans, has been proposed to exert its actions by increasing the levels of the anti-oxidant glutathione (GSH) in the brain. We report here that NAC, but not GSH, inhibits KAT II activity in brain tissue homogenates from rats and humans with IC₅₀ values in the high micromolar to low millimolar range. With similar potency, the drug interfered with the de novo formation of KYNA in rat brain slices, and NAC was a competitive inhibitor of recombinant human KAT II (Ki: 450 μM). Furthermore, GSH failed to S-glutathionylate recombinant human KAT II treated with the dithiocarbamate drug disulfiram. Shown by microdialysis in the prefrontal cortex of rats treated with kynurenine (50 mg/kg, i.p.), peripheral administration of NAC (500 mg/kg, i.p., 120 and 60 min before the application of kynurenine) reduced KYNA neosynthesis by ∼50%. Together, these results suggest that NAC exerts its neurobiological effects at least in part by reducing cerebral KYNA formation via KAT II inhibition.

Double blind, two dose, randomized, placebo-controlled, cross-over clinical trial of the positive allosteric modulator at the alpha7 nicotinic cholinergic receptor AVL-3288 in schizophrenia patients

Despite their theoretical rationale, nicotinic alpha-7 acetylcholine (nα₇) receptor agonists, have largely failed to demonstrate efficacy in placebo-controlled trials in schizophrenia. AVL-3288 is a nα₇ positive allosteric modulator (PAM), which is only active in the presence of the endogenous ligand (acetylcholine), and thus theoretically less likely to cause receptor desensitization. We evaluated the efficacy of AVL-3288 in a Phase 1b, randomized, double-blind, placebo-controlled, triple cross-over study. Twenty-four non-smoking, medicated, outpatients with schizophrenia or schizoaffective disorder and a Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) ≥62 were randomized. Each subject received 5 days of AVL-3288 (10, 30 mg) and placebo across three separate treatment weeks. The primary outcome measure was the RBANS total scale score, with auditory P50 evoked potential suppression the key target engagement biomarker. Secondary outcome measures include task-based fMRI (RISE task), mismatch negativity, the Scale for the Assessment of Negative Symptoms of Schizophrenia (SANS) and the Brief Psychiatric Rating Scale (BPRS). Twenty-four subjects were randomized and treated without any clinically significant treatment emergent adverse effects. Baseline RBANS (82 ± 17) and BPRS (41 ± 13) scores were consistent with moderate impairment. Primary outcomes were negative, with non-significant worsening for both active groups vs. placebo in the P50 and minimal between group changes on the RBANS. In conclusion, the results did not indicate efficacy of the compound, consistent with most prior results for the nα₇ target.

Galantamine Inhibits Aβ1-42-Induced Neurotoxicity by Enhancing α7nAChR Expression as a Cargo Carrier for LC3 Binding and Aβ1-42 Engulfment During Autophagic Degradation

Despite Alzheimer's disease (AD) being the most common neurodegenerative disorder worldwide, no FDA-approved disease-modifying treatments have been approved for this condition since 2003. Neuronal-type alpha7 nicotinic acetylcholine receptors (α7nAChRs) play an essential role in cognitive functions, binding with extracellular β-amyloid (Aβ plaques) and inhibiting Aβ-induced neurotoxicity. α7nAChRs are impaired early in the course of AD; drugs targeting α7nAChRs are being hotly pursued as a treatment of AD. Encenicline, a partial selective agonist of α7nAChR and modulator of acetylcholine, failed in phase III trials because of gastrointestinal side effects. We, therefore, evaluated the efficacy of galantamine, a positive allosteric modulator at α7nAChRs and an acetylcholinesterase inhibitor, that has been used since 2000 as first-line treatment of mild-to-moderate dementia. This study highlights an important new benefit with galantamine. We found that galantamine inhibits Aβ1-42-induced apoptosis by activating the JNK signaling pathway, thus enhancing α7nAChR expression, and also inhibits the Akt pathway, which further increases autophagosome biogenesis and autophagy. These effects can be reproduced by α7nAChR overexpression in the absence of galantamine. Importantly, the α7 subunit protein sequence of α7nAChRs contains 3 LC3-interacting regions; our immunoprecipitation data show that α7 binds with the autophagosomal marker protein LC3. This is the first report to provide evidence showing that the cell surface receptor α7nAChR acts as a cargo carrier for LC3 binding for Aβ1-42 sequestration to autophagosomes, suggesting a novel mechanism for the neuroprotective efficacy of galantamine in AD.

Muscarinic M1 Receptors Modulate Working Memory Performance and Activity via KCNQ Potassium Channels in the Primate Prefrontal Cortex

Working memory relies on the dorsolateral prefrontal cortex (dlPFC), where microcircuits of pyramidal neurons enable persistent firing in the absence of sensory input, maintaining information through recurrent excitation. This activity relies on acetylcholine, although the molecular mechanisms for this dependence are not thoroughly understood. This study investigated the role of muscarinic M1 receptors (M1Rs) in the dlPFC using iontophoresis coupled with single-unit recordings from aging monkeys with naturally occurring cholinergic depletion. We found that M1R stimulation produced an inverted-U dose response on cell firing and behavioral performance when given systemically to aged monkeys. Immunoelectron microscopy localized KCNQ isoforms (Kv7.2, Kv7.3, and Kv7.5) on layer III dendrites and spines, similar to M1Rs. Iontophoretic manipulation of KCNQ channels altered cell firing and reversed the effects of M1R compounds, suggesting that KCNQ channels are one mechanism for M1R actions in the dlPFC. These results indicate that M1Rs may be an appropriate target to treat cognitive disorders with cholinergic alterations.

α7 nicotinic acetylcholine receptors as therapeutic targets in schizophrenia: Update on animal and clinical studies and strategies for the future

Schizophrenia is a devastating mental illness and its effective treatment is among the most challenging issues in psychiatry. The symptoms of schizophrenia are heterogeneous ranging from positive symptoms (e.g., delusions, hallucinations) to negative symptoms (e.g., anhedonia, social withdrawal) to cognitive dysfunction. Antipsychotics are effective at ameliorating positive symptoms in some patients; however, they are not reliably effective at improving the negative symptoms or cognitive impairments. The inability to address the cognitive impairments is a particular concern since they have the greatest long-term impact on functional outcomes. While decades of research have been devoted to the development of pro-cognitive agents for schizophrenia, to date, no drug has been approved for clinical use. Converging behavioral, neurobiological, and genetic evidence led to the identification of the α7-nicotinic acetylcholine receptor (α7-nAChR) as a therapeutic target several years ago and there is now extensive preclinical evidence that α7-nAChR ligands have pro-cognitive effects and other properties that should be beneficial to schizophrenia patients. However, like the other pro-cognitive strategies, no α7-nAChR ligand has been approved for clinical use in schizophrenia thus far. In this review, several topics are discussed that may impact the success of α7-nAChR ligands as pro-cognitive agents for schizophrenia including the translational value of the animal models used, clinical trial design limitations, confounding effects of polypharmacy, dose-effect relationships, and chronic versus intermittent dosing considerations. Determining the most optimal pharmacologic strategy at α7-nAChRs: agonist, positive allosteric modulator, or potentially even receptor antagonist is also discussed. article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

A Pharmacological Comparison of Two Isomeric Nicotinic Receptor Agonists: The Marine Toxin Isoanatabine and the Tobacco Alkaloid Anatabine

Many organisms possess "secondary" compounds to avoid consumption or to immobilize prey. While the most abundant or active compounds are initially investigated, more extensive analyses reveal other "minor" compounds with distinctive properties that may also be of biomedical and pharmaceutical significance. Here, we present an initial in vitro investigation of the actions of two isomeric tetrahydropyridyl ring-containing anabasine analogs: isoanatabine, an alkaloid isolated from a marine worm, and anatabine, a relatively abundant minor alkaloid in commercial tobacco plants. Both compounds have a double bond that is distal to the piperidine ring nitrogen of anabasine. Racemic isoanatabine and anatabine were synthesized and their S- and R-enantiomers were isolated by chiral high pressure liquid chromatography (HPLC). Both isoanatabines displayed higher efficacies at α4β2 nicotinic acetylcholine receptors (nAChRs) relative to the anatabines; R-isoanatabine was most potent. Radioligand binding experiments revealed similar α4β2 nAChR binding affinities for the isoanatabines, but R-anatabine affinity was twice that of S-anatabine. While the two anatabines and S-isoanatabine were highly efficacious agonists at α7 nAChRs, R-isoanatabine was only a weak partial agonist. The four compounds share an ability to stimulate both α4β2 and α7 nAChRs, a property that may be useful in developing more efficacious drugs to treat neurodegenerative and other medical disorders.

Progress and perspectives of brain-targeting lipid-based nanosystems via the nasal route in Alzheimer's disease

Since health care systems dedicate substantial resources to Alzheimer's disease (AD), it poses an increasing challenge to scientists and health care providers worldwide, especially that many decades of research in the medical field revealed no optimal effective treatment for this disease. The intranasal administration route seems to be a preferable route of anti-AD drug delivery over the oral one as it demonstrates an ability to overcome the related obstacles reflected in low bioavailability, limited brain exposure and undesired pharmacokinetics or side effects. This delivery route can bypass the systemic circulation through the intraneuronal and extraneuronal pathways, providing truly needleless and direct brain drug delivery of the therapeutics due to its large surface area, porous endothelial membrane, the avoidance of the first-pass metabolism, and ready accessibility. Among the different nano-carrier systems developed, lipid-based nanosystems have become increasingly popular and have proven to be effective in managing the common symptoms of AD when administered via the nose-to-brain delivery route, which provides an answer to circumventing the BBB. The design of such lipid-based nanocarriers could be challenging since many factors can contribute to the quality of the final product. Hence, according to the authors, it is recommended to follow the quality by design methodology from the early stage of development to ensure high product quality while saving efforts and costs. This review article aims to draw attention to the up-to-date findings in the field of lipid-based nanosystems and the potential role of developing such forms in the management of AD by means of the nose-to-brain delivery route, in addition to highlighting the significant role of applying QbD methodology in this development.

Activation of α7 nAChR by PNU-282987 improves synaptic and cognitive functions through restoring the expression of synaptic-associated proteins and the CaM-CaMKII-CREB signaling pathway

Ligands of nicotinic acetylcholine receptors (nAChRs) are widely considered as potential therapeutic agents. The present study used primary hippocampus cells and APPswe/PSEN1dE9 double-transgenic mice models to study the possible therapeutic effect and underlying mechanism of the specific activation of α7 nAChR by PNU-282987 in the pathogenesis of Alzheimer’s disease. The results indicated that activation of α7 nAChR attenuated the Aβ-induced cell apoptosis, decreased the deposition of Aβ, increased the expression of synaptic-associated proteins, and maintained synaptic morphology. Furthermore, in the APP/PS1_DT mice model, activation of α7 nAChR attenuated Aβ-induced synaptic loss, reduced the deposition of Aβ in the hippocampus, maintained the integral structure of hippocampus-derived synapse, and activated the calmodulin (CaM)-calmodulin-dependent protein kinase II (CaMKII)-cAMP response element-binding protein signaling pathway by upregulation of its key signaling proteins. In addition, activation of α7 nAChR improved the learning and memory abilities of the APP/PS1_DT mice. Collectively, the activation of α7 nAChR by PNU-282987 attenuated the toxic effect of Aβ in vivo and in vitro, which including reduced deposition of Aβ in the hippocampus, maintained synaptic morphology by partially reversing the expression levels of synaptic-associated proteins, activation of the Ca²⁺ signaling pathway, and improvement of the cognitive abilities of APP/PS1_DT mice.

A Review of the Cholinergic System and Therapeutic Approaches to Treat Brain Disorders

Since its identification over a hundred years ago, the neurotransmitter acetylcholine (ACh) has proven to play an essential role in supporting many diverse functions. Some well-characterized functions include: chemical transmission at the neuromuscular junction; autonomic function in the peripheral nervous system; and, sustained attention, sleep/wake regulation, and learning and memory within the central nervous system. Within the brain, major cholinergic projection pathways from the basal forebrain and the brainstem support these centrally mediated processes, and dysregulation of the cholinergic system is implicated in cognitive decline associated with aging and dementias including Alzheimer's disease. ACh exerts its effects by binding to two different membrane-bound receptor classes: (1) G‑protein coupled muscarinic acetylcholine receptors (mAChRs), and (2) ligand-gated nicotinic acetylcholine receptors (nAChRs). These receptor systems are described in detail within this chapter along with discussion on the successes and failures of synthetic ligands designed to selectively target receptor subtypes for treating brain disorders. New molecular approaches and advances in our understanding of the target biology combined with opportunities to re-purpose existing cholinergic drugs for new indications continue to highlight the exciting opportunities for modulating this system for therapeutic purposes.

Activators of α7 nAChR as Potential Therapeutics for Cognitive Impairment

The α7 nicotinic acetylcholine receptor (nAChR) is a promising target for the treatment of cognitive deficits associated with psychiatric and neurological disorders, including schizophrenia and Alzheimer's disease (AD). Several α7 nAChR agonists and positive allosteric modulators (PAMs) have demonstrated procognitive effects in preclinical models and early clinical trials. However, despite intense research efforts in the pharmaceutical industry and academia, none of the α7 nAChR ligands has been approved for clinical use. This chapter will focus on the α7 nAChR ligands that have advanced to clinical studies and explore the reasons why these agents have not met with unequivocal clinical success.

Evidence-based guidelines for the pharmacological treatment of schizophrenia: Updated recommendations from the British Association for Psychopharmacology

These updated guidelines from the British Association for Psychopharmacology replace the original version published in 2011. They address the scope and targets of pharmacological treatment for schizophrenia. A consensus meeting was held in 2017, involving experts in schizophrenia and its treatment. They were asked to review key areas and consider the strength of the evidence on the risk-benefit balance of pharmacological interventions and the clinical implications, with an emphasis on meta-analyses, systematic reviews and randomised controlled trials where available, plus updates on current clinical practice. The guidelines cover the pharmacological management and treatment of schizophrenia across the various stages of the illness, including first-episode, relapse prevention, and illness that has proved refractory to standard treatment. It is hoped that the practice recommendations presented will support clinical decision making for practitioners, serve as a source of information for patients and carers, and inform quality improvement.

Improving Cognition via Exercise (ICE): Study Protocol for a Multi-Site, Parallel-Group, Single-Blind, Randomized Clinical Trial Examining the Efficacy of Aerobic Exercise to Improve Neurocognition, Daily Functioning, and Biomarkers of Cognitive Change in Individuals with Schizophrenia

Individuals with schizophrenia (SZ) display cognitive deficits that have been identified as major determinants of poor functioning and disability, representing a serious public health concern and an important target for interventions. At present, available treatments offer only minimal to moderate benefits to ameliorate cognitive deficits. Thus, there remains an urgent need to identify novel interventions to improve cognition in people with SZ. Emerging evidence from animal and basic human research suggests aerobic exercise training (AE) has beneficial effects on cognition. Preliminary findings suggest that AE is efficacious in improving cognitive functioning in SZ, however the extant studies have been limited by small samples, a dearth of information on biologically-relevant covariates, and limited information on impact on daily functioning. Additionally, while AE-related cognitive benefits have been linked to Brain-Derived Neurotrophic Factor (BDNF) upregulation, this putative mechanism needs confirmation. The present report describes a study protocol designed to address these limitations-we review and summarize the current literature on treatment of cognitive deficits in SZ, state the rationale for employing AE to target these deficits, and describe the current protocol-a multi-site, single-blind, randomized clinical trial aiming to recruit 200 community-dwelling individuals with SZ. Participants are randomized to one of two 12-week interventions: AE using active-play video games (i.e., Xbox Kinect) and traditional cardiovascular exercise equipment or a stretching-and-toning (ST) control intervention. Participants undergo assessments of aerobic fitness, cognition, and daily functioning, as well as BDNF and other biomarkers of cognitive change, at baseline and after 6-and 12-weeks.

Alpha7 Nicotinic Receptors as Therapeutic Targets in Schizophrenia

While current treatments for schizophrenia often provide much relief for positive symptoms such as hallucinations, other symptoms, particularly cognitive deficits, persist and contribute to substantial suffering and reduced quality of life for patients. In searching for novel therapeutic avenues to treat cognitive deficits in schizophrenia, recent work is exploring nicotinic receptor neurobiology. Supported by a large body of evidence, with contributions from studies of smoking behaviors, genetics, receptor distribution and function, animal models and nicotinic effects on illness symptoms, the alpha7 nicotinic receptor has emerged as a potential therapeutic target. Despite promise in early clinical trials, however, no drug targeting nicotinic systems has succeeded in larger phase 3 trials. Following a brief review of nicotinic receptor biology and the evidence that has led to pursuit of alpha7 nicotinic agonism as a therapeutic strategy, this review will provide an update on the status of recent trials, discuss potential issues that may have contributed to negative outcomes, and point to new directions and promising advances in developing alpha7 nicotinic receptor-based treatment for cognitive symptoms in schizophrenia.

IMPLICATIONS

By examining alpha7 nicotinic receptor biology and recent efforts to target the receptor in clinical trials, it is hoped that investigators will be motivated to explore novel, promising directions focusing on the receptor as a strategy to treat cognitive symptoms in schizophrenia.

Discovery and Development of Non-Dopaminergic Agents for the Treatment of Schizophrenia: Overview of the Preclinical and Early Clinical Studies

Schizophrenia is a chronic psychiatric disorder that affects about 1 in 100 people around the world and results in persistent emotional and cognitive impairments. Untreated schizophrenia leads to deterioration in quality of life and premature death. Although the clinical efficacy of dopamine D2 receptor antagonists against positive symptoms of schizophrenia supports the dopamine hypothesis of the disease, the resistance of negative and cognitive symptoms to these drugs implicates other systems in its pathophysiology. Many studies suggest that abnormalities in glutamate homeostasis may contribute to all three groups of schizophrenia symptoms. Scientific considerations also include disorders of gamma-aminobutyric acid-ergic and serotonergic neurotransmissions as well as the role of the immune system. The purpose of this review is to update the most recent reports on the discovery and development of non-dopaminergic agents that may reduce positive, negative, and cognitive symptoms of schizophrenia, and may be alternative to currently used antipsychotics. This review collects the chemical structures of representative compounds targeting metabotropic glutamate receptor, gamma-aminobutyric acid type A receptor, alpha 7 nicotinic acetylcholine receptor, glycine transporter type 1 and glycogen synthase kinase 3 as well as results of in vitro and in vivo studies indicating their efficacy in schizophrenia. Results of clinical trials assessing the safety and efficacy of the tested compounds have also been presented. Finally, attention has been paid to multifunctional ligands with serotonin receptor affinity or phosphodiesterase inhibitory activity as novel strategies in the search for dedicated medicines for patients with schizophrenia.

Comprehensive review of the research employing the schizophrenia cognition rating scale (SCoRS)

This review of research utilizing the Schizophrenia Cognition Rating Scale (SCoRS) outlines the development, evaluation, validation, and implementation of the SCoRS to assess whether the scale meets the criteria as a functional co-primary as defined by the MATRICS-CT initiative. Interview-based co-primary assessments should be: 1) practical and easy to administer for a clinician or researcher; 2) validated in individuals with schizophrenia; 3) contain the relevant areas of cognition and functioning applicable to schizophrenia; 4) able to assess all phases and severity levels of schizophrenia; 5) capable of monitoring disease progression; 6) minimal burden to patients; and 7) sensitive to assess treatment effects. A review of the literature was conducted to present information on the development, psychometric properties and usage of the SCoRS. Review of the development of the SCoRS followed the parameters outlined for scale development on content expert validation and feedback. The SCoRS shows good psychometric properties in various studies, and demonstrates low burden on clinicians and patients. The items measure global concepts that do not require notable cultural modification, making international use feasible. While multiple performance-based tests in cognition and functional outcomes are available, there is a need for a multi-domain, interview-based assessment of cognitive progression and treatment response in clinical trials. The SCoRS appears to meet many of the criteria for an optimal co-primary measure for schizophrenia cognition clinical trials as defined in the MATRICS-CT initiative.

Keeping up with the therapeutic advances in schizophrenia: a review of novel and emerging pharmacological entities

Schizophrenia remains one of the most severe medical diseases. Current dopamine modulating first-generation and second-generation antipsychotics target mainly positive symptoms, but not/inadequately negative and cognitive symptoms. Additional challenges include non-adherence and adverse effects, especially cardiometabolic dysregulation. This review evaluates new/emerging pharmacological treatments for schizophrenia. Therapies targeting total symptoms include cannabidiol, D3 antagonist/5-HT1A partial agonist F17464, lumateperone (ITI-007), phosphodiesterase 10A (PDE10A) inhibitors MK-8189 and TAK-063, sodium nitroprusside, and trace amine-associated receptor-1 (TAAR1) agonist RO5263397 and SEP-363856. Treatments targeting negative symptoms include the PDE10A inhibitor LuAF-11167, 5-HT2A inverse agonist pimavanserin, sigma-2/5-HT2A antagonist roluperidone (MIN-101), and d-amino acid oxidase (DAAO) inhibitor TAK-831. Agents targeting primarily cognitive dysfunction are the glycine transporter-1 inhibitor BI-425809 and cannabidiol. Therapies targeting residual positive symptoms/treatment-resistant schizophrenia include pimavanserin, dopamine D1/D2 antagonist LuAF-35700, and DAAO inhibitor sodium benzoate. Two new long-acting injectable antipsychotic formulations, Aripiprazole Lauroxil NanoCrystal® and the first subcutaneous injectable LAI Perseris (RBP-7000), were recently approved by U.S. Food and Drug Administration, and positive results were announced for Risperidone ISM®, each achieving therapeutic levels within 24 hours, without need for initial oral cotreatment/loading injection-strategies. Paliperidone palmitate 6-monthly intramuscularly injectable and Risperidone subcutaneously injectable TV46000 are currently under investigation. Finally, the samidorphan+olanzapine combination targets reduced weight gain liability, while maintaining olanzapine's efficacy. Most of these trial programs are still ongoing or have yielded mixed or even negative results. Thus, additional mechanisms of action and agents require study to improve schizophrenia outcomes for total/positive symptoms with reduced adverse effects, but also cognitive symptoms, negative symptoms, and treatment resistance, the areas of greatest need in schizophrenia currently.

Perioperative activation of spinal α7 nAChR promotes recovery from preoperative stress-induced prolongation of postsurgical pain

Preoperative stress could delay the recovery of postoperative pain and has been reported to be a risk factor for chronic postsurgical pain. As stress could facilitate the proinflammatory activation of microglia, we hypothesized that these cells may play a vital role in the development of preoperative stress-induced pain chronification after surgery. Our experiments were conducted in a rat model that consists of a single prolonged stress (SPS) procedure and plantar incision. A previous SPS exposure induced anxiety-like behaviors, prolonged incision-induced mechanical allodynia, and potentiated the activation of spinal microglia. Based on the results from ex vivo experiments, spinal microglia isolated from SPS-exposed rats secreted more proinflammatory cytokines upon challenge with LPS. Our results also demonstrated that microglia played a more important role than astrocytes in the initiation of SPS-induced prolongation of postsurgical pain. We further explored the therapeutic potential of agonism of α7 nAChR, an emerging anti-inflammatory target, for SPS-induced prolongation of postsurgical pain. Multiple intrathecal (i.t.) injections of PHA-543613 (an α7 nAChR agonist) or PNU-120596 (a type II positive allosteric modulator) during the perioperative period shortened the duration of postsurgical pain after SPS and suppressed SPS-potentiated microglia activation, but their effects were abolished by pretreatment with methyllycaconitine (an α7 nAChR antagonist; i.t.). Based on the results from ex vivo experiments, the anti-inflammatory effects of PHA-543613 and PNU-120596 may have been achieved by the direct modulation of microglia. In conclusion, stress-induced priming of spinal microglia played a key role in the initiation of preoperative stress-induced prolongation of postsurgical pain, and PHA-543613 and PNU-120596 may be potential candidates for preventing pain chronification after surgery.

Receptor variants and the development of centrally acting medications

The progressive changes in research paradigms observed in the largest pharmaceutical companies and the burgeoning of biotechnology startups over the last 10 years have generated a need for outsourcing research facilities. In parallel, progress made in the fields of genomics, protein expression in recombinant systems, and electrophysiological recording methods have offered new possibilities for the development of contract research organizations (CROs). Successful partnering between pharmaceutical companies and CROs largely depends upon the competences and scientific quality on offer for the discovery of novel active molecules and targets. Thus, it is critical to review the knowledge in the field of neuroscience research, how genetic approaches are augmenting our knowledge, and how they can be applied in the translation from the identification of potential molecules up to the first clinical trials. Taking these together, it is apparent that CROs have an important role to play in the neuroscience of drug discovery.