Challenges and opportunities for the development of new antipsychotic drugs

α2A- and α2C-adrenoceptor expression and functionality in postmortem prefrontal cortex of schizophrenia subjects

Previous evidence suggests that α₂-adrenoceptors (α₂-AR) may be involved in the pathophysiology of schizophrenia. However, postmortem brain studies on α₂-AR expression and functionality in schizophrenia are scarce. The aim of our work was to evaluate α_2A-AR and α_2C-AR expression in different subcellular fractions of prefrontal cortex postmortem tissue from antipsychotic-free (absence of antipsychotics in blood at the time of death) (n = 12) and antipsychotic-treated (n = 12) subjects with schizophrenia, and matched controls (n = 24). Functional coupling of α₂-AR to G_α proteins induced by the agonist UK14304 was also tested. Additionally, G_α protein expression was also evaluated. In antipsychotic-free schizophrenia subjects, α_2A-AR and α_2C-AR protein expression was similar to controls in all the subcellular fractions. Conversely, in antipsychotic-treated schizophrenia subjects, increased α_2A-AR expression was found in synaptosomal plasma membrane and postsynaptic density (PSD) fractions (+60% and +79% vs controls, respectively) with no significant changes in α_2C-AR. [³⁵S]GTPγS SPA experiments showed a significant lower stimulation of G_αi2 and G_αi3 proteins by UK14304 in antipsychotic-treated schizophrenia subjects, whereas stimulation in antipsychotic-free schizophrenia subjects remained unchanged. G_αo protein stimulation was significantly decreased in both antipsychotic-free and antipsychotic-treated schizophrenia subjects compared to controls. Expression of G_αi3 protein did not differ between groups, whereas G_αi2 levels were increased in PSD of schizophrenia subjects, both antipsychotic-free and antipsychotic-treated. G_αo protein expression was increased in PSD of antipsychotic-treated subjects and in the presynaptic fraction of antipsychotic-free schizophrenia subjects. The present results suggest that antipsychotic treatment is able to modify in opposite directions both the protein expression and the functionality of α_2A-AR in the cortex of schizophrenia patients.

Subtyping Schizophrenia Patients Based on Patterns of Structural Brain Alterations

Schizophrenia is a complex and heterogeneous syndrome. Whether quantitative imaging biomarkers can identify discrete subgroups of patients as might be used to foster personalized medicine approaches for patient care remains unclear. Cross-sectional structural MR images of 163 never-treated first-episode schizophrenia patients (FES) and 133 chronically ill patients with midcourse schizophrenia from the Bipolar and Schizophrenia Network for Intermediate Phenotypes (B-SNIP) consortium and a total of 403 healthy controls were recruited. Morphometric measures (cortical thickness, surface area, and subcortical structures) were extracted for each subject and then the optimized subtyping results were obtained with nonsupervised cluster analysis. Three subgroups of patients defined by distinct patterns of regional cortical and subcortical morphometric features were identified in FES. A similar three subgroup pattern was identified in the independent dataset of patients from the multi-site B-SNIP consortium. Similarities of classification patterns across these two patient cohorts suggest that the 3-group typology is relatively stable over the course of illness. Cognitive functions were worse in subgroup 1 with midcourse schizophrenia than those in subgroup 3. These findings provide novel insight into distinct subgroups of patients with schizophrenia based on structural brain features. Findings of different cognitive functions among the subgroups support clinical differences in the MRI-defined illness subtypes. Regardless of clinical presentation and stage of illness, anatomic MR subgrouping biomarkers can separate neurobiologically distinct subgroups of schizophrenia patients, which represent an important and meaningful step forward in differentiating subtypes of patients for studies of illness neurobiology and potentially for clinical trials.

Main interactions of dopamine and risperidone with the dopamine D2 receptor

Psychosis is one of the psychiatric disorders that is controlled by dopaminergic drugs such as antipsychotics that have affinity for the dopamine D2 receptor (DRD2). In this investigation we perform quantum chemical calculations of two molecules [dopamine and risperidone] within a large cavity of DRD2 that represents the binding site of the receptor. Dopamine is an endogenous neurotransmitter and risperidone is a second-generation antipsychotic. Non-covalent interactions of dopamine and risperidone with DRD2 are analyzed using the Quantum Theory of Atoms in Molecules (QTAIM) and the Non-Covalent Interaction index (NCI). The QTAIM results show that these molecules strongly interact with the receptor. There are 22 non-covalent interactions for dopamine and 54 for risperidone. The electron density evaluated at each critical binding point is small in both systems but it is higher for dopamine than for risperidone, indicating that the interactions of DRD2 with the first are stronger than with the second molecule. However, the binding energy is higher for risperidone (-72.6 kcal mol-1) than for dopamine (-22.8 kcal mol-1). Thus, the strength of the binding energy is due to the number of contacts rather than the strength of the interactions themselves. This could be related to the ability of risperidone to block DRD2 and may explain the efficacy of this drug for controlling the symptoms of schizophrenia, but likewise its secondary effects.

New information of dopaminergic agents based on quantum chemistry calculations

Dopamine is an important neurotransmitter that plays a key role in a wide range of both locomotive and cognitive functions in humans. Disturbances on the dopaminergic system cause, among others, psychosis, Parkinson's disease and Huntington's disease. Antipsychotics are drugs that interact primarily with the dopamine receptors and are thus important for the control of psychosis and related disorders. These drugs function as agonists or antagonists and are classified as such in the literature. However, there is still much to learn about the underlying mechanism of action of these drugs. The goal of this investigation is to analyze the intrinsic chemical reactivity, more specifically, the electron donor-acceptor capacity of 217 molecules used as dopaminergic substances, particularly focusing on drugs used to treat psychosis. We analyzed 86 molecules categorized as agonists and 131 molecules classified as antagonists, applying Density Functional Theory calculations. Results show that most of the agonists are electron donors, as is dopamine, whereas most of the antagonists are electron acceptors. Therefore, a new characterization based on the electron transfer capacity is proposed in this study. This new classification can guide the clinical decision-making process based on the physiopathological knowledge of the dopaminergic diseases.

In silico hippocampal modeling for multi-target pharmacotherapy in schizophrenia

Treatment of schizophrenia has had limited success in treating core cognitive symptoms. The evidence of multi-gene involvement suggests that multi-target therapy may be needed. Meanwhile, the complexity of schizophrenia pathophysiology and psychopathology, coupled with the species-specificity of much of the symptomatology, places limits on analysis via animal models, in vitro assays, and patient assessment. Multiscale computer modeling complements these traditional modes of study. Using a hippocampal CA3 computer model with 1200 neurons, we examined the effects of alterations in NMDAR, HCN (Ih current), and GABAAR on information flow (measured with normalized transfer entropy), and in gamma activity in local field potential (LFP). We found that altering NMDARs, GABAAR, Ih, individually or in combination, modified information flow in an inverted-U shape manner, with information flow reduced at low and high levels of these parameters. Theta-gamma phase-amplitude coupling also had an inverted-U shape relationship with NMDAR augmentation. The strong information flow was associated with an intermediate level of synchrony, seen as an intermediate level of gamma activity in the LFP, and an intermediate level of pyramidal cell excitability. Our results are consistent with the idea that overly low or high gamma power is associated with pathological information flow and information processing. These data suggest the need for careful titration of schizophrenia pharmacotherapy to avoid extremes that alter information flow in different ways. These results also identify gamma power as a potential biomarker for monitoring pathology and multi-target pharmacotherapy.

Influence of More Than 5 Years of Continuous Exposure to Antipsychotics on Cerebral Functional Connectivity of Chronic Schizophrenia

OBJECTIVE

To explore the effect of long-term antipsychotics use on the strength of functional connectivity (FC) in the brains of patients with chronic schizophrenia.

METHOD

We collected resting-state functional magnetic resonance imaging from 15 patients with continuously treated chronic schizophrenia (TCS), 19 patients with minimally TCS (MTCS), and 20 healthy controls (HCs). Then, we evaluated and compared the whole-brain FC strength (FCS; including full-range, short-range, and long-range FCS) among patients with TCS, MTCS, and HCs.

RESULTS

Patients with TCS and MTCS showed reduced full-/short-range FC compared with the HCs. No significant differences in the whole-brain FCS (including full-range, short-range, and long-range FCS) or clinical characteristics were identified between patients with TCS and MTCS. Additionally, the FCS in the right fusiform gyrus, right inferior temporal gyrus, and right inferior occipital gyrus negatively correlated with the duration of illness and positively correlated with onset age across all patients with chronic schizophrenia.

CONCLUSIONS

Regardless of the long-term use of antipsychotics, patients with chronic schizophrenia show decreased FC compared with healthy individuals. For some patients with chronic schizophrenia, the influence of long-term and minimal/short-term antipsychotic exposure on resting-state FC was similar. The decreased full- and short-range FCS in the right fusiform gyrus, right inferior temporal gyrus, and right inferior occipital gyrus may be an ongoing pathological process that is not altered by antipsychotic interventions in patients with chronic schizophrenia. Large-sample, long-term follow-up studies are still needed for further exploration.

Antipsychotic-like effects of a novel phosphodiesterase 10A inhibitor MT-3014 in rats

Phosphodiesterase (PDE) 10A is an attractive therapeutic target for schizophrenia. Here, we investigated the antipsychotic-like effects of a novel PDE10A inhibitor, 1-({2-(7-fluoro-3-methylquinoxalin-2-yl)-5-[(3R)-3-fluoropyrrolidin-1-yl]pyrazolo[1,5-α]pyrimidin-7-yl}amino)-2-methylpropan-2-ol hydrochloride (MT-3014) in rats. MT-3014 showed a potent and selective inhibitory effect against PDE10A (IC₅₀ = 0.357 nmol/L). Oral administration of MT-3014 (1.0-10 mg/kg) significantly increased the levels of cAMP, cGMP and cAMP response element-binding protein (CREB) phosphorylation in the rat striatum. MT-3014 decreased MK-801 (0.075 mg/kg)-induced hyperactivity (ED₅₀ = 0.30 mg/kg) in a dose-dependent manner, although it decreased spontaneous locomotion in control rats (ED₅₀ = 0.48 mg/kg); its effects were equivalent to those of risperidone. MT-3014 (0.3-3.0 mg/kg and 0.2 mg/kg) attenuated MK-801-induced prepulse inhibition deficits and cognitive deficits in rats, respectively, whereas risperidone attenuated MK-801-induced prepulse inhibition at only a high dose and failed to improve MK-801-induced cognitive deficits. Similar to risperidone (ID₅₀ = 0.63 mg/kg), MT-3014 suppressed the conditioned avoidance response (ID₅₀ = 0.32 mg/kg). Interestingly, MT-3014 did not elicit catalepsy and plasma prolactin increases at high doses. Furthermore, it also did not affect body weight. A positron emission tomography study using [¹¹C]IMA107 showed a plasma concentration-dependent increase in brain PDE10A occupancy after oral administration of MT-3014 within the pharmacological dose range in rats. Brain PDE10A occupancy corresponding to the ID₅₀ value in the conditioned avoidance response was approximately 60%, predicting the target occupancy in patients with schizophrenia. These results suggest that MT-3014 may be a novel antipsychotic drug, which is expected to have additional effects on cognitive impairment, without the prominent side effects associated with current atypical antipsychotics.

Do rat auditory event related potentials exhibit human mismatch negativity attributes related to predictive coding?

Rodent models play a significant role in understanding disease mechanisms and the screening of new treatments. With regard to psychiatric disorders such as schizophrenia, however, it is difficult to replicate the human symptoms in rodents because these symptoms are often either 'uniquely human' or are only conveyed via self-report. There is a growing interest in rodent mismatch responses (MMRs) as a translatable 'biomarker' for disorders such as schizophrenia. In this review, we will summarize the attributes of human MMN, and discuss the scope of exploring the attributes of human MMN in rodents. Here, we examine how reliably MMRs that are measured in rats mimic human attributes, and present original data examining whether manipulations of stimulus conditions known to modulate human MMN, do the same for rat MMRs. Using surgically-implanted epidural electroencephalographic electrodes and wireless telemetry in freely-moving rats, we observed human-like modulations of MMRs, namely that larger MMRs were elicited to unexpected (deviant) stimuli that a) had a larger change in pitch compared to the expected (standard) stimulus, b) were less frequently presented (lower probability), and c) had no jitter (stable stimulus onset asynchrony) compared to high jitter. Overall, these findings contribute to the mounting evidence for rat MMRs as a good analogue of human MMN, bolstering the development of a novel approach in future to validate the preclinical models based on a translatable biomarker, MMN.

A quantum chemical approach representing a new perspective concerning agonist and antagonist drugs in the context of schizophrenia and Parkinson's disease

Schizophrenia and Parkinson’s disease can be controlled with dopamine antagonists and agonists. In order to improve the understanding of the reaction mechanism of these drugs, in this investigation we present a quantum chemical study of 20 antagonists and 10 agonists. Electron donor acceptor capacity and global hardness are analyzed using Density Functional Theory calculations. Following this theoretical approach, we provide new insights into the intrinsic response of these chemical species. In summary, antagonists generally prove to be better electron acceptors and worse electron donors than dopamine, whereas agonists present an electron donor-acceptor capacity similar to that of dopamine. The chemical hardness is a descriptor that captures the resistance of a chemical compound to change its number of electrons. Within this model, harder molecules are less polarizable and more stable systems. Our results show that the global hardness is similar for dopamine and agonists whilst antagonists present smaller values. Following the Hard and Soft Acid and Bases principle, it is possible to conclude that dopamine and agonists are hard bases while antagonists are soft acids, and this can be related to their activity. From the electronic point of view, we have evolved a new perspective for the classification of agonist and antagonist, which may help to analyze future results of chemical interactions triggered by these drugs.

Dendritic structural plasticity and neuropsychiatric disease

The structure of neuronal circuits that subserve cognitive functions in the brain is shaped and refined throughout development and into adulthood. Evidence from human and animal studies suggests that the cellular and synaptic substrates of these circuits are atypical in neuropsychiatric disorders, indicating that altered structural plasticity may be an important part of the disease biology. Advances in genetics have redefined our understanding of neuropsychiatric disorders and have revealed a spectrum of risk factors that impact pathways known to influence structural plasticity. In this Review, we discuss the importance of recent genetic findings on the different mechanisms of structural plasticity and propose that these converge on shared pathways that can be targeted with novel therapeutics.

Antipsychotic-like effects of a novel phosphodiesterase 10A inhibitor T-251 in rodents

Phosphodiesterase 10A (PDE10A) is a dual-substrate PDE that hydrolyzes both cAMP and cGMP. PDE10A is selectively expressed in medium spiny neurons in the striatum, suggesting the potential of PDE10A inhibitors in the treatment of schizophrenia. This study presents the pharmacological profile of a novel PDE10A inhibitor, 2-[(E)-2-(7-fluoro-3-methylquinoxalin-2-yl)vinyl]-6-pyrrolidin-1-yl-N-(tetrahydro-2H-pyran-4-yl)pyrimidin-4-amine hydrochloride (T-251) in rodent models of schizophrenia. T-251 showed a potent inhibitory activity against human PDE10A (IC₅₀ = 0.050 nmol/L) and showed high selectivity over other PDE families which have over 10,000-fold IC₅₀ values. Oral administration of T-251 (0.1-1.0 mg/kg) increased cAMP and cGMP in the striatum in a dose-dependent manner. Oral administration of T-251 attenuated MK-801 induced hyperactivity (ED₅₀ = 0.68 mg/kg) and suppressed conditioned avoidance response (ID₅₀ = 0.87 mg/kg) in rats in a dose dependent manner. Furthermore, T-251 significantly attenuated MK-801 induced prepulse inhibition deficits and cognitive deficits in rats. Unlike haloperidol and olanzapine, T-251 (1.0-30 mg/kg) did not cause catalepsy in rats. Moreover, T-251 (0.6 and 6.0 mg/kg) did not increase plasma levels of prolactin at 1 h after administration, whereas haloperidol and olanzapine significantly increased them. The antipsychotic-like effects and cognitive enhancement of T-251 without catalepsy or plasma prolactin elevation observed in rats suggests that T-251 would be a novel antipsychotic with an improved side-effect profile.

Scalable Measurements of Intrinsic Excitability in Human iPS Cell-Derived Excitatory Neurons Using All-Optical Electrophysiology

Induced pluripotent stem (iPS) cells offer the exciting opportunity for modeling neurological disorders in vitro in the context of a human genetic background. While significant progress has been made in advancing the use of iPS cell-based disease models, there remains an unmet need to characterize the electrophysiological profile of individual neurons with sufficient throughput to enable statistically robust assessment of disease phenotypes and pharmacological modulation. Here, we describe the Optopatch platform technology that utilizes optogenetics to both stimulate and record action potentials (APs) from human iPS cell-derived excitatory neurons with similar information content to manual patch clamp electrophysiology, but with ~  3 orders of magnitude greater throughput. Cortical excitatory neurons were produced using the NGN2 transcriptional programming approach and cultured in the presence of rodent glial cells. Characterization of the neuronal preparations using immunocytochemistry and qRT-PCR assays reveals an enrichment of neuronal and glutamatergic markers as well as select ion channels. We demonstrate the scale of our intrinsic cellular excitability assay using pharmacological assessment with select ion channel modulators quinidine and retigabine, by measuring changes in both spike timing and waveform properties. The Optopatch platform in human iPS cell-derived cortical excitatory neurons has the potential for detailed phenotype and pharmacology evaluation, which can serve as the basis of cellular disease model exploration for drug discovery and phenotypic screening efforts.

PET neuroimaging reveals histone deacetylase dysregulation in schizophrenia

BACKGROUND

Patients with schizophrenia (SCZ) experience chronic cognitive deficits. Histone deacetylases (HDACs) are enzymes that regulate cognitive circuitry; however, the role of HDACs in cognitive disorders, including SCZ, remains unknown in humans. We previously determined that HDAC2 mRNA levels were lower in dorsolateral prefrontal cortex (DLPFC) tissue from donors with SCZ compared with controls. Here we investigated the relationship between in vivo HDAC expression and cognitive impairment in patients with SCZ and matched healthy controls using [11C]Martinostat positron emission tomography (PET).

METHODS

In a case-control study, relative [11C]Martinostat uptake was compared between 14 patients with SCZ or schizoaffective disorder (SCZ/SAD) and 17 controls using hypothesis-driven region-of-interest analysis and unbiased whole brain voxel-wise approaches. Clinical measures, including the MATRICS consensus cognitive battery, were administered.

RESULTS

Relative HDAC expression was lower in the DLPFC of patients with SCZ/SAD compared with controls, and HDAC expression positively correlated with cognitive performance scores across groups. Patients with SCZ/SAD also showed lower relative HDAC expression in the dorsomedial prefrontal cortex and orbitofrontal gyrus, and higher relative HDAC expression in the cerebral white matter, pons, and cerebellum compared with controls.

CONCLUSIONS

These findings provide in vivo evidence of HDAC dysregulation in patients with SCZ and suggest that altered HDAC expression may impact cognitive function in humans.

FUNDING

National Institute of Mental Health (NIMH), Brain and Behavior Foundation, Massachusetts General Hospital (MGH), Athinoula A. Martinos Center for Biomedical Imaging, National Institute of Biomedical Imaging and Bioengineering (NIBIB), NIH Shared Instrumentation Grant Program.

Pharmacological interventions in social cognition deficits: A systematic mapping review

Social cognition is an important research field in psychiatry due to its relevance in the functioning and quality of life of patients. The objective of this work is to conduct a systematic mapping review of pharmacological strategies for improving social cognition deficits. Publications from 2006 to 2016 were reviewed in Scopus, PsycINFO, PubMed, and Embase. From the initial 1059 publications obtained, a final number of 110 were selected. The results show an increasing interest in pharmacological approaches in different medical fields (especially psychiatry, pharmacology, and endocrinology, with schizophrenia and autism as the most studied disorders), as can be observed in the progressive increase in the number of publications, the high degree of scientific evidence, and the high impact factor of publications. However, it is also observed that most studies were conducted with oxytocin, psychostimulants, and antipsychotics (mainly risperidone and olanzapine), with few studies using other drugs. In the different social cognition domains, the majority of publications were focused on emotional processing or theory of mind, with few studies in other domains. Thus, this systematic mapping review shows that, even though there are increasing research activities, there are some important gaps to cover in future investigation.

Aminobenzisoxazole compounds as agonists of α7 nicotinic acetylcholine receptors: a patent evaluation (WO 2017027600)

INTRODUCTION

alpha 7 subtype nicotinic acetylcholine receptor (α7 nAChR) ligands, that is, ligands that interact with the orthosteric or allosteric binding sites of α7 nAChR, hold great potential for several therapeutic applications. Numerous compounds have been designed targeting α7 nAChR but most of them cannot be used therapeutically for various reasons. Areas covered: The patent application describes a series of germinal substituted aminobenzisoxazole compounds as α7 nAChR ligands. These compounds were claimed as potential therapeutics for treating and/or improving cognitive function. All of the (R)-stereoisomer presented high binding activities for α7 nAChR and several compounds displayed excellent selectivity over 5-HT₃R. Expert opinion: The privileged structure-derived modification via bioisosterism and scaffold hopping is an important approach for seeking novel α7 nAChR ligands. The claimed germinal substituted aminobenzisoxazole derivatives with low tPSA values as well as low number of hydrogen bond donors and acceptors are supposed to have sufficient BBB penetration. Although there is a lack of essential biological data and the molecular mechanisms are not clear, these compounds stand for a new type of α7 nAChR ligands and deserve further studies.

Quantifying the treatment goals of people recently diagnosed with schizophrenia using best-worst scaling

OBJECTIVE

This study seeks to quantify the treatment goals of people recently diagnosed with schizophrenia and explore their impact on treatment plan.

METHODS

People aged 18-35 years with a confirmed diagnosis of schizophrenia within the past 5 years were surveyed in the UK, Germany, and Italy. Treatment goals were assessed via a validated best-worst scaling instrument, where participants evaluated subsets of 13 possible treatment goals identified using a balanced incomplete block design. Participants identified the most and least important goals within each task. Data were also collected on current treatment and preference for daily oral versus long-acting injectable (LAI) treatment. Hierarchical Bayes was used to identify preference weights for the goals, and latent class analysis was used to identify segments of people with similar goals. The segments were compared with the current treatment and preference for oral versus LAI treatment.

RESULTS

Across 100 participants, the average age was 26 years, 75% were male and 50% were diagnosed within 2 years ago. Overall, preferences were most favorable for reduced disease symptoms, think clearly, reduced hospitalizations, reduced anxiety, and take care of self. A total of 61% preferred oral medication and 39% LAI. Two groups were identified with different treatment goals; 50% of participants emphasized clinical goals, including reduced disease symptoms (preference weight =19.7%), reduced hospitalizations (15.5%), and reduced anxiety (10.5%). The other 50% emphasized functional goals, including improved relationships with family/friends (11.4%), increased interest in work (10.6%), experiencing a fuller range of emotions (8.4%), and ability to socialize (7.5%). Those emphasizing functional goals were more likely to be on LAI (44% versus 26%; p=0.059) and preferred LAI (46% versus 32%; p=0.151).

CONCLUSIONS

People with recent-onset schizophrenia may focus more on clinical goals or functional goals, a discussion of which may help facilitate patient engagement.