Pharmacology of basimglurant (RO4917523, RG7090), a unique metabotropic glutamate receptor 5 negative allosteric modulator in clinical development for depression.

Major depressive disorder (MDD) is a serious public health burden and a leading cause of disability. Its pharmacotherapy is currently limited to modulators of monoamine neurotransmitters and second-generation antipsychotics. Recently, glutamatergic approaches for the treatment of MDD have increasingly received attention, and preclinical research suggests that metabotropic glutamate receptor 5 (mGlu5) inhibitors have antidepressant-like properties. Basimglurant (2-chloro-4-[1-(4-fluoro-phenyl)-2,5-dimethyl-1H-imidazol-4-ylethynyl]-pyridine) is a novel mGlu5 negative allosteric modulator currently in phase 2 clinical development for MDD and fragile X syndrome. Here, the comprehensive preclinical pharmacological profile of basimglurant is presented with a focus on its therapeutic potential for MDD and drug-like properties. Basimglurant is a potent, selective, and safe mGlu5 inhibitor with good oral bioavailability and long half-life supportive of once-daily administration, good brain penetration, and high in vivo potency. It has antidepressant properties that are corroborated by its functional magnetic imaging profile as well as anxiolytic-like and antinociceptive features. In electroencephalography recordings, basimglurant shows wake-promoting effects followed by increased delta power during subsequent non-rapid eye movement sleep. In microdialysis studies, basimglurant had no effect on monoamine transmitter levels in the frontal cortex or nucleus accumbens except for a moderate increase of accumbal dopamine, which is in line with its lack of pharmacological activity on monoamine reuptake transporters. These data taken together, basimglurant has favorable drug-like properties, a differentiated molecular mechanism of action, and antidepressant-like features that suggest the possibility of also addressing important comorbidities of MDD including anxiety and pain as well as daytime sleepiness and apathy or lethargy.

European clinical network: autism spectrum disorder assessments and patient characterisation.

The United Nations and World Health Organisation have identified autism spectrum disorder (ASD) as an important public health issue across global mental health services. Although a range of tools exist to identify and quantify ASD symptoms, there is a lack of information about which ASD measures are used in different services worldwide. This paper presents data from a large survey of measures used for patient characterisation in major ASD research and clinical centres across Europe collected between June 2013 and January 2014. The objective was to map the use of different instruments used to characterise ASD, comorbid psychopathology and cognitive and adaptive ability for patient diagnostic and characterisation purposes across Europe. Sixty-six clinical research sites diagnosing 14,844 patients per year contributed data. The majority of sites use the well-established Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview (ADI) instruments, though the proportion of sites in Western Europe using the ADI was almost double the rate in Eastern Europe. Approximately half the sites also used the Social Communication Questionnaire (SCQ) and Social Responsiveness Scale (SRS), although use of the SRS was over three times higher in Western Europe compared with Eastern Europe. The use of free/open access measures was lower than commercially available tools across all regions. There are clinical and scientific benefits in encouraging further convergence of clinical characterisation measures across ASD research and clinical centres in Europe to facilitate large-scale data sharing and collaboration, including clinical trials of novel medications and psychological interventions.

Differential effects of diazepam and MPEP on habituation and neuro-behavioural processes in inbred mice.

BACKGROUND: Previous studies have demonstrated a profound lack of habituation in 129P3 mice compared to the habituating, but initially more anxious, BALB/c mice. The present study investigated whether this non-adaptive phenotype of 129P3 mice is primarily based on anxiety-related characteristics. METHODS: To test this hypothesis and extend our knowledge on the behavioural profile of 129P3 mice, the effects of the anxiolyticdiazepam (1, 3 and 5 mg/kg) and the putative anxiolytic metabotropic glutamate receptor 5 (mGlu5R) antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP, 3, 10 and 30 mg/kg) treatment on within-trial (intrasession) habituation, object recognition (diazepam: 1 mg/kg; MPEP 10 mg/kg) and on the central-nervous expression of the immediate early gene c-Fos (diazepam: 1 mg/kg; MPEP 10 mg/kg) were investigated. RESULTS: Behavioural findings validated the initially high, but habituating phenotype of BALB/c mice, while 129P3 mice were characterized by impaired intrasession habituation. Diazepam had an anxiolytic effect in BALB/c mice, while in higher doses caused behavioural inactivity in 129P3 mice. MPEP revealed almost no anxiolytic effects on behaviour in both strains, but reduced stress-induced corticosterone responses only in 129P3 mice. These results were complemented by reduced expression of c-Fos after MPEP treatment in brain areas related to emotional processes, and increased c-Fos expression in higher integrating brain areas such as the prelimbic cortex compared to vehicle-treated 129P3 mice. CONCLUSIONS: These results suggest that the strain differences observed in (non)adaptive anxiety behaviour are at least in part mediated by differences in gamma-aminobutyric acid- A and mGluR5 mediated transmission.

Functional improvement in mouse models of familial amyotrophic lateral sclerosis by PEGylated insulin-like growth factor I treatment depends on disease severity.

Insulin-like growth factor I (IGF-I) has been successfully tested in the SOD1-G93A mouse model of familial amyotrophic lateral sclerosis (ALS) and proposed for clinical treatment. However, beneficial effects required gene therapy or intrathecal application. Circumventing the dosing issues we recently found that polyethylene glycol (PEG) modified IGF-I (PEG-IGF-I) modulated neuromuscular function after systemic application, and protected against disease progression in a motor neuron disease model. Here we investigated its effects in two SOD1-G93A mouse lines, the G1L with a milder and the G1H with a more severe phenotype. Results showed that in G1L mice, PEG-IGF-I treatment significantly improved muscle force, motor coordination and animal survival. In contrast, treatment of G1H mice with PEG-IGF-I or IGF-I even at high doses did not beneficially affect survival or functional outcomes despite increased signalling in brain and spinal cord by both agents. In conclusion, the data point towards further investigation of the therapeutic potential of PEG-IGF-I in ALS patients with less severe clinical phenotypes.

Interindividual Differences in Cortical Thickness and Their Genomic Underpinnings in Autism Spectrum Disorder.

OBJECTIVE: Autism spectrum disorder (ASD) is accompanied by highly individualized neuroanatomical deviations that potentially map onto distinct genotypes and clinical phenotypes. This study aimed to link differences in brain anatomy to specific biological pathways to pave the way toward targeted therapeutic interventions. METHODS: The authors examined neurodevelopmental differences in cortical thickness and their genomic underpinnings in a large and clinically diverse sample of 360 individuals with ASD and 279 typically developing control subjects (ages 6-30 years) within the EU-AIMS Longitudinal European Autism Project (LEAP). The authors also examined neurodevelopmental differences and their potential pathophysiological mechanisms between clinical ASD subgroups that differed in the severity and pattern of sensory features. RESULTS: In addition to significant between-group differences in "core" ASD brain regions (i.e., fronto-temporal and cingulate regions), individuals with ASD manifested as neuroanatomical outliers within the neurotypical cortical thickness range in a wider neural system, which was enriched for genes known to be implicated in ASD on the genetic and/or transcriptomic level. Within these regions, the individuals' total (i.e., accumulated) degree of neuroanatomical atypicality was significantly correlated with higher polygenic scores for ASD and other psychiatric conditions, and it scaled with measures of symptom severity. Differences in cortical thickness deviations were also associated with distinct sensory subgroups, especially in brain regions expressing genes involved in excitatory rather than inhibitory neurotransmission. CONCLUSIONS: The study findings corroborate the link between macroscopic differences in brain anatomy and the molecular mechanisms underpinning heterogeneity in ASD, and provide future targets for stratification and subtyping.

CTEP: a novel, potent, long-acting, and orally bioavailable metabotropic glutamate receptor 5 inhibitor.

The metabotropic glutamate receptor 5 (mGlu5) is a glutamate-activated class C G protein-coupled receptor widely expressed in the central nervous system and clinically investigated as a drug target for a range of indications, including depression, Parkinson's disease, and fragile X syndrome. Here, we present the novel potent, selective, and orally bioavailable mGlu5 negative allosteric modulator with inverse agonist properties 2-chloro-4-((2,5-dimethyl-1-(4-(trifluoromethoxy)phenyl)-1H-imidazol-4-yl)ethynyl)pyridine (CTEP). CTEP binds mGlu5 with low nanomolar affinity and shows >1000-fold selectivity when tested against 103 targets, including all known mGlu receptors. CTEP penetrates the brain with a brain/plasma ratio of 2.6 and displaces the tracer [(3)H]3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone-O-methyl-oxime (ABP688) in vivo in mice from brain regions expressing mGlu5 with an average ED(50) equivalent to a drug concentration of 77.5 ng/g in brain tissue. This novel mGlu5 inhibitor is active in the stress-induced hyperthermia procedure in mice and the Vogel conflict drinking test in rats with minimal effective doses of 0.1 and 0.3 mg/kg, respectively, reflecting a 30- to 100-fold higher in vivo potency compared with 2-methyl-6-(phenylethynyl)pyridine (MPEP) and fenobam. CTEP is the first reported mGlu5 inhibitor with both long half-life of approximately 18 h and high oral bioavailability allowing chronic treatment with continuous receptor blockade with one dose every 48 h in adult and newborn animals. By enabling long-term treatment through a wide age range, CTEP allows the exploration of the full therapeutic potential of mGlu5 inhibitors for indications requiring chronic receptor inhibition.

Imbalanced social-communicative and restricted repetitive behavior subtypes of autism spectrum disorder exhibit different neural circuitry.

Social-communication (SC) and restricted repetitive behaviors (RRB) are autism diagnostic symptom domains. SC and RRB severity can markedly differ within and between individuals and may be underpinned by different neural circuitry and genetic mechanisms. Modeling SC-RRB balance could help identify how neural circuitry and genetic mechanisms map onto such phenotypic heterogeneity. Here, we developed a phenotypic stratification model that makes highly accurate (97-99%) out-of-sample SC = RRB, SC > RRB, and RRB > SC subtype predictions. Applying this model to resting state fMRI data from the EU-AIMS LEAP dataset (n = 509), we find that while the phenotypic subtypes share many commonalities in terms of intrinsic functional connectivity, they also show replicable differences within some networks compared to a typically-developing group (TD). Specifically, the somatomotor network is hypoconnected with perisylvian circuitry in SC > RRB and visual association circuitry in SC = RRB. The SC = RRB subtype show hyperconnectivity between medial motor and anterior salience circuitry. Genes that are highly expressed within these networks show a differential enrichment pattern with known autism-associated genes, indicating that such circuits are affected by differing autism-associated genomic mechanisms. These results suggest that SC-RRB imbalance subtypes share many commonalities, but also express subtle differences in functional neural circuitry and the genomic underpinnings behind such circuitry.

Rational design of novel pyrrolidine derivatives as orally active neurokinin-3 receptor antagonists.

The rational design of a novel series of pyrrolidine derivatives as neurokinin-3 receptor antagonists is reported starting from a selective neurokinin-1 receptor antagonist. Typical representatives in this series showed in vivo efficacy after oral administration in a NK3 mediated functional assay. This series of NK3 antagonists shows promise to deliver a novel antipsychotic.

Discovery of potent, balanced and orally active dual NK1/NK3 receptor ligands.

During a program directed at selective NK(1) receptor antagonists, we serendipitously discovered an NK(1) receptor ligand with additional affinity for the NK(3) receptor. Recognising an opportunity for a drug discovery program aiming for dual NK(1)/NK(3) receptor antagonists, we prepared a series of analogues from a novel, versatile building block. From this series emerged compounds with high and balanced affinities for the NK(1) and the NK(3) receptors. Typical representatives of this series were active in the gerbil foot tapping assay after oral administration.

Transcriptome signatures from discordant sibling pairs reveal changes in peripheral blood immune cell composition in Autism Spectrum Disorder.

Notwithstanding several research efforts in the past years, robust and replicable molecular signatures for autism spectrum disorders from peripheral blood remain elusive. The available literature on blood transcriptome in ASD suggests that through accurate experimental design it is possible to extract important information on the disease pathophysiology at the peripheral level. Here we exploit the availability of a resource for molecular biomarkers in ASD, the Italian Autism Network (ITAN) collection, for the investigation of transcriptomic signatures in ASD based on a discordant sibling pair design. Whole blood samples from 75 discordant sibling pairs selected from the ITAN network where submitted to RNASeq analysis and data analyzed by complementary approaches. Overall, differences in gene expression between affected and unaffected siblings were small. In order to assess the contribution of differences in the relative proportion of blood cells between discordant siblings, we have applied two different cell deconvolution algorithms, showing that the observed molecular signatures mainly reflect changes in peripheral blood immune cell composition, in particular NK cells. The results obtained by the cell deconvolution approach are supported by the analysis performed by WGCNA. Our report describes the largest differential gene expression profiling in peripheral blood of ASD subjects and controls conducted by RNASeq. The observed signatures are consistent with the hypothesis of immune alterations in autism and an increased risk of developing autism in subjects exposed to prenatal infections or stress. Our study also points to a potential role of NMUR1, HMGB3, and PTPRN2 in ASD.

Social brain activation during mentalizing in a large autism cohort: the Longitudinal European Autism Project.

BACKGROUND: Autism spectrum disorder (ASD) is a neurodevelopmental condition with key deficits in social functioning. It is widely assumed that the biological underpinnings of social impairment are neurofunctional alterations in the "social brain," a neural circuitry involved in inferring the mental state of a social partner. However, previous evidence comes from small-scale studies and findings have been mixed. We therefore carried out the to-date largest study on neural correlates of mentalizing in ASD. METHODS: As part of the Longitudinal European Autism Project, we performed functional magnetic resonance imaging at six European sites in a large, well-powered, and deeply phenotyped sample of individuals with ASD (N = 205) and typically developing (TD) individuals (N = 189) aged 6 to 30 years. We presented an animated shapes task to assess and comprehensively characterize social brain activation during mentalizing. We tested for effects of age, diagnosis, and their association with symptom measures, including a continuous measure of autistic traits. RESULTS: We observed robust effects of task. Within the ASD sample, autistic traits were moderately associated with functional activation in one of the key regions of the social brain, the dorsomedial prefrontal cortex. However, there were no significant effects of diagnosis on task performance and no effects of age and diagnosis on social brain responses. Besides a lack of mean group differences, our data provide no evidence for meaningful differences in the distribution of brain response measures. Extensive control analyses suggest that the lack of case-control differences was not due to a variety of potential confounders. CONCLUSIONS: Contrary to prior reports, this large-scale study does not support the assumption that altered social brain activation during mentalizing forms a common neural marker of ASD, at least with the paradigm we employed. Yet, autistic individuals show socio-behavioral deficits. Our work therefore highlights the need to interrogate social brain function with other brain measures, such as connectivity and network-based approaches, using other paradigms, or applying complementary analysis approaches to assess individual differences in this heterogeneous condition.

Investigating the factors underlying adaptive functioning in autism in the EU-AIMS Longitudinal European Autism Project.

Individuals with autism spectrum disorder (ASD) exhibit significant impairments in adaptive functioning that impact on their ability to meet the demands of everyday life. A recurrent finding is that there is a pronounced discrepancy between level of cognitive ability and adaptive functioning, and this is particularly prominent among higher-ability individuals. However, the key clinical and demographic associations of these discrepancies remain unclear. This study included a sample of 417 children, adolescents, and adults with ASD as part of the EU-AIMS LEAP cohort. We examined how age, sex, IQ, levels of ASD symptom and autistic trait severity and psychiatric symptomatology are associated with adaptive functioning as measured by the Vineland Adaptive Behavior Scales-Second Edition and IQ-adaptive functioning discrepancies. Older age, lower IQ and higher social-communication symptoms were associated with lower adaptive functioning. Results also demonstrate that older age, higher IQ and higher social-communication symptoms are associated with greater IQ-adaptive functioning discrepancy scores. By contrast, sensory ASD symptoms, repetitive and restricted behaviors, as well as symptoms of attention deficit/hyperactivity disorder (ADHD), anxiety and depression, were not associated with adaptive functioning or IQ-adaptive functioning discrepancy scores. These findings suggest that it is the core social communication problems that define ASD that contribute to adaptive function impairments that people with ASD experience. They show for the first time that sensory symptoms, repetitive behavior and associated psychiatric symptoms do not independently contribute to adaptive function impairments. Individuals with ASD require supportive interventions across the lifespan that take account of social-communicative ASD symptom severity. Autism Res 2019, 12: 645-657. © 2019 The Authors. Autism Research published by International Society for Autism Research published by Wiley Periodicals, Inc. LAY SUMMARY: This study investigated key clinical and demographic associations of adaptive functioning impairments in individuals with autism. We found that older age, lower IQ and more severe social-communicative symptoms, but not sensory or repetitive symptoms or co-occurring psychiatric symptoms, are associated with lower adaptive functioning and greater ability-adaptive function discrepancies. This suggests that interventions targeting adaptive skills acquisition should be flexible in their timing and intensity across developmental periods, levels of cognitive ability and take account of social-communicative ASD symptom severity.

Reproducibility via coordinated standardization: a multi-center study in a Shank2 genetic rat model for Autism Spectrum Disorders.

Inconsistent findings between laboratories are hampering scientific progress and are of increasing public concern. Differences in laboratory environment is a known factor contributing to poor reproducibility of findings between research sites, and well-controlled multisite efforts are an important next step to identify the relevant factors needed to reduce variation in study outcome between laboratories. Through harmonization of apparatus, test protocol, and aligned and non-aligned environmental variables, the present study shows that behavioral pharmacological responses in Shank2 knockout (KO) rats, a model of synaptic dysfunction relevant to autism spectrum disorders, were highly replicable across three research centers. All three sites reliably observed a hyperactive and repetitive behavioral phenotype in KO rats compared to their wild-type littermates as well as a dose-dependent phenotype attenuation following acute injections of a selective mGluR1 antagonist. These results show that reproducibility in preclinical studies can be obtained and emphasizes the need for high quality and rigorous methodologies in scientific research. Considering the observed external validity, the present study also suggests mGluR1 as potential target for the treatment of autism spectrum disorders.

Altered Connectivity Between Cerebellum, Visual, and Sensory-Motor Networks in Autism Spectrum Disorder: Results from the EU-AIMS Longitudinal European Autism Project.

BACKGROUND: Resting-state functional magnetic resonance imaging-based studies on functional connectivity in autism spectrum disorder (ASD) have generated inconsistent results. Interpretation of findings is further hampered by small samples and a focus on a limited number of networks, with networks underlying sensory processing being largely underexamined. We aimed to comprehensively characterize ASD-related alterations within and between 20 well-characterized resting-state networks using baseline data from the EU-AIMS (European Autism Interventions-A Multicentre Study for Developing New Medications) Longitudinal European Autism Project. METHODS: Resting-state functional magnetic resonance imaging data was available for 265 individuals with ASD (7.5-30.3 years; 73.2% male) and 218 typically developing individuals (6.9-29.8 years; 64.2% male), all with IQ > 70. We compared functional connectivity within 20 networks-obtained using independent component analysis-between the ASD and typically developing groups, and related functional connectivity within these networks to continuous (overall) autism trait severity scores derived from the Social Responsiveness Scale Second Edition across all participants. Furthermore, we investigated case-control differences and autism trait-related alterations in between-network connectivity. RESULTS: Higher autism traits were associated with increased connectivity within salience, medial motor, and orbitofrontal networks. However, we did not replicate previously reported case-control differences within these networks. The between-network analysis did reveal case-control differences showing on average 1) decreased connectivity of the visual association network with somatosensory, medial, and lateral motor networks, and 2) increased connectivity of the cerebellum with these sensory and motor networks in ASD compared with typically developing subjects. CONCLUSIONS: We demonstrate ASD-related alterations in within- and between-network connectivity. The between-network alterations broadly affect connectivity between cerebellum, visual, and sensory-motor networks, potentially underlying impairments in multisensory and visual-motor integration frequently observed in ASD.

Patients with autism spectrum disorders display reproducible functional connectivity alterations.

Despite the high clinical burden, little is known about pathophysiology underlying autism spectrum disorder (ASD). Recent resting-state functional magnetic resonance imaging (rs-fMRI) studies have found atypical synchronization of brain activity in ASD. However, no consensus has been reached on the nature and clinical relevance of these alterations. Here, we addressed these questions in four large ASD cohorts. Using rs-fMRI, we identified functional connectivity alterations associated with ASD. We tested for associations of these imaging phenotypes with clinical and demographic factors such as age, sex, medication status, and clinical symptom severity. Our results showed reproducible patterns of ASD-associated functional hyper- and hypoconnectivity. Hypoconnectivity was primarily restricted to sensory-motor regions, whereas hyperconnectivity hubs were predominately located in prefrontal and parietal cortices. Shifts in cortico-cortical between-network connectivity from outside to within the identified regions were shown to be a key driver of these abnormalities. This reproducible pathophysiological phenotype was partially associated with core ASD symptoms related to communication and daily living skills and was not affected by age, sex, or medication status. Although the large effect sizes in standardized cohorts are encouraging with respect to potential application as a treatment and for patient stratification, the moderate link to clinical symptoms and the large overlap with healthy controls currently limit the usability of identified alterations as diagnostic or efficacy readout.

Me-talnetant and osanetant interact within overlapping but not identical binding pockets in the human tachykinin neurokinin 3 receptor transmembrane domains.

Recent clinical trials have indicated that neurokinin 3 receptor antagonists (S)-(+)-N-{{3-[1-benzoyl-3-(3,4-dichlorophenyl)-piperidin-3-yl]prop-1-yl}-4-phenylpiperidin-4-yl}-N-methylacetamine (SR142801; osanetant) and (S)-(-)-N-(alpha-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-carboxamide (SB223412; talnetant) may treat symptoms of schizophrenia. Using site-directed mutagenesis, rhodopsin-based modeling, [(3)H](S)-(-)-N-(alpha-ethylbenzyl)-3-methoxy-2-phenylquinoline-4-carboxamide (Me-talnetant) and [(3)H]osanetant binding, and functional Schild analyses, we have demonstrated the important molecular determinants of neurokinin B (NKB), Me-talnetant, and osanetant binding pockets. The residues Asn138(2.57), Asn142(2.61), Leu232(45.49), Tyr315(6.51), Phe342(7.39), and Met346(7.43) were found to be crucial for the NKB binding site. We observed that the M134(2.53)A, V169(3.36)M, F342(7.39)M, and S341(7.38)I/F342(7.39)M mutations resulted in the complete loss of [(3)H]Metalnetant and [(3)H]osanetant binding affinities and also abolished their functional potencies in an NKB-evoked accumulation of [(3)H]inositol phosphates assay, whereas the mutations V95(1.42)A, N142(2.61)A, Y315(6.51)F, and M346(7.43)A behaved differently between the interacting modes of two antagonists. V95(1.42)A and M346(7.43)A significantly decreased the affinity and potency of Me-talnetant. Y315(6.51)F, although not affecting Me-talnetant, led to a significant decrease in affinity and potency of osanetant. The mutation N142(2.61)A, which abolished the potency and affinity of osanetant, led to a significant increase in the affinity and potency of Me-talnetant. The proposed docking mode was further validated using (S)-2-(3,5-bis-trifluoromethyl-phenyl)-N-[4-(4-fluoro-2-methyl-phenyl)-6-((S)-4-methanesulfonyl-3-methyl-piperazin-1-yl)-pyridin-3-yl]-N-methyl-isobutyramide (RO49085940), from another chemical class. It is noteworthy that the mutation F342(7.39)A caused an 80-fold gain of RO4908594 binding affinity, but the same mutation resulted in the complete loss of the affinity of Me-talnetant and partial loss of the affinity of osanetant. These observations show that the binding pocket of Me-talnetant and osanetant are overlapping, but not identical. Taken together, our data are consistent with the proposed docking modes where Me-talnetant reaches deeply into the pocket formed by transmembrane (TM)1, -2, and -7, whereas osanetant fills the pocket TM3, -5, and -6 with its phenyl-piperidine moiety.

mGluR5 antagonists: discovery, characterization and drug development.

Disturbances of glutamate-mediated neurotransmission have been implicated in a broad range of nervous system disorders. Numerous attempts to correct nervous system dysfunction by pharmacological intervention at glutamate receptors have been made, and some of the approaches have achieved a high level of preclinical validation. However, in a number of cases involving agents acting as blockers of the ionotropic glutamate receptors, clinical success could not be achieved, mostly because of the lack of a therapeutic window. The identification of the metabotropic glutamate receptor (mGluR) family and their modulatory role in the control of neurotransmission provided a new means to alter glutamatergic transmission. Furthermore, selective agents acting as allosteric antagonists at the mGluR5 subtype have demonstrated therapeutic potential. The identification and characterization of mGluR5 antagonists and recent progress in clinical development are summarized.

Opinion: NK3 receptor antagonists: the next generation of antipsychotics?

Although current antipsychotic drugs are effective at treating the psychotic (positive) symptoms of schizophrenia, they have one or more serious side effects, including extrapyramidal symptoms, weight gain, cardiovascular liabilities and type II diabetes. However, recent data from clinical trials of selective neurokinin 3 (NK(3)) receptor antagonists in schizophrenia - osanetant and talnetant - have shown significant improvement in positive symptoms, with no major side-effects reported as yet. Here we discuss the preclinical and clinical evidence that indicates that NK(3) receptor antagonists might represent a new approach to the treatment of schizophrenia and possibly other neuropsychiatric disorders.

Glutamate and GABA in autism spectrum disorder-a translational magnetic resonance spectroscopy study in man and rodent models.

Autism spectrum disorder (ASD) is a pervasive neurodevelopmental syndrome with a high human and economic burden. The pathophysiology of ASD is largely unclear, thus hampering development of pharmacological treatments for the core symptoms of the disorder. Abnormalities in glutamate and GABA signaling have been hypothesized to underlie ASD symptoms, and may form a therapeutic target, but it is not known whether these abnormalities are recapitulated in humans with ASD, as well as in rodent models of the disorder. We used translational proton magnetic resonance spectroscopy ([1H]MRS) to compare glutamate and GABA levels in adult humans with ASD and in a panel of six diverse rodent ASD models, encompassing genetic and environmental etiologies. [1H]MRS was performed in the striatum and the medial prefrontal cortex, of the humans, mice, and rats in order to allow for direct cross-species comparisons in specific cortical and subcortical brain regions implicated in ASD. In humans with ASD, glutamate concentration was reduced in the striatum and this was correlated with the severity of social symptoms. GABA levels were not altered in either brain region. The reduction in striatal glutamate was recapitulated in mice prenatally exposed to valproate, and in mice and rats carrying Nlgn3 mutations, but not in rodent ASD models with other etiologies. Our findings suggest that glutamate/GABA abnormalities in the corticostriatal circuitry may be a key pathological mechanism in ASD; and may be linked to alterations in the neuroligin-neurexin signaling complex.

EU-AIMS Longitudinal European Autism Project (LEAP): the autism twin cohort.

EU-AIMS is the largest European research program aiming to identify stratification biomarkers and novel interventions for autism spectrum disorder (ASD). Within the program, the Longitudinal European Autism Project (LEAP) has recruited and comprehensively phenotyped a rare sample of 76 monozygotic and dizygotic twins, discordant, or concordant for ASD plus 30 typically developing twins. The aim of this letter is to complete previous descriptions of the LEAP case-control sample, clinically characterize, and investigate the suitability of the sample for ASD twin-control analyses purposes and share some 'lessons learnt.' Among the twins, a diagnosis of ASD is associated with increased symptom levels of ADHD, higher rates of intellectual disability, and lower family income. For the future, we conclude that the LEAP twin cohort offers multiple options for analyses of genetic and shared and non-shared environmental factors to generate new hypotheses for the larger cohort of LEAP singletons, but particularly cross-validate and refine evidence from it.