A retrospective study of memantine in children and adolescents with pervasive developmental disorders

Emerging Treatments and Therapies for Autism Spectrum Disorder: A Narrative Review

The prevalence of autism spectrum disorder (ASD) has increased over the last decade. In this regard, many emerging therapies have been described as ASD therapies. Although ASD does not have a cure, there are several management options available that can help reduce symptom severity. ASD is highly variable and, therefore, standard treatment protocols and studies are challenging to perform. Many of these therapies also address comorbidities for which patients with ASD have an increased risk. These concurrent diagnoses can include psychiatric and neurological disorders, including attention deficit and hyperactivity disorder, anxiety disorders, and epilepsy, as well as gastrointestinal symptoms such as chronic constipation and diarrhea. Both the extensive list of ASD-associated disorders and adverse effects from commonly prescribed medications for patients with ASD can impact presenting symptomatology. It is important to keep these potential interactions in mind when considering additional drug treatments or complementary therapies. This review addresses current literature involving novel pharmacological treatments such as oxytocin, bumetanide, acetylcholinesterase inhibitors, and memantine. It also discusses additional therapies such as diet intervention, acupuncture, music therapy, melatonin, and the use of technology to aid education. Notably, several of these therapies require more long-term research to determine efficacy in specific ASD groups within this patient population.

A Pilot Feasibility Study Assessing the Combined Effects of Early Behavioral Intervention and Propranolol on Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD), a neurodevelopmental disorder typified by differences in social communication as well as restricted and repetitive behaviors, is often responsive to early behavioral intervention. However, there is limited information on whether such intervention can be augmented with pharmacological approaches. We conducted a double-blinded, placebo-controlled feasibility trial to examine the effects of the β-adrenergic antagonist propranolol combined with early intensive behavioral intervention (EIBI) for children with ASD. Nine participants with ASD, ages three to ten, undergoing EIBI were enrolled and randomized to a 12-week course of propranolol or placebo. Blinded assessments were conducted at baseline, 6 weeks, and 12 weeks. The primary outcome measures focusing on social interaction were the General Social Outcome Measure-2 (GSOM-2) and Social Responsiveness Scale-Second Edition (SRS-2). Five participants completed the 12-week visit. The sample size was insufficient to evaluate the treatment efficacy. However, side effects were infrequent, and participants were largely able to fully participate in the procedures. Conducting a larger clinical trial to investigate propranolol's effects on core ASD features within the context of behavioral therapy will be beneficial, as this will advance and individualize combined therapeutic approaches to ASD intervention. This initial study helps to understand feasibility constraints on performing such a study.

Randomized placebo-controlled crossover trial of memantine in children with epileptic encephalopathy

Memantine is an N-methyl-D-aspartate receptor antagonist, approved for dementia treatment. There is limited evidence of memantine showing benefit for paediatric neurodevelopmental phenotypes, but no randomized placebo-controlled trials in children with developmental and epileptic encephalopathy. In this randomized double-blind placebo-controlled crossover trial (Trial registration: https://clinicaltrials.gov/ct2/show/NCT03779672), patients with developmental and epileptic encephalopathy received memantine and placebo, each for a 6-week period separated by a 2-week washout phase. Electroencephalography, seizure diary, patient caregivers' global impression, serum inflammatory markers and neuropsychological evaluation were performed at baseline and after each treatment phase. The primary outcome measure was classification as a 'responder', defined as ≥2 of: >50% seizure frequency reduction, electroencephalography improvement, caregiver clinical impression improvement or clear neuropsychological testing improvement. Thirty-one patients (13 females) enrolled. Two patients withdrew prior to initiating medication and two (twins) had to be removed from analysis. Of the remaining 27 patients, nine (33%) were classified as responders to memantine versus two (7%) in the placebo group (P < 0.02). Electroencephalography improvement was seen in eight patients on memantine compared to two on placebo (P < 0.04). Seizure improvement was observed in eight patients on memantine and two on placebo (P < 0.04). Caregivers reported overall clinical improvement in 10 patients on memantine compared to seven on placebo (not significant). Statistical analysis of neuropsychological evaluation suggested improvements in symptoms of attention-deficit hyperactivity disorder and autism. Memantine is a safe and effective treatment for children with developmental and epileptic encephalopathy, having the potential to improve both seizure control and cognitive function.

The pathogenic N650K variant in the GluN1 subunit regulates the trafficking, conductance, and pharmacological properties of NMDA receptors

N-methyl-D-aspartate receptors (NMDARs) play an essential role in excitatory neurotransmission in the mammalian brain, and their physiological importance is underscored by the large number of pathogenic mutations that have been identified in the receptor's GluN subunits and associated with a wide range of diseases and disorders. Here, we characterized the functional and pharmacological effects of the pathogenic N650K variant in the GluN1 subunit, which is associated with developmental delay and seizures. Our microscopy experiments showed that when expressed in HEK293 cells (from ATCC®), the GluN1-N650K subunit increases the surface expression of both GluN1/GluN2A and GluN1/GluN2B receptors, but not GluN1/GluN3A receptors, consistent with increased surface expression of the GluN1-N650K subunit expressed in hippocampal neurons (from embryonic day 18 of Wistar rats of both sexes). Using electrophysiology, we found that the GluN1-N650K variant increases the potency of GluN1/GluN2A receptors to both glutamate and glycine but decreases the receptor's conductance and open probability. In addition, the GluN1-N650K subunit does not form functional GluN1/GluN2B receptors but does form fully functional GluN1/GluN3A receptors. Moreover, in the presence of extracellular Mg²⁺, GluN1-N650K/GluN2A receptors have a similar and increased response to ketamine and memantine, respectively, while the effect of both drugs had markedly slower onset and offset compared to wild-type GluN1/GluN2A receptors. Finally, we found that expressing the GluN1-N650K subunit in hippocampal neurons reduces excitotoxicity, and memantine shows promising neuroprotective effects in neurons expressing either wild-type GluN1 or the GluN1-N650K subunit. This study provides the functional and pharmacological characterization of NMDARs containing the GluN1-N650K variant.

Memantine as treatment for compulsivity in child and adolescent psychiatry: Descriptive findings from an incompleted randomized, double-blind, placebo-controlled trial

Background

Autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD) are mental disorders with a considerable overlap in terms of their defining symptoms. The glutamatergic agent memantine appears to be a promising candidate for the treatment of ASD and OCD in children and adolescents. The aim of this study was to investigate the clinical efficacy and tolerability/safety of memantine in this population.

Methods

This randomized, double-blind, placebo-controlled multicenter add-on trial comprised patients aged 6 to 17; 9 years with a confirmed diagnosis of ASD and/or OCD. Participants were randomized to either memantine or placebo for 10 consecutive weeks, including an up-titration phase.

Results

A total of 7 patients were included in the study. N = 4 (57.1%) participants were treated with verum (memantine) and n = 3 (42.9%) received placebo. Patients receiving memantine showed a more pronounced reduction in their CY-BOCS score, as well as greater CGI-Improvement, compared to patients receiving placebo. No serious adverse events (SAEs) were reported.

Conclusions

Our findings, although based on a very small number of patients and therefore insufficient to draw clear conclusions, appear to be in line with the hypothesis that memantine is an effective, tolerable and safe agent for children and adolescents.

Trial registration

EudraCT Number: 2014-003080-38, Registered 14 July 2014, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2014-003080-38.

Evaluation of memantine's efficacy and safety in the treatment of children with autism spectrum disorder: A systematic review and meta-analysis

BACKGROUND

The United States Food and Drug Administration has approved drugs that address only autism-related symptoms rather than the underlying impairments. N-Methyl-D-Aspartate  receptor antagonists have recently emerged as a promising treatment option for a variety of neurologic and developmental problems, including autism.

AIMS

To review (systematically), for the first time, the medical literature that explores the safety in and efficacy of memantine in autism.

METHODS AND PROCEDURES

A comprehensive electronic search for relevant randomized controlled trials was conducted in four databases. Using RevMan software, we extracted and pooled data as a risk ratio (RR) or normalized mean differences in an inverse variance strategy.

RESULTS

This systematic review and meta-analysis includes five trials. There was no difference in enhancing social responsiveness when compared to placebo, though memantine lowered the likelihood of anxiety (RR = 0.25; 95% Confidence interval: [0.07; 0.87], p = 0.03). However, memantine aggravated impulsive behaviors. Additionally, in another trial that compared memantine added to risperidone versus risperidone added to placebo, memantine was found to be effective and safe.

CONCLUSION

Memantine showed safety in reducing acute symptoms of anxiety and other symptoms encountered in pediatric patients with autism spectrum disorders. However, memantine does not improve the core symptoms of autism. Nevertheless, further long-term trials are needed to explore its potential efficacy.

Memantine for autism spectrum disorder

BACKGROUND

Autism spectrum disorder (ASD; also known as autism) is a developmental disability that begins in childhood and is typically seen in around 1% to 2% of children. It is characterised by social communication difficulties and repetitive and restricted behaviours and routines that can have a negative impact on a child's quality of life, achievement at school, and social interactions with others. It has been hypothesised that memantine, which is traditionally used to treat dementia, may be effective in reducing the core symptoms of autism as well as some co-occurring symptoms such as hyperactivity and language difficulties. If memantine is being used to treat the core symptoms of autism, it is important to review the evidence of its effectiveness.

OBJECTIVES

To assess the effects of memantine on the core symptoms of autism, including, but not limited to, social communication and stereotypical behaviours.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, nine other databases and three trials registers up to February 2022. We also checked reference lists of key studies and checked with experts in the field for any additional papers. We searched for retractions of the included studies in MEDLINE, Embase, and the Retraction Watch Database. No retractions or corrections were found.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of any dose of memantine compared with placebo in autistic people. We also included RCTs in which only one group received memantine, but both groups received the same additional therapy (e.g. a behaviour intervention).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were core autism symptoms and adverse effects. Secondary outcomes were language, intelligence, memory, adaptive behaviour, hyperactivity, and irritability. We used GRADE to assess certainty of evidence.

MAIN RESULTS

We included three RCTs (two double-blind and one single-blind) with 204 participants that examined the short-term effect (immediately postintervention) of memantine in autistic people. Two studies took place in the USA and the other in Iran. All three studies focused on children and adolescents, with a mean age of 9.40 (standard deviation (SD) 2.26) years. Most participants were male (range across studies 73% to 87%). The diagnosis of ASD was based on the Diagnostic and Statistical Manual of Mental Disorders (4th edition; 4th edition, text revision; or 5th edition). To confirm the diagnosis, one study used the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised (ADI-R); one used ADOS, ADI-R or the Autism Diagnostic Interview Screener; and one used the Gilliam Autism Rating Scale. Dosage of memantine was based on the child's weight and ranged from 3 mg to 15 mg per day.  Comparisons  Two studies examined memantine compared with placebo; in the other study, both groups had a behavioural intervention while only one group was given memantine.  Risk of bias All studies were rated at high risk of bias overall, as they were at high or unclear risk of bias across all but four domains in one study, and all but two domains in the other two studies. One study was funded by Forest Laboratories, LLC, (Jersey City, New Jersey), Allergan. The study sponsor was involved in the study design, data collection (via contracted clinical investigator sites), analysis and interpretation of data, and the decision to present these results. The other two studies reported no financial support or sponsorship; though in one of the two, the study medication was an in-kind contribution from Forest Pharmaceuticals. Primary outcomes There was no clear evidence of a difference between memantine and placebo with respect to severity of core symptoms of autism, although we are very uncertain about the evidence. The standardised mean difference in autism symptoms score in the intervention group versus the control group was -0.74 standard deviations (95% confidence interval (CI) -2.07 to 0.58; 2 studies, 181 participants; very low-certainty evidence; medium effect size); lower scores indicate less severe autistic symptoms. Two studies (144 participants) recorded adverse effects that the authors deemed related to the study and found there may be no difference between memantine and placebo (odds ratio (OR) 0.64, 95% CI 0.17 to 2.39; low-certainty evidence). Secondary outcomes There may be no difference between memantine and placebo on language (2 studies, 144 participants; low-certainty evidence); memory or adaptive behaviour (1 study, 23 participants; both low-certainty evidence); or hyperactivity or irritability (1 study, 121 participants; both low-certainty evidence).

AUTHORS' CONCLUSIONS

It is unclear whether memantine is an effective treatment for autistic children. None of the three included trials reported on the effectiveness of memantine in adults. Further studies using rigorous designs, larger samples, longer follow-up and clinically meaningful outcome measures that are important to autistic people and their families will strengthen our knowledge of the effects of memantine in autism.

Signalling pathways in autism spectrum disorder: mechanisms and therapeutic implications

Autism spectrum disorder (ASD) is a prevalent and complex neurodevelopmental disorder which has strong genetic basis. Despite the rapidly rising incidence of autism, little is known about its aetiology, risk factors, and disease progression. There are currently neither validated biomarkers for diagnostic screening nor specific medication for autism. Over the last two decades, there have been remarkable advances in genetics, with hundreds of genes identified and validated as being associated with a high risk for autism. The convergence of neuroscience methods is becoming more widely recognized for its significance in elucidating the pathological mechanisms of autism. Efforts have been devoted to exploring the behavioural functions, key pathological mechanisms and potential treatments of autism. Here, as we highlight in this review, emerging evidence shows that signal transduction molecular events are involved in pathological processes such as transcription, translation, synaptic transmission, epigenetics and immunoinflammatory responses. This involvement has important implications for the discovery of precise molecular targets for autism. Moreover, we review recent insights into the mechanisms and clinical implications of signal transduction in autism from molecular, cellular, neural circuit, and neurobehavioural aspects. Finally, the challenges and future perspectives are discussed with regard to novel strategies predicated on the biological features of autism.

Relationship Between MR Spectroscopy-Detected Glutamatergic Neurometabolites and Changes in Social Behaviors in a Pilot Open-Label Trial of Memantine for Adults With Autism Spectrum Disorder

BACKGROUND

The neurobiology underlying ASD is largely unknown but altered neural excitability/inhibitory ratios have been reported. Memantine is an N-methyl-D-aspartate (NMDA) glutamatergic antagonist studied for the treatment of core ASD symptoms, with mixed results. We examined whether glutamatergic levels were associated with and predicted response to memantine in an exploratory pilot study.

METHODS

Ten adult participants with ASD underwent proton magnetic resonance spectroscopy (¹H-MRS) imaging at baseline and behavioral assessments before and after 12-weeks of open-label memantine. Post-treatment scores on Clinical Global Impressions-Improvement (CGI-I) for social interaction were the primary outcome measure, and scores on the Social Responsiveness Scale (SRS) were included as a secondary outcome. LCModel was used to quantify the concentrations of Point RESolved Spectroscopy-detected glutamate+glutamine (Glx) (and other neurometabolites, i.e., N-acetylaspartate, NAA; creatine+phosphocreatine, Cr+PCr, and myo-inositol, Ins), within the left dorsolateral prefrontal cortex (LDLPFC) and right (R) posterolateral cerebellum. SPM was used to perform brain tissue segmentation within the spectroscopic voxels. CGI-I scores post-treatment were used to classify the participants into two groups, responders (scores 1-3; n = 5) and non-responders (scores 4-7, or withdrew due to increase behaviors; n = 5). Independent samples t-tests, partial correlations and linear hierarchical regression models (SPSS) were used to determine between-group differences in neurometabolite concentrations and associations between neurometabolites and behavioral scores.

RESULTS

Responders and non-responders did not significantly differ in Glx levels in any region of interest, but differed in NAA levels in LDLPFC (higher in responders vs. non-responders). Although changes in CGI-I social scores were not correlated with Glx in any region of interest, the linear hierarchical regression did reveal that Glx and Ins levels in LDLPFC were predictors of post-treatment CGI-I social scores. Changes in SRS scores were correlated with baseline Cr+PCr levels in the LDLPFC.

DISCUSSION

Our pilot data suggest that baseline Glx, a marker of glutamatergic neurotransmission, did not directly predict response to memantine for social outcomes in adults with ASD. However, interactions between Glx and the neurometabolite associated with glial integrity (Ins) may help predict treatment response. Further, those with highest baseline NAA, a putative neuronal marker, and Cr+pCr, a brain energy metabolism marker, were the best responders. These preliminary results may explain some of the mixed results reported in previous memantine trials in ASD. Future studies will need to examine these results in a larger sample.

Excitation/Inhibition Modulators in Autism Spectrum Disorder: Current Clinical Research

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by social and communication abnormalities. Heterogeneity in the expression and severity of the core and associated symptoms poses difficulties in classification and the overall clinical approach. Synaptic abnormalities have been observed in preclinical ASD models. They are thought to play a major role in clinical functional abnormalities and might be modified by targeted interventions. An imbalance in excitatory to inhibitory neurotransmission (E/I imbalance), through altered glutamatergic and GABAergic neurotransmission, respectively, is thought to be implicated in the pathogenesis of ASD. Glutamatergic and GABAergic agents have been tested in clinical trials with encouraging results as to efficacy and tolerability. Further studies are needed to confirm the role of E/I modulators in the treatment of ASD and on the safety and efficacy of the current agents.

Sex differences in neuronal systems function and behaviour: beyond a single diagnosis in autism spectrum disorders

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is associated with functional brain alterations that underlie the expression of behaviour. Males are diagnosed up to four times more than females, and sex differences have been identified in memory, cognitive flexibility, verbal fluency, and social communication. Unfortunately, there exists a lack of information on the sex-dependent mechanisms of ASD, as well as biological markers to distinguish sex-specific symptoms in ASD. This can often result in a standardized diagnosis for individuals across the spectrum, despite significant differences in the various ASD subtypes. Alterations in neuronal connectivity and oscillatory activity, such as is observed in ASD, are highly coupled to behavioural states. Yet, despite the well-identified sexual dimorphisms that exist in ASD, these functional patterns have rarely been analyzed in the context of sex differences or symptomology. This review summarizes alterations in neuronal oscillatory function in ASD, discusses the age, region, symptom and sex-specific differences that are currently observed across the spectrum, and potential targets for regulating neuronal oscillatory activity in ASD. The need to identify sex-specific biomarkers, in order to facilitate specific diagnostic criteria and allow for more targeted therapeutic approaches for ASD will also be discussed.

A retrospective analysis of memantine use in a pediatric neurology clinic

BACKGROUND

Memantine is an N-methyl-D-aspartate receptor (NMDA-R) antagonist, approved for dementia, but also studied in pediatric autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD).

METHODS

We reviewed children treated with memantine in a single-centre pediatric neurology clinic. Clinical data extracted included age, sex, weight, clinical history, reason for memantine prescription, period of treatment trial and dosage, treatment response, side effects, and concomitant medications.

RESULTS

Eight patients met inclusion criteria with diagnoses including developmental and epileptic encephalopathy, focal epilepsy, ASD, ADHD. Four reported clear cognitive improvement, though two of these started other concurrent treatments at the time of memantine initiation. One of three patients with poorly-controlled epilepsy, a girl with a GRIN2A variant of uncertain significance, had a clear reduction in seizure frequency. No serious adverse events were noted.

CONCLUSIONS

Memantine is generally well-tolerated in children, and may have potential benefit for a broad range of pediatric neurodevelopmental disorders.

Dendritic spine membrane proteome and its alterations in autistic spectrum disorder

Dendritic spines are small protrusions stemming from the dendritic shaft that constitute the primary specialization for receiving and processing excitatory neurotransmission in brain synapses. The disruption of dendritic spine function in several neurological and neuropsychiatric diseases leads to severe information-processing deficits with impairments in neuronal connectivity and plasticity. Spine dysregulation is usually accompanied by morphological alterations to spine shape, size and/or number that may occur at early pathophysiological stages and not necessarily be reflected in clinical manifestations. Autism spectrum disorder (ASD) is one such group of diseases involving changes in neuronal connectivity and abnormal morphology of dendritic spines on postsynaptic neurons. These alterations at the subcellular level correlate with molecular changes in the spine proteome, with alterations in the copy number, topography, or in severe cases in the phenotype of the molecular components, predominantly of those proteins involved in spine recognition and adhesion, reflected in abnormally short lifetimes of the synapse and compensatory increases in synaptic connections. Since cholinergic neurotransmission participates in the regulation of cognitive function (attention, memory, learning processes, cognitive flexibility, social interactions) brain acetylcholine receptors are likely to play an important role in the dysfunctional synapses in ASD, either directly or indirectly via the modulatory functions exerted on other neurotransmitter receptor proteins and spine-resident proteins.

Decades of Progress in the Psychopharmacology of Autism Spectrum Disorder

Recent decades have been marked by a wave drug treatment research in autism spectrum disorder (ASD). This work has resulted in improved ability to treat commonly occurring behavioral challenges associated with ASD including most prominently irritability marked by aggression, self-injurious behavior, and severe tantrums. While treatment of interfering behavior has progressed in our field, there remain several areas of unmet medical need including most prominently a lack of any approved drug therapies for the core, defining symptoms of autism. We outline the progress to date in the field of autism drug treatment while taking a future look forward into how decades of work can inform better future steps in this field.

Neurocognitive Outcomes from Memantine: A Pilot, Double-Blind, Placebo-Controlled Trial in Children with Autism Spectrum Disorder

Objective: Studies interrogating therapeutics which alter the excitation-inhibition balance in the treatment of autism spectrum disorder (ASD) have reported mixed results on social and behavioral outcomes. Methods: The aim of this randomized, double-blind placebo-controlled pilot trial was to evaluate neurocognitive effects of memantine over a 24-week trial. Twenty-three children ages 6-12 years old with ASD were randomized to memantine or placebo. Primary outcomes included measures of apraxia and expressive language with evaluations at midpoint (week 12) and endpoint (week 24). Secondary outcomes included memory and adaptive behavior measures. Exploratory outcomes included changes in overall cognitive functioning and behavior (e.g., Aberrant Behavior Checklist). Results: Results suggest that memantine was well-tolerated. Dropout rates were high across groups with only 14 participants completing the 6-month trial. Memantine was not associated with improvements in apraxia and expressive language. Treatment with memantine was associated with improvements in verbal recognition memory as measured by the Narrative Memory-Recognition (NEPSY-II) (F = 5.05, p = .03). In addition, exploratory analyses of changes in Intelligence quotient (IQ) suggest improvements on verbal IQ (d = 1.8). Conclusions: Results suggest future studies of memantine in ASD may benefit from shifting treatment targets from social and behavioral outcomes to exploration of effects of memantine on cognition, potentially as an adjunct to learning and educational interventions. ClinicalTrials.gov: NCT01372449.

Recurrent seizure-related GRIN1 variant: Molecular mechanism and targeted therapy

OBJECTIVE

Genetic variants in the GRIN genes that encode N-methyl-D-aspartate receptor (NMDAR) subunits have been identified in various neurodevelopmental disorders, including epilepsy. We identified a GRIN1 variant from an individual with early-onset epileptic encephalopathy, evaluated functional changes to NMDAR properties caused by the variant, and screened FDA-approved therapeutic compounds as potential treatments for the patient.

METHODS

Whole exome sequencing identified a missense variant in GRIN1. Electrophysiological recordings were made from Xenopus oocytes and transfected HEK cells to determine the NMDAR biophysical properties as well as the sensitivity to agonists and FDA-approved drugs that inhibit NMDARs. A beta-lactamase reporter assay in transfected HEK cells evaluated the effects of the variant on the NMDAR surface expression.

RESULTS

A recurrent de novo missense variant in GRIN1 (c.1923G>A, p.Met641Ile), which encodes the GluN1 subunit, was identified in a pediatric patient with drug-resistant seizures and early-onset epileptic encephalopathy. In vitro analysis indicates that GluN1-M641I containing NMDARs showed enhanced agonist potency and reduced Mg2+ block, which may be associated with the patient's phenotype. Results from screening FDA-approved drugs suggested that GluN1-M641I containing NMDARs are more sensitive to the NMDAR channel blockers memantine, ketamine, and dextromethorphan compared to the wild-type receptors. The addition of memantine to the seizure treatment regimen significantly reduced the patient's seizure burden.

INTERPRETATION

Our finding contributes to the understanding of the phenotype-genotype correlations of patients with GRIN1 gene variants, provides a molecular mechanism underlying the actions of this variant, and explores therapeutic strategies for treating GRIN1-related neurological conditions.

Glutamatergic Dysfunction and Synaptic Ultrastructural Alterations in Schizophrenia and Autism Spectrum Disorder: Evidence from Human and Rodent Studies

The correlation between dysfunction in the glutamatergic system and neuropsychiatric disorders, including schizophrenia and autism spectrum disorder, is undisputed. Both disorders are associated with molecular and ultrastructural alterations that affect synaptic plasticity and thus the molecular and physiological basis of learning and memory. Altered synaptic plasticity, accompanied by changes in protein synthesis and trafficking of postsynaptic proteins, as well as structural modifications of excitatory synapses, are critically involved in the postnatal development of the mammalian nervous system. In this review, we summarize glutamatergic alterations and ultrastructural changes in synapses in schizophrenia and autism spectrum disorder of genetic or drug-related origin, and briefly comment on the possible reversibility of these neuropsychiatric disorders in the light of findings in regular synaptic physiology.

Heterogeneous clinical and functional features of GRIN2D-related developmental and epileptic encephalopathy

N-methyl d-aspartate receptors are ligand-gated ionotropic receptors mediating a slow, calcium-permeable component of excitatory synaptic transmission in the CNS. Variants in genes encoding NMDAR subunits have been associated with a spectrum of neurodevelopmental disorders. Here we report six novel GRIN2D variants and one previously-described disease-associated GRIN2D variant in two patients with developmental and epileptic encephalopathy. GRIN2D encodes for the GluN2D subunit protein; the GluN2D amino acids affected by the variants in this report are located in the pre-M1 helix, transmembrane domain M3, and the intracellular carboxyl terminal domain. Functional analysis in vitro reveals that all six variants decreased receptor surface expression, which may underline some shared clinical symptoms. In addition the GluN2D(Leu670Phe), (Ala675Thr) and (Ala678Asp) substitutions confer significantly enhanced agonist potency, and/or increased channel open probability, while the GluN2D(Ser573Phe), (Ser1271Phe) and (Arg1313Trp) substitutions result in a mild increase of agonist potency, reduced sensitivity to endogenous protons, and decreased channel open probability. The GluN2D(Ser573Phe), (Ala675Thr), and (Ala678Asp) substitutions significantly decrease current amplitude, consistent with reduced surface expression. The GluN2D(Leu670Phe) variant slows current response deactivation time course and increased charge transfer. GluN2D(Ala678Asp) transfection significantly decreased cell viability of rat cultured cortical neurons. In addition, we evaluated a set of FDA-approved NMDAR channel blockers to rescue functional changes of mutant receptors. This work suggests the complexity of the pathological mechanisms of GRIN2D-mediated developmental and epileptic encephalopathy, as well as the potential benefit of precision medicine.

Revisiting the excitation/inhibition imbalance hypothesis of ASD through a clinical lens

Autism spectrum disorder (ASD) currently affects 1 in 59 children, although the aetiology of this disorder remains unknown. Faced with multiple seemingly disparate and noncontiguous neurobiological alterations, Rubenstein and Merzenich hypothesized that imbalances between excitatory and inhibitory neurosignaling (E/I imbalance) underlie ASD. Since this initial statement, there has been a major focus examining this exact topic spanning both clinical and preclinical realms. The purpose of this article is to review the clinical neuroimaging literature surrounding E/I imbalance as an aetiology of ASD. Evidence for E/I imbalance is presented from several complementary clinical techniques including magnetic resonance spectroscopy, magnetoencephalography and transcranial magnetic stimulation. Additionally, two GABAergic potential interventions for ASD, which explicitly attempt to remediate E/I imbalance, are reviewed. The current literature suggests E/I imbalance as a useful framework for discussing the neurobiological etiology of ASD in at least a subset of affected individuals. While not constituting a completely unifying aetiology, E/I imbalance may be relevant as one of several underlying neuropathophysiologies that differentially affect individuals with ASD. Such statements do not diminish the value of the E/I imbalance concept-instead they suggest a possible role for the characterization of E/I imbalance, as well as other underlying neuropathophysiologies, in the biologically-based subtyping of individuals with ASD for potential applications including clinical trial enrichment as well as treatment triage.

Digital Attention-Related Augmented-Reality Game: Significant Correlation between Student Game Performance and Validated Clinical Measures of Attention-Deficit/Hyperactivity Disorder (ADHD)

As many as half of school children with autism spectrum disorder (ASD) exhibit symptoms of attention-deficit/hyperactivity disorder (ADHD), resulting in marked negative academic, social, and behavioral outcomes. The focus of the US Food and Drug Administration (FDA) on real-world data from novel digital sources, and the emergence of Current Procedural Terminology (CPT) codes to reimburse for digital monitoring and neurobehavioral testing suggest an increasing acceptance of the role of technology in augmenting clinical care and research. Empowered Brain is an augmented reality and artificial intelligence-based social-emotional communication aid for students with ASD. In this study, student performance on Empowered Brain is correlated to validated clinical measures of ADHD. Seven high school students with a diagnosis of ASD were recruited from a public high school. All students were assessed for severity of ADHD-related symptoms via three clinical gold-standard assessments, namely the Aberrant Behavioral Checklist (ABC), Social Responsiveness Scale 2 (SRS-2), and Teacher Report Form (TRF). Students used Empowered Brain over a one-week period. We measured the correlation of student in-game performance (as measured by point- and star-based rewards) relative to the hyperactivity subscale of the ABC (ABC-H), and the ADHD-subscale of the TRF. All seven students completed the study and managed to successfully use Empowered Brain. Students received a culminative total of 32 sessions, an average of 4.6 sessions per student (range 2–8). Student in-game performance demonstrated highly significant correlation relative to ABC-H (points: p = 0.0013; stars: p = 0.0013), and significant correlation to TRF ADHD scores (points: p = 0.012; stars: p = 0.012). No adverse effects were noted among students who used Empowered Brain. New technologies may herald novel ways of identifying and characterizing symptoms of ADHD in student populations. This study provides evidence that Empowered Brain in-game performance correlates with ADHD symptom severity in students with ASD. Larger samples are required to validate these findings, with more diverse participants that can also widen the generalizability of these findings to a broader range of brain conditions that manifest with inattention, impulsivity, and hyperactivity. Through further research, we may find that such technologies can help us to identify and longitudinally monitor such symptoms, and potentially aid in severity stratification and digital phenotyping.

From bedside to bench and back: Translating ASD models

Autism spectrum disorders (ASD) represent a heterogeneous group of disorders defined by deficits in social interaction/communication and restricted interests, behaviors, or activities. Models of ASD, developed based on clinical data and observations, are used in basic science, the "bench," to better understand the pathophysiology of ASD and provide therapeutic options for patients in the clinic, the "bedside." Translational medicine creates a bridge between the bench and bedside that allows for clinical and basic science discoveries to challenge one another to improve the opportunities to bring novel therapies to patients. From the clinical side, biomarker work is expanding our understanding of possible mechanisms of ASD through measures of behavior, genetics, imaging modalities, and serum markers. These biomarkers could help to subclassify patients with ASD in order to better target treatments to a more homogeneous groups of patients most likely to respond to a candidate therapy. In turn, basic science has been responding to developments in clinical evaluation by improving bench models to mechanistically and phenotypically recapitulate the ASD phenotypes observed in clinic. While genetic models are identifying novel therapeutics targets at the bench, the clinical efforts are making progress by defining better outcome measures that are most representative of meaningful patient responses. In this review, we discuss some of these challenges in translational research in ASD and strategies for the bench and bedside to bridge the gap to achieve better benefits to patients.

Efficacy of Memantine as Adjunct Therapy for Autism Spectrum Disorder in Children Aged <14 Years

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a recent increase in prevalence. A timely appropriate treatment for the disorder may play a crucial role in improvements in behaviors, interactions, and communications in an individual's life. It appears that evaluation of therapeutic approaches to the patients is essential and of importance. Thus, the aim of this study was to evaluate the efficacy of memantine as adjunct therapy in children with ASD.

MATERIALS AND METHODS

This randomized single-blind clinical trial included 60 children with ASD aged <14. The children undergoing applied behavior analysis (ABA) were divided into two groups of placebo and memantine (5 mg/day: a half of tablet in the morning and a half in the evening). After a 3-month course, improvements in symptoms of ASD were evaluated in both groups based on Gilliam autism rating scale. The collected data were analyzed with SPSS (version 20) using independent samples t-test, paired samples t-test, Chi-squared test and Fisher's exact test.

RESULTS

Both groups were similar in baseline characteristics including age, gender, and ASD symptoms (P > 0.05) but post intervention, total scores of ASD symptoms in both groups of memantine (mean score1 =95.20 ± 14.49; mean score2=73.50 ± 9.81) and control group (mean scorebefore = 91.50 ± 14.35; mean scoreafter = 89.63 ± 13.95) showed a decrease which was only significant in intervention group (P < 0.001).

CONCLUSION

Accordingly, memantine administration as adjunct therapy can be more effective in improvement of ASD symptoms in children than ABA alone. Thus, it can be considered as a new selective adjunct therapy.

Improved Socio-Emotional and Behavioral Functioning in Students with Autism Following School-Based Smartglasses Intervention: Multi-Stage Feasibility and Controlled Efficacy Study

Background: Students with Autism Spectrum Disorder (ASD) commonly demonstrate prominent social communication deficits, symptoms of attention-deficit/hyperactivity disorder, and chronic irritability. These challenges hinder academic progress and frequently persist despite educational, behavioral, and medical interventions. An assistive smartglasses technology may aid these individuals, especially if the technology is efficacious in ecologically-valid school settings. This study explored the feasibility and efficacy of Empowered Brain, a computerized smartglasses intervention designed as a socio-emotional behavioral aid for students with ASD. Methods: This two-part six-week study involved four school children with ASD from a public elementary school. The study incorporated an initial three-week feasibility stage followed by a three-week controlled longitudinal efficacy stage. Both stages involved the use of a twice-daily socio-emotional intervention with the smartglasses. Educators completed pre-intervention and post-intervention Aberrant Behavioral Checklist (ABC) ratings at the start of the feasibility stage, and weekly during the efficacy stage. Primary outcome measures were improvements in the ABC subscales of irritability, hyperactivity, and social withdrawal. Results: Students in both feasibility and efficacy stages demonstrated improvements (decreases) in irritability, hyperactivity, and social withdrawal compared to a baseline period and control periods, respectively. Participants in the controlled efficacy stage demonstrated decreased ABC subscale scores of 90% for irritability, 41.6% for hyperactivity, and 45.6% for social withdrawal. An intervention exposure-response improvement in irritability and hyperactivity was found during the efficacy stage. Educators rated the technology as superior or vastly superior compared to other assistive technologies. Conclusion: A substantial number of school children with ASD demonstrate chronic and impairing cognitive and behavioral challenges. This study provides evidence that Empowered Brain, a smartglasses-based socio-emotional aid for autism, is both feasible and efficacious in improving symptoms of social withdrawal, irritability, and hyperactivity in students with autism. The improvement is demonstrated as part of a longitudinal school-based intervention. Further studies involving larger samples and incorporation of randomized controlled trial methodology are underway to further elucidate the impact of this technology.

Social Skills Deficits in Autism Spectrum Disorder: Potential Biological Origins and Progress in Developing Therapeutic Agents

Autism spectrum disorder is defined by two core symptoms: a deficit in social communication and the presence of repetitive behaviors and/or restricted interests. Currently, there is no US Food and Drug Administration-approved drug for these core symptoms. This article reviews the biological origins of the social function deficit associated with autism spectrum disorder and the drug therapies with the potential to treat this deficit. A review of the history of autism demonstrates that a deficit in social interaction has been the defining feature of the concept of autism from its conception. Abnormalities identified in early social skill development and an overview of the pathophysiology abnormalities associated with autism spectrum disorder are discussed as are the abnormalities in brain circuits associated with the social function deficit. Previous and ongoing clinical trials examining agents that have the potential to improve social deficits associated with autism spectrum disorder are discussed in detail. This discussion reveals that agents such as oxytocin and propranolol are particularly promising and undergoing active investigation, while other agents such as vasopressin agonists and antagonists are being activity investigated but have limited published evidence at this time. In addition, agents such as bumetanide and manipulation of the enteric microbiome using microbiota transfer therapy appear to have promising effects on core autism spectrum disorder symptoms including social function. Other pertinent issues associated with developing treatments in autism spectrum disorder, such as disease heterogeneity, high placebo response rates, trial design, and the most appropriate way of assessing effects on social skills (outcome measures), are also discussed.

Excitotoxicity in the pathogenesis of neurological and psychiatric disorders: Therapeutic implications

Neurological and psychiatric disorders are leading contributors to the global disease burden, having a serious impact on the quality of life of both patients and their relatives. Although the molecular events underlying these heterogeneous diseases remain poorly understood, some studies have raised the idea of common mechanisms involved. In excitotoxicity, there is an excessive activation of glutamate receptors by excitatory amino acids, leading to neuronal damage. Thus, the excessive release of glutamate can lead to a dysregulation of Ca²⁺ homeostasis, triggering the production of free radicals and oxidative stress, mitochondrial dysfunction and eventually cell death. Although there is a consensus in considering excitotoxicity as a hallmark in most neurodegenerative diseases, increasing evidence points to the relevant role of this pathological mechanism in other illnesses affecting the central nervous system. Consequently, antagonists of glutamate receptors are used in current treatments or in clinical trials in both neurological and psychiatric disorders. However, drugs modulating other aspects of the excitotoxic mechanism could be more beneficial. This review discusses how excitotoxicity is involved in the pathogenesis of different neurological and psychiatric disorders and the promising strategies targeting the excitotoxic insult.

l-Carnosine As an Adjunctive Therapy to Risperidone in Children with Autistic Disorder: A Randomized, Double-Blind, Placebo-Controlled Trial

OBJECTIVES

This study aimed at investigating the efficacy and tolerability of l-carnosine as an add-on to risperidone in the management of children with autism.

METHODS

This was a 10-week, randomized, double-blind, placebo-controlled study. Seventy drug-free children aged 4-12 years old with a diagnosis of autism spectrum disorder (ASD), according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition. (DSM-5) who had an Aberrant Behavior Checklist-Community (ABC-C) scale irritability subscale score of ≥12, entered the study. The patients were randomly assigned to l-carnosine (800 mg/day in 2 divided doses) or placebo in addition to risperidone titrated up to 2 mg/day (based on body weight) for 10 weeks. The children were assessed by using ABC-C at baseline and weeks 5 and 10 post-baseline. The primary outcome measure was the mean change in the ABC-C irritability subscale score, and other subscale scores were defined as secondary outcomes.

RESULTS

Using the general linear model repeated measures, no significant effect was observed for time × treatment interaction on the irritability subscale scores. However, significant effect was detected on the hyperactivity/noncompliance subscale [F (1.62, 64.96) = 3.53, p-value = 0.044]. No significant improvements were obtained on the lethargy/social withdrawal, stereotypic behavior, and inappropriate speech subscale scores. Significantly greater score reduction in the hyperactivity/noncompliance subscale occurred in the l-carnosine group compared with the placebo group at the end of the trial. Extrapyramidal Symptom Rating Scale Scores and its changes did not differ between the two groups. The frequency of other side effects was not significantly different between the two groups.

CONCLUSIONS

Although no significant difference was detected on the irritability subscale scores, l-carnosine add-on can improve hyperactivity/noncompliance subscales of the ABC-C rating scale in patients with ASD.

Autism spectrum disorder: Consensus guidelines on assessment, treatment and research from the British Association for Psychopharmacology

An expert review of the aetiology, assessment, and treatment of autism spectrum disorder, and recommendations for diagnosis, management and service provision was coordinated by the British Association for Psychopharmacology, and evidence graded. The aetiology of autism spectrum disorder involves genetic and environmental contributions, and implicates a number of brain systems, in particular the gamma-aminobutyric acid, serotonergic and glutamatergic systems. The presentation of autism spectrum disorder varies widely and co-occurring health problems (in particular epilepsy, sleep disorders, anxiety, depression, attention deficit/hyperactivity disorder and irritability) are common. We did not recommend the routine use of any pharmacological treatment for the core symptoms of autism spectrum disorder. In children, melatonin may be useful to treat sleep problems, dopamine blockers for irritability, and methylphenidate, atomoxetine and guanfacine for attention deficit/hyperactivity disorder. The evidence for use of medication in adults is limited and recommendations are largely based on extrapolations from studies in children and patients without autism spectrum disorder. We discuss the conditions for considering and evaluating a trial of medication treatment, when non-pharmacological interventions should be considered, and make recommendations on service delivery. Finally, we identify key gaps and limitations in the current evidence base and make recommendations for future research and the design of clinical trials.

Current status of biological treatment options in Autism Spectrum Disorder

Autism Spectrum Disorders (ASDs) are characterised by deficits in social communication and restricted and repetitive behaviours. With an onset in early childhood, ASDs are thought to be heterogeneous, both genetically and clinically. This has led to the notion that "autism" is "autisms", however, there has been limited progress in understanding the different subgroups and the unique pathogenesis that would then allow targeted intervention. Although existing treatments are mainly symptom focussed, research is beginning to unravel the underlying genetic and molecular pathways, structural and functional neuronal circuitry involvement and the associated neurochemicals. This paper will review selected biological models with regard to pharmacological targets while also covering some of the non-pharmacological treatments such as neuro-stimulation.

Safety and Efficacy of Memantine in Children with Autism: Randomized, Placebo-Controlled Study and Open-Label Extension

OBJECTIVE

Abnormal glutamatergic neurotransmission is implicated in the pathophysiology of autism spectrum disorder (ASD). In this study, the safety, tolerability, and efficacy of the glutamatergic N-methyl-d-aspartate (NMDA) receptor antagonist memantine (once-daily extended-release [ER]) were investigated in children with autism in a randomized, placebo-controlled, 12 week trial and a 48 week open-label extension.

METHODS

A total of 121 children 6-12 years of age with Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Text Revision (DSM-IV-TR)-defined autistic disorder were randomized (1:1) to placebo or memantine ER for 12 weeks; 104 children entered the subsequent extension trial. Maximum memantine doses were determined by body weight and ranged from 3 to 15 mg/day.

RESULTS

There was one serious adverse event (SAE) (affective disorder, with memantine) in the 12 week study and one SAE (lobar pneumonia) in the 48 week extension; both were deemed unrelated to treatment. Other AEs were considered mild or moderate and most were deemed not related to treatment. No clinically significant changes occurred in clinical laboratory values, vital signs, or electrocardiogram (ECG). There was no significant between-group difference on the primary efficacy outcome of caregiver/parent ratings on the Social Responsiveness Scale (SRS), although an improvement over baseline at Week 12 was observed in both groups. A trend for improvement at the end of the 48 week extension was observed. No improvements in the active group were observed on any of the secondary end-points, with one communication measure showing significant worsening with memantine compared with placebo (p = 0.02) after 12 weeks.

CONCLUSIONS

This trial did not demonstrate clinical efficacy of memantine ER in autism; however, the tolerability and safety data were reassuring. Our results could inform future trial design in this population and may facilitate the investigation of memantine ER for other clinical applications.

Lithium protects hippocampal progenitors, cognitive performance and hypothalamus-pituitary function after irradiation to the juvenile rat brain

Cranial radiotherapy in children typically causes delayed and progressive cognitive dysfunction and there is no effective preventive strategy for radiation-induced cognitive impairments. Here we show that lithium treatment reduced irradiation-induced progenitor cell death in the subgranular zone of the hippocampus, and subsequently ameliorated irradiation-reduced neurogenesis and astrogenesis in the juvenile rat brain. Irradiation-induced memory impairment, motor hyperactivity and anxiety-like behaviour were normalized by lithium treatment. Late-onset irradiation-induced hypopituitarism was prevented by lithium treatment. Additionally, lithium appeared relatively toxic to multiple cultured tumour cell lines, and did not improve viability of radiated DAOY cells in vitro. In summary, our findings demonstrate that lithium can be safely administered to prevent both short- and long-term injury to the juvenile brain caused by ionizing radiation.

d-Cycloserine enhances durability of social skills training in autism spectrum disorder

BACKGROUND

d-Cycloserine (DCS) enhances extinction learning across species, but it has proven challenging to identify consistent benefit of DCS when added to therapeutic interventions. We conducted a placebo-controlled trial of DCS to potentiate social skills training in autism spectrum disorder (ASD) but found substantial improvement in both the DCS and placebo groups at the conclusion of active treatment. Here, we assess the impact of DCS 11 weeks following active treatment to evaluate the impact of DCS on treatment response durability.

METHODS

Study participants included 60 outpatient youth with ASD, ages 5-11 years, all with IQ above 70, and significantly impaired social functioning who completed a 10-week active treatment phase during which they received weekly single doses of 50 mg of DCS or placebo administered 30 min prior to group social skills training. Following the 10-week active treatment phase, blinded follow-up assessments occurred at week 11 and week 22. The primary outcome measure for our durability of treatment evaluation was the parent-rated social responsiveness scale (SRS) total raw score at week 22.

RESULTS

Analysis of the SRS total raw score demonstrated significant decrease for the DCS group compared to the placebo group (p = 0.042) indicating greater maintenance of treatment effect in the DCS group. DCS was well tolerated, with irritability being the most frequently reported adverse effect in both groups.

CONCLUSIONS

The findings of this study suggest that DCS may help youth with ASD to maintain skills gained during sort-term social skills training. Larger-scale studies with longer follow-up will be necessary to further understand the long-term impact of DCS paired with structured social skills training.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01086475.

Current Practice and Future Avenues in Autism Therapy

Autism spectrum disorders (ASDs) are neurodevelopmental disorders with early onset, characterized by deficits in social communication and repetitive and restricted interests and activities. A growing number of studies over the last 10 years support the efficacy of behaviorally based interventions in ASD for the improvement of social communication and behavioral functioning. In contrast, research on neurobiological based therapies for ASD is still at its beginnings. In this article, we will provide a selective overview of both well-established evidence-based treatments and novel interventions and drug treatments based on neurobiological principles aiming at improving core symptoms in ASD. Directions and options for future research on treatment in ASD are discussed.

Pediatric Traumatic Brain Injury and Autism: Elucidating Shared Mechanisms

Pediatric traumatic brain injury (TBI) and autism spectrum disorder (ASD) are two serious conditions that affect youth. Recent data, both preclinical and clinical, show that pediatric TBI and ASD share not only similar symptoms but also some of the same biologic mechanisms that cause these symptoms. Prominent symptoms for both disorders include gastrointestinal problems, learning difficulties, seizures, and sensory processing disruption. In this review, we highlight some of these shared mechanisms in order to discuss potential treatment options that might be applied for each condition. We discuss potential therapeutic and pharmacologic options as well as potential novel drug targets. Furthermore, we highlight advances in understanding of brain circuitry that is being propelled by improved imaging modalities. Going forward, advanced imaging will help in diagnosis and treatment planning strategies for pediatric patients. Lessons from each field can be applied to design better and more rigorous trials that can be used to improve guidelines for pediatric patients suffering from TBI or ASD.

Minocycline as Adjunctive Treatment to Risperidone in Children with Autistic Disorder: A Randomized, Double-Blind Placebo-Controlled Trial

OBJECTIVE

This is an investigation of minocycline efficacy and safety as an adjuvant to risperidone in management of children with autism.

METHODS

Forty-six children with diagnosis of autistic disorder, according to the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Text Revision (DSM-IV-TR) criteria and a score of ≥12 on the Aberrant Behavior Checklist-Community (ABC-C) irritability subscale, who were already drug-free for at least 6 months participated in a randomized controlled trial and underwent 10 weeks of treatment with either minocycline (50 mg twice per day) or placebo in addition to risperidone titrated up to 2 mg/day (based on bodyweight). Patients were evaluated using ABC-C at baseline and at weeks 5 and 10.

RESULTS

General linear model repeated measures showed significant effect for time × treatment interaction on the irritability [F(2, 88) = 3.94, p = 0.02] and hyperactivity/noncompliance [F(1.50, 66.05) = 7.92, p = 0.002], but not for lethargy/social withdrawal [F(1.61, 71.02) = 0.98, p = 0.36], stereotypic behavior [F(1.34, 58.80) = 1.55, p = 0.22], and inappropriate speech subscale scores [F(1.52, 66.88) = 1.15, p = 0.31]. By week 10, 21 (91.3%) patients in the minocycline group and 15 (65.5%) patients in the placebo group achieved at least partial response (p = 0.03). Frequencies of adverse events were not significantly different between groups.

CONCLUSIONS

Minocycline seems to be a safe and effective adjuvant in management of patients with autistic disorder. Future studies with larger sample sizes, longer follow-ups, and inflammatory cytokine measurements are warranted to confirm these findings and provide insight into minocycline mechanism of action in autistic disorder.

GRIN2D Recurrent De Novo Dominant Mutation Causes a Severe Epileptic Encephalopathy Treatable with NMDA Receptor Channel Blockers

N-methyl-D-aspartate receptors (NMDARs) are ligand-gated cation channels that mediate excitatory synaptic transmission. Genetic mutations in multiple NMDAR subunits cause various childhood epilepsy syndromes. Here, we report a de novo recurrent heterozygous missense mutation-c.1999G>A (p.Val667Ile)-in a NMDAR gene previously unrecognized to harbor disease-causing mutations, GRIN2D, identified by exome and candidate panel sequencing in two unrelated children with epileptic encephalopathy. The resulting GluN2D p.Val667Ile exchange occurs in the M3 transmembrane domain involved in channel gating. This gain-of-function mutation increases glutamate and glycine potency by 2-fold, increases channel open probability by 6-fold, and reduces receptor sensitivity to endogenous negative modulators such as extracellular protons. Moreover, this mutation prolongs the deactivation time course after glutamate removal, which controls the synaptic time course. Transfection of cultured neurons with human GRIN2D cDNA harboring c.1999G>A leads to dendritic swelling and neuronal cell death, suggestive of excitotoxicity mediated by NMDAR over-activation. Because both individuals' seizures had proven refractory to conventional antiepileptic medications, the sensitivity of mutant NMDARs to FDA-approved NMDAR antagonists was evaluated. Based on these results, oral memantine was administered to both children, with resulting mild to moderate improvement in seizure burden and development. The older proband subsequently developed refractory status epilepticus, with dramatic electroclinical improvement upon treatment with ketamine and magnesium. Overall, these results suggest that NMDAR antagonists can be useful as adjuvant epilepsy therapy in individuals with GRIN2D gain-of-function mutations. This work further demonstrates the value of functionally evaluating a mutation, enabling mechanistic understanding and therapeutic modeling to realize precision medicine for epilepsy.

Phenotyping, Etiological Factors, and Biomarkers: Toward Precision Medicine in Autism Spectrum Disorders

Despite the progress made in understanding the biology of autism spectrum disorder (ASD), effective biological interventions for the core symptoms remain elusive. Because of the etiological heterogeneity of ASD, identification of a "one-size-fits-all" treatment approach will likely continue to be challenging. A meeting was convened at the University of Missouri and the Thompson Center to discuss strategies for stratifying patients with ASD for the purpose of moving toward precision medicine. The "white paper" presented here articulates the challenges involved and provides suggestions for future solutions.

Age-dependent effects on social interaction of NMDA GluN2A receptor subtype-selective antagonism

NMDA receptor-mediated neurotransmission is implicated in the regulation of normal sociability in mice. The heterotetrameric NMDA receptor is composed of two obligatory GluN1 and either two "modulatory" GluN2A or GluN2B receptor subunits. GluN2A and GluN2B-containing receptors differ in terms of their developmental expression, distribution between synaptic and extrasynaptic locations, and channel kinetic properties, among other differences. Because age-dependent differences in disruptive effects of GluN2A and GluN2B subtype-selective antagonists on sociability and locomotor activity have been reported in rats, the current investigation explored age-dependent effects of PEAQX, a GluN2A subtype-selective antagonist, on sociability, stereotypic behaviors emerging during social interaction, and spatial working memory in 4- and 8-week old male Swiss Webster mice. The data implicate an age-dependent contribution of GluN2A-containing NMDA receptors to the regulation of normal social interaction in mice. Specifically, at a dose of PEAQX devoid of any effect on locomotor activity and mouse rotarod performance, the social interaction of 8-week old mice was disrupted without any effect on the social salience of a stimulus mouse. Moreover, PEAQX attenuated stereotypic behavior emerging during social interaction in 4- and 8-week old mice. However, PEAQX had no effect on spontaneous alternations, a measure of spatial working memory, suggesting that neural circuits mediating sociability and spatial working memory may be discrete and dissociable from each other. Also, the data suggest that the regulation of stereotypic behaviors and sociability may occur independently of each other. Because expression of GluN2A-containing NMDA receptors occurs at a later developmental stage, they may be more involved in mediating the pathogenesis of ASDs in patients with histories of "regression" after a period of normal development than GluN2B receptors.

A Prospective Open-Label Trial of Memantine Hydrochloride for the Treatment of Social Deficits in Intellectually Capable Adults With Autism Spectrum Disorder

This prospective 12-week open-label trial evaluates the tolerability and efficacy of memantine hydrochloride for the treatment of core social and cognitive deficits in adults with high-functioning autism spectrum disorder (ASD). Measures for assessment of therapeutic response included the Social Responsiveness Scale-Adult Research Version (SRS-A), disorder-specific Clinical Global Impression scales, Behavior Rating Inventory of Executive Functioning-Adult Self-Report, Diagnostic Analysis of Nonverbal Accuracy Scale, and Cambridge Neuropsychological Test Automated Battery. Eighteen adults (mean age, 28 ± 9.5 years) with high-functioning ASD (SRS-A raw score, 99 ± 17) were treated with memantine (mean dose, 19.7 ± 1.2 mg/d; range, 15-20 mg), and 17 (94%) completed the trial. Treatment with memantine was associated with significant reduction on informant-rated (SRS-A, -28 ± 25; P < 0.001) and clinician-rated (Clinical Global Impression-Improvement subscale ≤2, 83%) measures of autism severity. In addition, memantine treatment was associated with significant improvement in ADHD and anxiety symptom severity. Significant improvement was noted in nonverbal communication on the Diagnostic Analysis of Nonverbal Accuracy Scale test and in executive function per self-report (Behavior Rating Inventory of Executive Functioning-Adult Self-Report Global Executive Composite, -6 ± 8.8; P < 0.015) and neuropsychological assessments (Cambridge Neuropsychological Test Automated Battery). Memantine treatment was generally well tolerated and was not associated with any serious adverse events. Treatment with memantine appears to be beneficial for the treatment of ASD and associated psychopathology and cognitive dysfunction in intellectually capable adults. Future placebo-controlled trials are warranted.

Effects of propranolol on conversational reciprocity in autism spectrum disorder: a pilot, double-blind, single-dose psychopharmacological challenge study

RATIONALE

Pharmacological intervention for autism spectrum disorder (ASD) is an important addition to treatment, yet currently available agents target co-morbid psychiatric concerns, such as aggression and irritability. Propranolol, a beta-adrenergic antagonist with anxiolytic effects, has been shown to improve verbal fluency and working memory in adults and adolescents with ASD in single-dose challenges.

OBJECTIVES

The present pilot study explores the acute effects of propranolol on a measure of conversational reciprocity in this population. We also examined whether autonomic activity and anxiety moderate or mediate response to the drug, given relationships between these variables and ASD, as well as the drug's effects.

METHODS

In a within-subject crossover design, 20 individuals with ASD received a single dose of propranolol or placebo during two sessions in a double-blinded, counterbalanced manner. After drug administration, participants performed a conversational reciprocity task by engaging in a short conversation with the researcher. Measurements of autonomic activity and anxiety were obtained before and after drug administration.

RESULTS

Propranolol significantly improved performance on the conversational reciprocity task total [d = 0.40] and nonverbal communication domain scores when compared to the placebo condition. However, neither autonomic activity nor anxiety was significantly associated with drug response.

CONCLUSIONS

Acute propranolol administration improved conversational reciprocity in ASD. Further exploration of these preliminary findings, as well as other potential treatment response predictors, with serial doses is warranted.

Glutamatergic medication in the treatment of obsessive compulsive disorder (OCD) and autism spectrum disorder (ASD) - study protocol for a randomised controlled trial

BACKGROUND

Compulsivity is a cross-disorder trait underlying phenotypically distinct psychiatric disorders that emerge in childhood or adolescence. Despite the effectiveness of serotonergic compounds in the treatment of obsessive-compulsive disorder, treatment-resistant symptoms remaining in 40 to 60 % of patients present a pressing clinical problem. There are currently no medications that effectively treat the core impairments of autism spectrum disorder. There is an urgent need for the development of conceptually novel pharmacological strategies. Agents targeting glutamate neurotransmission, such as memantine, represent promising candidates. This proof-of-concept clinical study will allow pilot-testing of memantine for both clinical effectiveness and tolerability/safety. Memantine is an N-methyl-D-aspartate receptor antagonist, approved for the treatment of Alzheimer's dementia in a number of countries.

METHODS/DESIGN

This 12-week study has an add-on, randomised, double-blind, placebo-controlled design of treatment with memantine, including an up-titration phase (forced flexible dose design, 5-15 mg/day), in patients aged 6-17 years and 9 months with obsessive-compulsive disorder or autism spectrum disorder. It is planned to include patients with obsessive-compulsive disorder (N = 50) or autism spectrum disorder (N = 50) across four centres in three European countries. Patients will be randomly assigned to memantine or placebo in a 1:1 ratio. Primary objectives are the investigation of the effectiveness of memantine in paediatric patients for improving symptoms of compulsivity (primary outcome measure: total score on the Children's Yale-Brown Obsessive-Compulsive Scale) and to explore its tolerability and safety. Secondary objectives are to explore the effects of memantine at the level of structure, function and biochemistry of the fronto-striatal circuits, and to collect blood for genetic analyses and biomarkers. Tertiary objectives are to explore the role of new candidate genes and pathways for compulsivity by linking genes to clinical phenotypes, response to treatment, neurocognitive test performance, and key structural and functional neuroimaging measures of the fronto-striatal circuits and to explore biomarkers/proteomics for compulsivity traits.

DISCUSSION

This study is part of the large, translational project TACTICS ( http://www.tactics-project.eu/ ) that is funded by the European Union and investigates the neural, genetic and molecular factors involved in the pathogenesis of compulsivity. Its results will provide clinically relevant solid information on potential new mechanisms and medication treatment in obsessive-compulsive and autism spectrum disorders.

TRIAL REGISTRATION

EudraCT Number: 2014-003080-38 , date of registration: 14 July 2014.

Translational Mouse Models of Autism: Advancing Toward Pharmacological Therapeutics

Animal models provide preclinical tools to investigate the causal role of genetic mutations and environmental factors in the etiology of autism spectrum disorder (ASD). Knockout and humanized knock-in mice, and more recently knockout rats, have been generated for many of the de novo single gene mutations and copy number variants (CNVs) detected in ASD and comorbid neurodevelopmental disorders. Mouse models incorporating genetic and environmental manipulations have been employed for preclinical testing of hypothesis-driven pharmacological targets, to begin to develop treatments for the diagnostic and associated symptoms of autism. In this review, we summarize rodent behavioral assays relevant to the core features of autism, preclinical and clinical evaluations of pharmacological interventions, and strategies to improve the translational value of rodent models of autism.

New Therapeutic Options for Autism Spectrum Disorder: Experimental Evidences

Autism spectrum disorder (ASD) is characterized by impairment in two behavioral domains: social interaction/communication together with the presence of stereotyped behaviors and restricted interests. The heterogeneity in the phenotype among patients and the complex etiology of the disorder have long impeded the advancement of the development of successful pharmacotherapies. However, in the recent years, the integration of findings of multiple levels of research, from human genetics to mouse models, have made considerable progress towards the understanding of ASD pathophysiology, allowing the development of more effective targeted drug therapies. The present review discusses the current state of pharmacological research in ASD based on the emerging common pathophysiology signature.

Ionotropic GABA and Glutamate Receptor Mutations and Human Neurologic Diseases

The advent of whole exome/genome sequencing and the technology-driven reduction in the cost of next-generation sequencing as well as the introduction of diagnostic-targeted sequencing chips have resulted in an unprecedented volume of data directly linking patient genomic variability to disorders of the brain. This information has the potential to transform our understanding of neurologic disorders by improving diagnoses, illuminating the molecular heterogeneity underlying diseases, and identifying new targets for therapeutic treatment. There is a strong history of mutations in GABA receptor genes being involved in neurologic diseases, particularly the epilepsies. In addition, a substantial number of variants and mutations have been found in GABA receptor genes in patients with autism, schizophrenia, and addiction, suggesting potential links between the GABA receptors and these conditions. A new and unexpected outcome from sequencing efforts has been the surprising number of mutations found in glutamate receptor subunits, with the GRIN2A gene encoding the GluN2A N-methyl-d-aspartate receptor subunit being most often affected. These mutations are associated with multiple neurologic conditions, for which seizure disorders comprise the largest group. The GluN2A subunit appears to be a locus for epilepsy, which holds important therapeutic implications. Virtually all α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor mutations, most of which occur within GRIA3, are from patients with intellectual disabilities, suggesting a link to this condition. Similarly, the most common phenotype for kainate receptor variants is intellectual disability. Herein, we summarize the current understanding of disease-associated mutations in ionotropic GABA and glutamate receptor families, and discuss implications regarding the identification of human mutations and treatment of neurologic diseases.