Psychopharmacology : Autism Spectrum Disorders – An Emerging Area in Psychopharmacology (Mars 2014)

vendredi 28 février 2014

La revue Psychopharmacology consacre son numéro de mars 2014 à la question de l’autisme et de ses perspectives dans le domaine de la psychopharmacologie :

Autism Spectrum Disorders – An Emerging Area in Psychopharmacology

1. Steckler T, Spooren W, Murphy D. Autism spectrum disorders - an emerging area in psychopharmacology. Psychopharmacology. 2014 2014/03/01 ;231(6):977-8.

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2. Devine DP. Self-injurious behaviour in autistic children : a neuro-developmental theory of social and environmental isolation. Psychopharmacology. 2014 2014/03/01 ;231(6):979-97.

Self-injurious behaviour is not one of the three core symptoms that define autism. However, children on the autism spectrum appear to be particularly vulnerable. Afflicted children typically slap their faces, punch or bang their heads, and bite or pinch themselves. These behaviours can be extremely destructive, and they interfere with normal social and educational activities. However, the neurobiological mechanisms that confer vulnerability in children with autism have not been adequately described.

This review explores behavioural and neurobiological characteristics of children with autism that may be relevant for an increased understanding of their vulnerability for self-injurious behaviour.

Behavioural characteristics that are co-morbid for self-injurious behaviour in children with autism are examined. In addition, the contributions of social and environmental deprivation in self-injurious institutionalized orphans, isolated rhesus macaques, and additional animal models are reviewed.

There is extensive evidence that social and environmental deprivation promotes self-injurious behaviour in both humans (including children with autism) and animal models. Moreover, there are multiple lines of convergent neuroanatomical, neurophysiological, and neurochemical data that draw parallels between self-injurious children with autism and environmentally deprived humans and animals.

A hypothesis is presented that describes how the core symptoms of autism make these children particularly vulnerable for self-injurious behaviour. Relevant neurodevelopmental pathology is described in cortical, limbic, and basal ganglia brain regions, and additional research is suggested.

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3. Hsia Y, Wong AYS, Murphy DGM, Simonoff E, Buitelaar JK, Wong ICK. Psychopharmacological prescriptions for people with autism spectrum disorder (ASD) : a multinational study. Psychopharmacology. 2014 2014/03/01 ;231(6):999-1009.

Previous studies on psychotropic drugs prescribing in autism spectrum disorder (ASD) were from the USA or the UK. However, these studies may not be generalizable to other countries. There is a need to understand the extent of psychopharmacological prescribing for ASD treatment at a multinational level to identify areas of prescribing which lack evidence.

We used the IMS Prescribing Insights database to investigate psychotropic drugs prescribing patterns for ASD treatment in children and adults in 2010–2012. Data were obtained from Europe (France, Germany, Italy, Spain and UK), South America (Mexico and Brazil), North America (Canada and USA) and Asia (Japan).

North American countries have the highest prescription rates, followed by the European and South American countries. Prescribing rates were higher in children compared to adults in individual countries. The most commonly prescribed drug for ASD was risperidone in young people (except in UK and Japan). In the UK, methylphenidate (34 %) was the most commonly prescribed for young people and haloperidol (44.1 %) in Japan. In adults, the most commonly prescribed drug class was antipsychotics and particularly risperidone (thioridazine and ziprasidone were the most prescribed antipsychotics in Brazil and USA, respectively).

There is variation in medication prescription for people with ASD among countries, which may be attributable to diagnostic criteria, clinical guidelines or health care systems. However, there is a lack of evidence of efficacy and safety for many psychotropic drugs prescribed for people with ASD. Research is needed to bridge the evidence gaps in prescribing.

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4. Murray M, Hsia Y, Glaser K, Simonoff E, Murphy DM, Asherson P, Eklund H, Wong IK. Pharmacological treatments prescribed to people with autism spectrum disorder (ASD) in primary health care. Psychopharmacology. 2014 2014/03/01 ;231(6):1011-21.

approved in ASDs, and little is known about patterns of pharmacological treatment in the ASD population and associated co-morbidities.

We used The Health Improvement Network, a nationally representative primary care database, to assess the prevalence of ASD diagnoses, psychotropic drug prescribing and neuropsychiatric co-morbidities of 0–24 year olds between 1992 and 2008.

ASD prevalence increased 65-fold from 0.01 % (1992) to 0.50 % (2008). Psychotropic drugs were prescribed to 29 % (1,619/5,651) of the ASD cohort ; the most prescribed drugs were sleep medication (9.7 % of prescribed patients), psychostimulants (7.9 %) and antipsychotics (7.3 %). More patients were given psychostimulants and sleep medications over time from 1.5–6.3 % and 2.2–5.9 % respectively. Thirty-seven per cent of the cohort had ≥1 record of a neuropsychiatric co-morbidity, the most common being developmental difficulties and learning disabilities (12.6 %), behavioural, conduct and personality disorders (11.1 %) and attention deficit hyperactivity disorder (7.5 %).

British physicians are more conservative in prescribing practice than American colleagues. However, use of psychostimulants and antipsychotics is much higher in those with ASD than in the general population. Polypharmacy was seen in 34 % of prescribed patients in 2008. Additional studies examining use, efficacy, and long-term safety of antipsychotics and psychostimulants in autistic individuals are warranted.

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5. Politte LC, McDougle CJ. Atypical antipsychotics in the treatment of children and adolescents with pervasive developmental disorders. Psychopharmacology. 2014 2014/03/01 ;231(6):1023-36.

Autism and related pervasive developmental disorders (PDD) are characterized by impairments in social interaction and communication, restricted interests, and repetitive and stereotyped patterns of behavior. Individuals with PDD frequently display irritability and disruptive behaviors including tantrums, self-injurious behavior, and aggression. Atypical antipsychotics are currently the most efficacious pharmacological interventions available for treatment of irritability associated with PDD.

This article aims to review the body of literature pertaining to the use of atypical antipsychotics in the treatment of patients with PDD.

A PubMed literature search was conducted using the following key words : autism, pervasive developmental disorders, atypical antipsychotics, risperidone, aripiprazole, quetiapine, ziprasidone, olanzapine, clozapine, paliperidone, iloperidone, asenapine, and lurasidone. Search terms were limited to English language, human subjects, and publication from 1999 to present. Relevant references from identified articles were also reviewed.

The efficacy and tolerability of risperidone and aripiprazole for the treatment of irritability in autism have been established with multi-site, randomized, controlled trials. Studies supporting the use of other atypical antipsychotics are either limited in scope or less robust in their findings, though newer agents such as ziprasidone and paliperidone show promise.

Atypical antipsychotics are currently first-line pharmacological agents for the treatment of irritability and associated behaviors in children with PDD. Further placebo-controlled studies are warranted to characterize the efficacy and tolerability of the majority of these medications. There is also a need for the development of novel, targeted drugs with more favorable long-term side effect profiles.

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6. Kleijer KTE, Schmeisser MJ, Krueger DD, Boeckers TM, Scheiffele P, Bourgeron T, Brose N, Burbach JPH. Neurobiology of autism gene products : towards pathogenesis and drug targets. Psychopharmacology. 2014 2014/03/01 ;231(6):1037-62.

The genetic heterogeneity of autism spectrum disorders (ASDs) is enormous, and the neurobiology of proteins encoded by genes associated with ASD is very diverse. Revealing the mechanisms on which different neurobiological pathways in ASD pathogenesis converge may lead to the identification of drug targets.

The main objective is firstly to outline the main molecular networks and neuronal mechanisms in which ASD gene products participate and secondly to answer the question how these converge. Finally, we aim to pinpoint drug targets within these mechanisms.

Literature review of the neurobiological properties of ASD gene products with a special focus on the developmental consequences of genetic defects and the possibility to reverse these by genetic or pharmacological interventions.

The regulation of activity-dependent protein synthesis appears central in the pathogenesis of ASD. Through sequential consequences for axodendritic function, neuronal disabilities arise expressed as behavioral abnormalities and autistic symptoms in ASD patients. Several known ASD gene products have their effect on this central process by affecting protein synthesis intrinsically, e.g., through enhancing the mammalian target of rapamycin (mTOR) signal transduction pathway or through impairing synaptic function in general. These are interrelated processes and can be targeted by compounds from various directions : inhibition of protein synthesis through Lovastatin, mTOR inhibition using rapamycin, or mGluR-related modulation of synaptic activity.

ASD gene products may all feed into a central process of translational control that is important for adequate glutamatergic regulation of dendritic properties. This process can be modulated by available compounds but may also be targeted by yet unexplored routes.

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7. Vorstman JAS, Spooren W, Persico AM, Collier DA, Aigner S, Jagasia R, Glennon JC, Buitelaar JK. Using genetic findings in autism for the development of new pharmaceutical compounds. Psychopharmacology. 2014 2014/03/01 ;231(6):1063-78.

The main reason for the current lack of effective treatments for the core symptoms of autism is our limited understanding of the biological mechanisms underlying this heterogeneous group of disorders. A primary value of genetic research is enhancing our insight into the biology of autism through the study of identified autism risk genes.

In the current review we discuss (1) the genes and loci that are associated with autism, (2) how these provide us with essential cues as to what neurobiological mechanisms may be involved, and (3) how these mechanisms may be used as targets for novel treatments. Next, we provide an overview of currently ongoing clinical trials registered at clinicaltrials.gov with a variety of compounds. Finally, we review current approaches used to translate knowledge derived from gene discovery into novel pharmaceutical compounds and discuss their pitfalls and problems.

An increasing number of genetic variants associated with autism have been identified. This will generate new ideas about the biological mechanisms involved in autism, which in turn may provide new leads for the development of novel pharmaceutical compounds. To optimize this pipeline of drug discovery, large-scale international collaborations are needed for gene discovery, functional validation of risk genes, and improvement of clinical outcome measures and clinical trial methodology in autism.

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8. Cocks G, Curran S, Gami P, Uwanogho D, Jeffries AR, Kathuria A, Lucchesi W, Wood V, Dixon R, Ogilvie C, Steckler T, Price J. The utility of patient specific induced pluripotent stem cells for the modelling of Autistic Spectrum Disorders. Psychopharmacology. 2014 2014/03/01 ;231(6):1079-88.

Until now, models of psychiatric diseases have typically been animal models. Whether they were to be used to further understand the pathophysiology of the disorder, or as drug discovery tools, animal models have been the choice of preference in mimicking psychiatric disorders in an experimental setting. While there have been cellular models, they have generally been lacking in validity. This situation is changing with the advent of patient-specific induced pluripotent stem cells (iPSCs). In this article, we give a methodological evaluation of the current state of the iPS technology with reference to our own work in generating patient-specific iPSCs for the study of autistic spectrum disorder (ASD). In addition, we will give a broader perspective on the validity of this technology and to what extent it can be expected to complement animal models of ASD in the coming years.

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9. Aigner S, Heckel T, Zhang JD, Andreae LC, Jagasia R. Human pluripotent stem cell models of autism spectrum disorder : emerging frontiers, opportunities, and challenges towards neuronal networks in a dish. Psychopharmacology. 2014 2014/03/01 ;231(6):1089-104.

Autism spectrum disorder (ASD) is characterized by deficits in language development and social cognition and the manifestation of repetitive and restrictive behaviors. Despite recent major advances, our understanding of the pathophysiological mechanisms leading to ASD is limited. Although most ASD cases have unknown genetic underpinnings, animal and human cellular models of several rare, genetically defined syndromic forms of ASD have provided evidence for shared pathophysiological mechanisms that may extend to idiopathic cases. Here, we review our current knowledge of the genetic basis and molecular etiology of ASD and highlight how human pluripotent stem cell-based disease models have the potential to advance our understanding of molecular dysfunction. We summarize landmark studies in which neuronal cell populations generated from human embryonic stem cells and patient-derived induced pluripotent stem cells have served to model disease mechanisms, and we discuss recent technological advances that may ultimately allow in vitro modeling of specific human neuronal circuitry dysfunction in ASD. We propose that these advances now offer an unprecedented opportunity to help better understand ASD pathophysiology. This should ultimately enable the development of cellular models for ASD, allowing drug screening and the identification of molecular biomarkers for patient stratification.

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10. Dage JL, Colvin EM, Fouillet A, Langron E, Roell WC, Li J, Mathur SX, Mogg AJ, Schmitt MG, Felder CC, Merchant KM, Isaac J, Broad LM, Sher E, Ursu D. Pharmacological characterisation of ligand- and voltage-gated ion channels expressed in human iPSC-derived forebrain neurons. Psychopharmacology. 2014 2014/03/01 ;231(6):1105-24.

Genetic causes, or predisposition, are increasingly accepted to be part of the ethiopathogenesis of many neuropsychiatric diseases. While genes can be studied in any type of cells, their physiological function in human brain cells is difficult to evaluate, particularly in living subjects.

As a first step towards the characterisation of human inducible pluripotent stem cell (iPSC)-derived neurons from autism spectrum disorder (ASD) patients, we used gene expression and functional studies to define the regional identity of the typical forebrain differentiation, demonstrate expression patterns of genes of interest in ASD and understand the properties of ‘control’ iPSC-derived neurons (iCell-Neurons™), with a focus on receptors and ion channels that play a central role in synaptic physio-pathology.

The gene expression profile of the iCell-Neurons™ closely resembled that observed in neonatal prefrontal cortex tissues. Functional studies, performed mainly using calcium flux assays, demonstrated the presence of ionotropic glutamate (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-d-aspartate) and gamma-aminobutyric acid type A receptors. Voltage-gated sodium and calcium channels were also identified using similar techniques.

Overall, the results reported here suggest that iCell-Neurons™ are a good cellular model of a relatively immature forebrain human neuron population that can be used both as a control in comparison to patients cells, and as host cells in which mutations, insertions and deletions can be used in order to study the molecular mechanisms of ASD and other neurological disorders in an isogenic cellular background.

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11. Kas MJ, Glennon JC, Buitelaar J, Ey E, Biemans B, Crawley J, Ring RH, Lajonchere C, Esclassan F, Talpos J, Noldus LPJJ, Burbach JPH, Steckler T. Assessing behavioural and cognitive domains of autism spectrum disorders in rodents : current status and future perspectives. Psychopharmacology. 2014 2014/03/01 ;231(6):1125-46.

The establishment of robust and replicable behavioural testing paradigms with translational value for psychiatric diseases is a major step forward in developing and testing etiology-directed treatment for these complex disorders. Based on the existing literature, we have generated an inventory of applied rodent behavioural testing paradigms relevant to autism spectrum disorders (ASD). This inventory focused on previously used paradigms that assess behavioural domains that are affected in ASD, such as social interaction, social communication, repetitive behaviours and behavioural inflexibility, cognition as well as anxiety behaviour. A wide range of behavioural testing paradigms for rodents were identified. However, the level of face and construct validity is highly variable. The predictive validity of these paradigms is unknown, as etiology-directed treatments for ASD are currently not on the market. To optimise these studies, future efforts should address aspects of reproducibility and take into account data about the neurodevelopmental underpinnings and trajectory of ASD. In addition, with the increasing knowledge of processes underlying ASD, such as sensory information processes and synaptic plasticity, phenotyping efforts should include multi-level automated analysis of, for example, representative task-related behavioural and electrophysiological read-outs.

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12. Kas MJ, Modi ME, Saxe MlD, Smith DG. Advancing the discovery of medications for autism spectrum disorder using new technologies to reveal social brain circuitry in rodents. Psychopharmacology. 2014 2014/03/01 ;231(6):1147-65.

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition characterized by core differences and impairments in social behavioral functioning. There are no approved medications for improving social cognition and behavior in ASD, and the underlying mechanisms needed to discover safer, more effective medications are unclear.

In this review, we diagram the basic neurocircuitry governing social behaviors in order to provide a neurobiological framework for the origins of the core social behavioral symptoms of ASD. In addition, we discuss recent technological innovations in research tools that provide unprecedented observation of cellular morphology and activity deep within the intact brain and permit the precise control of discrete brain regions and specific cell types at distinct developmental stages.

The use of new technologies to reveal the neural circuits underlying social behavioral impairments associated with ASD is advancing our understanding of the brain changes underlying ASD and enabling the discovery of novel and effective therapeutic interventions.

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13. Petrinovic MM, Künnecke B. Neuroimaging Endophenotypes in Animal Models of Autism Spectrum Disorders : Lost or Found in Translation ?. Psychopharmacology. 2014 2014/03/01 ;231(6):1167-89.

Autism spectrum disorder(s) (ASDs) is a neurodevelopmental disorder characterized by stereotyped behaviours and impairments in communication and social interactions. This heterogeneity has been a major obstacle in uncovering the aetiology and biomarkers of ASDs. Rodent models with genetic modifications or environmental insults have been created to study particular endophenotypes and bridge the gap between genetics and behavioural phenotypes. Translational neuroimaging modalities with their ability to screen the brain noninvasively and yield structural, biochemical and functional information provide a unique platform for discovery and evaluation of such endophenotypes in preclinical and clinical research.

We reviewed literature on translational neuroimaging in rodent models of ASDs. The most prominent models will be described and the respective neuroimaging endophenotypes will be discussed with reference to human data. A perspective on future directions of translational neuroimaging in animal models of ASDs will be given.

To date, we experience a proliferation of rodent models which recapitulate specific liabilities identified in ASDs patients. Translational neuroimaging in these models is emerging but is skewed towards magnetic resonance imaging (MRI) modalities. Volumetric and structural assessments of the brain are dominating and a host of endophenotypes have been reported that allude to findings in ASDs patients but with only few to converge among the models. Caveats of current studies are the diverging biological conditions related to genetic background and age of the animals. It is anticipated that longitudinal and functional assessments will gain much importance and will help elucidating mechanistic relationship between behavioural and structural endophenotypes.

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14. Khatri N, Simpson KL, Lin RCS, Paul IA. Lasting neurobehavioral abnormalities in rats after neonatal activation of serotonin 1A and 1B receptors : possible mechanisms for serotonin dysfunction in autistic spectrum disorders. Psychopharmacology. 2014 2014/03/01 ;231(6):1191-200.

Perinatal exposure of rats to selective serotonin reuptake inhibitors (SSRIs) produces sensory and social abnormalities paralleling those seen in autistic spectrum disorders (ASDs). However, the possible mechanism(s) by which this exposure produces behavioral abnormalities is unclear.

We hypothesized that the lasting effects of neonatal SSRI exposure are a consequence of abnormal stimulation of 5-HT1A and/or 5-HT1B receptors during brain development. We examined whether such stimulation would result in lasting sensory and social deficits in rats in a manner similar to SSRIs using both direct agonist stimulation of receptors as well as selective antagonism of these receptors during SSRI exposure.

Male and female rat pups were treated from postnatal days 8 to 21. In Experiment 1, pups received citalopram (20 mg/kg/day), saline, (±)-8-hydroxy-dipropylaminotetralin hydrobromide (8-OH-DPAT ; 0.5 mg/kg/day) or 7-trifluoromethyl-4(4-methyl-1-piperazinyl)-pyrrolo[1,2-a]-quinoxaline dimaleate (CGS-12066B ; 10 mg/kg/day). In Experiment 2, a separate cohort of pups received citalopram (20 mg/kg/day), or saline which was combined with either N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclo-hexanecarboxamide maleate (WAY-100635 ; 0.6 mg/kg/day) or N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2′-methyl-4′-(5-methyl-1,2,4-oxadiazol-3-yl)-1-1′-biphenyl-4-carboxamide (GR-127935 ; 6 mg/kg/day) or vehicle. Rats were then tested in paradigms designed to assess sensory and social response behaviors at different time points during development.

Direct and indirect neonatal stimulation of 5-HT1A or 5-HT1B receptors disrupts sensory processing, produces neophobia, increases stereotypic activity, and impairs social interactions in manner analogous to that observed in ASD.

Increased stimulation of 5-HT1A and 5-HT1B receptors plays a significant role in the production of lasting social and sensory deficits in adult animals exposed as neonates to SSRIs.

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15. Ruggeri B, Sarkans U, Schumann G, Persico AM. Biomarkers in autism spectrum disorder : the old and the new. Psychopharmacology. 2014 2014/03/01 ;231(6):1201-16.

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder with onset during early childhood and typically a life-long course. The majority of ASD cases stems from complex, ‘multiple-hit’, oligogenic/polygenic underpinnings involving several loci and possibly gene–environment interactions. These multiple layers of complexity spur interest into the identification of biomarkers able to define biologically homogeneous subgroups, predict autism risk prior to the onset of behavioural abnormalities, aid early diagnoses, predict the developmental trajectory of ASD children, predict response to treatment and identify children at risk for severe adverse reactions to psychoactive drugs.

The present paper reviews (a) similarities and differences between the concepts of ‘biomarker’ and ‘endophenotype’, (b) established biomarkers and endophenotypes in autism research (biochemical, morphological, hormonal, immunological, neurophysiological and neuroanatomical, neuropsychological, behavioural), (c) -omics approaches towards the discovery of novel biomarker panels for ASD, (d) bioresource infrastructures and (e) data management for biomarker research in autism.

Known biomarkers, such as abnormal blood levels of serotonin, oxytocin, melatonin, immune cytokines and lymphocyte subtypes, multiple neuropsychological, electrophysiological and brain imaging parameters, will eventually merge with novel biomarkers identified using unbiased genomic, epigenomic, transcriptomic, proteomic and metabolomic methods, to generate multimarker panels. Bioresource infrastructures, data management and data analysis using artificial intelligence networks will be instrumental in supporting efforts to identify these biomarker panels.

Biomarker research has great heuristic potential in targeting autism diagnosis and treatment.

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16. Pop AS, Gomez-Mancilla B, Neri G, Willemsen R, Gasparini F. Fragile X syndrome : a preclinical review on metabotropic glutamate receptor 5 (mGluR5) antagonists and drug development. Psychopharmacology. 2014 2014/03/01 ;231(6):1217-26.

Fragile X syndrome (FXS) is considered the leading inherited cause of intellectual disability and autism. In FXS, the fragile X mental retardation 1 (FMR1) gene is silenced and the fragile X mental retardation protein (FMRP) is not expressed, resulting in the characteristic features of the syndrome. Despite recent advances in understanding the pathophysiology of FXS, there is still no cure for this condition ; current treatment is symptomatic. Preclinical research is essential in the development of potential therapeutic agents.

This review provides an overview of the preclinical evidence supporting metabotropic glutamate receptor 5 (mGluR5) antagonists as therapeutic agents for FXS.

According to the mGluR theory of FXS, the absence of FMRP leads to enhanced glutamatergic signaling via mGluR5, which leads to increased protein synthesis and defects in synaptic plasticity including enhanced long-term depression. As such, efforts to develop agents that target the underlying pathophysiology of FXS have focused on mGluR5 modulation. Animal models, particularly the Fmr1 knockout mouse model, have become invaluable in exploring therapeutic approaches on an electrophysiological, behavioral, biochemical, and neuroanatomical level. Two direct approaches are currently being investigated for FXS treatment : reactivating the FMR1 gene and compensating for the lack of FMRP. The latter approach has yielded promising results, with mGluR5 antagonists showing efficacy in clinical trials.

Targeting mGluR5 is a valid approach for the development of therapeutic agents that target the underlying pathophysiology of FXS. Several compounds are currently in development, with encouraging results.

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17. Pop AS, Levenga J, Esch CEF, Buijsen RAM, Nieuwenhuizen IM, Li T, Isaacs A, Gasparini F, Oostra BA, Willemsen R. Rescue of dendritic spine phenotype in Fmr1 KO mice with the mGluR5 antagonist AFQ056/Mavoglurant. Psychopharmacology. 2014 2014/03/01 ;231(6):1227-35.

Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and autism. The disease is a result of lack of expression of the fragile X mental retardation protein. Brain tissues of patients with FXS and mice with FMRP deficiency have shown an abnormal dendritic spine phenotype. We investigated the dendritic spine length and density of hippocampal CA1 pyramidal neurons in 2-, 10-, and 25-week-old Fmr1 knockout (KO). Next, we studied the effects of long-term treatment with an mGluR5 antagonist, AFQ056/Mavoglurant, on the spine phenotype in adult Fmr1 KO mice. We observed alterations in the spine phenotype during development, with a decreased spine length in 2-week-old Fmr1 KO mice compared with age-match wild-type littermates, but with increased spine length in Fmr1 KO mice compared with 10- and 25-week-old wild-type controls. No difference was found in spine density at any age. We report a rescue of the abnormal spine length in adult Fmr1 KO mice after a long-term treatment with AFQ056/Mavoglurant. This finding suggests that long-term treatment at later stage is sufficient to reverse the structural spine abnormalities and represents a starting point for future studies aimed at improving treatments for FXS.

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18. Jacquemont S, Berry-Kravis E, Hagerman R, Raison F, Gasparini F, Apostol G, Ufer M, Portes V, Gomez-Mancilla B. The challenges of clinical trials in fragile X syndrome. Psychopharmacology. 2014 2014/03/01 ;231(6):1237-50.

Advances in understanding the underlying mechanisms of conditions such as fragile X syndrome (FXS) and autism spectrum disorders have revealed heterogeneous populations. Recent trials of novel FXS therapies have highlighted several challenges including subpopulations with possibly differential therapeutic responses, the lack of specific outcome measures capturing the full range of improvements of patients with FXS, and a lack of biomarkers that can track whether a specific mechanism is responsive to a new drug and whether the response correlates with clinical improvement.

We review the phenotypic heterogeneity of FXS and the implications for clinical research in FXS and other neurodevelopmental disorders.

Residual levels of fragile X mental retardation protein (FMRP) expression explain in part the heterogeneity in the FXS phenotype ; studies indicate a correlation with both cognitive and behavioral deficits. However, this does not fully explain the extent of phenotypic variance observed or the variability of drug response. Post hoc analyses of studies involving the selective mGluR5 antagonist mavoglurant and the GABAB agonist arbaclofen have uncovered significant therapeutic responses following patient stratification according to FMR1 promoter methylation patterns or baseline severity of social withdrawal, respectively. Future studies designed to quantify disease modification will need to develop new strategies to track changes effectively over time and in multiple symptom domains.

Appropriate selection of patients and outcome measures is central to optimizing future clinical investigations of these complex disorders.

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19. Jucaite A, Öhd J, Potter AS, Jaeger J, Karlsson P, Hannesdottir K, Boström E, Newhouse PA, Paulsson B. A randomized, double-blind, placebo-controlled crossover study of α4β2* nicotinic acetylcholine receptor agonist AZD1446 (TC-6683) in adults with attention-deficit/hyperactivity disorder. Psychopharmacology. 2014 2014/03/01 ;231(6):1251-65.

Stimulation of nicotinic cholinergic systems has been shown to alleviate ADHD symptoms and to improve cognitive performance. AZD1446 is a selective α4β2* nicotinic acetylcholine receptor agonist with potential effect on the symptoms of ADHD.

The purpose of this study is to evaluate the efficacy, safety, and pharmacokinetics of AZD1446 in adults with ADHD treated for 2 weeks.

This was a randomized, double-blind, placebo-controlled crossover trial. Participants were 79 adults with ADHD, grouped according to their use of nicotine-containing products. Nicotine non-users received placebo and two of three AZD1446 treatment regimens (80 mg tid, 80 mg qd, 10 mg tid). Nicotine users received placebo, AZD1446 80 mg tid and 80 mg qd. Efficacy measures included the Conners’ Adult ADHD Rating Scale and cognitive measures of immediate and delayed verbal episodic memory, learning, attention, working memory, executive functioning, and spatial problem solving (CogState computerized test battery).

There was no significant effect of AZD1446 on any of the clinical scores irrespective of dose, schedule, or concomitant use of nicotine products. A statistically significant improvement was seen on the Groton Maze Learning Task, a measure of executive functioning, in nicotine non-users after treatment with AZD1446 80 mg qd.

AZD1446 was well tolerated, but did not significantly improve ADHD symptoms after 2 weeks of treatment compared to placebo. While the present study does not support the therapeutic utility of AZD1446 in ADHD, its potential pro-cognitive effects remain to be explored in other neuropsychiatric disorders.

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