A Randomized Placebo-Controlled Cross-Over Pilot Study of Riluzole for Drug-Refractory Irritability in Autism Spectrum Disorder

The pediatric psychopharmacology of autism spectrum disorder: A systematic review - Part II: The future

Part I of this systematic review summarized the state-of-the-art of pediatric psychopharmacology for Autism Spectrum Disorder (ASD), a severe and lifelong neurodevelopmental disorder. The purpose of this Part II follow-up article is to provide a systematic overview of the experimental psychopharmacology of ASD. To this aim, we have first identified in the Clinicaltrials.gov website all the 157 pharmacological and nutraceutical compounds which have been experimentally tested in children and adolescents with ASD using the randomized placebo-controlled trial (RCT) design. After excluding 24 drugs already presented in Part I, a systematic review spanning each of the remaining 133 compounds was registered on Prospero (ID: CRD42023476555), performed on PubMed (August 8, 2024), and completed with EBSCO, PsycINFO (psychology and psychiatry literature) and the Cochrane Database of Systematic reviews, yielding a total of 115 published RCTs, including 57 trials for 23 pharmacological compounds and 48 trials for 17 nutraceuticals/supplements. Melatonin and oxytocin were not included, because recent systematic reviews have been already published for both these compounds. RCTs of drugs with the strongest foundation in preclinical research, namely arbaclofen, balovaptan and bumetanide have all failed to reach their primary end-points, although efforts to target specific patient subgroups do warrant further investigation. For the vast majority of compounds, including cannabidiol, vasopressin, and probiotics, insufficient evidence of efficacy and safety is available. However, a small subset of compounds, including N-acetylcysteine, folinic acid, l-carnitine, coenzyme Q10, sulforaphane, and metformin may already be considered, with due caution, for clinical use, because there is promising evidence of efficacy and a high safety profile. For several other compounds, such as secretin, efficacy can be confidently excluded, and/or the data discourage undertaking new RCTs. Part I and Part II summarize "drug-based" information, which will be ultimately merged to provide clinicians with a "symptom-based" consensus statement in a conclusive Part III, with the overarching aim to foster evidence-based clinical practices and to organize new strategies for future clinical trials.

Regulating Together: Emotion Dysregulation Group Treatment for ASD Youth and Their Caregivers

Individuals with autism spectrum disorder (ASD) experience behavioral and emotional symptoms hypothesized to arise from emotion dysregulation (ED), difficulty modulating emotional experience, expression, and intensity in an acceptable and contextually appropriate manner. We developed Regulating Together (RT)-an intensive-outpatient, caregiver-assisted group program to meet the ASD + ED intervention critical need. A within-subjects trial was conducted (5-week-control lead-in period, 5-week-treatment, and 5-and 10-weeks-post-treatment follow-ups). Forty-four youth with ASD + ED (25 8-12, 19 13-18 yr-olds, 88% male, mean FSIQ of 96) participated. Improvements were found in reactivity, emotion regulation knowledge, and flexibility post-treatment and 10-weeks post-treatment. A reduction in inpatient hospitalization rates by 16% from the 12 months pre-RT to 12 months post-RT was observed. RT shows promise to reduce ED in ASD.

Prediction of Behavioral Improvement Through Resting-State Electroencephalography and Clinical Severity in a Randomized Controlled Trial Testing Bumetanide in Autism Spectrum Disorder

BACKGROUND

Mechanism-based treatments such as bumetanide are being repurposed for autism spectrum disorder. We recently reported beneficial effects on repetitive behavioral symptoms that might be related to regulating excitation-inhibition (E/I) balance in the brain. Here, we tested the neurophysiological effects of bumetanide and the relationship to clinical outcome variability and investigated the potential for machine learning-based predictions of meaningful clinical improvement.

METHODS

Using modified linear mixed models applied to intention-to-treat population, we analyzed E/I-sensitive electroencephalography (EEG) measures before and after 91 days of treatment in the double-blind, randomized, placebo-controlled Bumetanide in Autism Medication and Biomarker study. Resting-state EEG of 82 subjects out of 92 participants (7-15 years) were available. Alpha frequency band absolute and relative power, central frequency, long-range temporal correlations, and functional E/I ratio treatment effects were related to the Repetitive Behavior Scale-Revised (RBS-R) and the Social Responsiveness Scale 2 as clinical outcomes.

RESULTS

We observed superior bumetanide effects on EEG, reflected in increased absolute and relative alpha power and functional E/I ratio and in decreased central frequency. Associations between EEG and clinical outcome change were restricted to subgroups with medium to high RBS-R improvement. Using machine learning, medium and high RBS-R improvement could be predicted by baseline RBS-R score and EEG measures with 80% and 92% accuracy, respectively.

CONCLUSIONS

Bumetanide exerts neurophysiological effects related to clinical changes in more responsive subsets, in whom prediction of improvement was feasible through EEG and clinical measures.

Systematic Review and Meta-analysis: Pharmacological and Nonpharmacological Interventions for Persistent Nonepisodic Irritability

OBJECTIVE

This meta-analysis examined the efficacy of available pharmacological and nonpharmacological interventions for irritability among youth with autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), disruptive behavior disorders (DBD), disruptive mood dysregulation disorder (DMDD), and/or severe mood dysregulation (SMD).

METHOD

Literature searches were conducted in October 2020, resulting in 564 abstracts being reviewed to identify relevant papers, with 387 articles being reviewed in full. A random effects model was used for the meta-analysis, with subgroup meta-regressions run to assess effects of study design, intervention type, medication class, and clinical population.

RESULTS

A total of 101 studies were included (80 pharmacological, 13 nonpharmacological, 8 combined). Despite high heterogeneity in effects (I2 = 94.3%), pooled posttreatment effect size for decreasing irritability was large (Hedges' g = 1.62). Large effects were found for pharmacological (g = 1.85) and nonpharmacological (g = 1.11) interventions; moderate effects were found for combined interventions relative to monotherapy interventions (g = 0.69). Antipsychotic medications provided the largest effect for reducing irritability relative to all other medication classes and nonpharmacological interventions. A large effect was found for youth with ASD (g = 1.89), whereas a medium effect was found for youth with ADHD/DMDD/DBD/SMD (g = 0.64).

CONCLUSION

This meta-analysis provides a comprehensive review of interventions targeting persistent nonepisodic irritability among youth with various psychiatric disorders. Strong evidence was found for medium-to-large effects across study design, intervention type, and clinical populations, with the largest effects for pharmacological interventions, particularly antipsychotic medications and combined pharmacological interventions, and interventions for youth with ASD.

Systematic Review and Meta-analysis: Efficacy of Pharmacological Interventions for Irritability and Emotional Dysregulation in Autism Spectrum Disorder and Predictors of Response

OBJECTIVE

Emotional dysregulation and irritability are common in individuals with autism spectrum disorder (ASD). We conducted the first meta-analysis assessing the efficacy of a broad range of pharmacological interventions for emotional dysregulation and irritability in ASD and predictors of response.

METHOD

Following a preregistered protocol (PROSPERO: CRD42021235779), we systematically searched multiple databases until January 1, 2021. We included placebo-controlled randomized controlled trials (RCTs) and evaluated the efficacy of pharmacological interventions and predictors of response for emotional dysregulation and irritability. We assessed heterogeneity using Q statistics and publication bias. We conducted subanalyses and meta-regressions to identify predictors of response. The primary effect size was the standardized mean difference. Quality of studies was assessed using the Cochrane Risk of Bias Tool (RoB2).

RESULTS

A total of 2,856 individuals with ASD in 45 studies were included, among which 26.7% of RCTs had a high risk of bias. Compared to placebo, antipsychotics (standardized mean difference = 1.028, 95% CI = 0.824-1.232) and medications used to treat attention-deficit/hyperactivity disorder (ADHD) (0.471, 0.061-0.881) were significantly better than placebo in improving emotional dysregulation and irritability, whereas evidence of efficacy was not found for other drug classes (p > .05). Within individual medications, evidence of efficacy was found for aripiprazole (1.179, 0.838-1.520) and risperidone (1.074, 0.818-1.331). Increased rates of comorbid epilepsy (β = -0.049, p = .026) were associated with a lower efficacy.

CONCLUSION

Some pharmacological interventions (particularly risperidone and aripiprazole) have proved efficacy for short-term treatment of emotional dysregulation and irritability in ASD and should be considered within a multimodal treatment plan, taking into account also the tolerability profile and families' preferences.

Autism Spectrum Disorder: Neurodevelopmental Risk Factors, Biological Mechanism, and Precision Therapy

Autism spectrum disorder (ASD) is a heterogeneous, behaviorally defined neurodevelopmental disorder. Over the past two decades, the prevalence of autism spectrum disorders has progressively increased, however, no clear diagnostic markers and specifically targeted medications for autism have emerged. As a result, neurobehavioral abnormalities, neurobiological alterations in ASD, and the development of novel ASD pharmacological therapy necessitate multidisciplinary collaboration. In this review, we discuss the development of multiple animal models of ASD to contribute to the disease mechanisms of ASD, as well as new studies from multiple disciplines to assess the behavioral pathology of ASD. In addition, we summarize and highlight the mechanistic advances regarding gene transcription, RNA and non-coding RNA translation, abnormal synaptic signaling pathways, epigenetic post-translational modifications, brain-gut axis, immune inflammation and neural loop abnormalities in autism to provide a theoretical basis for the next step of precision therapy. Furthermore, we review existing autism therapy tactics and limits and present challenges and opportunities for translating multidisciplinary knowledge of ASD into clinical practice.

Chloride imbalance in Fragile X syndrome

Developmental changes in ionic balance are associated with crucial hallmarks in neural circuit formation, including changes in excitation and inhibition, neurogenesis, and synaptogenesis. Neuronal excitability is largely mediated by ionic concentrations inside and outside of the cell, and chloride (Cl-) ions are highly influential in early neurodevelopmental events. For example, γ-aminobutyric acid (GABA) is the main inhibitory neurotransmitter of the mature central nervous system (CNS). However, during early development GABA can depolarize target neurons, and GABAergic depolarization is implicated in crucial neurodevelopmental processes. This developmental shift of GABAergic neurotransmission from depolarizing to hyperpolarizing output is induced by changes in Cl- gradients, which are generated by the relative expression of Cl- transporters Nkcc1 and Kcc2. Interestingly, the GABA polarity shift is delayed in Fragile X syndrome (FXS) models; FXS is one of the most common heritable neurodevelopmental disorders. The RNA binding protein FMRP, encoded by the gene Fragile X Messenger Ribonucleoprotein-1 (Fmr1) and absent in FXS, appears to regulate chloride transporter expression. This could dramatically influence FXS phenotypes, as the syndrome is hypothesized to be rooted in defects in neural circuit development and imbalanced excitatory/inhibitory (E/I) neurotransmission. In this perspective, we summarize canonical Cl- transporter expression and investigate altered gene and protein expression of Nkcc1 and Kcc2 in FXS models. We then discuss interactions between Cl- transporters and neurotransmission complexes, and how these links could cause imbalances in inhibitory neurotransmission that may alter mature circuits. Finally, we highlight current therapeutic strategies and promising new directions in targeting Cl- transporter expression in FXS patients.

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.

Autism Spectrum Disorder: Focus on Glutamatergic Neurotransmission

Disturbances in the glutamatergic system have been increasingly documented in several neuropsychiatric disorders, including autism spectrum disorder (ASD). Glutamate-centered theories of ASD are based on evidence from patient samples and postmortem studies, as well as from studies documenting abnormalities in glutamatergic gene expression and metabolic pathways, including changes in the gut microbiota glutamate metabolism in patients with ASD. In addition, preclinical studies on animal models have demonstrated glutamatergic neurotransmission deficits and altered expression of glutamate synaptic proteins. At present, there are no approved glutamatergic drugs for ASD, but several ongoing clinical trials are currently focusing on evaluating in autistic patients glutamatergic pharmaceuticals already approved for other conditions. In this review, we provide an overview of the literature concerning the role of glutamatergic neurotransmission in the pathophysiology of ASD and as a potential target for novel treatments.

Novel treatments in autism spectrum disorder

PURPOSE OF REVIEW

There are currently no approved medications for the core symptoms of autism spectrum disorder (ASD), and only limited data on the management of co-occurring mental health and behavioural symptoms. The purpose of this review is to synthesize recent trials on novel treatments in ASD, with a focus on research trends in the past 2 years.

RECENT FINDINGS

No new pharmacologic agents received regulatory approval for use in ASD. Several large randomized controlled trials (RCTs) had negative or ambiguous results (e.g. fluoxetine, oxytocin). A cross-over RCT of an oral cannabinoid suggested possible benefits for disruptive behaviours. Two large-scale multicentre trials of bumetanide were terminated early for lack of efficacy. Multicenter trials using repetitive transcranial magnetic stimulation are underway. Recent meta-analyses indicate that specific behavioural and psychological interventions can support social communication and treat anxiety. Numerous novel treatment targets informed by biological mechanisms are under investigation.

SUMMARY

Recent data support the use of behavioural and psychological interventions for social communication and anxiety in ASD; data are more limited regarding pharmacotherapy for core and associated symptoms. Next steps include replication of early findings, trials of new molecular targets, and the identification of novel biomarkers, including genetic predictors, of treatment response.

Novel treatments for autism spectrum disorder based on genomics and systems biology

BACKGROUND

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder with a complex underlying genetic architecture. There are currently no known pharmacologic treatments for the core ASD symptoms of social deficits and restricted/ repetitive behavior. However, there are dozens of clinical trials currently underway that are testing the impact of novel and existing agents on core and associated symptoms in ASD.

METHODS

We present a narrative synthesis of the historical and contemporary challenges to drug discovery in ASD. We then provide an overview of novel treatments currently under investigation from a genomics and systems biology perspective.

RESULTS

Data driven network and cluster analyses suggest alterations in transcriptional regulation, chromatin remodelling, synaptic transmission, neuropeptide signalling, and/or immunological mechanisms may contribute to or underlie the development of ASD. Agents and upcoming trials targeting each of the above listed systems are reviewed.

CONCLUSION

Identifying effective pharmacologic treatments for the core and associated symptom domains in ASD will require further collaboration and innovation in the areas of outcome measurement, biomarker research, and genomics, as well as systematic efforts to identify and treat subgroups of individuals with ASD who may be differentially responsive to specific treatments.

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.

Investigational drugs in early-stage clinical trials for autism spectrum disorder

Introduction: Pharmacologic interventions in Autism Spectrum Disorder (ASD) have historically focused on symptom-based approaches. However, a treatment for the core social deficits has remained unidentified. While a definitive theory for the cause of ASD is not yet known, recent advances in our understanding of ASD pathophysiology have opened the door for research on new pharmaceutical methods to target core symptomology. Areas covered: Herein, we review the novel pharmacologic therapies undergoing early-stage clinical trials for the treatment of the social symptoms associated with ASD. Specifically, these strategies center on altering neurologic excitatory and inhibitory imbalance, neuropeptide abnormalities, immunologic dysfunction, and biochemical deficiencies in ASD. Expert opinion: Utilizing the growing field of knowledge regarding the pathological mechanisms and altered neurobiology of individuals with ASD has led to the development of many innovative pharmaceutical interventions. Clinical trials for neurobiologic and immunologic targets show promise in impacting the social behavior and processing deficits in ASD but need evaluation in larger clinical trials and continued biomarker development to more effectively and consistently assess pharmacologic effects. Additionally, evaluating patient-specific drug responsivity and integrating behavioral intervention in conjunction with pharmacologic treatment is crucial to developing a successful approach to ASD treatment.

Efficacy and tolerability of riluzole in psychiatric disorders: A systematic review and preliminary meta-analysis

There is a pressing need for better pharmacological treatment strategies for psychiatric disorders as current treatment often results in partial symptom remission and unwanted side effects. A point of entry may be the glutamatergic system since glutamatergic dysregulation contributes to multiple psychiatric disorders. We evaluated the evidence from randomized controlled trials (RCTs) regarding the use of the glutamatergic drug riluzole in mental illnesses; and conducted preliminary meta-analyses of its effectiveness in treating obsessive-compulsive disorder (OCD) and depression. A systematic search was performed using PubMed (Medline), Embase, Cochrane Database of Systematic Reviews and PsycINFO. Meta-analyses were performed using Comprehensive Meta-Analysis software. Twenty-three RCTs were included for qualitative analysis and showed positive effects of adjunctive/monotherapy riluzole in patients with OCD, depression, autism, substance abuse and schizophrenia. Seven studies were also used for quantitative analysis, which revealed positive but non-significant effects on OCD and depression. Riluzole was generally well tolerated with few serious adverse events. The studies included in this systematic review were highly heterogeneous and the number of studies was limited per diagnostic condition. Moreover, few studies have examined riluzole as a single treatment. We suggest carrying out further work to provide definitive evidence for the benefit of riluzole in psychiatric illness.

Autism Spectrum Disorder and the Experience of Traumatic Events: Review of the Current Literature to Inform Modifications to a Treatment Model for Children with Autism

Children with autism incur trauma and have increased vulnerabilities for experiencing trauma. This paper summarizes the current literature in the study of trauma in typically developing children and those with autism. A treatment model for children with autism, drawing on components from cognitive behavior therapy (CBT), trauma-focused CBT, and CBT to teach emotion regulation and treat anxiety in children with autism is suggested. Components include: (a) Functional Behavior Assessment; (b) behavior plans and behavioral skills training; (c) teaching emotion regulation; (d) exposure therapy; (e) cognitive restructuring; (f) parent and child support between sessions; (g) safety plan; and (h) programming for generalization and maintenance. Future research should establish evidence-based treatment of trauma in this population by evaluating the modified treatment package.