Large multicenter randomized trials in autism: key insights gained from the balovaptan clinical development program

Cannabinoid treatment for the symptoms of autism spectrum disorder

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder affecting approximately 3% of school-age children. The core symptoms are deficits in social communication and restricted and repetitive patterns of behavior. Associated problems in cognition, language, behavior, sleep and mood are prevalent. Currently, no established pharmacological treatment exists for core ASD symptoms. Risperidone and aripiprazole are used to manage associated irritability, but their effectiveness is limited and adverse events are common.

AREAS COVERED

This mini-review summarizes existing scientific literature and ongoing clinical trials concerning cannabinoid treatment for ASD. Uncontrolled case series have documented improvements in both core ASD symptoms and related behavioral challenges in children treated with cannabis extracts rich in cannabidiol (CBD). Placebo-controlled studies involving CBD-rich cannabis extracts and/or pure CBD in children with ASD have demonstrated mixed efficacy results. A similar outcome was observed in a placebo-controlled study of pure CBD addressing social avoidance in Fragile X syndrome. Importantly, these studies have shown relatively high safety and tolerability.

EXPERT OPINION

While current clinical data suggest the potential of CBD and CBD-rich cannabis extract in managing core and behavioral deficits in ASD, it is prudent to await the results of ongoing placebo-controlled trials before considering CBD treatment for ASD.

Efficacy and safety of V1a receptor antagonists in autism spectrum disorder: A meta-analysis

This meta-analysis has evaluated the efficacy and safety of V1a receptor antagonists in ASD compared to placebo. The reviewers extracted data from four relevant clinical trials after a literature search on databases and clinical trial registries. Quality assessment was done using the risk of bias assessment tool, and the random-effects model was used to estimate effect size. Subgroup analysis, meta-regression and sensitivity analysis were done. PRISMA guidelines were followed in the selection, analysis and reporting of findings. V1a receptor antagonists did not reduce Vineland II Adaptive behaviour composite score significantly (SMD: 0.14; 95% CI: -0.06-0.35; p = 0.16; PI: -0.44-0.73), communication domain subscale score and socialization domain subscale score. The change in daily living skills domain subscale score was significant and favourable for V1a receptor antagonists (SMD: 0.15; 95% CI: 0.03-0.26; p = 0.01). The subgroup analysis revealed a significant improvement in Vineland II Adaptive behaviour composite score with doses <10 mg (SMD: 0.45; 95% CI: 0.11-0.78; p = 0.009). Meta-regression does not show a significant association between SMD of ASD symptom score reduction with the duration and dose of V1a receptor antagonist therapy. Treatment-emergent adverse effects were not serious and dose dependent. Low doses (<10 mg) of V1a receptor antagonist may be effective in reducing the core symptoms of ASD compared to placebo; however, future active-controlled clinical trials are necessary to generate conclusive evidence.

Mediators of Placebo Response to Cannabinoid Treatment in Children with Autism Spectrum Disorder

The placebo response has a substantial impact on treatment outcome. However, data regarding mediators of the placebo response in children with autism spectrum disorder (ASD) are sparse. This retrospective study investigated possible mediators of the placebo response among participants of a placebo-controlled trial of cannabinoid treatment for behavioral problems in children with ASD (CBA trial, age 5-21 years). We used a specifically designed questionnaire to explore possible mediators of the placebo response in 88 participants of the CBA trial who received a placebo and had valid outcome scores. The parents of 67 participants completed the questionnaire. The placebo response was positively associated with the child's comprehension of the treatment purpose (p = 0.037). There was also a trend for participants who had a relative aggravation of symptoms before treatment onset to improve following placebo treatment (p = 0.053). No other domains, including parental expectations, previous positive experience with similar treatments (behavioral conditioning), parental locus of control, quality of the patient-physician relationships, and adherence to study medications were associated with placebo-response. This finding suggests that efforts to explain the treatment purpose to children with disabilities may enhance treatment efficacy in clinical practice and decrease differences in the placebo response between study arms. Contrary to our hypothesis, parental expectations regarding cannabinoid treatment were not associated with the placebo response.

Predictors of placebo response in three large clinical trials of the V1a receptor antagonist balovaptan in autism spectrum disorder

High rates of placebo response are increasingly implicated in failed autism spectrum disorder (ASD) clinical trials. Despite this, there are limited investigations of placebo response in ASD. We sought to identify baseline predictors of placebo response and quantify their influence on clinical scales of interest for three harmonized randomized clinical trials of balovaptan, a V1a receptor antagonist. We employed a two-step approach to identify predictors of placebo response on the Vineland-II two-domain composite (2DC) (primary outcome and a caregiver measure) and Clinical Global Impression (CGI) scale (secondary outcome and a clinician measure). The initial candidate predictor set of variables pertained to participant-level, site-specific, and protocol-related factors. Step 1 aimed to identify influential predictors of placebo response using Least Absolute Shrinkage and Selection Operator (LASSO) regression, while Step 2 quantified the influence of predictors via linear regression. Results were validated through statistical bootstrapping approaches with 500 replications of the analysis dataset. The pooled participant-level dataset included individuals with ASD aged 5 to 62 years (mean age 21 [SD 10]), among which 263 and 172 participants received placebo at Weeks 12 and 24, respectively. Although no influential predictors were identified for CGI, findings for Vineland-II 2DC are robust and informative. Decreased placebo response was predicted by higher baseline Vineland-II 2DC (i.e., more advanced adaptive function), longer trial duration, and European (vs United States) sites, while increased placebo response was predicted by commercial (vs academic) sites, attention deficit hyperactivity disorder and depression. Identification of these factors may be useful in anticipating and mitigating placebo response in drug development efforts in ASD and across developmental and psychiatric conditions.

Clinician- versus caregiver-rated scales as outcome measures of repetitive-restricted behaviors in clinical trials of autism: A systematic review and meta-analysis

The agreement between treatment effects measured by clinician- and caregiver-ratings of repetitive-restricted behaviors (RRBs) is important for clinical practice and research but is still unclear. Therefore, we conducted a post-hoc meta-analysis of placebo-controlled randomized-controlled trials (RCTs) investigating pharmacological and dietary-supplement treatments for autism that reported both clinician- and caregiver-ratings of RRBs. Treatment effects between medications and placebo were quantified with standardized mean differences (SMDs). The agreement between clinician- and caregiver-rated SMDs was investigated with an intraclass correlation coefficient (ICC) and random-effects meta-analysis of their difference (Δg). A meta-regression investigated the association between clinician (dependent) and caregiver-rated SMDs (independent variable). Certainty in the evidence was evaluated using the GRADE approach. We identified 15 eligible placebo-controlled RCTs with 1567 participants, from which 13 included children/adolescents and 9 reported data for the pair of the clinician-rated Yale-Brown Obsessive Compulsive Scale (YBOCS) and the caregiver-rated Aberrant Behavior Checklist-Stereotypic Behavior (ABC-S). There was on average a good agreement between clinician- and caregiver-rated SMDs (ICC=0.84, 95% confidence intervals [0.55, 0.95]), no clear difference between them (Δg=0.08, 95%CI[-0.06, 0.21], 95% prediction intervals [-0.16, 0.31]), and the beta of the meta-regression was 0.62, 95%CI[0.27, 0.97]. The certainty of the evidence was low due to concerns in imprecision and inconsistency. Our analysis showed on average a good agreement between clinician- and caregiver-rated treatment effects in RRBs, yet discordance could be expected in future RCTs, given the wide prediction intervals. It is also not certain that these results could be generalizable to other rating scales and intervention modalities. Ethics committee approval: Not applicable as a meta-analysis of previously published studies..

Vasopressin receptor antagonists: a patent summary (2018-2022)

INTRODUCTION

Arginine-vasopressin hormone (AVP) is a key regulator in many essential physiological processes. The effect of AVP is mediated through three receptors within the body, these are the G protein-coupled vasopressin receptors, namely V1a, V1b (also called V3), and V2. Numerous studies investigated the role of these receptors in certain pathological conditions; therefore, stimulation or inhibition of these receptors may be a treatment option in these diseases.

AREAS COVERED

In this manuscript, the authors summarize recent patent activity (2018-2022) associated with vasopressin receptor antagonists (selective V1a or V2, and dual-acting V1a/V2), focusing mostly on chemical structures, their modifications, and potential clinical applications. Patent search was carried out using SciFinder, Espacenet, Patentscope, Cortellis Competitive Intelligence, and Derwent Innovation databases.

EXPERT OPINION

In recent years, vasopressin receptor antagonists have been in the spotlight of drug discovery, especially V1a selective molecules. Publishing balovaptan as a possible treatment for autism spectrum disorder (ASD), greatly increased the interest in CNS-acting vasopressin antagonists. In addition, peripherally active selective V2 and dual-acting V1a/V2 antagonists have also been developed. Although clinical trials were unsuccessful in many cases, there is still potential in the research of vasopressin receptor antagonists as shown by several currently ongoing clinical trials.