Pharmacogenetic Study of Serotonin Transporter and 5HT2A Genotypes in Autism

Off-label psychopharmacological interventions for autism spectrum disorders: strategic pathways for clinicians

The prevalence of autism spectrum disorder (ASD) continues to see a trend upward with a noticeable increase to 1 in 36 children less than 8 years of age in the recent MMWR. There are many factors linked to the substantially increased burden of seeking mental health services, and clinically these individuals are likely to present for impairments associated with co-occurring conditions. The advances in cutting-edge research and the understanding of co-occurring conditions in addition to psychosocial interventions have provided a window of opportunity for psychopharmacological interventions given the limited availability of therapeutics for core symptomatology. The off-label psychopharmacological treatments for these co-occurring conditions are central to clinical practice. However, the scattered evidence remains an impediment for practitioners to systematically utilize these options. The review collates the crucial scientific literature to provide stepwise treatment alternatives for individuals with ASD; with an aim to lead practitioners in making informed and shared decisions. There are many questions about the safety and tolerability of off-label medications; however, it is considered the best practice to utilize the available empirical data in providing psychoeducation for patients, families, and caregivers. The review also covers experimental medications and theoretical underpinnings to enhance further experimental studies. In summary, amidst the growing clinical needs for individuals with ASD and the lack of approved clinical treatments, the review addresses these gaps with a practical guide to appraise the risk and benefits of off-label medications.

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.

Pharmacogenomic Studies in Intellectual Disabilities and Autism Spectrum Disorder: A Systematic Review

BACKGROUND

Individuals with intellectual disability (ID) and autism spectrum disorder (ASD) often receive psychotropic medications such as antipsychotics and antidepressants to treat aberrant behaviors and mood symptoms, frequently resulting in polypharmacy and drug-related adverse effects. Pharmacogenomic (PGx) studies with ASD and/or ID (ASD/ID) have been scarce despite the promise of optimizing treatment outcomes. We reviewed the literature on PGx studies with antipsychotics and antidepressants (e.g., treatment response and adverse effects) in ASD/ID.

METHODS

We performed a systematic review using MEDLINE, Embase, and PsycINFO, including peer-reviewed original articles in English referring to PGx in the treatment of ASD/ID in any age groups (e.g., treatment response and adverse effects).

RESULTS

A total of 28 PGx studies using mostly candidate gene approaches were identified across age groups. Notably, only 3 studies included adults with ASD/ID while the other 25 studies focused specifically on children/adolescents with ASD/ID. Twelve studies primarily investigated treatment response, of which 5 and 6 studies included patients treated with antipsychotics and antidepressants, respectively. Most interesting results for response were reported for 2 sets of candidate gene studies, namely: (1) The DRD3 Ser9Gly (rs6280) polymorphism was examined in patients treated with risperidone in 3 studies, 2 of which reported an association with risperidone treatment response and (2) the SLC6A4 5-HTTLPR polymorphism and treatment response to antidepressants which was investigated in 4 studies, 3 of which reported significant associations. In regard to side effects, 9 of 15 studies focused on hyperprolactinemia in patients treated with risperidone. Among them, 7 and 5 studies examined the impact of CYP2D6 and DRD2 Taq1A polymorphisms, respectively, yielding mostly negative study findings.

CONCLUSIONS

There is limited data available on PGx in individuals with ASD/ID and in particular in adults. Given the potential for PGx testing in improving treatment outcomes, additional PGx studies for psychotropic treatment in ASD/ID across age groups are warranted.

Differential serotonin transporter (5-HTT) and 5-HT2 receptor density in limbic and neocortical areas of adults and children with autism spectrum disorders: implications for selective serotonin reuptake inhibitor efficacy

As selective serotonin reuptake inhibitors (SSRIs) are among the most commonly prescribed medications in autism, we aimed to determine whether targets for SSRIs are differentially affected in three cortical areas in children and adults with autism compared to neurotypical individuals. Utilizing a large cohort of postmortem brain tissue (n = 14–19 per group), saturation ligand binding assays were conducted on sections from the anterior cingulate cortex (ACC), posterior cingulate cortex, and fusiform gyrus (FG). Specific binding to the 5‐HT transporter (5‐HTT) as well as to 5‐HT2 and 1A receptors (5‐HT₂, 5‐HT_1A) was quantified in superficial and deep layers of each region using the ligands [³H]‐citalopram (5‐HTT), [³H]‐ketanserin (5‐HT₂), and [³H]‐8‐OH‐DPAT (5‐HT_1A). A Welch’s t‐test was utilized to compare receptor densities (B_max), revealing a statistically significant decrease in 5‐HTT within the ACC of the entire autism cohort. There was also a decrease in 5‐HT₂ receptor density in the ACC in the adult cohort, but not in child postmortem autism cases as compared to controls. Comparing linear regression lines of B_max values plotted against age, shows a significantly lower intercept for 5‐HTT in autism (p = 0.025). 5‐HT₂ density increases with age in control cases, whereas in autism there is a decrease with age and significantly different slopes between regression lines (p = 0.032). This suggests a deficit in 5‐HTT within the ACC in individuals with autism, while decreases in 5‐HT₂ density are age‐dependent. There were no differences in receptor densities in the posterior cingulate cortex or FG in autism and no differences in ligand affinity (K_D) across all regions and ligands examined.

Effect of Fluoxetine on Obsessive-Compulsive Behaviors in Children and Adolescents With Autism Spectrum Disorders: A Randomized Clinical Trial

IMPORTANCE

Selective serotonin receptor inhibitors are prescribed to reduce the severity of core behaviors of autism spectrum disorders, but their efficacy remains uncertain.

OBJECTIVE

To determine the efficacy of fluoxetine for reducing the frequency and severity of obsessive-compulsive behaviors in autism spectrum disorders.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, randomized, placebo-controlled clinical trial. Participants aged 7.5-18 years with autism spectrum disorders and a total score of 6 or higher on the Children's Yale-Brown Obsessive Compulsive Scale, modified for pervasive developmental disorder (CYBOCS-PDD) were recruited from 3 tertiary health centers across Australia. Enrollment began November 2010 and ended April 2017. Follow-up ended August 2017.

INTERVENTIONS

Participants were randomized to receive fluoxetine (n = 75) or placebo (n = 71). Study medication was commenced at 4 or 8 mg/d for the first week, depending on weight, and then titrated to a maximum dose of 20 or 30 mg/d over 4 weeks. Treatment duration was 16 weeks.

MAIN OUTCOMES AND MEASURES

The primary outcome was the total score on the CYBOCS-PDD (scores range from 0-20; higher scores indicate higher levels of maladaptive behaviors; minimal clinically important difference, 2 points) at 16 weeks postrandomization, analyzed with a linear regression model adjusted for stratification factors (site, age at baseline, and intellectual disability), with an additional prespecified model that included additional adjustment for baseline score, sex, communication level, and imbalanced baseline and demographic variables.

RESULTS

Among the 146 participants who were randomized (85% males; mean age, 11.2 years), 109 completed the trial; 31 in the fluoxetine group and 21 in the placebo group dropped out or did not complete treatment. The mean CYBOCS-PDD score from baseline to 16 weeks decreased in the fluoxetine group from 12.80 to 9.02 points (3.72-point decrease; 95% CI, -4.85 to -2.60) and in the placebo group from 13.13 to 10.89 points (2.53-point decrease; 95% CI, -3.86 to -1.19). The between-group mean difference at 16 weeks was -2.01 (95% CI, -3.77 to -0.25; P = .03) (adjusted for stratification factors), and in the prespecified model with further adjustment, it was -1.17 (95% CI, -3.01 to 0.67; P = .21).

CONCLUSIONS AND RELEVANCE

In this preliminary study of children and adolescents with autism spectrum disorders, treatment with fluoxetine compared with placebo resulted in significantly lower scores for obsessive-compulsive behaviors at 16 weeks. Interpretation is limited by the high dropout rate, null findings of prespecified analyses that accounted for potentially confounding factors and baseline imbalances, and CIs for the treatment effect that included the minimal clinically important difference.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12608000173392.

Pharmacogenomics of autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by persistent deficits in social communication and interactions as well as restricted, repetitive behaviors and interests. Pharmacologic interventions are often needed to manage irritability, aggressive behaviors and hyperactivity. Pharmacogenomic studies have investigated genetic associations with treatment response and side effects in an attempt to better understand drug mechanisms in hopes of optimizing the balance of symptom improvement versus side effects. The majority of pharmacogenomic studies to date have focused on antipsychotics, antidepressants and stimulants that are the most commonly utilized medication classes for ASD. This review is a comprehensive examination of the existing pharmacogenomic studies in ASD highlighting the current state of knowledge regarding genetic variation influencing pharmacokinetics and pharmacodynamics, and associated clinical outcomes.

Escitalopram pharmacogenetics: CYP2C19 relationships with dosing and clinical outcomes in autism spectrum disorder

BACKGROUND AND AIM

Selective serotonin reuptake inhibitors such as escitalopram are commonly used to treat patients with autism spectrum disorder (ASD), but there are individual differences in treatment response and tolerability. CYP2C19 encodes the primary enzyme responsible for escitalopram metabolism and we investigated whether polymorphisms in CYP2C19 were related to symptoms and dosing in a pharmacogenetic study of ASD.

PARTICIPANTS AND METHODS

Participants completed the Aberrant Behavior Checklist--Community Version (ABC-CV) weekly for 6 weeks. Escitalopram was initiated at a dose of 2.5 mg per day, with weekly increases to 20 mg unless intolerable side-effects occurred. Three CYP2C19 metabolizer groups, including ultrarapid, extensive, and reduced metabolizers, were examined in relation to symptom improvement and tolerated dose.

RESULTS

ABC-CV scores improved over the course of treatment (P<0.0001). No differences were identified in the rate of improvement across metabolizer groups for the ABC-CV irritability subscale, which was the primary outcome for clinical symptoms. There was a trend for a metabolizer group by time interaction with respect to dose (P=0.10). This interaction was driven by the linear rate of change from week 1 to study endpoint between the reduced metabolizers and ultrarapid metabolizer groups (P=0.05). Post-hoc analyses identified significant differences in the rate of dose escalation between ultrarapid metabolizers and extensive metabolizers and for ultrarapid metabolizers compared with reduced metabolizers (P's<0.04), whereby ultrarapid metabolizers showed a slower rate of change in dose over time.

CONCLUSION

CYP2C19 ultrarapid metabolizers were associated with reduced tolerance to a fixed titration schedule of open-label escitalopram in this ASD study sample. Possible explanations may involve the altered kinetics of faster metabolizers or previously unknown activities of escitalopram metabolites.