Pharmacogenetics of risperidone therapy in autism: association analysis of eight candidate genes with drug efficacy and adverse drug reactions

Influence of CYP2C19 and CYP2D6 on side effects of aripiprazole and risperidone: A systematic review

Variability in hepatic cytochrome P450 (CYP) enzymes such as 2C19 and 2D6 may influence side-effect and efficacy outcomes for antipsychotics. Aripiprazole and risperidone are two commonly prescribed antipsychotics, metabolized primarily through CYP2D6. Here, we aimed to provide an overview of the effect of CYP2C19 and CYP2D6 on side-effects of aripiprazole and risperidone, and expand on existing literature by critically examining methodological issues associated with pharmacogenetic studies. A PRISMA compliant search of six electronic databases (Pubmed, PsychInfo, Embase, Central, Web of Science, and Google Scholar) identified pharmacogenetic studies on aripiprazole and risperidone. 2007 publications were first identified, of which 34 were included. Quality of literature was estimated using Newcastle-Ottowa Quality Assessment Scale (NOS) and revised Cochrane Risk of Bias tool. The average NOS score was 5.8 (range: 3-8) for risperidone literature and 5 for aripiprazole (range: 4-6). All RCTs on aripiprazole were rated as high risk of bias, and four out of six for risperidone literature. Study populations ranged from healthy volunteers to inpatient individuals in psychiatric units and included adult and pediatric samples. All n = 34 studies examined CYP2D6. Only one study genotyped for CYP2C19 and found a positive association with neurological side-effects of risperidone. Most studies did not report any relationship between CYP2D6 and any side-effect outcome. Heterogeneity between and within studies limited the ability to synthesize data and draw definitive conclusions. Studies lacked statistical power due to small sample size, selective genotyping methods, and study design. Large-scale randomized trials with multiple measurements, providing robust evidence on this topic, are suggested.

The polymorphisms of candidate pharmacokinetic and pharmacodynamic genes and their pharmacogenetic impacts on the effectiveness of risperidone maintenance therapy among Saudi children with autism

BACKGROUND

Antipsychotics, including risperidone (RIS), are frequently indicated for various autism spectrum disorder (ASD) manifestations; however, "actionable" PGx testing in psychiatry regarding antipsychotic dosing and selection has limited applications in routine clinical practice because of the lack of standard guidelines, mostly due to the inconsistency and scarcity of genetic variant data. The current study is aimed at examining the association of RIS effectiveness, according to ABC-CV and CGI indexes, with relevant pharmacokinetics (PK) and pharmacodynamics (PD) genes.

METHODS

Eighty-nine ASD children who received a consistent RIS-based regimen for at least 8 weeks were included. The Axiom PharmacoFocus Array technique was employed to generate accurate star allele-predicted phenotypes of 3 PK genes (CYP3A4, CYP3A5, and CYP2D6). Genotype calls for 5 candidate PD receptor genes (DRD1, DRD2, DRD3, HTR2C, and HTR2A) were obtained and reported as wild type, heterozygous, or homozygous for 11 variants.

RESULTS

Based on the ABC total score, 42 (47.2%) children were classified as responders, while 47 (52.8%) were classified as nonresponders. Multivariate logistic regression analyses, adjusted for nongenetic factors, suggested nonsignificant impacts of the star allele-predicted phenotypes of all 3 PK genes on improvement in ASD symptoms or CGI scores. However, significant positive or negative associations of certain PD variants involved in dopaminergic and serotonergic pathways were observed with specific ASD core and noncore symptom subdomains. Our significant polymorphism findings, mainly those in DRD2 (rs1800497, rs1799978, and rs2734841), HTR2C (rs3813929), and HTR2A (rs6311), were largely consistent with earlier findings (predictors of RIS effectiveness in adult schizophrenia patients), confirming their validity for identifying ASD children with a greater likelihood of core symptom improvement compared to noncarriers/wild types. Other novel findings of this study, such as significant improvements in DRD3 rs167771 carriers, particularly in ABC total and lethargy/social withdrawal scores, and DRD1 rs1875964 homozygotes and DRD2 rs1079598 wild types in stereotypic behavior, warrant further verification in biochemical and clinical studies to confirm their feasibility for inclusion in a PGx panel.

CONCLUSION

In conclusion, we provide evidence of potential genetic markers involved in clinical response variability to RIS therapy in ASD children. However, replication in prospective samples with greater ethnic diversity and sample sizes is necessary.

Exploratory focused pharmacogenetic testing reveals novel markers associated with risperidone pharmacokinetics in Saudi children with autism

Background: Autism spectrum disorders (ASDs) encompass a broad range of phenotypes characterized by diverse neurological alterations. Genomic studies have revealed considerable overlap between the molecular mechanisms implicated in the etiology of ASD and genes involved in the pharmacokinetic (PK) and pharmacodynamic (PD) pathways of antipsychotic drugs employed in ASD management. Given the conflicting data originating from candidate PK or PD gene association studies in diverse ethnogeographic ASD populations, dosage individualization based on "actionable" pharmacogenetic (PGx) markers has limited application in clinical practice. Additionally, off-label use of different antipsychotics is an ongoing practice, which is justified given the shortage of approved cures, despite the lack of satisfactory evidence for its safety according to precision medicine. This exploratory study aimed to identify PGx markers predictive of risperidone (RIS) exposure in autistic Saudi children. Methods: This prospective cohort study enrolled 89 Saudi children with ASD treated with RIS-based antipsychotic therapy. Plasma levels of RIS and 9-OH-RIS were measured using a liquid chromatography-tandem mass spectrometry system. To enable focused exploratory testing, genotyping was performed with the Axiom PharmacoFocus Array, which included a collection of probe sets targeting PK/PD genes. A total of 720 PGx markers were included in the association analysis. Results: A total of 27 PGx variants were found to have a prominent impact on various RIS PK parameters; most were not located within the genes involved in the classical RIS PK pathway. Specifically, 8 markers in 7 genes were identified as the PGx markers with the strongest impact on RIS levels (p < 0.01). Four PGx variants in 3 genes were strongly associated with 9-OH-RIS levels, while 5 markers in 5 different genes explained the interindividual variability in the total active moiety. Notably, 6 CYP2D6 variants exhibited strong linkage disequilibrium; however, they significantly influenced only the metabolic ratio and had no considerable effects on the individual estimates of RIS, 9-OH-RIS, or the total active moiety. After correction for multiple testing, rs78998153 in UGT2B17 (which is highly expressed in the brain) remained the most significant PGx marker positively adjusting the metabolic ratio. For the first time, certain human leukocyte antigen (HLA) markers were found to enhance various RIS exposure parameters, which reinforces the gut-brain axis theory of ASD etiology and its suggested inflammatory impacts on drug bioavailability through modulation of the brain, gastrointestinal tract and/or hepatic expression of metabolizing enzymes and transporters. Conclusion: Our hypothesis-generating approach identified a broad spectrum of PGx markers that interactively influence RIS exposure in ASD children, which indicated the need for further validation in population PK modeling studies to define polygenic scores for antipsychotic efficacy and safety, which could facilitate personalized therapeutic decision-making in this complex neurodevelopmental condition.

Pharmacogenetics May Prevent Psychotropic Adverse Events in Autism Spectrum Disorder: An Observational Pilot Study

INTRODUCTION

Up to 73% of individuals with autism spectrum disorder (ASD) and intellectual disability (ID) currently have prescriptions for psychotropic drugs. This is explained by a higher prevalence of medical and psychiatric chronic comorbidities, which favors polypharmacy, increasing the probability of the appearance of adverse events (AEs). These could be a preventable cause of harm to patients with ASD and an unnecessary waste of healthcare resources.

OBJECTIVE

To study the impact of pharmacogenetic markers on the prevention of AE appearance in a population with ASD and ID.

METHODS

This is a cross-sectional, observational study (n = 118, 72 participants completed all information) in the ASD population. Sociodemographic and pharmacological data were gathered. The Udvalg for Kliniske Undersøgelser Scale (UKU Scale) was used to identify AEs related to the use of psychotropic medication. Polymorphisms of DOP2, ABCB1, and COMT were genotyped and correlated with the AE to find candidate genes. Furthermore, a review of all medications assessed in a clinical trial for adults with autism was performed to enrich the search for potential pharmacogenetic markers, keeping in mind the usual medications.

RESULTS

The majority of the study population were men (75%) with multiple comorbidities and polypharmacy, the most frequently prescribed drugs were antipsychotics (69%); 21% of the participants had four or more AEs related to psychotropic drugs. The most common were "Neurological" and" Psychiatric" (both 41%). Statistical analysis results suggested a significant correlation between the neurological symptoms and the DOP2 genotype, given that they are not equally distributed among its allelic variants. The final review considered 19 manuscripts of medications for adults with ASD, and the confirmed genetic markers for those medications were consulted in databases.

CONCLUSION

A possible correlation between neurologic AEs and polymorphisms of DOP2 was observed; therefore, studying this gene could contribute to the safety of this population's prescriptions. The following studies are underway to maximize statistical power and have a better representation of the population.

Is the CYP2D6 Genotype Associated with Antipsychotic-Induced Weight Gain?

Antipsychotic-induced weight gain (AIWG) is a serious adverse effect. Studies have linked genetically-predicted CYP2D6 metabolic capacity to AIWG. The evidence, however, is ambiguous. We performed multiple regression analyses examining the association between genetic-predicted CYP2D6 metabolic capacity and AIWG. Analyses were based on previously unpublished data from an RCT investigating the clinical utility of routine genotyping of CYP2D6 and CYP2C19 in patients with schizophrenia. A total of 211 patients, corresponding to 71% of the original study population, were included. Our analyses indicated an effect of genetically predicted CYP2D6 metabolic capacity on AIWG with significant weight gain in both CYP2D6 poor metabolizers (PMs) (4.00 kg (95% CI: 0.80; 7.21)) and ultrarapid metabolizers (UMs) (6.50 kg (95% CI: 1.03; 12.0)). This finding remained stable after adjustment for covariates (PMs: 4.26 kg (0.88; 7.64), UMs: 7.26 kg (1.24; 13.3)). In addition to the CYP2D6 metabolic capacity, both baseline body mass index (−0.24 (95% CI: −0.44; −0.03)) and chlorpromazine equivalents per day (0.0041 (95% CI: 0.0005; 0.0077)) were statistically significantly associated with weight change in the adjusted analysis. Our results support that the genetically predicted CYP2D6 metabolic capacity matters for AIWG.

Pharmacogenetic Interventions Improve the Clinical Outcome of Treatment-Resistant Autistic Spectrum Disorder Sufferers

BACKGROUND

Autistic spectrum disorders (ASD) are severe neurodevelopmental alterations characterised by deficits in social communication and repetitive and restricted behaviours. About a third of patients receive pharmacological treatment for comorbid symptoms. However, 30-50% do not respond adequately and/or present severe and long-lasting side effects.

METHODS

Genetic variants in CYP1A2, CYP2C19, CYP2D6 and SLC6A4 were investigated in N = 42 ASD sufferers resistant to pharmacological treatment. Clinical recommendations based on their pharmacogenetic profiles were provided within 24-48 h of receiving a biological sample.

RESULTS

A total of 39 participants (93%) improved after the pharmacogenetic intervention according to their CGI scores (difference in basal-final scores: 2.26, SD 1.55) and 37 participants (88%) according to their CGAS scores (average improvement of 20.29, SD 11.85). Twenty-three of them (55%) achieved symptom stability (CGI ≤ 3 and CGAS improvement ≥ 20 points), requiring less frequent visits to their clinicians and hospital stays. Furthermore, the clinical improvement was higher than that observed in a control group (N = 62) with no pharmacogenetic interventions, in which 66% responded to treatment (difference in CGI scores: -0.87, SD 9.4, p = 1 × 10-5; difference in CGAS scores: 6.59, SD 7.76, p = 5 × 10-8).

CONCLUSIONS

The implementation of pharmacogenetic interventions has the potential to significantly improve the clinical outcomes in severe comorbid ASD populations with drug treatment resistance and poor prognosis.

HKG: an open genetic variant database of 205 Hong Kong cantonese exomes

HKG is the first fully accessible variant database for Hong Kong Cantonese, constructed from 205 novel whole-exome sequencing data. There has long been a research gap in the understanding of the genetic architecture of southern Chinese subgroups, including Hong Kong Cantonese. HKG detected 196 325 high-quality variants with 5.93% being novel, and 25 472 variants were found to be unique in HKG compared to three Chinese populations sampled from 1000 Genomes (CHN). PCA illustrates the uniqueness of HKG in CHN, and the admixture study estimated the ancestral composition of HKG and CHN, with a gradient change from north to south, consistent with their geological distribution. ClinVar, CIViC and PharmGKB annotated 599 clinically significant variants and 360 putative loss-of-function variants, substantiating our understanding of population characteristics for future medical development. Among the novel variants, 96.57% were singleton and 6.85% were of high impact. With a good representation of Hong Kong Cantonese, we demonstrated better variant imputation using reference with the addition of HKG data, thus successfully filling the data gap in southern Chinese to facilitate the regional and global development of population genetics.

CYP2D6 Genetic Variation and Antipsychotic-Induced Weight Gain: A Systematic Review and Meta-Analysis

BACKGROUND

Antipsychotic-induced weight gain is a contributing factor in the reduced life expectancy reported amongst people with psychotic disorders. CYP2D6 is a liver enzyme involved in the metabolism of many commonly used antipsychotic medications. We investigated if CYP2D6 genetic variation influenced weight or BMI among people taking antipsychotic treatment.

METHODS

We conducted a systematic review and a random effects meta-analysis of publications in Pubmed, Embase, PsychInfo, and CENTRAAL that had BMI and/or weight measurements of patients on long-term antipsychotics by their CYP2D6-defined metabolic groups (poor, intermediate, normal/extensive, and ultra-rapid metabolizers, UMs).

RESULTS

Twelve studies were included in the systematic review. All cohort studies suggested that the presence of reduced-function or non-functional alleles for CYP2D6 was associated with greater antipsychotic-induced weight gain, whereas most cross-sectional studies did not find any significant associations. Seventeen studies were included in the meta-analysis with clinical data of 2,041 patients, including 93 poor metabolizers (PMs), 633 intermediate metabolizers (IMs), 1,272 normal metabolizers (NMs), and 30 UMs. Overall, we did not find associations in any of the comparisons made. The estimated pooled standardized differences for the following comparisons were (i) PM versus NM; weight = -0.07 (95%CI: -0.49 to 0.35, p = 0.74), BMI = 0.40 (95%CI: -0.19 to 0.99, p = 0.19). (ii) IM versus NM; weight = 0.09 (95% CI: -0.04 to 0.22, p = 0.16) and BMI = 0.09 (95% CI: -0.24 to 0.41, p = 0.60). (iii) UM versus EM; weight = 0.01 (95% CI: -0.37 to 0.40, p = 0.94) and BMI = -0.08 (95%CI: -0.57 to 0.42, p = 0.77).

CONCLUSION

Our systematic review of cohort studies suggested that CYP2D6 poor metabolizers have higher BMI than normal metabolizers, but the data of cross-sectional studies and the meta-analysis did not show this association. Although our review and meta-analysis constitutes one of the largest studies with comprehensively genotyped samples, the literature is still limited by small numbers of participants with genetic variants resulting in poor or UMs status. We need further studies with larger numbers of extreme metabolizers to establish its clinical utility in antipsychotic treatment. CYP2D6 is a key gene for personalized prescribing in mental health.

Dopamine D3 Receptor, Cognition and Cognitive Dysfunctions in Neuropsychiatric Disorders: From the Bench to the Bedside

The dopamine D3 receptor (D3R) plays a prominent role in the modulation of cognition in healthy individuals, as well as in the pathophysiological mechanism underlying the cognitive deficits affecting patients suffering from neuropsychiatric disorders. At a therapeutic level, a growing body of evidence suggests that the D3R blockade enhances cognitive and thus it may be an optimal therapeutic strategy against cognitive dysfunctions. However, this is not always the case because other ligands targeting the D3R, and behaving as partial agonists or biased agonists, may exert their pro-cognitive effect by maintaining adequate level of dopamine in key brain areas tuning cognitive performances. In this chapter, we review and discuss preclinical and clinical findings with the aim to remark the crucial role of the D3R in cognition and to strengthen the message that drugs targeting D3R may be excellent cognitive enhancers for the treatment of several neuropsychiatric and neurological disorders.

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.

The Influence of CYP2D6 and CYP2C19 Genetic Variation on Diabetes Mellitus Risk in People Taking Antidepressants and Antipsychotics

CYP2D6 and CYP2C19 enzymes are essential in the metabolism of antidepressants and antipsychotics. Genetic variation in these genes may increase risk of adverse drug reactions. Antidepressants and antipsychotics have previously been associated with risk of diabetes. We examined whether individual genetic differences in CYP2D6 and CYP2C19 contribute to these effects. We identified 31,579 individuals taking antidepressants and 2699 taking antipsychotics within UK Biobank. Participants were classified as poor, intermediate, or normal metabolizers of CYP2D6, and as poor, intermediate, normal, rapid, or ultra-rapid metabolizers of CYP2C19. Risk of diabetes mellitus represented by HbA1c level was examined in relation to the metabolic phenotypes. CYP2D6 poor metabolizers taking paroxetine had higher Hb1Ac than normal metabolizers (mean difference: 2.29 mmol/mol; p < 0.001). Among participants with diabetes who were taking venlafaxine, CYP2D6 poor metabolizers had higher HbA1c levels compared to normal metabolizers (mean differences: 10.15 mmol/mol; p < 0.001. Among participants with diabetes who were taking fluoxetine, CYP2D6 intermediate metabolizers and decreased HbA1c, compared to normal metabolizers (mean difference -7.74 mmol/mol; p = 0.017). We did not observe any relationship between CYP2D6 or CYP2C19 metabolic status and HbA1c levels in participants taking antipsychotic medication. Our results indicate that the impact of genetic variation in CYP2D6 differs depending on diabetes status. Although our findings support existing clinical guidelines, further research is essential to inform pharmacogenetic testing for people taking antidepressants and antipsychotics.

Pharmacogenomics Factors Influencing the Effect of Risperidone on Prolactin Levels in Thai Pediatric Patients With Autism Spectrum Disorder

We investigated the association between genetic variations in pharmacodynamic genes and risperidone-induced increased prolactin levels in children and adolescents with autism spectrum disorder (ASD). In a retrospective study, variants of pharmacodynamic genes were analyzed in 124 ASD patients treated with a risperidone regimen for at least 3 months. To simplify genotype interpretation, we created an algorithm to calculate the dopamine D2 receptor (DRD2) gene genetic risk score. There was no relationship between prolactin levels and single SNPs. However, the H1/H3 diplotype (A2/A2-Cin/Cin-A/G) of DRD2/ankyrin repeat and kinase domain containing 1 (ANKK1) Taq1A, DRD2 -141C indel, and DRD2 -141A>G, which had a genetic risk score of 5.5, was associated with the highest median prolactin levels (23 ng/ml). As the dose-corrected plasma levels of risperidone, 9-OH-risperidone, and the active moiety increased, prolactin levels in patients carrying the H1/H3 diplotype were significantly higher than those of the other diplotypes. DRD2 diplotypes showed significantly high prolactin levels as plasma risperidone levels increased. Lower levels of prolactin were detected in patients who responded to risperidone. This is the first system for describing DRD2 haplotypes using genetic risk scores based on their protein expression. Clinicians should consider using pharmacogenetic-based decision-making in clinical practice to prevent prolactin increase.

Current strategies for predicting side effects from second generation antipsychotics in youth

Introduction: Antipsychotic medications are used to treat a number of conditions in children and adolescents. While side effect profiles from second generation antipsychotics (SGAs) may differ from older antipsychotics, they do not come without risk. Knowing which children may be at higher risk for specific outcomes is important clinical information for prescribers. Common side effects and toxicities of SGAs in children include movement disorders, weight gain, and hormonal changes. There are also rare, but potentially dangerous adverse events including neuroleptic malignant syndrome, hypersensitivity and suicidal ideation.Areas covered: This review will summarize and comment on clinical, pharmacological, and genetic factors having evidence as predictors of SGA-associated side effects and toxicities in children.Expert opinion: Observations across studies note that older children and those that do not respond early in treatment may be more at risk for movement disorders, while younger, antipsychotic naive children are at increased risk for weight gain. Relatively fewer studies have looked at pharmacogenetic relationships, although variations in pharmacokinetic and pharmacodynamic genes hold promise to advance drug dosing or selection strategies. Future efforts to assimilate multiple clinical, pharmacological, and genetic factors to facilitate predictive analytics and clinical decision support for prescribers will advance precision care to patients.

An Update on Precision Medicine Advances In Neurodevelopmental Disorders

Neurodevelopmental disorders, including autism spectrum disorder (ASD) and attention-deficit/hyper-activity disorder (ADHD), represent a group of conditions that manifest early in child development and produce impairments across multiple domains of functioning. Although a number of pharmacological and psychosocial treatments exist to improve the symptoms associated with these syndromes, treatment advances have lagged. The Precision Medicine Initiative was launched with the goal of revolutionizing medicine by progressing beyond the historical one-size-fits-all approach. In this review, we evaluate current research efforts to personalize treatments for ASD and ADHD. Most pharmacogenetic testing has focused on the cytochrome P450 enzyme family with a particular focus on CYP2D6 and CYP2C19, which are genes that produce an enzyme that acts as a key metabolizer of many prescribed medications. This article provides an update on the state of the field of pharmacogenetics and "therapy-genetics" in the context of ASD and ADHD, and it also encourages clinicians to follow US Food and Drug Administration recommendations regarding pharmacogenetic testing.

Evidence for Pharmacogenomic Effects on Risperidone Outcomes in Pediatrics

OBJECTIVE

To determine the association between genetic variants reported to affect risperidone and adverse events (AEs) in children and adolescents.

METHODS

Individuals aged 18 years or younger with ≥4 weeks of risperidone exposure in a deidentified DNA biobank were included. The primary outcome was AE frequency as a function of genotype. Individuals were classified according to metabolizer status for CYP2D6, CYP3A4, and CYP3A5; wild type, heterozygote, or homozygote for specific single nucleotide variants for DRD2, DRD3, HTR2A, and HTR2C; and wild type versus nonwild type for multiple uncommon variants in ABCG2, ABCB1, and HTR2C. Tests of association of each classification to AEs were performed using a Fisher exact test and logistic regression, and statistically significant classifications were included in a final logistic regression.

RESULTS

The final cohort included 257 individuals. AEs were more common in CYP2D6 poor/intermediate metabolizers (PMs/IMs) than normal/rapid/ultrarapid metabolizers (NMs/RMs/UMs) in univariate and multivariate analysis. HTR2A-rs6311 heterozygotes and homozygotes had fewer AEs than wild types in logistic regression but not in univariate analysis. In the final multivariable model adjusting for age, race, sex, and risperidone dose, AEs were associated with CYP2D6 (adjusted odds ratio [AOR] 2.6, 95% CI 1.1-5.5, for PMs/IMs vs. NMs/RMs/UMs) and HTR2A-rs6311 (AOR 0.6, 95% CI 0.4-0.9, for each variant allele), both consistent with previous studies.

CONCLUSION

Children and adolescents who are CYP2D6 PMs/IMs may have an increased risk for risperidone AEs. Of the genes and variants studied, only CYP2D6 has consistent association and sufficient data for clinical use, whereas HTR2A-rs6311 has limited data and requires further study.

CYP2D6 and Antipsychotic Treatment Outcomes in Children and Youth: A Systematic Review

Objective: To systematically review the impact of CYP2D6 genetic variation on antipsychotic pharmacokinetics, efficacy, and adverse drug reactions among children and youth. Method: The published literature was systematically searched in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations and critically evaluated using standardized tools and consensus criteria. Results: A total of 20 eligible studies comprising 1078 children and youth were evaluated. The included studies were of fair to moderate quality and included mostly males, individuals of European ancestry, and those treated with risperidone. CYP2D6 poor metabolizers (PMs) were consistently shown to have increased concentrations of risperidone relative to normal metabolizers (NMs). PMs were also consistently shown to have a greater propensity to experience antipsychotic (primarily risperidone) associated adverse drug reactions relative to NMs. However, robust evidence for an association between CYP2D6 and efficacy was less apparent. Conclusion and Clinical Significance: The current knowledge base suggests that CYP2D6 genetic variation has an appreciable impact on antipsychotic pharmacokinetics and the propensity for adverse drug reactions, particularly among children receiving risperidone treatment. However, several limitations with the current literature (e.g., sample sizes, study design, sample heterogeneity) should be addressed in future studies. Assuming that future studies support the link between CYP2D6 genetic variation and antipsychotic outcomes, we would anticipate an increase in the implementation of CYP2D6-guided antipsychotic drug selection and dose optimization in child and adolescent psychiatric services.

Effects of Risperidone in Autistic Children and Young Adults: A Systematic Review and Meta-Analysis

There are several studies investigating the effects of risperidone on autism, but many of these studies are contradictory or inconclusive. This systematic review and meta-analysis investigated the effects of risperidone on five domains of the Aberrant Behaviour Checklist (ABC) scale on Autism Spectrum Disorder (ASD), as well as weight gain and waist circumference. The protocol for the present systematic review and meta-analysis was registered on the International Prospective Register of Systematic Reviews (PROSPERO). For this study, we analysed articles (2,459), selecting them according to the PICOS strategy (Population, Intervention, Comparison, Outcome, Study design). Although risperidone is effective for the treatment of lethargy and inadequate speech, concerns about the association between weight gain, waist circumference and risperidone require a need for evaluation of the risk-benefit ratio in its use. There was a significant association between weight gain, waist circumference and risperidone. In conclusion, it was possible to suggest the efficacy of risperidone for the treatment of lethargy and inadequate speech. Finally, we emphasize that the risk-benefit in its use should be evaluated (Protocol number CRD42019122316).

Pharmacogenetics of antipsychotics: Clinical utility and implementation

Decades of research have produced extensive evidence of the contribution of genetic factors to the efficacy and toxicity of antipsychotics. Numerous genetic variants in genes controlling drug availability or involved in antipsychotic processes have been linked to treatment variability. The complex mechanism of action and multitarget profile of most antipsychotic drugs hinder the identification of pharmacogenetic markers of clinical value. Nevertheless, the validity of associations between variants in CYP1A2, CYP2D6, CYP2C19, ABCB1, DRD2, DRD3, HTR2A, HTR2C, BDNF, COMT, MC4R genes and antipsychotic response has been confirmed in independent candidate gene studies. Genome wide pharmacogenomic studies have proven the role of the glutamatergic pathway in mediating antipsychotic activity and have reported novel associations with antipsychotic response. However, only a limited number of the findings, mainly functional variants of CYP metabolic enzymes, have been shown to be of clinical utility and translated into useful pharmacogenetic markers. Based on the currently available information, actionable pharmacogenetics should be reduced to antipsychotics' dose adjustment according to the genetically predicted metabolic status (CYPs' profile) of the patient. Growing evidence suggests that such interventions will reduce antipsychotics' side-effects and increase treatment safety. Despite this evidence, the use of pharmacogenetics in psychiatric wards is minimal. Hopefully, further evidence on the clinical and economic benefits, the development of clinical protocols based on pharmacogenetic information, and improved and cheaper genetic testing will increase the implementation of pharmacogenetic guided prescription in clinical settings.

Risperidone plasma concentrations are associated with side effects and effectiveness in children and adolescents with autism spectrum disorder

AIM

Risperidone is the most commonly prescribed antipsychotic drug to children and adolescents worldwide, but it is associated with serious side effects, including weight gain. This study assessed the relationship of risperidone and 9-hydroxyrisperidone trough concentrations, maximum concentrations and 24-hour area under the curves (AUCs) with body mass index (BMI) z-scores in children and adolescents with autism spectrum disorder (ASD) and behavioural problems. Secondary outcomes were metabolic, endocrine, extrapyramidal and cardiac side effects and effectiveness.

METHODS

Forty-two children and adolescents (32 males) aged 6-18 years were included in a 24-week prospective observational trial. Drug plasma concentrations, side effects and effectiveness were measured at several time points during follow-up. Relevant pharmacokinetic covariates, including medication adherence and CYP2D6, CYP3A4, CYP3A5 and P-glycoprotein (ABCB1) genotypes, were measured. Nonlinear mixed-effects modelling (NONMEM®) was used for a population pharmacokinetic analysis with 205 risperidone and 205 9-hydroxyrisperidone concentrations. Subsequently, model-based trough concentrations, maximum concentrations and 24-hour AUCs were analysed to predict outcomes using generalized and linear mixed-effects models.

RESULTS

A risperidone two-compartment model combined with a 9-hydroxyrisperidone one-compartment model best described the measured concentrations. Of all the pharmacokinetic parameters, higher risperidone sum trough concentrations best predicted higher BMI z-scores during follow-up (P < .001). Higher sum trough concentrations also predicted more sedation (P < .05), higher prolactin levels (P < .001) and more effectiveness measured with Aberrant Behavior Checklist irritability score (P < .01).

CONCLUSION

Our results indicate a therapeutic window exists, which suggests that therapeutic drug monitoring of risperidone might increase safety and effectiveness in children and adolescents with ASD and behavioural problems.

Association of Genetic Variants of Dopamine and Serotonin In Schizophrenia

BACKGROUND

Several studies indicated that antipsychotic treatment response and side effect manifestation can be different due to inter-individual variability in genetic variations.

AIM OF THE STUDY

Here we perform a case-control study to explore a potential association between schizophrenia and variants within the antipsychotic drug molecular targets (DRD1, DRD2, DRD3, HTR2A, HTR6) and metabolizing enzymes (CYP2D6, COMT) genes in Armenian population including also analysis of their possible relationship with disease clinical symptoms.

METHODS

A total of 18 SNPs was studied in patients with schizophrenia (n = 78) and healthy control subjects (n = 77) using MassARRAY genotyping.

RESULTS

We found that two studied genetic variants, namely DRD2 rs4436578*C and HTR2A rs6314*A are underrepresented in the group of patients compared to healthy subjects. After the correction for multiple testing, the rs4436578*C variant remained significant while the rs6314*A reported borderline significance. No significant differences in minor allele frequencies for other studied variants were identified. Also, a relationship between the genotypes and age of onset as well as disease duration has been detected.

CONCLUSIONS

The DRD2 rs4436578*C genetic variant might have protective role against schizophrenia, at least in Armenians.

Pharmacogenomic Characterization in Bipolar Spectrum Disorders

The holistic approach of personalized medicine, merging clinical and molecular characteristics to tailor the diagnostic and therapeutic path to each individual, is steadily spreading in clinical practice. Psychiatric disorders represent one of the most difficult diagnostic challenges, given their frequent mixed nature and intrinsic variability, as in bipolar disorders and depression. Patients misdiagnosed as depressed are often initially prescribed serotonergic antidepressants, a treatment that can exacerbate a previously unrecognized bipolar condition. Thanks to the use of the patient's genomic profile, it is possible to recognize such risk and at the same time characterize specific genetic assets specifically associated with bipolar spectrum disorder, as well as with the individual response to the various therapeutic options. This provides the basis for molecular diagnosis and the definition of pharmacogenomic profiles, thus guiding therapeutic choices and allowing a safer and more effective use of psychotropic drugs. Here, we report the pharmacogenomics state of the art in bipolar disorders and suggest an algorithm for therapeutic regimen choice.

Prediction of Response to Drug Therapy in Psychiatric Disorders

Reprinted with permission from Open Biol. 8: 180031. The Royal Society.

Association of dopamine D2 receptor gene polymorphisms with prolactin levels related to risperidone treatment: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Dopamine D₂ receptor (DRD2) polymorphisms are inconsistently associated with elevated prolactin levels related to risperidone treatment. The aim of this systematic review and meta-analysis was to investigate whether DRD2 polymorphisms could modulate prolactin levels in patients treated with risperidone.

METHODS

Three electronic databases (PubMed, EMBASE and the Cochrane Library) were searched for studies investigating the effect of DRD2 polymorphisms on prolactin levels in patients treated with risperidone until May 2018. Summary standard mean differences (SMDs) and 95% confidence intervals (CIs) were calculated with Hedges' g tests for effect estimates using random effects models. The heterogeneity, sensitivity, univariable meta-regression, subgroup analyses and publication biases were calculated.

RESULTS AND DISCUSSION

After initially identifying 886 studies, 772 patients from eight studies were included. Summary SMDs indicated that compared with A1 non-carriers, Taq1A A1 carriers did not have different risperidone-related prolactin levels (SMD: 0.13; 95% CI: -0.18 to 0.43; P = 0.423) among patients with schizophrenia (SCZ; SMD: 0.07; 95% CI: -0.14 to 0.29; P = 0.505) or among those without SCZ (SMD: 0.16; 95% CI: -0.39 to 0.71; P = 0.562). There was no significant difference between Del carriers and Del non-carriers with regard to risperidone-related prolactin levels (SMD: -0.00; 95% CI: -0.59 to 0.58; P = 0.996). In an Asian subgroup analysis, we also noted that compared with Taq1A A1A2 carriers, Taq1A A1A1 carriers had lower prolactin levels (SMD: -0.34; 95% CI: -0.66 to -0.02; P = 0.040). However, there was no significant difference in prolactin levels between A1A1 carriers and A2A2 carriers (SMD: -0.27; 95% CI: -0.60 to 0.05; P = 0.098), or between A2 carriers and A2 non-carriers (SMD: 0.29; 95% CI: -0.01 to 0.59; P = 0.059). Based on univariable meta-regression analyses, the effects of publication year, study design, ethnicity, comparison groups and study quality could bias the identified association of DRD2 Taq1A with risperidone-related prolactin levels.

WHAT IS NEW AND CONCLUSION

The findings of this study suggest that there is no significant difference between Taq1A A1 carriers and non-A1 carriers with regard to risperidone-related prolactin levels. As there were few A1 homozygotes, large prospective studies with robust designs are still needed to investigate whether A1A1 could affect risperidone-related prolactin levels in the Asian population.

CYP2D6 genotype and adverse events to risperidone in children and adolescents

BACKGROUND

There are few and conflicting data on the role of cytochrome P450 2D6 (CYP2D6) polymorphisms in relation to risperidone adverse events (AEs) in children. This study assessed the association between CYP2D6 metabolizer status and risk for risperidone AEs in children.

METHODS

Children ≤18 years with at least 4 weeks of risperidone exposure were identified using BioVU, a de-identified DNA biobank linked to electronic health record data. The primary outcome of this study was AEs. After DNA sequencing, individuals were classified as CYP2D6 poor, intermediate, normal, or ultrarapid CYP2D6 metabolizers.

RESULTS

For analysis, the 257 individuals were grouped as poor/intermediate metabolizers (n = 33, 13%) and normal/ultrarapid metabolizers (n = 224, 87%). AEs were more common in poor/intermediate vs. normal/ultrarapid metabolizers (15/33, 46% vs. 61/224, 27%, P = 0.04). In multivariate analysis adjusting for age, sex, race, and initial dose, poor/intermediate metabolizers had increased AE risk (adjusted odds ratio 2.4, 95% confidence interval 1.1-5.1, P = 0.03).

CONCLUSION

Children with CYP2D6 poor or intermediate metabolizer phenotypes are at greater risk for risperidone AEs. Pre-prescription genotyping could identify this high-risk subset for an alternate therapy, risperidone dose reduction, and/or increased monitoring for AEs.

Prediction of response to drug therapy in psychiatric disorders

Personalized medicine has become increasingly relevant to many medical fields, promising more efficient drug therapies and earlier intervention. The development of personalized medicine is coupled with the identification of biomarkers and classification algorithms that help predict the responses of different patients to different drugs. In the last 10 years, the Food and Drug Administration (FDA) has approved several genetically pre-screened drugs labelled as pharmacogenomics in the fields of oncology, pulmonary medicine, gastroenterology, haematology, neurology, rheumatology and even psychiatry. Clinicians have long cautioned that what may appear to be similar patient-reported symptoms may actually arise from different biological causes. With growing populations being diagnosed with different psychiatric conditions, it is critical for scientists and clinicians to develop precision medication tailored to individual conditions. Genome-wide association studies have highlighted the complicated nature of psychiatric disorders such as schizophrenia, bipolar disorder, major depression and autism spectrum disorder. Following these studies, association studies are needed to look for genomic markers of responsiveness to available drugs of individual patients within the population of a specific disorder. In addition to GWAS, the advent of new technologies such as brain imaging, cell reprogramming, sequencing and gene editing has given us the opportunity to look for more biomarkers that characterize a therapeutic response to a drug and to use all these biomarkers for determining treatment options. In this review, we discuss studies that were performed to find biomarkers of responsiveness to different available drugs for four brain disorders: bipolar disorder, schizophrenia, major depression and autism spectrum disorder. We provide recommendations for using an integrated method that will use available techniques for a better prediction of the most suitable drug.

A systematic review of the effects of CYP2D6 phenotypes on risperidone treatment in children and adolescents

The second generation antipsychotic drug risperidone is widely used in the field of child and adolescent psychiatry to treat conditions associated with disruptive behavior, aggression and irritability, such as autism spectrum disorders. While risperidone can provide symptomatic relief for many patients, there is considerable individual variability in the therapeutic response and side-effect profile of the medication. One well established biological factor that contributes to these individual differences is genetic variation in the cytochrome P450 enzyme 2D6. The 2D6 enzyme metabolizes risperidone and therefore affects drug levels and dosing. In the present review, we summarize the current literature on 2D6 variants and their effects on risperidone responses, specifically in children and adolescents. Relevant articles were identified through systematic review, and after irrelevant articles were discarded, ten studies were included in the review. Most prospective studies were well controlled, but often did not have a large enough sample size to make robust statements about rarer variants, including those categorized as ultra-rapid and poor metabolizers. Individual studies demonstrated a role for different genetic variants in risperidone drug efficacy, pharmacokinetics, hyperprolactinemia, weight gain, extrapyramidal symptoms and drug-drug interactions. Where studies overlapped in measurements, there was typically a consensus between results. These findings indicate that the value of 2D6 genotyping in the youth population treated with risperidone requires further study, in particular with the less common variants.

Impact of NTRK2, DRD2 and ACE polymorphisms on prolactin levels in antipsychotic-treated patients with first-episode psychosis

BACKGROUND

Hyperprolactinemia is a common side-effect of antipsychotics (APs), which may trigger serious secondary problems and compromise the adherence to treatment which is crucial for prognosis, especially in patients presenting with a first-episode of psychosis (FEP).

AIMS

We evaluated, in some cases for the first time, the effect of polymorphisms in multiple candidate genes on serum prolactin (PRL) levels in an AP-treated FEP cohort recruited in the multicenter PEPs study (Phenotype - genotype and environmental interaction; Application of a predictive model in first psychotic episodes).

METHODS

PRL concentration was measured in serum from 222 patients. A total of 167 polymorphisms were selected in 23 genes. Genetic association analysis was performed in the whole sample and also in homogenous subgroups of patients treated with APs with a high (N = 101) or low risk (N = 95) of increasing PRL release, which showed significant differences in their PRL levels.

RESULTS

After Bonferroni correction, polymorphisms in NTRK2, DRD2 and ACE genes were associated with PRL concentration.

CONCLUSION

Our results give more support to the impact of DRD2, but also of other genes related to dopamine availability such as ACE. Moreover, this study provides the first evidence for the involvement of NTRK2, which suggests that pathways other than the ones related to dopamine or serotonin may participate in the AP-related PRL levels.

Clinical Pharmacogenetics of Cytochrome P450-Associated Drugs in Children

Cytochrome P450 (CYP) enzymes are commonly involved in drug metabolism, and genetic variation in the genes encoding CYPs are associated with variable drug response. While genotype-guided therapy has been clinically implemented in adults, these associations are less well established for pediatric patients. In order to understand the frequency of pediatric exposures to drugs with known CYP interactions, we compiled all actionable drug-CYP interactions with a high level of evidence using Clinical Pharmacogenomic Implementation Consortium (CPIC) data and surveyed 10 years of electronic health records (EHR) data for the number of children exposed to CYP-associated drugs. Subsequently, we performed a focused literature review for drugs commonly used in pediatrics, defined as more than 5000 pediatric patients exposed in the decade-long EHR cohort. There were 48 drug-CYP interactions with a high level of evidence in the CPIC database. Of those, only 10 drugs were commonly used in children (ondansetron, oxycodone, codeine, omeprazole, lansoprazole, sertraline, amitriptyline, citalopram, escitalopram, and risperidone). For these drugs, reports of the drug-CYP interaction in cohorts including children were sparse. There are adequate data for implementation of genotype-guided therapy for children for three of the 10 commonly used drugs (codeine, omeprazole and lansoprazole). For the majority of commonly used drugs with known CYP interactions, more data are required to support pharmacogenomic implementation in children.

Bridging Autism Spectrum Disorders and Schizophrenia through inflammation and biomarkers - pre-clinical and clinical investigations

In recent years, evidence supporting a link between inflammation and neuropsychiatric disorders has been mounting. Autism spectrum disorders (ASD) and schizophrenia share some clinical similarities which we hypothesize might reflect the same biological basis, namely, in terms of inflammation. However, the diagnosis of ASD and schizophrenia relies solely on clinical symptoms, and to date, there is no clinically useful biomarker to diagnose or monitor the course of such illnesses.

The focus of this review is the central role that inflammation plays in ASD and schizophrenia. It spans from pre-clinical animal models to clinical research and excludes in vitro studies. Four major areas are covered: (1) microglia, the inflammatory brain resident myeloid cells, (2) biomarkers, including circulating cytokines, oxidative stress markers, and microRNA players, known to influence cellular processes at brain and immune levels, (3) effect of anti-psychotics on biomarkers and other predictors of response, and (4) impact of gender on response to immune activation, biomarkers, and response to anti-psychotic treatments.

Pharmacogenomics and Efficacy of Risperidone Long-Term Treatment in Thai Autistic Children and Adolescents

The purpose of this study was to evaluate the association of pharmacogenomic factors and clinical outcome in autistic children and adolescents who were treated with risperidone for long periods. Eighty-two autistic subjects diagnosed with DSM-IV and who were treated with risperidone for more than 1 year were recruited. Pharmacogenomics and clinical outcome (CGI-I, aggressive, overactivity and repetitive score) were evaluated. Almost all patients showed stable symptoms on aggressive behaviour (89.02%), overactivity (71.95%), repetitive (70.89%) behaviour and all clinical symptoms (81.71%). Only 4.48% of patients showed minimally worse CGI-I score. Patients in the non-stable symptom group had DRD2 Taq1A non-wild-type (TT and CT) frequencies higher than the clinically stable group (p = 0.04), whereas other gene polymorphisms showed no significant association. Haplotype ACCTCAT (rs6311, rs1045642, rs1128503, rs1800497, rs4436578, rs1799978, rs6280) showed a significant association with non-stable clinical outcome (χ²  = 6.642, p = 0.010). Risperidone levels showed no association with any clinical outcome. On the other hand, risperidone dose, 9-OH risperidone levels and prolactin levels were significantly higher in the non-stable compared to the stable symptom group (p = 0.013, p = 0.044, p = 0.030). Increased appetite was the most common adverse drug reaction and associated with higher body-weight, whereas it was not significantly associated with genetic variations and non-genetic information. In conclusion, risperidone showed efficacy to control autism, especially aggressive symptoms in long-term treatment. However, Taq1A T - carrier of dopamine 2 receptor gene - is associated with non-stable response in risperidone-treated patients. This study supports pharmacogenomics testing for personalized therapy with risperidone in autistic children and adolescents.

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.

Risperidone-Induced Adverse Drug Reactions and Role of DRD2 (-141 C Ins/Del) and 5HTR2C (-759 C>T) Genetic Polymorphisms in Patients with Schizophrenia

OBJECTIVE

To determine the adverse drug reaction (ADR) profile of risperidone and their association with dopamine (DRD2 - 141 C Ins/Del/rs1799732) and serotonin receptor (5HTR2C -759 C>T/rs3813929) gene polymorphisms in patients with schizophrenia.

MATERIALS AND METHODS

The study was conducted among 289 patients who were diagnosed with schizophrenia and were on treatment with risperidone (4-8 mg/day)-based therapy for a minimum of 4 weeks. Genotyping was carried by real-time quantitative polymerase chain reaction. All the patients were observed for the occurrences of ADRs during the study. Changes in prolactin levels and body weight were analyzed for a subgroup of 102 and 97 patients, respectively.

RESULTS

Risperidone-induced extrapyramidal symptoms (EPSs) were seen in 36.7% of patients. Among them, tremors were the most common symptom 31.8%. Risperidone-induced hyperprolactinemia and weight gain were seen in 87.2% and 53.6% in subgroup patients. Adverse effects such as sedation, gastrointestinal effects, and amenorrhea were seen in 9.7% (28/289), 5.1% (15/289), and 6.1% (7/114), respectively. Occurrence of DRD2 - 141 Ins/Del and Del/Del polymorphisms were significantly associated with increased prolactin levels in response to risperidone (odds ratio [OR] = 10.45; 95% confidence interval = 1.29-84.89, P = 0.004). No such association was observed with 5HTR2C (-759 C>T) polymorphism. Weight gain and EPS were not associated with the above genetic polymorphisms.

CONCLUSION

Hyperprolactinemia, weight gain, and EPSs (>36.7%) were common adverse effects of risperidone. DRD2 - 141C Ins/Del and Del/Del polymorphisms were significantly associated with increased prolactin levels (OR = 10.45) in response to risperidone.

Pharmacogenetics of Risperidone: A Systematic Review of the Clinical Effects of CYP2D6 Polymorphisms

OBJECTIVE

To summarize and evaluate the pharmacogenetic literature pertaining to the effects of CYP2D6 polymorphism on clinical outcomes of risperidone therapy.

DATA SOURCES

A systematic literature search was performed using the search terms risperidone, pharmacogenetics, cytochrome P-450 enzyme system, cytochrome P-450 CYP2D6, and polymorphism (genetic) in MEDLINE (1946-October 2012), EMBASE (1980-October 2012), PubMed (1947-October 2012), International Pharmaceutical Abstracts (1970-October 2012), and Google Scholar.

STUDY SELECTION AND DATA EXTRACTION

Identified articles were included if they measured the association between CYP2D6 genetic polymorphisms and clinical outcomes in at least 2 patients taking risperidone. The data elements extracted from these articles consisted of study design, number of subjects, indication for risperidone therapy, CYP2D6 phenotype status, mean daily dose of risperidone, and effects on clinical outcomes.

DATA SYNTHESIS

The identified citations consisted of 10 prospective nonrandomized, uncontrolled cohort studies, 1 retrospective cohort study, 1 prospective case-control study, and 1 retrospective case series. Studies were of variable quality and none provided high-quality evidence; they included heterogeneous patient populations with varying clinical diagnoses and drug therapy regimens. Most studies reported nonsignificant trends but were limited by power to detect statistical significance and short trial duration. However, increased risk of adverse effects (including QT interval prolongation) was observed in patients with inactive alleles.

CONCLUSIONS

While there were trends toward increased adverse effects in poor metabolizers, most outcomes were not significant. As such, routine genotyping should not be used for screening. Future usefulness cannot be ruled out, as many studies had significant limitations that preclude determination of clinical relevance. Adequately powered clinical and epidemiologic studies are warranted to clarify the role of CYP2D6 genotyping in practice.

CYP2D6 polymorphisms and their influence on risperidone treatment

Cytochrome P450 enzyme especially CYP2D6 plays a major role in biotransformation. The interindividual variations of treatment response and toxicity are influenced by the polymorphisms of this enzyme. This review emphasizes the effect of CYP2D6 polymorphisms in risperidone treatment in terms of basic knowledge, pharmacogenetics, effectiveness, adverse events, and clinical practice. Although the previous studies showed different results, the effective responses in risperidone treatment depend on the CYP2D6 polymorphisms. Several studies suggested that CYP2D6 polymorphisms were associated with plasma concentration of risperidone, 9-hydroxyrisperidone, and active moiety but did not impact on clinical outcomes. In addition, CYP2D6 poor metabolizer showed more serious adverse events such as weight gain and prolactin than other predicted phenotype groups. The knowledge of pharmacogenomics of CYP2D6 in risperidone treatment is increasing, and it can be used for the development of personalized medication in term of genetic-based dose recommendation. Moreover, the effects of many factors in risperidone treatment are still being investigated. Both the CYP2D6 genotyping and therapeutic drug monitoring are the important steps to complement the genetic-based risperidone treatment.

Prescription trends in children with pervasive developmental disorders: a claims data-based study in Japan

BACKGROUND

The only drug approved for pervasive developmental disorders (PDD) in Japan is pimozide. Several psychotropic drugs are also prescribed for offlabel use in Japan, but details regarding their prescription and use are largely unknown. The purpose of this study was to clarify the use of drug treatment in Japanese children with PDD.

METHODS

Data were extracted from claims data from the Japan Medical Data Center for children younger than 18 years of age who were newly diagnosed with PDD (International Classification of Diseases version 10 codes: F84) from 2005 to 2010 (total of 3276 patients as of 2010). The prescription rates were presented as the percentage of PDD patients who were prescribed each drug.

RESULTS

Prior to 2010, the prescription rates for atypical antipsychotics, other antipsychotics, psychostimulants, all other central nervous system drugs, anticovnvulsants, non-barbiturates, and Parkinson's disease/syndrome drugs significantly increased among the Anatomical Therapeutic Chemical classifications defined as the "nervous system" (trend P≤0.02). The prescription rate for risperidone consistently increased, reaching 6.9% in 2010 (trend P<0.0001), the highest rate of the surveyed drugs among the antipsychotics. The prescription rate for aripiprazole also increased (trend P<0.0001), reaching 1.9% in 2010. The prescription rate for pimozide showed no annual changes, with a low rate of 0.4% in 2010.

CONCLUSION

Compared with pimozide, the prescription rates for risperidone, aripiprazole and other psychotropic drugs have increased. Because safety data for these drugs in Japanese children are sparse, there is a need for future safety evaluations of these drugs in Japanese children.

Variants in the DRD2 locus and antipsychotic-related prolactin levels: A meta-analysis

BACKGROUND

Although dopamine D2 receptor antagonists lead to dose-dependent prolactin (PRL) elevations proportionate to their D2 affinity, considerable inter-individual differences exist. We conducted a meta-analytic review of associations between genetic variations in the dopamine D2 receptor gene (DRD2) and PRL levels in antipsychotic-treated subjects.

METHODS

Systematic literature search (5/8/2015) was performed to find published studies of pharmacogenetic associations between two DRD2 variants, Taq1A (rs1800497) and -141C Ins/Del (rs1799732), and PRL levels during antipsychotic treatment (excluding aripiprazole). Patients were included independent of age or diagnosis. Random effects models were used and Hedges' g was calculated as the effect size measure. Subgroup analyses explored the effect of sex and diagnosis, (males vs females; schizophrenia vs non-schizophrenia).

RESULTS

Altogether, 11 studies (n=1034, schizophrenia-spectrum=475) for Taq1A polymorphism, and 4 studies (n=451, schizophrenia-spectrum=274) for -141C Ins/Del polymorphism, each reporting on PRL levels but not on the proportion of patients with hyperprolactinemia, were meta-analyzed. Across all patients, there was no statistically significant association between PRL levels and either DRD2 Taq1A genotype or DRD2 -141C Ins/Del genotype. However, in patients with schizophrenia, PRL levels were significantly higher in DRD2 Taq1A A1 carriers than A1 non-carriers (studies=5, n=475, Hedges' g=0.250, 95% CI=0.068-0.433, p=0.007, I(2)=0%).

DISCUSSION

Although there was no significant association between either DRD2 Taq1A genotype or DRD2 -141C Ins/Del genotype and PRL levels in all included patients, our results suggest that DRD2 Taq1A genotype may affect antipsychotic-related PRL levels in patients with schizophrenia. Because of the small sample size, further studies are needed to confirm these results.

Genetics of Common Antipsychotic-Induced Adverse Effects

The effectiveness of antipsychotic drugs is limited due to accompanying adverse effects which can pose considerable health risks and lead to patient noncompliance. Pharmacogenetics (PGx) offers a means to identify genetic biomarkers that can predict individual susceptibility to antipsychotic-induced adverse effects (AAEs), thereby improving clinical outcomes. We reviewed the literature on the PGx of common AAEs from 2010 to 2015, placing emphasis on findings that have been independently replicated and which have additionally been listed to be of interest by PGx expert panels. Gene-drug associations meeting these criteria primarily pertain to metabolic dysregulation, extrapyramidal symptoms (EPS), and tardive dyskinesia (TD). Regarding metabolic dysregulation, results have reaffirmed HTR2C as a strong candidate with potential clinical utility, while MC4R and OGFR1 gene loci have emerged as new and promising biomarkers for the prediction of weight gain. As for EPS and TD, additional evidence has accumulated in support of an association with CYP2D6 metabolizer status. Furthermore, HSPG2 and DPP6 have been identified as candidate genes with the potential to predict differential susceptibility to TD. Overall, considerable progress has been made within the field of psychiatric PGx, with inroads toward the development of clinical tools that can mitigate AAEs. Going forward, studies placing a greater emphasis on multilocus effects will need to be conducted.

A Prospective Pharmacogenomic Study of Crohn's Disease Patients during Routine Therapy with Anti-TNF-α Drug Adalimumab: Contribution of ATG5, NFKB1, and CRP Genes to Pharmacodynamic Variability

Crohn's disease is often treated with the anti-tumor necrosis factor-α drug adalimumab. However, about 20%-40% of patients do not display adequate therapeutic response. We prospectively evaluated, during a routine therapy of Crohn's disease patients, the candidate autophagy-related genes ATG12 and ATG5 and the inflammation-related genes NFKB1, NFKBIA, and CRP as potential predictors of adalimumab treatment response (pharmacodynamics). The associations of haplotypes and SNPs in these genes with response to drug therapy, biochemical parameters, and body mass were determined at baseline and after 4, 12, 20, and 30 weeks of therapy. Association analysis showed that haplotypes defined with the SNPs rs9373839 and rs510432 in ATG5 gene were significantly associated with positive response to therapy (p < 0.002). In addition, allele C and genotypes CC and CT of the rs1130864 in the CRP gene were positively associated with therapeutic response (p < 0.002). To the best of our knowledge, this is the first report that supports the association of SNPs in ATG5 and CRP genes with response to adalimumab therapy in Crohn's disease. Further study of these biological pathways in larger and independent clinical samples is warranted as novel streams of research on precision medicine and diagnostics for Crohn's disease.

Impact of Pharmacogenetic Markers of CYP2D6 and DRD2 on Prolactin Response in Risperidone-Treated Thai Children and Adolescents With Autism Spectrum Disorders

OBJECTIVE

The aim of the study was to identify the impact of pharmacogenetic markers associated with prolactin concentration in risperidone-treated children and adolescents with autism spectrum disorders.

METHODS

One hundred forty-seven children and adolescents with autism, aged 3 to 19 years, received risperidone. The clinical data of patients were recorded from medical records. Prolactin levels were measured by chemiluminescence immunoassay. Three CYP2D6 single nucleotide polymorphisms, CYP2D6*4 (1846G>A), *10 (100C>T), and *41 (2988G>A), 1 gene deletion (*5), and DRD2 Taq1A (rs1800497) polymorphism were genotyped by TaqMan real-time polymerase chain reaction.

RESULTS

The 3 common allelic frequencies were CYP2D6*10 (55.10%), *1 (32.65%), and *5 (6.12%), respectively. Patients were grouped according to their CYP2D6 genotypes. There was no significant correlation between the concentrations of prolactin among the CYP2D6 genotypes. In addition, there were no statistical differences in the prolactin response among the CYP2D6-predicted phenotypes of extensive metabolizer and intermediate metabolizer. The DRD2 genotype frequencies were Taq1A A2A2 (38.77%), A1A2 (41.50%), and A1A1 (19.73%), respectively. There were statistically significant differences in prolactin level of patients among the 3 groups (P = 0.033). The median prolactin level in patients with DRD2 Taq1A A2A2 (17.80 ng/mL) was significantly higher than A1A2 (17.10 ng/mL) and A1A1 (12.70 ng/mL).

CONCLUSIONS

DRD2 Taq1A A2A2 polymorphisms may play a significant role in the hyperprolactinemia- associated with risperidone treatment in children and adolescent with autism spectrum disorder. Many drugs used chronically in psychiatric diseases exert their effects mainly through the dopamine D2 receptor. It is therefore possible that these drugs could alter the expression of any dopamine receptor, thus affecting the pharmacodynamics characteristics and toxicity of drug substrates during pharmacotherapy.

Pharmacogenetics of Risperidone and Cardiovascular Risk in Children and Adolescents

Objective. To identify the frequency of obesity and metabolic complications in child and adolescent users of risperidone. Potential associations with clinical parameters and SNPs of the HTR2C, DRD2, LEP, LEPR, MC4R, and CYP2D6 genes were analyzed. Methods. Samples from 120 risperidone users (8-20 years old) were collected and SNPs were analyzed, alongside assessment of chronological and bone ages, prescribed and weight-adjusted doses, use of other psychotropic drugs, waist circumference, BMI z-scores, blood pressure, HOMA-IR index, fasting levels of serum glucose, insulin, cholesterol, triglycerides, transaminases, and leptin. Results. Thirty-two (26.7%) patients were overweight and 5 (4.2%) obese. Hypertension was recorded in 8 patients (6.7%), metabolic syndrome in 6 (5%), and increased waist circumference in 20 (16.7%). The HOMA-IR was high for 22 patients (18.3%), while total cholesterol and triglycerides were high in 20 (16.7%) and 41 (34.2%) patients, respectively. SNP associations were found for LEP, HTR2C, and CYP2D6 with BMI; CYP2D6 with blood pressure, ALT, and HOMA-IR; HTR2C and LEPR with leptin levels; MC4R and DRD2 with HOMA-IR; HTR2C with WC; and LEP with ALT. Conclusions. Although not higher than in the general pediatric population, a high frequency of patients was overweight/obese, with abnormalities in metabolic parameters and some pharmacogenetic associations.

Hyperprolactinemia in Children and Adolescents with Use of Risperidone: Clinical and Molecular Genetics Aspects

OBJECTIVE

In children and adolescents treated with risperidone, hyperprolactinemia is a frequent complication that may have clinical repercussions. Several genes have been associated with this occurrence. The aim of this study was to evaluate the frequency of hyperprolactinemia in children and adolescents treated with risperidone, and its associations with clinical and pharmacological data and certain polymorphisms of the following genes: Dopamine receptor D2 (DRD2), 5-hydroxytryptamine (serotonin) receptor 2C (HTR2C), cytochrome P450, family 2, subfamily D, polypeptide 6 (CYP2D6), leptin (LEP), leptin receptor (LEPR), melanocortin 4 receptor (MC4R), and scavenger receptor class B, member 2 (SCARB2).

METHODS

The study included patients using risperidone (8-20 years old) and healthy subjects not exposed to the medication. Psychopathological symptoms, doses, and duration of treatment with risperidone, sex, skin color, body mass index (BMI), use of other psychotropic drugs, and polymorphisms of DRD2, HTR2C, CYP2D6, LEP, LEPR, MC4R, and SCARB2 genes were evaluated.

RESULTS

There were 120 patients and 197 individuals not exposed to risperidone who were evaluated. Among patients, hyperprolactinemia was found in 79 (65.8%) cases, with no differences regarding sex, skin color, or being in monotherapy with risperidone (26.7% of total patients) or not. The level of prolactin was not correlated, either in case or control groups, with chronological age, bone age, prescribed dose of risperidone, weight-adjusted dose of risperidone, or BMI (p > 0.05), but was negatively correlated with the treatment duration (r = -0.352, p = 0.001 among cases; and r = -0.324, p = 0.039 among controls). There were significant differences in use of risperidone between patients and healthy subjects without the medication in the frequency of the polymorphisms of the DRD2, HTR2C, and LEP genes. Considering both sexes together and also specifically among females, the occurrence of hyperprolactinemia was higher in the presence of the C allele of the rs6318 single nucleotide polymorphisms (SNP) of the HTR2C gene.

CONCLUSIONS

This group of children and adolescents with or without isolated use of risperidone presented with a high frequency of hyperprolactinemia, although asymptomatic, and associated, when considering only females or both sexes together, with being a carrier of the C allele of the rs6318 SNP of the HTR2C gene.

Pharmacogenomics of neuropsychiatric disorders: analysis of genetic variability in 162 identified neuroreceptors using 1000 Genomes Project data

BACKGROUND

Neuroreceptors are considered to be primary drug targets and their abrupt signaling is a notable cause of interindividual drug response variability and treatment failure for complex neuropsychiatric diseases. In view of recent evidence, it is believed that common genetic risk factors mainly highly polymorphic neuroreceptors are being shared among neuropsychiatric disorders.

MATERIALS & METHODS

We identified 162 neuroreceptors from the 639 known receptors in Homo sapiens and investigated 231,683 SNPs using 1000 Genomes Project data and evaluated their biological effect using in silico tools including RegulomeDB, SIFT, PolyPhen-2 and CAROL. Furthermore, data from the 1000 Genomes Project was utilized to retrieve minor allele frequency and calculate pairwise logartithm of the odds score among these SNPs for African, American, Asian and European populations separately as well as when combined together using Haploview v4.2. LRTag was used to identify tagSNPs in populations.

RESULTS

A total of 52,381 (22.60%) SNPs were predicted as functionally important genetic variations. We identified sets of 603, 495, 450, 453 and 646 informative tagSNPs for African, American, Asian, European and combined populations, respectively. We propose construction of a 'neuroreceptor variants array' with these informative SNPs for future pharmacogenomic studies of neuropsychiatric disorders.

CONCLUSION

Such an approach might improve genotype-phenotype correlation across different populations and lead to identification of reliable genetic markers and novel drug targets. Integration of these SNPs in literature would further provide evidence relevant to underlying mechanisms of genetics based nosology, pathophysiology and development of new drugs for the treatment of neuropsychiatric disorders.

Metabolic side effects and pharmacogenetics of second-generation antipsychotics in children

Second-generation antipsychotics (SGAs) are increasingly being used to treat children for a range of mental health conditions, for example, anxiety disorder, attention deficit hyperactivity disorder and bipolar disorder. SGA treatment is associated with weight gain and cardiometabolic side effects such as dyslipidemia, insulin resistance and elevated blood pressure, in some, but not all children. This review provides an overview of the potential role of pharmacogenomics in predisposing a child to unhealthy weight gain and cardiometabolic side effects with SGA treatment. Specifically, the review includes a synopsis of the evidence for cardiometabolic side effects in SGA-treated children, illustrating the extent and depth of the problem; summarizes the potential long-term consequences of developing cardiometabolic risk during childhood and highlights genetic variants that may be useful in predicting cardiometabolic side effects in SGA-treated children.

Pharmacogenomic medicine in autism: challenges and opportunities

Autism spectrum disorder (ASD) affects 1 in 68 children in the US and is distinguished by core deficits in social interactions. Developing pharmacologic treatments for ASD is complicated by clinical and genetic heterogeneity. Although pharmacological treatments have not been shown to be effective in treating the core symptoms of ASD (i.e., social deficits), there is evidence that the burden of emotional and behavioral problems can be reduced with pharmacotherapy. Numerous randomized clinical trials of treatments for the core ASD deficits have been conducted; however, most have provided inconclusive results due to the substantial variation in treatment response. Variation also exists in the considerable metabolic side effects of many of the current treatments. Some of this variation may be explained by differences in the underlying genetic pathways. Exploiting the link between genetic heterogeneity and clinical variation associated with behavioral problems may provide an opportunity for targeted treatment of ASD. In this review, we summarize the recent findings from pharmacogenomics studies of ASD and suggest further how understanding how genetic liability modifies the effect of drugs may present an opportunity to address the challenges of personalized medicine in autism.

Clinical and pharmacokinetic evaluation of risperidone for the management of autism spectrum disorder

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is often accompanied by psychiatric comorbidity. Although there is no medication currently available to treat the core symptoms of ASD, risperidone was the first drug to be approved for use in ASD and is still the best established psychopharmacological option for the treatment of irritability and behavioral problems in ASD.

AREAS COVERED

This article gives an overview of the pharmacokinetic profile of risperidone and a comprehensive review of treatment studies regarding the use of risperidone in ASD.

EXPERT OPINION

Ample evidence supports the short-term use of risperidone for treating irritability and behavioral problems in ASD. Risperidone also shows promise in treating symptoms often associated with ASD, such as stereotypical behavior, social difficulties, hyperactivity and cognitive problems. However, several adverse effects have been identified; most are mild or moderate and well manageable, but weight gain and metabolic changes are a considerable concern. Therefore, risperidone should in our view be seen as 'a last resort', only justified for the short-term treatment of serious behavioral problems, which have failed to respond sufficiently to behavioral interventions. Future studies should investigate long-term effects of risperidone and factors that facilitate individual risk-benefit analyses before treatment.