Dopamine ( DRD 2 ) and Serotonin ( HTR 2A, 2C) Receptor Gene Polymorphisms do not influence early response to Risperidone in South Indian Patients with Schizophrenia

Association between the rs6313 polymorphism in the 5-HTR2A gene and the efficacy of antipsychotic drugs

BACKGROUND

Prescribing the optimal antipsychotic treatment to schizophrenia is very important as it is well established that patients have different sensitivity to the available antipsychotic drugs. The genotype of the HTR2A T102C (rs6313) polymorphism has been suggested to affect the efficacy of antipsychotic drugs, but the results of different studies have been inconsistent METHODS: In this study, a meta-analysis was used to ascertain the association between allele and genotype polymorphism of rs6313 and the efficacy of antipsychotic drugs. Related studies publicated from January 1995 to December 2021 were retrieved from PubMed, Embase, ScienceDirect, and Web of Science databases. The correlations between allele and genotype polymorphism of rs6313 and the responder rate and scale score reduction rate of antipsychotics were analyzed. In addition, subgroup analyses were performed on time, drug, and ethnicity.

RESULTS

A total of 18 studies were included. The meta-analysis showed that allele and genotype polymorphisms at the rs6313 locus overall were not associated with antipsychotic drug responder rate or scale score reduction rate. Ethnicity subgroup analysis showed that antipsychotic drugs were more effective in patients with allele T in the Caucasian population. Indian patients with the TT genotype had the lowest scale score reduction rate and poor drug treatment effect. East Asian patients with the TC genotype had better treatment effect, whereas in patients with the CC genotype, the treatment was less effective. Drug subgroup analysis showed that patients with the TC genotype treated with clozapine had the highest responder rate and score reduction rate.

CONCLUSIONS

The association between rs6313 polymorphism and the efficacy of antipsychotic drugs is mainly influenced by drug and ethnicity. Caucasian patients with the T allele respond better to drug therapy, and Asian patients with TC genotype. The TC genotype was also a good predictor of the efficacy of clozapine treatment.

Functional single nucleotide polymorphisms in dopaminergic receptors D2 predict clinical response to Cariprazine

Cariprazine (CAR) is an antipsychotic drug for the treatment of schizophrenia (SCZ) and bipolar disorder (BD), and it acts as a partial agonist on the dopamine receptors (DR), D2, and D3. Although many single nucleotide polymorphisms (SNPs) in genes coding for these receptors are known to influence response to antipsychotics, to date, no study on CAR pharmacogenetics exists. In this pilot study, we investigated the relationship between SNPs in DRD2 (rs1800497 and rs6277) and DRD3 (rs6280), and response to CAR treatment, evaluated by the psychometric Brief Psychiatric Rating Scale (BPRS), in a cohort of Caucasian patients. We found a significant association between DRD2 rs1800497 and rs6277 and response to CAR treatment. When genotypes were combined into an arbitrary score, the receiver operating characteristic curve analysis showed that using a cut-off value of -2.5 the response to CAR treatment could be predicted with a positive likelihood ratio of 8.0. Our study report, for the first time, a correlation between SNPs in DRD2 and response to CAR treatment. After confirmation in a larger cohort of patients, our results could open the way for the identification of new tools for the provision of response to CAR treatment.

Pharmacogenetics and Schizophrenia-Can Genomics Improve the Treatment with Second-Generation Antipsychotics?

Schizophrenia (SCZ) is a complex psychiatric disorder of multifactorial origin, in which both genetic and environmental factors have an impact on its onset, course, and outcome. Large variability in response and tolerability of medication among individuals makes it difficult to predict the efficacy of a chosen therapeutic method and create universal and precise guidelines for treatment. Pharmacogenetic research allows for the identification of genetic polymorphisms associated with response to a chosen antipsychotic, thus allowing for a more effective and personal approach to treatment. This review focuses on three frequently prescribed second-generation antipsychotics (SGAs), risperidone, olanzapine, and aripiprazole, and aims to analyze the current state and future perspectives in research dedicated to identifying genetic factors associated with antipsychotic response. Multiple alleles of genes involved in pharmacokinetics (particularly isoenzymes of cytochrome P450), as well as variants of genes involved in dopamine, serotonin, and glutamate neurotransmission, have already been identified as ones of significant impact on antipsychotic response. It must, however, be noted that although currently obtained results are promising, trials with bigger study groups and unified protocols are crucial for standardizing methods and determining objective antipsychotic response status.

Association of 5-HTR2A T102C and A-1438G polymorphisms with clinical response to atypical antipsychotic treatment in schizophrenia: A meta-analysis

Associations of serotonin 2A receptor (5-HTR2A) gene polymorphisms with clinical response to atypical antipsychotics (AAPs) treatment in schizophrenia (SCZ) were inconsistent. Thus we conducted a meta-analysis to investigate more reliable estimates. The Cochrane Library, Embase, PubMed, Weipu, CNKI and Wanfang databases were searched for eligible studies published up to September 2021. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated in four genetic models. Subgroup analyses were performed by ethnicity and antipsychotic type. Meta-regression was used to evaluate the potential effects of confounding variables. In total, 19 studies were included for the meta-analysis, of which 17 studies containing 2359 patients were identified for T102C polymorphism and 7 studies containing 1408 patients for A-1438G polymorphism. The results showed that A-1438G polymorphism was significantly associated with clinical response to AAPs treatment in SCZ in four genetic models (allele model, A vs. G, OR = 1.87, 95% CI = 1.05-3.33, P = 0.034; recessive model, AA vs. GA + GG: OR = 1.79, 95% CI = 1.17-2.72, P = 0.007; dominant model, AA + GA vs. GG: OR = 3.40, 95% CI = 1.15-10.10, P = 0.027; co-dominant model, AA vs. GG: OR = 3.44, 95% CI = 1.07-11.10, P = 0.039) in Asians, but not in Caucasians. When stratified by antipsychotic type, A-1438G polymorphism was related to the efficacy of olanzapine in recessive model (AA vs. GA + GG, OR = 1.85, 95% CI = 1.18-2.90, P = 0.007), but not in other models. However, neither four genetic models nor subgroup analyses of T102C polymorphism were found any significant associations with AAPs response (P > 0.05). Meta-regression revealed that no association was confounded by mean age, male ratio, treatment duration and illness duration (P > 0.05). The present meta-analysis indicated that 5-HTR2A A-1438G polymorphism, but not T102C polymorphism, was significantly associated with AAPs response in SCZ, especially in Asians and olanzapine-treated patients.

Genetic Polymorphisms Associated With the Pharmacokinetics, Pharmacodynamics and Adverse Effects of Olanzapine, Aripiprazole and Risperidone

Olanzapine, aripiprazole and risperidone are atypical antipsychotics or neuroleptics widely used for schizophrenia treatment. They induce various adverse drug reactions depending on their mechanisms of action: metabolic effects, such as weight gain and alterations of glucose and lipid metabolism; hyperprolactinemia and extrapyramidal effects, such as tremor, akathisia, dystonia, anxiety and distress. In this review, we listed polymorphisms associated with individual response variability to olanzapine, aripiprazole and risperidone. Olanzapine is mainly metabolized by cytochrome P450 enzymes, CYP1A2 and CYP2D6, whereas aripiprazole and risperidone metabolism is mainly mediated by CYP2D6 and CYP3A4. Polymorphisms in these genes and other enzymes and transporters, such as enzymes from the uridine 5'-diphospho-glucuronosyltransferase (UGT) family and ATP-binding cassette sub-family B member 1 (ABCB1), are associated to differences in pharmacokinetics. The three antipsychotics act on dopamine and serotonin receptors, among others, and several studies found associations between polymorphisms in these genes and variations in the incidence of adverse effects and in the response to the drug. Since olanzapine is metabolized by CYP1A2, a lower starting dose should be considered in patients treated with fluvoxamine or other CYP1A2 inhibitors. Regarding aripiprazole, a reduced dose should be administered in CYP2D6 poor metabolizers (PMs). Additionally, a reduction to a quarter of the normal dose is recommended if the patient is treated with concomitant CYP3A4 inhibitors. Risperidone dosage should be reduced for CYP2D6 PMs and titrated for CYPD6 ultrarapid metabolizers (UMs). Moreover, risperidone dose should be evaluated when a CYP2D6, CYP3A4 or ABCB1 inhibitor is administered concomitantly.

Toward personalized medicine in schizophrenia: Genetics and epigenetics of antipsychotic treatment

Schizophrenia is a complex psychiatric disorder where genetic, epigenetic, and environmental factors play a role in disease onset, course of illness, and treatment outcome. Pharmaco(epi)genetic research presents an important opportunity to improve patient care through prediction of medication side effects and response. In this narrative review, we discuss the current state of research and important progress of both genetic and epigenetic factors involved in antipsychotic response, over the past five years. The review is largely focused on the following frequently prescribed antipsychotics: olanzapine, risperidone, aripiprazole, and clozapine. Several consistent pharmacogenetic findings have emerged, in particular pharmacokinetic genes (primarily cytochrome P450 enzymes) and pharmacodynamic genes involving dopamine, serotonin, and glutamate neurotransmission. In addition to studies analysing DNA sequence variants, there are also several pharmacoepigenetic studies of antipsychotic response that have focused on the measurement of DNA methylation. Although pharmacoepigenetics is still in its infancy, consideration of both genetic and epigenetic factors contributing to antipsychotic response and side effects no doubt will be increasingly important in personalized medicine. We provide recommendations for next steps in research and clinical evaluation.

Gene-Based Association Analysis Suggests Association of HTR2A With Antidepressant Treatment Response in Depressed Patients

The serotonin [5-hydroxytryptamine (5-HT)] system has been implicated in the pathogenesis of major depressive disorder (MDD). Among the 5-HT receptor subtypes, 5-HT2 is one of the major pharmacological therapeutic targets for MDD. There have been inconsistent findings in previous pharmacogenetic studies investigating the antidepressant therapeutic response using one or several 5-HT2A (HTR2A) genetic polymorphisms. By using gene-based association analysis, we hope to identify genetic variants of HTR2A which are related to MDD susceptibility and its antidepressant therapeutic response. 288 HTR2A single nucleotide polymorphisms in MDD susceptibility have been investigated through a case–control (455 MDD patients and 2, 998 healthy controls) study, as well as in antidepressant efficacy (n = 455) in our current research. The 21-item Hamilton Rating Scale for Depression was used to evaluate measures of antidepressant therapeutic efficacy. From two MDD groups in the antidepressant therapeutic response, by using gene-based analyses, we have identified 14 polymorphisms as suggestive markers for therapeutic response (13 for remission and 1 for response) in both meta- and mega-analyses. All of these HTR2A reported polymorphisms did not reach statistical significance in the case–control association study. This current investigation supported the link between HTR2A variants and antidepressant therapeutic response in MDD but not with MDD susceptibility.

Association of the genetic polymorphisms of metabolizing enzymes, transporters, target receptors and their interactions with treatment response to olanzapine in chinese han schizophrenia patients

Olanzapine is an atypical antipsychotic drug that has been increasingly used for treatment in schizophrenia. It has been observed that olanzapine responses in schizophrenia patients vary individually, but the reason has not been elucidated. In the study, we aimed to comprehensively explore the relationships between olanzapine responses and genetic polymorphisms of drug metabolizing enzymes, transporters and target receptors, and so as to interpret the reason of good and poor responses of olanzapine. A total of 241 Chinese Han paranoid schizophrenia who treated with olanzapine alone for 4 weeks were recruited. The positive and negative symptom scale (PANSS) was used to evaluate the efficacy of olanzapine. The genetic polymorphisms were detected by improved multiple ligase detection reaction (iMLDR). Multivariate logistic regression analysis suggested that the genetic polymorphisms of CYP1A2 rs762551, UGT1A4 rs2011425, ABCB1 rs1045642, DRD2 rs1799732 and rs1799978, 5-HTR2A rs6311 were significantly associated with olanzapine response. Multifactor dimensionality reduction (MDR) analysis showed that there was a negative interaction between CYP1A2 rs762551, ABCB1 rs1045642, DRD2 rs1799978, 5-HTR2A rs6311 and the interaction model was the optimal model. Our findings could partially explain the different olanzapine outcome and provided evidence for clarifying the predictive indicators of olanzapine response in further.

Pharmacogenetics of antipsychotics in adolescents with acute psychotic episode during first 14 days after admission: effectiveness and safety evaluation

Objectives Prediction of the antipsychotic's effectiveness is a relevant topic in the field of personalized medicine. Methods The research design of this study is a prospective observation with posthoc analysis of associations of genetic polymorphisms with safety parameters and effectiveness of antipsychotic therapy. We observed 53 adolescents with an acute psychotic episode which were prescribed antipsychotics for 14 days. We evaluated the effectiveness of antipsychotics with the Positive and Negative Symptoms Scale and the safety with the UKU Side Effects Rating Scale, Simpson-Angus Scale, and Barnes Akathisia rating scale. We genotyped CYP3A4*22 (rs2740574), CYP3A5*3 (6986A>G, rs7767746), CYP2D6*4, *9, *10 (rs3892097, rs1065852), ABCB1 1236C>T (rs1128503), 2677G>T/A (rs2032582), 3435C>T (rs1045642), DRD2 (rs1800497), DRD4 (rs1800955), HTR2A (rs6313) by the real-time polymerase chain reaction method. Results We found significantly more frequent "increased dream activity" between CYP2D6 intermediate metabolizers and normal metabolizers (54 vs. 22%; p=0.043). The «increased duration of sleep» was more often observed in homozygotes TT of ABCB1 2677G>T/A (50 vs. 15.8%, p=0.006) and TT of 3435C>T (41.7 vs. 8.2%, p=0.007). Conclusions We found that CYP2D6 and ABCB1 polymorphisms were associated with the safety of antipsychotics in adolescents with an acute psychotic episode.

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.