ABCB1 (MDR1) gene polymorphisms are associated with the clinical response to paroxetine in patients with major depressive disorder

Omics approaches open new horizons in major depressive disorder: from biomarkers to precision medicine

Major depressive disorder (MDD) is a recurrent episodic mood disorder that represents the third leading cause of disability worldwide. In MDD, several factors can simultaneously contribute to its development, which complicates its diagnosis. According to practical guidelines, antidepressants are the first-line treatment for moderate to severe major depressive episodes. Traditional treatment strategies often follow a one-size-fits-all approach, resulting in suboptimal outcomes for many patients who fail to experience a response or recovery and develop the so-called "therapy-resistant depression". The high biological and clinical inter-variability within patients and the lack of robust biomarkers hinder the finding of specific therapeutic targets, contributing to the high treatment failure rates. In this frame, precision medicine, a paradigm that tailors medical interventions to individual characteristics, would help allocate the most adequate and effective treatment for each patient while minimizing its side effects. In particular, multi-omic studies may unveil the intricate interplays between genetic predispositions and exposure to environmental factors through the study of epigenomics, transcriptomics, proteomics, metabolomics, gut microbiomics, and immunomics. The integration of the flow of multi-omic information into molecular pathways may produce better outcomes than the current psychopharmacological approach, which targets singular molecular factors mainly related to the monoamine systems, disregarding the complex network of our organism. The concept of system biomedicine involves the integration and analysis of enormous datasets generated with different technologies, creating a "patient fingerprint", which defines the underlying biological mechanisms of every patient. This review, centered on precision medicine, explores the integration of multi-omic approaches as clinical tools for prediction in MDD at a single-patient level. It investigates how combining the existing technologies used for diagnostic, stratification, prognostic, and treatment-response biomarkers discovery with artificial intelligence can improve the assessment and treatment of MDD.

ABCB1 C1236T, G2677TA and C3435T Genetic Polymorphisms and Antidepressant Response Phenotypes: Results from a Portuguese Major Depressive Disorder Cohort

P-glycoprotein (P-GP) is a transporter molecule expressed on the apical surface of capillary endothelial cells of the Blood-Brain Barrier (BBB), whose activity heavily influences drug distribution, including antidepressants. This transporter is encoded by ABCB1 gene, and genetic variations within ABCB1 gene have been proposed to affect drug efflux and have been previously associated with depression. In this context, we aimed to evaluate the role of C1236T, G2677TA and C3435T ABCB1 genetic polymorphisms in antidepressant treatment phenotypes from a cohort of patients harboring Major Depressive Disorder. Patients enrolled in the study consisted of 80 individuals with Major Depressive Disorder, who took part in a 27-month follow-up study at HML, Portugal. To investigate the correlation between ABCB1 polymorphisms and antidepressant response phenotypes, DNA was extracted from peripheral blood, and C1236T, C3435T and G2677TA polymorphisms were genotyped with TaqMan® SNP Genotyping Assays. Despite the fact that the evaluated polymorphisms (C1236T, C3435T and G2677TA) were not associated with treatment resistant depression, or relapse, we observed that patients carrying TT genotype of the C3435T polymorphism remit earlier than the ones carrying CC or CT genotypes (10.2 weeks vs. 14.9 and 21.3, respectively, p = 0.028, Log-rank test). Since we found an association with C3435T and time to remission, and not to the absence of remission, we suggest that this polymorphism could have an impact on antidepressant drug distribution, and thus influence on the time to remission will occur, without influencing the risk of remission itself.

Distribution of pharmacogene allele and phenotype frequencies in Brazilian psychiatric patients

Purpose: This work was designed to identify the pharmacogenetic profile of Brazilian psychiatric patients receiving psychoactive drug treatment according to ethnicity. Methods: Based on the GnTech® database, this cross-sectional study analyzed data from self-reported sociodemographic and genetic results from the next-generation sequencing panel composed of 26 pharmacogenes from 359 psychotropic drug users. Results: Variant frequencies of multiple pharmacogenes presented differences between ethnicities (CYP3A5, CYP2D6, CYP1A2, CYP2B6, CYP3A4, UGT1A4, UGT2B15, ABCB1 rs1045642, ADRA2A rs1800544, COMT rs4680, GRIK4 rs1954787, GSK3B rs334558, GSK3B rs6438552, HTR1A rs6295, HTR2A rs7997012, HTR2C rs1414334, MTHFR rs1801131, OPRM1 rs1799971 and 5-HTTLPR), endorsing the necessity of individual-level analyses in drug treatment. Conclusion: A discussion of pharmacogenomic test implementation in psychiatric clinical practice is needed to improve treatment choices, especially in Brazil, a multiethnic country.

Pharmacokinetic Markers of Clinical Outcomes in Severe Mental Illness: A Systematic Review

The term severe mental illness (SMI) encompasses those psychiatric disorders exerting the highest clinical burden and socio-economic impact on the affected individuals and their communities. Pharmacogenomic (PGx) approaches hold great promise in personalizing treatment selection and clinical outcomes, possibly reducing the burden of SMI. Here, we sought to review the literature in the field, focusing on PGx testing and particularly on pharmacokinetic markers. We performed a systematic review on PUBMED/Medline, Web of Science, and Scopus. The last search was performed on the 17 September 2022, and further augmented with a comprehensive pearl-growing strategy. In total, 1979 records were screened, and after duplicate removal, 587 unique records were screened by at least 2 independent reviewers. Ultimately, forty-two articles were included in the qualitative analysis, eleven randomized controlled trials and thirty-one nonrandomized studies. The observed lack of standardization in PGx tests, population selection, and tested outcomes limit the overall interpretation of the available evidence. A growing body of evidence suggests that PGx testing might be cost-effective in specific settings and may modestly improve clinical outcomes. More efforts need to be directed toward improving PGx standardization, knowledge for all stakeholders, and clinical practice guidelines for screening recommendations.

Influence of eight ABCB1 polymorphisms on antidepressant response in a prospective cohort of treatment-free Russian patients with moderate or severe depression: An explorative psychopharmacological study with naturalistic design

BACKGROUND

Many antidepressants are substrates of P-glycoprotein, an efflux transporter in the blood-brain-barrier encoded by the ABCB1 gene. Genetic variations might influence the transport rate of antidepressants and hence their pharmacological effects. This study investigates the influence of eight polymorphisms in the ABCB1 gene on antidepressant treatment response.

METHOD

152 patients were included from psychiatric departments of the Mental Health Research Institute in Tomsk. The difference in Hamilton-Depression-Rating-Scale (HAMD-17)-scores between baseline and week two, week two and four, and baseline and week four was used to estimate timing of improvement of depression. Associations between the ABCB1 gene-polymorphisms and reduction in HAMD-17 score were assessed using independent t-test and multiple linear regression.

RESULTS

Tricyclic antidepressants were associated with a higher reduction of HAMD-17 score when compared to SSRIs. The SNP rs2235040 A-allele had a significant positive influence on the ΔHAMD-17_(0→2W) score but a significant negative influence on the ΔHAMD-17_(2→4W) score. The rs4148739 G-allele had a significant negative influence on the ΔHAMD-17_(0→2W) score but a significant positive influence on the ΔHAMD-17_(2→4W) score. The SNP rs2235015 T-allele is significant negatively related to the ΔHAMD-17_(2→4W) score.

CONCLUSION

ABCB1 Genetic variations appear to affect speed but not magnitude of antidepressant drug response.

ABCB1 variants and sex affect serotonin transporter occupancy in the brain

Strategies to personalize psychopharmacological treatment promise to improve efficacy and tolerability. We measured serotonin transporter occupancy immediately after infusion of the widely prescribed P-glycoprotein substrate citalopram and assessed to what extent variants of the ABCB1 gene affect drug target engagement in the brain in vivo. A total of 79 participants (39 female) including 31 patients with major depression and 48 healthy volunteers underwent two PET/MRI scans with the tracer [¹¹C]DASB and placebo-controlled infusion of citalopram (8 mg) in a cross-over design. We tested the effect of six ABCB1 single nucleotide polymorphisms and found lower SERT occupancy in ABCB1 rs2235015 minor allele carriers (n = 26, MAF = 0.18) compared to major allele homozygotes (t₇₃ = 2.73, p_FWE < 0.05) as well as in men compared to women (t₇₃ = 3.33, p_FWE < 0.05). These effects were robust to correction for citalopram plasma concentration, age and diagnosis. From occupancy we derived the ratio of occupied to unoccupied SERT, because in theory this measure is equal to the product of drug affinity and concentration at target sites. A model combining genotype with basic clinical variables, predicted that, at the same dosage, occupied to unoccupied SERT ratio was -14.48 ± 5.38% lower in rs2235015 minor allele carriers, +19.10 ± 6.95% higher in women, -4.83 ± 2.70% lower per 10 kg bodyweight, and -2.68 ± 3.07% lower per 10 years of age. Our results support the exploration of clinical algorithms with adjustment of initial citalopram dosing and highlight the potential of imaging-genetics for precision pharmacotherapy in psychiatry.

Effects of ABCB1 gene polymorphism on the efficacy of antidepressant drugs: A protocol for systematic review and meta-analysis

BACKGROUND

Antidepressant drugs are mainly used to treat depression clinically. ABCB1 affects the P-glycoprotein activity and changes the amount of drugs in the blood tissue barrier that can be squeezed back into the blood, thus affecting the efficacy of antidepressants. In this present study, Meta-analysis was performed to further investigate the influences of ABCB1 gene polymorphism on antidepressant response.

METHODS

Relevant literatures were searched from the PubMed, EMBASE, Web of Science, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals Database, China Biology Medicine disc, and Wan Fang databases up to May 2021 without any language restrictions. STATA 16.0 software was applied for this meta-analysis. Odds ratio (OR) and its corresponding 95% confidence interval (CI) were calculated.

RESULTS

The results of this meta-analysis will be submitted to a peer-reviewed journal for publication.

CONCLUSION

This meta-analysis will summarize the effects of ABCB1 gene polymorphism on antidepressant response.

Surface Interactions during the Removal of Emerging Contaminants by Hydrochar-Based Adsorbents

The aim of this work was to test activated carbons derived from hydrochars produced from sunflower stem, olive stone and walnut shells, as adsorbents for emerging contaminants in aqueous solution, namely fluoxetine and nicotinic acid. The adsorption capacity was determined by the chemical nature of the adsorbents, namely the presence of specific functional groups and their positive or negative ionization in aqueous solutions and also by steric factors. The activated carbons produced by air showed a higher adsorption capacity of fluoxetine, whilst the samples produced by carbon dioxide activation were more useful to remove nicotinic acid. In general, surface acidity was advantageous for fluoxetine adsorption and detrimental for nicotinic acid removal. The adsorption mechanisms involved in each case were discussed and related to the adsorbents characteristics. The maximum adsorption capacity, Q₀, given by the Langmuir model was 44.1 and 91.9 mg g⁻¹ for fluoxetine and nicotinic acid adsorption, respectively.

Donepezil, a cholinesterase inhibitor used in Alzheimer's disease therapy, is actively exported out of the brain by abcb1ab p-glycoproteins in mice

Polymorphisms in the drug transporter gene ABCB1 predict the treatment response of selected antidepressants and limit anticonvulsive medication's effectiveness. The ABCB1 locus encodes the energy-dependent transporter P-glycoprotein (P-gp) of the blood brain barrier (BBB), which serves as an efflux pump of its substrates in the expressing tissues of vertebrates. One experimental setup to determine a posteriori the P-gp substrate status is the use of the double abcb1ab knock-out (KO) mice model. Since so far, P-gp substrate status of donepezil, a cholinesterase inhibitor wildly used in Alzheimer's disease therapy was inconclusive, we performed subcutanous (s.c.), continuous injections over 11 days in double abcb1ab KO and P-gp competent wildtype (WT) mice. Both in brain and in testis concentrations of donepezil were significantly higher in P-gp deficient mice compared to WT controls (2.39 and 2.24 times respectively). In conclusion, in mice donepezil's brain bioavailability depends on P-gp.

Association study of genetic polymorphisms in proteins involved in oseltamivir transport, metabolism, and interactions with adverse reactions in Mexican patients with acute respiratory diseases

Oseltamivir, a pro-drug, is the best option for treatment and chemoprophylaxis for influenza outbreaks. However, many patients treated with oseltamivir developed adverse reactions, including hypersensitivity, gastritis, and neurological symptoms. The aim of this study was to determine the adverse drug reactions (ADRs) in Mexican patients treated with oseltamivir and whether these ADRs are associated with SNPs of the genes involved in the metabolism, transport, and interactions of oseltamivir. This study recruited 310 Mexican patients with acute respiratory diseases and treated them with oseltamivir (75 mg/day for 5 days) because they were suspected to have influenza A/H1N1 virus infection. Clinical data were obtained from medical records and interviews. Genotyping was performed using real-time polymerase chain reaction and TaqMan probes. The association was assessed under genetic models with contingency tables and logistic regression analysis. Out of 310 patients, only 38 (12.25%) presented ADRs to oseltamivir: hypersensitivity (1.9%), gastritis (10%), and depression and anxiety (0.9%). The polymorphism ABCB1-rs1045642 was associated with adverse drug reactions under the recessive model (P = 0.017); allele C was associated with no adverse drug reactions, while allele T was associated with adverse drug reactions. The polymorphisms SLC15A1-rs2297322, ABCB1-rs2032582, and CES1-rs2307243 were not consistent with Hardy-Weinberg equilibrium, and no other associations were found for the remaining polymorphisms. In conclusion, the polymorphism rs1045642 in the transporter encoded by the ABCB1 gene is a potential predictive biomarker of ADRs in oseltamivir treatment.

ABCB1 Gene Is Associated With Clinical Response to SNRIs in a Local Chinese Han Population

Background: The relation between the ATP-binding cassette subfamily B member 1 (ABCB1) gene and major depressive disorder (MDD) has been studied in a local Chinese Han population. MDD is associated with the rs2032582 (G2677T) and rs1128503 (C1236T) single-nucleotide polymorphisms (SNPs) of ABCB1 but not with rs1045642, rs2032583, rs2235040, and rs2235015. This study aims to explore the potential correlations of therapeutic responses with selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) in a local Chinese Han population.

Methods: The study population included 292 patients with MDD. All patients were assessed at baseline and at first, second, fourth, and sixth weeks according to the 17-item Hamilton Rating Scale for Depression (HAM-D17) to determine their therapeutic responses to SSRIs and SNRIs.

Results: In the SSRI therapy group, the genotype or allele distribution of six SNPs was not significantly different between responders and nonresponders. In the SNRI therapy group, only rs2032583 was associated with a therapeutic response to SNRIs. The C allele of the ABCB1 rs2032583 polymorphism was negatively correlated with therapeutic responses according to logistic regression analysis.

Conclusion: The ABCB1 gene polymorphisms may not be associated with therapeutic responses to SSRIs but not with SNRIs. The TT genotype of rs2032583 could be a predictive factor of improved treatment responses to SNRIs in the Chinese population. These findings should be replicated in future studies with larger patient groups.

Effect of ABCB1 C3435T Polymorphism on Pharmacokinetics of Antipsychotics and Antidepressants

P-glycoprotein, encoded by ABCB1, is an ATP-dependent drug efflux pump which exports substances outside the cell. Some studies described connections between C3435T polymorphism T allele and lower P-glycoprotein expression; therefore, homozygous T/T could show higher plasma levels. Our aim was to evaluate the effect of C3435T on pharmacokinetics of 4 antipsychotics (olanzapine, quetiapine, risperidone and aripiprazole) and 4 antidepressants (trazodone, sertraline, agomelatine and citalopram). The study included 473 healthy volunteers receiving a single oral dose of one of these drugs, genotyped by real-time PCR. Multivariate analysis was performed to adjust the effect of sex and genotype of the main cytochrome P450 enzymes. C3435T polymorphism had an effect on olanzapine pharmacokinetics, as T/T individuals showed lower clearance and volume of distribution. T/T individuals showed lower T_1/2 of 9-OH-risperidone, but this difference disappeared after multivariate correction. T/T homozygous individuals showed lower dehydro-aripiprazole and trazodone area under the concentration-time curve, along with lower half-life and higher clearance of trazodone. C/T genotype was associated to higher citalopram maximum concentration. C3435T had no effect on quetiapine, sertraline or agomelatine pharmacokinetics. C3435T can affect the elimination of some drugs in different ways. Regarding risperidone, trazodone and dehydro-aripiprazole, we observed enhanced elimination while it was reduced in olanzapine and citalopram. However, in quetiapine, aripiprazole, sertraline and agomelatine, no changes were detected. These results suggest that P-glycoprotein polymorphisms could affect CNS drugs disposition, but the genetic factor that alters its activity is still unknown. This fact leads to consider the analysis of ABCB1 haplotypes instead of individual variants.

Peripheral biomarkers of major depression and antidepressant treatment response: Current knowledge and future outlooks

BACKGROUND

In recent years, we have accomplished a deeper understanding about the pathophysiology of major depressive disorder (MDD). Nevertheless, this improved comprehension has not translated to improved treatment outcome, as identification of specific biologic markers of disease may still be crucial to facilitate a more rapid, successful treatment. Ongoing research explores the importance of screening biomarkers using neuroimaging, neurophysiology, genomics, proteomics, and metabolomics measures.

RESULTS

In the present review, we highlight the biomarkers that are differentially expressed in MDD and treatment response and place a particular emphasis on the most recent progress in advancing technology which will continue the search for blood-based biomarkers.

LIMITATIONS

Due to space constraints, we are unable to detail all biomarker platforms, such as neurophysiological and neuroimaging markers, although their contributions are certainly applicable to a biomarker review and valuable to the field.

CONCLUSIONS

Although the search for reliable biomarkers of depression and/or treatment outcome is ongoing, the rapidly-expanding field of research along with promising new technologies may provide the foundation for identifying key factors which will ultimately help direct patients toward a quicker and more effective treatment for MDD.

Does G2677T Polymorphism of the MDR1 Gene Make a Difference in the Therapeutic Response to Paroxetine in Depressed Patients in a Slovakian Population?

Background

The role of multidrug resistance 1 gene (MDR1 or ABCB1) polymorphism G2677T was studied in relation to paroxetine therapeutic efficacy and its side effects, as well as its association with selected demographic and clinical characteristics of patients with depressive disorder.

Material/Methods

To evaluate therapeutic efficacy, all patients (n=61) were rated at week 0, 2, 4, and 6 using the Hamilton Rating Scale for Depression (HAMD-21). They were labelled as “responders” (a decrease in HAMD ≥50%) and “nonresponders”. The frequency of the side effects of nausea and sexual dysfunction were assessed using the Utvalg for Kliniske Undersogelser rating scale. The PCR-restriction fragment length polymorphism method was used for genotyping.

Results

A significantly enhanced therapeutic efficacy of paroxetine was observed in patients carrying at least one T allele at week 4 (GG versus GT: 0.049; GG versus GT+TT: 0.035) and week 6 (GG versus TT: 0.001; GG versus GT+TT: 0.016; GG+GT versus TT: 0.003; G versus T: 0.001). On the other hand, carriers of the T allele showed only a nonsignificant increase in HAMD-21 score reduction. In the present study, no significant association between G2677T polymorphism and side effects was detected. However, we found a marginally significant difference between GG and GT genotypes regarding family history of depressive disorder (p=0.049).

Conclusions

Our study provided evidence for the potential effect of MDR1 G2677T polymorphism on paroxetine therapeutic efficacy, and eventually on depressive disorder family history. Larger multicenter studies and studies across other ethnic groups are needed to elucidate the contradictory implications of G2677T polymorphism with depressive disorder and its treatment.

Nanomedicine applications in women's health: state of the art

State-of-the-art applications of nanomedicine have the potential to revolutionize the diagnosis, prevention, and treatment of a range of conditions and diseases affecting women’s health. In this review, we provide a synopsis of potential applications of nanomedicine in some of the most dominant fields of women’s health: mental health, sexual health, reproductive medicine, oncology, menopause-related conditions and dementia. We explore published studies arising from in vitro and in vivo experiments, and clinical trials where available, to reveal novel and highly promising therapeutic applications of nanomedicine in these fields. For the first time, we summarize the growing body of evidence relating to the use of nanomaterials as experimental tools for the detection, prevention, and treatment of significant diseases and conditions across the life course of a cisgender woman, from puberty to menopause; revealing the far-reaching and desirable theoretical impact of nanomedicine across different medical disciplines. We also present an overview of potential concerns regarding the therapeutic applications of nanomedicine and the factors currently restricting the growth of applied nanomedicine.

Blood-based biomarkers predicting response to antidepressants

Major depressive disorder is a common, serious and in some cases, life-threatening condition and affects approximately 350 million people globally. Although there is effective treatment available for it, more than 50% of the patients fail to respond to the first antidepressant they receive. The selection of a distinct treatment is still exclusively based on clinical judgment without incorporating lab-derived objective measures. However, there is growing evidence of biomarkers that it helps to improve diagnostic processes and treatment algorithms. Here genetic markers and blood-based biomarkers of the monoamine pathways, inflammatory pathways and the hypothalamic-pituitary-adrenal (HPA) axis are reviewed. Promising findings arise from studies investigating inflammatory pathways and immune markers that may identify patients suitable for anti-inflammatory based treatment regimes. Next, an early normalization of a disturbed HPA axis or depleted neurotrophic factors may predict stable treatment response. Genetic markers within the serotonergic system may identify patients who are vulnerable because of stressful life events, but evidence for guiding treatment regimes still is inconsistent. Therefore, there is still a great need for studies investigating and validating biomarkers for the prediction of treatment response to facilitate the treatment selection and shorten the time to remission and thus provide personalized medicine in psychiatry.

Pharmacogenomics and Biomarkers of Depression

The standard of care for antidepressant treatment in major depressive disorder (MDD) is a trial-and-error approach. Patients often have to undergo multiple medication trials for weeks to months before finding an effective treatment. Clinical factors such as severity of baseline symptoms and the presence of specific individual (anhedonia or insomnia) or cluster (atypical, melancholic, or anxious) of symptoms are commonly used without any evidence of their utility in selecting among currently available antidepressants. Genomic and proteomic biomarker have gained recent attention for their potential in informing antidepressant medication selection. In this report, we have reviewed some of the major pharmacogenomics studies along with individual genetic and proteomic biomarker of antidepressant response. Additionally, we have reviewed the blood-based protein biomarkers that can inform selection of one antidepressant over another. Among all currently available biomarkers, C-reactive protein (CRP) appears to be the most promising and pragmatic choice. Low CRP (<1 mg/L) in patients with MDD predicts better response to escitalopram while higher levels are associated with better response to noradrenergic/dopaminergic antidepressants. Future studies are needed to demonstrate the superiority of a CRP-based treatment assignment over high-quality measurement-based care in real-world clinical practices.

Concordance between actual and pharmacogenetic predicted desvenlafaxine dose needed to achieve remission in major depressive disorder: a 10-week open-label study

Supplemental Digital Content is available in the text.

Background

Pharmacogenetic-based dosing support tools have been developed to personalize antidepressant-prescribing practice. However, the clinical validity of these tools has not been adequately tested, particularly for specific antidepressants.

Objective

To examine the concordance between the actual dose and a polygene pharmacogenetic predicted dose of desvenlafaxine needed to achieve symptom remission.

Materials and methods

A 10-week, open-label, prospective trial of desvenlafaxine among Caucasian adults with major depressive disorder (n=119) was conducted. Dose was clinically adjusted and at the completion of the trial, the clinical dose needed to achieve remission was compared with the predicted dose needed to achieve remission.

Results

Among remitters (n=95), there was a strong concordance (Kendall’s τ-b=0.84, P=0.0001; Cohen’s κ=0.82, P=0.0001) between the actual and the predicted dose need to achieve symptom remission, showing high sensitivity (≥85%), specificity (≥86%), and accuracy (≥89%) of the tool.

Conclusion

Findings provide initial evidence for the clinical validity of a polygene pharmacogenetic-based tool for desvenlafaxine dosing.

Prenatal exposure to serotonin reuptake inhibitors and congenital heart anomalies: an exploratory pharmacogenetics study

AIM

To explore the role of pharmacogenetics in determining the risk of congenital heart anomalies (CHA) with prenatal use of serotonin reuptake inhibitors.

METHODS

We included 33 case-mother dyads and 2 mother-only (child deceased) cases of CHA in a case-only study. Ten genes important in determining fetal exposure to serotonin reuptake inhibitors were examined: CYP1A2, CYP2C9, CYP2C19, CYP2D6, ABCB1, SLC6A4, HTR1A, HTR1B, HTR2A and HTR3B.

RESULTS

Among the exposed cases, polymorphisms that tended to be associated with an increased risk of CHA were SLC6A4 5-HTTLPR and 5-HTTVNTR, HTR1A rs1364043, HTR1B rs6296 and rs6298 and HTR3B rs1176744, but none reached statistical significance due to our limited sample sizes.

CONCLUSION

We identified several polymorphisms that might potentially affect the risk of CHA among exposed fetuses, which warrants further investigation.

Pharmacogenomics in Asia: a systematic review on current trends and novel discoveries

While early pharmacogenomic studies have primarily been carried out in Western populations, there has been a notable increase in the number of Asian studies over the past decade. We systematically reviewed all pharmacogenomic studies conducted in Asia published before 2016 to highlight trends and identify research gaps in Asia. We observed that pharmacogenomic research in Asia was dominated by larger developed countries, notably Japan and Korea, and mainly driven by local researchers. Studies were focused on drugs acting on the CNS, chemotherapeutics and anticoagulants. Significantly, several novel pharmacogenomic associations have emerged from Asian studies. These developments are highly encouraging for the strength of regional scientific and clinical community and propound the importance of discovery studies in different populations.

Possibility of Predicting Serotonin Transporter Occupancy From the In Vitro Inhibition Constant for Serotonin Transporter, the Clinically Relevant Plasma Concentration of Unbound Drugs, and Their Profiles for Substrates of Transporters

Accurate prediction of target occupancy facilitates central nervous system drug development. In this review, we discuss the predictability of serotonin transporter (SERT) occupancy in human brain estimated from in vitro K_i values for human SERT and plasma concentrations of unbound drug (C_u,plasma), as well as the impact of drug transporters in the blood-brain barrier. First, the geometric means of in vitro K_i values were compared with the means of in vivo K_i values (K_i,u,plasma) which were calculated as C_u,plasma values at 50% occupancy of SERT obtained from previous clinical positron emission tomography/single photon emission computed tomography imaging studies for 6 selective serotonin transporter reuptake inhibitors and 3 serotonin norepinephrine reuptake inhibitors. The in vitro K_i values for 7 drugs were comparable to their in vivo K_i,u,plasma values within 3-fold difference. SERT occupancy was overestimated for 5 drugs (P-glycoprotein substrates) and underestimated for 2 drugs (presumably uptake transporter substrates, although no evidence exists as yet). In conclusion, prediction of human SERT occupancy from in vitro K_i values and C_u,plasma was successful for drugs that are not transporter substrates and will become possible in future even for transporter substrates, once the transporter activities will be accurately estimated from in vitro experiments.

Influence of ABCB1 polymorphisms and serum concentrations on venlafaxine response in patients with major depressive disorder

BACKGROUND

The pharmacokinetics and the pharmacodynamics of antidepressants show large inter-individual variations which result in unpredictable clinical responses.

AIM

The aim of the study was to examine the effect of ABCB1 polymorphisms and the serum concentrations on the efficacy and tolerability of venlafaxine in patients with major depressive disorder (MDD).

METHODS

Fifty-two outpatients who met the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition (DSM-IV) criteria for MDD were recruited for the study. The severity of depression was assessed using the 17-item Hamilton Rating Scale for Depression scale (HDRS₁₇) and tolerability was assessed based on a query regarding side-effects for 6 weeks. The ABCB1 C3435T/A and G2677T/A polymorphisms were genotyped by PCR/RFLP and steady-state serum venlafaxine concentrations were measured by high-performance liquid chromatography.

RESULTS

Patients with the TT genotype for the C3435T and the TT/TA genotype for the G2677T/A polymorphism showed significantly higher frequencies in venlafaxine-induced akathisia. This relationship was not observed for efficacy. As regards serum venlafaxine concentrations, patient groups showed no significant differences in efficacy and tolerability.

CONCLUSION

The results suggest that individuals with the TT-TT/TA genotypes for the C3435T-G2677T/A polymorphisms of ABCB1 may be pre-disposed to a risk of akathisia.

Quantification of the steady-state plasma concentrations of clozapine and N-desmethylclozapine in Japanese patients with schizophrenia using a novel HPLC method and the effects of CYPs and ABC transporters polymorphisms

Background This study developed a novel high-performance liquid chromatography (HPLC) method for the simultaneous quantification of clozapine and its active metabolite, N-desmethylclozapine, in human plasma and investigated the effects of various factors, including genetic polymorphisms in cytochrome P450 (CYP) 2D6, CYP3A5, ABCB1 and ABCG2, on the steady-state plasma trough concentrations (C₀) of clozapine and N-desmethylclozapine in Japanese patients with schizophrenia. Methods Forty-five patients had been receiving fixed doses of clozapine for at least four weeks. The CYP2D6 ( CYP2D6*2, CYP2D6*5, CYP2D6*10), CYP3A5 ( CYP3A5*3), ABCB1 (1236C > T, 2677G > T/A, 3435C > T) and ABCG2 (421 C > A) genotypes were identified by polymerase chain reaction. Results The within- and between-day coefficients of variation (CV) were less than 11.0%, and accuracy was within 9.0% over the linear range from 10 to 2500 ng/mL for both analytes, and their LOQs were each 10 ng/mL. The median C₀/dose (C₀/D) ratios of clozapine were significantly higher in patients with the ABCG2 421 A allele than in those with the 421 C/C genotype ( P = 0.010). However, there were no significant differences in C₀/D ratios of clozapine and N-desmethylclozapine among ABCB1, CYP2D6 or CYP3A5 genotypes. In multiple regression analysis, including polymorphisms, age, body weight and biochemical data of patients, the ABCG2 polymorphism alone was correlated with the C₀/D ratios of clozapine ( R²= 0.139, P = 0.016). Conclusions Among the various CYPs and drug transporters, BCRP appeared to most strongly influence clozapine exposure. Knowledge of the patient's ABCG2 421 C > A genotype before initiating therapy may be useful when making dosing decisions aimed at achieving optimal clozapine exposure.

Pharmacokinetic Modeling and Monte Carlo Simulation to Predict Interindividual Variability in Human Exposure to Oseltamivir and Its Active Metabolite, Ro 64-0802

Oseltamivir (Tamiflu®) is a prodrug of Ro 64-0802, a selective inhibitor of influenza virus neuraminidase. There is a possible relationship between oseltamivir treatment and neuropsychiatric adverse events; although this has not been established, close monitoring is recommended on the prescription label. The objective of this study was to predict interindividual variability of human exposure to oseltamivir and its active metabolite Ro 64-0802. By leveraging mathematical models and computations, physiological parameters in virtual subjects were generated with population means and coefficient of variations collected from the literature or produced experimentally. Postulated functional changes caused by genetic mutations in four key molecules, carboxylesterase 1A1, P-glycoprotein, organic anion transporter 3, and multidrug resistance-associated protein 4, were also taken into account. One hundred thousand virtual subjects were generated per simulation, which was iterated 20 times with different random number generator seeds. Even in the most exaggerated case, the systemic areas under the concentration-time curve (AUCs) of oseltamivir and Ro 64-0802 were increased by at most threefold compared with the population mean. By contrast, the brain AUCs of oseltamivir and Ro 64-0802 were increased up to about sevenfold and 40-fold, respectively, compared with the population means. This unexpectedly high exposure to oseltamivir or Ro 64-0802, which occurs extremely rarely, might trigger adverse central nervous system effects in the clinical setting.

Pharmacogenetics and Imaging-Pharmacogenetics of Antidepressant Response: Towards Translational Strategies

Genetic variation underlies both the response to antidepressant treatment and the occurrence of side effects. Over the past two decades, a number of pharmacogenetic variants, among these the SCL6A4, BDNF, FKBP5, GNB3, GRIK4, and ABCB1 genes, have come to the forefront in this regard. However, small effects sizes, mixed results in independent samples, and conflicting meta-analyses results led to inherent difficulties in the field of pharmacogenetics translating these findings into clinical practice. Nearly all antidepressant pharmacogenetic variants have potentially pleiotropic effects in which they are associated with major depressive disorder, intermediate phenotypes involved in emotional processes, and brain areas affected by antidepressant treatment. The purpose of this article is to provide a comprehensive review of the advances made in the field of pharmacogenetics of antidepressant efficacy and side effects, imaging findings of antidepressant response, and the latest results in the expanding field of imaging-pharmacogenetics studies. We suggest there is mounting evidence that genetic factors exert their impact on treatment response by influencing brain structural and functional changes during antidepressant treatment, and combining neuroimaging and genetic methods may be a more powerful way to detect biological mechanisms of response than either method alone. The most promising imaging-pharmacogenetics findings exist for the SCL6A4 gene, with converging associations with antidepressant response, frontolimbic predictors of affective symptoms, and normalization of frontolimbic activity following antidepressant treatment. More research is required before imaging-pharmacogenetics informed personalized medicine can be applied to antidepressant treatment; nevertheless, inroads have been made towards assessing genetic and neuroanatomical liability and potential clinical application.

ABCB1 genotyping in the treatment of depression

P-glycoprotein (P-gp), the gene product of ABCB1, is a drug transporter at the blood–brain barrier and could be a limiting factor for entrance of antidepressants into the brain, the target site of antidepressant action. Animal studies showed that brain concentrations of many antidepressants depend on P-gp. In humans, ABCB1 genotyping in the treatment of depression rests on the assumption that genetic variations in ABCB1 explain individual differences in antidepressant response via their effects on P-gp expression at the blood–brain barrier. High P-gp expression is hypothesized to lead to lower and often insufficient brain concentrations of P-gp substrate antidepressants. In this review, we summarize 32 studies investigating the question of whether ABCB1 polymorphisms predict clinical efficacy and/or tolerability of antidepressants in humans and evaluate the clinical application status of ABCB1 genotyping in depression treatment.

Reliability of In Vitro and In Vivo Methods for Predicting the Effect of P-Glycoprotein on the Delivery of Antidepressants to the Brain

As the effect of P-glycoprotein (P-gp) transport on antidepressant delivery has been extensively evaluated using in vitro cellular and in vivo rodent models, an increasing number of publications have addressed the effect of P-gp in limiting brain penetration of antidepressants and causing treatment-resistant depression in current clinical therapies. However, contradictory results have been observed in different systems. It is of vital importance to understand the potential for drug interactions related to P-gp at the blood-brain barrier (BBB), and whether coadministration of a P-gp inhibitor together with an antidepressant is a good clinical strategy for dosing of patients with treatment-resistant depression. In this review, the complicated construction of the BBB, the transport mechanisms for compounds that cross the BBB, and the basic characteristics of antidepressants are illustrated. Further, the reliability of different systems related to antidepressant brain delivery, including in vitro bidirectional transport cell lines, in vivo Mdr1 knockout mice, and chemical inhibition studies in rodents are analyzed, supporting a low possibility that P-gp affects currently marketed antidepressants when these results are extrapolated to the human BBB. These findings can also be applied to other central nervous system drugs.

The Risk of Congenital Heart Anomalies Following Prenatal Exposure to Serotonin Reuptake Inhibitors-Is Pharmacogenetics the Key?

Serotonin reuptake inhibitors (SRIs) are often prescribed during pregnancy. Previous studies that found an increased risk of congenital anomalies, particularly congenital heart anomalies (CHA), with SRI use during pregnancy have created concern among pregnant women and healthcare professionals about the safety of these drugs. However, subsequent studies have reported conflicting results on the association between CHA and SRI use during pregnancy. These discrepancies in the risk estimates can potentially be explained by genetic differences among exposed individuals. In this review, we explore the potential pharmacogenetic predictors involved in the pharmacokinetics and mechanism of action of SRIs, and their relation to the risk of CHA. In general, the risk is dependent on the maternal concentration of SRIs and the foetal serotonin level/effect, which can be modulated by the alteration in the expression and/or function of the metabolic enzymes, transporter proteins and serotonin receptors involved in the serotonin signalling of the foetal heart development. Pharmacogenetics might be the key to understanding why some children exposed to SRIs develop a congenital heart anomaly and others do not.

Polymorphisms in ATP-binding cassette transporter genes and interaction with diet and life style factors in relation to colorectal cancer in a Danish prospective case-cohort study

BACKGROUND AND AIMS

The ATP-binding cassette (ABC) transporter family transports various molecules across the enterocytes in the gut protecting the intestine against potentially harmful substances. Moreover, ABC transporters are involved in mucosal immune defence through interaction with cytokines. The study aimed to assess whether polymorphisms in ABCB1, ABCC2 and ABCG2 were associated with risk of colorectal cancer (CRC) and to investigate gene-environment (dietary factors, smoking and use of non-steroidal anti-inflammatory drugs) and gene-gene interactions between previously studied polymorphisms in IL1B and IL10 and ABC transporter genes in relation to CRC risk.

MATERIALS AND METHODS

We used a Danish prospective case-cohort study of 1010 CRC cases and 1829 randomly selected participants from the Danish Diet, Cancer and Health cohort. Incidence rate ratios were calculated based on Cox' proportional hazards model.

RESULTS

None of the polymorphisms were associated with CRC, but ABCB1 and ABCG2 haplotypes were associated with risk of CRC. ABCB1/rs1045642 interacted with intake of cereals and fiber (p-Value for interaction (P(int)) = 0.001 and 0.01, respectively). In a three-way analysis, both ABCB1/rs1045642 and ABCG2/rs2231137 in combination with IL10/rs3024505 interacted with fiber intake in relation to risk of CRC (P(int) = 0.0007 and 0.009).

CONCLUSIONS

Our results suggest that the ABC transporters P-glycoprotein/multidrug resistance 1 and BRCP, in cooperation with IL-10, are involved in the biological mechanism underlying the protective effect of fiber intake in relation to CRC. These results should be replicated in other cohorts to rule out chance findings.

Impact of Genetic Polymorphisms of ABCB1 (MDR1, P-Glycoprotein) on Drug Disposition and Potential Clinical Implications: Update of the Literature

ATP-binding cassette transporter B1 (ABCB1; P-glycoprotein; multidrug resistance protein 1) is an adenosine triphosphate (ATP)-dependent efflux transporter located in the plasma membrane of many different cell types. Numerous structurally unrelated compounds, including drugs and environmental toxins, have been identified as substrates. ABCB1 limits the absorption of xenobiotics from the gut lumen, protects sensitive tissues (e.g. the brain, fetus and testes) from xenobiotics and is involved in biliary and renal secretion of its substrates. In recent years, a large number of polymorphisms of the ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1] gene have been described. The variants 1236C>T (rs1128503, p.G412G), 2677G>T/A (rs2032582, p.A893S/T) and 3435C>T (rs1045642, p.I1145I) occur at high allele frequencies and create a common haplotype; therefore, they have been most widely studied. This review provides an overview of clinical studies published between 2002 and March 2015. In summary, the effect of ABCB1 variation on P-glycoprotein expression (messenger RNA and protein expression) and/or activity in various tissues (e.g. the liver, gut and heart) appears to be small. Although polymorphisms and haplotypes of ABCB1 have been associated with alterations in drug disposition and drug response, including adverse events with various ABCB1 substrates in different ethnic populations, the results have been majorly conflicting, with limited clinical relevance. Future research activities are warranted, considering a deep-sequencing approach, as well as well-designed clinical studies with appropriate sample sizes to elucidate the impact of rare ABCB1 variants and their potential consequences for effect sizes.

Association between ABCB1 Polymorphisms and Antidepressant Treatment Response in Taiwanese Major Depressive Patients

Objective

The multidrug resistance 1 (ABCB1, MDR1) gene, encoding P-glycoprotein, is extensively distributed and expressed in various tissues, such as a blood-brain barrier transporter. P-glycoprotein plays an important role in controlling the passage of substances between the blood and brain. The current study aimed to investigate possible associations of functional ABCB1 polymorphisms (C3435T, G2677T and C1236T) with response to antidepressant treatment and serum cortisol levels in Taiwanese patients with major depressive disorder (MDD).

Methods

We recruited 112 MDD patients who were randomized to fluoxetine (n=58, mean dose: 21.4±4.5 mg/day) or venlafaxine (n=54, 80.2±34.7 mg/day) treatment for 6 weeks. The 21-item Hamilton Depression Rating Scale (HDRS) was administered initially and biweekly after treatment, and cortisol levels were assessed initially and after 6-week antidepressant treatment.

Results

The initial HDRS scores and the HDRS scores after six weeks of antidepressant treatment were not significantly different among the different genotypes in each polymorphism of ABCB1. The percentage changes of HDRS scores over time were significantly different in the polymorphisms of ABCB1 G2677T (p=0.002). MDD patients with the G/G genotype of ABCB1 G2677T had a worse antidepressant treatment response. However, the polymorphisms of ABCB1 genotypes were not significantly associated with cortisol levels before and after antidepressant treatment in MDD patients.

Conclusion

The results suggested that the variants of ABCB1 may influence the short-term antidepressant response in MDD patients. Further details of the underlying mechanisms of ABCB1 in antidepressant treatment remain to be clarified.

Exposure-outcome analysis in depressed patients treated with paroxetine using population pharmacokinetics

Purpose

This study investigated population pharmacokinetics of paroxetine, and then performed an integrated analysis of exposure and clinical outcome using population pharmacokinetic parameter estimates in depressed patients treated with paroxetine.

Patients and methods

A total of 271 therapeutic drug monitoring (TDM) data were retrospectively collected from 127 psychiatric outpatients. A population nonlinear mixed-effects modeling approach was used to describe serum concentrations of paroxetine. For 83 patients with major depressive disorder, the treatment response rate and the incidence of adverse drug reaction (ADR) were characterized by logistic regression using daily dose or area under the concentration–time curve (AUC) estimated from the final model as a potential exposure predictor.

Results

One compartment model was developed. The apparent clearance of paroxetine was affected by age as well as daily dose administered at steady-state. Overall treatment response rate was 72%, and the incidence of ADR was 30%. The logistic regression showed that exposure predictors were not associated with treatment response or ADR in the range of dose commonly used in routine practice. However, the incidence of ADR increased with the increase of daily dose or AUC for the patients with multiple concentrations.

Conclusion

In depressed patients treated with paroxetine, TDM may be of limited value for individualization of treatment.

Improved Antidepressant Remission in Major Depression via a Pharmacokinetic Pathway Polygene Pharmacogenetic Report

Objective

Major depressive disorder (MDD) is projected to be a leading cause of disability globally by 2030. Only a minority of patients remit with antidepressants. If assay of polymorphisms influencing central nervous system (CNS) bioavailability could guide prescribers to more effectively dose patients, remission rates may improve and the burden of disease from MDD reduce. Hepatic and blood brain barrier (BBB) polymorphisms appear to influence antidepressant CNS bioavailability.

Methods

A 12-week prospective double blind randomized genetically guided versus unguided trial of antidepressant dosing in Caucasian adults with MDD (n=148) was conducted.

Results

Subjects receiving genetically guided prescribing had a 2.52-fold greater chance of remission (95% confidence interval [CI]=1.71–3.73, z=4.66, p<0.0001). The number needed to genotype (NNG)=3 (95% CI=1.7–3.5) to produce an additional remission.

Conclusion

These data suggest that a pharmacogenetic dosing report (CNSDose^®) improves antidepressant efficacy. The effect size was sufficient that translation to clinical care may arise if results are independently replicated.

Pharmacogenetics of major depressive disorder: top genes and pathways toward clinical applications

The pharmacogenetics of antidepressants has been not only a challenging but also frustrating research field since its birth in the 1990s. Indeed, great expectations followed the first evidence of familiar aggregation of antidepressant response. Despite the progress from candidate gene studies to genome-wide association studies (GWAS), results fell out the expectations and they were often inconsistent. Anyway, the cumulative evidence supports the involvement of some genes and molecular pathways in antidepressant efficacy. The best single genes are SLC6A4, HTR2A, BDNF, GNB3, FKBP5, ABCB1, and cytochrome P450 genes (CYP2D6 and CYP2C19). Molecular pathways involved in inflammation and neuroplasticity show the greatest support. The first studies evaluating benefits of genotype-guided antidepressant treatments provided encouraging results and confirmed the relevance of SLC6A4, HTR2A, ABCB1, and cytochrome P450 genes. Further progress in genotyping and data analysis would allow to move forward and complete the understanding of antidepressant pharmacogenetics and its translation into clinical applications.

ABCB1 gene variants and antidepressant treatment outcome: A meta-analysis

The efflux pump P-glycoprotein (P-gp), a gene product of the ABCB1 gene, plays a pivotal role in the transfer of various molecules across the blood-brain barrier. P-gp protects the brain by selectively extruding its substrates, including certain antidepressive drugs, thereby limiting their uptake into the brain. Uhr et al. [2008] first showed that ABCB1 variants predicted the remission to antidepressants with P-gp substrate properties in patients suffering from major depression (MD). Other studies investigating the influence of ABCB1 polymorphisms on antidepressant treatment response produced inconclusive results. In this meta-analysis, we systematically summarized 16 pharmacogenetic studies focused on the association of ABCB1 variants and antidepressant treatment outcome in patients with MD (overall n = 2695). We investigated the association of treatment outcome and six ABCB1 single nucleotide polymorphisms (SNPs): rs2032583, rs2235015, rs2235040, rs1045642, rs2032582, rs1128503. We stratified for admission status, ethnicity, and prescription of concomitant medication. SNP rs2032583 showed a nominally significant association across all studies (P = 0.035, SNP was studied in a total of 2,037 patients) and a significant Bonferroni-corrected association among inpatients (P = 1.5 × 10(-05) , n = 485). Also SNP rs2235015 was significantly associated with antidepressant treatment outcome withstanding Bonferroni correction (P = 3.0 × 10(-04) ) among inpatients in a smaller subsample (n = 195). There were no significant associations of the other SNPs tested with antidepressant treatment outcome. Future pharmacogenetic association studies should focus on the role of the ABCB1 SNP rs2032583 in antidepressant outcome prediction.

Pharmacogenetics and analgesic effects of antidepressants in chronic pain management

Antidepressants are widely administered to chronic pain patients, but there is large interindividual variability in their efficacy and adverse effect rates that may be attributed to genetic factors. Studies have attempted to determine the impact of genetic polymorphisms in enzymes and transporters that are involved in antidepressant pharmacokinetics, for example, cytochrome P450 and P-gp. The impacts of genetic polymorphisms in the targets of antidepressants, such as the serotonin receptor or transporter, the noradrenaline transporter and the COMT and monoamine oxydase enzymes, have also been described. This manuscript discusses the current knowledge of the influence of genetic factors on the plasma concentrations, efficacy and adverse effects of the major antidepressants used in pain management.

Genetic variants in combination with early partial improvement as a clinical utility predictor of treatment outcome in major depressive disorder: the result of two pooled RCTs

Pharmacogenetics may allow for a personalized treatment, but a combination with clinical variables may further enhance prediction. In particular, in the present paper, we investigated early partial improvement (EPI) defined as 20% or more improvement by rating scales 2  weeks after treatment, in combination with selected gene variants as a predictor of treatment outcome in patients with major depressive disorder. Two randomized controlled trials with 168 Japanese depressed patients were used. A stepwise multiple linear regression model with HAM-D score change at week 6 as the dependent variable and genotypes, EPI, baseline HAM-D score, age and sex as independent variables was performed in paroxetine, fluvoxamine and milnacipran, respectively, to estimate the prediction of HAM-D change at week 6. In the paroxetine sample, only EPI (P<0.001) was significantly associated with HAM-D change (n=81, R(2)=0.25, P<0.001). In the fluvoxamine sample, 5-HTTLPR La/Lg, S (P=0.029), FGF2 rs1449683C/T (P=0.013) and EPI (P=0.003) were associated with HAM-D change (n=42, R(2)=0.43, P<0.001). In the milnacipran sample, HTR-1A-1019C/G (P=0.001), ADRA2A-1297C/G (P=0.028) and EPI (P<0.001) were associated with outcome (n=45, R(2)=0.71, P<0.001). EPI in combination with genetic variants could be a useful predictor of treatment outcome and could strengthen the practical use of pharmacogenetic data in clinical practice.

The Influence of C3435T Polymorphism of the ABCB1 Gene on Genetic Susceptibility to Depression and Treatment Response in Polish Population - Preliminary Report

BACKGROUND

Despite the high prevalence of depression, the mechanism of the origin of this disease as well as the causes of resistance to therapy in some patients are still not fully understood. Increasingly, the possible role of genetic factors is considered. One of them is polymorphisms in the ABCB1 (MDR1) gene which encodes P-glycoprotein, responsible for the transport of xenobiotics, including antidepressant drugs, through the blood-brain barrier.

METHODS

C3435T was evaluated in 90 patients with recurrent depressive disorders (rDD). Genotyping was performed using a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The obtained results indicate that the TT genotype occurred more frequently among patients with rDD than in healthy volunteers (p=0.0441). Also, at least one C allele was present significantly less frequent in the study group than in healthy individuals (p=0.0300). The severity of depressive symptoms was higher among patient with the CC genotype in comparison with the other genotypes (p=0.0106) but treatment response to antidepressants was better in this group than among patients with CT or TT genotypes (p=0.0301). Likewise, patients with the T allele have a significantly lower severity of symptoms (p=0.0026) and decreased therapy effectiveness (p=0.0142) than C allele carriers.

CONCLUSIONS

This study suggests that C3435T polymorphisms in the ABCB1 gene are strongly associated with a predisposition to depression development, the severity of depressive symptoms and the effectiveness of therapy with using different groups of antidepressant agents.

ABCB1 (MDR1) predicts remission on P-gp substrates in chronic depression

The hypothesis that allelic variation in the multidrug resistance-1 (MDR1 or ABCB1) gene encoding the P-glycoprotein (P-gp) blood-brain barrier efflux pump is associated with remission and side effects was tested in chronic major depression patients treated with P-gp substrates. In 83 patients from the REVAMP trial, frequency of and time to remission as well as side effects was tested among genotype groups at 6 ABCB1 single nucleotide polymorphisms (SNPs). These six SNPs are significantly associated with remission and time to remission, with minor allele carriers on rs2235040 and rs9282564 attaining statistical significance after controlling for the other ABCB1 SNPs. The six ABCB1 SNPs are also significantly associated with the average side effects. However, here common homozygotes on rs2235040 and rs9282564 demonstrated significantly higher side effects after controlling for the effects of the other ABCB1 SNPs. These findings confirm and extend previous observations that minor alleles of two ABCB1 SNPs predict remission to treatment with substrates and demonstrate that common homozygotes on these SNPs experience greater side effects. Results point to the potential importance of ABCB1 variation for personalized medicine approaches to treating depression.

Understanding the pharmacogenetics of selective serotonin reuptake inhibitors

INTRODUCTION

The genetic background of antidepressant response represents a unique opportunity to identify biological markers of treatment outcome. Encouraging results alternating with inconsistent findings made antidepressant pharmacogenetics a stimulating but often discouraging field that requires careful discussion about cumulative evidence and methodological issues.

AREAS COVERED

The present review discusses both known and less replicated genes that have been implicated in selective serotonin reuptake inhibitors (SSRIs) efficacy and side effects. Candidate genes studies and genome-wide association studies (GWAS) were collected through MEDLINE database search (articles published till January 2014). Further, GWAS signals localized in promising genetic regions according to candidate gene studies are reported in order to assess the general comparability of results obtained through these two types of pharmacogenetic studies. Finally, a pathway enrichment approach is applied to the top genes (those harboring SNPs with p < 0.0001) outlined by previous GWAS in order to identify possible molecular mechanisms involved in SSRI effect.

EXPERT OPINION

In order to improve the understanding of SSRI pharmacogenetics, the present review discusses the proposal of moving from the analysis of individual polymorphisms to genes and molecular pathways, and from the separation across different methodological approaches to their combination. Efforts in this direction are justified by the recent evidence of a favorable cost-utility of gene-guided antidepressant treatment.

ABCB6, ABCB1 and ABCG1 genetic polymorphisms and antidepressant response of SSRIs in Chinese depressive patients

AIM

Major depressive disorder is a common psychiatric disorder with worldwide prevalence. The most widely prescribed antidepressants are selective serotonin reuptake inhibitors (SSRIs). ATP-binding cassette proteins are responsible for the membrane transport of various molecules including antidepressive drugs. We investigated whether SNPs in ABCB6, ABCB1 and ABCG1 were associated with the treatment response of SSRIs.

MATERIALS & METHODS

A pharmacogenetic study genotyping nine SNPs was conducted in 290 major depressive disorder patients in the Chinese Han population. Allele and genotype frequencies were compared between responders and nonresponders.

RESULTS

The allele frequencies of rs28401781 and rs4148739 in ABCB1 showed significant difference between responders and nonresponders before correction (p = 0.0297 and p = 0.0359, respectively). No significant associations were detected for the ABCB6 or ABCG1 gene.

CONCLUSION

Our results suggest that ABCB1 polymorphisms might be associated with SSRIs treatment response in the Chinese Han population.

Increased genetic diversity of ADME genes in African Americans compared with their putative ancestral source populations and implications for pharmacogenomics

BACKGROUND

African Americans have been treated as a representative population for African ancestry for many purposes, including pharmacogenomic studies. However, the contribution of European ancestry is expected to result in considerable differences in the genetic architecture of African American individuals compared with an African genome. In particular, the genetic admixture influences the genomic diversity of drug metabolism-related genes, and may cause high heterogeneity of drug responses in admixed populations such as African Americans.

RESULTS

The genomic ancestry information of African-American (ASW) samples was obtained from data of the 1000 Genomes Project, and local ancestral components were also extracted for 32 core genes and 252 extended genes, which are associated with drug absorption, distribution, metabolism, and excretion (ADME) genes. As expected, the global genetic diversity pattern in ASW was determined by the contributions of its putative ancestral source populations, and the whole profiles of ADME genes in ASW are much closer to those in YRI than in CEU. However, we observed much higher diversity in some functionally important ADME genes in ASW than either CEU or YRI, which could be a result of either genetic drift or natural selection, and we identified some signatures of the latter. We analyzed the clinically relevant polymorphic alleles and haplotypes, and found that 28 functional mutations (including 3 missense, 3 splice, and 22 regulator sites) exhibited significantly higher differentiation between the three populations.

CONCLUSIONS

Analysis of the genetic diversity of ADME genes showed differentiation between admixed population and its ancestral source populations. In particular, the different genetic diversity between ASW and YRI indicated that the ethnic differences in pharmacogenomic studies are broadly existed despite that African ancestry is dominant in Africans Americans. This study should advance our understanding of the genetic basis of the drug response heterogeneity between populations, especially in the case of population admixture, and have significant implications for evaluating potential inter-population heterogeneity in drug treatment effects.

The clinical application of ABCB1 genotyping in antidepressant treatment: a pilot study

BACKGROUND

The gene product of the ABCB1 gene, the P-glycoprotein, functions as a custodian molecule in the blood-brain barrier and regulates the access of most antidepressants into the brain. Previous studies showed that ABCB1 polymorphisms predicted the response to antidepressants that are substrates of the P-gp, while the response to nonsubstrates was not influenced by ABCB1 polymorphisms. The aim of the present study was to evaluate the clinical application of ABCB1 genotyping in antidepressant pharmacotherapy.

METHODS

Data came from 58 depressed inpatients participating in the Munich Antidepressant Response Signature (MARS) project, whose ABCB1 gene test results were implemented into the clinical decision making process. Hamilton Depression Rating Scale (HAM-D) scores, remission rates, and duration of hospital stay were documented with dose and kind of antidepressant treatment.

RESULTS

Patients who received ABCB1 genotyping had higher remission rates [χ2(1) = 6.596, p = 0.005, 1-sided] and lower Hamilton sores [t(111) = 2.091, p = 0.0195, 1-sided] at the time of discharge from hospital as compared to patients without ABCB1 testing. Among major allele homozygotes for ABCB1 single nucleotide polymorphisms (SNPs) rs2032583 and rs2235015 (TT/GG genotype), an increase in dose was associated with a shorter duration of hospital stay [rho(28) = -0.441, p = 0.009, 1-sided], whereas other treatment strategies (eg, switching to a nonsubstrate) showed no significant associations with better treatment outcome. Discussion The implementation of ABCB1 genotyping as a diagnostic tool influenced clinical decisions and led to an improvement of treatment outcome. Patients carrying the TT/GG genotype seemed to benefit from an increase in P-gp substrate dose.

CONCLUSION

Results suggest that antidepressant treatment of depression can be optimized by the clinical application of ABCB1 genotyping.

Innovative drugs to treat depression: did animal models fail to be predictive or did clinical trials fail to detect effects?

Over recent decades, encouraging preclinical evidence using rodent models pointed to innovative pharmacological targets to treat major depressive disorder. However, subsequent clinical trials have failed to show convincing results. Two explanations for these rather disappointing results can be put forward, either animal models of psychiatric disorders have failed to predict the clinical effectiveness of treatments or clinical trials have failed to detect the effects of these new drugs. A careful analysis of the literature reveals that both statements are true. Indeed, in some cases, clinical efficacy has been predicted on the basis of inappropriate animal models, although the contrary is also true, as some clinical trials have not targeted the appropriate dose or clinical population. On the one hand, refinement of animal models requires using species that have better homological validity, designing models that rely on experimental manipulations inducing pathological features, and trying to model subtypes of depression. On the other hand, clinical research should consider carefully the results from preclinical studies, in order to study these compounds at the correct dose, in the appropriate psychiatric nosological entity or symptomatology, in relevant subpopulations of patients characterized by specific biomarkers. To achieve these goals, translational research has to strengthen the dialogue between basic and clinical science.