Polymorphisms in the SLC6A4 and HTR2A genes influence treatment outcome following antidepressant therapy

Pharmacogenetics of selective serotonin reuptake inhibitors (SSRI): A serotonin reuptake transporter (SERT)-based approach

Neuropsychiatric disorders are considered to be the most common cause of disability worldwide. Serotonin and its transporter is a prominent paradigm in mood disorders. Response to selective serotonin reuptake inhibitors (SSRI) is altered due to heterogeneity in the serotonin transporter gene, SLC6A4 (solute carrier family 6 member 4). The reported polymorphisms are found to be in different regions of the transporter gene: promoter region (5-HTTLPR and various single nucleotide polymorphisms within it), intron (STin2), and exon 9 (I425V). The long and short alleles of the 5-HTTLPR gene, which are prevalent among variations, may mediate differential effects. In long allelic variant carriers, an increased response to SSRI and timely recovery is due to increased availability of SERT. Whereas, SERT availability is significantly decreased in short allelic carriers, necessitating a reduction in SSRI dosage due to the increased risk of adverse drug reactions. Thus, pharmacogenetic investigations are required to understand the impact of functional variations on the efficacy and tolerability of SSRI. Identifying the carrier variants may aid in clear-decision making of the treatment regimen, aiding the approach of personalized medication.

Pharmacogenetic Factors Influence Escitalopram Pharmacokinetics and Adverse Events in Youth with a Family History of Bipolar Disorder: A Preliminary Study

Introduction: Escitalopram is an effective and generally well-tolerated antidepressant, but children of parents with bipolar disorder (BD) may be at increased risk for adverse events associated with antidepressants, including increased irritability, restlessness, impulsivity, and manic symptoms. This risk may be influenced by polymorphisms in genes encoding cytochrome P450 enzymes (CYP2C19 or CYP2D6), the serotonin transporter (SLC6A4), and the serotonin receptor 2A subtype (HTR2A). We explored whether gene-drug interactions influence the emergence of adverse events in depressed and/or anxious youth with a family history of BD. Materials and Methods: Children and adolescents aged 12-17 years with a first-degree relative with bipolar I disorder were treated with escitalopram and monitored for adverse effects, underwent pharmacogenetic testing, and provided serum escitalopram levels. Emergence of adverse events was determined by study clinicians, and symptoms were tracked using the Treatment-Emergent Activation and Suicidality Assessment Profile (TEASAP) and Pediatric Adverse Events Rating Scale. Clinical Pharmacogenetics Implementation Consortium guidelines were used to determine CYP2C19 and CYP2D6 phenotypes. Results: Slower CYP2C19 metabolizers had greater dose-normalized 24-hour area under the curve (AUC0-24; p = 0.025), trough concentrations (Ctrough; p = 0.013), and elimination half-lives (t1/2; p < 0.001). CYP2D6 phenotype was not significantly associated with any pharmacokinetic parameter. Slower CYP2D6 metabolizers had increased TEASAP akathisia (p = 0.015) scores. HTR2A A/A and A/G genotypes were associated with increased TEASAP "self-injury, suicidality, and harm to others" subscale scores (p = 0.017). Escitalopram maximum concentration, AUC0-24, CYP2C19 phenotype, and SLC6A4 genotype were not associated with adverse events. Conclusions: CYP2C19 phenotype influences escitalopram pharmacokinetics whereas CYP2D6 phenotype does not. Slower CYP2D6 metabolism was associated with increased akathisia, and HTR2A A/A or A/G genotypes were associated with increased risk of self-harm or harm to others. Larger cohorts are needed to identify associations between genetic test results and antidepressant-associated adverse events. Trial Registration: ClinicalTrials.gov identifier: NCT02553161.

Genetic Landscape of Major Depressive Disorder: Assessment of Potential Diagnostic and Antidepressant Response Markers

BACKGROUND

The clinical heterogeneity in major depressive disorder (MDD), variable treatment response, and conflicting findings limit the ability of genomics toward the discovery of evidence-based diagnosis and treatment regimen. This study attempts to curate all genetic association findings to evaluate potential variants for clinical translation.

METHODS

We systematically reviewed all candidates and genome-wide association studies for both MDD susceptibility and antidepressant response, independently, using MEDLINE, particularly to identify replicated findings. These variants were evaluated for functional consequences using different in silico tools and further estimated their diagnostic predictability by calculating positive predictive values.

RESULTS

A total of 217 significantly associated studies comprising 1200 variants across 545 genes and 128 studies including 921 variants across 412 genes were included with MDD susceptibility and antidepressant response, respectively. Although the majority of associations were confirmed by a single study, we identified 31 and 18 replicated variants (in at least 2 studies) for MDD and antidepressant response. Functional annotation of these 31 variants predicted 20% coding variants as deleterious/damaging and 80.6% variants with regulatory effect. Similarly, the response-related 18 variants revealed 25% coding variant as damaging and 88.2% with substantial regulatory potential. Finally, we could calculate the diagnostic predictability of 19 and 5 variants whose positive predictive values ranges from 0.49 to 0.66 for MDD and 0.36 to 0.66 for response.

CONCLUSIONS

The replicated variants presented in our data are promising for disease diagnosis and improved response outcomes. Although these quantitative assessment measures are solely directive of available observational evidence, robust homogenous validation studies are required to strengthen these variants for molecular diagnostic application.

Examining Whether Genetic Variants Moderate the Skeletal Effects of Selective Serotonin Reuptake Inhibitors in Older Adolescents and Young Adults

Objective: To examine whether serotonin (5-HT) related genetic variants moderate the effects of selective serotonin reuptake inhibitors (SSRIs) on skeletal outcomes. Methods: Trabecular bone mineral density (BMD) at the radius, lumbar spine (LS) BMD, total body less head (TBLH) bone mineral content (BMC) and markers of bone metabolism (osteocalcin, C-terminal telopeptide of type I collagen [CTX-1], and bone specific alkaline phosphatase to CTX-1 ratio) were examined in an observational study, enrolling 15- to 20-year-old participants, unmedicated or within a month of SSRI initiation. Variants in HTR1A (rs6295), HTR1B (rs6296), HTR1D (rs6300), HTR2A (rs6311 and rs6314), HTR2B (rs6736017), and the serotonin transporter intron 2 variable number tandem repeat (STin2 VNTR) were genotyped. Linear mixed-effects regression analysis examined associations between SSRI use, genetic variants, and skeletal outcomes. Results: After adjusting for relevant covariates, rs6295 CC and GC genotypes in 262 participants (60% female, mean ± SD age = 18.9 ± 1.6 years) were significantly associated with higher LS BMD compared to the GG genotype. Rs6311 GG SSRI users had greater LS BMD compared to nonusers (β = 0.18, p = <0.0001). Female SSRI users with the combination of rs6295 CC+GC and rs6311 GG genotypes had greater LS BMD than female SSRI nonusers (β = 0.29, p < 0.0001). SSRI users with the rs6295 GG genotype had higher trabecular BMD compared to nonusers (β = 3.60, p = 0.05). No significant interactions were found for TBLH BMC or bone turnover markers. After correcting for multiple comparisons, none of the results retained significance. Conclusions: In older adolescents and young adults, HTR1A (rs6295) and HTR2A (rs6311) variants may moderate the effect of SSRIs on BMD. Sex differences may exist and require further examination. Further research with larger sample sizes is needed to confirm our preliminary findings. Clinical Trial Registration: clinicaltrials.gov NCT02147184.

In silico analysis of a SLC6A4 G100V mutation in lung cancers

SLC6A4 is a serotonin re-uptake transporter which has been a target for anti-depressant therapies but recently some mutations have been described in cancer cells. Here, we characterize mutations in SLC6A4 that appear in cancer cells. We employed several validated computational and artificial intelligence algorithms to characterize the mutations. We identified a previously uncharacterized G100V mutation in lung cancers. In sillico structural analysis reveals that this mutation may affect SLC6A4 ligand binding and subsequently its function. We also identified several other mutations that may affect the structure of the protein. This preliminary analysis highlights the role of SLC6A4 in human cancers.

Pharmacokinetics of immediate and sustained-release formulations of paroxetine: Population pharmacokinetic approach to guide paroxetine personalized therapy in chinese psychotic patients

Paroxetine is one of the most potent selective serotonin reuptake inhibitors (SSRIs) approved for treating depression, panic disorder, and obsessive-compulsive disorder. There is evidence linking genetic polymorphisms and nonlinear metabolism to the Paroxetine’s pharmacokinetic (PK) variability. The purpose of the present study was to develop a population PK (PPK) model of paroxetine in Chinese patients, which was used to define the paroxetine’s PK parameters and quantify the effect of clinical and baseline demographic factors on these PK characteristics. The study included 184 inpatients with psychosis (103 females and 81 males), with a total of 372 serum concentrations of paroxetine for PPK analyses. The total daily dosage ranged from 20 to 75 mg. One compartment model could fit the PKs characterize of paroxetine. Covariate analysis revealed that dose, formulation, and sex had a significant effect on the PK parameters of paroxetine; however, there was no evident genetic influence of CYP2D6 enzymes on paroxetine concentrations in Chinese patients. The study determined that the population’s apparent distribution volume (V/F) and apparent clearance (CL/F), respectively, were 8850 and 21.2 L/h. The CL/F decreased 1-2-fold for each 10 mg dose increase, whereas the different formulations caused a decrease in V/F of 66.6%. Sex was found to affect bioavailability (F), which decreased F by 47.5%. Females had higher F values than males. This PPK model described data from patients with psychosis who received paroxetine immediate-release tablets (IR-T) and/or sustained-release tablets (SR-T). Paroxetine trough concentrations and relative bioavailability were different between formulations and sex. The altered serum concentrations of paroxetine resulting from individual variants and additive effects need to be considered, to optimize the dosage regimen for individual patients.

Role of serotonin transporter and receptor gene polymorphisms in treatment response to selective serotonin reuptake inhibitors in major depressive disorder

OBJECTIVE

Significant challenges in the management of major depressive disorder include the lag period from treatment initiation to an evident response, low response rates and unpredictable disparities in outcome between patients. As a large part of these has been linked to genetic mechanisms, we tried to establish a relationship between genes associated with serotonin neurotransmission and outcome to selective serotonin reuptake inhibitor (SSRI) treatment.

METHODS

One hundred and twenty-five patients with moderate to severe depression [at least 15 on the Hamilton Depression (HAM-D) Rating Scale] being started on SSRI were recruited. Those with a reduction of at least 50% from baseline or an absolute score of 7 or less after 8 weeks of treatment were considered as responders. The serotonin transporter linked polymorphic region 5HTTLPR, serotonin transporter intron 2 (STin2) polymorphism and the 5-HT receptor 1A rs6295 polymorphisms were studied in association with outcome.

RESULTS

The l/l genotype of the 5HTTLPR was associated with greater likelihood of response (OR: 4.65, CI: 1.74-12.38, p = 0.003). Patients with the 12/12 repeat variant of the STin2 VNTR polymorphism showed a greater reduction in HAM-D score, compared to patients with the 10/10 genotype (OR: 0.12, CI: 0.03-0.44, p = 0.001). We found no association of the 5HTR1Ars6295 polymorphism with response.

CONCLUSIONS

The 5HTTLPR polymorphism and the SLC6A4 intron 2 polymorphism were associated with treatment response, with the l/l genotype and 12-copy allele showing a tendency towards better outcomes, respectively.

Serotonin Transporter Genetic Variation and Antidepressant Response and Tolerability: A Systematic Review and Meta-Analysis

Antidepressants are used to treat several psychiatric disorders; however, a large proportion of patients do not respond to their first antidepressant therapy and often experience adverse drug reactions (ADR). A common insertion–deletion polymorphism in the promoter region (5-HTTLPR) of the serotonin transporter (SLC6A4) gene has been frequently investigated for its association with antidepressant outcomes. Here, we performed a systematic review and meta-analysis to assess 5-HTTLPR associations with antidepressants: (1) response in psychiatric disorders other than major depressive disorder (MDD) and (2) tolerability across all psychiatric disorders. Literature searches were performed up to January 2021, yielding 82 studies that met inclusion criteria, and 16 of these studies were included in the meta-analyses. Carriers of the 5-HTTLPR LL or LS genotypes were more likely to respond to antidepressant therapy, compared to the SS carriers in the total and European ancestry-only study populations. Long (L) allele carriers taking selective serotonin reuptake inhibitors (SSRIs) reported fewer ADRs relative to short/short (SS) carriers. European L carriers taking SSRIs had lower ADR rates than S carriers. These results suggest the 5-HTTLPR polymorphism may serve as a marker for antidepressant outcomes in psychiatric disorders and may be particularly relevant to SSRI treatment among individuals of European descent.

A Meta-Analysis of 5-Hydroxytryptamine Receptor 1B Polymorphisms With Risk of Major Depressive Disorder and Suicidal Behavior

Purpose: Previous association studies have investigated whether genetic polymorphisms in HTR1B influenced individuals' susceptibility to major depressive disorder (MDD), anti-depressant response (ADR) and suicidal behavior. However, equivocal evidence was obtained. In this meta-analysis, we aimed to examine the association of HTR1B polymorphisms with risk of MDD, ADR and suicidal behavior. Materials and Methods: Studies evaluating the association between HTR1B polymorphisms and risk of MDD, ADR and suicidal behavior were searched in Pubmed, Ovid Medline, web of science and China National Knowledge Infrastructure databases. Summary odds ratios (ORs), 95 % confidence intervals (CIs) and p-values were calculated using a fixed or random effects model. Results: Meta-analysis findings revealed a significantly increased risk of MDD with rs6296 GC and GC/CC genotypes (GC vs. GG: OR = 1.26, 95% CI, 1.07-1.48; GC/CC vs. GG: OR = 1.22, 95% CI, 1.04-1.43, respectively). Moreover, rs6298 CT genotype was significantly associated with an increased risk of suicidal behavior (CT vs. CC: OR = 1.48, 95% CI, 1.16-1.88). However, both rs6296 and rs130058 were not significant risk factors for lethal suicidal behavior. Conclusion: This meta-analysis identified that rs6296 and rs6298 in HTR1B may be significantly related to the risk of MDD and lethality of suicide attempts, respectively. Further studies are required to assess the markers in larger cohorts.

Associations between the 1438A/G, 102T/C, and rs7997012G/A polymorphisms of HTR2A and the safety and efficacy of antidepressants in depression: a meta-analysis

The correlations between hydroxytryptamine receptor 2A (HTR2A) gene polymorphisms (1438A/G, 102T/C, and rs7997012G/A) and the safety and efficacy of antidepressants in depression patients were constantly reported, but conclusions are debatable. This meta-analysis ascertained forty-two studies on the efficacy (including response and remission) and side-effect issued before February 2020. Pooled analyses indicated significant associations of 1438A/G polymorphism (16 studies, 1931 subjects) and higher response within dominant model (OR: 1.40, 95% CI: 1.12-1.76); rs7997012G/A polymorphism (nine studies, 1434 subjects) and higher remission in overall models (dominant model: OR: 1.30, 95% CI: 1.01-1.66; recessive model: OR: 2.20, 95% CI: 1.53-3.16; homozygote model: OR: 2.73, 95% CI: 1.78-4.17); 102T/C polymorphism (eight studies, 804 subjects) and reduced risk of side-effect within recessive (OR: 0.57, 95% CI: 0.4-0.83) and homozygote models (OR: 0.54, 95% CI: 0.29-0.99). For depression patients, genotyping of HTR2A polymorphisms is a promising tool for estimating the outcome and side-effect of antidepressants.

Association between genetic polymorphism and antidepressants in major depression: a network meta-analysis

This network meta-analysis was conducted to compare the predictive value of eight SNPs on the efficacy of antidepressants in major depressive disorder (MDD), including 5-HTTLPR, 5HTR2A (rs6311, rs6314, rs7997012 and rs6313), 5HTR2A (rs6295), BDNF (rs6265) and 5HTTSTin2. Databases were searched for related studies published up to December 2019. A total of 16 studies were included in this study. The predictive value were evaluated by the use of the odd ratios (OR) and drawing surface under the cumulative ranking curves (SUCRA). The pairwise meta-analysis indicated that in terms of overall response ratio, the SNPs were not associated with the efficacy of antidepressants in MDD. The result of this network meta-analysis suggested that there was no significant difference in predictive value of eight SNPs on the efficacy of antidepressants in MDD. More research is needed to explore the relationship between SNPs and antidepressant response.

Pharmacogenetic association of bi- and triallelic polymorphisms of SLC6A4 with antidepressant response in major depressive disorder

BACKGROUND

Antidepressants (ADs) are the main clinical therapy for depression, but approximately half of users do not get adequate response. The biallelic (5-HTTLPR) and triallelic (5-HTTLPR/rs25531) polymorphisms in SLC6A4 have been frequently investigated, but their associations with ADs response are in controversy. Here, we performed a meta-analysis to assess their modulation effect to ADs response in major depressive disorder (MDD).

METHODS

We performed literature search in PubMed, Web of Science and EMBASE before June 2019. Pooled analysis of genetic associations with response and remission, meta-regression and sensitivity analysis were performed, and publication bias was assessed.

RESULTS

Literature search yielded 49 eligible studies with 46 and 10 studies for biallelic and triallelic polymorphism, respectively. L allele of 5-HTTLPR was associated with both of response and remission rates. In the Caucasians using SSRIs only, carriers of LL/LS or LL genotype were more likely to be responders compared to SS carriers (LL/LS vs. SS: OR=1.55, 95%CI 1.20-2.00, p=0.001; LL vs. SS: OR=1.97, 95%CI 1.45-2.67, p<0.001). Similar associations were also found with remission rate. However, no effects on response or remission were found in the Asians or mixed/other antidepressant subgroups. Additionally, the 5-HTTLPR/rs25531 triallelic polymorphism may not associate with ADs response. Meta-regression showed that percent of female in participants, year of publication and treatment duration modulated the association in Caucasians.

CONCLUSION

5-HTTLPR, instead of 5-HTTLPR/rs25531 triallelic polymorphism, may exert as a marker for the prediction of response to SSRIs in Caucasians with MDD.

Analysis of the Deleterious Single-Nucleotide Polymorphisms Associated With Antidepressant Efficacy in Major Depressive Disorder

Major depressive disorder (MDD) is a serious mental disease with negative effects on both mental and physical health of the patient. Currently, antidepressants are among the major ways to ease or treat MDD. However, the existing antidepressants have limited efficacy in treating MDD, with a large fraction of patients either responding inadequately or differently to antidepressants during the treatment. Pharmacogenetics studies have found that the genetic features of some genes are associated with the antidepressant efficacy. In order to obtain a better understanding on the relationship between the genetic factors and antidepressant treatment response, we compiled a list of 233 single-nucleotide polymorphisms (SNPs) significantly associated with the antidepressant efficacy in treating MDD. Of the 13 non-synonymous SNPs in the list, three (rs1065852, rs3810651, and rs117986340) may influence the structures and function of the corresponding proteins. Besides, the influence of rs1065852 on the structure of CYP2D6 was further investigated via molecular dynamics simulations. Our results showed that compared to the native CYP2D6 the flexibility of the F-G loop was reduced in the mutant. As a portion of the substrate access channel, the lower flexibility of F-G loop may reduce the ability of the substrates to enter the channel, which may be the reason for the lower enzyme activity of mutant. This study may help us to understand the impact of genetic variation on antidepressant efficacy and provide clues for developing new antidepressants.

GRP Receptor Regulates Depression Behavior via Interaction With 5-HT2a Receptor

OBJECTIVE

Accumulating evidences indicate that gastrin-releasing peptide receptor (GRPR) may contribute to the pathophysiology of depression. However, the mechanism of the involvement of GRPR in the progression of depression remains unclear. Here, we showed the extent to which stress and antidepressant treatment impact GRPR expression, and explored the interactions between 5-HT2a receptor (5-HT2aR) and GRPR at the cellular level.

METHODS

The rat depression models were created with chronic unpredictable mild stress (CUMS). Then, these rats were treated with fluoxetine for 4 weeks after CUMS. We measured body weight and performed behavioral tests to determine the effects of stress and fluoxetine on depressive-like behaviors. Real-time PCR and western blotting were used to measure the mRNA and protein expression levels of GRPR in the hypothalamus. Then, Flag-tagged protein (pcmv-Flag-5HT2aR) and Myc-tagged protein (pcmv-Myc-GRPR) expression vectors were constructed, identified, and transfected into human embryo kidney 293 (HEK293) cells. The interaction between 5-HT2aR and GRPR was detected by coimmunoprecipitation and double-label immunofluorescence.

RESULTS

The rats subjected to 4 weeks of CUMS showed depressive-like behaviors, including decreased body weight, sucrose preference, and distance traveled, rearing frequency and velocity in the open field test and increased immobility time in the forced swimming test. Fluoxetine treatment reversed CUMS-induced depressive-like behavior. The mRNA and protein expression of GRPR in the hypothalamus was significantly increased after 4 weeks CUMS exposure, and treatment with fluoxetine reversed these changes. Coimmunoprecipitation showed that 5-HT2aR and GRPR combine with each other in vitro. Immunofluorescence revealed that the 5-HT2aR and GRPR were colocalization in both the cell membrane and cytoplasm.

CONCLUSION

Our study enhances the understanding of the involvement of GRPR in depression. This study also provides in vitro experimental evidence of the interaction between 5-HT2aR and GRPR, which may play an important role in the pathogenesis of depression.

Association of rs4680 COMT, rs6280 DRD3, and rs7322347 5HT2A With Clinical Features of Youth-Onset Schizophrenia

We investigated the associations of rs4680 COMT, rs6280 DRD3, and rs7322347 5HT2A with youth-onset schizophrenia in the Russian population in a case-control study, and the role of the genotype in the severity of clinical features. The association between rs7322347 and schizophrenia (p = 0.0001) is described for the first time. Furthermore, we found a link with rs6280 and rs4680 in females (p = 0.001 and p = 0.02 respectively) and with rs7322347 in males (p = 0.002). Clinical symptoms were assessed on three scales: the Clinician-Rated Dimensions of Psychosis Symptom Severity scale, Positive and Negative Syndrome Scale, and Frontal Assessment Battery. Gender differences in clinical features are of particular interest. In our study we found gender differences in the severity of clinical features-higher scores for delusions (Positive and Negative Syndrome Scale and Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) in males and higher scores for depression, delusions, somatic concern, motor retardation, poor attention were found in females.

User considerations in assessing pharmacogenomic tests and their clinical support tools

Pharmacogenomic (PGx) testing is gaining recognition from physicians, pharmacists and patients as a tool for evidence-based medication management. However, seemingly similar PGx testing panels (and PGx-based decision support tools) can diverge in their technological specifications, as well as the genetic factors that determine test specificity and sensitivity, and hence offer different values for users. Reluctance to embrace PGx testing is often the result of unfamiliarity with PGx technology, a lack of knowledge about the availability of curated guidelines/evidence for drug dosing recommendations, and an absence of wide-spread institutional implementation efforts and educational support. Demystifying an often confusing and variable PGx marketplace can lead to greater acceptance of PGx as a standard-of-care practice that improves drug outcomes and provides a lifetime value for patients. Here, we highlight the key underlying factors of a PGx test that should be considered, and discuss the current progress of PGx implementation.

Genetic variants in major depressive disorder: From pathophysiology to therapy

In spite of promising preclinical results there is a decreasing number of new registered medications in major depression. The main reason behind this fact is the lack of confirmation in clinical studies for the assumed, and in animals confirmed, therapeutic results. This suggests low predictive value of animal studies for central nervous system disorders. One solution for identifying new possible targets is the application of genetics and genomics, which may pinpoint new targets based on the effect of genetic variants in humans. The present review summarizes such research focusing on depression and its therapy. The inconsistency between most genetic studies in depression suggests, first of all, a significant role of environmental stress. Furthermore, effect of individual genes and polymorphisms is weak, therefore gene x gene interactions or complete biochemical pathways should be analyzed. Even genes encoding target proteins of currently used antidepressants remain non-significant in genome-wide case control investigations suggesting no main effect in depression, but rather an interaction with stress. The few significant genes in GWASs are related to neurogenesis, neuronal synapse, cell contact and DNA transcription and as being nonspecific for depression are difficult to harvest pharmacologically. Most candidate genes in replicable gene x environment interactions, on the other hand, are connected to the regulation of stress and the HPA axis and thus could serve as drug targets for depression subgroups characterized by stress-sensitivity and anxiety while other risk polymorphisms such as those related to prominent cognitive symptoms in depression may help to identify additional subgroups and their distinct treatment. Until these new targets find their way into therapy, the optimization of current medications can be approached by pharmacogenomics, where metabolizing enzyme polymorphisms remain prominent determinants of therapeutic success.

Value of Supportive Care Pharmacogenomics in Oncology Practice

Genomic medicine provides opportunities to personalize cancer therapy for an individual patient. Although novel targeted therapies prolong survival, most patients with cancer continue to suffer from burdensome symptoms including pain, depression, neuropathy, nausea and vomiting, and infections, which significantly impair quality of life. Suboptimal management of these symptoms can negatively affect response to cancer treatment and overall prognosis. The effect of genetic variation on drug response-otherwise known as pharmacogenomics-is well documented and directly influences an individual patient's response to antiemetics, opioids, neuromodulators, antidepressants, antifungals, and more. The growing body of pharmacogenomic data can now guide clinicians to select the safest and most effective supportive medications for an individual patient with cancer from the very first prescription. This review outlines a theoretical patient case and the implications of using pharmacogenetic test results to personalize supportive care throughout the cancer care continuum.

IMPLICATIONS FOR PRACTICE

Integration of palliative medicine into the cancer care continuum has resulted in increased quality of life and survival for patients with many cancer types. However, suboptimal management of symptoms such as pain, neuropathy, depression, and nausea and vomiting continues to place a heavy burden on patients with cancer. As demonstrated in this theoretical case, pharmacogenomics can have a major effect on clinical response to medications used to treat these conditions. Recognizing the value of supportive care pharmacogenomics in oncology and application into routine practice offers an objective choice for the safest and most effective treatment compared with the traditional trial and error method.

Serotonin transporter gene polymorphisms may be associated with poststroke neurological recovery after escitalopram use

OBJECTIVE

Selective serotonin reuptake inhibitors (SSRIs) putatively improve neurological recovery after stroke. We aimed to investigate whether serotonin transporter (SERT) gene polymorphisms are related to the responsiveness to SSRIs in the poststroke neurological recovery.

METHODS

This was a post hoc analysis of the EMOTION study (ClinicalTrials.gov NCT01278498), a randomised, placebo-controlled, double-blind trial examining the efficacy of escitalopram on emotional and neurological disturbances after acute stroke. Patients with no/minimal disability initially (modified Rankin Scale (mRS) 0-1) were excluded. Of the participants, 301 underwent genetic studies of the STin2 (a variable number tandem repeat (VNTR) in intron 2) (STin2 12/10 and STin2 12/12 genotypes) and 5-HTTLPR (a variable-length repeat in the promoter region) polymorphisms of SERT. We explored whether neurological function (National Institutes of Health Stroke Scale (NIHSS) score and mRS) at 3 months would differ according to SERT polymorphisms within each treatment arm (escitalopram and placebo).

RESULTS

Among the escitalopram users (n=159), neurological function in subjects with STin2 12/10 (n=29) improved significantly more than that in STin2 12/12 carriers (n=130) at 3 months. After adjusting for age, initial NIHSS and depression, STin2 12/10 independently predicted a good clinical outcome (mRS 0-1) (OR 2.99, 95% CI 1.04 to 8.58) at 3 months. However, differences between STin2 polymorphisms were not shown in the placebo group (n=142). 5-HTTLPR polymorphisms were not associated with neurological recovery in any treatment group.

CONCLUSION

STin2 VNTR polymorphisms may be associated with poststroke neurological recovery after SSRI therapy. Further studies are needed to identify the role of serotonin in neurological recovery after stroke.

Serotonin and brain function: a tale of two receptors

Previous attempts to identify a unified theory of brain serotonin function have largely failed to achieve consensus. In this present synthesis, we integrate previous perspectives with new and older data to create a novel bipartite model centred on the view that serotonin neurotransmission enhances two distinct adaptive responses to adversity, mediated in large part by its two most prevalent and researched brain receptors: the 5-HT1A and 5-HT2A receptors. We propose that passive coping (i.e. tolerating a source of stress) is mediated by postsynaptic 5-HT1AR signalling and characterised by stress moderation. Conversely, we argue that active coping (i.e. actively addressing a source of stress) is mediated by 5-HT2AR signalling and characterised by enhanced plasticity (defined as capacity for change). We propose that 5-HT1AR-mediated stress moderation may be the brain's default response to adversity but that an improved ability to change one's situation and/or relationship to it via 5-HT2AR-mediated plasticity may also be important - and increasingly so as the level of adversity reaches a critical point. We propose that the 5-HT1AR pathway is enhanced by conventional 5-HT reuptake blocking antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), whereas the 5-HT2AR pathway is enhanced by 5-HT2AR-agonist psychedelics. This bipartite model purports to explain how different drugs (SSRIs and psychedelics) that modulate the serotonergic system in different ways, can achieve complementary adaptive and potentially therapeutic outcomes.

Striatal N-Acetylaspartate Synthetase Shati/Nat8l Regulates Depression-Like Behaviors via mGluR3-Mediated Serotonergic Suppression in Mice

BACKGROUND

Several clinical studies have suggested that N-acetylaspartate and N-acetylaspartylglutamate levels in the human brain are associated with various psychiatric disorders, including major depressive disorder. We have previously identified Shati/Nat8l, an N-acetyltransferase, in the brain using an animal model of psychosis. Shati/Nat8l synthesizes N-acetylaspartate from L-aspartate and acetyl-coenzyme A. Further, N-acetylaspartate is converted into N-acetylaspartylglutamate, a neurotransmitter for metabotropic glutamate receptor 3.

METHODS

Because Shati/Nat8l mRNA levels were increased in the dorsal striatum of mice following the exposure to forced swimming stress, Shati/Nat8l was overexpressed in mice by the microinjection of adeno-associated virus vectors containing Shati/Nat8l gene into the dorsal striatum (dS-Shati/Nat8l mice). The dS-Shati/Nat8l mice were further assessed using behavioral and neurochemical tests.

RESULTS

The dS-Shati/Nat8l mice exhibited behavioral despair in the forced swimming and tail suspension tests and social withdrawal in the 3-chamber social interaction test. These depression-like behaviors were attenuated by the administration of a metabotropic glutamate receptor 2/3 antagonist and a selective serotonin reuptake inhibitor. Furthermore, the metabolism of N-acetylaspartate to N-acetylaspartylglutamate was decreased in the dorsal striatum of the dS-Shati/Nat8l mice. This finding corresponded with the increased expression of glutamate carboxypeptidase II, an enzyme that metabolizes N-acetylaspartylglutamate present in the extracellular space. Extracellular serotonin levels were lower in the dorsal striatum of the dS-Shati/Nat8l and normal mice that were repeatedly administered a selective glutamate carboxypeptidase II inhibitor.

CONCLUSIONS

Our findings indicate that the striatal expression of N-acetylaspartate synthetase Shati/Nat8l plays a role in major depressive disorder via the metabotropic glutamate receptor 3-mediated functional control of the serotonergic neuronal system.

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.

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.

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.

Serotonin pathway polymorphisms and the treatment of major depressive disorder and anxiety disorders

While antidepressants are widely used to treat major depressive disorder and anxiety disorders, only half of the patients will respond to antidepressant treatment and only a third of patients will experience a remission of symptoms. Identification of genetic biomarkers that predict antidepressant treatment response could thus greatly improve current clinical practice by providing guidance on which drug to use for which patient. Most antidepressant drugs for the treatment of depression and anxiety disorders have effects on the serotonergic neurotransmitter system; thus, genetic polymorphisms in the genes involved in this pathway represent logical candidates for investigation. This article reviews recent findings on the pharmacogenetics of antidepressant drugs with a focus on serotonergic pathway polymorphisms and discusses future clinical applications.

Genetic dysfunction of serotonin 2A receptor hampers response to antidepressant drugs: A translational approach

Pharmacological studies have yielded valuable insights into the role of the serotonin 2A (5-HT2A) receptor in major depressive disorder (MDD) and antidepressant drugs (ADs) response. However, it is still unknown whether genetic variants in the HTR2A gene affect the therapeutic outcome of ADs and the mechanism underlying the regulation of such response remains poorly described. In this context, a translational human-mouse study offers a unique opportunity to address the possibility that variations in the HTR2A gene may represent a relevant marker to predict the efficacy of ADs. In a first part of this study, we investigated in depressed patients the effect of three HTR2A single nucleotide polymorphisms (SNPs), selected for their potential functional consequences on 5-HT2A receptor (rs6313, rs6314 and rs7333412), on response and remission rates after 3 months of antidepressant treatments. We also explored the consequences of the constitutive genetic inactivation of the 5-HT2A receptor (i.e. in 5-HT2A(-/-) mice) on the activity of acute and prolonged administration of SSRIs. Our clinical data indicate that GG patients for the rs7333412 SNP were less prone to respond to ADs than AA/AG patients. In the preclinical study, we demonstrated that the 5-HT2A receptor exerts an inhibitory influence on the neuronal activity of the serotonergic system after acute administration of SSRIs. However, while the chronic administration of the SSRIs escitalopram or fluoxetine elicited a progressive increased in the firing rate of 5-HT neurons in 5-HT2A(+/+) mice, it failed to do so in 5-HT2A(-/-) mutants. These electrophysiological impairments were associated with a decreased ability of the chronic administration of fluoxetine to stimulate hippocampal plasticity and to produce antidepressant-like activities. Genetic loss of the 5-HT2A receptor compromised the activity of chronic treatment with SSRIs, making this receptor a putative marker to predict ADs response.

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.

Genetic Variations in the Serotonergic System Mediate a Combined, Weakened Response to SSRI Treatment: A Proposed Model

Individuals with the short (S) allele in the promoter region of the serotonin transporter gene (5-HTTLPR) show a less favorable response to selective serotonin reuptake inhibitor (SSRI) treatment than individuals with the long (L) allele. Similarly, individuals with the C(-1019)G allele for the mutation found in the promoter region of the serotonin 1A receptor gene (5-HTR1A) have shown blunted responses to SSRI treatment when compared with individuals lacking this polymorphism. While these findings have been replicated across multiple studies, only two studies to date have reported data for a gene-gene interaction associated with response to SSRI treatment. Both of these studies reported a combined effect for these genotypes, with individuals homozygous for the L allele and the C allele (5-HTT(L/L)-1A(C/C)) reporting the most favorable response to SSRI treatment, and individuals homozygous for the S allele and the G allele (5-HTT(S/S)-1A(G/G)) reporting the least favorable response to SSRI treatment. Additionally, no neural mechanisms have been proposed to explain why this gene-gene interaction has been observed. To that end, this article provides a review of the relevant literature associated with these polymorphisms and proposes a feasible model that describes a genotype-dependent modulation of postsynaptic serotonin signaling associated with the 5-HTT and 5-HTR1A genes.

Serotonin transporter gene: a new polymorphism may affect response to antidepressant treatments in major depressive disorder

BACKGROUND AND OBJECTIVES

Several gene variants have been related to major depressive disorder (MDD) treatment outcomes; however, few studies have investigated a possible different effect on pharmacotherapy and brief psychotherapy response.

METHODS

A total of 137 MDD patients were randomized to either interpersonal counseling (IPC; n = 40) or antidepressant pharmacological treatment (n = 97). Outcomes were remission, response, and symptom improvement at week 8. Five genetic variants were investigated (5HTR2A rs6314, BDNF rs6265, SLC6A4 rs8076005, CREB1 rs2253206, and TPH2 rs11179023) as possible modulators of outcomes.

RESULTS

The LC6A4 rs8076005 AA genotype and A allele were associated with response rate in the antidepressant group (p = 0.015 and 0.005, respectively) and in the whole sample (p = 0.03 and 0.02, respectively). In the IPC group a non-significant trend in the same direction was observed. The TPH2 rs11179023 A allele showed a marginal association with symptom improvement in the IPC group only. Other gene variants did not impact on outcomes in any treatment group.

CONCLUSION

Our study suggests that rs8076005 in the SLC6A4 gene may be a modulator of antidepressant response, especially when pharmacological treatment is used.

Central serotonin-2A (5-HT2A) receptor dysfunction in depression and epilepsy: the missing link?

5-Hydroxytryptamine 2A receptors (5-HT_2A-Rs) are G-protein coupled receptors. In agreement with their location in the brain, they have been implicated not only in various central physiological functions including memory, sleep, nociception, eating and reward behaviors, but also in many neuropsychiatric disorders. Interestingly, a bidirectional link between depression and epilepsy is suspected since patients with depression and especially suicide attempters have an increased seizure risk, while a significant percentage of epileptic patients suffer from depression. Such epidemiological data led us to hypothesize that both pathologies may share common anatomical and neurobiological alteration of the 5-HT_2A signaling. After a brief presentation of the pharmacological properties of the 5-HT_2A-Rs, this review illustrates how these receptors may directly or indirectly control neuronal excitability in most networks involved in depression and epilepsy through interactions with the monoaminergic, GABAergic and glutamatergic neurotransmissions. It also synthetizes the preclinical and clinical evidence demonstrating the role of these receptors in antidepressant and antiepileptic responses.

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.

Polymorphism in the serotonin receptor 2a (HTR2A) gene as possible predisposal factor for aggressive traits

Aggressive manifestations and their consequences are a major issue of mankind, highlighting the need for understanding the contributory factors. Still, aggression-related genetic analyses have so far mainly been conducted on small population subsets such as individuals suffering from a certain psychiatric disorder or a narrow-range age cohort, but no data on the general population is yet available. In the present study, our aim was to identify polymorphisms in genes affecting neurobiological processes that might explain some of the inter-individual variation between aggression levels in the non-clinical Caucasian adult population. 55 single nucleotide polymorphisms (SNP) were simultaneously determined in 887 subjects who also filled out the self-report Buss-Perry Aggression Questionnaire (BPAQ). Single marker association analyses between genotypes and aggression scores indicated a significant role of rs7322347 located in the HTR2A gene encoding serotonin receptor 2a following Bonferroni correction for multiple testing (p = 0.0007) both for males and females. Taking the four BPAQ subscales individually, scores for Hostility, Anger and Physical Aggression showed significant association with rs7322347 T allele in themselves, while no association was found with Verbal Aggression. Of the subscales, relationship with rs7322347 was strongest in the case of Hostility, where statistical significance virtually equaled that observed with the whole BPAQ. In conclusion, this is the first study to our knowledge analyzing SNPs in a wide variety of genes in terms of aggression in a large sample-size non-clinical adult population, also describing a novel candidate polymorphism as predisposal to aggressive traits.

Influence of 5-HTR2A genetic polymorphisms on the efficacy of antidepressants in the treatment of major depressive disorder: a meta-analysis

OBJECTIVE

The aim of the current meta-analysis was to assess the influence of common genetic polymorphisms in the 5-HTR2A gene on the efficacy of antidepressants in the treatment of major depressive disorder (MDD).

METHOD

MEDLINE (1966-2013), Cochrane Library Database (Issue 12, 2013), EMBASE (1980-2013), CINAHL (1982-2013), Web of Science (1945-2013) and Chinese Biomedical Database (CBM) (1982-2013) were searched without language restrictions. Meta-analysis was performed using the STATA statistical software. We calculated the odds ratio (OR) and its 95% confidence interval (95% CI) to estimate the efficacy of antidepressants in the treatment of MDD.

RESULTS

Eleven studies with a total of 1775 MDD patients met the inclusion criteria of this meta-analysis. Three common polymorphisms in the 5-HTR2A gene were assessed, including rs6311 C>T, rs7997012 G>A, and rs6313 T>C. Our findings suggested that the 5-HTR2A rs6313 T>C polymorphism was significantly correlated with a higher response rate to antidepressants in MDD patients (allele model: OR=1.33, 95% CI=1.05-1.68, P=0.020; dominant model: OR=1.62, 95% CI=1.21-2.18, P=0.001; homozygous model: OR=1.85, 95% CI=1.18-2.90, P=0.008). The rs7997012 G>A polymorphism was also associated with a higher response rate to antidepressants in MDD patients under the dominant model (OR=1.92, 95% CI=1.02-3.61, P=0.044). However, no significant correlation was found for the 5-HTR2A rs6311 C>T polymorphism under five genetic models (all P>0.05).

CONCLUSION

Our findings provide empirical evidence that the 5-HTR2A rs6313 T>C and rs7997012 G>A polymorphism may be correlated with the efficacy of antidepressants in the treatment of MDD.

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.

The influence of 5-HTTLPR genotype on the association between the plasma concentration and therapeutic effect of paroxetine in patients with major depressive disorder

INTRODUCTION

The efficacy of treatment with selective serotonin reuptake inhibitors in patients with major depressive disorder (MDD) can differ depending on the patient's serotonin transporter-linked polymorphic region (5-HTTLPR) genotype, and the effects of varying plasma concentrations of drugs can also vary. We investigated the association between the paroxetine plasma concentration and clinical response in patients with different 5-HTTLPR genotypes.

METHODS

Fifty-one patients were enrolled in this study. The Montgomery-Asberg Depression Rating Scale (MADRS) was used to evaluate patients at 0, 1, 2, 4, and 6 weeks. The patients' paroxetine plasma concentrations at week 6 were measured using high-performance liquid chromatography. Additionally, their 5-HTTLPR polymorphisms (alleles S and L) were analyzed using a polymerase chain reaction with specific primers. We divided the participants into two groups based on their L haplotype: the SS group and the SL and LL group. We performed single and multiple regression analyses to investigate the associations between MADRS improvement and paroxetine plasma concentrations or other covariates for each group.

RESULTS

There were no significant differences between the two groups with regard to demographic or clinical data. In the SS group, the paroxetine plasma concentration was significantly negatively correlated with improvement in MADRS at week 6. In the SL and LL group, the paroxetine plasma concentration was significantly positively correlated with improvement in MADRS at week 6 according to the results of the single regression analysis; however, it was not significantly correlated with improvement in MADRS at week 6 according to the results of the multiple regression analysis.

CONCLUSION

Among patients with MDD who do not respond to paroxetine, a lower plasma concentration or a lower oral dose of paroxetine might be more effective in those with the SS genotype, and a higher plasma concentration might be more effective in those with the SL or LL genotype.

Are there meaningful biomarkers of treatment response for depression?

During the past decades, the prevalence of affective disorders has been on the rise globally, with only one out of three patients achieving remission in acute treatment with antidepressants. The identification of physiological markers that predict treatment course proves useful in increasing therapeutic success. On the basis of well-documented, recent findings in depression research, we highlight and discuss the most promising biomarkers for antidepressant therapy response. These include genetic variants and gene expression profiles, proteomic and metabolomic markers, neuroendocrine function tests, electrophysiology and imaging techniques. Ultimately, this review proposes an integrative use of biomarkers for antidepressant treatment outcome.

From pharmacogenetics to pharmacogenomics: the way toward the personalization of antidepressant treatment

OBJECTIVE

Major depressive disorder is the most common psychiatric disorder, worldwide, yet response and remission rates are still unsatisfactory. The identification of genetic predictors of antidepressant (AD) response could provide a promising opportunity to improve current AD efficacy through the personalization of treatment. The major steps and findings along this path are reviewed together with their clinical implications and limitations.

METHOD

We systematically reviewed the literature through MEDLINE and Embase database searches, using any word combination of "antidepressant," "gene," "polymorphism," "pharmacogenetics," "genome-wide association study," "GWAS," "response," and "adverse drug reactions." Experimental works and reviews published until March 2012 were collected and compared.

RESULTS

Numerous genes pertaining to several functional systems were associated with AD response. The more robust findings were found for the following genes: solute carrier family 6 (neurotransmitter transporter), member 4; serotonin receptor 1A and 2A; brain-derived neurotrophic factor; and catechol-O-methyltransferase. Genome-wide association studies (GWASs) provided many top markers, even if none of them reached genome-wide significance.

CONCLUSIONS

AD pharmacogenetics have not produced any knowledge applicable to routine clinical practice yet, as results were mainly inconsistent across studies. Despite this, the rising awareness about methodological deficits of past studies could allow for the identication of more suitable strategies, such as the integration of the GWAS approach with the candidate gene approach, and innovative methodologies, such as pathway analysis and study of depressive endophenotypes.

A Preliminary Examination of the Relationship Between the 5-HTTLPR and Childhood Emotional Abuse on Depressive Symptoms in 10-12-Year-Old Youth

Childhood emotional abuse (CEA) is a pervasive problem associated with negative sequelae such as elevated depressive symptoms. Key stress-related genes, such as the 5-HTTLPR polymorphism, interact with childhood abuse to produce elevated depressive symptoms in older adolescent girls, but not in older adolescent boys. To date, studies have not examined this relationship as a function of CEA specifically or among younger adolescents. To extend prior work, we examined the effects of the 5-HTTLPR and CEA on depressive symptoms among 10-12-year-old youth. Based on previous findings, we expected a main effect of CEA on depressive symptoms among all youth, but only expected an interactive effect between the 5-HTTLPR and CEA on depressive symptoms in girls. In the current study, 222 youth (mean age 11.02 years, 44.1% girls, 51.6% Caucasian, 33.0% African American, 2.7% Latino, and 12.7% other) and their parent(s)/guardian(s) completed the Revised Child Anxiety and Depression Scale and the Emotional Abuse subscale of the Childhood Trauma Questionnaire and provided saliva samples for genotyping the 5-HTTLPR. Results indicate that CEA, but not the 5-HTTLPR, was related to elevated depressive symptoms among boys. Among girls, each copy of the s allele of the 5-HTTLPR was related to increased depressive symptoms, but only for those who had experienced CEA. Our results extend prior findings by specifically examining CEA and by focusing on 10-12-year-old youth. These results, although preliminary, suggest that focusing on the interplay between putative genetic markers and a broader range of environmental events, such as CEA, might allow researchers to determine factors differentially influencing the later emergence of sex differences in depressive symptoms.

Clinical validity of cytochrome P450 metabolism and serotonin gene variants in psychiatric pharmacotherapy

Adverse events, response failures and medication non-compliance are common in patients receiving medications for the treatment of mental illnesses. A systematic literature review assessed whether pharmacokinetic (PK) or pharmacodynamic (PD) responses to 26 commonly prescribed antipsychotic and antidepressant medications, including efficacy or side effects, are associated with nucleotide polymorphisms in eight commonly studied genes in psychiatric pharmacotherapy: CYP2D6, CYP2C19, CYP2C9, CYP1A2, CYP3A4, HTR2C, HTR2A, and SLC6A4. Of the 294 publications included in this review, 168 (57%) showed significant associations between gene variants and PK or PD outcomes. Other studies that showed no association often had insufficient control for confounding variables, such as co-medication use, or analysis of medications not substrates of the target gene. The strongest gene-outcome associations were for the PK profiles of CYP2C19 and CYP2D6 (93% and 90%, respectively), for the PD associations between HTR2C and weight gain (57%), and for SLC6A4 and clinical response (54%), with stronger SLC6A4 response associations for specific drug classes (60-83%). The preponderance of evidence supports the validity of analyzing nucleotide polymorphisms in CYP and pharmacodynamic genes to predict the metabolism, safety, or therapeutic efficacy of psychotropic medications commonly used for the treatment of depression, schizophrenia, and bipolar illness.

Pharmacogenetic polymorphisms and response to escitalopram and venlafaxine over 8 weeks in major depression

OBJECTIVE

The objective of this study is to investigate the influence of the 5-HTTLPR (serotonin transporter-linked promoter region), cytochrome P450 2C19, and cytochrome P450 2D6 polymorphisms on escitalopram (ESC) and venlafaxine (VEN) responses in major depressive disorder.

METHOD

A prospective multi-site study of 106 patients (Caucasian and Han Chinese ethnicities) with major depressive disorder treated with either ESC or VEN was conducted. The 17-item Hamilton Depression scale (HDRS), Clinical Global Impression Scale, and an adverse events scale (UKU) were assessed over 8 weeks, blind to genotype.

RESULTS

At the 8-week end point, a significant HDRS reduction for both ESC and VEN occurred (p < 0.0001). The 5-HTTLPR l/l genotype was associated with significantly greater score reductions on the HDRS compared with s/s carriers (p = 0.016) among Caucasian subjects receiving ESC (n = 47). Response rates were significantly higher for l/l (92%) compared with l/s (61%) and s/s (46%) variants (p = 0.042). For every l allele a participant carried, there was a 3.33 (95% confidence interval 1.25, 8.84; p = 0.02) times greater odds of ESC response. No significant associations between any of the genotypes and adverse effects were found.

CONCLUSION

Ethnicity may have differential effects on the 5-HTTLPR genotype-efficacy relationship. Results suggest that l/l allele for 5-HTTLPR is associated with a robust treatment response to ESC in Caucasian subjects only.

Pharmacogenetics of antidepressant drugs: an update after almost 20 years of research

Major depressive disorder (MDD) is an emergent cause of personal and socio-economic burden, both for the high prevalence of the disorder and the unsatisfying response rate of the available antidepressant treatments. No reliable predictor of treatment efficacy and tolerance in the single patient is available, thus drug choice is based on a trial and error principle with poor clinical efficiency. Among modulators of treatment outcome, genetic polymorphisms are thought to explain a significant share of the inter-individual variability. The present review collected the main pharmacogenetic findings primarily about antidepressant response and secondly about antidepressant induced side effects, and discussed the main strengths and limits of both candidate and genome-wide association studies and the most promising methodological opportunities and challenges of the field. Despite clinical applications of antidepressant pharmacogenetics are not available yet, previous findings suggest that genotyping may be applied in the clinical practice. In order to reach this objective, further rigorous pharmacogenetic studies (adequate sample size, study of better defined clinical subtypes of MDD, adequate covering of the genetic variability), their combination with the results obtained through complementary methodologies (e.g., pathway analysis, epigenetics, transcriptomics, and proteomics), and finally cost-effectiveness trials are required.

Pharmacogenetics in major depression: a comprehensive meta-analysis

A number of candidate gene studies focused on major depression (MD) and antidepressant (AD) efficacy have been carried out, but results mainly remain inconclusive. We performed a comprehensive meta-analysis of published candidate gene studies focused on AD efficacy in MD to evaluate the cumulative evidence. A random-effect model was applied to study the polymorphisms with genotypic counts available from at least three independent studies. On the base of previous evidence, the analysis was stratified by ethnicity (Caucasian, Asian, and other/mixed), and AD class (SSRIs and mixed/other ADs). Genotypic data were available for 16 polymorphisms in 11 genes. After the exclusion of 5-HTTLPR in SLC6A4 included in another recent meta-analysis, 15 polymorphisms in 11 genes were included in the present meta-analysis (BDNF rs6265, SLC6A4 STin2, HTR1A rs6295, HTR2A rs6311, rs6313 and rs7997012, HTR6 rs1805054, TPH1 rs1800532, SLC6A2 rs5569, COMT rs4680, GNB3 rs5443, FKBP5 rs1360780 and rs3800373, and ABCB1 rs1045642 and rs2032582). Our results suggested that BDNF rs6265 (Val66Met) heterozygous genotype was associated with better SSRIs response compared to the homozygous genotypes, particularly in Asians (OR=1.53, 95%CI 1.12-2.07, p=0.007). SLC6A4 STin2, HTR2A rs6311 and rs7997012, GNB3 rs5443, FKBP5 rs1360780 and rs3800373, and ABCB1 rs2032582 showed associations with AD efficacy, but these results were highly dependent on one or two single studies. In conclusion, our findings suggested the BDNF Val66Met as the best single candidate involved in AD response, with a selective effect on SSRI treatment. Our overall results supported no major effect of any single gene variant on AD efficacy.

Personalized medicine in psychiatry: problems and promises

The central theme of personalized medicine is the premise that an individual's unique physiologic characteristics play a significant role in both disease vulnerability and in response to specific therapies. The major goals of personalized medicine are therefore to predict an individual's susceptibility to developing an illness, achieve accurate diagnosis, and optimize the most efficient and favorable response to treatment. The goal of achieving personalized medicine in psychiatry is a laudable one, because its attainment should be associated with a marked reduction in morbidity and mortality. In this review, we summarize an illustrative selection of studies that are laying the foundation towards personalizing medicine in major depressive disorder, bipolar disorder, and schizophrenia. In addition, we present emerging applications that are likely to advance personalized medicine in psychiatry, with an emphasis on novel biomarkers and neuroimaging.

Association between serotonin transporter-linked polymorphic region and escitalopram antidepressant treatment response in Korean patients with major depressive disorder

OBJECTIVE

Various studies have shown that short (s)/long (l) polymorphisms of the serotonin transporter-linked polymorphic region (5-HTTLPR) might predict treatment outcome to selective serotonin reuptake inhibitors. The purpose of this study was to evaluate the association between 5-HTTLPR and clinical response to escitalopram treatment in Korean subjects with major depressive disorder.

METHODS

One hundred and fifteen Korean patients diagnosed with major depressive disorder were evaluated during 8 weeks of escitalopram treatment at a dose of 5-20 mg/day. Patients were genotyped for 5-HTTLPR using polymerase chain reaction. Clinical symptoms were evaluated by the 21-item Hamilton Depression Rating (HAMD-21) scale during the 8 weeks of treatment.

RESULTS

Therapeutic response to antidepressant escitalopram was better in s allele carriers (ss, sl) than in l allele homozygotes (ll) at 8 weeks of treatment (OR = 6.24, p = 0.026). The proportion of s allele carriers in responders was higher than that in non-responders (96.6 vs. 85.7%). The percentile decline in HAMD-21 in s allele carriers (59.86 ± 3.23%) was larger than that in HAMD-21 in l allele homozygotes (43.13 ± 11.49%; p = 0.029). However, 5-HTTLPR genotypes were not significantly associated with remission (p > 0.05).

CONCLUSIONS

Our results show that treatment response to escitalopram at 8 weeks was moderated by 5-HTTLPR, with better response rates for s allele carriers than for l allele homozygotes. Although the role of 5-HTTLPR as a definite predictor of selective serotonin reuptake inhibitor treatment response cannot be confirmed from current results, they do suggest a trend for better response in s allele carriers.

Escitalopram reduces attentional performance in anxious older adults with high-expression genetic variants at serotonin 2A and 1B receptors

Older adults are among the most vulnerable to adverse cognitive effects of psychotropic medications and, therefore, the personalization of psychotropic treatment based on adverse drug reactions in this demographic is of great importance. We examined changes on neuropsychological tests of attention attributable to selective serotonin reuptake inhibitor (SSRI) treatment in anxious older adults. We also examined whether variation in serotonin receptor genes was associated with reduced attentional performance with SSRIs. We examined change from pre- to post-treatment in two attention measures - digit span and coding - in 133 adults aged ≥60 yr with generalized anxiety disorder in a 12-wk trial of escitalopram vs. placebo. We also examined attentional change in relation to genetic variability in four central serotonin receptors: the serotonin transporter and serotonin 1A, 2A and 1B receptors. Digit span scores were significantly lowered in patients receiving escitalopram relative to placebo, indicating reduced attentional performance attributable to the SSRI. Individuals with high-transcription variants in the receptors 5-HTR2A rs6311 and 5-HTR1B rs11568817 had greater reductions in attention with SSRI treatment compared to placebo. We conclude that SSRIs reduce attention in older adults, particularly in those with high-expression genetic variants at the serotonin 2A and 1B receptors. Analysing neuropsychological changes with SSRIs in relation to genetic variation in the serotonin system may be a useful strategy for detecting subgroups of older adults who are more susceptible to side-effects of SSRIs. These results, if confirmed, could lead to the personalization of SSRI use to reduce adverse neurocognitive effects.