Pharmacogenetic study focused on fluoxetine pharmacodynamics in children and adolescent patients: impact of the serotonin pathway

Therapeutic Drug Monitoring in Children and Adolescents: Findings on Fluoxetine from the TDM-VIGIL Trial

Fluoxetine is the recommended first-line antidepressant in many therapeutic guidelines for children and adolescents. However, little is known about the relationships between drug dose and serum level as well as the therapeutic serum reference range in this age group. Within a large naturalistic observational prospective multicenter clinical trial ("TDM-VIGIL"), a transdiagnostic sample of children and adolescents (n = 138; mean age, 15; range, 7-18 years; 24.6% males) was treated with fluoxetine (10-40 mg/day). Analyses of both the last timepoint and all timepoints (n = 292 observations), utilizing (multiple) linear regressions, linear mixed-effect models, and cumulative link (mixed) models, were used to test the associations between dose, serum concentration, outcome, and potential predictors. The receiver operating curve and first to third interquartile methods, respectively, were used to examine concentration cutoff and reference values for responders. A strong positive relationship was found between dose and serum concentration of fluoxetine and its metabolite. Higher body weight was associated with lower serum concentrations, and female sex was associated with lower therapeutic response. The preliminary reference ranges for the active moiety (fluoxetine+norfluoxetine) were 208-328 ng/mL (transdiagnostically) and 201.5-306 ng/mL (depression). Most patients showed marked (45.6%) or minimal (43.5%) improvements and reported no adverse effects (64.9%). This study demonstrated a clear linear dose-serum level relationship for fluoxetine in youth, with the identified reference range being within that established for adults.

Genome-wide association study identifies TPH2 variant as a novel locus for severe CV-A6-associated hand, foot, and mouth disease in Han Chinese

BACKGROUND

Little is known about the association between genetic susceptibility and the severity of hand, foot, and mouth disease (HFMD) infected with coxsackievirus A6 (CV-A6).

METHODS

Three hundred and sixty-four CV-A6 HFMD patients were enrolled, including 115 severe and 249 mild patients. A genome-wide association study (GWAS) was performed involving eight DNA pools of 115 severe and 115 mild CV-A6 HFMD patients pair-matched by age and gender. Differences in relative allele signal scores of SNPs in Illumina Human OmniZhongHua-8 BeadChips were compared between the two groups. The tag SNPS for potentially functional SNPs or their high linked SNPs were selected for individual genotyping in all 364 patients and assessed for their associations with severe CV-A6 HFMD using multivariable logistic regression analyses.

RESULTS

The top 30 significant SNPs obtained from pooled DNA GWAS analysis were checked for biological functions and their high linkage disequilibrium (LD) SNPs. Four tag SNPs (rs1558206, rs6927647, rs9375728 and rs10879355) were selected for further individual genotyping in 364 CV-A6 patients. Only SNP rs10879355 was associated with severe CV-A6 HFMD, with CC genotype having a greater risk of severe illness than TT+TC genotypes (OR=2.48, 95%CI: 1.34, 4.56). SNP rs4290270 is in complete LD with rs10879355 in Chinese Han children.

CONCLUSIONS

This is the first report that one potentially functional SNP rs4290270 in the TPH2 gene may be associated with the risk of severe CV-A6 HFMD.

Antidepressant pharmacogenetics in children and young adults: A systematic review

OBJECTIVE

Antidepressants are frequently prescribed and are the first-line pharmacological treatments for psychiatric disorders in children and adolescents. Although antidepressants are generally effective and well-tolerated by children, between 31% to 48% will not respond and up to 25% will experience an adverse drug reaction. Evidence from adult populations suggests pharmacogenetic information can assist with identifying individuals at greatest risk for poor response or adverse drug reactions but the evidence base in pediatric populations is less clear.

METHOD

We systematically identified, reviewed, and critically evaluated the antidepressant pharmacogenetics literature among children and adolescents using standardized tools and consensus criteria.

RESULTS

We identified 24 studies, most of which were of fair to moderate quality. Collectively, the studies identified 25 significant gene-antidepressant associations involving 10 genes (ABCB1, BDNF, CYP2C19, CYP2D6, FKBP5, GNB3, HTR1B, HTR2A, SLC6A4, TPH2) and nine antidepressants (amitriptyline, citalopram, escitalopram, fluoxetine, fluvoxamine, nortriptyline, paroxetine, sertraline, and venlafaxine). None of the identified associations have been independently replicated in children.

LIMITATIONS

Included studies were heterogenous in terms of study design, genes and drugs assessed, and outcomes measured.

CONCLUSION

The antidepressant pharmacogenetics knowledge base in pediatric populations is still emerging, but results to date echo many of the gene-antidepressant associations identified in adult populations. Given ubiquitous prescribing of antidepressants in the care of children and adolescents with psychiatric disorders, further research on identifying new and confirming current gene-antidepressant associations are warranted.

Further Support for the Involvement of Genetic Variants Related to the Serotonergic Pathway in the Antidepressant Response in Children and Adolescents After a 12-Month Follow-Up: Impact of the HTR2A rs7997012 Polymorphism

Objective: Fluoxetine is an effective and well-tolerated pharmacological treatment for children and adolescents with major depressive disorder (MDD). However, a high percentage of patients do not respond. There is a substantial genetic contribution to this variable clinical outcome. Based on previous genetic results of our group and given the lack of pharmacogenetics studies of antidepressant response with a long follow-up period, we evaluated the influence of single nucleotide polymorphisms (SNPs) in genes related to the serotonergic pathway on remission and recovery in children and adolescents diagnosed with MDD after 12 months of initiating fluoxetine treatment. Methods: The assessment was performed in 46 patients. All of them were visited at least once a month during the 12-month follow-up. Psychiatrists interviewed patients and their parents to explore clinical improvement. A total of 75 genotyped SNPs in 10 candidate genes were included in the genetic association analysis with remission and recovery. Bonferroni correction for multiple testing was applied to avoid false positive results. Results: The HTR2A rs7997012 SNP was significantly associated after Bonferroni correction with clinical improvement. Particularly, the homozygotes for the major allele (GG) showed the highest percentage of remitters and the highest score reductions on the Clinical Global Impressions-Severity (CGI-S) scale. Moreover, although the results were on the border of statistical significance, the GG homozygotes also tended to experience fewer readmissions during the follow-up period Conclusions: These results provide more evidence of the involvement of genetic variants related to the serotonergic pathway in the antidepressant response. Studies with larger cohorts are needed to integrate all relevant variants into clinical predictors of antidepressant response.

HTR1A/1B DNA methylation may predict escitalopram treatment response in depressed Chinese Han patients

BACKGROUND

The serotonin receptor 1A and 1B (HTR1A/1B) gene have been suggested to be involved in the pathogenesis of major depressive disorder (MDD) and the antidepressant treatment response. Gene expression differences were partly mediated by genetic polymorphism and DNA methylation which might be affected by environmental factors. In the present study, we attempt to identify whether HTR1A/1B DNA methylation and genetic polymorphism could predict antidepressant treatment response.

METHODS

85 Chinese Han MDD patients were clinically assessed 8 weeks after of initiating escitalopram treatment for the first time. Antidepressant treatment response was assessed by changes in the Hamilton Depression Rating Scale-17 items (HAMD-17) score. The Life Events Scale (LES) and the Childhood Trauma Questionnaire (CTQ) were utilized as the assessment of previous life stress. The Illumina HiSeq platform was used to assess DNA methylation at 96 CpG sites located in HTR1A and HTR1B gene promoter regions. Six single nucleotide polymorphisms (SNPs) (HTR1A rs6294, rs116985176; HTR1B rs6296, rs6298, rs1228814, rs1778258) were genotype by using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) or PCR sequencing. Regression analyses were used to explore the relationship between DNA methylation and SNP and antidepressant response.

RESULTS

We identified two CpG sites predictor of antidepressant treatment response (CpG 668, amplicon HTR1A_1, NC_000005.10, P = 0.025; CpG 1401, amplicon HTR1B_4, NC_000006.12, P = 0.033). The interaction of four CpG sites hypomethylation of HTR1A/1B with high recent stress might result in impaired antidepressant treatment response. What's more, the present data indicated that age, environments and antidepressant treatment might affect DNA methylation status. It was found that DNA methylation status could be influenced by antidepressant treatment in turn. However, HTR1A and HTR1B genotypes did not influence antidepressant response and DNA methylation status.

CONCLUSIONS

The results suggest that HTR1A/1B DNA hypomethylation and its interaction with recent life stress might drive impaired antidepressant treatment response. Meanwhile, DNA methylation, in turn, was modified by antidepressant treatment and environments. Our results offer new evidence for the role of epigenetic and genetic polymorphism in pharmacological response to antidepressants.