Clinical outcomes and genome-wide association for a brain methylation site in an antidepressant pharmacogenetics study in Mexican Americans

Objective: The authors compared the effectiveness of fluoxetine and desipramine treatment in a prospective double-blind pharmacogenetics study in first-generation Mexican Americans and examined the role of whole-exome functional gene variations in the patients' antidepressant response.

Method: A total of 232 Mexican Americans who met DSM-IV criteria for major depressive disorder were randomly assigned to receive 8 weeks of double-blind treatment with desipramine (50-200 mg/day) or fluoxetine (10-40 mg/day) after a 1-week placebo lead-in period. Outcomemeasures included the Hamilton Depression Rating Scale (HAM-D), the Hamilton Anxiety Rating Scale, and the Beck Depression Inventory. At week 8, whole-exome genotyping data were obtained for 36 participants who remitted and 29 who did not respond to treatment.

Results: Comparedwith desipramine treatment, fluoxetine treatment was associated with a greater reduction in HAM-D score, higher response and remission rates, shorter time to response and remission, and lower incidences of anticholinergic and cardiovascular side effects. Pharmacogenetics analysis showed that exm-rs1321744 achieved exome-wide significance for treatment remission. This variant is located in a brain methylated DNA immunoprecipitation sequencing site, which suggests that it may be involved in epigenetic regulation of neuronal gene expression. This and two other common gene variants provided a highly accurate cross-validated predictive model for treatment remission ofmajor depression (receiver operating characteristic integral=0.95).

Conclusions: Compared with desipramine, fluoxetine treatment showed amore rapid reduction of HAM-Dscore and a lower incidence of side effects in a population comprising primarily first-generation Mexican Americans with major depression. This study's pharmacogenetics approach strongly implicates the role of functional variants in antidepressant treatment response.