Can COMT Val158Met Gene Polymorphism Predict Treatment Outcomes for Methylphenidates in ADHD Patients?

Abstract

The COMT gene encodes for the Catechol-O-methyltransferase (COMT) enzyme, an enzyme responsible for the breakdown of dopamine and norepinephrine in the prefrontal cortical areas. The most common variation of the COMT gene is the Val158Met polymorphism (rs4680) which leads to a valine (Val) to methionine (Met) substitution at codon 158. It is plausible that variations in this gene may predict treatment outcomes to stimulants like methylphenidates used in the treatment of ADHD. The purpose of this study is to statistically evaluate this association to further the clinical implementation of personalized medicine. Quantitative data was collected from clinical trials where patients were genotyped for the COMT gene and were evaluated for treatment response to methylphenidates on a quantifiable scale. Correlational analysis (n=1094) showed a statistically significant association (p=0.003) between this genotype and treatment outcomes. The Odd’s ratio calculated from the binary outcomes (n=638 patients) depicted that the Val/Val carriers were 1.86 times more likely to respond positively to methylphenidate treatment compared to the Met allele carriers. Our analysis shows that variations in COMT gene can reliably predict treatment outcomes to Methylphenidates in ADHD patients. However, this association is based on the data extracted from 9 different clinical studies (n= 1094 patients). These studies had different sample sizes, ethnicities, and measurement scales which may have contributed to the heterogeneity in the overall sample data set, thereby diluting the power of the association. Nevertheless, this analysis adds to the body of pharmacogenomic evidence increasing the clinical utility of precision medicine.