Genome-Wide Pharmacogenomic Study on Methadone Maintenance Treatment Identifies SNP rs17180299 and Multiple Haplotypes on CYP2B6, SPON1, and GSG1L Associated with Plasma Concentrations of Methadone R- and S-enantiomers in Heroin-Dependent Patients

Methadone maintenance treatment (MMT) is commonly used for controlling opioid dependence, preventing withdrawal symptoms, and improving the quality of life of heroin-dependent patients. A steady-state plasma concentration of methadone enantiomers, a measure of methadone metabolism, is an index of treatment response and efficacy of MMT. Although the methadone metabolism pathway has been partially revealed, no genome-wide pharmacogenomic study has been performed to identify genetic determinants and characterize genetic mechanisms for the plasma concentrations of methadone R- and S-enantiomers. This study was the first genome-wide pharmacogenomic study to identify genes associated with the plasma concentrations of methadone R- and S-enantiomers and their respective metabolites in a methadone maintenance cohort. After data quality control was ensured, a dataset of 344 heroin-dependent patients in the Han Chinese population of Taiwan who underwent MMT was analyzed. Genome-wide single-locus and haplotype-based association tests were performed to analyze four quantitative traits: the plasma concentrations of methadone R- and S-enantiomers and their respective metabolites. A significant single nucleotide polymorphism (SNP), rs17180299 (raw p = 2.24 × 10−8), was identified, accounting for 9.541% of the variation in the plasma concentration of the methadone R-enantiomer. In addition, 17 haplotypes were identified on SPON1, GSG1L, and CYP450 genes associated with the plasma concentration of methadone S-enantiomer. These haplotypes accounted for approximately one-fourth of the variation of the overall S-methadone plasma concentration. The association between the S-methadone plasma concentration and CYP2B6, SPON1, and GSG1L were replicated in another independent study. A gene expression experiment revealed that CYP2B6, SPON1, and GSG1L can be activated concomitantly through a constitutive androstane receptor (CAR) activation pathway. In conclusion, this study revealed new genes associated with the plasma concentration of methadone, providing insight into the genetic foundation of methadone metabolism. The results can be applied to predict treatment responses and methadone-related deaths for individualized MMTs.美沙酮维持治疗（Methadone Maintenance Treatment, MMT）常用于控制阿片类物质依赖、戒断症状，并提升海洛因依赖患者的生活质量。美沙酮对映体的稳态血浆浓度作为美沙酮代谢水平的衡量指标，是评估美沙酮维持治疗应答情况与疗效的重要指标。尽管美沙酮的代谢通路已得到部分阐明，但目前尚无全基因组药物基因组学研究，用于鉴定美沙酮R型与S型对映体血浆浓度的遗传决定因素并阐释其背后的遗传机制。本研究为首项在美沙酮维持治疗队列中开展的全基因组药物基因组学研究，旨在鉴定与美沙酮R型、S型对映体及其各自代谢产物的血浆浓度相关的基因。在完成数据质量控制后，本研究对中国台湾汉族人群中344名接受美沙酮维持治疗的海洛因依赖患者的数据集进行了分析。研究采用全基因组单基因座关联检验与基于单倍型的关联检验，对四项定量性状展开分析：美沙酮R型、S型对映体及其各自代谢产物的血浆浓度。研究鉴定出1个具有统计学意义的单核苷酸多态性（single nucleotide polymorphism, SNP）rs17180299（原始P值=2.24×10⁻⁸），该位点可解释美沙酮R型对映体血浆浓度变异的9.541%。此外，在SPON1、GSG1L与CYP450基因上，研究共鉴定出17个与美沙酮S型对映体血浆浓度相关的单倍型；这些单倍型约可解释整体S-美沙酮血浆浓度变异的四分之一。S-美沙酮血浆浓度与CYP2B6、SPON1及GSG1L的关联在另一项独立研究中得到了重复验证。基因表达实验显示，CYP2B6、SPON1及GSG1L可通过组成型雄甾烷受体（constitutive androstane receptor, CAR）激活通路实现协同激活。综上，本研究揭示了与美沙酮血浆浓度相关的新基因，为美沙酮代谢的遗传基础提供了新的研究视角；该研究结果可用于预测美沙酮维持治疗的应答情况及美沙酮相关死亡风险，从而实现个体化美沙酮维持治疗。