The importance of genetic factors (e.g. sequence variation) in the absorption, distribution, metabolism, excretion (ADME) and overall efficacy of therapeutic agents is well established. Our ability to identify, interpret and utilize these factors is the subject of much clinical investigation and therapeutic development. However, drug ADME and efficacy are also heavily influenced by epigenetic factors such as DNA/histone methylation and non-coding RNAs [especially microRNAs (miRNAs)]. Results from studies using tools, such as in silico miRNA target prediction, in vitro functional assays, nucleic acid profiling/sequencing and high-throughput proteomics, are rapidly expanding our knowledge of these factors and their effects on drug metabolism. Although these studies reveal a complex regulation of drug ADME, an increased understanding of the molecular interplay between the genome, epigenome and transcriptome has the potential to provide practically useful strategies to facilitate drug development, optimize therapeutic efficacy, circumvent adverse effects, yield novel diagnostics and ultimately become an integral component of personalized medicine.
LINKED ARTICLESThis article is part of a themed section on Epigenetics and Therapy. To view the other articles in this section visit http://dx.doi. org/10.1111/bph.2015.172.issue-11 Abbreviations ABC, ATP-binding cassette; ABCB1/MDR1/P-gp, multidrug resistance protein 1/P-glycoprotein; ADME, absorption, distribution, metabolism, excretion; antimiR, miRNA antagonist; CYP450, cytochrome P450; DOX, doxorubicin; ESR1, oestrogen receptor alpha; ETS1, V-Ets avian erythroblastosis virus E26 oncogene homologue 1; GPX7, glutathione peroxidase 7; GSS, glutathione synthetase; HDAC, histone deacetylase; LXRA, liver X receptor α; miRNA, microRNA; mRNA, messenger RNA; ncRNA, non-coding RNA; NR1C1, PPARα; PK, pharmacokinetic; PXR, pregnane X receptor; RISC, RNA-induced silencing complex; RXR, retinoid X receptor; SLC, solute carrier; UGT, UDP-glucuronosyltransferase; UTR, untranslated region; VD receptor, vitamin D receptor The proper control of absorption, distribution, metabolism and excretion (ADME) of xenobiotics is essential for living organisms to obtain energy, acquire necessary building blocks (e.g. essential amino acids) and maintain homeostasis in a complex chemical environment. Genes involved in ADME activities encode various receptor/transporters, biotransformation enzymes and accessory proteins (PharmaADME, http://pharmaadme.org/joomla/). These proteins include membrane transporters responsible for the absorption and excretion of specific molecules and enzymes to convert xenobiotics for excretion. To date, over 300 transporters and enzymes directly involved in ADME process have been described. This long list of components makes the study of ADME inherently complex, as transporters and enzymes work in concert to respond dynamically to diverse external factors. Despite the formidable complexity of the field, an understanding of ADME is critical for drug development in order...