Precision medicine and pharmacogenetics: what does oncology have that addiction medicine does not?

Individual variations in motives for nicotine self-administration in male rats: evidence in support for a precision psychopharmacology

The significant heterogeneity in smoking behavior among smokers, coupled with the inconsistent efficacy of approved smoking cessation therapies, supports the presence of individual variations in the mechanisms underlying smoking. This emphasizes the need to shift from standardized to personalized smoking cessation therapies. However, informed precision medicine demands precision fundamental research. Tobacco smoking is influenced and sustained by diverse psychopharmacological interactions between nicotine and environmental stimuli. In the classical experimental rodent model for studying tobacco dependence, namely intravenous self-administration of nicotine, seeking behavior is reinforced by the combined delivery of nicotine and a discrete cue (nicotine+cue). Whether self-administration behavior is driven by the same psychopharmacological mechanisms across individual rats remains unknown and unexplored. To address this, we employed behavioral pharmacology and unbiased cluster analysis to investigate individual differences in the mechanisms supporting classical intravenous nicotine self-administration (0.04 mg/kg/infusion) in male outbred Sprague-Dawley rats. Our analysis identified two clusters: one subset of rats sought nicotine primarily for its reinforcing effects, while the second subset sought nicotine to enhance the reinforcing effects of the discrete cue. Varenicline (1 mg/kg i.p.) reduced seeking behavior in the former group, whereas it tended to increase in the latter group. Crucially, despite this fundamental qualitative difference revealed by behavioral manipulation, the two clusters exhibited quantitatively identical nicotine+cue self-administration behavior. The traditional application of rodent models to study the reinforcing and addictive effects of nicotine may mask individual variability in the underlying motivational mechanisms. Accounting for this variability could significantly enhance the predictive validity of translational research.

Threats to external validity in the neuroprediction of substance use treatment outcomes

Background: Tools predicting individual relapse risk would invaluably inform clinical decision-making (e.g. level-of-care) in substance use treatment. Studies of neuroprediction - use of neuromarkers to predict individual outcomes - have the dual potential to create such tools and inform etiological models leading to new treatments. However, financial limitations, statistical power demands, and related factors encourage restrictive selection criteria, yielding samples that do not fully represent the target population. This problem may be further compounded by a lack of statistical optimism correction in neuroprediction research, resulting in predictive models that are overfit to already-restricted samples.Objectives: This systematic review aims to identify potential threats to external validity related to restrictive selection criteria and underutilization of optimism correction in the existing neuroprediction literature targeting substance use treatment outcomes.Methods: Sixty-seven studies of neuroprediction in substance use treatment were identified and details of sample selection criteria and statistical optimism correction were extracted.Results: Most publications were found to report restrictive selection criteria (e.g. excluding psychiatric (94% of publications) and substance use comorbidities (69% of publications)) that would rule-out a considerable portion of the treatment population. Furthermore, only 21% of publications reported optimism correction.Conclusion: Restrictive selection criteria and underutilization of optimism correction are common in the existing literature and may limit the generalizability of identified neural predictors to the target population whose treatment they would ultimately inform. Greater attention to the inclusivity and generalizability of addiction neuroprediction research, as well as new opportunities provided through open science initiatives, have the potential to address this issue.

RNA biomarkers for alcohol use disorder

Alcohol use disorder (AUD) is highly prevalent and one of the leading causes of disability in the US and around the world. There are some molecular biomarkers of heavy alcohol use and liver damage which can suggest AUD, but these are lacking in sensitivity and specificity. AUD treatment involves psychosocial interventions and medications for managing alcohol withdrawal, assisting in abstinence and reduced drinking (naltrexone, acamprosate, disulfiram, and some off-label medications), and treating comorbid psychiatric conditions (e.g., depression and anxiety). It has been suggested that various patient groups within the heterogeneous AUD population would respond more favorably to specific treatment approaches. For example, there is some evidence that so-called reward-drinkers respond better to naltrexone than acamprosate. However, there are currently no objective molecular markers to separate patients into optimal treatment groups or any markers of treatment response. Objective molecular biomarkers could aid in AUD diagnosis and patient stratification, which could personalize treatment and improve outcomes through more targeted interventions. Biomarkers of treatment response could also improve AUD management and treatment development. Systems biology considers complex diseases and emergent behaviors as the outcome of interactions and crosstalk between biomolecular networks. A systems approach that uses transcriptomic (or other -omic data, e.g., methylome, proteome, metabolome) can capture genetic and environmental factors associated with AUD and potentially provide sensitive, specific, and objective biomarkers to guide patient stratification, prognosis of treatment response or relapse, and predict optimal treatments. This Review describes and highlights state-of-the-art research on employing transcriptomic data and artificial intelligence (AI) methods to serve as molecular biomarkers with the goal of improving the clinical management of AUD. Considerations about future directions are also discussed.

Pharmacogenetics of Addiction Therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies with response to treatment based on individual genetic makeup. In this chapter, we will discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The continued elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

Pharmacogenomics: A road ahead for precision medicine in psychiatry

Psychiatric genomics is providing insights into the nature of psychiatric conditions that in time should identify new drug targets and improve patient care. Less attention has been paid to psychiatric pharmacogenomics research, despite its potential to deliver more rapid change in clinical practice and patient outcomes. The pharmacogenomics of treatment response encapsulates both pharmacokinetic ("what the body does to a drug") and pharmacodynamic ("what the drug does to the body") effects. Despite early optimism and substantial research in both these areas, they have to date made little impact on clinical management in psychiatry. A number of bottlenecks have hampered progress, including a lack of large-scale replication studies, inconsistencies in defining valid treatment outcomes across experiments, a failure to routinely incorporate adverse drug reactions and serum metabolite monitoring in study designs, and inadequate investment in the longitudinal data collections required to demonstrate clinical utility. Nonetheless, advances in genomics and health informatics present distinct opportunities for psychiatric pharmacogenomics to enter a new and productive phase of research discovery and translation.

Tumor Chemosensitivity Assays Are Helpful for Personalized Cytotoxic Treatments in Cancer Patients

Tumor chemosensitivity assays (TCAs), also known as drug response assays or individualized tumor response tests, have been gaining attention over the past few decades. Although there have been strong positive correlations between the results of these assays and clinical outcomes, they are still not considered routine tests in the care of cancer patients. The correlations between the assays' results (drug sensitivity or resistance) and the clinical evaluations (e.g., response to treatment, progression-free survival) are highly promising. However, there is still a need to design randomized controlled prospective studies to secure the place of these assays in routine use. One of the best ideas to increase the value of these assays could be the combination of the assay results with the omics technologies (e.g., pharmacogenetics that gives an idea of the possible side effects of the drugs). In the near future, the importance of personalized chemotherapy is expected to dictate the use of these omics technologies. The omics relies on the macromolecules (Deoxyribonucleic acid -DNA-, ribonucleic acid -RNA-) and proteins (meaning the structure) while TCAs operate on living cell populations (meaning the function). Therefore, wise combinations of TCAs and omics could be a highly promising novel landscape in the modern care of cancer patients.

Topic Evolution Analysis for Omics Data Integration in Cancers

One of the vital challenges for cancer diseases is efficient biomarkers monitoring formation and development are limited. Omics data integration plays a crucial role in the mining of biomarkers in the human condition. As the link between omics study on biomarkers discovery and cancer diseases is deepened, defining the principal technologies applied in the field is a must not only for the current period but also for the future. We utilize topic modeling to extract topics (or themes) as a probabilistic distribution of latent topics from the dataset. To predict the future trend of related cases, we utilize the Prophet neural network to perform a prediction correction model for existing topics. A total of 2,318 pieces of literature (from 2006 to 2020) were retrieved from MEDLINE with the query on “omics” and “cancer.” Our study found 20 topics covering current research types. The topic extraction results indicate that, with the rapid development of omics data integration research, multi-omics analysis (Topic 11) and genomics of colorectal cancer (Topic 10) have more studies reported last 15 years. From the topic prediction view, research findings in multi-omics data processing and novel biomarker discovery for cancer prediction (Topic 2, 3, 10, 11) will be heavily focused in the future. From the topic visuallization and evolution trends, metabolomics of breast cancer (Topic 9), pharmacogenomics (Topic 15), genome-guided therapy regimens (Topic 16), and microRNAs target genes (Topic 17) could have more rapidly developed in the study of cancer treatment effect and recurrence prediction.

The future of translational research on alcohol use disorder

In March 2019, a scientific meeting was held at the University of California, Los Angeles (UCLA) Luskin Center to discuss approaches to expedite the translation of neurobiological insights to advances in the treatment of alcohol use disorder (AUD). A guiding theme that emerged was that while translational research in AUD is clearly a challenge, it is also a field ripe with opportunities. Herein, we seek to summarize and disseminate the recommendations for the future of translational AUD research using four sections. First, we briefly review the current landscape of AUD treatment including the available evidence-based treatments and their uptake in clinical settings. Second, we discuss AUD treatment development efforts from a translational science viewpoint. We review current hurdles to treatment development as well as opportunities for mechanism-informed treatment. Third, we consider models of translational science and public health impact. Together, these critical insights serve as the bases for a series of recommendations and future directions. Towards the goal of improving clinical care and population health for AUD, scientists are tasked with bolstering the clinical applicability of their research findings so as to expedite the translation of knowledge into patient care.

Pharmacogenomics and prescription opioid use

Genome-wide association studies and candidate gene findings suggest that genetic approaches may help in choosing the most appropriate drug and dosage, while preventing adverse drug reactions. This is the field that addresses precision medicine: to evaluate variations in the DNA sequence that could be responsible for different individual analgesic response. We review potential gene biomarkers with best overall convergent functional evidence, for opioid use, in pain management. Polymorphisms can modify pharmacodynamics (i.e., mu opioid receptor, OPRM1) and pharmacokinetics (i.e., CYP2D6 phenotypes) pathways altering opioid effectiveness, consumption, side effects or additionally, prescription opioid use dependence vulnerability. This review provides a summary of these candidate variants for the translation of genotype into clinically useful information in pain medicine.

Genomics and Transcriptomics: The Powerful Technologies in Precision Medicine

In a clinical trial, people with the same disease can show different responses after treatment with the same drug and exactly under the same conditions. Some of them may improve, some may not show any response, and occasionally side effects may be observed. In other words, people with the same disease process under the same therapeutic conditions may have different responses. Today, some diseases are resistant to conventional (standard) treatment procedures. Why do people with the same disease show different responses to the treatment with the same drug? This is primarily due to differences in molecular pathways (especially genetic variations) associated with the disease. On the other hand, designing and delivery of a new drug is a time-consuming and costly process, so any mistake in any stage of this process can have irreparable consequences for pharmaceutical companies and consumer patients. Therefore, we can achieve more accurate and reliable treatments by acquiring precise insight into different aspects of precision medicine including genomics and transcriptomics. The aim of this paper is to address the role of genomics and transcriptomics in precision medicine.

Systematic review and meta-analysis of the moderating effect of rs1799971 in OPRM1, the mu-opioid receptor gene, on response to naltrexone treatment of alcohol use disorder

BACKGROUND AND AIMS

There is wide inter-individual variability in response to the treatment of alcohol use disorder (AUD) with the opioid receptor antagonist naltrexone. To identify patients who may be most responsive to naltrexone treatment, studies have examined the moderating effect of rs1799971, a single nucleotide polymorphism (SNP) that encodes a non-synonymous substitution (Asn40Asp) in the mu-opioid receptor gene, OPRM1. The aims of this study were to: (1) conduct a systematic review of randomized clinical trials (RCTs); (2) assess the bias of the available studies and gauge publication bias; and (3) meta-analyze the interaction effect of the Asn40Asp SNP on the response to naltrexone treatment.

METHODS

We searched for placebo-controlled RCTs that examined the effect of Asn40Asp on the response to naltrexone treatment of heavy drinking or AUD. We tested the hypothesis that the minor (Asp40) allele was associated with a greater reduction in five alcohol consumption measures (relapse to heavy drinking, abstinence, percentage of heavy drinking days, percentage of days abstinent and drinks per day) in naltrexone-treated participants by meta-analyzing the interaction effects using a random effects model.

RESULTS

Seven RCTs met the study criteria. Overall, risk of bias was low and we observed no evidence of publication bias. Of the five alcohol consumption outcomes considered, there was a nominally significant moderating effect of the Asn40Asp SNP only on drinks per day (d = -0.18, P = 0.02). However, the effect was not significant when multiple comparisons were taken into account.

CONCLUSIONS

From the evidence to date, it remains unclear whether rs1799971, the OPRM1 Asn40Asp single nucleotide polymorphism, predicts naltrexone treatment response in individuals with alcohol use disorder or heavy drinking.

Survey of Addiction Specialists' Use of Medications to Treat Alcohol Use Disorder

OBJECTIVES

Several medications have been shown to be safe and effective for treating alcohol use disorder (AUD); however, these medications are prescribed infrequently. We conducted a survey of the demographics, practice characteristics, and self-perceived knowledge, experience, and opinions of addiction specialists on the use of AUD medications and how to increase their use.

METHODS

We sent a 19-question survey to members of the American Society of Addiction Medicine (ASAM) and the American Academy of Addiction Psychiatry (AAAP).

RESULTS

We received a total of 395 responses from ASAM members and 194 responses from AAAP members. One hundred of the respondents were members of both organizations. The large majority of respondents (92.6%) were prescribers, and 81.6% were non-trainee physicians. The two most frequently used medications for treating AUD were oral naltrexone (27%) and long-acting naltrexone (18%). Respondents were significantly more confident in the strength of the research findings and evidence for the efficacy and safety of naltrexone than other AUD medications (p < 0.001 ). Respondents identified additional education to current providers about existing medications as the most important potential intervention to increase the use of AUD medications.

CONCLUSIONS

Compared with a survey published in 2001, in 2018 the proportion of respondents who reported using naltrexone more than doubled and addiction specialists were more confident in their use of AUD medications, rating their efficacy and safety more highly. Consistent with findings from other recent studies, providing more education to practitioners about existing AUD medications may be the most effective way to increase their use.

In Search of Reward Deficiency Syndrome (RDS)-free Controls: The "Holy Grail" in Genetic Addiction Risk Testing

BACKGROUND

The search for an accurate, gene-based test to identify heritable risk factors for Reward Deficiency Syndrome (RDS) was conducted based on hundreds of published studies about the role of dopamine in addictive behaviors, including risk for drug dependence and compulsive/impulsive behavior disorders. The term RDS was first coined by Blum's group in 1995 to identify a group of behaviors with a common neurobiological mechanism associated with a polymorphic allelic propensity for hypodopaminergia.

OBJECTIVES

To outline the process used to select risk alleles of reward genes for the Genetic Addiction Risk Score (GARS) test. Consequently, to address the limitations caused by inconsistent results that occur in many case-control behavioral association studies. These limitations are perhaps due to the failure of investigators to adequately screen controls for drug and alcohol use disorder, and any of the many RDS behaviors, including nicotine dependence, obesity, pathological gambling, and internet gaming addiction.

METHODS

Review of the literature related to the function of risk alleles of reward genes associated with hypodopaminergia relevant case-control association studies for the selection of alleles to be measured by the Genetic Addiction Risk Score (GARS) test.

RESULTS

The prevalence of the DRD2 A1 allele in unscreened controls (33.3%), compared to "Super-Controls" [highly screened RDS controls (3.3%) in proband and family] is used to exemplify a possible solution.

CONCLUSION

Unlike one gene-one disease (OGOD), RDS is polygenetic, and very complex. In addition, any RDS-related behaviors must be eliminated from the control group in order to obtain the best possible statistical analysis instead of comparing the phenotype with disease-ridden controls.

Pharmacogenetics in the clinical analysis laboratory: clinical practice, research, and drug development pipeline

Introduction: Over the last decade, the spread of next-generation sequencing technology along with the rising cost in health management in national health systems has led to widespread use/abuse of pharmacogenetic tests (PGx) in the practice of many clinical disciplines. However, given their clinical significance, it is important to standardize these tests for having an interaction with the clinical analysis laboratory (CAL), in which a PGx service can meet these requirements. Areas covered: A diagnostic test must meet the criteria of reproducibility and validity for its utility in the clinical routine. This present review mainly describes the utility of introducing PGx tests in the CAL routine to produce correct results useful for setting up personalized drug treatments. Expert opinion: With a PGx service, CALs can provide the right tool to help clinicians to make better choices about different categories of drugs and their dosage and to manage the economic impact both in hospital-based settings and in National Health Services, throughout electronic health records. Advances in PGx also allow a new approach for pharmaceutical companies in order to improve drug development and clinical trials. As a result, CALs can achieve a powerful source of epidemiological, clinical, and research findings from PGx tests.

Pharmacogenetics of alcohol use disorder treatments: an update

Introduction: Alcohol use disorder (AUD) is highly prevalent; costly economically, socially, and interpersonally; and grossly undertreated. The low rate of utilization of medications with demonstrated (albeit modest) efficacy is particularly noteworthy. One approach to increasing the utility and safety of available medications is to use a precision medicine approach, which seeks to identify patients for whom specific medications are likely to be most efficacious and have the fewest adverse effects. Areas Covered: We review the literature on the pharmacogenetics of AUD treatment using both approved and off-label medications. We cover both laboratory studies and clinical trials, highlighting valuable mechanistic insights and underscoring the potential value of precision-based care for AUD. Expert Opinion: Pharmacotherapy can be a useful component of AUD treatment. Currently, the evidence regarding genetic predictors of medication efficacy is very limited. Thus, a precision medicine approach is not yet ready for widespread clinical implementation. Further research is needed to identify candidate genetic variants that moderate the response to both established and novel medications. The growing availability of large-scale, longitudinal datasets that enable the synthesis of genetic and electronic health record data provides important opportunities to develop this area of research.

Salivary microRNAs identified by small RNA sequencing and machine learning as potential biomarkers of alcohol dependence

Aim: Salivary miRNA can be easily accessible biomarkers of alcohol dependence (AD). Materials & methods: The miRNA transcriptome in the saliva of 56 African-Americans (AAs; 28 AD patients/28 controls) and 64 European-Americans (EAs; 32 AD patients/32 controls) was profiled using small RNA sequencing. Differentially expressed miRNAs were identified. Salivary miRNAs were used to predict the AD presence using machine learning with Random Forests. Results: Seven miRNAs were differentially expressed in AA AD patients, and five miRNAs were differentially expressed in EA AD patients. The AD prediction accuracy based on top five miRNAs (ranked by Gini index) was 79.1 and 72.2% in AAs and EAs, respectively. Conclusion: This study provided the first evidence that salivary miRNAs are AD biomarkers.

Conceptualizing Addiction From an Osteopathic Perspective: Dopamine Homeostasis

Addiction is a public health crisis in the United States. Understanding the cause and providing effective treatment for patients-in particular, those with substance use disorders-is challenging. Research has demonstrated that addiction is not a flaw in one's moral fiber or a disease of choice; rather, it is driven by alterations in neuronal mechanisms, especially those that involve the neurotransmitter dopamine, which plays a critical role in the brain's reward pathway. Much of osteopathic philosophy is based on the concept of total body homeostasis and allostasis. This article discusses the role of achieving dopamine homeostasis as part of a comprehensive biopsychosocial treatment strategy in the effective management of addiction. The authors aim to motivate osteopathic primary care physicians to incorporate osteopathic philosophy into the treatment of patients with substance use disorders.

State-of-the-art behavioral and pharmacological treatments for alcohol use disorder

BACKGROUND

Alcohol use disorder (AUD) and its associated consequences remain significant public health concerns. Given that AUD represents a spectrum of severity, treatment options represent a continuum of care, ranging from single-session brief interventions to more intensive, prolonged, and specialized treatment modalities.

OBJECTIVE

This qualitative literature review seeks to describe the best practices for AUD by placing a particular emphasis on identifying those practices which have received the most empirical support.

METHOD

This review summarizes psychological and pharmacological intervention options for AUD treatment, with a focus on the relapse prevention phase of recovery. Psychological and pharmacological treatments are summarized in terms of the empirical evidence favoring each approach and the level of AUD severity for which they are most indicated.

SCIENTIFIC SIGNIFICANCE

One of the broad assertions from this review is that while AUD is highly prevalent, seeking treatment for AUD is not. There are a myriad of behavioral and pharmacological treatments that have shown compelling evidence of efficacy for the treatment of AUD. In the behavioral treatment literature, cognitive behavioral therapy has received the most consistent support. Opioid antagonism (via naltrexone) has been the most widely studied pharmacotherapy and has produced moderate effect sizes. While none of the treatments reviewed herein represents a so-called silver bullet for AUD, they each have the potential to significantly improve the odds of recovery. Precision medicine, or the identification of best treatment matches for individual patients, looms as an important overarching goal for the field, although specific matches are not yet sufficiently reliable in their empirical evidence to warrant clinical dissemination.

Does cardiology hold pharmacogenetics to an inconsistent standard? A comparison of evidence among recommendations

Current guideline recommendations for pharmacogenetic testing for clopidogrel by the American Heart Association/American College of Cardiology (AHA/ACC) contradict the Clinical Pharmacogenetics Implementation Consortium and the US FDA. The AHA/ACC recommends against routine pharmacogenetic testing for clopidogrel because no randomized controlled trials have demonstrated that testing improves patients' outcomes. However the AHA/ACC and the National Comprehensive Cancer Network (NCCN) recommend other pharmacogenetic tests in the absence of randomized controlled trials evidence. Using clopidogrel as a case example, we compared the evidence for other pharmacogenetic tests recommended by the AHA/ACC and NCCN. In patients that received percutaneous coronary intervention, the evidence supporting pharmacogenetic testing for clopidogrel is stronger than other pharmacogenetic tests recommended by the AHA/ACC and NCCN.

Precision Psychiatry and Dual Disorders

OBJECTIVE

Addiction co-occurs with distinct pathological personality traits, other psychiatric disorders or symptoms and cognitive impairment, which are known as dual disorders or co-occurring disorders. This symptomatic high concurrency suggests that both conditions are in some ways causally linked. Research is ongoing to identify distinctive neurobehavioral mechanisms and endophenotypes that predispose individuals to compulsive drug use and other mental disorders. Research is also providing new revelations about the diverse effects of substances on individuals, including differences according to sex. Today we know that the same substance may give rise to different behavioral, affective, cognitive, and sensory effects across different individuals.

METHODS

This state-of the art review tends to address the concept of precision psychiatry and dual disorders. The PubMed database was searched for the last 15 years to identify those articles that reported neurobiological perspectives on dual disorders, addiction and other mental disorders, precision medicine, and precision psychiatry.

RESULTS

There has been considerable progress made in recent years in relation to the study of addiction and dual disorders. The concept of dual disorders attempts to capture not only the persistence of substance use and substance seeking but also the evident vulnerability of specific subpopulations to switch from controlled to compulsive drug use. Precision medicine is focused on identifying this individual vulnerability to illness as much as the individual response to treatment. Psychiatry is fully committed to this goal. Regarding addiction, essential precision medicine advances will be possible if concerted efforts are made in the discovery of biological variations and environmental factors that contribute to individual vulnerability to addictive disorders and dual disorders, together with the identification of moderators of treatment response.

CONCLUSIONS

Here we survey the discoveries, future research directions, and translational relevance of the concept of precision psychiatry for dual disorders. The review may offer new perspectives on this issue and highlight a new way to see and to think about dual disorders.

New steps for treating alcohol use disorder

Alcohol use disorder is a complex syndrome with multiple treatment points including drug-induced pathology, withdrawal management, behavioral/cognitive strategies, and relapse prevention. These different components may be complicated by genotype and phenotype. A huge milestone for the treatment of alcohol use disorder across several countries in the last 10 years was the introduction of practice guidelines integrating clinical expertise and research evidence. These provide a summary of interventions that have been shown to be effective following rigorous and replicated clinical trials. Inspection of these guidelines reveals good consistency, but little evidence of progress in treatment approaches for alcohol use disorder over the past decade. In this mini-review, we discuss emerging treatments for alcohol use disorder that may supplement or improve the evidence-based treatments that are currently recommended. New medications, the emergence of digital technology, and other novel approaches such as transcranial magnetic stimulation are all discussed with reference to treatments already in practice. We also consider how individual differences in genotype and phenotype may affect outcomes. Together with improvements in technology, this knowledge offers a powerful tool for designing personalized approaches to treatment, and hence improving prognosis for rehabilitation programs.

Biosignature Discovery for Substance Use Disorders Using Statistical Learning

There are limited biomarkers for substance use disorders (SUDs). Traditional statistical approaches are identifying simple biomarkers in large samples, but clinical use cases are still being established. High-throughput clinical, imaging, and 'omic' technologies are generating data from SUD studies and may lead to more sophisticated and clinically useful models. However, analytic strategies suited for high-dimensional data are not regularly used. We review strategies for identifying biomarkers and biosignatures from high-dimensional data types. Focusing on penalized regression and Bayesian approaches, we address how to leverage evidence from existing studies and knowledge bases, using nicotine metabolism as an example. We posit that big data and machine learning approaches will considerably advance SUD biomarker discovery. However, translation to clinical practice, will require integrated scientific efforts.

Clinical application of pharmacogenetics in pain management

There is growing experience translating genomic data into clinical practice, as seen with the Implementing GeNomics In pracTicE (IGNITE) network. A primary example is the influence of CYP2D6 genotype on the beneficial and adverse effects of some opioids. Clinical recommendations exist to guide drug therapy based on CYP2D6 genotype for codeine, tramadol, oxycodone and hydrocodone, although the level of supporting evidence differs by drug. Limited evidence also supports the use of genetic data to guide other medications in chronic pain therapy, including tricyclic antidepressants and celecoxib. Pragmatic clinical trial data are needed in this area to better understand the impact of diverse populations, therapeutic interventions and clinical care environments on genotype-guided drug therapy for chronic pain.

Chronic Alcohol, Intrinsic Excitability, and Potassium Channels: Neuroadaptations and Drinking Behavior

Neural mechanisms underlying alcohol use disorder remain elusive, and this lack of understanding has slowed the development of efficacious treatment strategies for reducing relapse rates and prolonging abstinence. While synaptic adaptations produced by chronic alcohol exposure have been extensively characterized in a variety of brain regions, changes in intrinsic excitability of critical projection neurons are understudied. Accumulating evidence suggests that prolonged alcohol drinking and alcohol dependence produce plasticity of intrinsic excitability as measured by changes in evoked action potential firing and after-hyperpolarization amplitude. In this chapter, we describe functional changes in cell firing of projection neurons after long-term alcohol exposure that occur across species and in multiple brain regions. Adaptations in calcium-activated (K_Ca2), voltage-dependent (K_V7), and G protein-coupled inwardly rectifying (K_ir3 or GIRK) potassium channels that regulate the evoked firing and after-hyperpolarization parallel functional changes in intrinsic excitability induced by chronic alcohol. Moreover, there are strong genetic links between alcohol-related behaviors and genes encoding K_Ca2, K_V7, and GIRK channels, and pharmacologically targeting these channels reduces alcohol consumption and alcohol-related behaviors. Together, these studies demonstrate that chronic alcohol drinking produces adaptations in K_Ca2, K_V7, and GIRK channels leading to impaired regulation of the after-hyperpolarization and aberrant cell firing. Correcting the deficit in the after-hyperpolarization with positive modulators of K_Ca2 and K_V7 channels and altering the GIRK channel binding pocket to block the access of alcohol represent a potentially highly effective pharmacological approach that can restore changes in intrinsic excitability and reduce alcohol consumption in affected individuals.