HLA-B*3505 allele is a strong predictor for nevirapine-induced skin adverse drug reactions in HIV-infected Thai patients

Pembrolizumab-induced Stevens-Johnson syndrome/Toxic Epidermal Necrolysis in a Vietnamese patient with nonsmall-cell lung cancer

Chemoimmunotherapy is an effective therapy for an individual with nonsmall-cell lung cancer (NSCLC) without anaplastic lymphoma kinase or epidermal growth factor receptor mutations. However, it can also be related to adverse cutaneous reactions such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) with high morbidities and mortality rates. We present a case of a 65-year-old male with NSCLC who underwent first-line chemotherapy with paclitaxel, carboplatin, and pembrolizumab, which was later followed by a second cycle of the same therapies. The patient developed a fever and rash 12 days after the second cycle. Pembrolizumab was strongly suspected as the culprit medication because cutaneous reactions to this drug have been frequently reported and threw other medications used as less likely candidates. This is the first case reported in Vietnam of SJS/TEN related to pembrolizumab and contributes to our knowledge of severe skin reactions associated with immune checkpoint inhibitors.

Molecular insights into the HLA-B35 molecules' classification associated with HIV control

Human leukocyte antigen (HLA) class I molecules have been shown to influence the immune response to HIV infection and acquired immunodeficiency syndrome progression. Polymorphisms within the HLA-B35 molecules divide the family into two groups, namely, Px and PY. The Px group is associated with deleterious effects and accelerated disease progression in HIV+ patients, whereas the PY group is not. The classification is based on the preferential binding of a tyrosine at the C-terminal part of the peptide in the PY group, and a nontyrosine residue in the Px group. However, there is a lack of knowledge on the molecular differences between the two groups. Here, we have investigated three HLA-B35 molecules, namely, HLA-B*35:01 (PY), HLA-B*35:03 (Px) and HLA-B*35:05 (unclassified). We selected an HIV-derived peptide, NY9, and demonstrated that it can trigger a polyfunctional CD8+ T-cell response in HLA-B*35:01+ /HIV+ patients. We determined that in the complex with the NY9 peptide, the PY molecule was more stable than the Px molecule. We solved the crystal structures of the three HLA molecules in complex with the NY9 peptide, and structural similarities with HLA-B*35:01 would classify the HLA-B*35:05 within the PY group. Interestingly, we found that HLA-B*35:05 can also bind a small molecule in its cleft, suggesting that small drugs could bind as well.

Advances in understanding of the pathogenesis and therapeutic implications of drug reaction with eosinophilia and systemic symptoms: an updated review

Drug reaction with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome (DRESS/DIHS) is one type of severe cutaneous adverse reaction (SCAR). It is featured by fever, widespread skin lesions, protracted clinical course, internal organ involvement, and possibly long-term autoimmune sequelae. The presence of high-risk human leukocyte antigen (HLA) alleles, hypersensitivity reaction after culprit drug ingestion, and human herpesvirus reactivation may all contribute to its complex clinical manifestations. Some recent studies focusing on the roles of involved cytokines/chemokines and T cells co-signaling pathways in DRESS/DIHS were conducted. In addition, some predictors of disease severity and prognosis were also reported. In this review, we provided an update on the current understanding of the pathogenesis, potential biomarkers, and the relevant therapeutic rationales of DRESS/DIHS.

Updates on the immunopathology and genomics of severe cutaneous adverse drug reactions

Severe cutaneous adverse reactions (SCARs) such as Stevens-Johnson syndrome, toxic epidermal necrolysis (SJS/TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS) cause significant morbidity and mortality and impede new drug development. HLA class I associations with SJS/TEN and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome have aided preventive efforts and provided insights into immunopathogenesis. In SJS/TEN, HLA class I-restricted oligoclonal CD8+ T-cell responses occur at the tissue level. However, specific HLA risk allele(s) and antigens driving this response have not been identified for most drugs. HLA risk alleles also have incomplete positive and negative predictive values, making truly comprehensive screening currently challenging. Although, there have been key paradigm shifts in knowledge regarding drug hypersensitivity, there are still many open and unanswered questions about SCAR immunopathogenesis, as well as genetic and environmental risk. In addition to understanding the cellular and molecular basis of SCAR at the single-cell level, identification of the MHC-restricted drug-reactive self- or viral peptides driving the hypersensitivity reaction will also be critical to advancing premarketing strategies to predict risk at an individual and drug level. This will also enable identification of biologic markers for earlier diagnosis and accurate prognosis, as well as drug causality and targeted therapeutics.

Delayed Drug Hypersensitivity Reactions: Molecular Recognition, Genetic Susceptibility, and Immune Mediators

Drug hypersensitivity reactions are classified into immediate and delayed types, according to the onset time. In contrast to the immediate type, delayed drug hypersensitivity mainly involves T lymphocyte recognition of the drug antigens and cell activation. The clinical presentations of such hypersensitivity are various and range from mild reactions (e.g., maculopapular exanthema (MPE) and fixed drug eruption (FDE)), to drug-induced liver injury (DILI) and severe cutaneous adverse reactions (SCARs) (e.g., Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalized exanthematous pustulosis (AGEP)). The common culprits of delayed drug hypersensitivity include anti-epileptics, antibiotics, anti-gout agents, anti-viral drugs, etc. Delayed drug hypersensitivity is proposed to be initiated by different models of molecular recognition, composed of drug/metabolite antigen and endogenous peptide, HLA presentation, and T cell receptor (TCR) interaction. Increasing the genetic variants of HLA loci and drug metabolic enzymes has been identified to be responsible for delayed drug hypersensitivity. Furthermore, preferential TCR clonotypes, and the activation of cytotoxic proteins/cytokines/chemokines, are also involved in the pathogenesis of delayed drug hypersensitivity. This review provides a summary of the current understanding of the molecular recognition, genetic susceptibility, and immune mediators of delayed drug hypersensitivity.

Association of Human Leukocyte Antigen Alleles and Hypersensitivity of Efavirenz/Nevirapine in HIV-Infected Chinese Patients

To examine the association between human leukocyte antigen (HLA) and nevirapine (NVP)- and efavirenz (EFV)-induced cutaneous adverse reactions in human immunodeficiency virus (HIV) patients, we conducted a case-control study at our center consisting of 96 patients. Patients were further assigned based on the occurrence of cutaneous adverse events and the drugs involved. All patients were subjected to next generation sequencing (NGS)-based screening with focus on HLA phenotype, including the presence of HLA-B, HLA-C, and HLA-DRB1. Our data indicated that the HLA-C*01:02:01 allele presence was observed in 47.4% (18/38) of patients in the EFV-hypersensitivity group compared with 18.9% (7/30) in the control group [odds ratio (OR) = 5.837; 95% confidence interval (CI) = 1.727-19.722, p = .005]. In contrast, the occurrence of HLA-DRB1*08:03 was found to be significantly lower in the EFV-hypersensitivity group (4/38, 10.5%) compared with the corresponding control group (12/37, 32.4%) (OR = 0.148; 95% CI = 0.035-0.625, p = .009). In addition, the HLA-DRB1*04:05:01 antigen was expressed more frequently in the NVP-hypersensitivity group (23.8%, 5/21) compared with the control group (10.8%, 4/37) (OR = 7; 95% CI = 1.265-38.793, p = .026). Our data not only revealed a significant association between HLA-C*01:02:01 and EFV-induced cutaneous adverse reactions but may also shed light on defining the treatment for Chinese HIV patients.

A low-cost, sensitive and specific PCR-based tool for rapid clinical detection of HLA-B*35 alleles associated with delayed drug hypersensitivity reactions

HLA (HLA) alleles are risk factors for CD8+ T-cell-mediated drug hypersensitivity reactions. However, as most HLA associations are incompletely predictive and/or involve risk alleles at low frequency, costly sequence-based typing can elude an economically productive cost: benefit ratio for clinical validation studies and diagnostic and/or preventative screening. Hence rapid and low-cost detection assays are now required, both for single alleles but also across risk loci associated with broader multi-disease risk; exemplified by associations with diverse alleles in HLA-B*35, including HLA-B*35:01 and green tea- or co-trimoxazole-induced liver injury. Here, we developed a cost-effective (<$10USD) qPCR assay for rapid (<2.5 h) clinical detection of HLA-B*35 alleles. The assay was validated using 430 DNA samples with previous American society for histocompatibility and immunogenetics-accredited sequence-based high-resolution HLA typing, positively detecting all HLA-B*35 allelic variants in our cohort, and as expected by primer design, the six samples that expressed low-frequency B*78:01. The assay did not result in positive detection for any negative control allele. With expected detection of B*35 and B*78, our assay sensitivity (95% CI, 95.07%-100.00%) and specificity (95% CI, 98.97%-100.00%) of 100% using as low as 10 ng of DNA provides a reliable HLA-B*35 screening tool for clinical validation and HLA-risk-based prevention and diagnostics.

Distribution of HLA-B Alleles and Haplotypes in Qatari: Recommendation for Establishing Pharmacogenomic Markers Screening for Drug Hypersensitivity

Human leukocyte antigen (HLA) proteins are present at the cellular surface of antigen-presenting cells and play a crucial role in the adaptive immune response. Class I genes, specifically certain HLA-B alleles, are associated with adverse drug reactions (ADRs) and are used as pharmacogenetic markers. Although ADRs are a common causes of hospitalization and mortality, the data on the prevalence of HLA-B pharmacogenetics markers in Arab countries are scarce. In this study, we investigated the frequencies of major HLA-B pharmacogenomics markers in the Qatari population. Next-generation sequencing data from 1,098 Qatari individuals were employed for HLA-B typing using HLA-HD version 1.4.0 and IPD-IMGT/HLA database. In addition, HLA-B pharmacogenetics markers were obtained from the HLA Adverse Drug Reaction Database. In total, 469 major HLA-B pharmacogenetic markers were identified, with HLA-B*51:01 being the most frequent pharmacogenetic marker (26.67%) in the Qatari population. Moreover, HLA-B*51:01 is associated with phenytoin- and clindamycin-induced ADRs. The second most frequent pharmacogenetic marker was the HLA-B*58:01 allele (6.56%), which is associated with allopurinol-induced ADRs. The third most frequent pharmacogenetic marker was the HLA-B*44:03 allele, which is associated with phenytoin-induced ADRs. The establishment of a pharmacogenetics screening program in Qatar for cost effective interventions aimed at preventing drug-induced hypersensitivity can be aided by the highly prevalent HLA-B pharmacogenetic markers detected here.

The Association of HLA-B*35 and GSTT1 Genotypes and Hepatotoxicity in Thai People Living with HIV

Glutathione s-transferase (GST) is a family of drug-metabolizing enzymes responsible for metabolizing and detoxifying drugs and xenobiotic substances. Therefore, deletion polymorphisms of GSTs can be implicated in developing several pathological conditions, including antiretroviral drug-induced liver injury (ARVDILI). Notably, GST polymorphisms have been shown to be associated with ARVDILI risk. However, data on GST polymorphisms in the Thai population are limited. Therefore, this study investigated possible associations between GST genetic polymorphisms and ARVDILI development. A total of 362 people living with HIV (PLHIV) and 85 healthy controls from multiple centers were enrolled. GSTM1 and GSTT1 genetic polymorphisms were determined using polymerase chain reactions. In addition, HLA genotypes were determined using a sequence-based HLA typing method. After comparing GST genotypic frequencies, there was no significant difference between PLHIV and healthy volunteers. However, while observing the PLHIV group, GSTT1 wild type was significantly associated with a 2.04-fold increased risk of ARVDILI (95%CI: 1.01, 4.14; p = 0.045). Interestingly, a combination of GSTT1 wild type and HLA-B*35:05 was associated with a 2.28-fold higher risk of ARVDILI (95%CI: 1.15, 4.50; p = 0.02). Collectively, GSTT1 wild type and a combination of GSTT1 wild type plus HLA-B*35:05 were associated with susceptibility to ARVDILI in the Thai population.

An Updated Review of Genetic Associations With Severe Adverse Drug Reactions: Translation and Implementation of Pharmacogenomic Testing in Clinical Practice

Adverse drug reactions (ADR) remain the major problems in healthcare. Most severe ADR are unpredictable, dose-independent and termed as type B idiosyncratic reactions. Recent pharmacogenomic studies have demonstrated the strong associations between severe ADR and genetic markers, including specific HLA alleles (e.g., HLA-B*15:02/HLA-B*57:01/HLA-A*31:01 for carbamazepine-induced severe cutaneous adverse drug reactions [SCAR], HLA-B*58:01 for allopurinol-SCAR, HLA-B*57:01 for abacavir-hypersensitivity, HLA-B*13:01 for dapsone/co-trimoxazole-induced SCAR, and HLA-A*33:01 for terbinafine-induced liver injury), drug metabolism enzymes (such as CYP2C9*3 for phenytoin-induced SCAR and missense variant of TPMT/NUDT15 for thiopurine-induced leukopenia), drug transporters (e.g., SLCO1B1 polymorphism for statin-induced myopathy), and T cell receptors (Sulfanilamide binding into the CDR3/Vα of the TCR 1.3). This mini review article aims to summarize the current knowledge of pharmacogenomics of severe ADR, and the potentially clinical use of these genetic markers for avoidance of ADR.

Drug-Induced Hypersensitivity Syndrome (DIHS)/Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS): Clinical Features and Pathogenesis

Drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS) is one example of a severe delayed T-cell-mediated adverse drug reaction. DIHS/DRESS presents with fever, widespread rash and facial edema, organ involvement, and hematological abnormalities, including eosinophilia and atypical lymphocytosis. DIHS/DRESS is associated with relapse 2 to 4 weeks after acute symptoms, often coinciding with reactivation of prevalent chronic persistent human herpesviruses such as human herpesvirus 6, EBV, and cytomegalovirus. The mortality of DIHS/DRESS is up to 10% and often related to unrecognized myocarditis and cytomegalovirus complications, with longer-term consequences that contribute to morbidity including autoimmune diseases such as thyroiditis. It is essential that all potential drug causes, including all new drugs introduced within the 8 weeks preceding onset of DIHS/DRESS symptoms, are identified. All potential drug culprits, as well as drugs that are closely related structurally to the culprit drug, should be avoided in the future. Systemic corticosteroids have remained the mainstay for the treatment of DIHS/DRESS with internal organ involvement. Steroid-sparing agents, such as cyclosporine, mycophenolate mofetil, and monthly intravenous immune globulin, have been successfully used for treatment, and careful follow-up for cytomegalovirus reactivation is recommended. Strong associations between HLA class I alleles and DIHS/DRESS predisposition include HLA-B∗13:01 and dapsone, HLA-B∗58:01 and allopurinol, and HLA-B∗32:01 and vancomycin. These have opened a pathway for prevention, risk stratification, and earlier diagnosis. Single-cell sequencing and other studies of immunopathogenesis promise to identify targeted treatment approaches.

Drug Reaction with Eosinophilia and Systemic Symptoms (DReSS)/Drug-Induced Hypersensitivity Syndrome (DiHS)-Readdressing the DReSS

Drug reaction with eosinophilia and systemic symptoms (DReSS), also known as drug-induced hypersensitivity syndrome (DiHS), is a severe, systemic, T cell mediated drug reaction with combinations of cutaneous, hematologic, and internal organ involvement. Pathogenesis of DReSS is multi-factorial, involving drug-exposure, genetic predisposition through specific human leukocyte antigen (HLA) alleles and metabolism defects, viral reactivation, and immune dysregulation. Clinical features of this condition are delayed, stepwise, and heterogenous, making this syndrome challenging to recognize and diagnose. Two sets of validated diagnostic criteria exist that can be employed to diagnose DReSS/DiHS. Methods to improve early recognition of DReSS and predict disease severity has been a recent area of research focus. In vitro and in vivo tests can be employed to confirm the diagnosis and help identify culprit drugs. The mainstay treatment of DReSS is prompt withdrawal of the culprit drug, supportive treatment, and immunosuppression depending on the severity of disease. We present a comprehensive review on the most recent research and literature on DReSS, with emphasis on pathogenesis, clinical features, diagnosis, confirmatory testing modalities, and treatment. Additionally, this summary aims to highlight the differing viewpoints on this severe disease and broaden our perspective on the condition known as DReSS.

HLA-associated adverse drug reactions - scoping review

Alleles of the human leukocyte antigen (HLA) system have been associated with the occurrence of idiosyncratic adverse drug reactions (ADRs). Accordingly, it is assumed that pre-emptive testing for the presence of certain HLA alleles (HLA-typing) could prevent these ADRs in carriers. In order to perceive the current evidence for HLA-associated ADRs, we conducted a scoping review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The literature search on PubMed and on Embase was carried out on the July 8 and 9, 2020, respectively. To be included in the scoping review, the studies had to investigate an association of any HLA-associated ADR with any small molecule approved and available on the Swiss market. We considered English and German primary literature published since 2002. A total of 149 studies were included, whereof most were retrospective, whereas one was a prospective randomized controlled trial. The majority of the studies (n = 33) described the association of HLA-B*15:02 with carbamazepine. It was not possible to directly compare the studies, as they were too heterogeneous in terms of the ADR definition, the HLA alleles, the number of participants, and the study types. Therefore, we summarized the results in a descriptive manner. Even if an interpretation of the outcomes remains open, the descriptive overview revealed the prevailing complexity and uncertainty in the field. For the future, consistent definitions on the different phenotypes need to be established and applied and the reporting of association studies should follow a harmonized structure.

Genetics of Severe Cutaneous Adverse Reactions

Severe cutaneous adverse reactions (SCARs) including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug rash with eosinophilia and systemic symptoms (DRESS) are T cells-mediated life-threatening immune reactions, most commonly induced by drug. The last decade has seen significant progress in SCARs research. Recent studies have unveiled the pathogenesis of SCARs involved in susceptible genes, including human leukocyte antigens (HLA) and drugs-T cell receptor (TCR) interaction that may trigger T cell activation with downstream immune signaling of cytokines/chemokines and specific cytotoxic proteins releases. Advances in identification of multiple genetic alleles associated with specific drugs related SCARS in different populations is an important breakthrough in recent years for prevention of SCARs. This article summarized the findings on genetic factors related to SJS/TEN, especially for HLA.

Genomic Risk Factors Driving Immune-Mediated Delayed Drug Hypersensitivity Reactions

Adverse drug reactions (ADRs) remain associated with significant mortality. Delayed hypersensitivity reactions (DHRs) that occur greater than 6 h following drug administration are T-cell mediated with many severe DHRs now associated with human leukocyte antigen (HLA) risk alleles, opening pathways for clinical prediction and prevention. However, incomplete negative predictive value (NPV), low positive predictive value (PPV), and a large number needed to test (NNT) to prevent one case have practically prevented large-scale and cost-effective screening implementation. Additional factors outside of HLA contributing to risk of severe T-cell-mediated DHRs include variation in drug metabolism, T-cell receptor (TCR) specificity, and, most recently, HLA-presented immunopeptidome-processing efficiencies via endoplasmic reticulum aminopeptidase (ERAP). Active research continues toward identification of other highly polymorphic factors likely to impose risk. These include those previously associated with T-cell-mediated HLA-associated infectious or auto-immune disease such as Killer cell immunoglobulin-like receptors (KIR), epistatically linked with HLA class I to regulate NK- and T-cell-mediated cytotoxic degranulation, and co-inhibitory signaling pathways for which therapeutic blockade in cancer immunotherapy is now associated with an increased incidence of DHRs. As such, the field now recognizes that susceptibility is not simply a static product of genetics but that individuals may experience dynamic risk, skewed toward immune activation through therapeutic interventions and epigenetic modifications driven by ecological exposures. This review provides an updated overview of current and proposed genetic factors thought to predispose risk for severe T-cell-mediated DHRs.

A novel association of efavirenz induced severe cutaneous adverse reactions with HLA- DRB1*03:01: A case-control study from North-East India

HIV-infected patients have a higher risk of developing cutaneous reactions to drugs than the general population. Severe cutaneous adverse reactions (SCARs) are not uncommon in patients taking antiretroviral therapy (HAART]. To evaluate HLA class I and II allele frequencies in HIV patients on HAART who develop SCARs due to nevirapine (NVP] or efavirenz (EFZ] containing regime and compare this genotype composition with HAART tolerant patients and healthy organ donors. A case-control study for 4 years was conducted with four subsets of patients hailing from north-east India:Cohort 1- HIV seropositive patients who developed SCARs due to EFZ (n = 8];Cohort 2 - HIV seropositive patients who developed SCARs due to NVP (n = 15]; Cohort 3 -HIV seropositive NVP/EFZ-tolerant patients (n = 18]; Cohort 4 - Healthy HIV seronegative organ donors (n = 169].Cohort 3 & 4 acted as control-group. These patients were genotyped for the HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQB1, and HLA-DPB1 by a sequence-based HLA typing method. HLA-DRB1*03:01 allele revealed a significant association with EFZ regimen-induced SCARs in 62.5% patients compared with only 5.56% observed in HAART-tolerant patients and 4.14% in healthy organ. HLA-B*3505was found to be significantly associated with NVP induced SCARs. We found significant novel association of HLA-DRB1*03:01 with EFZ induced SCARs in North-East Indian HIV patients. Thus, HLA-DRB*03:01 may be useful as a genetic marker to avoid EFZ induced serious cutaneous rashes. The molecular HLA characterization of these alleles may provide a novel insight into the immunological basis of the antiretroviral drug reactions.

Genetic variations in medical research in the past, at present and in the future

As we look so different, our genomic sequences vary enormously. The differences in our genome, genetic variations, have played very significant roles in medical research and have contributed to improvement of medical managements in the last 2-3 decades. Genetic variations include germline variations, somatic mutations, and diversities in receptor genes of rearranged immune cells, T cells and B cells. Germline variants are in some cases causative of genetic diseases, are associated with the risk of various diseases, and also affect drug efficacies or adverse events. Some somatic mutations are causative of tumor development. Recent DNA sequencing technologies allow us to perform single-cell analysis or detailed repertoire analysis of B and T cells. It is critically important to investigate temporal changes in immune environment in various anatomical regions in the next one to two decades. In this review article, we would like to introduce the roles of genetic variations in medical fields in the past, at present and in the future.

An in vitro coculture system of human peripheral blood mononuclear cells with hepatocellular carcinoma-derived cells for predicting drug-induced liver injury

Preventing clinical drug-induced liver injury (DILI) remains a major challenge, because DILI develops via multifactorial mechanisms. Immune and inflammatory reactions are considered important mechanisms of DILI; however, biomarkers from in vitro systems using immune cells have not been comprehensively studied. The aims of this study were (1) to identify promising biomarker genes for predicting DILI in an in vitro coculture model of peripheral blood mononuclear cells (PBMCs) with a human liver cell line, and (2) to evaluate these genes as predictors of DILI using a panel of drugs with different clinical DILI risk. Transcriptome-wide analysis of PBMCs cocultured with HepG2 or differentiated HepaRG cells that were treated with several drugs revealed an appropriate separation of DILI-positive and DILI-negative drugs, from which 12 putative biomarker genes were selected. To evaluate the predictive performance of these genes, PBMCs cocultured with HepG2 cells were exposed to 77 different drugs, and gene expression levels in PBMCs were determined. The MET proto-oncogene receptor tyrosine kinase (MET) showed the highest area under the receiver-operating characteristic curve (AUC) value of 0.81 among the 12 genes with a high sensitivity/specificity (85/66%). However, a stepwise logistic regression model using the 12 identified genes showed the highest AUC value of 0.94 with a high sensitivity/specificity (93/86%). Taken together, we established a coculture system using PBMCs and HepG2 cells and selected biomarkers that can predict DILI risk. The established model would be useful in detecting the DILI potential of compounds, in particular those that involve an immune mechanism.

Mechanistic insights into antiretroviral drug-induced liver injury

All classes of antiretroviral therapy (ART) have been implicated to induce adverse drug reactions such drug-induced liver injury (DILI) and immune-mediated adverse reactions in Human Immunodeficiency Virus (HIV) infected individuals. Patients that develop adverse drug reactions tend to have prolonged stays in hospital and may require to change to alternative regimens if reactions persist upon rechallenge or if rechallenge is contraindicated due to severity of the adverse reaction. Diagnosis of DILI remains a huge obstacle that delays timely interventions, since it is still based largely on exclusion of other causes. There is an urgent need to develop robust diagnostic and predictive biomarkers that could be used alongside the available tools (biopsy, imaging, and serological tests for liver enzymes) to give a specific diagnosis of DILI. Crucial to this is also achieving consensus in the definition of DILI so that robust studies can be undertaken. Importantly, it is crucial that we gain deeper insights into the mechanism of DILI so that patients can receive appropriate management. In general, it has been demonstrated that the mechanism of ART-induced liver injury is driven by four main mechanisms: mitochondrial toxicity, metabolic host-mediated injury, immune reconstitution, and hypersensitivity reactions. The focus of this review is to discuss the type and phenotypes of DILI that are caused by the first line ART regimens. Furthermore, we will summarize recent studies that have elucidated the cellular and molecular mechanisms of DILI both in vivo and in vitro.

Genetic variants associated with T cell-mediated cutaneous adverse drug reactions: A PRISMA-compliant systematic review-An EAACI position paper

Drug hypersensitivity reactions (DHRs) are associated with high global morbidity and mortality. Cutaneous T cell-mediated reactions classically occur more than 6 hours after drug administration and include life-threatening conditions such as toxic epidermal necrolysis, Stevens-Johnson syndrome, and hypersensitivity syndrome. Over the last 20 years, significant advances have been made in our understanding of the pathogenesis of DHRs with the identification of human leukocyte antigens as predisposing factors. This has led to the development of pharmacogenetic screening tests, such as HLA-B*57:01 in abacavir therapy, which has successfully reduced the incidence of abacavir hypersensitivity reactions. We have completed a PRISMA-compliant systematic review to identify genetic associations that have been reported in DHRs. In total, 105 studies (5554 cases and 123 548 controls) have been included in the review reporting genetic associations with carbamazepine (n = 31), other aromatic antiepileptic drugs (n = 24), abacavir (n = 11), nevirapine (n = 14), trimethoprim-sulfamethoxazole (n = 11), dapsone (n = 4), allopurinol (n = 10), and other drugs (n = 5). The most commonly reported genetic variants associated with DHRs are located in human leukocyte antigen genes and genes involved in drug metabolism pathways. Increasing our understanding of genetic variants that contribute to DHRs will allow us to improve diagnosis, develop new treatments, and predict and prevent DHRs in the future.

Genetic Diversity of HLA Class I and Class II Alleles in Thai Populations: Contribution to Genotype-Guided Therapeutics

Human leukocyte antigen (HLA) class I and II are known to have association with severe cutaneous adverse reactions (SCARs) when exposing to certain drug treatment. Due to genetic differences at population level, drug hypersensitivity reactions are varied, and thus common pharmacogenetics markers for one country might be different from another country, for instance, HLA-A*31:01 is associated with carbamazepine (CBZ)-induced SCARs in European and Japanese while HLA-B*15:02 is associated with CBZ-induced Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) among Taiwanese and Southeast Asian. Such differences pose a major challenge to prevent drug hypersensitivity when pharmacogenetics cannot be ubiquitously and efficiently translated into clinic. Therefore, a population-wide study of the distribution of HLA-pharmacogenetics markers is needed. This work presents a study of Thai HLA alleles on both HLA class I and II genes from 470 unrelated Thai individuals by means of polymerase chain reaction sequence-specific oligonucleotide (PCR-SSO) in which oligonucleotide probes along the stretches of HLA-A, -B, -C, -DRB1, -DQA1, and -DQB1 genes were genotyped. These 470 individuals were selected according to their regional locations, which were from North, Northeast, South, Central, and a capital city, Bangkok. Top ranked HLA alleles in Thai population include HLA-A*11:01 (26.06%), -B*46:01 (14.04%), -C* 01:02 (17.13%), -DRB1*12:02 (15.32%), -DQA1*01:01 (24.89%), and -DQB1*05:02 (21.28%). The results revealed that the distribution of HLA-pharmacogenetics alleles from the South had more HLA-B75 family that a typical HLA-B*15:02 pharmacogenetics test for SJS/TEN screening would not cover. Besides the view across the nation, when compared HLA alleles from Thai population with HLA alleles from both European and Asian countries, the distribution landscape of HLA-associated drug hypersensitivity across many countries could be observed. Consequently, this pharmacogenetics database offers a comprehensive view of pharmacogenetics marker distribution in Thailand that could be used as a reference for other Southeast Asian countries to validate the feasibility of their future pharmacogenetics deployment.

Association of HLA-A*31:01 Screening With the Incidence of Carbamazepine-Induced Cutaneous Adverse Reactions in a Japanese Population

Importance

Carbamazepine, a commonly used antiepileptic drug, is one of the most common causes of cutaneous adverse drug reactions (cADRs) worldwide. The allele HLA-A*31:01 is reportedly associated with carbamazepine-induced cADRs in Japanese and European populations; however, the clinical utility of HLA-A*31:01 has not been evaluated.

Objective

To assess the use of HLA-A*31:01 genetic screening to identify Japanese individuals at risk of carbamazepine-induced cADRs.

Design, Setting, and Participants

This cohort study was conducted across 36 hospitals in Japan from January 2012 to November 2014 among 1202 patients who had been deemed suitable to start treatment with carbamazepine. Preemptive HLA-A*31:01 genetic screening was performed for 1187 participants. Patients who did not start treatment with carbamazepine or alternative drugs were excluded. Participants were interviewed once weekly for 8 weeks to monitor the development of cADRs. Data analysis was performed from June 8, 2015, to December 27, 2016.

Exposures

Neuropsychiatrists were asked to prescribe carbamazepine for patients who tested negative for HLA-A*31:01 and alternative drugs for those who tested positive for HLA-A*31:01.

Main Outcomes and Measures

Incidence of carbamazepine-induced cADRs.

Results

Of the 1130 included patients who were prescribed carbamazepine or alternative drugs, the mean (range) age was 37.4 (0-95) years, 614 (54.3%) were men, and 198 (17.5%) were positive for HLA-A*31:01. Expert dermatologists identified 23 patients (2.0%) who had carbamazepine-induced cADRs, of which 4 patients required hospitalization. Drug-induced hypersensitivity syndrome was observed for 3 patients, maculopapular eruption for 9 patients, erythema multiforme for 5 patients, and an undetermined type of cADR for 6 patients. No patient developed Stevens-Johnson syndrome or toxic epidermal necrolysis. Compared with historical controls, the incidence of carbamazepine-induced cADRs was significantly decreased (for BioBank Japan data: incidence, 3.4%; odds ratio, 0.60; 95% CI, 0.36-1.00; P = .048; for the Japan Medical Data Centre claims database: incidence, 5.1%; odds ratio, 0.39; 95% CI, 0.26-0.59; P < .001).

Conclusions and Relevance

Preemptive HLA-A*31:01 genetic screening significantly decreased the incidence of carbamazepine-induced cADRs among Japanese patients, which suggests that it may be warranted in routine clinical practice.

Genetic testing for prevention of severe drug-induced skin rash

BACKGROUND

Drug-induced skin reactions present with a range of clinical symptoms, from mild maculopapular skin rashes to potentially fatal blistering skin rashes - such as Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) - which may result in death. Milder reactions may be troublesome and lead to low drug compliance. The pathogenesis of these drug reactions is not yet fully understood; however, there is evidence that pretreatment genetic testing may help to predict and prevent these reactions in some cases.

OBJECTIVES

To assess the effects of prospective pharmacogenetic screening to reduce drug-associated skin reactions in a patient population.

SEARCH METHODS

We searched the following databases up to July 2018: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase and LILACS. We also searched five trials registers, and checked the reference lists of included studies and relevant reviews for further references to relevant randomised controlled trials (RCTs).

SELECTION CRITERIA

We included RCTs of participants who had prospective pharmacogenetic screening to determine genetic variants associated with hypersensitivity reactions, compared with those who did not have prospective pharmacogenetic screening. We included participants in any setting, who were of any age, gender, and ethnicity, who had been prescribed drugs known to cause delayed type hypersensitivity reactions.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. To assess studies for inclusion, two review authors independently screened all of the titles and abstracts of publications identified by the searches. Because there was only one included study, many of the planned data analyses were not applicable to the review. We used GRADE to assess the quality of the included study.The review's primary outcomes were the incidence of severe skin rashes with systemic symptoms (such as fever and multiple organ involvement), and long-term effects (such as scarring of eyelids or lung tissue). Secondary outcomes were hospitalisation for drug-induced skin reactions, blistering skin reactions (such as SJS, hypersensitivity (HSS) syndrome), and death.

MAIN RESULTS

One study, which was a randomised, double-blind, controlled, multicentre trial, fulfilled our inclusion criteria. The trial included 1956 adult participants (74% men, with a mean age of 42 years) across 265 centres (medical centres, hospitals, outpatient clinics) in 19 countries around the world who were infected with HIV-type 1 and who had not received abacavir previously. The participants, who had a clinical need for treatment with an antiretroviral-drug regimen containing abacavir, were randomly assigned to undergo prospective human leukocyte antigen (HLA) Class I, locus B, allele 57:01 (HLA-B*57:01) screening (prospective-screening group) before this treatment, or to undergo a standard-care approach of abacavir use without prospective HLA-B*57:01 screening (control group). Participants who tested positive for HLA-B*57:01 were not given abacavir; instead, they received antiretroviral therapy that did not include abacavir. The control group did have retrospective HLA-B*57:01 pharmacogenetic testing. The trial duration was six months. Each participant was observed for six weeks. Assessments were performed at the time of study entry, at baseline (day one of abacavir treatment), and at weeks one, two and six. This study was funded by the manufacturer of abacavir, GlaxoSmithKline.The study did not assess any of our primary outcomes, and it measured none of our secondary outcomes in isolation. However, it did assess an outcome of (characteristically severe) hypersensitivity reaction which included (but was not limited to) our secondary outcomes of HSS and SJS/TEN.The study demonstrated that prospective HLA-B*57:01 screening probably reduces the incidence of hypersensitivity reaction to abacavir. The incidence of clinically diagnosed HSS reaction to abacavir was lower in the screening arm (risk ratio (RR) 0.43, 95% confidence interval (CI) 0.28 to 0.67; 1650 participants; moderate-quality evidence), as was immunologically confirmed HSS reaction (RR 0.02, 95% 0.00 to 0.37; 1644 participants; moderate-quality evidence). A positive result from an epicutaneous patch test performed six to ten weeks after clinical diagnosis provided immunological confirmation.Overall, the study demonstrates a low risk of bias across five out of seven domains. There was a high risk of detection bias because hypersensitivity reactions were diagnosed by the principal investigator at the recruitment site without the use of predefined clinical criteria. Although there was also high risk of attrition bias due to excluding participants with incomplete follow-up from analyses, the authors did undertake a series of sensitivity analyses based on the intention-to-treat population, which demonstrated consistent results with the primary analysis. We rated the study quality as moderate-quality using GRADE criteria.

AUTHORS' CONCLUSIONS

Prospective screening for HLA-B*57:01 probably reduces severe hypersensitivity skin reactions to abacavir in patients positive for HIV-type 1. However, these results are only based on one study, which was at high risk of attrition and detection bias.Our primary outcomes (incidence of severe skin rashes with systemic symptoms, and long-term effects) were not assessed by the trial, and only one of the review's secondary outcomes was measured (hypersensitivity reaction); thus, we found no evidence relating to hospitalisation, death, or long-term conditions resulting from drug injury.We found no eligible evidence on genetic testing for severe drug-induced skin rash in relation to different drugs and classes of drugs. Further clinical trials based on other drugs, and in different patient populations, would be useful for advising policy changes for improving the prevention of adverse skin reactions to drug treatments.

Associations between human leukocyte antigen polymorphisms and hypersensitivity to antiretroviral therapy in patients with human immunodeficiency virus: a meta-analysis

BACKGROUND

Human leukocyte antigen (HLA) alleles are implicated in drug-induced hypersensitivity, including by nevirapine and abacavir. The purpose of this meta-analysis was to evaluate the relationship between HLA polymorphisms and hypersensitivity to antiretroviral therapy in human immunodeficiency virus (HIV)-infected patients.

METHODS

We conducted a systematic search of PubMed, Embase, Web of Science, and the Cochrane Library for studies that evaluated the associations of HLA polymorphisms with antiretroviral therapy-induced hypersensitivity published in April 2019. The summary odds ratios (ORs) with 95% confidence intervals (CIs) were considered as estimates of the effect.

RESULTS

The meta-analysis included 17 studies that assessed a total of 4273 patients. First, carriers of HLA-A *24 were associated with an increased risk of hypersensitivity among patients with HIV who received antiretroviral therapy (OR: 12.12; P = 0.018). Second, five SNPs of HLA-B genotypes, including *18 (OR: 1.63; P = 0.028), *35 (OR: 2.31; P = 0.002), *39 (OR: 11.85; P = 0.040), *51 (OR: 1.66; P = 0.028), and *81 (OR: 8.11; P = 0.021), were associated with an increased risk of hypersensitivity. Conversely, carriers of HLA-B *15 were associated with a reduced risk of hypersensitivity (OR: 0.43; P < 0.001). Third, HLA-C *04 was associated with an increased risk of hypersensitivity (OR: 3.09; P < 0.001), whereas a lower risk for hypersensitivity was observed in patients who were carriers of HLA-C *02 (OR: 0.22; P = 0.030), *03 (OR: 0.53; P = 0.049), and *07 (OR: 0.61; P = 0.044). Finally, carriers of HLA-DRB1 *05 (OR: 0.18; P = 0.006) and *15 (OR: 0.23; P = 0.013) were associated with a reduced risk of hypersensitivity among patients receiving antiretroviral therapy.

CONCLUSIONS

The findings of this meta-analysis indicated patients carrying HLA-A *24, HLA-B *18, *35, *39, *51, *81, HLA-C *04 were associated with a higher risk of hypersensitivity. Conversely, subjects carrying HLA-B *15, HLA-C *02, *03, *07, HLA-DRB1 *05, *15 were associated with a reduced risk of hypersensitivity.

Novel genetic and epigenetic factors of importance for inter-individual differences in drug disposition, response and toxicity

Individuals differ substantially in their response to pharmacological treatment. Personalized medicine aspires to embrace these inter-individual differences and customize therapy by taking a wealth of patient-specific data into account. Pharmacogenomic constitutes a cornerstone of personalized medicine that provides therapeutic guidance based on the genomic profile of a given patient. Pharmacogenomics already has applications in the clinics, particularly in oncology, whereas future development in this area is needed in order to establish pharmacogenomic biomarkers as useful clinical tools. In this review we present an updated overview of current and emerging pharmacogenomic biomarkers in different therapeutic areas and critically discuss their potential to transform clinical care. Furthermore, we discuss opportunities of technological, methodological and institutional advances to improve biomarker discovery. We also summarize recent progress in our understanding of epigenetic effects on drug disposition and response, including a discussion of the only few pharmacogenomic biomarkers implemented into routine care. We anticipate, in part due to exciting rapid developments in Next Generation Sequencing technologies, machine learning methods and national biobanks, that the field will make great advances in the upcoming years towards unlocking the full potential of genomic data.

Singularities of nevirapine metabolism: from sex-dependent differences to idiosyncratic toxicity

Nevirapine (NVP) is a first-generation non-nucleoside reverse transcriptase inhibitor widely used for the treatment and prophylaxis of human immunodeficiency virus infection. The drug is taken throughout the patient's life and, due to the availability of an extended-release formulation, it is administered once daily. This antiretroviral is one of the scarce examples of drugs with prescription criteria based on sex, in order to prevent adverse reactions. The therapy with NVP has been associated with potentially life-threatening liver and idiosyncratic skin toxicity. Multiple evidence has emerged regarding the formation of electrophilic NVP metabolites as crucial for adverse idiosyncratic reactions. The formation of reactive metabolites that yield covalent adducts with proteins has been demonstrated in patients under NVP-based treatment. Interestingly, several pharmacogenetic- and sex-related factors associated with NVP toxicity can be mechanistically explained by an imbalance toward increased formation of NVP-derived reactive metabolites and/or impaired detoxification capability. Moreover, the haptenation of self-proteins by these reactive species provides a plausible link between NVP bioactivation and immunotoxicity, further supporting the relevance of this toxicokinetics hypothesis. In the current paper, we review the existing knowledge and recent developments on NVP metabolism and their relation to NVP toxicity.

Drug-Induced Skin Adverse Reactions: The Role of Pharmacogenomics in Their Prevention

Adverse drug reactions (ADRs) affect many patients and remain a major public health problem, as they are a common cause of morbidity and mortality. It is estimated that ADRs are responsible for about 6% of hospital admissions and about 9% of hospitalization costs. Skin is the organ that is most frequently involved in ADRs. Drug-induced skin injuries vary from mild maculopapular eruptions (MPE) to severe cutaneous adverse reactions (SCARs) that are potentially life threatening. Genetic factors have been suggested to contribute to these SCARs, and most significant genetic associations have been identified in the major histocompatibility complex (MHC) genes. Common drugs associated with SCARs connected with strong genetic risk factors include antiepileptic drugs (AEDs), allopurinol, abacavir, nevirapine, sulfonamides, dapsone, non-steroidal anti-inflammatory drugs (NSAIDs), and analgesic drugs. However, genetic associations vary between different ethnic populations. Differences may in part be explained by the different prevalence of HLA (human leukocyte antigen) alleles among ethnic groups. In this review, we present and discuss the recent advances in genetic associations with ADRs in the skin. Many of these ADRs are now preventable with pharmacogenetic screening.

Genetic markers of severe cutaneous adverse reactions

Adverse drug reactions can cause considerable discomfort. They can be life-threatening in severe cases, requiring or prolonging hospitalization, impeding proper treatment, and increasing treatment costs considerably. Although the incidence of severe cutaneous adverse reactions (SCARs) is low, they can be serious, have permanent sequelae, or lead to death. A recent pharmacogenomic study confirmed that genetic factors can predispose an individual to SCARs. Genetic markers enable not only elucidation of the pathogenesis of SCARs, but also screening of susceptible subjects. The human leukocyte antigen (HLA) genotypes associated with SCARs include HLA-B*57:01 for abacavir (Caucasians), HLA-B*58:01 for allopurinol (Asians), HLA-B*15:02 (Han Chinese) and HLA-A*31:01 (Europeans and Koreans) for carbamazepine, HLA-B*59:01 for methazolamide (Koreans and Japanese), and HLA-B*13:01 for dapsone (Asians). Therefore, prescreening genetic testing could prevent severe drug hypersensitivity reactions. Large-scale epidemiologic studies are required to demonstrate the usefulness and cost-effectiveness of screening tests because their efficacy is affected by the genetic differences among ethnicities.

HLA Pharmacogenetic Markers of Drug Hypersensitivity in a Thai Population

Severe cutaneous adverse drug reactions (SCARs) including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reactions with eosinophilia and systemic symptoms (DRESS) are potentially life-threatening cutaneous reactions caused by several drugs. Recently, a number of genes encoding for human antigen presenting proteins, HLA alleles, have been discovered as valid pharmacogenetic markers for prediction of these life-threatening reactions. This study was aimed to determine the distribution of HLA alleles including the HLA class I and class II genes in 183 unrelated individuals of a Thai population using high resolution HLA genotyping in order to obtain 2-field data (4-digit resolution) and compare the frequencies of the HLA alleles that have been proposed as markers of SCARs with other ethnics. Results revealed a high prevalence of pharmacogenetic markers of drug-induced SCARs e.g., B^*13:01 for dapsone; B^*15:02 for carbamazepine and oxcarbazepine; B^*58:01, A^*33:03 and C^*03:02 for allopurinol; C^*08:01, C^*14:02 and DRB1^*12:02 for co-trimoxazole. Whereas, low prevalence of pharmacogenetic markers of SCARs induced by abacavir, B^*57:01 and phenytoin, B^*56:02/B^*56:04 were noticed. The allele frequencies of B^*13:01, B^*15:02, and B^*58:01 observed in a Thai population were significantly higher than those reported in Japanese and Caucasian populations. Similar to those observed in other Southeast Asian populations, low frequencies of A^*31:01 and B^*57:01 alleles were noted in the study population. Based on the frequencies of HLA pharmacogenetic markers, Thai and other Southeast Asian populations may at higher risk of drug-induced SCARs compared with Caucasian population.

An Updated Review of the Molecular Mechanisms in Drug Hypersensitivity

Drug hypersensitivity may manifest ranging from milder skin reactions (e.g., maculopapular exanthema and urticaria) to severe systemic reactions, such as anaphylaxis, drug reactions with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS), or Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN). Current pharmacogenomic studies have made important strides in the prevention of some drug hypersensitivity through the identification of relevant genetic variants, particularly for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). The associations identified by these studies are usually drug, phenotype, and ethnic specific. The drug presentation models that explain how small drug antigens might interact with HLA and T cell receptor (TCR) molecules in drug hypersensitivity include the hapten theory, the p-i concept, the altered peptide repertoire model, and the altered TCR repertoire model. The broad spectrum of clinical manifestations of drug hypersensitivity involving different drugs, as well as the various pathomechanisms involved, makes the diagnosis and management of it more challenging. This review highlights recent advances in our understanding of the predisposing factors, immune mechanisms, pathogenesis, diagnostic tools, and therapeutic approaches for drug hypersensitivity.

Nevirapine-induced liver lipid-SER inclusions and other ultrastructural aberrations

Nevirapine (NVP) therapy is associated with a high risk of serious liver injury and skin rash. Treatment of Brown Norway rats with NVP causes an immune-mediated skin rash. Even though NVP does not cause serious liver injury in wildtype animals, incubation of hepatocytes with NVP leads to the release of presumably danger-associated molecular pattern molecules (DAMPs), which activate macrophages. In this study, we examined the liver biopsies of Brown Norway rats treated with NVP to determine the histologic correlate to the release of DAMPs by hepatocytes. In vivo, debris from necrotic hepatocytes and endothelial cells were present in the liver sinusoids, a condition that can trigger an immune response. In addition to mitochondrial, hepatocytic, and endothelial damage, the drug induced large hepatocytic inclusions composed of lipid droplets surrounded by concentric whorls of smooth endoplasmic reticulum (SER) cisternae-lipid-SER (LSER) inclusions, which were deposited in the sinusoids. NVP is lipid soluble, and these LSER inclusions may be sinks of NVP or its metabolites. LSERs are deposited in the blood stream where they may be picked up by lymph nodes and contribute to initiation of an immune response leading to serious liver injury or skin rash. LSERs migration from liver to the blood stream may signify a novel mechanism of drug exocytosis.

HLAs: Key regulators of T-cell-mediated drug hypersensitivity

Adverse drug reactions (ADR) can be broadly categorised as either on-target or off-target. On-target ADRs arise as a direct consequence of the pharmacological properties of the drug and are therefore predictable and dose-dependent. On-target ADRs comprise the majority (>80%) of ADRs, relate to the drug's interaction with its known pharmacological target and are a result of a complex interplay of genetic and ecologic factors. In contrast, off-target ADRs, including immune-mediated ADRs (IM-ADRs), are due to unintended pharmacological interactions such as inadvertent ligation of host cell receptors or non-pharmacological interactions mediated through an adaptive immune response. IM-ADRs can be classified according to the primary immune cell involved and include B-cell-mediated (Gell-Coombs type I-III reactions) and T-cell-mediated (Gell-Coombs type IV or delayed hypersensitivity) reactions. IM-ADRs mediated by T cells are associated with phenotypically distinct clinical diagnoses and can vary from a mild delayed rash to a life-threatening cutaneous, systemic or organ disease, such as Stephen Johnson syndrome/toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms and drug-induced liver disease. T-cell-mediated ADRs are strongly linked to the carriage of particular HLA risk alleles which are in the case of abacavir hypersensitivity and HLA-B*57:01 has led to translation into the clinic as a routine screening test. In this review, we will discuss the immunogenetics and pathogenesis of IM-ADRs and how HLA associations inform both pre-drug screening strategies and mechanistic understanding.

Severe Delayed Drug Reactions: Role of Genetics and Viral Infections

Adverse drug reactions (ADRs) are a significant source of patient morbidity and mortality and represent a major burden to health care systems and drug development. Up to 50% of such reactions are preventable. Although many ADRs can be predicted based on the on-target pharmacologic activity, ADRs arising from drug interactions with off-target receptors are recognized. Off-target ADRs include the immune-mediated ADRs (IM-ADRs) and pharmacologic drug effects. In this review, we discuss what is known about the immunogenetics and pathogenesis of IM-ADRs and the hypothesized role of heterologous immunity in the development of IM-ADRs.

Genome-wide association study of nevirapine hypersensitivity in a sub-Saharan African HIV-infected population

Background

The antiretroviral nevirapine is associated with hypersensitivity reactions in 6%-10% of patients, including hepatotoxicity, maculopapular exanthema, Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).

Objectives

To undertake a genome-wide association study (GWAS) to identify genetic predisposing factors for the different clinical phenotypes associated with nevirapine hypersensitivity.

Methods

A GWAS was undertaken in a discovery cohort of 151 nevirapine-hypersensitive and 182 tolerant, HIV-infected Malawian adults. Replication of signals was determined in a cohort of 116 cases and 68 controls obtained from Malawi, Uganda and Mozambique. Interaction with ERAP genes was determined in patients positive for HLA-C*04:01 . In silico docking studies were also performed for HLA-C*04:01 .

Results

Fifteen SNPs demonstrated nominal significance ( P  <   1 × 10 -5 ) with one or more of the hypersensitivity phenotypes. The most promising signal was seen in SJS/TEN, where rs5010528 ( HLA-C locus) approached genome-wide significance ( P  <   8.5 × 10 -8 ) and was below HLA -wide significance ( P  <   2.5 × 10 -4 ) in the meta-analysis of discovery and replication cohorts [OR 4.84 (95% CI 2.71-8.61)]. rs5010528 is a strong proxy for HLA-C*04:01 carriage: in silico docking showed that two residues (33 and 123) in the B pocket were the most likely nevirapine interactors. There was no interaction between HLA-C*04:01 and ERAP1 , but there is a potential protective effect with ERAP2 [ P  =   0.019, OR 0.43 (95% CI 0.21-0.87)].

Conclusions

HLA-C*04:01 predisposes to nevirapine-induced SJS/TEN in sub-Saharan Africans, but not to other hypersensitivity phenotypes. This is likely to be mediated via binding to the B pocket of the HLA-C peptide. Whether this risk is modulated by ERAP2 variants requires further study.

Shared peptide binding of HLA Class I and II alleles associate with cutaneous nevirapine hypersensitivity and identify novel risk alleles

Genes of the human leukocyte antigen (HLA) system encode cell-surface proteins involved in regulation of immune responses, and the way drugs interact with the HLA peptide binding groove is important in the immunopathogenesis of T-cell mediated drug hypersensitivity syndromes. Nevirapine (NVP), is an HIV-1 antiretroviral with treatment-limiting hypersensitivity reactions (HSRs) associated with multiple class I and II HLA alleles. Here we utilize a novel analytical approach to explore these multi-allelic associations by systematically examining HLA molecules for similarities in peptide binding specificities and binding pocket structure. We demonstrate that primary predisposition to cutaneous NVP HSR, seen across ancestral groups, can be attributed to a cluster of HLA-C alleles sharing a common binding groove F pocket with HLA-C*04:01. An independent association with a group of class II alleles which share the HLA-DRB1-P4 pocket is also observed. In contrast, NVP HSR protection is afforded by a cluster of HLA-B alleles defined by a characteristic peptide binding groove B pocket. The results suggest drug-specific interactions within the antigen binding cleft can be shared across HLA molecules with similar binding pockets. We thereby provide an explanation for multiple HLA associations with cutaneous NVP HSR and advance insight into its pathogenic mechanisms.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): An Interplay among Drugs, Viruses, and Immune System

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a severe multiorgan hypersensitivity reaction mostly caused by a limited number of eliciting drugs in patients with a genetic predisposition. Patients with DRESS syndrome present with characteristic but variable clinical and pathological features. Reactivation of human herpesviruses (HHV), especially HHV-6, is the hallmark of the disease. Anti-viral immune responses intertwined with drug hypersensitivity make the disease more complicated and protracted. In recent years, emerging studies have outlined the disease more clearly, though several important questions remain unresolved. In this review, we provide an overview of DRESS syndrome, including clinical presentations, histopathological features, pathomechanisms, and treatments.

Pharmacogenomic Advances in the Prediction and Prevention of Cutaneous Idiosyncratic Drug Reactions

Cutaneous idiosyncratic drug reactions (CIDRs) are usually unpredictable, ranging from mild maculopapular exanthema (MPE) to severe cutaneous adverse drug reactions (SCARs) such as drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). Increasing evidence suggests that HLA alleles are strongly associated with drug-induced-CIDRs. The pathomechanisms for CIDRs include genetic polymorphisms affecting complex immune-specific HLA/drug antigen/T-cell receptor interactions and drug metabolism. Pharmacogenomic tests to prevent CIDRs have been widely implemented in clinical practice in recent years.

Pharmacogenomics in Asia: a systematic review on current trends and novel discoveries

While early pharmacogenomic studies have primarily been carried out in Western populations, there has been a notable increase in the number of Asian studies over the past decade. We systematically reviewed all pharmacogenomic studies conducted in Asia published before 2016 to highlight trends and identify research gaps in Asia. We observed that pharmacogenomic research in Asia was dominated by larger developed countries, notably Japan and Korea, and mainly driven by local researchers. Studies were focused on drugs acting on the CNS, chemotherapeutics and anticoagulants. Significantly, several novel pharmacogenomic associations have emerged from Asian studies. These developments are highly encouraging for the strength of regional scientific and clinical community and propound the importance of discovery studies in different populations.

An update on HLA alleles associated with adverse drug reactions

Adverse drug reactions (ADRs) are considered as an important cause of morbidity and mortality. The hypersensitivity reactions are immune-mediated ADRs, which are dose-independent, unpredictable and have been associated with several HLA alleles. The present review aimed to describe HLA alleles that have been associated with different ADRs in populations worldwide, the recommendations of regulatory agencies and pharmacoeconomic information and databases for the study of HLA alleles in pharmacogenetics. A systematic search was performed in June 2016 of articles relevant to this issue in indexed journals and in scientific databases (PubMed and PharmGKB). The information of 95 association studies found was summarized. Several HLA alleles and haplotypes have been associated with ADRs induced mainly by carbamazepine, allopurinol, abacavir and nevirapine, among other drugs. Years with the highest numbers of publications were 2013 and 2014. The majority of the reports have been performed on Asians and Caucasians, and carbamazepine was the most studied ADR drug inducer. Two HLA alleles' databases are described, as well as the recommendations of the U.S. Food and Drug Administration, the European Medicine Agency and the Clinical Pharmacogenetics Implementation Consortium. Pharmacoeconomic studies on this issue are also mentioned. The strongest associations remain for HLA-B*58:01, HLA-B*57:01, HLA-B*15:02 and HLA-A*31:01 but only in certain populations; therefore, studies on different ethnic groups would be useful. Due to the improvement of drug therapy and the economic benefit that HLA screening represents, investigations on HLA alleles associated with ADR should continue.

Pharmacogenomics of off-target adverse drug reactions

Off-target adverse drug reactions (ADRs) are associated with significant morbidity and costs to the healthcare system, and their occurrence is not predictable based on the known pharmacological action of the drug's therapeutic effect. Off-target ADRs may or may not be associated with immunological memory, although they can manifest with a variety of shared clinical features, including maculopapular exanthema, severe cutaneous adverse reactions (SCARs), angioedema, pruritus and bronchospasm. Discovery of specific genes associated with a particular ADR phenotype is a foundational component of clinical translation into screening programmes for their prevention. In this review, genetic associations of off-target drug-induced ADRs that have a clinical phenotype suggestive of an immunologically mediated process and their mechanisms are highlighted. A significant proportion of these reactions lack immunological memory and current data are informative for these ADRs with regard to disease pathophysiology, therapeutic targets and biomarkers which may identify patients at greatest risk. Although many serious delayed immune-mediated (IM)-ADRs show strong human leukocyte antigen associations, only a small subset have successfully been implemented in screening programmes. More recently, other factors, such as drug metabolism, have been shown to contribute to the risk of the IM-ADR. In the future, pharmacogenomic targets and an understanding of how they interact with drugs to cause ADRs will be applied to drug design and preclinical testing, and this will allow selection of optimal therapy to improve patient safety.

Multicenter study of skin rashes and hepatotoxicity in antiretroviral-naïve HIV-positive patients receiving non-nucleoside reverse-transcriptase inhibitor plus nucleoside reverse-transcriptase inhibitors in Taiwan

OBJECTIVES

Two nucleos(t)ide reverse-transcriptase inhibitors (NRTIs) plus 1 non-NRTI (nNRTI) remain the preferred or alternative combination antiretroviral therapy (cART) for antiretroviral-naive HIV-positive patients in Taiwan. The three most commonly used nNRTIs are nevirapine (NVP), efavirenz (EFV) and rilpivirine (RPV). This study aimed to determine the incidences of hepatotoxicity and skin rashes within 4 weeks of initiation of cART containing 1 nNRTI plus 2 NRTIs.

METHODS

Between June, 2012 and November, 2015, all antiretroviral-naive HIV-positive adult patients initiating nNRTI-containing cART at 8 designated hospitals for HIV care were included in this retrospective observational study. According to the national HIV treatment guidelines, patients were assessed at baseline, 2 and 4 weeks of cART initiation, and subsequently every 8 to 12 weeks. Plasma HIV RNA load, CD4 cell count and aminotransferases were determined. The toxicity grading scale of the Division of AIDS (DAIDS) 2014 was used for reporting clinical and laboratory adverse events.

RESULTS

During the 3.5-year study period, 2,341 patients initiated nNRTI-containing cART: NVP in 629 patients, EFV 1,363 patients, and RPV 349 patients. Rash of any grade occurred in 14.1% (n = 331) of the patients. In multiple logistic regression analysis, baseline CD4 cell counts (per 100-cell/μl increase, adjusted odds ratio [AOR], 1.125; 95% confidence interval [95% CI], 1.031-1.228) and use of NVP (AOR, 2.443; 95% CI, 1.816-3.286) (compared with efavirenz) were independently associated with the development of skin rashes. Among the 1,455 patients (62.2%) with aminotransferase data both at baseline and week 4, 72 (4.9%) developed grade 2 or greater hepatotoxicity. In multiple logistic regression analysis, presence of antibody for hepatitis C virus (HCV) (AOR, 2.865; 95% CI, 1.439-5.704) or hepatitis B surface antigen (AOR, 2.397; 95% CI, 1.150-4.997), and development of skin rashes (AOR, 2.811; 95% CI, 1.051-7.521) were independently associated with the development of hepatotoxicity.

CONCLUSIONS

The baseline CD4 cell counts and use of NVP were associated with increased risk of skin rashes, while hepatotoxicity was independently associated with HCV or hepatitis B virus coinfection, and development of skin rashes in antiretroviral-naïve HIV-positive Taiwanese patients within 4 weeks of initiation of nNRTI-containing regimens.

The HLA-A*31:01 allele: influence on carbamazepine treatment

Carbamazepine (CBZ) is an effective anticonvulsant that can sometimes cause hypersensitivity reactions that vary in frequency and severity. Strong associations have been reported between specific human leukocyte antigen (HLA) alleles and susceptibility to CBZ hypersensitivity reactions. Screening for HLA-B*15:02 is mandated in patients from South East Asia because of a strong association with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). HLA-A*31:01 predisposes to multiple phenotypes of CBZ hypersensitivity including maculopapular exanthema, hypersensitivity syndrome, and SJS/TEN in a range of populations including Europeans, Japanese, South Koreans and Han Chinese, although the effect size varies between the different phenotypes and populations. Between 47 Caucasians and 67 Japanese patients would need to be tested for HLA-A*31:01 in order to avoid a single case of CBZ hypersensitivity. A cost-effectiveness study has demonstrated that HLA-A*31:01 screening would be cost-effective. Patient preference assessment has also revealed that patients prefer pharmacogenetic screening and prescription of alternative anticonvulsants compared to current standard of practice without pharmacogenetic testing. For patients who test positive for HLA-A*31:01, alternative treatments are available. When alternatives have failed or are unavailable, HLA-A*31:01 testing can alert clinicians to 1) patients who are at increased risk of CBZ hypersensitivity who can then be targeted for more intensive monitoring and 2) increase diagnostic certainty in cases where hypersensitivity has already occurred, so patients can be advised to avoid structurally related drugs in the future. On the basis of the current evidence, we would favor screening all patients for HLA-A*31:01 and HLA-B*15:02 prior to starting CBZ therapy.