HLA-B∗ 1502 is associated with carbamazepine induced Stevens-Johnson syndrome in North Indian population

Unraveling the genetic link: an umbrella review on HLA-B*15:02 and antiepileptic drug-induced Stevens-Johnson syndrome/toxic epidermal necrolysis

PURPOSE

This umbrella review was conducted to summarize the association between HLA*1502 allele with antiepileptic induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).

METHODS

Pubmed, Scopus and EMBASE were searched for eligible reviews in May 2023. Two authors independently screened titles and abstracts and assessed full-text reviews for eligibility. The quality of meta-analyses and case-control studies was appraised with Assessing the Methodological Quality of Systematic Reviews 2 and Newcastle-Ottawa Scale, respectively. Narrative summaries of each antiepileptic drug were analyzed. Preestablished protocol was registered on the International Prospective Register of Systematic Reviews Registry(ID: CRD42023403957).

RESULTS

Included studies are systematic reviews, meta-analyses and case-control studies evaluating the association of HLA-B*1502 allele with the following antiepileptics. Seven meta-analyses for carbamazepine, three meta-analyses for lamotrigine (LTG), three case-control studies for oxcarbazepine, nine case-control studies for phenytoin and four case-control studies for phenobarbitone were included. The findings of this umbrella review suggest that there is a strong association between HLA-B-1502 with SJS/TEN for carbamazepine and oxcarbazepine and a milder association for lamotrigine and phenytoin.

CONCLUSION

In summary, although HLA-B*1502 is less likely to be associated with phenytoin or lamotrigine-induced SJS/TEN compared to carbamazepine-induced SJS/TEN, it is a significant risk factor that if carefully screened, could potentially reduce the development of SJS/TEN. In view of potential morbidity and mortality, HLA-B*1502 testing may be beneficial in patients who are initiating lamotrigine/phenytoin therapy. However, further studies are required to examine the association of other alleles with the development of SJS/TEN and to explore the possibility of genome-wide association studies before initiation of treatment.

Update on HLA-B*15:02 allele associated with adverse drug reactions

HLA alleles, part of the major histocompatibility complex, are strongly associated with adverse drug reactions (ADRs). This review focuses on HLA-B*15:02 and explores its association with ADRs in various ethnic populations and with different drugs, aiming to provide insights into the safe clinical use of drugs and minimize the occurrence of ADRs. Furthermore, the review explores the potential mechanisms by which HLA-B*15:02 may be associated with ADRs, aiming to gain new insights into drug modification and identification of haptens. In addition, it analyzes the frequency of the HLA-B*15:02, genotyping methods, cost-effectiveness and treatment measures for adverse reactions, thereby providing a theoretical basis for formulating clinical treatment plans.

Accurate identification of HLA-B*15:02 allele by two-dimensional polymerase chain reaction

BACKGROUND

HLA-B*15:02 is highly associated with carbamazepine-induced SJS/TEN; however, there is no rapid and accurate detecting method. Here, we present a method to distinguish HLA-B*15:02 from 16 highly homologous HLA-B*15 alleles.

METHODS

The high-throughput two-dimensional polymerase chain reaction (2D-PCR) technology was employed to identify HLA-B*15:02 in two-tube reaction. And, 2D-PCR accuracy was verified by PCR-sequence based typing (PCR-SBT).

RESULTS

HLA-B*15:02 heterozygotes were identified by 14 melting valleys in the first tube reaction and none in the second, or by 13 melting valleys in the first tube reaction and one in the second. HLA-B*15:02 homozygote was identified by 13 melting valleys in the first tube reaction and none in the second. Three (0.16%) HLA-B*15:02 homozygotes and 84 (4.59%) HLA-B*15:02 heterozygotes were detected in 1830 samples of clinical general population without detecting 16 highly homologous alleles to HLA-B*15:02. The kappa test showed 100% coincidence between the 2D-PCR and PCR-SBT.

CONCLUSIONS

2D-PCR in two-tube reaction method for identifying HLA-B*15:02 was successfully established. Identification of HLA-B*15:02 is necessary prior to taking CBZ based on HLA-B*15:02 allele frequency.

Association of Human Leukocyte Antigen Alleles with Carbamazepine- or Lamotrigine-Induced Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis in an Iranian Population: A Case-control Study

Background

Genetic diversity in human leukocyte antigen (HLA) alleles across populations is a significant risk factor for drug-induced severe cutaneous adverse reactions (SCARs), e.g., carbamazepine (CBZ)- and lamotrigine (LTG)-induced Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). The present study aimed to investigate the frequency of different HLA alleles in Iranian patients with CBZ- and LTG-induced SJS/TEN.

Methods

A case-control study was conducted from 2011 to 2018 at various hospitals affiliated with Shiraz University of Medical Sciences (Shiraz, Iran). A total of 31 patients receiving anticonvulsant drugs (CZB or LTG) were recruited and divided into two groups. The drug-induced group (n=14) included hospitalized patients due to CBZ- or LTG-induced SJS/TEN. The drug-tolerant group (n=17) included individuals receiving CBZ or LTG for at least three months with no adverse effects. In addition, 46 healthy individuals (control group) were recruited. The frequency of HLA-A, -B, and -DRB1 alleles in patients with CZB- or LTG-induced SJS/TEN was investigated. HLA typing was performed using the allele-specific polymerase chain reaction method. The Chi square test and Fisher's exact test were used to determine a potential association between SJS/TEN and HLA alleles. P<0.05 was considered statistically significant.

Results

CBZ- or LTG-induced SJS/TEN was not significantly associated with HLA alleles. However, HLA-DRB1*01 showed a significantly higher frequency in patients with CBZ-induced SJS/TEN than the CBZ-tolerant patients (30% vs. 9%, P=0.07).

Conclusion

Overall, no significant association was found between CBZ- or LTG-induced SJS/TEN and HLA alleles. Further large-scale studies are required to substantiate our findings.

Genotyping for HLA risk alleles versus patch tests to diagnose anti-seizure medication induced cutaneous adverse drug reactions

Aim: To provide a comparison of genotyping for HLA risk alleles versus patch testing to determine which of these two tests is a better diagnostic tool for cutaneous hypersensitivity reactions caused by anti-seizure medication.

Methods: A literature study was performed in PubMed to assess the sensitivity and specificity of HLA genotyping and patch tests for identifying anti-seizure medication induced cutaneous hypersensitivity reactions.

Results: This study shows that HLA-B*15:02 genotyping shows high sensitivity for carbamazepine-induced SJS/TEN, especially in Han Chinese and Southeast Asian patients (66.7–100.0%) whereas the sensitivity of patch tests (0.0–62,5%), HLA-A*31:01 (0–50%) and HLA-B*15:11 (18.2–42.9%) are lower. On the contrary, for carbamazepine and phenytoin induced DRESS, patch tests (respectively 70.0–88.9% and 14.3–70.0%) show higher sensitivity than HLA tests (0–66.7% and 0–12.7%). Also for lamotrigine-induced DRESS patch tests perform better than HLA-B*15:02 (33.3–40.0 versus 0%). For anti-seizure medication induced MPE and for oxcarbazepine-induced SCARs more studies are needed.

Conclusion: Use of HLA-B genotyping may aid clinicians in the diagnosis of carbamazepine, phenytoin, lamotrigine and oxcarbazepine induced SJS/TEN, particularly in Han Chinese and Southeast Asian patients. On the other hand, patch tests seem to perform better in the diagnosis of carbamazepine and phenytoin induced DRESS.

HLA pharmacogenetic markers of drug hypersensitivity from the perspective of the populations of the Greater Middle East

Specific HLA associations with drug hypersensitivity may vary between geographic regions and ethnic groups. There are little to no data related to HLA-drug hypersensitivity on populations who reside in the Greater Middle East (GME), a vast region spanning from Morocco in the west to Pakistan in the east. In this review, the authors intended to summarize the significant HLA alleles associated with hypersensitive drug reactions induced by different drugs, as have been found in different populations, and to summarize the prevalence of these alleles in the specific and diverse populations of the GME. For example, HLA-B*57:01 allele prevalence, associated with abacavir-induced hypersensitivity, ranges from 1% to 3%, and HLA-DPB1*03:01 prevalence, associated with aspirin-induced asthma, ranges from 10% to 14% in the GME population. Studying pharmacogenomic associations in the ethnic groups of the GME may allow the discovery of new associations, confirm ones found with a low evidence rate and enable cost-effectiveness analysis of allele screening before drug use.

Associations of HLA genetic variants with carbamazepine‐induced cutaneous adverse drug reactions: An updated meta‐analysis

Aggregated risk of carbamazepine (CBZ)‐induced cutaneous adverse drug reactions (cADRs) with different HLA variants are unclear and limited in terms of the power of studies. This study aimed to assess the aggregated risk of CBZ‐induced cADRs associated with carrying the following HLA variants: HLA‐B*15:02, HLA‐B*15:11, HLA‐B*15:21, HLA‐B*38:02, HLA‐B*40:01, HLA‐B*46:01, HLA‐B*58:01, HLA‐A*24:02, and HLA‐A*31:01. Literature was searched in different databases following PRISMA guidelines. The outcomes were measured as odds ratio (OR) using RevMan software by a random/fixed effects model, where p < 0.05 was set as statistical significance. In total, 46 case–control studies met the inclusion criteria and were included in this analysis consisting of 1817 cases and 6614 controls. It was found that case‐patients who carried the HLA‐B*15:02 allele were associated with a significantly increased risk of CBZ‐induced Stevens−Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) compared to controls (OR 26.01; 95% CI 15.88–42.60; p < 0.00001). The aggregated risk of cADRs was slightly higher in Asian compared to Caucasian patients (Asians: OR 14.84; 95% CI 8.95–24.61; p < 0.00001; Caucasians: OR 11.65; 95% CI 1.68–80.70; p = 0.01). Further, HLA‐B*15:11, HLA‐B*15:21, or HLA‐A*31:01 allele was also associated with significantly increased risk of CBZ‐induced cADRs (HLA‐B*15:11: OR 6.08; 95% CI 2.28–16.23; p = 0.0003; HLA‐B*15:21: OR 5.37; 95% CI 2.02–14.28; p = 0.0008; HLA‐A*31:01: OR 5.92; 95% CI 4.35–8.05; p < 0.00001). Other HLA variants were not found to have any significant associations with CBZ‐induced cADRs. Strong associations between the HLA‐B*15:02, HLA‐B*15:11, HLA‐B*15:21, or HLA‐A*31:01 allele with CBZ‐induced cADRs have been established in this analysis. Pharmacogenetic testing of particular HLA alleles before initiation of CBZ therapy may be beneficial to patients and may help to eradicate cADRs substantially.

Clinical Aspects of Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis With Severe Ocular Complications in India

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a spectrum of rare, severe immunological blistering skin reactions which are triggered by medication intake or infections. The acute phase is characterized by necrolysis of the skin and desquamation of mucosa, primarily oral and ocular, with significant mortality rates. The chronic phase is characterized by multi-organ sequelae with increased rates of morbidity and reduced quality of life for patients who have survived the acute phase. Since the primary goal in the acute phase is saving the life of the patient, ocular involvement is often missed and a significant proportion of patients present to an ophthalmologist with the chronic ocular sequelae. In India, chronic ocular sequelae and low vision are observed in two-thirds of patients who present in the chronic phase of SJS/TEN. In the chronic phase of ocular involvement, there are definite windows of opportunity which if targeted with specific interventions such as scleral lenses and mucous membrane grafts can help reduce the incidence of corneal blindness and improve the quality of life for patients with SJS/TEN. Over the last decade, several studies from India have advanced the understanding of the natural course of ocular involvement in SJS/TEN and the outcomes of timely interventions in the chronic phase of the disease. We present an overview of the epidemiology of ocular complications of SJS/TEN in India, the specific challenges faced in the management of ocular complications in the acute stage and recent advances in management of the chronic ocular complications of the disease.

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.

Association of HLA-B*51:01, HLA-B*55:01, CYP2C9*3, and Phenytoin-Induced Cutaneous Adverse Drug Reactions in the South Indian Tamil Population

Phenytoin (PHT) is one of the most commonly reported aromatic anti-epileptic drugs (AEDs) to cause cutaneous adverse reactions (CADRs), particularly severe cutaneous adverse reactions (SCARs). Although human leukocyte antigen (HLA)-B*15:02 is associated with PHT-induced Steven Johnson syndrome/toxic epidermal necrosis (SJS/TEN) in East Asians, the association is much weaker than it is reported for carbamazepine (CBZ). In this study, we investigated the association of pharmacogenetic variants of the HLA B gene and CYP2C9*3 with PHT-CADRs in South Indian epileptic patients. This prospective case-controlled study included 25 PHT-induced CADRs, 30 phenytoin-tolerant patients, and 463 (HLA-B) and 82 (CYP2C9*3) normal-controls from previous studies included for the case and normal-control comparison. Six SCARs cases and 19 mild-moderate reactions were observed among the 25 cases. Pooled data analysis was performed for the HLA B*51:01 and PHT-CADRs associations. The Fisher exact test and multivariate binary logistic regression analysis were used to identify the susceptible alleles associated with PHT-CADRs. Multivariate analysis showed that CYP2C9*3 was significantly associated with overall PHT-CADRs (OR = 12.00, 95% CI 2.759–84.87, p = 003). In subgroup analysis, CYP2C9*3 and HLA B*55:01 were found to be associated with PHT-SCARs (OR = 12.45, 95% CI 1.138–136.2, p = 0.003) and PHT-maculopapular exanthema (MPE) (OR = 4.041, 95% CI 1.125–15.67, p = 0.035), respectively. Pooled data analysis has confirmed the association between HLA B*51:01/PHT-SCARs (OR = 6.273, 95% CI 2.24–16.69, p = <0.001) and HLA B*51:01/PHT-overall CADRs (OR = 2.323, 95% CI 1.22–5.899, p = 0.037). In this study, neither the case nor the control groups had any patients with HLA B*15:02. The risk variables for PHT-SCARs, PHT-overall CADRs, and PHT-MPE were found to be HLA B*51:01, CYP2C9*3, and HLA B*55:01, respectively. These alleles were identified as the risk factors for the first time in the South Indian Tamil population for PHT-CADRs. Further investigation is warranted to establish the clinical relevance of these alleles in this population with larger sample size.

Carbamazepine induced toxic epidermal necrolysis and Stevens-Johnson syndrome overlapping during pregnancy in a South-East Asian patient: A case report

Introduction

Toxic Epidermal Necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are rare and severe forms of drug-induced skin reaction. Most frequently involved drugs are noted to be non-steroidal anti-inflammatory agents, antibiotics, and anticonvulsants. These have high morbidity and mortality and counts among dermatological emergencies.

Case presentation

We report an eventful case of a 22-year-old lady who suffered and recovered from carbamazepine-induced SJS/TEN overlapping during her pregnancy. Our patient had a history of epilepsy for which she was under sodium valproate. Switching to carbamazepine due to its low teratogenicity led our patient to this condition. History of prodromal symptoms and exposure to carbamazepine helped in the diagnosis. Carbamazepine abstinence and a multidisciplinary approach in symptomatic management worked very well for the patient.

Clinical discussion

Carbamazepine-induced TES/SJS manifests multisystem effects and requires a multidisciplinary approach for management. The condition itself is life-threatening and in its addition, their sequelae further threaten the life of the patients. Early intervention is the key. Genetically susceptible are thought to be the ones carrying human leukocyte antigen B*15:02 (HLA-B*15:02) allele and it is most prevalent in South-East Asian populations. Screening of this allele before using carbamazepine prevents the incidence of carbamazepine-induced SJS/TEN.

Conclusion

Prodromal symptoms of carbamazepine-induced SJS/TEN constitute flu-like symptoms that should not be missed. Early intervention and multidisciplinary approach prevent secondary infections and complications. Screening for HLA-B*15:02 variant allele and close monitoring of these adverse reactions along with proper counseling to patients goes a long way in preventing the development of this life-threatening condition.

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Carbamazepine-induced cutaneous reaction may present as Stevens-Johnson Syndrome (SJS) or toxic epidermal necrolysis (TEN).

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Carriers of the human leukocyte antigen B*1502 gene are susceptible to developing carbamazepine-induced SJS/TEN.

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Human leukocyte antigen B*1502 gene is most prevalent in South-East Asia.

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SJS/TEN affect multisystem and need a multidisciplinary approach in management.

Review on Databases and Bioinformatic Approaches on Pharmacogenomics of Adverse Drug Reactions

Pharmacogenomics has been used effectively in studying adverse drug reactions by determining the person-specific genetic factors associated with individual response to a drug. Current approaches have revealed the significant importance of sequencing technologies and sequence analysis strategies for interpreting the contribution of genetic variation in developing adverse reactions. Advance in next generation sequencing and platform brings new opportunities in validating the genetic candidates in certain reactions, and could be used to develop the preemptive tests to predict the outcome of the variation in a personal response to a drug. With the highly accumulated available data recently, the in silico approach with data analysis and modeling plays as other important alternatives which significantly support the final decisions in the transformation from research to clinical applications such as diagnosis and treatments for various types of adverse responses.

Genetic Markers for Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis in the Asian Indian Population: Implications on Prevention

This review attempts to collate all the studies performed in India or comprising a population originating from India and to find out if there is an association between the HLA (human leucocyte antigen) type of individual and development of Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) subsequent to medication use. The authors performed a PubMed search of all articles published in English from 2009 to 2019 for articles that studied HLA type in patients who developed SJS/TEN after intake of a specific drug in the Asian Indian population or in individuals of Asian Indian origin. The selection criteria were satisfied by a total of 11 studies that reported HLA associations with specific drugs, which induced SJS/TEN, mainly anti-epileptic drugs, and cold medicine/non-steroidal anti-inflammatory drugs. These studies involved a small number of patients, and hence, there is limited evidence to conclude if these associations can be extrapolated to a larger population of the same ethnicity. Similar multi-center studies need to be conducted with a larger sample size to confirm these associations. This would have implications in policy making and for understanding the potential of using genetic markers as a screening tool before prescribing a drug to a patient, which might make them susceptible to developing a potentially life-threatening disease such as SJS/TEN. This is possibly the only mode of primary prevention for this potentially fatal severe cutaneous adverse drug reaction.

Possible interplay between the theories of pharmacoresistant epilepsy

Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.

Pharmacogenetic Testing for Prevention of Severe Cutaneous Adverse Drug Reactions

Severe cutaneous adverse reactions (SCAR), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug rash with eosinophilia and systemic symptoms (DRESS), are idiosyncratic and unpredictable drug-hypersensitivity reactions with a high-mortality rate ranging from 10% to over 30%, thus causing a major burden on the healthcare system. Recent pharmacogenomic studies have revealed strong associations between SCAR and the genes encoding human-leukocyte antigens (HLAs) or drug-metabolizing enzymes. Some of pharmacogenetic markers have been successfully applied in clinical practice to protect patients from SCAR, such as HLA-B*15:02 and HLA-A*31:01 for new users of carbamazepine, HLA-B*58:01 for allopurinol, and HLA-B*57:01 for abacavir. This article aims to update the current knowledge in the field of pharmacogenomics of drug hypersensitivities or SCAR, and its implementation in the clinical practice.

Diagnostic Utility of Human Leukocyte Antigen B*15:02 Screening in Severe Carbamazepine Hypersensitivity Syndrome

Background

Despite many studies suggesting an association between human leukocyte antigen (HLA)-B*15:02 and carbamazepine (CBZ)-induced severe cutaneous adverse drug reactions essentially toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS), the evidence of association in different populations and the degree of association remain uncertain.

Materials and Methods

The primary analysis was based on population control studies. Data were pooled by means of a random-effects model, and sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-), diagnostic odds ratios (DOR), and areas under the summary receiver operating characteristic curve (AUC) were calculated.

Results

In 23 population control studies, HLA-B*15:02 was measured in 373 patients with CBZ-induced TEN/SJS and 3452 patients without CBZ-induced TEN/SJS. The pooled sensitivity, specificity, LR+, LR-, DOR, and AUC were 0.67 (95% confidence interval [CI] = 0.63-0.72), 0.98 (95% CI = 0.98-0.99), 19.73 (95% CI = 10.54-36.92), 0.34 (95% CI = 0.23-0.49), 71.38 (95% CI = 34.89-146.05), and 0.96 (95% CI = 0.92-0.98), respectively. Subgroup analyses for Han Chinese, Thai, and Malaysian populations yielded similar findings. Specifically, racial/ethnic subgroup analyses revealed similar findings with respect to DOR for Han Chinese (99.28; 95% CI = 22.20-443.88), Thai (61.01; 95% CI = 23.05-161.44), and Malaysian (30; 95% CI = 7.08-126.68) populations, which are similar to the pooled DOR for the relationship between the HLA-B*15:02 allele and CBZ-induced TEN/SJS across all populations (71.38; 95% CI = 34.89-146.05).

Conclusions

The present study reveals that CBZ is the leading cause of TEN/SJS in many countries. Screening of HLA-B*15:02 may help patients to prevent the occurrence of CBZ-induced TEN/SJS, especially in populations with a higher (≥5%) risk allele frequency.

HLA-associated antiepileptic drug-induced cutaneous adverse reactions

Adverse drug reactions (ADRs) are a common cause of hospital admissions (up to 19%), with the majority of cases due to off-target predictable drug effects (type A reactions). However, idiosyncratic drug-induced immune activated (type B) reactions contribute to a range of hypersensitivity reactions, with T-cell-mediated type IV hypersensitivity reactions mainly manifesting as cutaneous ADRs (cADRs). Aromatic antiepileptic drugs (AEDs), used in the treatment of epilepsy as well as bipolar disorder or neuropathic pain, have been implicated as culprit drugs in a spectrum of pathologies ranging from mild maculopapular exanthema (MPE) to severe and life-threatening conditions including drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). These AED-induced cADRs are unpredictable based on pharmacological and clinical factors alone, thereby prompting investigations into genomic contributors mediating risk of pathology. The most strongly associated risk genes identified are from the human leukocyte antigen (HLA) class I alleles, which play a critical role in adaptive immunity by flagging either infected or aberrant cells for recognition by surveying T-cells. In the setting of drug hypersensitivity, the immunogenicity of HLA molecules and their peptide cargo can be modulated by interactions with small drug molecules that drive inappropriate T-cell responses. This review discusses the current understanding of HLA class I molecules in modifying risk of AED-induced cADRs.

Association of cutaneous adverse drug reactions due to antiepileptic drugs with HLA alleles in a North Indian population

PURPOSE

Aromatic antiepileptic drugs (AEDs) are frequently implicated in cutaneous adverse drug reactions (cADRs), a few of which are associated with certain human leukocyte antigen (HLA) alleles in some populations. We aimed to find HLA-associations with AED-related cADRs among North Indians.

METHODS

North Indian subjects with cADR due to an AED, and those who were AED-tolerant were recruited as cases and controls, respectively. Genotyping for HLA-A, B and DRB1 were performed. Statistical analysis to compare carrier-rates and allele-frequencies between cases and controls (and healthy population, where necessary), was done for HLA-alleles occurring more than twice in either group.

RESULTS

120 cases {11 - Lamotrigine (LTG), 14 -Valproic acid (VPA), 8 -Levetiracetam (LEV), 35 -Carbamazepine (CBZ) and 52 - Phenytoin (PHT)}, and 250 controls were recruited. Presence of HLA-A*31:01 and HLA-B*51:01 were found to increase the risk of Maculopapular exanthema (MPE) due to CBZ and PHT (OR = 6.38; 95% CI: 1.46-27.75; OR = 4.60; 95% CI: 1.54-13.72, respectively). Among the severe cADRs, HLA-B*57:01(OR = 11.00 95% CI: 1.41-85.81) and HLA-DRB1*07:01 (OR = 7.25; 95% CI: 1.09-48.18) were noted to be significantly associated with CBZ-induced Stevens Johnson Syndrome (SJS)/Toxic Epidermal Necrolysis (TEN); HLA-B *51:01 was associated with drug reaction eosinophilia and systemic symptoms (DRESS) caused by PHT (OR = 6.90; 95% CI: 1.38-34.29).

CONCLUSIONS

We found significant associations of some HLA alleles with specific cADRs to CBZ and PHT in North Indians, which may need to be tested before AED-initiation; only screening for HLA-B*15:02 may not help in this population.

High-risk drug rashes

OBJECTIVE

To provide a brief overview of the clinical presentation, common offending agents, management, prognosis, and mortality of 6 selected high-risk drug rashes, namely, Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, multiple drug hypersensitivity (MDH) syndrome, acute generalized exanthematous pustulosis (AGEP), and drug-induced bullous pemphigoid (DIBP).

DATA SOURCES

A review of the published literature was performed with PubMed and supplemented with our clinical experience.

STUDY SELECTIONS

The most recent clinically relevant studies and older seminal works were selected.

RESULTS

Most of the published data on these uncommon rashes were based on small observational series or case reports. SJS and TEN have specific genotypes association with certain drugs, have high morbidity and mortality, and require aggressive management by a team of multiple specialists. DRESS syndrome is a severe, prolonged multiorgan reaction, yet it has a better prognosis than TEN. MDH is a syndrome of repeated reactions to unrelated drugs that often imposes diagnostic and management difficulties. AGEP consists of generalized sterile small pustules, usually mistaken for infection with subsequent inappropriate treatment. Bullous pemphigoid presents with tense pruritic bullae and characteristic linear basement membrane deposition of IgG and C3. DIBP has much better prognosis than the autoimmune variety.

CONCLUSION

In such high-risk drug rashes, early recognition, immediate withdrawal of the suspected drug(s), prompt individualized management, and monitoring of vital organs function are mandatory for reducing morbidity and mortality. The lack of reliable tests for identification of the causative agent imposes difficulty, particularly in patients receiving multiple medications.

HLA Association with Drug-Induced Adverse Reactions

Adverse drug reactions (ADRs) remain a common and major problem in healthcare. Severe cutaneous adverse drug reactions (SCARs), such as Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) with mortality rate ranges from 10% to more than 30%, can be life threatening. A number of recent studies demonstrated that ADRs possess strong genetic predisposition. ADRs induced by several drugs have been shown to have significant associations with specific alleles of human leukocyte antigen (HLA) genes. For example, hypersensitivity to abacavir, a drug used for treating of human immunodeficiency virus (HIV) infection, has been proposed to be associated with allele 57:01 of HLA-B gene (terms HLA-B^∗57:01). The incidences of abacavir hypersensitivity are much higher in Caucasians compared to other populations due to various allele frequencies in different ethnic populations. The antithyroid drug- (ATDs- ) induced agranulocytosis are strongly associated with two alleles: HLA-B^∗38:02 and HLA-DRB1^∗08:03. In addition, HLA-B^∗15:02 allele was reported to be related to carbamazepine-induced SJS/TEN, and HLA-B^∗57:01 in abacavir hypersensitivity and flucloxacillin induced drug-induced liver injury (DILI). In this review, we summarized the alleles of HLA genes which have been proposed to have association with ADRs caused by different drugs.

Antiepilepsy drugs and the immune system

OBJECTIVE

To alert physicians about the peculiar adverse effects of antiepilepsy drugs (AEDs) on the immune system.

DATA SOURCES

PubMed literature during the past 25 years.

STUDY SELECTIONS

Reports and review articles on the hypersensitivities of AEDs and their effect on immunity.

RESULTS

AEDs have significant effects on the immune system in the form of hypersensitivity or immune suppression. IgE-mediated reactions can be urticaria, angioedema, bronchospasm, or anaphylaxis. Non-IgE-mediated reactions, more commonly associated with aromatic AEDs, can be in the form of nonspecific rashes or serious reactions, such as Stevens-Johnson syndrome, toxic epidermal necrolysis, drug rash with eosinophilia and systemic symptom syndrome, and acute generalized exanthematous pustulosis. Because of strong genetic predispositions for certain AEDs in causing severe reactions, HLA analysis before initiation of the drug is advised in certain populations. Immunoglobulin levels can be reduced to various degrees, particularly by carbamazepine, valproate, phenytoin, levetiracetam, zonisamide, and lamotrigine. Spontaneous return to normal levels can be rapid or take months to a few years, and intravenous immunoglobulin supplementation may be needed. Cellular effects can be in the form of cytopenias, inhibition of lymphocyte function, or cytokine dysregulation.

CONCLUSION

When prescribing AEDs, physicians should pay special attention to their potential adverse effects on immunity or hypersensitivity, which can be severe and even fatal. For early recognition and intervention, monitoring such patients is necessary. The cornerstone of management is discontinued use of the suspected medication and avoidance of drugs of similar structure, particularly among members of the aromatic group.

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.

External quality assessment for laboratory testing of HLA-B*15:02 allele in relation to carbamazepine therapy

BACKGROUND

Due to the significant risk of developing Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), the use of carbamazepine is not recommended in patients carrying the human leukocyte antigen B (HLA-B) *15:02 allele. In an effort to guarantee reliable community-based HLA-B*15:02 testing throughout China, a HLA-B*15:02 genotyping external quality assessment (EQA) program was set up.

METHODS

In 2016, 10 genomic DNA samples with known HLA-B*15:02 allele status were sent to 37 laboratories from 16 provinces with a request for routine HLA-B*15:02 screening. The samples were validated using Sanger sequencing by a reference laboratory. Both genotyping results and clinical written reports were evaluated.

RESULTS

Thirty-six of the participating laboratories correctly identified the HLA-B*15:02 allele status for all EQA samples. However, one lab failed to identify any positive challenges. The overall analytical sensitivity was 97.3% (180/185 challenges; 95% confidence interval: 93.8%-99.1%) and the analytic specificity was 100% (185/185; 95% confidence interval: 98.0%-100%). A review of the written reports showed that the clinical reporting for HLA-B*15:02 detection should be improved. Some essential information was missing, most notably laboratory information/contact, therapeutic recommendations, and methodology.

CONCLUSION

External quality assessment is valuable in assessing and improving the quality of laboratory testing of HLA-B*15:02 allele.

Spectrum of Cutaneous Adverse Reactions to Levetiracetam and Human Leukocyte Antigen Typing in North-Indian Patients

Background and Purpose

Aromatic antiepileptic drugs are frequently implicated for cutaneous adverse drug reactions (cADRs); there are case-reports of even severe reactions like drug reaction eosinophilia and systemic symptoms (DRESS) and Stevens Johnson syndrome (SJS)-toxic epidermal necrolysis with Levetiracetam (LEV). Certain human leukocyte antigen (HLA)-alleles have strong association with cADRs due to specific drugs - HLA-B*15:02 and HLA-A*31:01 in Carbamazepine (CBZ)-related SJS in Han-Chinese and European populations, respectively. Here, the spectrum of cADRs to LEV was studied, and HLA-typing in patients with cADRs due to LEV and some who were LEV-tolerant was performed, in an attempt to find an association between HLA and such reactions.

Methods

589 patients taking LEV were screened for skin reactions, and eight patients with LEV-related cADRs and 25 LEV-tolerant controls were recruited - all 33 of North Indian ethnicity, their HLA-A, B, DRB1 genotyping done. Statistical analysis was done to compare carrier-rates and allele-frequencies of HLA-alleles between cases and controls (and healthy population, where necessary) for alleles occurring more than two times in either group.

Results

Out of 589 patients on LEV screened, there were 8 cases of cADR: 5 with maculopapular exanthema (MPE), 2 of SJS, and 1 with DRESS. Although HLA-A*33:01 was seen to occur more in MPE cases as compared to tolerant controls, the difference was not statistically significant (odds ratio [OR] 6.00, 95% confidence interval [CI] 0.30–116.6; p = 0.31). HLA A*11:01 and 24:02 were found to occur more in LEV-tolerant controls than in cases (OR 0.23 [95% CI 0.02–2.36, p = 0.33] and 1.00 [95% CI 0.09–11.02, p = 1.00] respectively).

Conclusions

Cutaneous reactions to LEV are very unusual, and their association with HLA in North-Indian population was not statistically significant.

A Critical Evaluation of Pharmacogenetic Information in Package Inserts for Selected Drugs Marketed in India and Its Comparison With US FDA-Approved Package Inserts

Our objective was to compare the pharmacogenetic information provided in the package inserts (PIs) of 7 drugs marketed in the United States and India, namely, abacavir, capecitabine, carbamazepine, clopidogrel, irinotecan, valproic acid, and warfarin. We evaluated the pharmacogenetic information provided in Indian PIs for the highest level where it was included, robustness and completeness, clinical validity, and clinical utility and compared it with corresponding data of US PIs. Pharmacogenetic studies carried out in India were identified using PubMed. Pharmacogenetic information was provided in Indian PIs of all the drugs except irinotecan. It appeared in the same section as in US PIs for abacavir, capecitabine, carbamazepine (HLA-*3101), valproic acid (urea cycle disorders), and warfarin (protein C and protein S), whereas it appeared at lower levels for other drug-gene combinations. The robustness of pharmacogenetic testing was graded convincing for abacavir, adequate for carbamazepine and clopidogrel, and incomplete for the remaining drugs, and only abacavir and clopidogrel PIs provided full details of supporting studies. These details, when provided in the Indian PIs were identical to those in the US PIs. The Indian PIs did not provide data on Indian patients, although published studies are available. Both US and Indian PIs lacked critical information on the clinical validity and utility of pharmacogenetic testing. The pharmacogenetic information should provide country/ethnicity-specific data so that they are useful to clinicians. Where data are not available, the prevalence of genetic variation in the population of a country needs to be determined and should then be translated to the PIs.

Systems pharmacological analysis of drugs inducing stevens-johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are serious cutaneous adverse reactions. We mined the approved labels in Drugs@FDA, identified the SJS/TEN list of 259 small molecular drugs and biologics, and conducted systems pharmacological network analyses. Pharmacological network analysis revealed that drugs with treatment-related SJS and/or TEN are pharmacologically diverse and that the largest subnetwork is associated with antiepileptic drugs and their pharmacological targets. Our pharmacological network analysis identified CTNNB1 [catenin (cadherin-associated protein), beta 1, 88 kDa] as a significant intermediator. This protein is involved in maintaining the functional integrity of the epithelium through regulating cell growth and adhesion between cells in various organs, including the skin. Leveraging a publicly accessible genome-wide transcriptional expression database, we found that human leukocyte antigen-related (HLA) genes were significantly perturbed by various SJS/TEN-inducing drugs. Notably, carbamazepine (CBZ) perturbed several HLA genes, among which HLA-DQB1*0201 was reportedly shown to be associated with CBZ-induced SJS/TEN in caucasians. In short, systems analysis by leveraging a publicly accessible knowledge base and databases could produce meaningful results for further mechanistic investigation. Our study sheds light on the utility of systems pharmacology analysis for gaining insight into clinical drug toxicity.