Clinical Profiles of Japanese Patients with Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis Collected by a Nationwide System from 2006 to 2023.

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are potentially life-threatening severe cutaneous adverse drug reactions. These diseases are rare, and their onset is difficult to predict because of their idiosyncratic reactivity. The Japan Severe Adverse Reactions Research Group, led by the National Institute of Health Sciences, has operated a nationwide to collect clinical information and genomic samples from patients with SJS/TEN since 2006. This study evaluated the associations of clinical symptoms with sequelae and specific causative drugs/drug groups in Japanese patients with SJS/TEN to identify clinical clues for SJS/TEN treatment and prognosis. Acetaminophen, antibiotics, and carbocisteine were linked to high frequencies of severe ocular symptoms and ocular sequelae (p < 0.05). For erythema and erosion areas, antipyretic analgesics had higher rates of skin symptom affecting <10% of the skin than the other drugs, suggesting narrower lesions (p < 0.004). Hepatic dysfunction, was common in both SJS and TEN, and antiepileptic drugs carried higher risks of hepatic dysfunction than the other drug groups (p = 0.0032). This study revealed that the clinical manifestations of SJS/TEN vary according to the causative drugs.

Low Levels of Amlodipine in Breast Milk and Plasma.

OBJECTIVE: Few clinical reports have addressed the use of the antihypertensive drug amlodipine during breastfeeding. The objective of this study is to characterize concentration-time profiles of amlodipine in maternal and infant plasma, and milk. MATERIALS AND METHODS: Plasma and breast milk samples were obtained from eight nursing mothers and their nine newborn nursing infants (median postnatal age: 6.5 days, range 5-7 days). Participants were recruited from February 2009 to June 2009. Multiple blood and milk samples were obtained from the mothers over a 24 hours dosing interval. The blood of infants was also obtained at before and 8 hours after nursing. Amlodipine concentrations were determined by high-performance liquid chromatography. Relative infant dose (RID) was calculated by dividing the infant's dose via milk in mg/kg/day by the maternal dose in mg/kg/day, assuming that a daily intake of milk is 150 mL/kg/day in the infants. RESULTS: Maximal amlodipine concentrations in mothers ranged from 4.4 to 14.7 ng/mL in plasma, and 6.5 to 19.7 ng/mL in milk (Average milk/plasma ratio: 1.4). RID was 3.4% of the maternal weight-adjusted dose. All plasma concentrations in infants were under the quantitation limit (0.4 ng/mL). CONCLUSION: Infant exposure to amlodipine in breast milk appears very small, suggesting that amlodipine can be used with little influence on infants during breastfeeding.

SLCO1B1 Polymorphism Is a Drug Response Predictive Marker for Advanced Pancreatic Cancer Patients Treated With Gemcitabine, S-1, or Gemcitabine Plus S-1.

OBJECTIVES: The aim of this study was to evaluate the effects of single-nucleotide polymorphisms (SNPs) on advanced pancreatic cancer risk and overall survival (OS) in a candidate-gene approach. METHODS: Overall, 5438 SNPs in 219 candidate genes encoding several drug-metabolizing enzymes or transporters were analyzed. In the screening study, 3 SNPs were found associated with OS (P ≤ 0.0005). We validated these SNPs as part of the randomized phase 3 study (GEST study). The associations between OS and SNPs were investigated using log-rank test and Cox proportional hazards model. RESULTS: From the GEST study, the SNP rs4149086 in the 3' UTR of the solute carrier organic anion transporter family member 1B1 (SLCO1B1) gene showed significant interaction with treatment (P = 0.02). In the gemcitabine group, the SNP was associated with short OS (hazard ratio [HR], 3.75; 95% confidence interval [CI], 1.30-10.8; P = 0.008) even after multiple-comparisons adjustment. In contrast, the SNP was not associated with OS in S-1 (HR, 0.77; 95% CI, 0.33-1.81; P = 0.55) or gemcitabine plus S-1 groups (HR, 1.18; 95% CI, 0.46-3.00; P = 0.72). CONCLUSIONS: Patients with advanced pancreatic cancer with the rs4149086 AG or GG genotype may obtain good clinical results when treated with S-1-containing regimens.

Absence of ethnic differences in the pharmacokinetics of moxifloxacin, simvastatin, and meloxicam among three East Asian populations and Caucasians.

AIM: To examine whether strict control of clinical trial conditions could reduce apparent differences of pharmacokinetic (PK) parameters among ethnic groups. METHODS: Open-label, single dose PK studies of moxifloxacin, simvastatin and meloxicam were conducted in healthy male subjects from three East Asian populations (Japanese, Chinese and Koreans) and one Caucasian population as a control. These three drugs were selected because differences in PK parameters have been reported, even though the backgrounds of these East Asian populations are similar. Moxifloxacin (400 mg) was administered orally to 20 subjects, and plasma and urine levels of moxifloxacin and its metabolite (M2) were measured. Simvastatin (20 mg) was given to 40 subjects, and plasma levels of simvastatin and simvastatin acid were measured. Meloxicam (7.5 mg) was given to 30 subjects and its plasma concentration was determined. Intrinsic factors (polymorphism of UGT1A1 for moxifloxacin, SLCO1B1 for simvastatin, and CYP2C9 for meloxicam) were also examined. RESULTS: AUCinf values for moxifloxacin, simvastatin and meloxicam showed no significant differences among the East Asian groups. Cmax values of moxifloxacin and simvastatin, but not meloxicam, showed significant differences. There were no significant differences of data for M2 or simvastatin acid. Genetic analysis identified significant differences in the frequencies of relevant polymorphisms, but these differences did not affect the PK parameters observed. CONCLUSIONS: Although there were some differences in PK parameters among the three East Asian groups, the present study performed under strictly controlled conditions did not reproduce the major ethnic differences observed in previous studies.

Development of a simple genotyping method for the HLA-A*31:01-tagging SNP in Japanese.

AIM: To construct a simple, low-cost typing method for the surrogate marker of HLA-A*31:01, a risk factor for carbamazepine (CBZ) related Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). MATERIALS & METHODS: DNAs from Japanese SJS/TEN patients were used for genotyping and developing the assay. RESULTS: HLA-A*31:01 was confirmed to be significantly associated with definite/probable cases of CBZ-related SJS/TEN (p = 0.0040). Three single nucleotide polymorphisms, rs1150738, rs3869066 and rs259945, were in absolute linkage disequilibrium with HLA-A*31:01 in 210 Japanese SJS/TEN patients. Robust genotyping of rs3869066 in ZNRD1-AS1 was developed using polymerase chain reaction-restriction fragment length polymorphism assays. CONCLUSION: Single nucleotide polymorphism genotyping is less time consuming and cheaper than conventional HLA typing, and would be useful for identifying Japanese patients at risk of CBZ-related SJS/TEN.

Construction of possible integrated predictive index based on EGFR and ANXA3 polymorphisms for chemotherapy response in fluoropyrimidine-treated Japanese gastric cancer patients using a bioinformatic method.

BACKGROUND: Variability in drug response between individual patients is a serious concern in medicine. To identify single-nucleotide polymorphisms (SNPs) related to drug response variability, many genome-wide association studies have been conducted. METHODS: We previously applied a knowledge-based bioinformatic approach to a pharmacogenomics study in which 119 fluoropyrimidine-treated gastric cancer patients were genotyped at 109,365 SNPs using the Illumina Human-1 BeadChip. We identified the SNP rs2293347 in the human epidermal growth factor receptor (EGFR) gene as a novel genetic factor related to chemotherapeutic response. In the present study, we reanalyzed these hypothesis-free genomic data using extended knowledge. RESULTS: We identified rs2867461 in annexin A3 (ANXA3) gene as another candidate. Using logistic regression, we confirmed that the performance of the rs2867461 + rs2293347 model was superior to those of the single factor models. Furthermore, we propose a novel integrated predictive index (iEA) based on these two polymorphisms in EGFR and ANXA3. The p value for iEA was 1.47 × 10(-8) by Fisher's exact test. Recent studies showed that the mutations in EGFR is associated with high expression of dihydropyrimidine dehydrogenase, which is an inactivating and rate-limiting enzyme for fluoropyrimidine, and suggested that the combination of chemotherapy with fluoropyrimidine and EGFR-targeting agents is effective against EGFR-overexpressing gastric tumors, while ANXA3 overexpression confers resistance to tyrosine kinase inhibitors targeting the EGFR pathway. CONCLUSIONS: These results suggest that the iEA index or a combination of polymorphisms in EGFR and ANXA3 may serve as predictive factors of drug response, and therefore could be useful for optimal selection of chemotherapy regimens.

[Utilization of Genomic Biomarkers for Post-marketing Safety of Drugs].

To prevent adverse drug reactions in the post-marketing phase, therapeutic drug monitoring and various laboratory tests have been used for decades. Recently, data on associations between drug adverse reactions and biomarkers based on "omics" technologies/studies have been increasing. Using genomic biomarkers, patients at high risk for developing side effects can be distinguished before initiating medical treatment, allowing the choice of an appropriate drug/initial dosage regimen. Biomarkers based on proteomics or metabolomics can detect the onset of adverse reactions at an earlier stage than can be accomplished with classical laboratory tests. However, the clinical use of drug safety-related biomarkers is still limited compared with biomarkers that predict drug efficacy of, for example, molecular-targeted drugs. In this symposium, genomic biomarkers associated with the safety of anticancer drugs and idiosyncratic adverse reactions are introduced and compared between Japan and other countries. Prospective studies evaluating the application of screening tests to prevent adverse drug reactions are also shown, and steps necessary to accelerate the use of drug safety-related biomarkers are discussed.

IKZF1, a new susceptibility gene for cold medicine-related Stevens-Johnson syndrome/toxic epidermal necrolysis with severe mucosal involvement.

BACKGROUND: Stevens-Johnson syndrome (SJS) and its severe form, toxic epidermal necrolysis (TEN), are acute inflammatory vesiculobullous reactions of the skin and mucous membranes, including the ocular surface, oral cavity, and genitals. These reactions are very rare but are often associated with inciting drugs, infectious agents, or both. OBJECTIVE: We sought to identify susceptibility loci for cold medicine-related SJS/TEN (CM-SJS/TEN) with severe mucosal involvement (SMI). METHODS: A genome-wide association study was performed in 808 Japanese subjects (117 patients with CM-SJS/TEN with SMI and 691 healthy control subjects), and subsequent replication studies were performed in 204 other Japanese subjects (16 cases and 188 control subjects), 117 Korean subjects (27 cases and 90 control subjects), 76 Indian subjects (20 cases and 56 control subjects), and 174 Brazilian subjects (39 cases and 135 control subjects). RESULTS: In addition to the most significant susceptibility region, HLA-A, we identified IKZF1, which encodes Ikaros, as a novel susceptibility gene (meta-analysis, rs4917014 [G vs. T]; odds ratio, 0.5; P = 8.5 × 10(-11)). Furthermore, quantitative ratios of the IKZF1 alternative splicing isoforms Ik1 and Ik2 were significantly associated with rs4917014 genotypes. CONCLUSION: We identified IKZF1 as a susceptibility gene for CM-SJS/TEN with SMI not only in Japanese subjects but also in Korean and Indian subjects and showed that the Ik2/Ik1 ratio might be influenced by IKZF1 single nucleotide polymorphisms, which were significantly associated with susceptibility to CM-SJS/TEN with SMI.

Genetic variants associated with phenytoin-related severe cutaneous adverse reactions.

IMPORTANCE: The antiepileptic drug phenytoin can cause cutaneous adverse reactions, ranging from maculopapular exanthema to severe cutaneous adverse reactions, which include drug reactions with eosinophilia and systemic symptoms, Stevens-Johnson syndrome, and toxic epidermal necrolysis. The pharmacogenomic basis of phenytoin-related severe cutaneous adverse reactions remains unknown. OBJECTIVE: To investigate the genetic factors associated with phenytoin-related severe cutaneous adverse reactions. DESIGN, SETTING, AND PARTICIPANTS: Case-control study conducted in 2002-2014 among 105 cases with phenytoin-related severe cutaneous adverse reactions (n=61 Stevens-Johnson syndrome/toxic epidermal necrolysis and n=44 drug reactions with eosinophilia and systemic symptoms), 78 cases with maculopapular exanthema, 130 phenytoin-tolerant control participants, and 3655 population controls from Taiwan, Japan, and Malaysia. A genome-wide association study (GWAS), direct sequencing of the associated loci, and replication analysis were conducted using the samples from Taiwan. The initial GWAS included samples of 60 cases with phenytoin-related severe cutaneous adverse reactions and 412 population controls from Taiwan. The results were validated in (1) 30 cases with severe cutaneous adverse reactions and 130 phenytoin-tolerant controls from Taiwan, (2) 9 patients with Stevens-Johnson syndrome/toxic epidermal necrolysis and 2869 population controls from Japan, and (3) 6 cases and 374 population controls from Malaysia. MAIN OUTCOMES AND MEASURES: Specific genetic factors associated with phenytoin-related severe cutaneous adverse reactions. RESULTS: The GWAS discovered a cluster of 16 single-nucleotide polymorphisms in CYP2C genes at 10q23.33 that reached genome-wide significance. Direct sequencing of CYP2C identified missense variant rs1057910 (CYP2C9*3) that showed significant association with phenytoin-related severe cutaneous adverse reactions (odds ratio, 12; 95% CI, 6.6-20; P=1.1 × 10(-17)). The statistically significant association between CYP2C9*3 and phenytoin-related severe cutaneous adverse reactions was observed in additional samples from Taiwan, Japan, and Malaysia. A meta-analysis using the data from the 3 populations showed an overall odds ratio of 11 (95% CI, 6.2-18; z=8.58; P < .00001) for CYP2C9*3 association with phenytoin-related severe cutaneous adverse reactions. Delayed clearance of plasma phenytoin was detected in patients with severe cutaneous adverse reactions, especially CYP2C9*3 carriers, providing a functional link of the associated variants to the disease. CONCLUSIONS AND RELEVANCE: This study identified CYP2C variants, including CYP2C9*3, known to reduce drug clearance, as important genetic factors associated with phenytoin-related severe cutaneous adverse reactions.

Application of a combination of a knowledge-based algorithm and 2-stage screening to hypothesis-free genomic data on irinotecan-treated patients for identification of a candidate single nucleotide polymorphism related to an adverse effect.

Interindividual variation in a drug response among patients is known to cause serious problems in medicine. Genomic information has been proposed as the basis for "personalized" health care. The genome-wide association study (GWAS) is a powerful technique for examining single nucleotide polymorphisms (SNPs) and their relationship with drug response variation; however, when using only GWAS, it often happens that no useful SNPs are identified due to multiple testing problems. Therefore, in a previous study, we proposed a combined method consisting of a knowledge-based algorithm, 2 stages of screening, and a permutation test for identifying SNPs. In the present study, we applied this method to a pharmacogenomics study where 109,365 SNPs were genotyped using Illumina Human-1 BeadChip in 168 cancer patients treated with irinotecan chemotherapy. We identified the SNP rs9351963 in potassium voltage-gated channel subfamily KQT member 5 (KCNQ5) as a candidate factor related to incidence of irinotecan-induced diarrhea. The p value for rs9351963 was 3.31×10-5 in Fisher's exact test and 0.0289 in the permutation test (when multiple testing problems were corrected). Additionally, rs9351963 was clearly superior to the clinical parameters and the model involving rs9351963 showed sensitivity of 77.8% and specificity of 57.6% in the evaluation by means of logistic regression. Recent studies showed that KCNQ4 and KCNQ5 genes encode members of the M channel expressed in gastrointestinal smooth muscle and suggested that these genes are associated with irritable bowel syndrome and similar peristalsis diseases. These results suggest that rs9351963 in KCNQ5 is a possible predictive factor of incidence of diarrhea in cancer patients treated with irinotecan chemotherapy and for selecting chemotherapy regimens, such as irinotecan alone or a combination of irinotecan with a KCNQ5 opener. Nonetheless, clinical importance of rs9351963 should be further elucidated.

Independent strong association of HLA-A*02:06 and HLA-B*44:03 with cold medicine-related Stevens-Johnson syndrome with severe mucosal involvement.

Stevens-Johnson syndrome (SJS) and its severe variant, toxic epidermal necrolysis (TEN), are acute inflammatory vesiculobullous reactions of the skin and mucous membranes. Cold medicines including non-steroidal anti-inflammatory drugs (NSAIDs) and multi-ingredient cold medications are reported to be important inciting drugs. We used two sample sets of Japanese patients to investigate the association between HLA genotypes and cold medicine-related SJS/TEN (CM-SJS/TEN), including acetaminophen-related SJS/TEN (AR-SJS/TEN) with severe mucosal involvement such as severe ocular surface complications (SOC). HLA-A*02:06 was strongly associated with CM-SJS/TEN with SOC and AR-SJS/TEN with SOC. HLA-B*44:03 was also detected as an independent risk allele for CM-, including AR-SJS/TEN with SOC. Analyses using data obtained from CM-SJS/TEN patients without SOC and patients with CM-unrelated SJS/TEN with SOC suggested that these two susceptibility alleles are involved in the development of only CM-SJS/TEN with SOC patients.

Genetic factors associated with gemcitabine pharmacokinetics, disposition, and toxicity.

AIM: The goal of this work was to investigate the associations of genetic and environmental factors with gemcitabine disposition and toxicity from genomewide data using a novel information theoretic approach. METHODS: We utilized the information theoretic K-way interaction information (KWII) metric to detect gene-gene and gene-environment interactions associated with gemcitabine disposition and gemcitabine-induced neutropenia in genomic and clinical data from Japanese cancer patients. RESULTS: The information theoretic KWII analyses identified age and four genes - DMD, HEXDC, CNTN4, and ALOX5AP - to be associated with gemcitabine pharmacokinetics (PK). The rs4769060 single-nucleotide polymorphism in the ALOX5AP gene was associated with all PK parameters studied. For gemcitabine-induced neutropenia, multiple associations with long intergenic noncoding RNA regions were detected. Pathway analysis identified leukotriene and eoxin synthesis, platelet homeostasis, and L1CAM interactions as potential pathways associated with gemcitabine disposition. CONCLUSION: The KWII analyses detected novel associations with gemcitabine PK and toxicity. These results could be used to inform future investigations involving gemcitabine efficacy in clinical settings.

[Biomarker exploration and its clinical use].

Biomarkers are useful tools as indicators/predictors of disease severity and drug responsiveness, and thus, are expected to make drug development more efficient and to accelerate proper use of approved drugs. Many academic achievements on biomarkers have been reported, but only several biomarkers are used in drug development and clinical settings. We first show our results on the pharmacogenomic analysis of the anti-cancer drug irinotecan and of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). UGT1A1*6 and *28 were significantly associated with altered pharmacokinetics of an irinotecan metabolite, SN-38, and with increased frequency of severe neutropenia. HLA* 58:01 and HLA-B*15:11/HLA-A*31:01 were associated with SJS/TEN by allopurinol and carbamazepine, respectively. Our papers have been cited in the package inserts of irinotecan and allopurinol. In addition to these genomic biomarkers, metabolomic biomarkers, which can reflect the disease phenotype and drug responsiveness, have been exploring for 12 major diseases in Japan, as a part of a multi-omics team with multi-national centers. In animal models of dilated cardiomyopathy and Alzheimer's disease, we found several changes in lipid metabolite levels in the diseased tissues. Moreover, two oxidized fatty acids were correlatively changed in the brain and plasma from Alzheimer's model mice before its onset, and thus, could be candidates for predictive biomarkers. Finally, we propose/discuss several key issues for academic researches on biomarker discovery and development, especially for newly coming researchers in the field of pharmaceutical sciences. We hope that this review would help novel biomarker identification and qualification in Japan.

Specific HLA types are associated with antiepileptic drug-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Japanese subjects.

AIM: This preliminary study investigated genomic biomarkers for Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), related to three antiepileptic drugs, zonisamide, phenobarbital and phenytoin. PATIENTS & METHODS: HLA class I and HLA-DRB1 loci were genotyped for Japanese patients with zonisamide-, phenobarbital- or phenytoin-induced SJS/TEN (n = 12, 8 and 9, respectively) and for healthy Japanese volunteers (n = 2878). RESULTS: Carrier frequencies of HLA-A*02:07 in patients with zonisamide-induced SJS/TEN and in the general Japanese population were 41.7 and 6.81%, respectively. Carrier frequencies of HLA-B*51:01 in patients with phenobarbital- and phenytoin-induced SJS/TEN and in controls were 75.0, 55.6 and 15.2%, respectively. HLA-A*02:07 and HLA-B*51:01, in a dominant model, were significantly associated with zonisamide- and phenobarbital-induced SJS/TEN, respectively (Pc = 0.0176 and 0.0042, respectively). CONCLUSION: Our data suggest that HLA-A*02:07 and HLA-B*51:01 are potential biomarkers for zonisamide- and phenobarbital-induced SJS/TEN, respectively, in Japanese individuals.

Identification of a candidate single-nucleotide polymorphism related to chemotherapeutic response through a combination of knowledge-based algorithm and hypothesis-free genomic data.

Inter-individual variations in drug responses among patients are known to cause serious problems in medicine. Genome-wide association study (GWAS) is powerful for examining single-nucleotide polymorphisms (SNPs) and their relationships with drug response variations. However, no significant SNP has been identified using GWAS due to multiple testing problems. Therefore, we propose a combination method consisting of knowledge-based algorithm, two stages of screening, and permutation test for identifying SNPs in the present study. We applied this method to a genome-wide pharmacogenomics study for which 109,365 SNPs had been genotyped using Illumina Human-1 BeadChip for 119 gastric cancer patients treated with fluoropyrimidine. We identified rs2293347 in epidermal growth factor receptor (EGFR) is as a candidate SNP related to chemotherapeutic response. The p value for the rs2293347 was 2.19 × 10(-5) for Fisher's exact test, and the p value was 0.00360 for the permutation test (multiple testing problems are corrected). Additionally, rs2293347 was clearly superior to clinical parameters and showed a sensitivity value of 55.0% and specificity value of 94.4% in the evaluation by using multiple regression models. Recent studies have shown that combination chemotherapy of fluoropyrimidine and EGFR-targeting agents is effective for gastric cancer patients highly expressing EGFR. These results suggest that rs2293347 is a potential predictive factor for selecting chemotherapies, such as fluoropyrimidine alone or combination chemotherapies.

Pharmacogenomics of severe cutaneous adverse reactions and drug-induced liver injury.

Rare but severe adverse drug reactions (ADRs) are an important issue in drug development and in the proper usage of drugs during the post-approval phase. The ability to predict patient susceptibility to severe ADRs would prevent drug administration to high-risk patients. This would save lives and ensure the quality of life for these patients, but occurrence of idiosyncratic severe ADRs had been very difficult to predict for a long time. However, in this decade, genetic markers have been found for several ADRs, especially for severe cutaneous adverse reactions (SCARs) and drug-induced liver injury (DILI). In this review, we summarize recent progress in identifying genetic markers for SCARS and DILI, and discuss issues that remain unresolved. As for SCARs, associations of HLA-B*15:02 or HLA-A*31:01 and HLA-B*58:01 have been revealed for carbamazepine- and allopurinol-related Stevens-Johnson syndrome and toxic epidermal neclolysis, respectively. HLA-B*57:01 is strongly associated with abacavir-induced hypersensitivity syndrome. Several HLA alleles also demonstrate drug-specific associations with DILI, such as HLA-A*33:03 for ticlopidine, HLA-B*57:01 for flucloxacillin and HLA-DQA1*02:01 for lapatinib. Efforts should be continued to find other genetic markers to achieve high predictability for ADRs, with the goal being development of genetic tests for use in clinical settings.

The risk of cutaneous adverse reactions among patients with the HLA-A* 31:01 allele who are given carbamazepine, oxcarbazepine or eslicarbazepine: a perspective review.

Carbamazepine is a drug that is widely used for the treatment of epilepsy, trigeminal neuralgia and bipolar disorder. This drug is also known to cause cutaneous adverse drug reactions (cADRs) in up to 10% of patients. The recent progress in pharmacogenetics has revealed that human leukocyte antigen (HLA) genotypes are associated with a susceptibility to the cADRs caused by particular drugs. For carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis, very strong associations with HLA-B*15:02 have been found mainly in patients of Southeastern Asian origin. In some countries, prescreening HLA-B*15:02 allele has already been put to practical use as a biomarker to avoid the life-threatening adverse drug reactions. In this review, another risk factor for carbamazepine-induced cADRs is discussed, namely HLA-A*31:01. We compare the strength of the association between HLA-A*31:01 and carbamazepine-induced cADRs based on reports for various ethnic populations; discuss the difference between the HLA-A*31:01 and HLA-B*15:02 biomarkers and the usefulness of prescreening HLA-A*31:01 to detect patients at high risk for carbamazepine-induced cADRs; and refer to points that remain to be resolved.