Nahoko Kaniwa

HLA-B locus in Japanese patients with anti-epileptics and allopurinol-related Stevens-Johnson syndrome and toxic epidermal necrolysis.

INTRODUCTION Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but life-threatening severe cutaneous adverse reactions. Recently, strong associations of HLA-B*1502 and HLA-B*5801 with carbamazepine- and allopurinol-induced severe cutaneous adverse reactions were found in Han Chinese patients, respectively, but ethnic differences in the associations have been reported. The objective of this study is to clarify the involvement of HLA-B*1502 and HLA-B*5801 in Japanese SJS/TEN patients. METHODS HLA-B genotyping was performed on 58 Japanese SJS/TEN patients between July 2006 and April 2008 from multicenters in Japan. RESULTS There were no HLA-B*1502 carriers among 58 SJS/TEN patients. This patient group included seven carbamazepine-related and 11 aromatic anti-epileptic agent-related SJS/TEN patients. In addition, there were five HLA-B*5801 carriers, which included four allopurinol-related SJS/TEN patients. CONCLUSION While HLA-B*1502 is unlikely to be associated with carbamazepine-related or aromatic anti-epileptic agent-related SJS/TEN, HLA-B*5801 was significantly associated with allopurinol-related SJS/TEN in Japanese.

UGT1A1 Haplotypes Associated with Reduced Glucuronidation and Increased Serum Bilirubin in Irinotecan‐administered Japanese Patients with Cancer

A comprehensive haplotype analysis of UGT1A1 in the Japanese population was conducted, and the effects of these haplotypes were investigated with respect to UGT1A1‐related phenotypic parameters in patients with cancer who received irinotecan.

Irinotecan pharmacokinetics/pharmacodynamics and UGT1A genetic polymorphisms in Japanese: roles of UGT1A1*6 and *28.

Objectives SN-38, an active metabolite of irinotecan, is detoxified by glucuronidation with UGT1A isoforms, 1A1, 1A7, 1A9, and 1A10. The pharmacogenetic information on UGT1A haplotypes covering all these isoforms is important for the individualized therapy of irinotecan. Associations between UGT1A haplotypes and pharmacokinetics/pharmacodynamics of irinotecan were investigated to identify pharmacogenetic markers. Methods Associations between UGT1A haplotypes and the area under concentration curve ratio (SN-38 glucuronide/SN-38) or toxicities were analyzed in 177 Japanese cancer patients treated with irinotecan as a single agent or in combination chemotherapy. For association analysis, diplotypes of UGT1A gene segments [(1A1, 1A7, 1A9, 1A10), and Block C (common exons 2–5)] and combinatorial haplotypes (1A9-1A7-1A1) were used. The relationship between diplotypes and toxicities was investigated in 55 patients treated with irinotecan as a single agent. Results Among diplotypes of UGT1A genes, patients with the haplotypes harboring UGT1A1*6 or *28 had significantly reduced area under concentration curve ratios, with the effects of UGT1A1*6 or *28 being of a similar scale. A gene dose effect on the area under concentration curve ratio was observed for the number of haplotypes containing *28 or *6 (5.55, 3.62, and 2.07 for 0, 1, and 2 haplotypes, respectively, P<0.0001). In multivariate analysis, the homozygotes and double heterozygotes of *6 and *28 (*6/*6, *28/*28 and *6/*28) were significantly associated with severe neutropenia in 53 patients who received irinotecan monotherapy. Conclusions The haplotypes significantly associated with reduced area under concentration curve ratios and neutropenia contained UGT1A1*6 or *28, and both of them should be genotyped before irinotecan is given to Japanese and probably other Asian patients.

HLA-B*1511 is a risk factor for carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in Japanese patients

Stevens‐Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but life‐threatening severe cutaneous adverse reactions. Recently, strong associations of HLA‐B*1502 with carbamazepine‐induced SJS/TEN have been found in Han Chinese patients. These associations have been confirmed in several Asian populations, excluding Japanese. SJS patients carrying HLA‐B*1508, HLA‐B*1511, or HLA‐B*1521, which are members of the HLA‐B75 type along with HLA‐B*1502, were detected in studies in India and Thailand. In the current study, we genotyped the HLA‐B locus from 14 Japanese typical and atypical SJS/TEN patients in whom carbamazepine was considered to be involved in the onset of adverse reactions. Although there were no HLA‐B*1502 carriers, four patients had HLA‐B*1511. Our data suggest that HLA‐B*1511, a member of HLA‐B75, is a risk factor for carbamazepine‐induced SJS/TEN in Japanese.

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.

A whole-genome association study of major determinants for allopurinol-related Stevens–Johnson syndrome and toxic epidermal necrolysis in Japanese patients

Stevens–Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are severe, cutaneous adverse drug reactions that are rare but life threatening. Genetic biomarkers for allopurinol-related SJS/TEN in Japanese were examined in a genome-wide association study in which Japanese patients (n=14) were compared with ethnically matched healthy controls (n=991). Associations between 890 321 single nucleotide polymorphisms and allopurinol-related SJS/TEN were analyzed by the Fishers exact test (dominant genotype mode). A total of 21 polymorphisms on chromosome 6 were significantly associated with allopurinol-related SJS/TEN. The strongest association was found at rs2734583 in BAT1, rs3094011 in HCP5 and GA005234 in MICC (P=2.44 × 10−8; odds ratio=66.8; 95% confidence interval, 19.8–225.0). rs9263726 in PSORS1C1, also significantly associated with allopurinol-related SJS/TEN, is in absolute linkage disequilibrium with human leukocyte antigen-B*5801, which is in strong association with allopurinol-induced SJS/TEN. The ease of typing rs9263726 makes it a useful biomarker for allopurinol-related SJS/TEN in Japanese.

HLA Class I markers in Japanese patients with carbamazepine‐induced cutaneous adverse reactions

Carbamazepine (CBZ) is frequently used for treating epilepsy, but this drug causes cutaneous adverse drug reactions (cADRs) that may range from mild to severe. It is reported recently that the human leukocyte antigen HLA‐B*1502 is associated with Stevens‐Johnson syndrome (SJS) induced by CBZ in Han Chinese. We examined HLA class I in 15 Japanese patients who fulfilled the diagnostic criteria for CBZ‐induced cADRs (mild in 10 and severe = SJS in 5). HLA‐B*1518, HLA‐B*5901 and HLA‐C*0704 alleles showed higher relative risks (above 10.0) for severe cADRs. The haplotype (HLA‐A*2402‐B*5901‐C*0102) had high relative risk (16.09) for severe cADRs. In patients with severe cADRs, frequencies of HLA‐A*1101, HLA‐A*3303, HLA‐B*1501, HLA‐B*4403, HLA‐B*5101, HLA‐B*5201, HLA‐C*0702, and HLA‐C*1202 alleles are relatively lower than in the Japanese population. These data may suggest that HLA‐B*5901 is one of the candidate markers for CBZ‐induced SJS in Japanese.

Severe drug toxicity associated with a single-nucleotide polymorphism of the cytidine deaminase gene in a Japanese cancer patient treated with gemcitabine plus cisplatin.

Purpose: We investigated single-nucleotide polymorphisms of the cytidine deaminase gene (CDA), which encodes an enzyme that metabolizes gemcitabine, to clarify the relationship between the single-nucleotide polymorphism 208G>A and the pharmacokinetics and toxicity of gemcitabine in cancer patients treated with gemcitabine plus cisplatin. Experimental Design: Six Japanese cancer patients treated with gemcitabine plus cisplatin were examined. Plasma gemcitabine and its metabolite 2′,2′-difluorodeoxyuridine were measured using an high-performance liquid chromatography method, and the CDA genotypes were determined with DNA sequencing. Results: One patient, a 45-year-old man with pancreatic carcinoma, showed severe hematologic and nonhematologic toxicities during the first course of chemotherapy with gemcitabine and cisplatin. The area under the concentration-time curve value of gemcitabine in this patient (54.54 μg hour/mL) was five times higher than the average value for five other patients (10.88 μg hour/mL) treated with gemcitabine plus cisplatin. The area under the concentration-time curve of 2′,2′-difluorodeoxyuridine in this patient (41.58 μg hour/mL) was less than the half of the average value of the five patients (106.13 μg hour/mL). This patient was found to be homozygous for 208A (Thr70) in the CDA gene, whereas the other patients were homozygous for 208G (Ala70). Conclusion: Homozygous 208G>A alteration in CDA might have caused the severe drug toxicity experienced by a Japanese cancer patient treated with gemcitabine plus cisplatin.

Haplotype structures of the UGT1A gene complex in a Japanese population.

Genetic polymorphisms of UDP-glucuronosyltransferases (UGTs) are involved in individual and ethnic differences in drug metabolism. To reveal co-occurrence of the UGT1A polymorphisms, we first analyzed haplotype structures of the entire UGT1A gene complex using the polymorphisms from 196 Japanese subjects. Based on strong linkage disequilibrium between UGT1A8 and 1A10, among 1A9, 1A7, and 1A6, and between 1A3 and 1A1, the complex was divided into five blocks, Block 8/10, Block 9/6, Block 4, Block 3/1, and Block C, and the haplotypes for each block were subsequently determined/inferred. Second, using pyrosequencing or direct sequencing, additional 105 subjects were genotyped for 41 functionally tagged polymorphisms. The data from 301 subjects confirmed the robustness of block partitioning, but several linkages among the haplotypes with functional changes were found across the blocks. Thus, important haplotypes and their linkages were identified among the UGT1A gene blocks (and segments), which should be considered in pharmacogenetic studies.

Gastric acidity dependent bioavailability of cinnarizine from two commercial capsules in healthy volunteers

Abstract Two commercially available capsules of 25 mg cinnarizine, which were chosen from the results of dissolution tests as the extreme cases out of 32 such capsules available in Japan, were examined in detail to determine their dissolution properties and bioavailabilities. The two capsules had similar dissolution rates at pH 1.2 and at pH 6.0 even though the rate at pH 1.2 was much faster than at pH 6.0. The serum levels of cinnarizine, which were determined by a GC-MS technique after administration of a single cinnarizine capsule, showed a wide variation in human volunteers, and this was ascribable to differences in the gastric acidity of the subjects. The AUC 0–8h values of the two capsules in the subjects having low gastric acidity were only 27 and 14% of those in the high acidity group, and the C max values of the two capsules were also depressed to 32 and 14% of those in the high acidity subject group, respectively. Bioavailability of cinnarizine appears to be determined mainly by the amount dissolved in the stomach.