Adverse events of nivolumab plus ipilimumab versus nivolumab plus cabozantinib: a real-world pharmacovigilance study.

BACKGROUND: No head-to-head clinical trials have compared the differences in adverse events (AEs) between nivolumab plus ipilimumab (NIVO-IPI) and nivolumab plus cabozantinib (NIVO-CABO) in the treatment of metastatic renal cell carcinoma (mRCC). AIM: We analysed the two largest real-world databases, the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) and the World Health Organization's VigiBase, to elucidate the differences in AEs between NIVO-IPI and NIVO-CABO. METHOD: In total, 40,376 and 38,022 records were extracted from FAERS and VigiBase, and 193 AEs were analysed. The reporting odds ratios (ROR) with 95% confidence interval were calculated using a disproportionality analysis (NIVO-CABO/NIVO-IPI). RESULTS: The reported numbers of immune-related AEs, including myocarditis, colitis, and hepatitis, were significantly higher with NIVO-IPI (ROR = 0.18 for FAERS and 0.13 for VigiBase). Contrarily, the reported numbers of other AEs, including gastrointestinal disorders (ROR = 2.68 and 2.92) and skin and subcutaneous tissue disorders (ROR = 2.94 and 3.55), considered to be potentiated by the combination of NIVO and CABO, were higher with NIVO-CABO. CONCLUSION: Our findings contribute to the selection and clinical management of NIVO-IPI and NIVO-CABO, which minimizes the risk of AEs for individual patients with mRCC by considering distinctive differences in the AE profiles.

A comparison between the adverse event profiles of patients receiving palbociclib and abemaciclib: analysis of two real-world databases.

BACKGROUND: Palbociclib and abemaciclib are cyclin-dependent kinase (CDK) 4/6 inhibitors currently used to treat breast cancer. Although their therapeutic efficacies are considered comparable, differences in adverse event (AE) profiles of the two drugs remain unclear. AIM: We analysed two real-world databases, the World Health Organization's VigiBase and the Food and Drug Administration Adverse Event Reporting System (FAERS), to identify differences in AE profiles of palbociclib and abemaciclib. METHOD: Data of patients with breast cancer receiving palbociclib or abemaciclib recorded until December 2022 were extracted from the VigiBase and FAERS databases. In total, 200 types of AEs were analysed. The reporting odds ratios were calculated using a disproportionality analysis. RESULTS: Cytopenia was frequently reported in patients receiving palbociclib, whereas interstitial lung disease and diarrhoea were frequently reported in those receiving abemaciclib. Moreover, psychiatric and nervous system disorders were more common in the palbociclib group, whereas renal and urinary disorders were more common in the abemaciclib group. CONCLUSION: This study is the first to show comprehensively the disparities in the AE profiles of palbociclib and abemaciclib. The findings highlight the importance of considering these differences when selecting a suitable CDK4/6 inhibitor to ensure safe and favourable outcomes for patients with breast cancer.

Adverse Events of Axitinib plus Pembrolizumab Versus Lenvatinib plus Pembrolizumab: A Pharmacovigilance Study in Food and Drug Administration Adverse Event Reporting System.

No head-to-head postmarket surveillance study has compared the differences in adverse events (AEs) between two combination therapies, axitinib (AXI) + pembrolizumab (PEMBRO) and lenvatinib (LEN) + PEMBRO, against metastatic renal cell carcinoma. This study aims to highlight the comprehensive differences in AEs between these two therapies based on the real-world big data from the Food and Drug Administration Adverse Event Reporting System (FAERS) database. In total, 28 937 records were extracted from the FAERS database, and 139 AEs grouped into the System Organ Class according to the Medical Dictionary for Regulatory Activities were analysed. Logistic regression analyses were performed, and the reporting odds ratio with a 95% confidence interval was determined. We found that the incidences of cardiac and hepatobiliary disorders for AXI + PEMBRO, and blood and lymphatic system, metabolism and nutrition, and vascular disorders for LEN + PEMBRO, all of which were associated with serious AEs, were higher than those for LEN + PEMBRO and AXI + PEMBRO, respectively. The differences in the AEs between AXI + PEMBRO and LEN + PEMBRO were not derived merely from those between AXI and LEN monotherapies. Furthermore, remarkable AE potentiation was observed for AXI + PEMBRO. As FAERS is a spontaneous reporting system comprising partially limited information, analysing more detailed relationships between AEs and patient or treatment characteristics was challenging in this study. The present study is the first to show the overall real-world postmarketing differences in AEs between AXI + PEMBRO and LEN + PEMBRO. Our novel findings will substantially improve clinical practice; we recommend comparing patients' conditions associated with the above AEs when selecting between these two therapies. PATIENT SUMMARY: Herein, we highlight the differences in adverse events (AEs) between axitinib + pembrolizumab and lenvatinib + pembrolizumab therapies using data from the real-world Food and Drug Administration Adverse Event Reporting System database aimed at patients with metastatic renal cell carcinoma. We identified AEs that needed attention in each combination. We recommend the differences in AEs to be considered when selecting these two therapies.

Significance of UGT1A6, UGT1A9, and UGT2B7 genetic variants and their mRNA expression in the clinical outcome of renal cell carcinoma.

UDP-glucuronosyltransferase (UGT) metabolizes a number of endogenous and exogenous substrates. Renal cells express high amounts of UGT; however, the significance of UGT in patients with renal cell carcinoma (RCC) remains unknown. In this study, we profile the mRNA expression of UGT subtypes (UGT1A6, UGT1A9, and UGT2B7) and their genetic variants in the kidney tissue of 125 Japanese patients with RCC (Okayama University Hospital, Japan). In addition, we elucidate the association between the UGT variants and UGT mRNA expression levels and clinical outcomes in these patients. The three representative genetic variants, namely, UGT1A6 541A > G, UGT1A9 i399C > T, and UGT2B7-161C > T, were genotyped, and their mRNA expression levels in each tissue were determined. We found that the mRNA expression of the three UGTs (UGT1A6, UGT1A9, and UGT2B7) are significantly downregulated in RCC tissues. Moreover, in patients with RCC, the UGT2B7-161C > T variant and high UGT2B7 mRNA expression are significantly correlated with preferable cancer-specific survival (CSS) and overall survival (OS), respectively. As such, the UGT2B7-161C > T variant and UGT2B7 mRNA expression level were identified as significant independent prognostic factors of CSS and CSS/OS, respectively. Taken together, these findings indicate that UGT2B7 has a role in RCC progression and may, therefore, represent a potential prognostic biomarker for patients with RCC.

Relevance of CYP3A5 Expression on the Clinical Outcome of Patients With Renal Cell Carcinoma.

BACKGROUND/AIM: This study aimed to elucidate the detailed characteristics of CYP3A5 expression and the association between CYP3A5 expression and clinical outcomes in patients with renal cell carcinoma (RCC). PATIENTS AND METHODS: This study retrospectively enrolled 124 Japanese patients with RCC treated at the Okayama University Hospital. The commonest CYP3A5 gene polymorphism, CYP3A5*3, and expression levels of CYP3A5 mRNA and protein in each tissue were examined. RESULTS: Expression of CYP3A5 mRNA and protein in RCC tissues was significantly down-regulated compared to that in adjacent normal tissues. High level of CYP3A5 mRNA expression significantly extended cancer-specific survival (p=0.004) and overall survival (p=0.002). The CYP3A5 mRNA expression level was identified as a significant independent prognostic factor for both cancer-specific survival and overall survival. CONCLUSION: CYP3A5 could serve as a potential marker for prognostication and treatment planning for patients with RCC.

A randomized controlled, open-label early phase II trial comparing incidence of FOLFIRI.3-induced diarrhoea between Hangeshashinto and oral alkalization in Japanese patients with colorectal cancer.

WHAT IS KNOWN AND OBJECTIVE: We conducted a pilot clinical trial to investigate whether Hangeshashinto (TJ-14) could be substituted for oral alkalization in patients scheduled to undergo chemotherapy by FOLFIRI.3 regimen for colorectal cancer (CRC). METHODS: Patients with CRC were randomized 1:1 to a TJ-14 (7.5 g/day) group or an oral alkalization (sodium bicarbonate, 1.8 g/day; ursodeoxycholic acid, 300 mg/day) group. The primary endpoint was incident of late-onset diarrhoea. A total of 30 patients were randomized to either the TJ-14 group or the alkalization group. RESULTS AND DISCUSSION: There was no statistical difference in age, concomitantly used drugs or UGT1A1 genotypes between the groups. In the alkalization group (n = 15), the frequency of grade 0/1/2 and grade 3 diarrhoea was 73% and 27%, respectively. In the TJ-14 group (n = 14), the frequency of grade 0/1/2 and grade 3 diarrhoea was 79% and 21%, respectively. Grade 4 diarrhoea was not observed in either group. There was no statistically significant difference in other adverse events or in response to FOLFIRI.3 between the groups. WHAT IS NEW AND CONCLUSION: This pilot trial suggests that TJ-14 is a promising alternative treatment option to reduce FOLFIRI.3-induced late-onset diarrhoea, although additional clinical study with a larger number of patients is necessary to confirm these results.

An extremely high bioavailability of orally administered vancomycin in a patient with severe colitis and renal insufficiency.

Because there is little absorption of orally administered vancomycin hydrochloride (VCM) through the normal intestinal microvillus membrane, the pharmacokinetics of VCM absorbed from the digestive tract are mostly unknown. Here we report a case of severe colitis and renal insufficiency in which the serum concentration of VCM reached the supratherapeutic range after oral administration. A 54-year-old man receiving outpatient chemotherapy for rectal cancer was admitted to our hospital for severe sepsis and acute renal failure. Multimodal therapy including continuous renal replacement therapy (CRRT) and mechanical ventilation was initiated, and oral VCM administration (0.5 g every 6 h) was begun for suspected severe pseudomembranous colitis with large amounts of watery stool. Despite continued CRRT, the serum VCM concentration increased to 30.6 µg/mL after 4 days. Based on pharmacokinetic analysis, the bioavailability of VCM was estimated to be over 54.5%. Colonoscopy showed that the mucosa was severely damaged throughout the large intestine, resulting in considerable exudation of plasma and blood. This case indicates the need for careful and early monitoring during high-dose oral VCM administration to patients with severe mucosal injury and renal insufficiency.

Increased platelet inhibition after switching from maintenance clopidogrel to prasugrel in Japanese patients with stable coronary artery disease.

BACKGROUND: The pharmacodynamic effects of changing from standard-dose clopidogrel to low-dose (3.75 mg) prasugrel in Japanese patients are largely unknown. METHODS AND RESULTS: A total of 53 consecutive Japanese patients with stable coronary artery disease (CAD) who received aspirin and clopidogrel were enrolled. Clopidogrel was switched to 3.75 mg prasugrel. At day 14, prasugrel was switched to 75 mg clopidogrel. Platelet reactivity was measured using the VerifyNow assay at baseline, day 14, and day 28. VerifyNow P2Y12 reaction units (PRU) >208 was defined as high on-treatment platelet reactivity (HPR). The prevalence of HPR (18.9% vs. 41.5% vs. 44.2%, P<0.001) and the PRU level (154.3±54.2 vs. 196.2±55.5 vs. 194.6±55.8, P<0.001) were significantly lower on prasugrel maintenance therapy compared with the clopidogrel therapy before and after switching. The CYP2C19 genotypes that account for the 3 phenotypes (ie, extensive metabolizer, intermediate metabolizer, and poor metabolizer) had a significant impact on platelet reactivity with clopidogrel (174.9±54.0 vs. 193.1±56.5 vs. 240.6±25.4 PRU, P<0.001) but not prasugrel (147.0±51.9 vs. 147.5±58.3 vs. 184.4±38.3 PRU, P=0.15). CONCLUSIONS: Low-dose prasugrel achieves stronger platelet inhibition than clopidogrel in Japanese patients with stable CAD.

Organic anion transporting polypeptide 2B1 expression correlates with uptake of estrone-3-sulfate and cell proliferation in estrogen receptor-positive breast cancer cells.

Estrone-3-sulfate (E1S) is thought to be a major estrogen precursor in estrogen receptor (ER)-positive breast cancer. Since E1S is a hydrophilic compound, the uptake of E1S into cancer cells is probably mediated by transporters, such as organic anion-transporting polypeptide (OATP, SLCO) family. In this study, we investigated the relationship between expression of OATP2B1 and cell proliferation in ER-positive breast cancer. Cell-based assays were carried out in MCF-7 cells both with and without overexpression of OATP2B1. Normal breast and tumor tissues were collected and used in this study. Cell proliferation, ER-mediated transcriptional activities and estradiol secretion were stimulated by addition of E1S to the culture medium of MCF-7 cells. These stimulatory effects were significantly greater in MCF-7 cells overexpressing OATP2B1 than in control cells. The expression level of SLCO2B1 mRNA was significantly correlated with histological grade, Ki-67 labelling index and mRNA expression of steroid sulfatase. The expression level of SLCO2B1 mRNA in luminal B-like cancers was higher than that in luminal A-like cancers. Uptake of E1S resulted in down-regulation of ERα protein and induction of Ki-67 in MCF-7 cells. The present study suggests that OATP2B1 is involved in cell proliferation by increasing the amount of estrogen in ER-positive breast cancer cells.

Genetic and non-genetic factors responsible for antiplatelet effects of clopidogrel in Japanese patients undergoing coronary stent implantation: an algorithm to predict on-clopidogrel platelet reactivity.

INTRODUCTION: Antiplatelet effects of clopidogrel appear to be affected by various factors including genetic polymorphism. So far, there has been little information about the response of clopidogrel in Asians, whose prevalence of a CYP2C19 loss-of-function (LOF) allele is high. METHODS AND RESULTS: We investigated background and clinical factors affecting on-clopidogrel platelet reactivity in Japanese patients undergoing coronary stent implantation (n=114). In univariate analysis, antiplatelet effects of clopidogrel in a steady state were associated with not only CYP2C19 genotypes but also several factors including dyslipidemia. In addition, we developed an algorithm that can estimate P2Y12 Reaction Units (PRU) in a steady state by multiple regression analysis and evaluated the adequacy of the algorithm by the Akaike Information Criterion. CONCLUSIONS: We revealed several factors influencing on-clopidogrel platelet reactivity in Japanese patients. We also succeeded in developing an algorithm that estimates PRU in a steady state, although it is uncertain whether the algorithm can be applied to other populations.

Functional characterization of seven single-nucleotide polymorphisms of the steroid sulfatase gene found in a Japanese population.

Steroid sulfatase (STS) is an enzyme that hydrolyzes steroid sulfates such as dehydroepiandrosterone sulfate (DHEA-S) and estrone sulfate. STS has a key role in the synthesis of steroid hormones in placenta and breast cancer cells. Recently, we have identified six novel single-nucleotide polymorphisms (SNPs) and one nonsynonymous SNP (V476M) in the STS gene in a Japanese population. To clarify the effects of SNPs in the 5'-flanking region or 5' untranslated region on transcriptional activity, a reporter gene assay was conducted. In addition, DHEA-S desulfatase activity of a variant (Met at codon 476)-type enzyme was compared with that of the wild (Wd)-type enzyme in COS-1 cells. The transcriptional activities were significantly decreased (155A) and increased (-2837A and -1588C) in MCF-7 cells. On the other hand, no significant difference was found in expression levels of STS protein or specific activities of DHEA-S desulfation between Wd and the variant enzymes. This is the first report on the effects of various SNPs in the STS gene detected in Japanese healthy subjects.

Application of Akaike information criterion to evaluate warfarin dosing algorithm.

INTRODUCTION: Several factors responsible for inter-individual differences in response to warfarin have been confirmed; however, unidentified factors appear to remain. The purpose of this study was to examine a simple method to evaluate whether optional variables are appropriate as factors to improve dosing algorithms. MATERIALS AND METHODS: All patients were Japanese. Genotyping of selected genes was conducted, and other information was obtained from medical record. Dosing algorithms were constructed by multivariate linear regression analyses and were evaluated by the Akaike Information Criterion (AIC). RESULTS AND CONCLUSIONS: Multivariate analysis showed that white blood-cell count (WBC), concomitant use of allopurinol, and CYP4F2 genotype are apparently involved in warfarin dose variation, in addition to well-known factors, such as age and VKORC1 genotype. We evaluated the adequacy of these variables as factors to improve the dosing algorithm using the AIC. Addition of WBC, allopurinol administration and CYP4F2 genotype to the basal algorithm resulted in decreased AIC, suggesting that these factor candidates may contribute to improving the prediction of warfarin maintenance dose. This study is the first to evaluate the warfarin dosing algorithm by AIC. To further improve the dosing algorithm, AIC may be a simple and useful tool to evaluate both the model itself and factors to be incorporated into the algorithm.

Kefiran reduces atherosclerosis in rabbits fed a high cholesterol diet.

AIM: Kefiran is an exopolysaccharide produced by Lactobacillus kefiranofaciens, and has been proposed to have many health-promoting properties. We investigated the antiatherogenic effect of kefiran on rabbits fed a high-cholesterol diet. METHODS: Male New Zealand White rabbits were fed a 0.5% cholesterol diet without (control group, n = 7) or with kefiran (kefiran group, n = 8) for eight weeks. The aorta was analyzed by histochemistry and atherosclerotic lesions were quantified. Lipids and sugars in serum were measured. Foam cell formation of RAW264.7 by ßVLDL derived from both groups of rabbits was also investigated. RESULTS: Cholesterol, triglyceride and phospholipids levels of serum and lipoprotein fractions were not significantly different between these groups. Atherosclerotic lesions of the aorta in the kefiran group were statistically lower than those of the control group, with marked differences in the abdominal aorta. T-lymphocytes were not detectable in the aorta of the kefiran group. Cholesterol contents in stools were almost identical in both groups. Cholesterol content in the liver of the kefiran group was statistically lower than in the control group. Galactose content of ßVLDL derived from the kefiran group was higher, and the lipid peroxidation level was much lower than in the control group. RAW264.7 macrophages treated with ßVLDL from the kefiran group showed a more spherical shape and accumulated statistically lower cholesterol than macrophages treated with ßVLDL from the control group. CONCLUSION: Orally derived kefiran is absorbed in the blood. Kefiran prevents the onset and development of atherosclerosis in hypercholesterolemic rabbits by anti-inflammatory and anti-oxidant actions.

Super-acute onset of tumor lysis syndrome accompanied by hypercytokinemia during treatment of Hodgkin's lymphoma with ABVD chemotherapy.

BACKGROUND: Tumor lysis syndrome (TLS) is a group of life-threatening metabolic complications that can occur after initiation of cancer chemotherapy. Onset of TLS in the middle of chemotherapy, however, has not been reported previously in patients with hematologic malignancies. OBJECTIVE: We report a case of a patient who experienced TLS of super-acute onset accompanied by hypercytokinemia during chemotherapy treatment with a combination of doxorubicin (Adriamycin), bleomycin, vinblastine, and dacarbazine (ABVD). CASE SUMMARY: A 36-year-old Japanese man (height, 182 cm; weight, 83 kg; body surface area, 2.04 m(2)) was admitted to the hospital for the treatment of malignant lymphoma (clinical stage IVB Hodgkin's lymphoma). Chemotherapy was initiated using the ABVD regimen (doxorubicin [Adriamycin] 25 mg/m(2) by 30-minute infusion, bleomycin 9 mg/m(2) by 30-minute infusion, vinblastine 6 mg/m(2) by bolus injection, and dacarbazine 375 mg/m(2) by 2-hour infusion). During the dacarbazine infusion, the patient's body temperature rose from 36.5 degrees C to 42 degrees C; he experienced a convulsion and then lost consciousness. The convulsion was not suppressed despite the use of diazepam (5 mg IV twice) and phenytoin (500 mg IV). The patient was then transferred to the intensive care unit and sedated using a continuous infusion of midazolam (10 mg/h). Levels of serum lactate dehydrogenase, aspartate aminotransferase, uric acid, blood urea nitrogen, and creatinine evaluated shortly after the ABVD regimen were outside normal limits. In addition, interleukin-6 (IL-6) concentrations were elevated to 54,220 pg/mL. Continuous hemodiafiltration was immediately performed to lower the elevated levels of IL-6. The next day, IL-6 concentrations decreased to 97 pg/mL, and the patient was weaned from ventilator support and sedation. The patient had no adverse effects after the event. According to the results of an assessment using the Naranjo adverse drug reaction probability scale (score = 3), the development of TLS in this patient was possibly related to the chemotherapy regimen. CONCLUSIONS: ABVD chemotherapy was possibly associated with the super-acute onset of TLS in this patient. In addition, hypercytokinemia occurred with TLS, which led to pyrexia, convulsion, and loss of consciousness.

Probable interaction between warfarin and antitumor agents used in R-ESHAP chemotherapy.

BACKGROUND: The pharmacologic effects of warfarin might be altered by various factors, including drug-drug interaction. CASE SUMMARY: A 49-year-old Japanese man (height, 174 cm; weight, 68 kg) presented with a 20-month history of malignant lymphoma (diffuse large B cell lymphoma, clinical stage IV). He was treated with a combination of rituximab chemotherapy and etoposide, cisplatin, high-dose cytarabine, and methyl-prednisolone (R-ESHAP). He had been receiving warfarin for the secondary prevention of pulmonary embolism with deep venous thrombosis. When R-ESHAP was started, international normalized ratio (INR) increased from 1 to 5. This phenomenon was observed again in the second R-ESHAP. The INR was increased from 2.44 to 4.71 during chemotherapy but was returned to within the normal range (1.05; normal range: 0.81-1.009) 5 days after chemotherapy was completed. CONCLUSION: In this patient, R-ESHAP chemotherapy might have affected warfarin anticoagulation sensitivity; thus, careful monitoring of INR is essential, particularly in patients receiving warfarin who undergo R-ESHAP chemotherapy.

Population pharmacokinetics of oral busulfan in young Japanese children before hematopoietic stem cell transplantation.

The objectives of this study were to develop a population pharmacokinetic model and to determine the covariates affecting the pharmacokinetics of busulfan in Japanese pediatric patients who received high-dose oral busulfan as a conditioning regimen before hematopoietic stem cell transplantation. Population analysis was performed using retrospective therapeutic drug monitoring data (including test dose data) from 103 children. Their ages ranged from 2 months to 11 years old (mean age, 30 months; median age, 18 months). The plasma concentration of busulfan in all 1028 samples was measured with the same high-performance liquid chromatography method. Maximum likelihood estimates were sought for pharmacokinetic parameters with the NONMEM program. The best structural covariate-free model for busulfan was a one-compartment model with an exponential error model to account for intersubject variability and a proportional error model to account for intrasubject variability. The apparent oral clearance was found to be correlated with age, aspartate transaminase, and type of disease (malignant disease or other). The apparent volume of distribution was related to body weight. The busulfan formulation (1% powder form or crystal form) and dose (milligrams per kilogram) influenced the absorption rate constant. It was estimated that oral clearance expressed per kilogram of body weight is low at early infancy, then increases to a maximum at approximately 2 years of age and, thereafter, decreases. In conclusion, we have developed a population pharmacokinetic model of oral busulfan in children, particularly for those younger than 4 years old, that takes into consideration not only body size, but also several other covariates.

Direct interaction between substrates and endogenous steroids in the active site may change the activity of cytochrome P450 3A4.

CYP3A4 exhibits unusual kinetic characteristics that result from the metabolism of multiple substrate including endogenous steroids and some drugs that coexist at the active site. To clarify the mechanism of the effect of endogenous steroids on the drug metabolism, the interaction between substrates, nevirapine (NVP) and carbamazepine (CBZ), and endogenous steroids was investigated by theoretical calculations. When the activities of NVP 2-hydroxylation and CBZ 10,11-epoxidation by expressed CYP3A4 were measured in the presence of steroids, NVP 2-hydroxylation was found to be remarkably increased by aldosterone and inhibited by estradiol. CBZ 10,11-epoxidation was increased by androstenedione. Three-dimensional computer modeling has shown that the active site of CYP3A4 is especially large, permitting access of two substrate molecules. The interactions between NVP and aldosterone and between CBZ and androstenedione were estimated by theoretical calculations assuming the substrate and steroids to be present in the active site at the same time. It was shown that NVP or CBZ would be stably fixed close to the oxygen atom at the sixth ligand of heme by interaction with steroids, suggesting that NVP and CBZ may be hydroxylated more easily due to the interaction with steroids. Estradiol was also expected to interact with NVP via a pi/pi interaction between a benzene ring, in which the NVP hydroxylation site is located, and a benzene ring of estradiol, suggested to inhibit the reaction. From these results, interactions between the substrate and endogenous steroids in the active site may change the activity of CYP3A4.

Association of CYP2A6 gene deletion with cigarette smoking status in Japanese adults.

BACKGROUND: Genetic variation of CYP2A6 is shown to alter nicotine metabolism. This study was developed to investigate the genetic influence of the whole deletion-allele of CYP2A6 on active and passive smoking behavior. METHODS: Two hundred and forty Japanese adults, who visited Aichi Cancer Center as outpatients, were genotyped for the wild-type (CYP2A6*1A, CYP2A6*1B) and the whole deletion-type (CYP2A6*4C) polymorphism of CYP2A6. Information about active and passive smoking status was obtained by a self-administered questionnaire. Genetic influence of CYP2A6 polymorphism on smoking behavior was evaluated using the Mantel extension test. RESULTS: The frequency of the deletion allele was 18%. All 8 subjects carrying two deletion alleles had no smoking habit, and the homozygous deletion genotype showed a tendency to correlate with active smoking status after adjustment for sex and age (p = 0.054). However, the proportion of never smokers among heterozygous subjects was almost the same as among subjects carrying no deletion allele (54% and 58%, respectively). Furthermore, CYP2A6 genotypes were correlated neither with the number of cigarettes smoked per day nor with the age at starting smoking (p = 0.364 and 0.880, respectively). Among never smokers, CYP2A6 genotypes were not correlated with exposure to passive smoking at home or in the workplace (p = 0.623 and 0.484, respectively). CONCLUSION: Despite the possible protection against active smoking behavior in subjects homozygous for the deletion allele, the CYP2A6 polymorphism has only a limited impact on public health because no protective effect was found in heterozygous subjects.