Yuko Okada

Genetic polymorphism of CYP2C9 and CYP2C19 in a Bolivian population: an investigative and comparative study

ObjectiveSeveral reports of CYP2C genetic polymorphism demonstrate its potential clinical role in determining both inter-individual and inter-ethnic differences in drug efficacy. We estimated the distribution of CYP2C9 and CYP2C19 common variants in the Bolivian population (a South American population), and compared these data with those from Asian, African, Caucasian and Oceanian populations.MethodsGenomic DNA was obtained from 778 unrelated healthy volunteers from Bolivia. The genotypic status of CYP2C9 and CYP2C19 was determined by means of polymerase chain reaction–restriction fragment length polymorphism.ResultsAllelic and genotypic frequencies of CYP2C9 and CYP2C19 were determined for the Bolivian population, and comparison of the data with other ethnic groups revealed a lower CYP2C9*2 frequency (4.8%) than in Caucasians, but a higher frequency than in Asians; frequencies of CYP2C9*3 (3.0%) and CYP2C9 (0.4%) poor metabolizers (PMs) were similar to those seen in Asian populations. Frequencies of CYP2C19*2 (7.8%), CYP2C19*3 (0.1%), and CYP2C19 PMs (1.0%) in the Bolivian population were for the most part lower than in Caucasian, Asian, Oceanian and African populations.ConclusionThis is the first study to investigate a South American population for genetic polymorphism in the CYP2C subfamily. The Bolivian population differs from most other ethnic groups in the incidence of CYP2C9 and CYP2C19 common variants that might be influenced by its admixture characteristics.

CYP4F2 gene polymorphism as a contributor to warfarin maintenance dose in Japanese subjects

What is known and Objective:  Polymorphisms in the gene encoding CYP4F2 may partly explain the variability in warfarin maintenance dose by altering the metabolism of vitamin K. To determine the genetic factors that cause large inter‐patient variability in warfarin efficacy, we investigated the relationship between serum warfarin concentration and CYP4F2 V433M (1347C>T, rs2108622) polymorphism in Japanese subjects.

Pro32Thr Polymorphism of Inosine Triphosphate Pyrophosphatase Gene Predicts Efficacy of Low-Dose Azathioprine for Patients With Systemic Lupus Erythematosus

We evaluated the relationship between the efficacy of low‐dose azathioprine (AZA) therapy and the inosine triphosphate pyrophosphatase (ITPA) 94C>A (Pro32Thr) polymorphism in patients with systemic lupus erythematosus (SLE). We performed a multiple regression analysis to assess the influence of various factors on the reduction in SLE disease activity index (SLEDAI) scores. The ITPA 94C>A polymorphism had the highest correlation with the change in SLEDAI score (r = 0.354, P = 0.006).

Inosine triphosphate pyrophosphatase 94C> A polymorphism: clinical implications for patients with systemic lupus erythematosus treated with azathioprine

Importance of the field: Azathioprine (AZA) has immunosuppressive property and has been widely used in organ transplantation and in several autoimmune diseases including systemic lupus erythematosus. The use of AZA is limited by the occurrence of adverse drug reactions (ADRs) leading to treatment discontinuation. Under AZA therapy, inosine triphosphate pyrophosphatase (ITPA) deficiency presumably leads to accumulation of unusual thioinosine metabolites with the potential for ADRs. Japanese patients require lower doses of AZA compared with Caucasian patients to achieve the same concentration of active metabolites. This ethnic difference in part is probably due to genetic polymorphisms of ITPA. Areas covered in this review: Relationships between ITPA genotype and enzyme activity, and efficacy and toxicity of AZA in both Caucasian and Asian populations are reviewed. Take home message: Clinical studies using a dose of < 1.5 mg/kg/day in various autoimmune diseases have shown no association between ITPA genotype and ADRs. In studies using higher doses, ITPA deficiency appears to increase the risk for AZA toxicity. Genotyping of ITPA may be useful to achieve dose optimization. It is important to maintain the dose of AZA < 1.5 mg/kg/day for Asian patients with ITPA 94A allele, with careful monitoring of the therapeutic efficacy.

Pharmacokinetic individualization of high-dose methotrexate chemotherapy for the treatment of localized osteosarcoma.

Abstract Individualization of high-dose methotrexate (MTX) dosing is important to achieve therapeutic levels (700-1,000 μm) for osteosarcoma. therefore we developed a pharmacokinetically (PK) individualized dosage regimen to maintain MTX concentrations of 700 μm (1 h bolus followed by 5 h maintenance infusion) and evaluated its safety and efficacy. Loading and maintenance doses were calculated by the PK parameters based on 2-compartment model analysis. Thirty-two courses of chemotherapy were performed in 9 patients with osteosarcoma. The maximum concentrations during maintenance infusion in 31 courses (97%) were above 700 μm. Only 1 patient developed severe hepatotoxicity as adverse effect. Total body clearance of MTX decreased in 4 patients when weekly MTX chemotherapy was performed for 3 consecutive weeks. Although the clearance was changed, the average MTX concentrations were maintained at about 700 μm by the PK individualization. The 5-year survival rate was 77.8% (7 of 9 patients), and all of them have survived for more than 9 years. This PK individualization is safe and useful for tailoring high-dose MTX therapy to achieve therapeutic levels.

Development of a single-tube PCR-pyrosequencing method for the simultaneous and rapid detection of four variant alleles of CYP2C9 gene polymorphism

Background and Objective:  CYP2C9 is a polymorphic enzyme that has been reported to metabolize several clinically useful drugs such as warfarin, phenytoin and non‐steroidal anti‐inflammatory drugs. We designed a rapid single‐tube multiplex assay to detect four variant alleles of the CYP2C9 in a single polymerase chain reaction (PCR) and a single pyrosequencing reaction.

Analysis of cytochrome P450 gene polymorphism in a lupus nephritis patient in whom tacrolimus blood concentration was markedly elevated after administration of azole antifungal agents

What is known and Objective:  Both itraconazole (ITCZ) and voriconazole (VCZ) are potent inhibitors of cytochrome P450 (CYP) 3A, and their effects have been reported to be equal. However, ITCZ is metabolized by CYP3A, whereas VCZ is mainly metabolized by CYP2C9 and CYP2C19 and only partially by CYP3A. We experienced the case of a patient who showed a 5‐fold increase in trough levels of tacrolimus (FK) level after switching from ITCZ to VCZ. Our objective is to discuss the mechanism of the increase drug–drug interaction in terms of serum concentration of the azole drugs and patient pharmacogenomics.

Effect of a Dietary Supplement Containing Raspberry Ketone on CYP3A Activity in Healthy Women

Objective: Raspberry ketone (RK) is available as a supplement with effect on weight gain suppression. Recent studies have found that various herbal products can affect the activities of drug metabolizing enzymes and drug efflux proteins, and provoke clinically relevant drug-drug interactions. Capsaicin, a molecule having a similar chemical structure to RK, is another well-known cytochrome P450 (CYP) inhibitor. On the other hand, it is totally unclear whether RK has any effect on human CYP activities. In this study, we evaluated the effect of orally administered RK on CYP3A activity by measuring 6beta-hydroxycortisol/cortisol ratio in urine samples. Methods: This clinical study was conducted with approval by the Institutional Review Board at Gunma University Hospital. A total of 7 healthy women aged between 20 and 35 years were included and all of them provided written informed consent. Urine samples were collected from all subjects on the morning of day 5 (± 1 day) of menstrual cycle. In the subsequent RK phase, subjects took 3 tablets (16.7 mg/tab) of RK 3 times daily for 7 days, followed by urine sampling on the morning of day 8. In the control phase, the second morning urine sampling was performed 8 days after the first sampling. Urine 6 beta-hydroxycortisol and cortisol concentrations were measured by HPLC UV method and the 6 beta-hydroxycortisol to cortisol ratio was compared between the two phases. Results: The mean basal and assessment ratios in the RK phase were 7.49 ± 4.76 and 9.20 ± 8.05, respectively, while the corresponding ratios in the control phase were 5.36 ± 3.17 and 5.19 ± 4.61, showing no significant difference in either phase. Conclusion: RK does not affect CYP3A activity.

Effect of a Dietary Supplement Containing Raspberry Ketone on Cytochrome P450 3A Activity

Objective: Various herbal medicines and dietary supplements are known to alter the effects of drugs and cause severe complications. One of the most famous examples is St. John’s wort, which promotes an increase of cytochrome P450 2C9 (CYP2C9), CYP2C19, and CYP3A4 expression, and reduces the effects of a large number of drugs. Raspberry ketone, an aromatic ingredient extracted from raspberries, is sold in Japan as a herbal supplement with a claimed slimming effect; however, its effect on CYP activity is unknown. To clarify the risk of an interaction between raspberry ketone-related supplements and CYP3A substrates, we performed an in vivo pharmacokinetic study using rats. Methods: We investigated the effect of the oral administration of raspberry ketone on the pharmacokinetics of midazolam, a typical CYP3A substrate, in rats. St. John’s wort, as a positive control, and raspberry ketone tablets at a dose of 50 mg/kg were administered every 12 h for 7 days, and at 24 h after the final treatment, 10 mg/kg midazolam was administered orally. The plasma concentration of midazolam was analyzed by high-performance liquid chromatography. Results: Oral clearance of midazolam in the St. John’s wort-treated group increased to 161% of that observed in the control group. Conversely, there was no significant difference between the raspberry ketone-treated and control groups. The mean residence time was essentially the same in all groups. Conclusion: Because raspberry ketone is considered to suppress the accumulation of body fat, it is mainly taken by young healthy women for weight loss. Considering this population, information about the interaction of raspberry ketone with oral contraceptives, which are substrates of CYP3A, is of clinical importance. In this study, raspberry ketone was found to have little impact on CYP3A activity, unlike St. John’s wort. These data indicate the low risk of an interaction between raspberry ketone-related supplements and many drugs metabolized by CYP3A.