Association of Nutritional Indices With Adverse Effects and Time-to-Treatment-Failure in Triple Therapy for Lung Cancer.

BACKGROUND/AIM: Recent lung cancer treatments include an immune checkpoint inhibitor (ICI) pembrolizumab, platinum-based agents, plus an additional cytotoxic anticancer agent. Nutritional indices, such as the geriatric nutritional risk index (GNRI) and the prognostic nutritional index (PNI), are known to correlate with the prognosis of cancer chemotherapy. Several previous studies have investigated the relationship between PNI and treatment response in non-small cell lung cancer patients, reporting significantly increased OS and PFS in the high PNI group before treatment. However, the relationship between the three-drug combination and GNRI/PNI is unclear. The current study aimed to investigate the association of nutritional indices with duration of treatment success and occurrence of side effects in triple therapy. PATIENTS AND METHODS: Seventy-two patients with non-small cell lung cancer, treated with combination of carboplatin, pemetrexed, and pembrolizumab from November 2019 to September 30, 2022, were classified into two groups (High and Low) for GNRI and PNI, and a retrospective study was performed. RESULTS: In terms of time-to-treatment-failure (TTF), univariate and multivariate Cox proportional hazards regression analysis showed the Low-PNI group to have significantly shorter TTF than the High-PNI group (p=0.006); multivariate analysis results also showed PNI as a factor affecting TTF (HR=2.791, 95%CI=1.362-5.721, p=0.005). On the other hand, GNRI was not shown to be a factor affecting TTF. CONCLUSION: PNI at the start of treatment was an independent prognostic factor affecting treatment success time (TTF) in non-small cell lung cancer patients receiving triple therapy. However, PNI was not shown to be a prognostic predictor of irAE development.

Adherence of denosumab treatment for low bone mineral density in Japanese people living with HIV: a retrospective observational study.

BACKGROUND: Long-term care issues, specifically metabolic bone disorders, are a concern for people living with human immunodeficiency virus (PLWH) who undergo life-long antiretroviral therapy (ART). Previous clinical trials with denosumab, an anti-RANKL antibody inhibitor, have revealed its effectiveness in increasing bone mineral density (BMD) in patients with osteoporosis. However, there are limited data on adherence and effectiveness of denosumab treatment for osteoporosis in PLWH. Hence, this study aimed to investigate the adherence and effectiveness of denosumab treatment for osteoporosis in Japanese PLWH. METHODS: This study is a retrospective exploratory analysis of 29 Japanese PLWH who initiated denosumab treatment for osteoporosis, between 2013 and 2021. The study included patients who received at least one dose of denosumab every 6 months. Adherence and persistence were defined as receiving two consecutive injections of denosumab 6 months ± 4 weeks apart and 6 months + 8 weeks apart, respectively. The primary outcome measure of the study was the adherence of denosumab treatment for 24 months. The secondary outcome measures included treatment persistence and BMD. The period after January 2020 was defined as the coronavirus disease 2019 (COVID-19) pandemic period, and its impact on adherence was investigated. RESULTS: The treatment adherence rates at 12 and 24 months were 89.7% and 60.7%, respectively. By contrast, the treatment persistence at 12 and 24 months was 100% and 85.7%, respectively. More patients in the group who initiated denosumab treatment after the COVID-19 pandemic reached non-adherence than in the group who initiated denosumab treatment before the pandemic. BMD at the lumbar spine and femoral neck significantly increased compared to that at baseline, with median percentage changes of 8.7% (p < 0.001) and 3.5% (p = 0.001), respectively. CONCLUSIONS: The results showed that patients in the study had a high rate of non-adherence but a lower rate of non-persistence. Additionally, PLWH on ongoing ART experienced increased BMD with denosumab treatment. This study provides an opportunity to improve future strategies for denosumab treatment in the Japanese PLWH.

The Relationship Between Efficacy and Safety of Osimertinib Blood Concentration in Patients With EGFR Mutation-positive Lung Cancer: A Prospective Observational Study.

BACKGROUND/AIM: Osimertinib blood levels and their impact on treatment continuation in patients with EGFR mutation-positive lung cancer is not known. This study investigated the drug blood levels and risk factors affecting treatment continuation. PATIENTS AND METHODS: Fifty-six patients with recurrent and inoperable epidermal growth factor receptor (EGFR) mutation-positive non-small cell lung cancer who received Osimertinib (80 mg once daily, daily dose) between October 1, 2016, and August 31, 2021, were included. Patients were classified into two groups using a cutoff blood level of 155 ng/ml. The primary endpoint was the relationship between Osimertinib exposure and efficacy, and secondary endpoints were the relationship between Osimertinib exposure and side effects, and the effect of covariates on efficacy and blood levels. RESULTS: The median progression-free survival (PFS) for evaluable patients in the steady-state trough concentration (Cmin ss) ≥155 ng/ml and Cmin ss <155 ng/ml groups was 18.7 months and 31.2 months. Serum albumin (Alb) levels were 3.73±0.40 g/dl and 3.93±0.28 g/dl (p=0.030), respectively, and in multivariate analysis, Alb <3.7 g/dl was associated with a hazard ratio of 5.304 (95%CI=1.431-19.66; p=0.013), indicating that Alb <3.7 g/dl significantly shortened PFS. CONCLUSION: Free blood concentration of Osimertinib may have been increased by a combination of factors, including decreased hepatic metabolic function and decreased albumin production caused by systemic inflammation in patients with cancer. However, there was no effect of Osimertinib Cmin ss on PFS.

Effect of renal clearance on vancomycin area under the concentration-time curve deviations in critically ill patients.

INTRODUCTION: Augmented renal clearance (ARC) increases vancomycin (VCM) clearance. Therefore, higher VCM doses are recommended in patients with ARC; however, impacts of ARC on the area under the concentration-time curve (AUC) discrepancies between initial dosing design and therapeutic drug monitoring (TDM) period remains unclear. METHODS: We retrospectively collected data from critically ill patients treated with VCM. The primary endpoint was the association between ARC and AUC24-48h deviations. ARC and AUC deviation were defined as a serum creatinine clearance (CCr) ≥130 mL/min/1.73 m2 and an AUC at TDM 30% or more higher than the AUC at the initial dosing design, respectively. The pharmacokinetic profiles of VCM were analyzed with the trough levels or peak/trough levels using the Bayesian estimation software Practical AUC-guided TDM (PAT). RESULTS: Among 141 patients (median [IQR]; 66 [58-74] years old; 30% women), 35 (25%) had ARC. AUC deviations were significantly more frequent in the ARC group than in the non-ARC group (20/35 [57.1%] and 17/106 [16.0%] patients, respectively, p < 0.001). Age- and sex-adjusted multivariate analyses revealed that the number of VCM doses before TDM ≥5 (odds ratio, 2.56; 95% confidence interval [CI]: 1.01-6.44, p = 0.047) and CCr ≥130 mL/min/1.73 m2 were significantly associated with AUC deviations (odds ratio, 7.86; 95%CI: 2.91-21.19, p < 0.001). CONCLUSION: Our study clarifies that the AUC of VCM in patients with ARC is higher at the time of TDM than at the time of dosage design.

Development and Validation of a Simple Method for Simultaneously Measuring the Concentrations of BCR-ABL and Bruton Tyrosine Kinase Inhibitors in Dried Blood Spot (DBS): A Pilot Study to Obtain Candidate Conversion Equations for Predicting Plasma Concentration Based on DBS Concentration.

BACKGROUND: Dried blood spots (DBSs) are promising candidates for therapeutic drug monitoring. In this study, a simple method for the simultaneous measurement of tyrosine kinase inhibitors (TKIs), including bosutinib, dasatinib, ibrutinib, imatinib, nilotinib, and ponatinib, using DBS was developed and validated. The prediction of the plasma concentration of TKIs based on the TKI concentrations in the DBS was assessed using the developed measurement method. METHODS: DBS was prepared using venous blood on Whatman 903 cards. One whole DBS sample containing the equivalent of 40 µL of blood was used for the analysis. The analytical method was validated according to the relevant guidelines. For clinical validation, 96 clinical samples were analyzed. The regression equation was derived from a weighted Deming regression analysis, and correction factors for calculating the estimated plasma concentrations (EPCs) of the analytes from their concentrations in the DBS and the predictive performance of EPC were evaluated using 2 conversion equations. RESULTS: This method was successfully validated. Hematocrit had no significant effect on the method's accuracy or precision. Ibrutinib was stable in the DBS for up to 8 weeks at room temperature, whereas all BCR-ABL TKIs were stable for 12 weeks. All BCR-ABL TKIs exhibited similar predictive performance for EPCs using both calculation methods. Good agreement between EPCs and the measured plasma concentrations of bosutinib, imatinib, and ponatinib was observed with both conversion equations. However, Bland-Altman analysis showed that blood sampling time affected the EPC accuracy for dasatinib and nilotinib. CONCLUSIONS: A simple method for the simultaneous determination of BCR-ABL and Bruton TKI concentrations in DBS was developed and validated. Owing to the small clinical sample size, further clinical validation is needed to determine the predictive performance of EPCs for the 6 TKIs.

An Liquid Chromatography-Tandem Mass Spectrometry Method for the Simultaneous Determination of Afatinib, Alectinib, Ceritinib, Crizotinib, Dacomitinib, Erlotinib, Gefitinib, and Osimertinib in Human Serum.

BACKGROUND: Routine therapeutic drug monitoring is a promising approach for the rational use of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and anaplastic lymphoma kinase (ALK) inhibitors. The purpose of this study was to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of 5 EGFR-TKIs (afatinib, dacomitinib, erlotinib, gefitinib, and osimertinib) and 3 ALK inhibitors (alectinib, ceritinib, and crizotinib). METHODS: A 100-mL aliquot of serum was diluted with 100 µL of 1% aqueous ammonia containing internal standards and then purified using the supported liquid extraction method. LC-MS/MS was conducted in positive ionization mode, and the method was validated according to published guidelines. RESULTS: Calibration curves were linear across concentration ranges examined. The intra- and interassay accuracies were 90.7%-110.7% and 94.7%-107.6%, respectively. All intra- and interassay imprecision values were ≤10.1%. The EGFR-TKIs and ALK inhibitors examined in this study, except osimertinib, which could be stored on ice for at least 5 hours, were stable at room temperature for 3 hours. For the internal standard-normalized matrix factors, the mean recovery and percent coefficient of variation values ranged between 54%-112% and 1.7%-11.7%, respectively. This method successfully determined serum concentrations of afatinib, alectinib, erlotinib, gefitinib, and osimertinib in clinical samples. Serum levels of kinase inhibitors consistently reflected those reported in previous studies. CONCLUSIONS: An LC-MS/MS method suitable for the simultaneous determination of 5 EGFR-TKIs and 3 ALK inhibitors in serum was developed and validated. The newly developed method enabled the determination of 5 of 8 target drugs examined in clinical samples. However, a large number of clinical samples need to be analyzed to verify the usefulness of the method.

Effects of angiotensin II receptor blockers on serum levels of epoxyeicosatrienoic acids and dihydroxyeicosatrienoic acids in patients admitted to a cardiovascular center.

PURPOSE: Several clinical studies have demonstrated that angiotensin-converting enzyme inhibitors, but not angiotensin II receptor blockers (ARBs), reduce the risk of non-fatal myocardial infarction and cardiovascular mortality. We found that ARBs inhibited the activity of various cytochrome enzymes in arachidonic acid metabolism, resulting in decreased in vitro production of epoxyeicosatrienoic acids (EETs), which exhibit vasodilation and anti-inflammatory effects, and their subsequent metabolites, dihydroxyeicosatrienoic acids (DHETs). The present study examined the effects of ARBs on serum levels of EETs and DHETs in patients admitted to a cardiovascular center. METHODS: A total of 223 patients were enrolled, of which 107 were exposed to ARBs in this study. ARB-free individuals were defined as the control group (n = 116). Serum levels of EETs and DHETs were measured by liquid chromatography-tandem mass spectrometry. Multiple linear regression analyses were carried out to identify covariates for total serum levels of EETs and DHETs. RESULTS: A significant negative association was observed between ARB use and serum EET and DHET levels (p = 0.034), whereas a significant positive association was observed between the estimated glomerular filtration rate (eGFR) and serum EET and DHET levels (p = 0.007). The median serum total EET and DHET level in the ARB group tended to become lower than that in the control group, although the difference was not significant. CONCLUSION: ARB use and eGFR were significantly associated with total serum levels of EETs and DHETs. Our results suggest that ARBs could affect the concentration of EETs in vivo.

Simultaneous Quantification of BCR-ABL and Bruton Tyrosine Kinase Inhibitors in Dried Plasma Spots and Its Application to Clinical Sample Analysis.

BACKGROUND: Recent reports highlight the importance of therapeutic drug monitoring (TDM) of BCR-ABL and Bruton tyrosine kinase inhibitors (TKIs); thus, large-scale studies are needed to determine the target concentrations of these drugs. TDM using dried plasma spots (DPS) instead of conventional plasma samples is a promising approach. This study aimed to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of BCR-ABL and Bruton TKIs for further TDM studies. METHODS: A 20-µL aliquot of plasma was spotted onto a filter paper and dried completely. Analytes were extracted from 2 DPS using 250 µL of solvent. After cleanup by supported liquid extraction, the sample was analyzed by LC-MS/MS. Applicability of the method was examined using samples of patients' DPS transported by regular mail as a proof-of-concept study. The constant bias and proportional error between plasma and DPS concentrations were assessed by Passing-Bablok regression analysis, and systematic errors were evaluated by Bland-Altman analysis. RESULTS: The method was successfully validated over the following calibration ranges: 1-200 ng/mL for dasatinib and ponatinib, 2-400 ng/mL for ibrutinib, 5-1000 ng/mL for bosutinib, and 20-4000 ng/mL for imatinib and nilotinib. TKI concentrations were successfully determined for 93 of 96 DPS from clinical samples. No constant bias between plasma and DPS concentrations was observed for bosutinib, dasatinib, nilotinib, and ponatinib, whereas there were proportional errors between the plasma and DPS concentrations of nilotinib and ponatinib. Bland-Altman plots revealed that significant systematic errors existed between both methods for bosutinib, nilotinib, and ponatinib. CONCLUSIONS: An LC-MS/MS method for the simultaneous quantification of 6 TKIs in DPS was developed and validated. Further large-scale studies should be conducted to assess the consistency of concentration measurements obtained from plasma and DPS.

Novel high-performance liquid chromatography-tandem mass spectrometry method for simultaneous quantification of BCR-ABL and Bruton's tyrosine kinase inhibitors and their three active metabolites in human plasma.

Therapeutic drug monitoring is important in patients taking BCR-ABL and Bruton's tyrosine kinase inhibitors (TKIs). Some TKI active metabolites with long elimination half-lives, such as dihydrodiol ibrutinib (DHI), N-desmethyl imatinib (N-DI), and N-desmethyl ponatinib (N-DP), have been characterized, indicating that these active metabolites should be monitored along with the parent compounds. However, there are currently no methods for the simultaneous quantification of BCR-ABL and Bruton's TKIs and their three active metabolites. The present study aimed to develop and validate a method for the simultaneous quantification of nine pharmacologically active compounds (bosutinib, dasatinib, DHI, ibrutinib, imatinib, N-DI, N-DP, nilotinib, and ponatinib) using high-performance liquid chromatography-tandem mass spectrometry. A 150-µL sample of plasma was analyzed after purification with supported liquid extraction. The method has a run time of 7 min and was successfully validated over the following calibration ranges: 0.25-75 ng/mL for N-DP, 0.5-150 ng/mL for dasatinib and ponatinib, 10-3000 ng/mL for imatinib and nilotinib, and 1-300 ng/mL for the other analytes. Stability of the analytes after short- and long-term storage in the presence of plasma matrix was examined, and all analytes were found to be stable under all tested conditions. The recovery was ≥83%, and the relative standard deviation of internal-standard normalized matrix effects ranged from 3.9 to 13.9%. Dilution integrity up to 4-fold was ensured. The applicability of the method for all analytes was demonstrated using patient samples.

Interior Temperature and Relative Humidity of an Envelope During Mail Transport by the Japan Post in the Summer: Preliminary Study for a Stability Test of Dried Blood Spot Samples Sent as Regular Mail.

BACKGROUND: The dried blood spot (DBS) is well studied and has been considered a useful technique for collecting biological specimens for therapeutic drug monitoring. Since DBS cards are transported as regular mail, these samples can be exposed to various climatic conditions while in transit. However, there have been limited amounts of data regarding interior temperature and relative humidity (RH) of the envelope during mail transport of DBS samples. This study investigated the interior temperature and RH during the transport of regular mail by Japan Post during the summer and assessed the effect of the gas permeability of zip lock bags on the interior temperature and RH when used as containers for the DBS card. METHODS: Either an aluminum zip lock bag, gas-impermeable, or a plastic zip lock bag, gas-permeable, containing a desiccant pouch (10 g) and a data logger was packed in an envelope and then transported by mail between Sapporo and Tsukuba/Kagoshima. The ambient temperature and RH in the above cities during the mail transport were obtained from the website of the Japan Meteorological Agency. RESULTS: The envelope was exposed to ≥30°C for up to 22 hours during the mail transport. Differences in the temperature between the interior and exterior of the envelope were almost completely within a range of ±4°C regardless of the gas permeability of the zip lock bags. Although the ambient RH was sometimes over 90% during mail transport, the mean interior RHs of the envelope containing the aluminum or plastic zip lock bag throughout the transport process were 13% and 17%, respectively. CONCLUSIONS: Both zip lock bags provided comparable results in relation to the interior temperature and RH of the envelope. Our results suggest that a stability test at 40°C and 90% RH for at least 24 hours is recommended as a validation process if DBS samples are transported as regular mail in Japan. However, conditions may need to be modified depending on the regions.

Combined effect of telmisartan and fluvastatin on arachidonic acid metabolism in human liver microsomes.

1. Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid (AA) via cytochrome P450s, have a protective effect on the cardiovascular system involving vasodilation. We have previously demonstrated that telmisartan (TEL) inhibits EETs production from AA in vitro. 2. The objectives of the study were to examine the inhibitory effect of fluvastatin (FLU), an inhibitor of CYP2C9, and the combined effect of TEL and FLU on the production of EETs using human liver microsomes. The combined effect of TEL and FLU was evaluated using two methods, the fixed concentration method and the fixed ratio method. 3. FLU significantly reduced total eicosanoids (sum of EETs and their subsequent metabolites dihydroxyeicosatrienoic acids) production at > 0.25 µM. The results of the fixed concentration method indicated that the addition of the other inhibitor resulted in significant reduction of the production of total eicosanoids in a concentration-dependent manner. In the fixed ratio method, the combination of TEL and FLU over all concentration ratios tested did not produce a horizontal shift in the dose response curves. 4. Our results showing an additive combined effect of TEL and FLU on AA metabolism, suggest that concomitant treatment with TEL and FLU would theoretically affect the vascular tone mediated by EETs from AA.

The Inhibitory Effect of Telmisartan on the Metabolism of Arachidonic Acid by CYP2C9 and CYP2C8: An in Vitro Study.

Epoxyeicosatorienoic acids (EETs) are generated from arachidonic acid (AA) by CYPs. EETs comprise four regioisomers (14,15-, 11,12-, 8,9-, and 5,6-EET). EETs show potent physiological effects, including vasodilation, anti-inflammation, myocardial preconditioning, and anti-platelet aggregation effects. We recently demonstrated that telmisartan, one of angiotensin II receptor blockers, inhibits AA metabolism by CYP enzymes, including CYP2C8, CYP2C9, and CYP2J2. We conducted studies of AA metabolism using recombinant CYP enzymes to estimate the inhibition constant and the type of inhibition by telmisartan of CYP2C9 and CYP2C8. The contribution ratio (CR) of each CYP enzyme was investigated using human liver microsomes. Dixon and Lineweaver-Burk plots indicated that telmisartan is a mixed inhibitor of both CYP2C9 and CYP2C8; telmisartan did not show a time-dependent inhibition toward these CYP enzymes. Based on the CRs, both CYP2C9 and CYP2C8 are the key enzymes in the metabolism of AA in the human liver. Uptake of telmisartan in the liver by organic anion transporting polypeptide (OATP) 1B3 and the non-linear metabolism in gastrointestinal tract augment the potential of the drug to inhibit the CYP enzymes in the liver.

Co-administration of Fluvastatin and CYP3A4 and CYP2C8 Inhibitors May Increase the Exposure to Fluvastatin in Carriers of CYP2C9 Genetic Variants.

Fluvastatin, which is one of the hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitors (statins), is primarily metabolized by CYP2C9 and to a lesser extent by CYP3A4 and CYP2C8. Predictions of drug-drug interactions (DDI) are important for the safety of combination therapies with statins, in particular drugs that are metabolized by CYP3A4. Little information is available regarding drug interactions with fluvastatin. Since CYP2C9 is a polymorphic enzyme, we investigated the effect of DDI via CYP2C9, CYP3A4, and CYP2C8 on fluvastatin pharmacokinetics by using a validated prediction method in relation to CYP2C9 variants. The predicted increases in the area under the concentration-time curve (AUC) ratios of fluvastatin in carriers with CYP2C9*1/*2, CYP2C9*1/*3, CYP2C9*2/*2, CYP2C9*2/*3, and CYP2C9*3/*3 versus that found in carriers with CYP2C9*1/*1 were 1.16, 1.35, 1.37, 1.65, and 2.06, respectively. Our in silico model predicted that administration of fluvastatin in conjunction with the potent inhibitors that completely inhibited CYP3A4 and CYP2C8 in carriers with the CYP2C9*3/*3 variant would cause a 3.23- and 2.60-fold increase in the AUC ratios, respectively, when compared to that for the carriers with the CYP2C9*1/*1 taking fluvastatin alone. We also predicted the effect of telmisartan when coadministered with fluvastatin. Our prediction results showed that the interaction between telmisartan and fluvastatin via CYP enzymes were negligible in clinical situations.

Concentration of Sulfate and Glucuronide Conjugates of Ritodrine in Twin Pregnancy.

Ritodrine, a drug for the treatment of threatened premature labor, is a highly selective beta-2 agonist with the major metabolites of sulfate and glucuronide conjugates. This study investigated the continuous evaluation of the concentration of ritodrine conjugates in relation to the clinical course in twin pregnancy. The subjects were 9 twin-pregnancy mothers who delivered after receiving ritodrine treatment between April 2012 and December 2013. Serum ritodrine sulfate and glucuronide conjugates were deconjugated using their specific enzymes. Ritodrine concentration was measured by liquid chromatography-tandem mass spectrometry. The continuous infusion rate of ritodrine was 2.66±0.67 (0.8-3.54) µg/min/kg, and the average concentration of unchanged ritodrine was 118.8±33.2 (63.8-194.0) ng/mL. During the study period between week 32 and week 36 of gestation, the average ratio of unchanged ritodrine concentration and sulfate ritodrine conjugate concentration for weeks 32, 33, 34, 35, and 36 were 1.7, 1.9, 1.5, 1.7, and 1.7 not significant (N.S.), respectively. The average ratio of unchanged ritodrine concentration and glucuronide ritodrine conjugate concentration were 1.8, 2.2, 1.9, 1.8, and 2.1 (N.S.), respectively. No statistical difference was identified in the ratios of unchanged ritodrine concentration and sulfate or glucuronide ritodrine conjugate concentrations. Large individual differences were shown in the concentration of sulfate and glucuronide during the gestational period. No change in the ratio of the formation of ritodrine metabolites was identified as the gestational age progressed.

Angiotensin II Receptor Blockers Inhibit the Generation of Epoxyeicosatrienoic Acid from Arachidonic Acid in Recombinant CYP2C9, CYP2J2 and Human Liver Microsomes.

Cytochrome P450 (CYP) 2C9, CYP2C8 and CYP2J2 enzymes, which metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids, have cardioprotective effects including anti-inflammation and vasodilation. We have recently shown that some angiotensin II receptor blockers (ARBs) may inhibit AA metabolism via CYP2C8. Using recombinant CYP2C9, CYP2J2 and human liver microsomes (HLMs), the aim was now to compare the ability of six different clinically used ARBs to inhibit AA metabolism in vitro. The rank order of the ARBs for the 50% inhibitory concentration (IC50 ) of AA metabolism was losartan

The Role of CYP2C8 and CYP2C9 Genotypes in Losartan-Dependent Inhibition of Paclitaxel Metabolism in Human Liver Microsomes.

The aim of the present study was to further investigate a previously identified metabolic interaction between losartan and paclitaxel, which is one of the marker substrates of CYP2C8, by using human liver microsomes (HLMs) from donors with different CYP2C8 and CYP2C9 genotypes. Although CYP2C8 and CYP2C9 exhibit genetic linkage, previous studies have yet to determine whether losartan or its active metabolite, EXP-3174 which is specifically generated by CYP2C9, is responsible for CYP2C8 inhibition. Concentrations of 6α-hydroxypaclitaxel and EXP-3174 were measured by high-performance liquid chromatography after incubations with paclitaxel, losartan or EXP-3174 in HLMs from seven donors with different CYP2C8 and CYP2C9 genotypes. The half maximal inhibitory concentration (IC50 ) values were not fully dependent on CYP2C8 genotypes. Although the degree of inhibition was small, losartan significantly inhibited the production of 6α-hydroxypaclitaxel at a concentration of 1 µmol/L in only HL20 with the CYP2C8*3/*3 genotype. HLMs with either CYP2C9*2/*2 or CYP2C9*1/*3 exhibited a lower losartan intrinsic clearance (Vmax /Km ) than other HLMs including those with CYP2C9*1/*1 and CYP2C9*1/*2. Significant inhibition of 6α-hydroxypaclitaxel formation by EXP-3174 could only be found at levels that were 50 times higher (100 µmol/L) than the maximum concentration generated in the inhibition study using losartan. These results suggest that the metabolic interaction between losartan and paclitaxel is dependent on losartan itself rather than its metabolite and that the CYP2C8 inhibition by losartan is not affected by the CYP2C9 genotype. Further study is needed to define the effect of CYP2C8 genotypes on losartan-paclitaxel interaction.

Effects of Angiotensin II Receptor Blockers on Metabolism of Arachidonic Acid via CYP2C8.

Arachidonic acid (AA) is metabolized to epoxyeicosatrienoic acids (EETs) via cytochrome enzymes such as CYP 2C9, 2C8 and 2J2. EETs play a role in cardioprotection and regulation of blood pressure. Recently, adverse reactions such as sudden heart attack and fatal myocardial infarction were reported among patients taking angiotensin II receptor blockers (ARBs). As some ARBs have affinity for these CYP enzymes, metabolic inhibition of AA by ARBs is a possible cause for the increase in cardiovascular events. In this study, we quantitatively investigated the inhibitory effects of ARBs on the formation of EETs and further metabolites, dihydroxyeicosatrienoic acids (DHETs), from AA via CYP2C8. In incubations with recombinant CYP2C8 in vitro, the inhibitory effects were compared by measuring EETs and DHETs by HPLC-MS/MS. Inhibition of AA metabolism by ARBs was detected in a concentration-dependent manner with IC50 values of losartan (42.7 µM), telmisartan (49.5 µM), irbesartan (55.6 µM), olmesartan (66.2 µM), candesartan (108 µM), and valsartan (279 µM). Losartan, telmisartan and irbesartan, which reportedly accumulate in the liver and kidneys, have stronger inhibitory effects than other ARBs. The lower concentration of EETs leads to less protective action on the cardiovascular system and a higher incidence of adverse effects such as sudden heart attack and myocardial infarction in patients taking ARBs.

Simultaneous Determination Method of Epoxyeicosatrienoic Acids and Dihydroxyeicosatrienoic Acids by LC-MS/MS System.

Epoxyeicosatrienoic acids (EETs) are produced primarily by CYPs from arachidonic acid (AA) and then further metabolized to the corresponding dihydroxyeicosatrienoic acids (DHETs). EETs play important roles in physiological processes such as regulating vasodilation and inflammation. Thus, the drug inhibition of CYP-mediated AA metabolism could reduce production of EETs, potentially resulting in adverse cardiovascular events. The aim of this study was to develop a simple method to simultaneously determine the concentrations of both EETs and DHETs using a conventional LC-MS/MS system to evaluate drug-endogenous substance interactions, including eicosanoids. Eight eicosanoids (5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, 5,6-DHET, 8,9-DHET, 11,12-DHET, and 14,15-DHET) were detected with their corresponding deuterium-labeled eicosanoids as internal standards. The samples were purified by solid-phase extraction columns. Liquid chromatographic separation was achieved on a C18 column. DHETs and EETs were eluted at 4-7 and 18-26 min, respectively. The weighted (1/y(2)) calibration curves were linear over a range of 5-2000 nmol/L for EETs and 2-2000 nmol/L for DHETs. In quality control (QC) samples, the recoveries of eicosanoids were 95.2-118%. The intra-day precisions were within 6% in all three QC samples, and the inter-day precisions were <16.7% at 50 nmol/L, <8.6% at 200 nmol/L, and <9.8% at 1000 nmol/L. We have applied this method for the determination of the eicosanoid levels in samples from incubation studies of AA by using human recombinant CYP enzyme (rCYP), and confirmed that the method has sensitivity sufficient for assessment of rCYP incubation study.