Application of physiologically based pharmacokinetic modeling to understand real-world outcomes in patients receiving imatinib for chronic myeloid leukemia.

We aimed to use physiologically based pharmacokinetic (PBPK) modeling and simulation to predict imatinib steady-state plasma exposure in patients with chronic myeloid leukemia (CML) to investigate variability in outcomes. A validated imatinib PBPK model (Simcyp Simulator) was used to predict imatinib AUCss , Css,min and Css,max for patients with CML (n = 68) from a real-world retrospective observational study. Differences in imatinib exposure were evaluated based on clinical outcomes, (a) Early Molecular Response (EMR) achievement and (b) occurrence of grade ≥3 adverse drug reactions (ADRs), using the Kruskal-Wallis rank sum test. Sensitivity analyses explored the influence of patient characteristics and drug interactions on imatinib exposure. Simulated imatinib exposure was significantly higher in patients who achieved EMR compared to patients who did not (geometric mean AUC0-24,ss 51.2 vs. 42.7 µg h mL-1 , p < 0.05; Css,min 1.1 vs. 0.9 µg mL-1 , p < 0.05; Css,max 3.4 vs. 2.8 µg mL-1 , p < 0.05). Patients who experienced grade ≥3 ADRs had a significantly higher simulated imatinib exposure compared to patients who did not (AUC0-24,ss 56.1 vs. 45.9 µg h mL-1 , p < 0.05; Css,min 1.2 vs. 1.0 µg mL-1 , p < 0.05; Css,max 3.7 vs. 3.0 µg mL-1 , p < 0.05). Simulations identified a range of patient (sex, age, weight, abundance of hepatic CYP2C8 and CYP3A4, α1 -acid glycoprotein concentrations, liver and kidney function) and medication-related factors (dose, concomitant CYP2C8 modulators) contributing to the inter-individual variability in imatinib exposure. Relationships between imatinib plasma exposure, EMR achievement and ADRs support the rationale for therapeutic drug monitoring to guide imatinib dosing to achieve optimal outcomes in CML.

Pharmacokinetic, Safety, and Tolerability Evaluations of Gepotidacin (GSK2140944) in Healthy Japanese Participants.

Gepotidacin is a novel, bactericidal, first-in-class triazaacenaphthylene antibiotic in late-phase development for uncomplicated urinary tract infection and uncomplicated urogenital gonorrhea. Two clinical studies were conducted to assess the pharmacokinetics (PK) and interethnic comparisons of oral gepotidacin (free-base and to-be-marketed mesylate formulations) administered as single doses ranging from 1500 to 3000 mg in fed and fasted states, and as 2 × 3000-mg doses given 12 hours apart under fed conditions in healthy participants of Japanese ancestry. Dose proportionality was observed in plasma exposures, and comparable area under the concentration-time curve (AUC) and maximum concentration were observed in fed and fasted states. Interethnic comparisons for Japanese versus non-Japanese participant data showed slightly higher plasma maximum concentration (7%-30%) yet similar plasma AUCs; slightly lower urine AUCs (11%-18%) were observed. The slightly higher plasma exposures in healthy Japanese versus White participants in the same study were attributed to lower mean body weights (64 kg versus ≈80 kg). Adverse events were primarily gastrointestinal, and when administered with food, gastrointestinal tolerability was improved. Overall, the gepotidacin PK and safety-risk profiles in healthy Japanese support potential evaluation of the global clinical doses in future studies.

Real-world efficacy and safety outcomes of imatinib treatment in patients with chronic myeloid leukemia: An Australian experience.

Tyrosine kinase inhibitors (TKI) have revolutionized the treatment of chronic myeloid leukemia (CML), but patients still experience treatment-limiting toxicities or therapeutic failure. To investigate the real-world use and outcomes of imatinib in patients with CML in Australia, a retrospective cohort study of patients with CML commencing imatinib (2001-2018) was conducted across two sites. Prescribing patterns, tolerability outcomes, and survival and molecular response were evaluated. 86 patients received 89 imatinib treatments. Dose modifications were frequently observed (12-month rate of 58%). At last follow-up, 62 patients (5-year rate of 55%) had permanently discontinued imatinib treatment, of which 44 switched to another TKI (5-year rate of 46%). Within 3 months of starting imatinib, 43% (95% CI, 32%-53%) of patients experienced imatinib-related grade ≥3 adverse drug reactions (ADRs). Higher comorbidity score, lower body weight, higher imatinib starting dose, and Middle Eastern or North African ancestry were associated with a higher risk of grade ≥3 ADR occurrence on multivariable analysis (MVA). Estimated overall survival and event-free survival rates at 3 years were 97% (95% CI, 92%-100%) and 81% (95% CI, 72%-92%), respectively. Cumulative incidence of major molecular response (MMR) at 3 years was 63% (95% CI, 50%-73%). On MVA, imatinib starting dose, ELTS score, BCR-ABL1 transcript type, pre-existing pulmonary disease, and potential drug-drug interactions were predictive of MMR. In conclusion, imatinib induced deep molecular responses that translated to good survival outcomes in a real-world setting, but was associated with a higher incidence of ADRs, dose modifications and treatment discontinuations than in clinical trials.

Randomized Trial of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of GSK2831781 in Healthy Japanese and White Participants.

This study investigated ethnic differences in the safety, tolerability, pharmacokinetics, and pharmacodynamics of GSK2831781, an anti-lymphocyte activation gene 3 (LAG3) monoclonal antibody, in healthy participants, and determined local tolerability and bioavailability following subcutaneous (SC) administration. A double-blind, randomized study of (A) single intravenous (IV) doses of GSK2831781 450 mg or placebo in Japanese and White participants; and (B) single SC doses of GSK2831781 150 or 450 mg, or placebo in White participants, was conducted. Blood samples for analyses were collected before dosing and over 112 days after dosing. GSK2831781 was well tolerated in Japanese and White participants after both IV and SC doses, with the adverse event profile in Japanese being consistent with other populations. There were no injection site adverse events. There was no evidence of differences in systemic exposure among Japanese and White participants. Systemic exposure did not vary with body weight. SC bioavailability was 76.5%, as estimated using population pharmacokinetic modeling. Full and sustained target engagement and evidence of LAG3+ cell depletion (≈53%-66%) were observed in both populations and after both administration routes. No evidence of reduced circulating regulatory T cells (CD4+ CD25+ CD127low FoxP3+ ) was observed. Following IV and SC administration, GSK2831781 depleted circulating LAG3+ T cells with no interethnic difference observed. There were no major impacts on circulating regulatory T cells.

A physiologically based pharmacokinetic model of clopidogrel in populations of European and Japanese ancestry: An evaluation of CYP2C19 activity.

Treatment response to clopidogrel is associated with CYP2C19 activity through the formation of the active H4 metabolite. The aims of this study were to develop a physiologically based pharmacokinetic (PBPK) model of clopidogrel and its metabolites for populations of European ancestry, to predict the pharmacokinetics in the Japanese population by CYP2C19 phenotype, and to investigate the effect of clinical and demographic factors. A PBPK model was developed and verified to describe the two metabolic pathways of clopidogrel (H4 metabolite, acyl glucuronide metabolite) for a population of European ancestry using plasma data from published studies. Subsequently, model predictions in the Japanese population were evaluated. The effects of CYP2C19 activity, fluvoxamine coadministration (CYP2C19 inhibitor), and population-specific factors (age, sex, BMI, body weight, cancer, hepatic, and renal dysfunction) on the pharmacokinetics of clopidogrel and its metabolites were then characterized. The predicted/observed ratios for clopidogrel and metabolite exposure parameters were acceptable (twofold acceptance criteria). For all CYP2C19 phenotypes, steady-state AUC0-τ of the H4 metabolite was lower for the Japanese (e.g., EM, 7.69 [6.26-9.45] ng·h/ml; geometric mean [95% CI]) than European (EM, 24.8 [20.4-30.1] ng·h/ml, p < .001) population. In addition to CYP2C19-poor metabolizer phenotype, fluvoxamine coadministration, hepatic, and renal dysfunction were found to reduce H4 metabolite but not acyl glucuronide metabolite concentrations. This is the first PBPK model describing the two major metabolic pathways of clopidogrel, which can be applied to populations of European and Japanese ancestry by CYP2C19 phenotype. The differences between the two populations appear to be determined primarily by the effect of varying CYP2C19 liver activity.

Clinical trial diversity: An opportunity for improved insight into the determinants of variability in drug response.

Although the number of countries participating in pivotal trials submitted to enable drug registration has nearly doubled over the past 25 years, there has not been a substantial increase in the diversity of clinical trial populations. In parallel, our understanding of factors that influence medicine response and variability has continued to evolve. The notion of intrinsic and extrinsic sources of variability has been embedded into different regulatory guidelines, including the recent guideline on the importance of enhancing the diversity of clinical trial populations. In addition to presenting the clinical and scientific reasons for ensuring that clinical trial populations represent the demographics of patient populations, this overview outlines the efforts of regulatory agencies, patient advocacy groups and clinical researchers to attain this goal through strategies to meet representation in recruitment targets and broaden eligibility criteria. Despite these efforts, challenges to participation in clinical trials remain, and certain groups continue to be underrepresented in development programmes. These challenges are amplified when the representativeness of specific groups may vary across countries and regions in a global clinical programme. Whilst enhanced trial diversity is a critical step towards ensuring that results will be representative of patient populations, a concerted effort is required to characterise further the factors influencing interindividual and regional differences in response for global populations. Quantitative clinical pharmacology principles should be applied to allow extrapolation of data across groups or regions as well as provide insight into the effect of patient-specific characteristics on a medicine's dose rationale and efficacy and safety profiles.

Physiologically-based pharmacokinetic model predictions of inter-ethnic differences in imatinib pharmacokinetics and dosing regimens.

AIMS: This study implements a physiologically-based pharmacokinetic (PBPK) modelling approach to investigate inter-ethnic differences in imatinib pharmacokinetics and dosing regimens. METHODS: A PBPK model of imatinib was built in the Simcyp Simulator (version 17) integrating in vitro drug metabolism and clinical pharmacokinetic data. The model accounts for ethnic differences in body size and abundance of drug-metabolising enzymes and proteins involved in imatinib disposition. Utility of this model for prediction of imatinib pharmacokinetics was evaluated across different dosing regimens and ethnic groups. The impact of ethnicity on imatinib dosing was then assessed based on the established range of trough concentrations (Css,min ). RESULTS: The PBPK model of imatinib demonstrated excellent predictive performance in describing pharmacokinetics and the attained Css,min in patients from different ethnic groups, shown by prediction differences that were within 1.25-fold of the clinically-reported values in published studies. PBPK simulation suggested a similar dose of imatinib (400-600 mg/d) to achieve the desirable range of Css,min (1000-3200 ng/mL) in populations of European, Japanese and Chinese ancestry. The simulation indicated that patients of African ancestry may benefit from a higher initial dose (600-800 mg/d) to achieve imatinib target concentrations, due to a higher apparent clearance (CL/F) of imatinib compared to other ethnic groups; however, the clinical data to support this are currently limited. CONCLUSION: PBPK simulations highlighted a potential ethnic difference in the recommended initial dose of imatinib between populations of European and African ancestry, but not populations of Chinese and Japanese ancestry.

The Extent and Impact of Variation in ADME Genes in Sub-Saharan African Populations.

Introduction: Investigating variation in genes involved in the absorption, distribution, metabolism, and excretion (ADME) of drugs are key to characterizing pharmacogenomic (PGx) relationships. ADME gene variation is relatively well characterized in European and Asian populations, but data from African populations are under-studied-which has implications for drug safety and effective use in Africa. Results: We identified significant ADME gene variation in African populations using data from 458 high-coverage whole genome sequences, 412 of which are novel, and from previously available African sequences from the 1,000 Genomes Project. ADME variation was not uniform across African populations, particularly within high impact coding variation. Copy number variation was detected in 116 ADME genes, with equal ratios of duplications/deletions. We identified 930 potential high impact coding variants, of which most are discrete to a single African population cluster. Large frequency differences (i.e., >10%) were seen in common high impact variants between clusters. Several novel variants are predicted to have a significant impact on protein structure, but additional functional work is needed to confirm the outcome of these for PGx use. Most variants of known clinical outcome are rare in Africa compared to European populations, potentially reflecting a clinical PGx research bias to European populations. Discussion: The genetic diversity of ADME genes across sub-Saharan African populations is large. The Southern African population cluster is most distinct from that of far West Africa. PGx strategies based on European variants will be of limited use in African populations. Although established variants are important, PGx must take into account the full range of African variation. This work urges further characterization of variants in African populations including in vitro and in silico studies, and to consider the unique African ADME landscape when developing precision medicine guidelines and tools for African populations.

Comparison of the Pharmacokinetics of RIPK1 Inhibitor GSK2982772 in Healthy Western and Japanese Subjects.

BACKGROUND AND OBJECTIVES: GSK2982772 is an oral small-molecule RIPK1 inhibitor with potential therapeutic efficacy in immune-mediated inflammatory diseases (IMIDs). An inter-ethnic comparison of GSK2982772 pharmacokinetics was conducted based on data from Western (Study 1) and Japanese subjects (Study 2). METHODS: Both studies were single-centre, randomised, double-blind, placebo-controlled studies with objectives to assess the safety and characterise the pharmacokinetics of GSK2982772. Western subjects in Study 1 (NCT03305419), Part A (N = 15), were randomly assigned to receive 120 mg three times daily (TID), 240 mg TID, or 360 mg twice daily (BID) doses of GSK2982772, or placebo (TID or BID) for 1 day. Part B subjects (N = 47) received GSK2982772 120 mg TID, 240 mg TID, or placebo TID for 14 days. Japanese subjects in Study 2 (N = 13) (NCT03590613) were randomly assigned to receive TID doses of GSK2982772 60, 120, 240 mg TID or placebo TID for 1 day. RESULTS: GSK2982772 was well tolerated and adverse events were generally mild. Maximum observed plasma drug concentration (Cmax), time to reach Cmax (Tmax), area under the plasma drug concentration versus time curve after the first GSK2982772 dose (AUC(0-7)) of 120 and 240 mg, and (AUC(0-24)) values for the 120 and 240 mg TID doses over a single day were similar in Japanese and Western subjects. CONCLUSIONS: The pharmacokinetics and tolerability of GSK2982772 were similar between Western and Japanese subjects, justifying inclusion of Japanese subjects in future global clinical studies to assess the therapeutic potential of RIPK1 inhibition for the treatment of IMIDs. Clinical Trials: NCT03305419 and NCT03590613 available from http://www.clinicaltrials.gov .

The Effects of Cruciferous Vegetable-Enriched Diets on Drug Metabolism: A Systematic Review and Meta-Analysis of Dietary Intervention Trials in Humans.

Relatively few studies exist in the literature that discuss the effects of diet on drug metabolism and how this can affect interindividual differences in systemic drug exposure. Several studies have investigated the effects of cruciferous vegetables (Cruciferae) or their constituents on drug-metabolizing activity, as these vegetables form an important part of many peoples' diets. In general, the ingestion of cruciferous vegetables is associated with induction of cytochrome P450 (CYP) 1A2 activity in vivo; however, there is contention between reports, and the clinical significance of potential diet-drug interactions remains unclear. This study reports a systematic review, critical appraisal, and meta-analysis of the published literature in this area, and discusses the clinical significance of Cruciferae-enriched diets in the context of diet-drug interactions. Twenty-three dietary intervention trials with drug metabolism end points were identified across Embase, Medline, and the Cochrane Controlled Register of Trials (CENTRAL). Cruciferous vegetables represented in the literature included broccoli, Brussels sprout, cabbage, cauliflower, radish, and watercress. A range of phase I and II drug-metabolizing enzymes and phenotyping metrics were represented in the literature. The meta-analyses performed demonstrated a significant effect on CYP1A2 and glutathione S-transferase-alpha (GST-α), with consumption of Cruciferae increasing the activities of these enzymes by 20-40% and 15-35%, respectively. The results herein suggest that patients undergoing pharmacotherapy with CYP1A2 or GST-α substrates could have altered drug exposure profiles if they regularly eat large or variable amounts of cruciferous vegetables. Recommendations regarding the design of future randomized, controlled trials to test hypotheses in this area are included.

An improved cytochrome P450 phenotyping cocktail with a simplified and highly sensitive UHPLC-MS/MS assay in human plasma.

Measuring in vivo changes in the drug metabolizing activity of cytochrome P450 (CYP) enzymes is critical to understanding and assessing drug-drug, drug-diet and drug-disease interactions. The sensitivity and specificity of ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) makes it an ideal tool for analyzing drugs and their metabolites in biological matrices, and has demonstrated utility in CYP phenotyping across varied applications. Published CYP phenotyping cocktail assays often require large plasma sample volumes (0.5-1 mL), have relatively low sensitivity and multi-step complex sample preparation and extraction procedures. Further, variability exists in the way that recovery and matrix effects are investigated and reported, and some studies fail to report these data altogether. Therefore, the aim of this study was to develop, validate and optimize a simplified assay for the probe drugs caffeine (metabolized by CYP1A2), omeprazole (CYP2C19), losartan (CYP2C9), dextromethorphan (CYP2D6), midazolam (CYP3A4) and their respective enzyme-specific metabolites in small volumes (100 µL) of human plasma, that addresses the issues noted. Analyte extraction involved protein precipitation with acetonitrile and solid-phase extraction (SPE). Samples were analyzed using an Agilent 1290 infinity LC system in tandem with 6460A triple quadrupole mass spectrometers. The assay met FDA guideline-recommended requirements for specificity, sensitivity (analyte LLOQs 0.78-23.4 ng/mL), accuracy (intra-day RE% nominal concentration 90.7-110.2%; inter-day RE% 87.0-110.5%) and precision (intra-day analyte RSD% 0.46-11.4%; inter-day RSD% 1.36-11.2%). Recovery and matrix effects were thoroughly investigated and excluded as potential interferers with assay performance. This assay has been used successfully to phenotype CYP activity in a human clinical trial participant. Importantly, the authors provide a contemporary commentary on commonly found issues in the CYP phenotyping cocktail assay literature, and make recommendations concerning best-practice approaches and the standardization of data reporting in this area.

Evaluation of the Pharmacokinetics, Safety, and Tolerability of a Single Oral Dose of Pyrimethamine in Healthy Male Subjects of Japanese and European Ancestry.

The pharmacokinetics of pyrimethamine have been evaluated in various populations but have not been reported in subjects of Japanese ancestry following administration as a single-agent tablet. Furthermore, although pyrimethamine pharmacokinetics after a single dose of the single-agent tablet studied in Western countries have been reported, these studies are old, and the ancestry of the subjects was not specified. Consequently, this study investigated the pharmacokinetics and safety of a single oral 50-mg dose of pyrimethamine in healthy male subjects of Japanese and European ancestry. Seven subjects of each ancestry group were administered pyrimethamine, along with calcium folinate. After absorption, pyrimethamine was eliminated, with a mean half-life of 122.8 hours in Japanese subjects and 99.5 hours in European subjects. The mean Cmax and AUC0-t were 433.8 ng/mL and 59.63 µg·h/mL in Japanese subjects and 372.7 ng/mL and 42.83 µg·h/mL in European subjects. No safety concerns were reported during the study. Although pyrimethamine exposure was slightly higher in subjects of Japanese than of European ancestry, a considerable overlap in the range of parameter values was observed. Considering the range of pyrimethamine exposure reported previously, difference in exposure observed in this study would not be considered of note.

The IMPACT Study - Single Inhaler Triple Therapy (FF/UMEC/VI) Versus FF/VI And UMEC/VI In Patients With COPD: Efficacy And Safety In A Japanese Population.

Purpose: The Informing the Pathway of COPD Treatment (IMPACT) study demonstrated that single-inhaler triple therapy fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) reduces moderate/severe exacerbation rates and improves lung function and health status versus FF/VI or UMEC/VI dual therapy in patients with symptomatic COPD and a history of exacerbations. This analysis evaluated the efficacy and safety of FF/UMEC/VI in patients enrolled in Japan. Patients and methods: IMPACT was a 52-week, randomized, double-blind, multicenter study comparing FF/UMEC/VI 100/62.5/25 µg with FF/VI 100/25 µg or UMEC/VI 62.5/25 µg in patients ≥40 years with symptomatic COPD and ≥1 moderate/severe exacerbation in the previous year. Endpoints included annual rate of on-treatment moderate/severe exacerbations (primary endpoint), time-to-first on-treatment moderate/severe exacerbation and change from baseline at Week 52 in trough FEV1, post-bronchodilator FEV1, St. George's Respiratory Questionnaire, and COPD Assessment Test score. Safety was also assessed. Results: The Japan subgroup accounted for only 4% (378/10,355) of the overall IMPACT intent-to-treat (ITT) population. In the Japan subgroup, FF/UMEC/VI reduced the annual rate of on-treatment moderate/severe exacerbations by 15% (95% CI: -20, 40) versus FF/VI (compared with 15% [10, 20] in the ITT) and 36% (95% CI: 6, 57) versus UMEC/VI (compared with 25% [19, 30] in the ITT). FF/UMEC/VI reduced moderate/severe exacerbation risk (time-to-first), improved lung function and health status at Week 52 versus both dual therapies. These results were in the same direction and of a generally similar magnitude to those seen in the overall ITT population. No new safety signals were identified in the Japan subgroup compared with the ITT population. Pneumonia incidence was higher with FF/UMEC/VI and FF/VI versus UMEC/VI. Conclusion: These results highlight the favorable benefit-risk profile of FF/UMEC/VI single-inhaler triple therapy compared with FF/VI or UMEC/VI dual therapy in patients in Japan with symptomatic COPD and ≥1 exacerbation in the prior year.

Characterization of ADME gene variation in 21 populations by exome sequencing.

OBJECTIVE: Proteins involving absorption, distribution, metabolism, and excretion (ADME) play a critical role in drug pharmacokinetics. The type and frequency of genetic variation in the ADME genes differ among populations. The aim of this study was to systematically investigate common and rare ADME coding variation in diverse ethnic populations by exome sequencing. MATERIALS AND METHODS: Data derived from commercial exome capture arrays and next-generation sequencing were used to characterize coding variation in 298 ADME genes in 251 Northeast Asians and 1181 individuals from the 1000 Genomes Project. RESULTS: Approximately 75% of the ADME coding sequence was captured at high quality across the joint samples harboring more than 8000 variants, with 49% of individuals carrying at least one 'knockout' allele. ADME genes carried 50% more nonsynonymous variation than non-ADME genes (P=8.2×10) and showed significantly greater levels of population differentiation (P=7.6×10). Out of the 2135 variants identified that were predicted to be deleterious, 633 were not on commercially available ADME or general-purpose genotyping arrays. Forty deleterious variants within important ADME genes, with frequencies of at least 2% in at least one population, were identified as candidates for future pharmacogenetic studies. CONCLUSION: Exome sequencing was effective in accurately genotyping most ADME variants important for pharmacogenetic research, in addition to identifying rare or potentially de novo coding variants that may be clinically meaningful. Furthermore, as a class, ADME genes are more variable and less sensitive to purifying selection than non-ADME genes.

Ethnic sensitivity assessment of fluticasone furoate/vilanterol in East Asian asthma patients from randomized double-blind multicentre Phase IIb/III trials.

BACKGROUND: Fluticasone furoate (FF)/vilanterol (VI) is a once daily (OD) inhaled corticosteroid/long-acting ß2-agonist combination asthma therapy approved in Japan and the EU. FF/VI efficacy and safety data from asthma studies including patients in East Asia were evaluated to assess ethnic sensitivity. METHODS: Randomized, double-blind, multicenter Phase IIb/III trials were assessed. Change from baseline relative to placebo or twice-daily fluticasone propionate 500 µg in trough FEV1 was compared between patients from Japan (N = 148) and Not-Japan (N = 3,066; three studies). Adverse events (AEs), laboratory results, and electrocardiograms were compared between patients from Japan + Korea (N = 188) and Not-Japan + Korea (N = 3,840; five studies). RESULTS: For trough FEV1, improvements from baseline (least-squares mean difference [95% confidence interval]) were reported for FF/VI 100/25 µg OD versus placebo at Week 12 (Japan: 0.323 L [0.104-0.542]; Not-Japan: 0.168 L [0.095-0.241]). Improvements from baseline (least-squares mean change [standard error]) were reported with FF/VI 200/25 µg OD at Week 24 (Japan: 0.355 L [0.1152]; Not-Japan: 0.396 L [0.0313]). A greater proportion of patients from Japan + Korea versus Not-Japan + Korea reported AEs in all treatment arms including placebo (FF/VI 100/25 µg: 79% versus 57%; FF/VI 200/25 µg: 64% versus 45%; placebo: 41% versus 23%). There were no notable differences in treatment-related or class-related AEs. No clinically significant changes in electrocardiogram assessments or statistically significant differences in 24 h urinary cortisol excretion were observed between the Japan + Korea and Not-Japan + Korea cohorts. CONCLUSIONS: Good efficacy and an acceptable safety profile were observed for FF/VI 100/25 µg and 200/25 µg OD in East Asian asthma patients; these globally recommended doses are appropriate for asthma patients in Japan. TRIAL REGISTRATION: Clinicaltrials.gov registration numbers: NCT01165138 , NCT01134042 , NCT01086384 , NCT00603278 , NCT00603382 .

Single and Multiple Dose Pharmacokinetics, Pharmacodynamics and Safety of the Novel Lipoprotein-Associated Phospholipase A2 Enzyme Inhibitor Darapladib in Healthy Chinese Subjects: An Open Label Phase-1 Clinical Trial.

BACKGROUND AND OBJECTIVES: Darapladib is a lipoprotein-associated phospholipase A2 (Lp-PLA2) inhibitor. This study evaluated the pharmacokinetics, pharmacodynamics and safety of darapladib in healthy Chinese subjects. METHODS: Twenty-four subjects received darapladib 160 mg orally, approximately 1 hour after a standard breakfast, as a single dose and once daily for 28 days. Non-compartmental methods were used to determine the single and multiple dose pharmacokinetics of darapladib and its metabolite SB-553253. Repeat dose Lp-PLA2 activity and safety were evaluated. RESULTS: Systemic exposure (AUC(0-T), Cmax geometric mean (CVb%)) of darapladib was higher after multiple-dosing (519 ng.h/mL (33.3%), 34.4 ng/mL (49.9%)) compared to single-dose administration (153 ng.h/mL (69.0%), 17.9 ng/mL (55.2%). The steady-state accumulation ratio was less than unity (Rs = 0.80), indicating time-dependent pharmacokinetics of darapladib. Darapladib steady-state was reached by Day 14 of once daily dosing. Systemic exposure to SB-553253 was lower than darapladib with median (SB-553253: darapladib) ratios for AUC(0-τ) of 0.0786 for single dose and 0.0532 for multiple dose administration. On Day 28, pre-dose and maximum inhibition of Lp-PLA2 activity was approximately 70% and 75% relative to the baseline value, respectively and was dependent of darapladib concentration. The most common adverse events (≥ 21% subjects) were abnormal faeces, abnormal urine odour, diarrhoea and nasopharyngitis. CONCLUSION: Darapladib 160 mg single and repeat doses were profiled in healthy Chinese subjects. Single dose systemic exposure to darapladib in healthy Chinese subjects was consistent with that observed previously in Western subjects whereas steady-state systemic exposure was approximately 65% higher in Chinese than Western subjects. The Lp-PLA2 activity and adverse event profile were similar in healthy Chinese and previous reports in Western subjects. Ethnic-specific dose adjustment of darapladib is not considered necessary for the Chinese population. TRIAL REGISTRATION: ClinicalTrials.gov NCT02000804.

A pharmacometric approach to investigate the impact of methylxanthine abstinence and caffeine consumption on CYP1A2 activity.

This study aimed to investigate the impact of methylxanthine abstinence (MA) periods on CYP1A2 activity in individuals with varying levels of caffeine consumption through development of a population pharmacokinetic model of caffeine and its major metabolite paraxanthine. This study developed and evaluated a mixed-effects pharmacokinetic model for caffeine and paraxanthine concentration-time data derived from a sequential single-dose cross-over study in healthy male volunteers (n = 30) who received oral 100 mg caffeine doses. Participants received caffeine with and without a MA period. Participants were classified as low (0-100 mg/d), medium (100-200 mg/d), or high (>200 mg/d) caffeine consumers (LCCs, MCCs, or HCCs, respectively). All caffeine and paraxanthine concentration-time data were simultaneously modeled. Caffeine pharmacokinetics was described by a two-compartment model with first-order absorption and two first-order elimination pathways. Paraxanthine was described by a one-compartment model with first-order absorption and elimination. Among LCCs (n = 16) and MCCs (n = 9), there was no difference in the mean (95% confidence interval) total apparent caffeine clearance (CL) between the MA period [LCCs: 6.88 (5.61-8.16 l/h); MCCs: 10.09 (7.57-12.60 l/h)] versus the no MA period [LCCs: 6.22 (4.97-7.46 l/h); MCCs: 9.68 (7.12-12.24 l/h)]. The mean CL among HCCs (n = 5) was considerably higher in the MA period [10.48 (5.62-15.33 l/h)] compared with the no MA period [6.30 (3.40-9.20 l/h)] (P < 0.05). The decrease in CL in the no MA period among HCC appears to be due to alternative caffeine elimination pathways, rather than CYP1A2.

Considering CYP1A2 phenotype and genotype for optimizing the dose of olanzapine in the management of schizophrenia.

INTRODUCTION: Schizophrenia, a mental disorder, is a debilitating condition which typically strikes young people in their early 20's. Antipsychotic medications are widely prescribed for the treatment of schizophrenia however a balancing act is necessary to provide the correct dose to each patient. It is suggested that a large number of patients discontinue antipsychotic pharmacotherapy because the treatments provided do not always reduce the positive symptoms of the disease, while many have adverse effects on the patients. This implies that neither the incorrect drug nor the optimal dosage for that patient is achieved. AREAS COVERED: The current review investigates variability in response to olanzapine with a specific focus on the common intrinsic and extrinsic factors that influence both olanzapine and CYP1A2 activity. Furthermore, the authors discuss the utilization of phenotyping and genotyping of CYP1A2 and their potential utility in clinical practice for olanzapine dosing regimens. The authors also consider the potential of pharmacometrics compared to pharmacogenomics as a tool to personalize medicine. EXPERT OPINION: Careful consideration must be given to the impact of a genetic variant on the disposition of a drug prior to implementing genetic 'tests' to determine response. CYP1A2 phenotypic assessment can yield important information regarding the disposition of olanzapine; however, it relies on the accuracy of the metric and the minimal impact of other metabolic pathways. The application of pharmacometrics provides an effective method to establish covariates that significantly influence olanzapine disposition which can incorporate phenotype and/or genotype.

Diurnal variation in CYP1A2 enzyme activity in South Asians and Europeans.

OBJECTIVES: Response to some medications can depend on time of administration throughout the day. This study investigated diurnal variation in cytochrome P450 1A2 (CYP1A2) activity in people of South Asian and European ancestry. METHODS: CYP1A2 activity was determined using the 4-h paraxanthine/caffeine saliva concentration ratio following a 100-mg oral dose of caffeine in healthy individuals of South Asian (n = 11) and European (n = 12) ancestry. Caffeine was administered in the morning and evening on three separate days. KEY FINDINGS: A higher CYP1A2 activity (mean ± standard deviation) was found in the morning (0.52 ± 0.17) when compared with evening (0.47 ± 0.17) (n = 23, P < 0.05). When stratified by ethnicity, a difference in CYP1A2 activity was found in the morning (0.43 ± 0.13) and evening (0.35 ± 0.05) for South Asians (P < 0.05), but not in Europeans (0.61 ± 0.15 and 0.56 ± 0.17, respectively). The intra-individual variation in CYP1A2 activity (% coefficient of variation, CV) of CYP1A2 activity ranged from 2.9 to 40.0% in the morning and 1.3 to 38.8% in the evening. Inter-individual CV was 32.1 ± 5.0% and 30.9 ± 6.4% in South Asians and Europeans, respectively. CONCLUSIONS: This study observed diurnal variation of CYP1A2 activity in South Asians, resulting in lower enzyme activity in the evening.