CYP2C19 genotype has a major influence on labetalol pharmacokinetics in healthy male Chinese subjects

Pharmacokinetic Characterization of Labetalol in Pregnancy (The CLIP Study): A Prospective Observational Longitudinal Pharmacokinetic/Pharmacodynamic Cohort Study During Pregnancy and Postpartum

Background/Objectives: Hypertensive disorders of pregnancy are a leading cause of pregnancy-related deaths in the United States, accounting for 7% of maternal mortality. Labetalol and nifedipine are the first-line drugs for the management of hypertension in pregnancy, but there are little data guiding the choice of one drug over the other. The current pilot longitudinal study aims to characterize the pharmacokinetics (PK) and pharmacodynamics (PD) of labetalol stereoisomers throughout pregnancy and postpartum. Methods: This is a single-center clinical study recruiting up to 40 pregnant individuals ≥ 18 years of age at the time of enrollment, taking labetalol as per the standard of care. The exclusion criteria include any pathophysiology impacting the PK of labetalol, e.g., liver failure. Maternal plasma, urine, amniotic fluid, cord blood, and breast milk will be collected, and labetalol stereoisomers will be measured using a validated LC-MS/MS assay. Heart rate and blood pressure will be measured as the PD endpoints. These may be assessed throughout a participant's dosing interval at scheduled PK study visits, which will occur every 6-10 weeks during pregnancy, at delivery, during the 1st week postpartum, and up to 20 weeks postpartum. The primary aim is to characterize the PK and PD of labetalol during pregnancy and in the postpartum period. The secondary aim is to determine the extent of breast milk excretion of and infant exposure to labetalol from breast milk. The data will be analyzed using population PK modeling to evaluate the PK/PD relationship and ultimately develop trimester-specific dosing recommendations. Results/Conclusions: To our knowledge, this is the first study aiming to characterize the PK of labetalol stereoisomers across pregnancy and postpartum, utilizing individual stereoisomer data to evaluate the PK/PD relationship, and collecting postpartum samples, including breast milk, to model infant exposure to labetalol through breast milk. This study will provide important PK/PD data and knowledge which will be combined with large multi-center clinical trial data to develop trimester-specific dosing regimens for anti-hypertensive agents.

Physiologically Based Pharmacokinetic Modeling for Multiple Oral Administration Labetalol in Pregnant Women

BACKGROUND

Labetalol has an irreplaceable role in treating Hypertensive disorders of pregnancy (HDP), a common disease during pregnancy with a prevalence of 5.2-8.2%. However, there were big differences in dosage regimens between various guidelines.

PURPOSE

A physiologically-based pharmacokinetics (PBPK) model was established and validated to evaluate the existing oral dosage regimens, and to compare the difference in plasma concentration between pregnant and non-pregnant women.

METHODS

First, non-pregnant woman models with specific plasma clearance or enzymatic metabolism (UGT1A1, UGT2B7, CYP2C19) were established and validated. For CYP2C19, slow, intermediate, and rapid metabolic phenotypes were considered. Then, a pregnant model with proper structure and parameters adjustment was established and validated against the multiple oral administration data.

RESULTS

The predicted labetalol exposure captured the experimental data well. The following simulations with criteria lowering 15 mmHg blood pressure (corresponding to around 108 ng/ml plasma labetalol) found that the maximum daily dosage in the Chinese guideline may be insufficient for some severe HDP patients. Moreover, similar predicted steady-state trough plasma concentration was found between the maximum daily dosage in the American College of Obstetricians and Gynecologists (ACOG) guideline, 800 mg Q8h and a regimen of 200 mg Q6h. Simulations comparing non-pregnant and pregnant women found that the difference in labetalol exposure highly depended on the CYP2C19 metabolic phenotype.

CONCLUSIONS

In summary, this work initially established a PBPK model for multiple oral administration of labetalol for pregnant women. This PBPK model may lead to personalized labetalol medication in the future.

(-)-N-3-Benzylphenobarbital Is Superior to Omeprazole and (+)-N-3-Benzylnirvanol as a CYP2C19 Inhibitor in Suspended Human Hepatocytes

Early assessment of metabolism pathways of new chemical entities guides the understanding of drug-drug interactions. Selective enzyme inhibitors are indispensable in CYP reaction phenotyping. The most commonly applied CYP2C19 inhibitor, omeprazole, lacks selectivity. Two promising alternatives, (+)-N-3-benzylnirvanol and (-)-N-3-benzylphenobarbital, are already used as CYP2C19 inhibitors in some in vitro studies with suspended human hepatocytes. However, a full validation proving their suitability in terms of CYP and non-CYP selectivity has not been presented in literature. The present study provides a thorough comparison between omeprazole, (+)-N-3-benzylnirvanol, and (-)-N-3-benzylphenobarbital in terms of potency and selectivity and shows the superiority of (-)-N-3-benzylphenobarbital as a CYP2C19 inhibitor in suspended human hepatocytes. Furthermore, we evaluated the application of (-)-N-3-benzylphenobarbital to predict the in vivo contribution of CYP2C19 to drug metabolism [fraction metabolized (fm) of CYP2C19, fmCYP2C19]. A set of 10 clinically used CYP2C19 substrates with reported in vivo fmCYP2C19 data was evaluated. fmCYP2C19, which was predicted using data from suspended human hepatocyte incubations, underestimated the in vivo fmCYP2C19 The use of a different hepatocyte batch with a different CYP3A4/CYP2C19 activity ratio showed the impact of intrinsic CYP activities on the determination of fmCYP2C19 Overall, this study confirms the selective CYP2C19 inhibition by (-)-N-3-benzylphenobarbital over other CYP isoforms (CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2D6, and CYP3A4) and clinically relevant non-CYP enzymes [aldehyde oxidase, flavin-containing monooxygenase 3, N-acetyltransferase 2, uridine diphosphate glucuronosyltransferase (UGT) 1A1, UGT1A4, UGT2B7, UGT2B15] in suspended human hepatocytes. (-)-N-3-benzylphenobarbital is therefore the preferred CYP2C19 inhibitor to assess fmCYP2C19 in suspended human hepatocytes in comparison with omeprazole and (+)-N-3-benzylnirvanol. SIGNIFICANCE STATEMENT: (-)-N-3-Benzylphenobarbital is a more potent and selective inhibitor of CYP2C19 in suspended human hepatocytes than omeprazole and (+)-N-3-benzylnirvanol. (-)-N-3-Benzylphenobarbital can be used to predict the fraction metabolized by CYP2C19 in suspended human hepatocytes.

Heart Failure Clinical Trials in East and Southeast Asia: Understanding the Importance and Defining the Next Steps

Heart failure (HF) is a major and increasing global public health problem. In Asia, aging populations and recent increases in cardiovascular risk factors have contributed to a particularly high burden of HF, with outcomes that are poorer than those in the rest of the world. Representation of Asians in landmark HF trials has been variable. In addition, HF patients from Asia demonstrate clinical differences from patients in other geographic regions. Thus, the generalizability of some clinical trial results to the Asian population remains uncertain. In this article, we review differences in HF phenotype, HF management, and outcomes in patients from East and Southeast Asia. We describe lessons learned in Asia from recent HF registries and clinical trial databases and outline strategies to improve the potential for success in future trials. This review is based on discussions among scientists, clinical trialists, industry representatives, and regulatory representatives at the CardioVascular Clinical Trialist Asia Forum in Singapore on July 4, 2014.

Polymorphisms in genes involved in the absorption, distribution, metabolism, and excretion of drugs in the Kazakhs of Kazakhstan

BACKGROUND

Studies of genes involved in the absorption, distribution, metabolism, and excretion (ADME) of drugs are crucial to the development of therapeutics in clinical medicine. Such data provide information that may improve our understanding of individual differences in sensitivity or resistance to certain drugs, thereby helping to avoid adverse drug reactions (ADRs) in patients and improve the quality of therapies. Here, we aimed to analyse single nucleotide polymorphisms (SNPs) involved in the ADME of multiple drugs in Kazakhs from Kazakhstan.

RESULTS

A total of 158 SNPs involved in the ADME of various drugs were studied. We analysed 320 Kazakh DNA samples using OpenArray genotyping. Of the 158 SNPs, 75 were not found in heterozygous or homozygous variants. Comparative analysis among Kazakhs and world populations showed a fairly high percentage of population differentiation.

CONCLUSION

These results provide further information for pharmacogenetic databases and may contribute to the development of personalized approaches and safer therapies for the Kazakh population. Moreover, these data provide insights into the different racial groups that may have contributed to the Kazakh population.

Is personalized medicine achievable in obstetrics?

Personalized medicine seeks to identify the right dose of the right drug for the right patient at the right time. Typically, individualization of therapy is based on the pharmacogenomic makeup of the individual and environmental factors that alter drug disposition and response. In addition to these factors, during pregnancy, a woman's body undergoes many changes that can impact the therapeutic efficacy of medications. Yet, there is minimal research regarding personalized medicine in obstetrics. Adoption of pharmacogenetic testing into the obstetrical care is dependent on evidence of analytical validity, clinical validity, and clinical utility. Here, we briefly present information regarding the potential utility of personalized medicine for treating the obstetric patient for pain with narcotics, hypertension, and preterm labor, and discuss the impediments of bringing personalized medicine to the obstetrical clinic.