Pregnancy-related effects on nelfinavir-M8 pharmacokinetics: a population study with 133 women

Need for a Standardized Translational Drug Development Platform: Lessons Learned from the Repurposing of Drugs for COVID-19

In the absence of drugs to treat or prevent COVID-19, drug repurposing can be a valuable strategy. Despite a substantial number of clinical trials, drug repurposing did not deliver on its promise. While success was observed with some repurposed drugs (e.g., remdesivir, dexamethasone, tocilizumab, baricitinib), others failed to show clinical efficacy. One reason is the lack of clear translational processes based on adequate preclinical profiling before clinical evaluation. Combined with limitations of existing in vitro and in vivo models, there is a need for a systematic approach to urgent antiviral drug development in the context of a global pandemic. We implemented a methodology to test repurposed and experimental drugs to generate robust preclinical evidence for further clinical development. This translational drug development platform comprises in vitro, ex vivo, and in vivo models of SARS-CoV-2, along with pharmacokinetic modeling and simulation approaches to evaluate exposure levels in plasma and target organs. Here, we provide examples of identified repurposed antiviral drugs tested within our multidisciplinary collaboration to highlight lessons learned in urgent antiviral drug development during the COVID-19 pandemic. Our data confirm the importance of assessing in vitro and in vivo potency in multiple assays to boost the translatability of pre-clinical data. The value of pharmacokinetic modeling and simulations for compound prioritization is also discussed. We advocate the need for a standardized translational drug development platform for mild-to-moderate COVID-19 to generate preclinical evidence in support of clinical trials. We propose clear prerequisites for progression of drug candidates for repurposing into clinical trials. Further research is needed to gain a deeper understanding of the scope and limitations of the presented translational drug development platform.

Quetiapine dose optimisation during gestation: a pharmacokinetic modelling study

Objectives

The second-generation antipsychotic quetiapine has been demonstrated to undergo gestation-related changes in pharmacokinetics. This study applied pharmacokinetic modelling principles to investigate the mechanism of these changes and to propose new dosing strategies to counteract these changes.

Methods

A pharmacokinetic modelling approach was implemented using virtual population groups. Changes in quetiapine trough plasma concentration during gestation were quantified across all trimesters, and dose adjustment strategies were applied to counteract these changes by targeting a therapeutic range of 50–500 ng/ml throughout gestation.

Key findings

The application of the model during gestation predicted a decrease in trough concentration. A maximum decrease of 58% was predicted during trimester 2, and being associated with a statistically significant decrease in oral clearance at gestation week 25, 204 l/h ± 100.8 l/h compared with non-pregnant subjects, 121.9 l/h ± 51.8 l/h. A dosing optimisation strategy identified that dose increases to 500–700 mg twice daily would result in 32–55% of subjects possessing trough concentration in excess of 50 ng/ml.

Conclusions

Quetiapine doses in pregnancy should be increased to 500–700 mg twice daily to counteract a concomitant increase in metabolic clearance, increase in volume of distribution and decrease in plasma protein binding.

Pharmacokinetics of Increased Nelfinavir Plasma Concentrations in Women During Pregnancy and Postpartum

This study aims to evaluate the safety, acceptability, and pharmacokinetics (PK) of an increased dose of nelfinavir (NFV) during the third trimester of pregnancy. The study was registered as part of the International Maternal Pediatric Adolescent AIDS Clinical Trials network (IMPAACT-P1026s), an ongoing multicenter prospective cohort study of antiretroviral PK during pregnancy (NCT00042289). NFV intensive PK evaluations were performed at steady state during the third trimester of pregnancy and 2-3 weeks postpartum. Plasma concentrations of NFV and its active metabolite, hydroxyl-tert-butylamide (M8) were measured using high-performance liquid chromatography with ultraviolet detection. A total of 18 women are included in the analysis. NFV area under the concentration-time curve (AUC) with the increased dose during the third trimester was nearly identical to the standard dose postpartum, with a geometric mean ratio for third trimester to postpartum AUC of 0.98 (90%CI 0.71-1.35). Despite the increased dose, M8 AUC was lower during the third trimester compared to postpartum (0.53, IQR [0.38-0.75]), as was the M8/NFV AUC ratio (0.51, IQR [0.42-0.63]). NFV AUC_0-12 was above target in 15 of 18 (83%) of participants during the third trimester compared to 14 of 16 (88%) postpartum. No major safety concerns were noted. Increasing the NFV dose to 1875 mg twice daily during the third trimester achieved similar concentrations postpartum compared to standard dosing (1250 mg twice daily). Increased NFV dose regimens may still have some benefit to human immunodeficiency virus (HIV)-positive pregnant women living in countries where novel protease inhibitors are currently unavailable or in individuals who are intolerant to ritonavir-boosted HIV medications.

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

BACKGROUND

Women are commonly prescribed a variety of medications during pregnancy. As most organ systems are affected by the substantial anatomical and physiological changes that occur during pregnancy, it is expected that pharmacokinetics (PK) (absorption, distribution, metabolism, and excretion of drugs) would also be affected in ways that may necessitate changes in dosing schedules. The objective of this study was to systematically identify existing clinically relevant evidence on PK changes during pregnancy.

METHODS AND FINDINGS

Systematic searches were conducted in MEDLINE (Ovid), Embase (Ovid), Cochrane Central Register of Controlled Trials (Ovid), and Web of Science (Thomson Reuters), from database inception to August 31, 2015. An update of the search from September 1, 2015, to May 20, 2016, was performed, and relevant data were added to the present review. No language or date restrictions were applied. All publications of clinical PK studies involving a group of pregnant women with a comparison to nonpregnant participants or nonpregnant population data were eligible to be included in this review. A total of 198 studies involving 121 different medications fulfilled the inclusion criteria. In these studies, commonly investigated drug classes included antiretrovirals (54 studies), antiepileptic drugs (27 studies), antibiotics (23 studies), antimalarial drugs (22 studies), and cardiovascular drugs (17 studies). Overall, pregnancy-associated changes in PK parameters were often observed as consistent findings among many studies, particularly enhanced drug elimination and decreased exposure to total drugs (bound and unbound to plasma proteins) at a given dose. However, associated alterations in clinical responses and outcomes, or lack thereof, remain largely unknown.

CONCLUSION

This systematic review of pregnancy-associated PK changes identifies a significant gap between the accumulating knowledge of PK changes in pregnant women and our understanding of their clinical impact for both mother and fetus. It is essential for clinicians to be aware of these unique pregnancy-related changes in PK, and to critically examine their clinical implications.

Pharmacokinetics of drugs in pregnancy

Pregnancy is a complex state where changes in maternal physiology have evolved to favor the development and growth of the placenta and the fetus. These adaptations may affect preexisting disease or result in pregnancy-specific disorders. Similarly, variations in physiology may alter the pharmacokinetics or pharmacodynamics that determines drug dosing and effect. It follows that detailed pharmacologic information is required to adjust therapeutic treatment strategies during pregnancy. Understanding both pregnancy physiology and the gestation-specific pharmacology of different agents is necessary to achieve effective treatment and limit maternal and fetal risk. Unfortunately, most drug studies have excluded pregnant women based on often-mistaken concerns regarding fetal risk. Furthermore, over two-thirds of women receive prescription drugs while pregnant, with treatment and dosing strategies based on data from healthy male volunteers and non-pregnant women, and with little adjustment for the complex physiology of pregnancy and its unique disease states. This review will describe basic concepts in pharmacokinetics and their clinical relevance and highlight the variations in pregnancy that may impact the pharmacokinetic properties of medications.

Therapeutic drug monitoring in HIV-infected pregnant women with a focus on protease inhibitors

The goals of HIV therapy in pregnant patients are to ensure health of mother and to prevent mother to child transmission of HIV to the unborn child. Pregnancy is a time of significant physiological alterations that affect all pharmacological aspects of the antiretroviral (ARV) drugs. Studies point toward lower levels of ARVs in maternal blood especially during late stages of pregnancy. Therapeutic drug monitoring is a strategy to ensure that maternal blood contains adequate level of ARVs to achieve these targets. Pharmacokinetics and therapeutic drug monitoring studies of protease inhibitors are reviewed in this article with emphasis on darunavir which is a newer protease inhibitor gaining popularity as a therapeutic choice in pregnant patients.

Pregnancy and pharmacogenomics in the context of drug metabolism and response

It is well-known that profound physiological and biochemical changes occur throughout the course of pregnancy. At the same time, the role of pharmacogenomics in modulating the metabolism and response profile to numerous medications has been elucidated. Yet, the clinical impact of pharmacogenomics during pregnancy is less well understood. We present an overview of factors modulating the pharmacokinetics and pharmacodynamics of medications throughout the time span of pregnancy while providing insights on how pharmacogenomics may contribute to interindividual variability in drug metabolism and response amongst pregnant women.

HIV protease inhibitors in pregnancy : pharmacology and clinical use

The impact of antiretroviral therapy (ART) on the natural history of HIV-1 infection has resulted in dramatic reductions in disease-associated morbidity and mortality. Additionally, the epidemiology of HIV-1 infection worldwide is changing, as women now represent a substantial proportion of infected adults. As more highly effective and tolerable antiretroviral regimens become available, and as the prevention of mother-to-child transmission becomes an attainable goal in the management of HIV-infected individuals, more and more HIV-positive women are choosing to become pregnant and have children. Consequently, it is important to consider the efficacy and safety of antiretroviral agents in pregnancy. Protease inhibitors are a common class of medication used in the treatment of HIV-1 infection and are increasingly being used in pregnancy. However, several studies have raised concerns regarding pharmacokinetic alterations in pregnancy, particularly in the third trimester, which results in suboptimal drug concentrations and a theoretically higher risk of virologic failure and perinatal transmission. Drug level reductions have been observed with each individual protease inhibitor and dose adjustments in pregnancy are suggested for certain agents. Furthermore, studies have also raised concerns regarding the safety of protease inhibitors in pregnancy, particularly as they may increase the risk of pre-term birth and metabolic disturbances. Overall, protease inhibitors are safe and effective for the treatment of HIV-infected pregnant women. Specifically, ritonavir-boosted lopinavir- and atazanavir-based regimens are preferred in pregnancy, while ritonavir-boosted darunavir- and saquinavir-based therapies are reasonable alternatives. This paper reviews the use of protease inhibitors in pregnancy, focusing on pharmacokinetic and safety considerations, and outlines the recommendations for use of this class of medication in the HIV-1-infected pregnant woman.

Interpreting tacrolimus concentrations during pregnancy and postpartum

Pregnancy after solid organ transplantation, although considered high risk for maternal, fetal, and neonatal complications, has been quite successful. Tacrolimus pharmacokinetic changes during pregnancy make interpretation of whole blood trough concentrations particularly challenging. There are multiple factors that can increase the fraction of unbound tacrolimus, including but not limited to low albumin concentration and low red blood cell count. The clinical titration of dosage to maintain whole blood tacrolimus trough concentrations in the usual therapeutic range can lead to elevated unbound concentrations and possibly toxicity in pregnant women with anemia and hypoalbuminemia. Measurement of plasma or unbound tacrolimus concentrations for pregnant women might better reflect the active form of the drug, although these are technically challenging and often unavailable in usual clinical practice. Tacrolimus crosses the placenta with in utero exposure being approximately 71% of maternal blood concentrations. The lower fetal blood concentrations are likely due to active efflux transport of tacrolimus from the fetus toward the mother by placental P-glycoprotein. To date, tacrolimus has not been linked to congenital malformations but can cause reversible nephrotoxicity and hyperkalemia in the newborn. In contrast, very small amounts of tacrolimus are excreted in the breast milk and are unlikely to elicit adverse effects in the nursing infant.

Pharmacokinetics of tacrolimus during pregnancy

BACKGROUND

Information on the pharmacokinetics of tacrolimus during pregnancy is limited to case reports despite the increasing number of pregnant women being prescribed tacrolimus for immunosuppression.

METHODS

Blood, plasma, and urine samples were collected over 1 steady-state dosing interval from women treated with oral tacrolimus during early to late pregnancy (n = 10) and postpartum (n = 5). Total and unbound tacrolimus as well as metabolite concentrations in blood and plasma were assayed by a validated liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) method. A mixed-effect linear model was used for comparison across gestational age and using postpartum as the reference group.

RESULTS

The mean oral clearance (CL/F) based on whole-blood tacrolimus concentration was 39% higher during mid-pregnancy and late pregnancy compared with postpartum (47.4 ± 12.6 vs. 34.2 ± 14.8 L/h, P < 0.03). Tacrolimus-free fraction increased by 91% in plasma (f(P)) and by 100% in blood (f(B)) during pregnancy (P = 0.0007 and 0.002, respectively). Increased fP was inversely associated with serum albumin concentration (r = -0.7, P = 0.003), which decreased by 27% during pregnancy. Pregnancy-related changes in f(P) and f(B) contributed significantly to the observed gestational increase in tacrolimus whole-blood CL/F (r² = 0.36 and 0.47, respectively, P < 0.01). In addition, tacrolimus whole-blood CL/F was inversely correlated with both hematocrit and red blood cell counts, suggesting that binding of tacrolimus to erythrocytes restricts its availability for metabolism. Treating physicians increased tacrolimus dosages in study participants during pregnancy by an average of 45% to maintain tacrolimus whole-blood trough concentrations in the therapeutic range. This led to striking increases in unbound tacrolimus trough concentrations and unbound area under the concentration-time curve, by 112% and 173%, respectively, during pregnancy (P = 0.02 and 0.03, respectively).

CONCLUSIONS

Tacrolimus pharmacokinetics are altered during pregnancy. Dose adjustment to maintain whole-blood tacrolimus concentration in the usual therapeutic range during pregnancy increases circulating free drug concentrations, which may impact clinical outcomes.

Pharmacologic evidence to support clinical decision making for peripartum methadone treatment

RATIONALE

Limited pharmacological data are available to guide methadone treatment during pregnancy and postpartum.

OBJECTIVES

Study goals were to (1) characterize changes in methadone dose across childbearing, (2) determine enantiomer-specific methadone withdrawal kinetics from steady state during late pregnancy, (3) assess enantiomer-specific changes in methadone level/dose (L/D) ratios across childbearing, and (4) explore relationships between CYP2B6, CYP2C19, and CYP3A4 single-nucleotide polymorphisms and maternal dose, plasma concentration, and L/D.

METHODS

Methadone dose changes and timed plasma samples were obtained for women on methadone (n = 25) followed prospectively from third trimester of pregnancy to 3 months postpartum.

RESULTS

Participants were primarily white, Medicaid insured, and multiparous. All women increased their dose from first to end of second trimester (mean peak increase = 23 mg/day); 71 % of women increased from second trimester to delivery (mean peak increase = 19 mg/day). Half took a higher dose 3 months postpartum than at delivery despite significantly larger clearance during late pregnancy. Third trimester enantiomer-specific methadone half-lives (range R-methadone 14.7-24.9 h; S-methadone, 8.02-18.9 h) were about half of those reported in non-pregnant populations. In three women with weekly 24-h methadone levels after delivery, L/D increased within 1-2 weeks after delivery. Women with the CYP2B6 Q172 variant GT genotype have consistently higher L/D values for S-methadone across both pregnancy and postpartum.

CONCLUSIONS

Most women require increases in methadone dose across pregnancy. Given the shorter half-life and larger clearances during pregnancy, many pregnant women may benefit from split methadone dosing. L/D increases quickly after delivery and doses should be lowered rapidly after delivery.

Clinical therapeutics in pregnancy

Most drugs are not tested for use during pregnancy, consequently, labeling, which may include information about fetal safety, includes nothing about dosing, efficacy, or maternal safety. Yet these are concerns of health care providers considering treatment of disease during pregnancy. Therefore, the practitioner treats the pregnant woman with the same dose recommended for use in adults (typically men) or may decide not to treat the disease at all. However, is the choice of not treating a woman during pregnancy better than dealing with the challenges which accompany treatment? This paper, which summarizes metabolic and physiologic changes induced by pregnancy, illustrates that standard adult dosing is likely to be incorrect during pregnancy.

Therapeutic drug monitoring in highly active antiretroviral therapy

IMPORTANCE OF THE FIELD

Despite the efficacy of combination antiretroviral therapy (ART), a large proportion of patients living with HIV/AIDS on ART does not achieve or maintain adequate virological suppression. Therapeutic drug monitoring (TDM) has been utilised to improve treatment outcomes of ART.

AREAS COVERED IN THE REVIEW

The potential incorporation of TDM into the clinical HIV management is supported by the existing relationship between drug exposure and efficacy/toxicity, the high inter-patient variability pharmacokinetics, and the accurate, specific and rapid method for drug level determination. The current status of TDM in ART is reviewed in this article with discussions on its feasibility, potential use and limitations.

WHAT THE READER WILL GAIN

Mounting evidence from clinical trials has indicated the potential use of TDM in reducing the rates of treatment failure and adverse effect, avoiding the drug interactions, and special populations, such as children, pregnant women and patients with co-infections. TDM may play an important role even in resource-limited settings, to safeguard expanded use of bioequivalent generic antiretroviral drugs and avoid drug interactions with traditional Chinese medicines.

TAKE HOME MESSAGE

TDM is still in the centre of controversy in that several critical issues need to be addressed, such as limited adherence assessment, inappropriate response predictors, insufficient validation of target concentration windows and lack of the quality control of assay. The utility of TDM will remain experimental until more data are obtained from large clinical trials showing the benefit of TDM.

Antiretroviral treatment in pregnancy: a six-year perspective on recent trends in prescription patterns, viral load suppression, and pregnancy outcomes

The aim of the study was to describe the recent trends in antiretroviral treatment in late pregnancy and the sociodemographic changes among pregnant women with HIV over the last 6 years. Data from the National Program on Surveillance on Antiretroviral Treatment in Pregnancy in Italy were grouped per calendar year, and changes in antiretroviral treatment, population characteristics, maternal immunovirologic status and newborn clinical parameters were analyzed. A total of 981 HIV-infected mothers who delivered between 2002 and 2008 were evaluated. The proportion of women receiving at least three antiretroviral drugs at delivery increased significantly from 63.0% in 2002 to 95.5% in 2007-2008, paralleled by a similar upward trend in the proportion of women who achieved complete viral suppression at third trimester (from 37.3 in 2002 to 80.9 in 2007-2008; p < 0.001). The co-formulation of zidovudine plus lamivudine remained the most common nucleoside backbone in pregnancy, even if a significant increase in the use of tenofovir plus emtricitabine was observed in more recent years. Starting from 2003, nevirapine prescription declined, paralleled by a significant rise in the use of protease inhibitors (PI), which were present in more than 60% of regimens administered in 2007-2008. Nelfinavir was progressively replaced by ritonavir-boosted PIs, mainly lopinavir. No significant changes in preterm delivery, Apgar score, birth weight, and birth defects were observed during the study period, and the rate of HIV transmission remained below 2%. These data demonstrate a significant evolution in the treatment of HIV in pregnancy. Constant improvements in the rates of HIV suppression were observed, probably driven by the adoption of stronger and more effective regimens and by the increasing options available for combination treatment.

Antiretroviral treatment during pregnancy

OBJECTIVE

Virologic failure of HIV-positive patients is of special concern during pregnancy. We compared virologic failure and the frequency of treatment changes in pregnant and non-pregnant women of the Swiss HIV Cohort Study.

METHODS

Using data on 372 pregnancies in 324 women we describe antiretroviral therapy during pregnancy. Pregnant women on HAART at conception (n = 131) were matched to 228 non-pregnant women (interindividual comparison) and to a time period of equal length before and after pregnancy (intraindividual comparison). Women starting HAART during pregnancy (n = 145) were compared with 578 non-pregnant women starting HAART.

FINDINGS

The median age at conception was 31 years, 16% (n = 50) were infected through injecting drug use and the median CD4 cell count was 489 cells/microl. In the majority of pregnancies (n = 220, 59%), women had started ART before conception. When ART was started during pregnancy (n = 145, 39%), it was mainly during the second trimester (n = 100, 69%). Two thirds (n = 26) of 35 women starting in the third trimester were diagnosed with HIV during pregnancy. The risk of virologic failure tended to be lower in pregnant than in non-pregnant women [adjusted odds ratio 0.52 (95% confidence interval 0.25-1.09, P = 0.08)], but was similar in the intraindividual comparison (adjusted odds ratio 1.04, 95% confidence interval 0.48-2.28). Women starting HAART during pregnancy changed the treatment less often than non-pregnant women.

CONCLUSION

Despite the physiological changes occurring during pregnancy, HIV infected pregnant women are not at higher risk of virologic failure.

Pharmacokinetics of new 625 mg nelfinavir formulation during pregnancy and postpartum

OBJECTIVES

Our objective was to evaluate the pharmacokinetics of nelfinavir (NFV) (625 mg tablets) 1250 mg twice daily during pregnancy and postpartum.

METHODS

The participants were HIV-1-infected pregnant women enrolled in P1026s and receiving NFV (625 mg tablets) 1250 mg twice daily as part of routine clinical care. Intensive steady-state 12-h NFV pharmacokinetic profiles were performed during pregnancy and postpartum. The target NFV area under the plasma concentration-time curve (AUC(0-12)) was >or=10th percentile NFV AUC(0-12) in non-pregnant historical controls (18.5 microg h/mL).

RESULTS

Of 27 patients receiving NFV, pharmacokinetic data were available for four (second trimester), 27 (third trimester) and 22 (postpartum) patients. The NFV maximum concentration (C(max)), 12-h post-dose concentration (C(12)) and AUC(0-12) were significantly lower during the third trimester compared to postpartum (P<or=0.03). The metabolite hydroxyl-tert-butylamide (M8) AUC(0-12) and the M8/NFV AUC ratio were lower during the third trimester compared to postpartum (P<0.01). The NFV AUC(0-12) exceeded the AUC(0-12) target for 15/27 (56%) and 21/22 (95%) of third trimester and postpartum patients, respectively. The minimum concentration (C(min)) was above the suggested minimum trough concentration (0.8 mug/mL) in 15% (third trimester) and 18% (postpartum). The plasma viral load was <400 HIV-1 RNA copies/mL in 81% of patients at delivery.

CONCLUSIONS

These results suggest that higher doses of NFV should be considered during pregnancy.

Pharmacokinetics and therapeutic drug monitoring of antiretrovirals in pregnant women

Highly active antiretroviral therapy is recommended for HIV-infected pregnant women to prevent mother-to-child transmission. The specific physiological background induced by pregnancy leads to significant changes in maternal pharmacokinetics, suggesting potential variability in plasma concentrations of antiretrovirals during gestation. Therapeutic drug monitoring (TDM) of protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) is recommended in certain situations, including pregnancy, but its systematic use in HIV-infected pregnant women remains controversial. This review provides an update of the pharmacokinetic data available for PIs and NNRTIs in pregnant women and highlights the clinical interest of systematic TDM of certain antiretroviral drugs during pregnancy, including nevirapine, nelfinavir, saquinavir, indinavir and lopinavir.

Effects of pregnancy on CYP3A and P-glycoprotein activities as measured by disposition of midazolam and digoxin: a University of Washington specialized center of research study

The objectives of the study were to evaluate the effects of pregnancy on CYP3A and P-glycoprotein (P-gp) activities, as measured by disposition of midazolam and digoxin, respectively. Thirteen women received digoxin (0.25 mg p.o.) and midazolam (2 mg p.o.) in random order, separated by 1-2 weeks at 28-32 weeks gestation, and the same order was repeated at 6-10 weeks postpartum. Plasma and urine concentrations were determined by liquid chromatography-mass spectrometry and analyzed by noncompartmental methods. Midazolam CL/F(unbound) (593 +/- 237 l/min vs. 345 +/- 103 l/min; P = 0.007), digoxin CL(Renal, unbound) (272 +/- 45 ml/min vs. 183 +/- 37 ml/min; P < 0.002) and digoxin CL(secretion,) (unbound) (109 +/- 34 ml/min vs. 58 +/- 22 ml/min; P < 0.002) were higher during pregnancy than postpartum. These data are consistent with increased hepatic and/or intestinal CYP3A and renal P-gp activities during pregnancy.

Effect of CYP2C19 polymorphism on nelfinavir to M8 biotransformation in HIV patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Nelfinavir is an HIV protease inhibitor, substrate of the transporter P-glycoprotein and metabolized via CYP2C19, CYP3A4 and CYP3A5 enzymes. * Pharmacokinetic studies have shown wide interindividual variability of nelfinavir concentrations, some of this variability perhaps caused by variant drug metabolism or transporter genes. * For CYP3A4*1B and CYP3A5*3 polymorphism, results from three studies are in agreement, showing no difference in nelfinavir concentrations between patients with these different genotypes. * However, for MDR1 and CYP2C19 polymorphism, there have been contradictory studies, showing either no impact on nelfinavir concentration or modified concentrations which could influence virological response.

WHAT THIS STUDY ADDS

* Patients with an *1/*2 or *2/*2 genotype for CYP2C19 had a nelfinavir to M8 biotransformation divided by 2 compared with *1/*1 patients. * No evidence of any influence of MDR1 polymorphism on nelfinavir absorption could be detected.

AIMS

To evaluate the effect of CYP2C19 polymorphism on nelfinavir and M8 pharmacokinetic variability in human immunodeficiency virus-infected patients and to study the link between pharmacokinetic exposure and short-term efficacy and toxicity.

METHODS

Nelfinavir (n = 120) and M8 (n = 119) concentrations were measured in 34 protease inhibitor-naive patients. Two weeks after initiating the treatment, blood samples were taken before, 1, 3 and 6 h after drug administration. Genotyping for CYP3A4, 3A5, 2C19 and MDR1 was performed. A population pharmacokinetic model was developed to describe nelfinavir-M8 concentration time-courses and to estimate interpatient variability. The influence of individual characteristics and genotypes were tested using a likelihood ratio test. Estimated mean (C(mean)), maximal (C(max)) and trough (C(trough)) nelfinavir and M8 concentrations were correlated to short-term virological efficacy and tolerance using Spearman nonparametric correlation tests.

RESULTS

A one-compartment model with first-order absorption, elimination and metabolism to M8 best described nelfinavir data. M8 was modelled by an additional compartment. Mean pharmacokinetic estimates and the corresponding intersubject variabilities were: absorption rate 0.17 h(-1) (99%), absorption lag time 0.82 h, apparent nelfinavir total clearance 52 l h(-1) (49%), apparent nelfinavir volume of distribution 191 l, M8 elimination rate constant 1.76 h(-1) and nelfinavir to M8 0.39 h(-1) (59%) in *1/*1 patients and 0.20 h(-1) in *1/*2 or *2/*2 patients for CYP2C19*2. Nelfinavir C(mean) was positively correlated to glycaemia and triglyceride increases (P = 0.02 and P = 0.04, respectively).

CONCLUSIONS

The rate of metabolism of nelfinavir to M8 was reduced by 50% in patients with *1/*2 or *2/*2 genotype for CYP2C19 compared with those with *1/*1 genotype.

Pharmacokinetic modelling of the placental transfer of nelfinavir and its M8 metabolite: a population study using 75 maternal-cord plasma samples

AIMS

A population pharmacokinetic model was developed to characterize the transfer of nelfinavir and its active metabolite M8 from maternal to cord plasma and amniotic fluid.

METHODS

Concentration data were obtained from 75 women on the day of delivery and for whom maternal, umbilical plasma and amniotic fluid samples were collected. Data from 53 pregnant, 61 nonpregnant and seven consecutively pregnant and non pregnant women were then added to the database, the contents of which were analyzed using NONMEM.

RESULTS

Nelfinavir and M8 concentrations in maternal plasma, umbilical plasma and amniotic fluid were described by six connected compartments. Mean (% intersubject variability) population estimates were: absorption rate 00.67 h(-1), lag time 00.87 h, oral clearance and volume of distribution: 39.5 l h(-1) (53%), and 557 l for non pregnant and pregnant women, respectively, and 115 l h(-1) (132%) and 1626 l, respectively, on the day of delivery, M8 formation clearance 0.77 l h(-1) and M8 elimination rate constant 03.41 h(-1) (74%). For nelfinavir and M8, respectively, the mother-to-cord parameters were 0.058 l h(-1) (34%), and 00.35 h(-1) (76%), the cord-to-amniotic fluid rate constants were 0.23 and 00.59 h(-1), and the elimination rate constants from amniotic fluid were 0.36 and 00.49 h(-1). The nelfinavir fetus : maternal concentration ratio was 25% for maternal concentrations between 0.1 and 2.5 mg l(-1), between the 31 and 41st week of gestation.

CONCLUSIONS

The low transfer of nelfinavir from the placenta is unlikely to protect the fetus from vertical HIV-1 transmission.

Artemether/lumefantrine in the treatment of uncomplicated falciparum malaria

At present, artemether/lumefantrine (AL) is the only fixed-dose artemisinin-based combination therapy recommended and pre-qualified by WHO for the treatment of uncomplicated malaria caused by Plasmodium falciparum. It has been shown to be effective both in sub-Saharan Africa and in areas with multi-drug resistant P. falciparum in southeast Asia. It is currently recommended as first-line treatment for uncomplicated malaria in several countries. However, AL has a complex treatment regimen and the issues of adherence to treatment with AL by adult patients and real-life effectiveness in resource-poor settings will be critical in determining its useful therapeutic life, especially in Africa, where the major burden of malaria is felt. There are also issues of safety of the artemisinin derivatives, including AL, which will need to be monitored as their use in resource-poor settings becomes more widespread. There are limited pharmacokinetic studies of AL in African patients, and the relationship between plasma drug concentration and efficacy in these patients is unknown. Moreover, the effects of factors such as concurrently administered drugs, malnutrition and co-infections with HIV and helminths in malaria patients are not well understood. These will need to be addressed, although a few studies on possible drug-drug interactions with commonly used drugs, such as quinine, mefloquine and ketoconazole, have been reported. This review focuses on the status of clinical pharmacology, efficacy and real-life effectiveness of AL under a variety of settings, and highlights some of the challenges that face policy makers during the deployment of AL, especially in Africa, with regards to ensuring that those who most need this therapy will not be denied access due to official inefficiency in procurement and distribution processes.