Pharmacogenetics of nevirapine excretion into breast milk and infants' exposure through breast milk versus postexposure prophylaxis

Generic Workflow to Predict Medicine Concentrations in Human Milk Using Physiologically-Based Pharmacokinetic (PBPK) Modelling-A Contribution from the ConcePTION Project

Women commonly take medication during lactation. Currently, there is little information about the exposure-related safety of maternal medicines for breastfed infants. The aim was to explore the performance of a generic physiologically-based pharmacokinetic (PBPK) model to predict concentrations in human milk for ten physiochemically diverse medicines. First, PBPK models were developed for "non-lactating" adult individuals in PK-Sim/MoBi v9.1 (Open Systems Pharmacology). The PBPK models predicted the area-under-the-curve (AUC) and maximum concentrations (C_max) in plasma within a two-fold error. Next, the PBPK models were extended to include lactation physiology. Plasma and human milk concentrations were simulated for a three-months postpartum population, and the corresponding AUC-based milk-to-plasma (M/P) ratios and relative infant doses were calculated. The lactation PBPK models resulted in reasonable predictions for eight medicines, while an overprediction of human milk concentrations and M/P ratios (>2-fold) was observed for two medicines. From a safety perspective, none of the models resulted in underpredictions of observed human milk concentrations. The present effort resulted in a generic workflow to predict medicine concentrations in human milk. This generic PBPK model represents an important step towards an evidence-based safety assessment of maternal medication during lactation, applicable in an early drug development stage.

Viral and antiretroviral dynamics in HIV mother-to-child transmission fluids (VADICT) – Protocol and data analysis plan for a cohort study

Background: Pregnancy and polymorphisms in drug disposition genes alter the clearance of key antiretrovirals used as part of regimens for prevention of mother-to-child transmission of HIV (PMTCT). The clinical significance of these in women initiating therapy late in pregnancy has not been investigated. The primary objective of the Viral and Antiretroviral Dynamics in HIV Mother-To-Child Transmission Fluids (VADICT) study is to investigate viral and antiretroviral dynamics in matrices associated with mother-to-child transmission (MTCT) (plasma, genital fluid and breastmilk) in women (stratified by CYP2B6 genotypes) who initiate antiretroviral therapy (ART) before or early in pregnancy versus late in pregnancy or early postpartum. Methods: A cohort of HIV-1 infected women who initiated ART containing 600 mg efavirenz before or early in pregnancy (n = 120), during the third trimester (n = 60), or early postpartum (n = 60) will be studied.  Eligible patients will be recruited from four hospitals in Benue State, North Central Nigeria and followed until the end of breastfeeding. Procedures at follow up visits will include sample collection for drug quantification and HIV-1 RNA and DNA in plasma, genital fluid and breastmilk; adherence monitoring; and newborn and infant assessment. Using newborn exposure to maternal efavirenz at birth for validation, prenatal pharmacogenetics of efavirenz will be explored using physiologically-based pharmacokinetic modelling. Three integrated methods will be used to monitor patterns and correlates of adherence across pregnancy and the breastfeeding period. A population pharmacokinetic-pharmacodynamic model will be developed to describe the observed data and simulate what to expect in women initiating ART containing 400 mg efavirenz (recently approved for non-pregnant adults) late in pregnancy or early postpartum. Discussion: This study will help in understanding residual MTCT in women receiving ART and reasons for the rise in MTCT risk during the breastfeeding period. Trial registration: ClinicalTrials.gov: NCT03284645 (15/09/2017)

Pharmacogenetics of artemether-lumefantrine influence on nevirapine disposition: Clinically significant drug-drug interaction?

AIMS

In this study the influence of first-line antimalarial drug artemether-lumefantrine on the pharmacokinetics of the antiretroviral drug nevirapine was investigated in the context of selected single nucleotide polymorphisms (SNPs) in a cohort of adult HIV-infected Nigerian patients.

METHODS

This was a two-period, single sequence crossover study. In stage 1, 150 HIV-infected patients receiving nevirapine-based antiretroviral regimens were enrolled and genotyped for seven SNPs. Sparse pharmacokinetic sampling was conducted to identify SNPs independently associated with nevirapine plasma concentration. Patients were categorized as poor, intermediate and extensive metabolizers based on the numbers of alleles of significantly associated SNPs. Intensive sampling was conducted in selected patients from each group. In stage 2, patients received standard artemether-lumefantrine treatment with nevirapine, and intensive pharmacokinetic sampling was conducted on day 3.

RESULTS

No clinically significant changes were observed in key nevirapine pharmacokinetic parameters, the 90% confidence interval for the measured changes falling completely within the 0.80-1.25 no-effect boundaries. However, the number of patients with trough plasma nevirapine concentration below the 3400 ng ml^-1 minimum effective concentration increased from 10% without artemether-lumefantrine (all extensive metabolizers) to 21% with artemether-lumefantrine (14% extensive, 4% intermediate, and 3% poor metabolizers).

CONCLUSIONS

This approach highlights additional increase in the already existing risk of suboptimal trough plasma concentration, especially in extensive metabolizers when nevirapine is co-administered with artemether-lumefantrine.

Prevention of TB using rifampicin plus isoniazid reduces nevirapine concentrations in HIV-exposed infants

Background

Newborns of HIV-infected mothers are given daily doses of nevirapine to prevent HIV-1 acquisition. Infants born to mothers with TB should also receive TB preventive therapy. TB preventive regimens include isoniazid for 6 months or rifampicin plus isoniazid for 3 months (RH preventive therapy). The effect of concomitant RH preventive therapy on nevirapine concentrations in infants is unknown.

Patients and methods

Tshepiso was a prospective case-control cohort study of pregnant HIV-infected women with and without TB whose newborn infants received standard doses of nevirapine for HIV prophylaxis. Infants born to mothers with TB also received RH preventive therapy. Infant plasma nevirapine concentrations were measured at 1 and 6 weeks. The effects of RH preventive therapy on nevirapine disposition were investigated in a population pharmacokinetic model.

Results

Of 164 infants undergoing pharmacokinetic sampling, 46 received RH preventive therapy. After adjusting for weight using allometric scaling, the model estimated a 33% reduction in nevirapine trough concentrations with RH preventive therapy compared with TB-unexposed infants not receiving concomitant rifampicin and a 30% decline in trough concentrations in a typical infant between day 7 and 35 post-partum.

Conclusions

Rifampicin-based TB preventative treatment reduces nevirapine concentrations significantly in HIV-exposed infants. Although the nevirapine exposures required to prevent HIV acquisition in breastfeeding infants are undefined, given the potential risks associated with underdosing nevirapine in this setting, it is prudent to avoid rifampicin-based preventive therapy in HIV-exposed children receiving prophylactic nevirapine.

Plasma and breast milk pharmacokinetics of emtricitabine, tenofovir and lamivudine using dried blood and breast milk spots in nursing African mother-infant pairs

Background

Breast milk transfer of first-line ART from mother to infant is not fully understood.

Objectives

To determine the concentrations of lamivudine, emtricitabine and tenofovir in maternal blood, breast milk and infant blood from breastfeeding mother-infant pairs.

Methods

Intensive pharmacokinetic sampling of maternal dried blood spots (DBS), dried breast milk spots (DBMS) and infant DBS from 30 Ugandan and 29 Nigerian mothers receiving first-line ART and their infants was conducted. DBS and DBMS were collected pre-dose and at 5-6 timepoints up to 12 h following observed dosing. Infant DBS were sampled twice during this period. Lamivudine, emtricitabine and tenofovir were quantified using LC-MS/MS, with non-compartmental analysis to calculate key pharmacokinetic parameters.

Results

Peak concentrations in breast milk from women taking lamivudine and emtricitabine occurred later than in plasma (4-8 h compared with 2 h for lamivudine and 2-4 h for emtricitabine). Consequently, the milk-to-plasma (M:P) ratio of lamivudine taken once daily was 0.95 (0.82-1.15) for AUC0-12, whereas for AUC12-20 this was 3.04 (2.87-4.16). Lamivudine was detectable in 36% (14/39) of infants [median 17.7 (16.3-22.7) ng/mL]. For 200 mg of emtricitabine once daily, the median M:P ratio was 3.01 (2.06-3.38). Three infants (19%) had measurable emtricitabine [median 18.5 (17.6-20.8) ng/mL]. For 300 mg of tenofovir once daily, the median M:P ratio was 0.015 (0-0.03) and no infant had measurable tenofovir concentrations.

Conclusions

Emtricitabine and lamivudine accumulate in breast milk and were detected in breastfeeding infants. In contrast, tenofovir penetrates the breast milk to a small degree, but is undetectable in breastfeeding infants.