Potential effect of pharmacogenetics on maternal, fetal and infant antiretroviral drug exposure during pregnancy and breastfeeding

Non-Nutritive Sweeteners Acesulfame Potassium and Sucralose Are Competitive Inhibitors of the Human P-glycoprotein/Multidrug Resistance Protein 1 (PGP/MDR1)

Non-nutritive sweeteners (NNS) are popular sugar replacements used in foods, beverages, and medications. Although NNS are considered safe by regulatory organizations, their effects on physiological processes such as detoxification are incompletely understood. Previous studies revealed that the NNS sucralose (Sucr) altered P-glycoprotein (PGP) expression in rat colon. We also demonstrated that early-life exposure to NNS Sucr and acesulfame potassium (AceK) compromises mouse liver detoxification. Building upon these initial discoveries, we investigated the impact of AceK and Sucr on the PGP transporter in human cells to assess whether NNS influence its key role in cellular detoxification and drug metabolism. We showed that AceK and Sucr acted as PGP inhibitors, competing for the natural substrate-binding pocket of PGP. Most importantly, this was observed after exposure to concentrations of NNS within expected levels from common foods and beverage consumption. This may suggest risks for NNS consumers, either when taking medications that require PGP as the primary detoxification transporter or during exposure to toxic compounds.

Differential effects of antiretroviral drug toxicity in male versus female children who are HIV-exposed but uninfected

: In recent years, widespread use of antiretroviral therapy (ART) during pregnancy has been increasingly effective in reducing risk of vertical transmission of HIV, with over 80% of pregnant women living with HIV now accessing ART, and a 41% reduction in new infections in children between 2010 and 2018. Despite these strides, the developmental toxicity of widely administered antiretroviral drugs (ARVs) remains poorly described and existing literature often fails to account for fetal and infant sex as a variable. Recent reports have identified associations between in-utero exposure to commonly used antiretroviral regimens and alteration in neurodevelopment, growth, and metabolism amongst children who are HIV-exposed but uninfected, with findings of sex differences in the prevalence and severity of ARV toxicity. These differences are potentially explained by variable exposure to ARV drugs in utero or exacerbation of existing sex-linked risk factors. Fetal ARV exposure is mediated by placental and fetal drug transporters and metabolic enzymes, which may contribute to the manifestation of sex differences. Existing evidence of sex differences in ARV toxicity in fetal development is concerning, and demands further research to guide optimal treatment options for maternal health and prevention of vertical HIV transmission.

Frequency of differential placental transfer to twins of maternal antiretroviral medications

BACKGROUND

Placental passage of drugs in twins is poorly understood, and is unknown regarding antiretrovirals (ARVs). In the event of large differences in the exposure of 2 twins to the same maternal therapy, this could have a clinical impact in terms of prevention of perinatal HIV transmission or adverse effects.

OBJECTIVE

To describe the frequency of differential transplacental passage of antiretrovirals between twins.

STUDY DESIGN

The study was performed retrospectively, on data from women included in a multicenter perinatal HIV cohort study. All twin pairs for which the mother received antiretroviral therapy and for which drug concentrations in both of the umbilical cords after cord clamping at delivery were studied. We considered that a difference in concentrations of more than 50 % between twins was a substantial difference (ratios below 0.67 or above 1.50).

RESULTS

We analyzed 29 twin pairs, 27 dichorionic and 2 monochorionic diamniotic. Cord blood concentrations differed between the 2 twins by more than 50 % for at least one ARV in 9 twin pairs, 8 dichorionic and 1 monochorionic. Discordant concentrations were observed in one or more cases for several nucleoside reverse transcriptase inhibitors (tenofovir, emtricitabine, lamivudine, zidovudine) and protease inhibitors (atazanavir, lopinavir, saquinavir et ritonavir); within individual twin pairs placental transfer was discordant for one or more ARVs, but identical for others.

CONCLUSION

Concentrations differed in nearly one third of twin pairs. This may be due to interindividual genetic variability of placental transporters between dizygotic twins as well as physiological differences between twins.

Pharmacokinetics of HIV therapies in pregnant patients: an update

INTRODUCTION

Mother-to-child transmission (MTCT) of HIV is thought to account for over 90% of new pediatric infections, and is associated with poor maternal and fetal outcomes. As such ensuring further reduction in MTCT is a priority in HIV treatment and prevention programs.

AREAS COVERED

This review aims to provide a comprehensive update on the pharmacokinetics of recently approved antiretroviral drugs and novel drug formulations and delivery systems. Alongside recent recommendations for dose adjustments, and an overview of the implications of co-infections on the pharmacokinetics of antiretrovirals relevant to pregnant HIV positive patients. Additionally, potential opportunities to progress pharmacokinetic research of new treatments in this population are highlighted.

EXPERT OPINION

In order to improve our understanding of how to provide safe and effective treatment to HIV positive pregnant women, further work is required to enable their inclusion in early stages of clinical trials. Incentives must be created for this research, in the form of additional investment by key stakeholders and regulatory agencies. Furthermore, as the incidence of MTCT is reduced globally there is a need to conduct long-term pharmacovigilance studies in uninfected children exposed to HIV and antiretrovirals in utero, in order to determine the safest and most effective antiretroviral therapies.

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)

Efavirenz and Lopinavir Levels in HIV-Infected Women and Their Nursing Infants, in Mali

Limited data are currently available on antiretroviral pharmacokinetics in breast milk (BM) and in breastfed infants' blood. To explore these parameters in patients in Mali, we measured plasma antiretroviral levels in human immunodeficiency virus (HIV)-infected mothers and their breastfed infants over 6 months. We specifically analyzed the concentrations of efavirenz (EFV) and lopinavir (LPV) in the plasma of mothers living with HIV and their breastfed infants. Blood samples were collected at delivery and at month 1, 3, and 6 postpartum. EFV and LPV concentrations were measured by liquid chromatography-tandem mass spectrometry. HIV-1 RNA load was measured by Abbott M2000RT RealTime System at delivery and 6 months postpartum for mothers, and at 3 and 6 months postbirth for infants. The median duration of antiretroviral therapy at study inclusion was 57 months [interquartile range (IQR), 0-168 months]. The median EFV ratios of infant plasma/maternal plasma (MP) were 0.057 at month 1, 0.072 at month 3, and 0.048 at month 6. During the study period, the median BM/MP ratio of EFV was 1.16 (IQR, 0.96-20.62), which corresponds to a relative infant dose of 2.46% of the recommended weight-adjusted pediatric EFV dose at month 6. The apparent infant clearance of EFV was 0.146 l/h per kilogram at month 6. The LPV concentrations in the plasma of all infants were undetectable. No drug-related adverse reaction or toxicity was observed in any of the infants. The two women who presented a viral load of >50 copies/ml at month 6 had undetectable plasma drug concentrations at the same period. This study showed that breastfed infants received a low level of EFV but not LPV from their treated mothers.

Drugs in Lactation

One impediment to breastfeeding is the lack of information on the use of many drugs during lactation, especially newer ones. The principles of drug passage into breastmilk are well established, but have often not been optimally applied prospectively. Commonly used preclinical rodent models for determining drug excretion into milk are very unreliable because of marked differences in milk composition and transporters compared to those of humans. Measurement of drug concentrations in humans remains the gold standard, but computer modeling is promising. New FDA labeling requirements present an opportunity to apply modeling to preclinical drug development in place of conventional animal testing for drug excretion into breastmilk, which should improve the use of medications in nursing mothers.

Pharmacogenetic Analysis of the Model-Based Pharmacokinetics of Five Anti-HIV Drugs: How Does This Influence the Effect of Aging?

Analysis of aging and pharmacogenetics (PGx) on antiretroviral pharmacokinetics (PKs) could inform precision dosing for older human HIV‐infected patients. Seventy‐four participants receiving either atazanavir/ritonavir (ATV/RTV) or efavirenz (EFV) with tenofovir/emtricitabine (TFV/FTC) provided PK and PGx information. Aging‐PGx‐PK association and interaction analyses were conducted using one‐way analysis of variance (ANOVA), multiple linear regression, and Random Forest ensemble methods. Our analyses associated unbound ATV disposition with multidrug resistance protein (MRP)4, RTV with P‐glycoprotein (P‐gp), and EFV with cytochrome P450 (CYP)2B6 and MRP4 genetic variants. The clearance and cellular distribution of TFV were associated with P‐gp, MRP2, and concentrative nucleoside transporters (CNTs), and FTC parameters were associated with organic cation transporters (OCTs) and MRP2 genetic variants. Notably, p16^INK4a expression, a cellular aging marker, predicted EFV and FTC PK when genetic factors were adjusted. Both age and p16^INK4a expression interacted with PGx on ATV and TFV disposition, implying potential dose adjustment based on aging may depend on genetic background.

Pharmacokinetics of Bupropion and Its Pharmacologically Active Metabolites in Pregnancy

Bupropion sustained release is used to promote smoking cessation in males and nonpregnant females. However, its efficacy as a smoking cessation aid during pregnancy is not reported. The pregnancy-associated changes in maternal physiology may alter the pharmacokinetics and pharmacodynamics of bupropion and consequently its efficacy in pregnant smokers. Therefore, the aims of this study were to determine the steady-state pharmacokinetics of bupropion during pregnancy and the effect of functional genetic variants of CYP2B6 and CYP2C19 on bupropion pharmacokinetics in pregnant women. Plasma and urine concentrations of bupropion and its metabolites hydroxybupropion (OHBUP), threohydrobupropion, and erythrohydrobupropion were determined by liquid chromatography-mass spectrometry. Subjects were genotyped for five nonsynonymous single-nucleotide polymorphisms that result in seven CYP2B6 alleles, namely *2, *3, *4, *5, *6, *7, and *9, and for CYP2C19 variants *2, *3, and *17 The present study reports that the isoform-specific effect of pregnancy on bupropion-metabolizing enzymes along with the increase of renal elimination of the drug could collectively result in a slight decrease in exposure to bupropion in pregnancy. In contrast, pregnancy-induced increase in CYP2B6-catalyzed bupropion hydroxylation did not impact the plasma levels of OHBUP, probably due to a higher rate of OHBUP glucuronidation, and renal elimination associated with pregnancy. Therefore, exposure to OHBUP, a pharmacologically active metabolite of the bupropion, appears to be similar to that of the nonpregnant state. The predicted metabolic phenotypes of CYP2B6*6 and variant alleles of CYP2C19 in pregnancy are similar to those in the nonpregnant state.

Accelerated oral nanomedicine discovery from miniaturized screening to clinical production exemplified by paediatric HIV nanotherapies

Considerable scope exists to vary the physical and chemical properties of nanoparticles, with subsequent impact on biological interactions; however, no accelerated process to access large nanoparticle material space is currently available, hampering the development of new nanomedicines. In particular, no clinically available nanotherapies exist for HIV populations and conventional paediatric HIV medicines are poorly available; one current paediatric formulation utilizes high ethanol concentrations to solubilize lopinavir, a poorly soluble antiretroviral. Here we apply accelerated nanomedicine discovery to generate a potential aqueous paediatric HIV nanotherapy, with clinical translation and regulatory approval for human evaluation. Our rapid small-scale screening approach yields large libraries of solid drug nanoparticles (160 individual components) targeting oral dose. Screening uses 1 mg of drug compound per library member and iterative pharmacological and chemical evaluation establishes potential candidates for progression through to clinical manufacture. The wide applicability of our strategy has implications for multiple therapy development programmes.

Pharmacokinetics of Rilpivirine in HIV-Infected Pregnant Women

BACKGROUND

Rilpivirine pharmacokinetics is defined by its absorption, distribution, metabolism, and excretion. Pregnancy can affect these factors by changes in cardiac output, protein binding, volume of distribution, and cytochrome P450 (CYP) 3A4 activity. Rilpivirine is metabolized by CYP3A4. The impact of pregnancy on rilpivirine pharmacokinetics is largely unknown.

METHODS

International Maternal Pediatric Adolescent AIDS Clinical Trials P1026s is a multicenter, nonblinded, prospective study evaluating antiretroviral pharmacokinetics in HIV-infected pregnant women that included a cohort receiving rilpivirine 25 mg once daily as part of their combination antiretrovirals for clinical care. Thirty-two women were enrolled in this study. Intensive pharmacokinetic sampling was performed at steady state during the second trimester, the third trimester, and postpartum. Maternal and umbilical cord blood samples were obtained at delivery. Plasma rilpivirine concentration was measured using liquid chromatography-mass spectrometry; lower limit of quantitation was 10 ng/mL.

RESULTS

Median (range) AUC0-24 were 1969 (867-4987, n = 15), 1669 (556-4312, n = 28), and 2387 (188-6736, n = 28) ng·h/mL in the second trimester, the third trimester, and postpartum, respectively (P < 0.05 for either trimester vs postpartum). Median (range) C24 were 63 (37-225, n = 17), 56 (<10-181, n = 30), and 81 (<10-299, n = 28) ng/mL (P < 0.05 for either trimester vs postpartum). High variability in pharmacokinetic parameters was observed between subjects. Median (range) cord blood/maternal concentration ratio was 0.55 (0.3-0.8, n = 21). Delivery HIV-1 RNA was ≤50 copies per milliliter in 70% and ≤400 copies per milliliter in 90% of women. Cmin were significantly lower at 15 visits with detectable HIV-1 RNA compared with 61 visits with undetectable HIV-1 RNA, 29 (<10-93) vs 63 (15-200) ng/mL (P = 0.0001). Cmin was below the protein binding-adjusted EC90 concentration (12.2 ng/mL) at 4 visits in 3 of 31 women (10%).

CONCLUSIONS

Rilpivirine exposure is lower during pregnancy compared with postpartum and highly variable. Ninety percent of women had minimum concentrations above the protein binding-adjusted EC90 for rilpivirine.

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

AIM

The influence of genetic factors on nevirapine (NVP) breast milk pharmacokinetics and breastfed infants' exposure were investigated.

PATIENTS & METHODS

Associations between nine SNPs in NVP disposition genes in mothers and its plasma and breast milk concentrations were explored in nursing mother-infant pairs.

RESULTS

NVP pharmacokinetics in maternal plasma, breast milk and infant exposure indices were influenced by CYP2B6 516G>T and 983T>C. The median (range) milk-to-plasma area under the curve (AUC0-12) ratio was 0.95 (0.56-1.5). Calculated as percentages of pediatric treatment, infant postexposure prophylaxis and maternal weight-adjusted doses, the maximum exposure indices were 3.64% (1.99-9.88), 26.0% (9.93-79.1) and 13.8% (5.77-27.7), respectively. Infant plasma concentration as a result of exposure through breast milk (n = 93), pre-exposure prophylaxis (n = 10) and both (n = 27) were 660 (104-3090), 1020 (401-3325) and 2720 ng/ml (1360-7290), respectively.

CONCLUSION

The clinical significance of the observed differences between routes of infants' exposure warrants further investigation.

Prenatal pharmacogenomics: a promising area for research

Clinical applications of prenatal genetic screening currently focus on detection of aneuploidy and other genetic diseases in the developing fetus. Growing evidence suggests that the fetal genome may also be informative about fetal exposures, through contributions to placental transport as well as placental and fetal metabolism. Possible clinical applications of prenatal pharmacogenomic screening include prospective optimization of medication selection and dosage, as well as retrospective assessment of whether a fetus was previously exposed to significant risk. Newly available non-invasive methods of prenatal genetic screening mean that relevant fetal genotypes could be made available to obstetricians for use in management of a current pregnancy. This promising area for research merits more attention than it has thus far received.

Genomewide association study of tenofovir pharmacokinetics and creatinine clearance in AIDS Clinical Trials Group protocol A5202

BACKGROUND

Tenofovir disoproxil fumarate (TDF) causes kidney toxicity in some patients. We carried out genomewide analyses to identify associations with plasma tenofovir clearance and change in creatinine clearance (CrCl) during the first 6 months after initiating therapy among patients randomized to TDF/emtricitabine-containing regimens in AIDS Clinical Trials Group protocol A5202.

METHODS

Pharmacokinetic analyses involved 501 patients randomized to the tenofovir arm. CrCl analyses involved 1096 patients, including 548 controls randomized to abacavir-containing regimens. All had been randomized to also receive atazanavir/ritonavir or efavirenz. Multivariable linear regression and generalized least squares models were used to test for associations between polymorphisms and tenofovir clearance and CrCl change, with Bonferroni correction. Planned subanalyses considered candidate genes and polymorphisms.

RESULTS

Median CrCl at baseline was 116 ml/min (interquartile range 99.8-135.5). The median change in CrCl after 6 months was -0.5 ml/min (-10.7 to +10.8) and 2.2 (interquartile range -9.9 to +13.2) in tenofovir and abacavir arms, respectively. In genomewide analyses SLC17A1 rs12662869 was found to be associated with an increase in tenofovir clearance (P=7.1×10). In candidate gene analysis for tenofovir clearance, most polymorphisms evaluated were in ABCC4. In the ABCC4 region, the lowest P-value was for CLDN10 rs12866697 (P=1.4×10). Among African Americans, SLC22A2 rs3127573 was associated with a greater 6-month CrCl increase in the tenofovir arm after correcting for multiple comparisons (P=3.3×10).

CONCLUSION

Among patients randomized to receive TDF/emtricitabine in A5202, there were no significant genomewide associations with change in CrCl. This study did not replicate polymorphisms previously implicated in tenofovir-associated renal injury.

Breast milk pharmacokinetics of efavirenz and breastfed infants' exposure in genetically defined subgroups of mother-infant pairs: an observational study

BACKGROUND

The antiretroviral drug efavirenz is widely used during breastfeeding. Evaluating its safety requires an understanding of its breast milk pharmacokinetics, level of breastfed infants' exposure, and potential influence of polymorphisms in drug disposition genes.

METHODS

For this observational study, we investigated plasma and breast milk pharmacokinetics of efavirenz and breastfed infants' exposure in human immunodeficiency virus positive nursing mothers and their breastfed infants. We also evaluated potential variability due to genetic polymorphisms in CYP2B6, NR1I3, CYP2A6, ABCB1, ABCB5, and ABCG2.

RESULTS

CYP2B6 516G>T was independently associated with efavirenz concentrations in maternal plasma, breast milk, and infant plasma (n = 134). When stratified based on CYP2B6 516G>T (n = 29 ; 11 GG, 10 GT and 8 TT), efavirenz pharmacokinetic parameters in plasma and breast milk differed significantly between patient groups. The median time-averaged milk-to-plasma concentration ratio was 1.10 (range: 0.57-1.71). The estimated maximum infant efavirenz dose from breast milk was 809 µg/kg/day (215-2760) and pediatric dose weight-adjusted exposure index was 4.05% (1.08-13.8). Infant plasma concentrations did not change significantly during the dosing interval, 157 ng/mL (28.6-1360) in pooled analysis and 315 ng/mL (108-1360) in CYP2B6 516TT group. Infant plasma concentrations were highest up to 8 days of age at 1590 ng/mL (190-4631) and decreased by about 90% in the age stratum day 9 to 3 months. No efavirenz related toxicity was reported.

CONCLUSIONS

Most breastfed infants are exposed to <10% of the weight-adjusted therapeutic pediatric dose, the safety threshold for exposure to maternal drugs from breast milk.

Pharmacogenetics of pregnancy-induced changes in efavirenz pharmacokinetics

Pregnancy-induced physiological changes alter many drugs' pharmacokinetics. We investigated pregnancy-induced changes in efavirenz pharmacokinetics in 25 pregnant and 19 different postpartum women stratified from 211 HIV-positive women in whom a preliminary pharmacogenetic study had been undertaken. Despite significant changes in CL/F during pregnancy (42.6% increase; P = 0.023), median (range) Cmin was 1,000 ng/mL (429-5,190) with no significant change in Cmax (P = 0.072). However, when stratified for CYP2B6 516G>T (rs3745274) genotype, efavirenz AUC0-24 , Cmax and Cmin were 50.6% (P = 0.0013), 17.2% (P = 0.14), and 61.6% (P = 0.0027) lower during pregnancy (n = 8) compared with postpartum (n = 6) in 516G homozygotes, with values of 25,900 ng.h/mL (21,700-32,600), 2,640 ng/mL (1,260-3,490), and 592 ng/mL (429-917), respectively, and CL/F was 100% higher (P = 0.0013). No changes were apparent in CYP2B6 516 heterozygotes (14 pregnant vs. 7 postpartum). The clinical implications of these findings warrant further investigation.

Development, validation and clinical application of a novel method for the quantification of efavirenz in dried breast milk spots using LC-MS/MS

OBJECTIVES

This manuscript describes the development, validation and clinical application of a novel method for the quantification of the antiretroviral drug efavirenz in dried breast milk spots using LC-MS.

METHODS

Dried breast milk spots were prepared by spotting 30 μL of human breast milk on each circle of Whatman 903 Protein Saver cards. Chromatographic separation was achieved on a reverse-phase C18 column with 1 mM ammonium acetate in water/acetonitrile using a solvent gradient at a flow rate of 400 μL/min and detection was by TSQ Quantum Access triple quadrupole mass spectrometer equipped with a heated electrospray ionization source. The method was applied to characterize the breast milk pharmacokinetic profile of efavirenz in HIV-positive nursing mothers receiving regimens containing 600 mg of efavirenz once daily.

RESULTS

The assay was validated over the concentration range 50-7500 ng/mL. Accuracy ranged between 95.2% and 102.5% and precision ranged between 1.05% and 9.53%. The average recovery of efavirenz from dried breast milk spots was 106.4% and the matrix effect was 8.14%. Stability of efavirenz in dried breast milk spots and processed samples at room temperature, -40°C and -80°C was demonstrated. In the pharmacokinetic study, the mean (SD) AUC0-24, Cmax and Cmin of efavirenz in breast milk were 59,620 ng·h/mL (17,440), 4527 ng/mL (1767) and 1261 ng/mL (755.9), respectively. The mean (range) milk-to-plasma concentration ratio over the dosing interval was 0.78 (0.57-1.26).

CONCLUSIONS

The dried breast milk spot method is simple, robust, accurate and precise, and can be used in settings with limited resources.

Pharmacological considerations on the use of antiretrovirals in pregnancy

PURPOSE OF REVIEW

Treatment with combination antiretroviral therapy during pregnancy reduces the chance of mother to child transmission of HIV. Physiological changes during pregnancy can lead to lower exposure to antiretrovirals, possibly resulting in virological failure. For most antiretrovirals, data on exposure during pregnancy and transplacental passage are limited. This review summarizes the most recent information on pharmacokinetics (including transplacental passage), efficacy, as well as the safety of antiretrovirals during pregnancy.

RECENT FINDINGS

Intensive-sampling pharmacokinetic studies as well as observational studies using sparse sampling were performed to explore the exposure to antiretrovirals during pregnancy. Transplacental passage, efficacy (viral load at delivery and infection status of the newborn) and safety information were evaluated for several antiretrovirals.

SUMMARY

For most nucleoside/nucleotide reverse transcriptase inhibitors and protease inhibitors, recent research shows a decreased exposure during pregnancy. However, the advantage of a general dose increase during pregnancy still remains unclear. For newer compounds and efavirenz, limited or no data on pharmacokinetics during pregnancy or transplacentally are available, while the mechanisms of transplacental passage also remain unknown. For safety reasons, it will be important to monitor pregnancy outcomes in resource-limited settings during the implementation of the WHO guidelines (including the use of efavirenz during pregnancy).

Antiretroviral pharmacokinetics in mothers and breastfeeding infants from 6 to 24 weeks post-partum: results of the BAN Study

BACKGROUND

An intensive, prospective, open-label pharmacokinetic (PK) study in a subset of HIV-infected mothers and their uninfected infants enrolled in the Breastfeeding, Antiretroviral and Nutrition (BAN) Study was performed to describe drug exposure and antiviral response.

METHODS

Women using Combivir(®) (zidovudine [ZDV] + lamivudine [3TC]) +Aluvia(®) (lopinavir/ritonavir [LPV/RTV]) were enrolled. Breast milk (BM), mother plasma (MP) and infant plasma (IP) samples were obtained over 6 h after observed dosing at 6, 12 or 24 weeks post-partum for drug concentrations and HIV RNA.

RESULTS

A total of 30 mother/infant pairs (10 each at 6, 12 and 24 weeks post-partum) were enrolled. Relative to MP, BM concentrations of ZDV and 3TC were 35% and 21% higher, respectively, whereas LPV and RTV were 80% lower. Only 3TC was detected in IP with concentrations 96% and 98% lower than MP and BM, respectively. Concentrations in all matrices were similar at 6-24 weeks. The majority (98.3%) of BM concentrations were >HIV(wt) IC50, with one having detectable virus. There was no association between PK parameters and MP or BM HIV RNA.

CONCLUSIONS

ZDV and 3TC concentrated in BM whereas LPV and RTV did not, possibly due to protein binding and drug transporter affinity. Undetectable to low antiretroviral concentrations in IP suggest prevention of transmission while breastfeeding may be due to antiretroviral effects on systemic or BM HIV RNA in the mother. Low IP 3TC exposure may predispose an infected infant to HIV resistance, necessitating testing and treating infants early.

Physiologically based pharmacokinetic models for the optimization of antiretroviral therapy: recent progress and future perspective

Anti-HIV therapy is characterized by the chronic administration of antiretrovirals (ARVs), and consequently, several problems can arise during the management of HIV-positive patients. ARV disposition can be simulated by combining system data describing a population of patients and in vitro drug data through physiologically based pharmacokinetic (PBPK) models, which mathematically describe absorption, distribution, metabolism and elimination. PBPK modeling can find application in the investigation of clinically relevant scenarios, while providing the opportunity for a better understanding of the mechanisms regulating drug distribution. In this review, we have analyzed the most recent applications of PBPK models for ARVs and highlighted some of the most interesting areas of use, such as drug–drug interaction, pharmacogenetics, factors regulating absorption and tissue penetration, as well as therapy optimization in special populations. The application of the PBPK modeling approach might not be limited to the investigation of hypothetical clinical issues, but could be used to inform future prospective clinical trials.