Functional role of p-glycoprotein and binding protein effect on the placental transfer of lopinavir/ritonavir in the ex vivo human perfusion model

Fetus Exposure to Drugs and Chemicals: A Holistic Overview on the Assessment of Their Transport and Metabolism across the Human Placental Barrier

BACKGROUND

The placenta exerts a crucial role in fetus growth and development during gestation, protecting the fetus from maternal drugs and chemical exposure. However, diverse drugs and chemicals (xenobiotics) can penetrate the maternal placental barrier, leading to deleterious, adverse effects concerning fetus health. Moreover, placental enzymes can metabolize drugs and chemicals into more toxic compounds for the fetus. Thus, evaluating the molecular mechanisms through which drugs and chemicals transfer and undergo metabolism across the placental barrier is of vital importance. In this aspect, this comprehensive literature review aims to provide a holistic approach by critically summarizing and scrutinizing the potential molecular processes and mechanisms governing drugs and chemical transfer and metabolism across the placental barrier, which may lead to fetotoxicity effects, as well as analyzing the currently available experimental methodologies used to assess xenobiotics placental transfer and metabolism.

METHODS

A comprehensive and in-depth literature review was conducted in the most accurate scientific databases such as PubMed, Scopus, and Web of Science by using relevant and effective keywords related to xenobiotic placental transfer and metabolism, retrieving 8830 published articles until 5 February 2024. After applying several strict exclusion and inclusion criteria, a final number of 148 relevant published articles were included.

RESULTS

During pregnancy, several drugs and chemicals can be transferred from the mother to the fetus across the placental barrier by either passive diffusion or through placental transporters, resulting in fetus exposure and potential fetotoxicity effects. Some drugs and chemicals also appear to be metabolized across the placental barrier, leading to more toxic products for both the mother and the fetus. At present, there is increasing research development of diverse experimental methodologies to determine the potential molecular processes and mechanisms of drug and chemical placental transfer and metabolism. All the currently available methodologies have specific strengths and limitations, highlighting the strong demand to utilize an efficient combination of them to obtain reliable evidence concerning drug and chemical transfer and metabolism across the placental barrier. To derive the most consistent and safe evidence, in vitro studies, ex vivo perfusion methods, and in vivo animal and human studies can be applied together with the final aim to minimize potential fetotoxicity effects.

CONCLUSIONS

Research is being increasingly carried out to obtain an accurate and safe evaluation of drug and chemical transport and metabolism across the placental barrier, applying a combination of advanced techniques to avoid potential fetotoxic effects. The improvement of the currently available techniques and the development of novel experimental protocols and methodologies are of major importance to protect both the mother and the fetus from xenobiotic exposure, as well as to minimize potential fetotoxicity effects.

Variability in perfusion conditions and set-up parameters used in ex vivo human placenta models: A literature review

The ex vivo human placenta perfusion model has proven to be clinically relevant to study transfer- and fetal exposure of various drugs. Although the method has existed for a long period, the setup of the perfusion model has not been generalized yet. This review aims to summarize the setups of ex vivo placental perfusion models used to examine drug transfer across the placenta to identify generalized properties and differences across setups. A literature search was carried out in PubMed September 26, 2022. Studies were labeled as relevant when information was reported, between 2000 and 2022, on the setups of ex vivo placental perfusion models used to study drug transfer across the placenta. The placenta perfusion process, and the data extraction, was divided into phases of preparation, control, drug, and experimental reflecting the chronological timeline of the different phases during the entire placental perfusion process. 135 studies describing an ex vivo human placental perfusion experiment were included. Among included studies, the majority (78.5%) analyzed drug perfusion in maternal to fetal direction, 18% evaluated bi-directional drug perfusion, 3% under equilibrium conditions, and one study investigated drug perfusion in fetal to maternal direction. This literature review facilitates the comparison of studies that employ similar placenta perfusion protocols for drug transfer studies and reveals significant disparities in the setup of these ex vivo placental perfusion models. Due to interlaboratory variability, perfusion studies are not readily comparable or interchangeable. Therefore, a stepwise protocol with multiple checkpoints for validating placental perfusion is needed.

Outcomes of Children with Fetal and Lactation Immunosuppression Exposure Born to Female Transplant Recipients

Solid organ transplantation (SOT) is a lifesaving procedure for those with end-stage kidney, liver, heart, lung, and intestinal diseases, including females of childbearing age who wish to proceed with pregnancy following transplantation. While there is clear risk associated with use of mycophenolate during pregnancy, the risks associated with use of other immunosuppressant agents are less well understood, and the timing of use in pregnancy may be pertinent when considering the risk versus benefit for individual patients. In addition to overall fetal outcomes, including gestational age, birth weight, and mortality, this review summarizes published literature on additional complications that have been examined in association with maternal use during pregnancy and postpartum while breastfeeding. Compared with non-transplant pregnancies, pregnancies in transplant recipients are associated with lower birth weight and earlier gestational age. Effects associated with particular immunosuppressant agents in the infant include renal dysfunction from calcineurin inhibitors, myelosuppression from azathioprine, and decreased circulating immune cells with several agents. However, these effects are noted to primarily be transient, though the decrease in immune cells may predispose the infant to increased infectious complications in the first year of life. Utilizing relative infant dose estimations, nearly all commonly utilized immunosuppressants are likely safe during breastfeeding given the limited exposure to the infant.

First evidence that emerging pinnatoxin-G, a contaminant of shellfish, reaches the brain and crosses the placental barrier

Massive proliferation of some toxic marine dinoflagellates is responsible for the occurrence of harmful algal blooms and the contamination of fish and shellfish worldwide. Pinnatoxins (PnTx) (A-H) comprise an emerging phycotoxin family belonging to the cyclic imine toxin group. Interest has been focused on these lipophilic, fast-acting and highly potent toxins because they are widely found in contaminated shellfish, and can represent a risk for seafood consumers. PnTx display a potent antagonist effect on nicotinic acetylcholine receptors (nAChR), and in this study we assessed in vivo the ability of PnTx-G to cross physiological barriers to reach its molecular target. Radiolabeled [³H]-PnTx-G synthesized with good radiochemical purity and yield retained the high affinity of the natural toxin. Oral gavage or intravenous administration to adult rats and digital autoradiographic analyses revealed the biodistribution and toxicokinetics of [³H]-PnTx-G, which is rapidly cleared from blood, and accumulates in the liver and small intestine. The labeling of peripheral and brain adult/embryo rat tissues highlights its ability to cross the intestinal, blood-brain and placental barriers. High-resolution 3D-imaging and in vitro competition studies on rat embryo sections revealed the specificity of [³H]-PnTx-G binding and its selectivity for muscle and neuronal nAChR subtypes (such as α7 subtype). The use of a human perfused cotyledon model and mass spectrometry analyses disclosed that PnTx-G crosses the human placental barrier. The increasing worldwide occurrence of both the dinoflagellate Vulcanodinium rugosum and PnTx-contaminated shellfish, due to climate warming, raises concerns about the potential adverse impact that exposure to pinnatoxins may have for human health.

A Glyphosate-Based Formulation but Not Glyphosate Alone Alters Human Placental Integrity

Glyphosate (G)-based herbicidal formulations, such as the most commonly used one, Roundup (R), are major pesticides used worldwide on food and feed. Pregnant women may be frequently exposed to R compounds. These are composed of G, which is declared as the active principle, and other products contained in formulations, named formulants, which have been declared as inerts and diluents by the manufacturers. These formulants have, in fact, been demonstrated to be much more toxic than G, in particular to placental and embryonic human cells. In this work, we thus compared the effect of G and a GT+ formulation named R, using placental perfusion ex vivo. R, but not G alone, was demonstrated to alter the placental permeability of a known small model molecule, antipyrine. Similar results were observed for the fetal venous flow rate. The transfer of G alone increases with time, but is significantly decreased in presence of its formulants. The perfusion of R provokes a destruction of fetal vessels, as demonstrated by immunohistochemistry. Formulants obviously alter the fetal-placental circulation and placental integrity according to time of exposure. Therefore, G does not appear to be the main toxic agent of R. Formulants, although undeclared, include polyoxyethanolamines, PAHs, or heavy metals, and may be responsible for this toxicity. These compounds are also present in other pesticides. The progressive blood flow reduction due to the toxic compounds of formulations may diminish the nutrient supply to the fetus, alter the development, and may enhance the poisoning effects. Although these are preliminary results, they could at least partially explain some adverse pregnancy outcomes in mothers exposed to pesticides or other environmental pollutants. The debate on glyphosate alone is proven insufficient for the understanding of the toxicity.

HIV in pregnancy: Mother-to-child transmission, pharmacotherapy, and toxicity

An estimated 1.3 million pregnant women were living with HIV in 2018. HIV infection is associated with adverse pregnancy outcomes and all HIV-positive pregnant women, regardless of their clinical stage, should receive a combination of antiretroviral drugs to suppress maternal viral load and prevent vertical fetal infection. Although antiretroviral treatment in pregnant women has undoubtedly minimized mother-to-child transmission of HIV, several uncertainties remain. For example, while pregnancy is accompanied by changes in pharmacokinetic parameters, relevant data from clinical studies are lacking. Similarly, long-term adverse effects of exposure to antiretrovirals on fetuses have not been studied in detail. Here, we review current knowledge on HIV effects on the placenta and developing fetus, recommended antiretroviral regimens, and pharmacokinetic considerations with particular focus on placental transport. We also discuss recent advances in antiretroviral research and potential effects of antiretroviral treatment on placental/fetal development and programming.

Chiral Transplacental Pharmacokinetics of Fexofenadine: Impact of P-Glycoprotein Inhibitor Fluoxetine Using the Human Placental Perfusion Model

PURPOSE

Fexofenadine is a well-identified in vivo probe substrate of P-glycoprotein (P-gp) and/or organic anion transporting polypeptide (OATP). This work aimed to investigate the transplacental pharmacokinetics of fexofenadine enantiomers with and without the selective P-gp inhibitor fluoxetine.

METHODS

The chiral transplacental pharmacokinetics of fexofenadine-fluoxetine interaction was determined using the ex vivo human placenta perfusion model (n = 4). In the Control period, racemic fexofenadine (75 ng of each enantiomer/ml) was added in the maternal circuit. In the Interaction period, racemic fluoxetine (50 ng of each enantiomer/mL) and racemic fexofenadine (75 ng of each enantiomer/mL) were added to the maternal circulation. In both periods, maternal and fetal perfusate samples were taken over 90 min.

RESULTS

The (S)-(-)- and (R)-(+)-fexofenadine fetal-to-maternal ratio values in Control and Interaction periods were similar (~0.18). The placental transfer rates were similar between (S)-(-)- and (R)-(+)-fexofenadine in both Control (0.0024 vs 0.0019 min^-1) and Interaction (0.0019 vs 0.0021 min^-1) periods. In both Control and Interaction periods, the enantiomeric fexofenadine ratios [R-(+)/S-(-)] were approximately 1.

CONCLUSIONS

Our study showed a low extent, slow rate of non-enantioselective placental transfer of fexofenadine enantiomers, indicating a limited fetal fexofenadine exposure mediated by placental P-gp and/or OATP2B1. The fluoxetine interaction did not affect the non-enantioselective transplacental transfer of fexofenadine. The ex vivo placental perfusion model accurately predicts in vivo placental transfer of fexofenadine enantiomers with remarkably similar values (~0.17), and thus estimates the limited fetal exposure.

Placental transfer of the integrase strand inhibitors cabotegravir and bictegravir in the ex-vivo human cotyledon perfusion model

: Data on placental transfer is lacking for the recent HIV integrase inhibitors, bictegravir and cabotegravir, although their future use in pregnancy is to be expected. The objective of this study was to determine their transplacental pharmacokinetics. Maternal-to-fetal transfer was investigated using the open-circuit ex-vivo dually perfused human cotyledon model. Cabotegravir or bictegravir was added to a maternal perfusate containing 2 g/l of human albumin and antipyrine, a marker to validate the cotyledon's viability, and cotyledons were dually perfused for up to 90 min. For cabotegravir, in five experiments, the median (IQR 25-75) concentrations in the maternal and in the fetal compartments were, respectively, 550 ng/ml (344-788) and 48 ng/ml (37-54), with a maternal-to-fetal ratio of 10% (5-16) and a clearance index (in comparison with antipyrine transfer) of 22% (19-28). The median cotyledon accumulation index was 10% (2-21). For bictegravir, in six experiments, the median (IQR 25-75) concentrations in the maternal and in the fetal compartments were, respectively, 1650 ng/ml (1455-1960) and 126 ng/ml (112-142), with a maternal-to-fetal ratio of 7% (6-9.5) and a clearance index (in comparison with antipyrine transfer) of 21% (17-29). The median cotyledon accumulation index was 4% (3-5). Placental transfer of cabotegravir and bictegravir were low. This may not only limit the potential for fetal toxicities but also be a limit to their usefulness at the time of labor and delivery to reduce the risk of vertical HIV transmission. The safety and efficacy of these new integrase inhibitors in pregnancy require more investigation.

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.

Placental transfer and safety in pregnancy of medications under investigation to treat coronavirus disease 2019

Objective

Treatment of coronavirus disease 2019 is mostly symptomatic, but a wide range of medications are under investigation against severe acute respiratory syndrome coronavirus 2. Although pregnant women are excluded from clinical trials, they will inevitably receive therapies whenever they seem effective in nonpregnant patients and even under compassionate use.

Methods

We conducted a review of the literature on placental transfer and pregnancy safety data of drugs under current investigation for coronavirus disease 2019.

Results

Regarding remdesivir, there are no data in pregnant women. Several other candidates already have safety data in pregnant women, because they are repurposed drugs already used for their established indications. Thus, they may be used in pregnancy, although their safety in the context of coronavirus disease 2019 may differ from conventional use. These include HIV protease inhibitors such as lopinavir/ritonavir that have low placental transfer, interferon that does not cross the placental barrier, and hydroxychloroquine or chloroquine that has high placental transfer. There are also pregnancy safety and placental transfer data for colchicine, steroids, oseltamivir, azithromycin, and some monoclonal antibodies. However, some drugs are strictly prohibited in pregnancy because of known teratogenicity (thalidomide) or fetal toxicities (renin-angiotensin system blockers). Other candidates including tocilizumab, other interleukin 6 inhibitors, umifenovir, and favipiravir have insufficient data on pregnancy outcomes.

Conclusion

In life-threatening cases of coronavirus disease 2019, the potential risks of therapy to the fetus may be more than offset by the benefit of curing the mother. Although preclinical and placental transfer studies are required for a number of potential anti-severe acute respiratory syndrome coronavirus 2 drugs, several medications can already be used in pregnant women.

Pharmacokinetics and Placental Transfer of Bupivacaine Enantiomers in HIV-Infected Parturient Women on Antiretroviral Therapy

Bupivacaine, a local anesthetic, is commercialized as a racemic mixture of R-bupivacaine and S-bupivacaine enantiomers. HIV infection increases the expression of placental P-glycoprotein (P-gp), and antiretroviral (ARV) therapy inhibits cytochrome P450 3A and P-gp. The present study evaluates the kinetic disposition of bupivacaine enantiomers in HIV-infected parturient women on ARV therapy. In this study, HIV-infected parturient women (n = 10) treated with zidovudine, lamivudine, lopinavir, and ritonavir were investigated. Anesthesia and/or analgesia was achieved by the administration of 0.5% racemic bupivacaine hydrochloride with 1:200000 epinephrine in the epidural space at doses of 2.5 to 22.5 mg. Maternal serial blood samples were obtained at the time immediately before and 5, 15, 30, 45, and 60 minutes and 2, 4, 6, 8, 10, 12, and 14 hours after administration of the bupivacaine. At the time of delivery, samples of maternal and umbilical cord vein blood were also collected. The results suggest that bupivacaine pharmacokinetics are enantioselective, revealing higher maternal plasma concentrations of the R-bupivacaine enantiomer (area under the total plasma concentration-time curve was calculated by the trapezoid method with extrapolation to infinity/dose_(S)/(R) = 0.91; P < .05). The plasma unbound fraction of the drug (0.09 vs 0.06) and the umbilical cord vein/maternal plasma ratio (0.47 vs 0.39) were higher for the R-bupivacaine enantiomer than the S-bupivacaine enantiomer (P < .05). ARV therapy with ritonavir confers an enantioselective interaction between the enantiomers of bupivacaine and placental P-gp, producing greater inhibition of efflux transport of the R-bupivacaine enantiomer. Possible changes in the well-being of the fetuses of mothers under analgesia may be a consequence of the increased placental transfer of bupivacaine enantiomers to the fetal circulation.

Placental transfer and tissue accumulation of dolutegravir in the ex vivo human cotyledon perfusion model

OBJECTIVE

To determine the transplacental pharmacokinetics of the HIV integrase inhibitor dolutegravir.

STUDY DESIGN

Maternal-to-fetal transfer across the term human placenta was investigated with the ex-vivo dually perfused cotyledon model, in 5 closed-circuit, recirculating experiments. Dolutegravir was added to a maternal perfusate containing antipyrine, a marker to validate the cotyledon's viability, and 2 g/liter of human albumin.

RESULTS

After 3h of recirculating perfusion, the mean (± SD) DTG concentrations in the maternal and in the fetal compartments were respectively 2450 ± 286 ng/mL and 715 ± 369 ng/mL, with a fetal-to-maternal ratio of 34% ± 18% and a clearance index (in comparison with antipyrine transfer) of 79% ± 23%. The mean cotyledon accumulation index was 153% ± 25%.

CONCLUSION

Fetal transplacental exposure to dolutegravir was considerable as well as accumulation in placental tissue. Whether this may lead to risks for the exposed fetus requires more investigation.

Lopinavir/ritonavir treatment increases the placental transfer of bupivacaine enantiomers in human immunodeficiency virus-infected pregnant women

AIMS

The present study evaluated the placental transfer and amniotic fluid distribution of bupivacaine enantiomers in health pregnant women and in human immunodeficiency virus (HIV)-infected pregnant women receiving epidural anaesthesia for caesarean section.

METHODS

Twelve HIV-infected pregnant women (HIV group) were treated long-term (at least 8 weeks) with lopinavir/ritonavir (400/100 mg twice daily), and 12 healthy pregnant women (Control group) who submitted to epidural anaesthesia with racemic bupivacaine (75 mg) during caesarean section were investigated. At delivery, samples of maternal and fetal blood and amniotic fluid were collected (10-20 min after drug administration).

RESULTS

The placental transfer ratio of bupivacaine enantiomers was significantly higher among the pregnant women from the HIV group when compared with those from the Control group (Mann-Whitney test, P ≤ 0.05). Placental transfer ratios (median and 25th - 75th percentiles) for (+)-(R)-bupivacaine were 0.58 (0.38-0.82) in the HIV group vs. 0.25 (0.18-0.33) in the Control group, and for (-)-(S)-bupivacaine, they were 0.54 (0.34-0.69) in the HIV group vs. 0.25 (0.19-0.29) in the Control group. The transplacental distribution of bupivacaine was stereoselective only in the HIV group. The umbilical artery/umbilical vein ratio and amniotic fluid/maternal vein ratio were low and nonstereoselective, and no statistically significant differences were observed between the groups.

CONCLUSIONS

This study supports that the placental transfer of both bupivacaine enantiomers was 100% higher in HIV-pregnant women treated with lopinavir/ritonavir when compared with that in healthy pregnant women receiving epidural anaesthesia for caesarean section.

The Role of PXR Genotype and Transporter Expression in the Placental Transport of Lopinavir in Mice

Lopinavir (LPV), an antiretroviral protease inhibitor frequently prescribed in HIV-positive pregnancies, is a substrate of Abcb1 and Abcc2. As differences in placental expression of these transporters were seen in Pregnane X Receptor (PXR) −/− mice, we examined the impact of placental transporter expression and fetal PXR genotype on the fetal accumulation of LPV. PXR +/− dams bearing PXR +/+, PXR +/−, and PXR −/− fetuses were generated by mating PXR +/− female mice with PXR +/− males. On gestational day 17, dams were administered 10 mg/kg LPV (i.v.) and sacrificed 30 min post injection. Concentrations of LPV in maternal plasma and fetal tissue were measured by LC-MS/MS, and transporter expression was determined by quantitative RT-PCR. As compared to the PXR +/+ fetal units, placental expression of Abcb1a, Abcc2, and Abcg2 mRNA were two- to three-fold higher in PXR −/− fetuses (p < 0.05). Two-fold higher fetal:maternal LPV concentration ratios were also seen in the PXR +/+ as compared to the PXR −/− fetuses (p < 0.05), and this significantly correlated to the placental expression of Abcb1a (r = 0.495; p < 0.005). Individual differences in the expression of placental transporters due to genetic or environmental factors can impact fetal exposure to their substrates.

Placental Origins of Chronic Disease

Epidemiological evidence links an individual's susceptibility to chronic disease in adult life to events during their intrauterine phase of development. Biologically this should not be unexpected, for organ systems are at their most plastic when progenitor cells are proliferating and differentiating. Influences operating at this time can permanently affect their structure and functional capacity, and the activity of enzyme systems and endocrine axes. It is now appreciated that such effects lay the foundations for a diverse array of diseases that become manifest many years later, often in response to secondary environmental stressors. Fetal development is underpinned by the placenta, the organ that forms the interface between the fetus and its mother. All nutrients and oxygen reaching the fetus must pass through this organ. The placenta also has major endocrine functions, orchestrating maternal adaptations to pregnancy and mobilizing resources for fetal use. In addition, it acts as a selective barrier, creating a protective milieu by minimizing exposure of the fetus to maternal hormones, such as glucocorticoids, xenobiotics, pathogens, and parasites. The placenta shows a remarkable capacity to adapt to adverse environmental cues and lessen their impact on the fetus. However, if placental function is impaired, or its capacity to adapt is exceeded, then fetal development may be compromised. Here, we explore the complex relationships between the placental phenotype and developmental programming of chronic disease in the offspring. Ensuring optimal placentation offers a new approach to the prevention of disorders such as cardiovascular disease, diabetes, and obesity, which are reaching epidemic proportions.

Maternal use of drug substrates of placental transporters and the effect of transporter-mediated drug interactions on the risk of congenital anomalies

BACKGROUND

A number of transporter proteins are expressed in the placenta, and they facilitate the placental transfer of drugs. The inhibition of P-glycoprotein (P-gp) was previously found to be associated with an increase in the risk of congenital anomalies caused by drug substrates of this transporter. We now explore the role of other placental transporter proteins.

METHODS

A population-based case-referent study was performed using cases with congenital anomalies (N = 5,131) from EUROCAT Northern Netherlands, a registry of congenital anomalies. The referent population (N = 31,055) was selected from the pregnancy IADB.nl, a pharmacy prescription database.

RESULTS

Ten placental transporters known to have comparable expression levels in the placenta to that of P-gp, were selected in this study. In total, 147 drugs were identified to be substrates, inhibitors or inducers, of these transporters. Fifty-eight of these drugs were used by at least one mother in our cases or referent population, and 28 were used in both. The highest user rate was observed for the substrates of multidrug resistance-associated protein 1, mainly folic acid (6% of cases, 8% of referents), and breast cancer resistance protein, mainly nitrofurantoin (2.3% of cases, 2.9% of referents). In contrast to P-gp, drug interactions involving substrates of these transporters did not have a significant effect on the risk of congenital anomalies.

CONCLUSIONS

Some of the drugs which are substrates or inhibitors of placental transporters were commonly used during pregnancy. No significant effect of transporter inhibition was found on fetal drug exposure, possibly due to a limited number of exposures.

P-Glycoprotein-Mediated Drug Interactions in Pregnancy and Changes in the Risk of Congenital Anomalies: A Case-Reference Study

Introduction

Drug use in pregnancy is very common but may cause harm to the fetus. The teratogenic effect of a drug is partly dependent on the drug level in the fetal circulation, which is associated with the transport across the placenta. Many drugs are substrates of P-glycoprotein (P-gp), an efflux transporter that acts as a protective barrier for the fetus. We aim to identify whether drug interactions associated with P-gp promote any changes in fetal drug exposure, as measured by the risk of having children with congenital anomalies.

Methods

In this study, cases (N = 4634) were mothers of children with congenital anomalies registered in the EUROCAT Northern Netherlands registry, and the reference population were mothers of children (N = 25,126) from a drug prescription database (IADB.nl).

Results

Drugs that are associated with P-gp transport were commonly used in pregnancy in cases (10 %) and population (12 %). Several drug classes, which are substrates for P-gp, were shown to have a higher user rate in mothers of cases with specific anomalies. The use of this subset of drugs in combination with other P-gp substrates increased the risk for specific anomalies (odds ratio [OR] 4.17, 95 % CI 1.75–9.91), and the addition of inhibitors further increased the risk (OR 13.03, 95 % CI 3.37–50.42). The same pattern of risk increment was observed when the drugs were analyzed separately according to substrate specificity.

Conclusions

The use of drugs associated with P-gp transport was common during pregnancy. For several drug classes associated with specific anomalies, P-gp-mediated drug interactions are associated with an increased risk for those specific anomalies.

Electronic supplementary material

The online version of this article (doi:10.1007/s40264-015-0299-3) contains supplementary material, which is available to authorized users.

Antiretroviral Drugs in Meconium: Detection for Different Gestational Periods of Exposure

OBJECTIVES

To determine whether antiretroviral (ARV) medications can be detected in meconium from second or third trimester, labor and delivery (L&D), or postnatal exposures.

STUDY DESIGN

Twenty ARV medications were quantified by liquid chromatography-tandem mass spectrometry in 598 meconium samples from uninfected infants born to pregnant women with HIV enrolled in the Pediatric HIV/AIDS Cohort Study.

RESULTS

ARV detection in meconium following third trimester exposure was 85.7%-94.4% for all ARVs except stavudine (0%, n = 2), likely because of low doses and a high limit for quantification. Of 107 samples with some second trimester only ARV exposures, meconium was positive for only lopinavir, tenofovir, or efavirenz in 11.8%-14.3% of exposed neonates; administration of these ARVs occurred between gestational weeks 25-28 in the positive samples. Days without lopinavir or tenofovir before delivery significantly correlated with decreasing concentrations of lopinavir and tenofovir in meconium. Tenofovir and lamivudine concentrations significantly correlated with increasing gestational age among infants with continuous second and third trimester exposure. Zidovudine given during L&D or for neonatal prophylaxis was detected in 95.1% and 94.6% of meconium samples, respectively.

CONCLUSIONS

Changes in ARV treatments during pregnancy offered a unique opportunity to investigate ARV detection in meconium. ARVs in meconium primarily reflect third trimester ARV exposures, although 6 of 107 second trimester only exposures were detected. Zidovudine administration during L&D was detected in meconium indicating potential urine contamination or rapid incorporation into meconium. These data will improve interpretation of meconium drug test results.

Placental transfer of darunavir in an ex vivo human cotyledon perfusion model

Placental transfer of the HIV protease inhibitor darunavir was investigated in 5 term human cotyledons perfused with darunavir (1,000 ng/ml) in the maternal to fetal direction. The mean (± the standard deviation [SD]) fetal transfer rate (FTR) (fetal/maternal concentration at steady state from 30 to 90 min) was 15.0%±2.1%, and the mean (±SD) clearance index (darunavir FTR/antipyrine FTR) was 40.3%±5.8%. This shows that darunavir crosses the placenta at a relatively low rate, resulting in fetal exposure.

[Placental transfer of drugs]

With more than 830,000 live births in France, a great number of pregnant women are concerned by a treatment during pregnancy and many questions revolve around appreciating medication-related risks during pregnancy. The human placenta is the interface between mother and fetus and remains difficult to study for ethical reasons. Placental transfer of drugs from mother to fetus is dependent on their physicochemical properties, maternal and fetal factors and placental factors. The human placental perfusion model is the only experimental model to study human placental transfer of drugs in organized placental tissue. In vitro models utilizing cell cultures are mostly limited to the investigation of cellular toxicity along pregnancy or specific transfer mechanisms, such as their interaction with transporters. Taking advantage of the complementarity of these models, it will be possible to develop a rational use of drugs during this period.

Safety of protease inhibitors in HIV-infected pregnant women

The dire conditions of the human immunodeficiency virus/acquired immune deficiency syndrome epidemic and the immense benefits of antiretroviral prophylaxis in prevention of mother-to-child transmission far outweigh the potential for adverse effects and undeniably justify the rapid and widespread use of this therapy, despite incomplete safety data. Highly active antiretroviral therapy has now become standard care, and more than half the validated regimens include protease inhibitors. This paper reviews current knowledge of the safety of these drugs during pregnancy, in terms of maternal and fetal outcomes. Transfer of protease inhibitors across the placenta is known to be minimal, and current data about birth defects and fetal malignancies are reassuring. Maternal liver function and glucose metabolism should be monitored in women treated with protease inhibitor-based regimens, but concerns about the development of maternal resistance, should treatment be discontinued, have been shown to be groundless. Neonates should be screened for hematologic abnormalities, although these are rarely severe or permanent and are not usually related to the protease inhibitor component of the antiretroviral combination. Current findings concerning pre-eclampsia and growth restriction are discordant, and further research is needed to address the question of placental vascular complications. The increased risk of preterm birth attributed to protease inhibitors should be interpreted with caution considering the discrepant results and the multitude of confounding factors often overlooked. Although data are thus far reassuring, further research is needed to shed light on unresolved controversies about the safety of protease inhibitors during pregnancy.

Hair and plasma data show that lopinavir, ritonavir, and efavirenz all transfer from mother to infant in utero, but only efavirenz transfers via breastfeeding

BACKGROUND

As efforts intensify to eliminate perinatal HIV transmission, understanding kinetics of maternal-to-child transfer of antiretrovirals during pregnancy and breastfeeding is critical. Antiretroviral levels in plasma, cord blood, and breastmilk reflect exposure over short intervals. Hair concentrations reflect cumulative exposure and can uniquely quantify in utero transfer of maternal medications to infants. We measured plasma and hair antiretroviral levels in HIV-infected Ugandan mothers and their infants at delivery and during breastfeeding to assess transfer.

METHODS

HIV-infected pregnant women were randomized to lopinavir/ritonavir- or efavirenz-based therapy in a larger trial (the Prevention of Malaria and HIV disease in Tororo, PROMOTE). At 0, 8, and 12 weeks postpartum, plasma antiretroviral levels were measured in 117 mother-infant pairs; hair levels were assayed at 12 weeks. Ratios and correlations of infant:maternal concentrations were calculated.

RESULTS

By 12 weeks, 90.4% of mothers reported exclusive breastfeeding. Hair and plasma levels over time suggest moderate (47%) to extensive (87%) in utero transfer of lopinavir and ritonavir, respectively, but negligible transfer of either via breastfeeding. Moderate transfer of efavirenz occurs during pregnancy and breastfeeding (40% cumulative; 15% during breastfeeding). Despite differences in exposure, no infant seroconversions or correlations between infant hair/plasma antiretroviral levels and adverse effects were observed.

CONCLUSIONS

Using a unique approach combining hair and plasma data, we found that different antiretrovirals have distinct kinetics of mother-to-infant transfer. Efavirenz transfers during both pregnancy and breastfeeding, whereas lopinavir and ritonavir transfer only in utero. Further study of the degree and timing of maternal-to-child transfer by antiretroviral will help optimize strategies that protect infants and minimize toxicities during periods of risk.

Prescribing without evidence - pregnancy

Prescribing of medicines during pregnancy is common, and for some groups of women is essential for maintaining maternal and therefore fetal health. Pregnant women and prescribers are rightly concerned, however, about the potential adverse fetal effects of medicines. These may include fetal death or stillbirth, congenital malformations, developmental impairment, neonatal effects or late carcinogenesis. It is therefore essential that the risks and benefits for mother and fetus are considered carefully before prescribing in pregnancy. This is often challenging because of the paucity of information available. To complicate the issue further, drug pharmacokinetics are commonly altered in pregnancy, potentially affecting optimal dosing as well as interpretation of plasma concentration measurements, with specific information on individual drugs seldom available. Most drugs cross the placenta, especially lipophilic drugs and those with low plasma protein binding. Active membrane transporters also have an important role in enhancing or preventing drug transfer, although this is not yet clearly understood. Animal studies have limited applicability to humans because of species-specific effects, and clinical trials in pregnancy are only undertaken in special circumstances. Prescribers therefore need to rely on observational studies of fetal outcomes following drug exposure in human pregnancy. These often involve limited numbers, and data are also subject to confounding and bias, making interpretation difficult. It therefore remains essential that appropriate mechanisms for systematic data collection, including congenital malformation registries, teratology information services, pregnancy registers and linked population registries, are maintained and enhanced to increase the amount and quality of information available.

Current toxicological aspects on drug and chemical transport and metabolism across the human placental barrier

INTRODUCTION

Placenta plays an obligatory role in fetal growth and development by performing a multitude of functions, including embryo implantation, transport of nutrients and elimination of metabolic waste products and endocrine activity. Drugs and chemicals can transfer across the placental barrier from mother to fetus either by passive diffusion mechanisms and/or via a network of active transporters, which may lead to potential fetotoxicity effects. Placenta also expresses a wide variety of enzymes, being capable of metabolizing a large diversity of drugs and chemicals to metabolites of lower or even higher toxicity than parent compounds.

AREAS COVERED

The present review aims to summarize the current toxicological aspects in the emerging topic of drug transport and metabolism across the human placental barrier.

EXPERT OPINION

There is an emerging demand for accurate assessment of drug transport and metabolism across the human placental barrier, on the basis of a high throughput screening process in the early stages of drug design, to avoid drug candidates from potential fetotoxicity effects. In this aspect, combined studies, which take into account in vivo and in vitro investigations, as well as the ex vivo perfusion method and the recently developed computer-aided technologies, may significantly contribute to this direction.

Drug Interactions at the Human Placenta: What is the Evidence?

Pregnant women (and their fetuses) are treated with a significant number of prescription and non-prescription medications. Interactions among those drugs may affect their efficacy and toxicity in both mother and fetus. Whereas interactions that result in altered drug concentrations in maternal plasma are detectable, those involving modulation of placental transfer mechanisms are rarely reflected by altered drug concentrations in maternal plasma. Therefore, they are often overlooked. Placental-mediated interactions are possible because the placenta is not only a passive diffusional barrier, but also expresses a variety of influx and efflux transporters and drug-metabolizing enzymes. Current data on placental-mediated drug interactions are limited. In rodents, pharmacological or genetic manipulations of placental transporters significantly affect fetal drug exposure. In contrast, studies in human placentae suggest that the magnitude of such interactions is modest in most cases. Nevertheless, under certain circumstances, such interactions may be of clinical significance. This review describes currently known mechanisms of placental-mediated drug interactions and the potential implications of such interactions in humans. Better understanding of those mechanisms is important for minimizing fetal toxicity from drugs while improving their efficacy when directed to treat the fetus.

Atazanavir in pregnancy: impact on neonatal hyperbilirubinemia

OBJECTIVE

To study the impact on the neonate of maternal antiretroviral therapy with atazanavir (ATV).

STUDY DESIGN

An observational study of 22 HIV-infected women receiving, for clinical indications, antiretroviral therapy with ATV 300 mg and ritonavir 100mg during pregnancy and their 23 HIV infants (including a twin pair).

RESULTS

Mothers had received ATV for a median duration of 19 months [range 3-49] by delivery. At delivery, plasma HIV-RNA was <40 copies/mL in all patients. Liver enzymes were normal in 19/22 patients, but one woman had grade 3-4 liver toxicity. Maternal serum bilirubin concentrations were above the upper limit of normal in most patients, with grade 3 toxicity in 5 patients. All but one woman had trough ATV concentrations during pregnancy above the minimum effective concentration. The median cord blood ATV concentration was 130 ng/mL [range<30-758]; the cord/maternal ratio was 21%. All neonates were born at term [median 38.2 weeks]. Three neonates had mildly elevated AST transaminase levels. Bilirubin concentrations at birth were significantly higher than maternal concentrations, with a median of 44 μm/L [range 24-129]; values on days 2-3 were 63 [8-212]. Five neonates had jaundice requiring phototherapy, without liver damage, and recovered without sequelae.

CONCLUSION

Neonates whose mothers were treated with ATV should be monitored for hyperbilirubinemia, which may be due to placental transfer of unconjugated bilirubin from the mother and/or a direct effect of transplacental ATV on bilirubin metabolism in the fetus.

ABCB1 and ABCG2 expression in the placenta and fetus: an interspecies comparison

IMPORTANCE OF THE FIELD

ABCB1 and ABCG2 are efflux transporters which have a major impact on the pharmacological behavior of numerous drugs. They are expressed, for example, in the intestine, liver, kidney, BBB and placenta. It has become evident that ABCB1 and ABCG2 modify the pharmaco/toxicokinetics in the placenta and fetus and may consequently affect the outcome of pregnancy.

AREAS COVERED IN THIS REVIEW

Comprehensive literature searches were done using PubMed (until June 2010) to identify publications on ABCB1 and ABCG2 expression in placenta and fetal tissues in human, mouse, rat, guinea-pig and rabbit.

WHAT THE READER WILL GAIN

In this review, we aim to provide an overview of the current knowledge on the ABCB1 and ABCG2 transporter expression profiles in the placenta and fetal tissues in humans relative to other species.

TAKE HOME MESSAGE

The available information on ABCB1 and ABCG2 temporal expression profiles in placenta and fetus indicates rather good correlation among human, mouse and rat although some specific differences have been reported. However, at this point no detailed comparisons or comparative functional data are available. Detailed knowledge on the expression patterns and functional activity of ABCB1 and ABCG2 transporters placenta and developing embryo/fetus in different species could possibly help the interspecies extrapolation.

[Contributions of the ex vivo human perfused placenta in the study of placental transfer of drugs]

Perfused human placental lobule was developed during the 1970s. Only this model respects the anatomical features of the human placenta. This approach allows different technical conditions (concentrations of drugs…) without ethical problems. Limitations of this ex vivo model are detailed in this review, also its recent contributions in better understanding of placental passage of drugs.