Population approach to analyze the pharmacokinetics of free and total lopinavir in HIV-infected pregnant women and consequences for dose adjustment

Successful Prediction of Human Fetal Exposure to P-Glycoprotein Substrate Drugs Using the Proteomics-Informed Relative Expression Factor Approach and PBPK Modeling and Simulation

Many women take drugs during their pregnancy to treat a variety of clinical conditions. To optimize drug efficacy and reduce fetal toxicity, it is important to determine or predict fetal drug exposure throughout pregnancy. Previously, we developed and verified a maternal-fetal physiologically based pharmacokinetic (m-f PBPK) model to predict fetal K_p,uu (unbound fetal plasma AUC/unbound maternal plasma AUC) of drugs that passively cross the placenta. Here, we used in vitro transport studies in Transwell, in combination with our m-f PBPK model, to predict fetal K_p,uu of drugs that are effluxed by placental P-glycoprotein (P-gp)-namely, dexamethasone, betamethasone, darunavir, and lopinavir. Using Transwell, we determined the efflux ratio of these drugs in hMDR1-MDCK^cP-gpKO cells, in which human P-gp was overexpressed and the endogenous P-gp was knocked out. Then, using the proteomics-informed efflux ratio-relative expressive factor approach, we predicted the fetal K_p,uu of these drugs at term. Finally, to verify our predictions, we compared them with the observed in vivo fetal K_p,uu at term. The latter was estimated using our m-f PBPK model and published fetal [umbilical vein (UV)]/maternal plasma drug concentrations obtained at term (UV/maternal plasma). Fetal K_p,uu predictions for dexamethasone (0.63), betamethasone (0.59), darunavir (0.17), and lopinavir (0.08) were successful, as they fell within the 90% confidence interval of the corresponding in vivo fetal K_p,uu (0.30-0.66, 0.29-0.71, 0.11-0.22, 0.04-0.19, respectively). This is the first demonstration of successful prediction of fetal K_p,uu of P-gp drug substrates from in vitro studies. SIGNIFICANCE STATEMENT: For the first time, using in vitro studies in cells, this study successfully predicted human fetal K_p,uu of P-gp substrate drugs. This success confirms that the m-f PBPK model, combined with the ER-REF approach, can successfully predict fetal drug exposure to P-gp substrates. This success provides increased confidence in the use of the ER-REF approach, combined with the m-f PBPK model, to predict fetal K_p,uu of drugs (transported by P-gp or other transporters), both at term and at earlier gestational ages.

Neglecting Plasma Protein Binding in COVID-19 Patients Leads to a Wrong Interpretation of Lopinavir Overexposure

Boffito et al. recalled the critical importance to correctly interpret protein binding. Changes of lopinavir pharmacokinetics in coronavirus disease 2019 (COVID‐19) are a perfect illustration. Indeed, several studies described that total lopinavir plasma concentrations were considerably higher in patients with severe COVID‐19 than those reported in patients with HIV. These findings have led to a reduction of the dose of lopinavir in some patients, hypothesizing an inhibitory effect of inflammation on lopinavir metabolism. Unfortunately, changes in plasma protein binding were never investigated. We performed a retrospective cohort study. Data were collected from the medical records of patients hospitalized for COVID‐19 treated with lopinavir/ritonavir in intensive care units or infectious disease departments of Toulouse University Hospital (France). Total and unbound concentrations of lopinavir, C reactive protein, albumin, and alpha‐1‐acid glycoprotein (AAG) levels were measured during routine care on the same samples. In patients with COVID‐19, increased total lopinavir concentration is the result of an increased AAG‐bound lopinavir concentration, whereas the unbound concentration remains constant, and insufficient to reduce the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2) viral load. Although international guidelines have recently recommended against using lopinavir/ritonavir to treat severe COVID‐19, the description of lopinavir pharmacokinetics changes in COVID‐19 is a textbook case of the high risk of misinterpretation of a total drug exposure when changes in protein binding are not taken into consideration.

Studies on the Efficacy, Potential Cardiotoxicity and Monkey Pharmacokinetics of GLP-26 as a Potent Hepatitis B Virus Capsid Assembly Modulator

While treatment options are available for hepatitis B virus (HBV), there is currently no cure. Anti-HBV nucleoside analogs and interferon-alpha 2b rarely clear HBV covalently closed circular DNA (cccDNA), requiring lifelong treatment. Recently, we identified GLP-26, a glyoxamide derivative which modulates HBV capsid assembly. The impact of GLP-26 on viral replication and integrated DNA was assessed in an HBV nude mouse model bearing HBV transfected AD38 xenografts. At day 45 post-infection, GLP-26 reduced HBV titers by 2.3–3 log₁₀ versus infected placebo-treated mice. Combination therapy with GLP-26 and entecavir reduced HBV log₁₀ titers by 4.6-fold versus placebo. Next, we examined the pharmacokinetics (PK) in cynomolgus monkeys administered GLP-26 via IV (1 mg/kg) or PO (5 mg/kg). GLP-26 was found to have 34% oral bioavailability, with a mean input time of 3.17 h. The oral dose produced a mean peak plasma concentration of 380.7 ng/mL, observed 0.67 h after administration (~30-fold > in vitro EC₉₀ corrected for protein binding), with a mean terminal elimination half-life of 2.4 h and a mean area under the plasma concentration versus time curve of 1660 ng·hr/mL. GLP-26 was 86.7% bound in monkey plasma. Lastly, GLP-26 demonstrated a favorable toxicity profile confirmed in primary human cardiomyocytes. Thus, GLP-26 warrants further preclinical development as an add on to treatment for HBV infection.

Effect of Pregnancy on Unbound Raltegravir Concentrations in the ANRS 160 RalFe Trial

A population pharmacokinetic model was developed to explore the pharmacokinetics modification of unbound raltegravir during pregnancy. The RalFe ANRS160 study was a nonrandomized, open-label, multicenter trial enrolling HIV-infected pregnant women receiving a combined antiretroviral regimen containing 400 mg raltegravir twice daily. Biological samples were collected during the third trimester of pregnancy (between 30 and 37 weeks of gestational age) and at postpartum (4 to 6 weeks after delivery). A population pharmacokinetic model was developed with Monolix software. A total of 360 plasma samples were collected from 43 women during pregnancy and postpartum. The unbound raltegravir was described by a one-compartment model with a transit compartment with first-order absorption, evolving to bound raltegravir (by a linear binding to albumin) or metabolism to RAL-glucuronide or to a first-order elimination, with a circadian rhythm. During pregnancy, the absorption was decreased and delayed and the raltegravir elimination clearance and glucuronidation increased by 37%. Median total and unbound area under the curve from 0 to 12 h significantly decreased by 36% and 27% during pregnancy. Median total trough concentration (C _trough) decreased significantly in the evening (28%); however, the median total C _trough in the morning, unbound C _trough in the morning, and unbound C _trough in the evening showed a nonsignificant decrease of 16%, 1%, and 15%, respectively, during pregnancy compared to the postpartum period. This is the first study reporting the pharmacokinetics of unbound raltegravir during pregnancy. As unbound C _trough did not significantly decrease during the third trimester, the pregnancy effect on raltegravir unbound concentrations was not considered clinically relevant. (This study has been registered at ClinicalTrials.gov under identifier NCT02099474.).

Drug dosing during pregnancy-opportunities for physiologically based pharmacokinetic models

Drugs can have harmful effects on the embryo or the fetus at any point during pregnancy. Not all the damaging effects of intrauterine exposure to drugs are obvious at birth, some may only manifest later in life. Thus, drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus. Dosing of drugs during pregnancy is often empirically determined and based upon evidence from studies of non-pregnant subjects, which may lead to suboptimal dosing, particularly during the third trimester. This review collates examples of drugs with known recommendations for dose adjustment during pregnancy, in addition to providing an example of the potential use of PBPK models in dose adjustment recommendation during pregnancy within the context of drug-drug interactions. For many drugs, such as antidepressants and antiretroviral drugs, dose adjustment has been recommended based on pharmacokinetic studies demonstrating a reduction in drug concentrations. However, there is relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Examples of using pregnancy PBPK models to predict feto-maternal drug exposures and their applications to facilitate and guide dose assessment throughout gestation are discussed.

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.

Pretreatment and non-specific binding in ultrafiltration device: Impact on protease inhibitor quantification

INTRODUCTION

Ultrafiltration (UF) is used to separate unbound drugs; however, non-specific binding (NSB) may be a limiting factor of this technique. Pretreatment of UF devices has been suggested to reduce NSB. Therefore, the pretreatment methodologies for UF devices were evaluated in order to test their effectiveness in reducing NSB of protease inhibitors (PIs).

METHODOLOGY

Two PIs (lopinavir-LPV and ritonavir-RTV) were tested. UF devices were pretreated with ultrapure water, Tween-20 or Tween-80. To evaluate the NSB, after UF devices being pretreated, ultrafiltrate solutions containing the analytes at two concentrations (low and high) were used. Samples were quantified by LC-MS/MS.

RESULTS

UF devices pretreated with Tween-5% had the lowest NSB for both analytes. NSB values varied between 7 and 11% at low concentration 16-34% at high LPV concentration, respectively. For RTV, NSB was approximately 6% for low concentration and 18% for high concentration. Failure to completely remove Tween in UF devices could results in an overestimation of NSB.

CONCLUSION

Pretreatment of UF device with Tween and subsequent removal proved to be effective in reducing NSB of PI.

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.

Placental transfer of elvitegravir and cobicistat in an ex-vivo human cotyledon double perfusion model

OBJECTIVE

To determine the transplacental pharmacokinetics of the HIV integrase strand transfer inhibitor elvitegravir and of cobicistat, a cytochrome P450 inhibitor used as a pharmacoenhancer in antiretroviral therapy.

DESIGN AND METHODS

Maternal-to-fetal transfer across the term human placenta was investigated with the ex-vivo dually perfused cotyledon model, in seven open-circuit experiments and 10 closed-circuit (recirculating) experiments. Elvitegravir and cobicistat were added to a maternal perfusate containing 2 g/l of human serum albumin and antipyrine, as a marker to validate the cotyledon's viability. Elvitegravir and cobicistat concentrations were measured using ultraperformance liquid chromatography coupled with tandem mass spectrometry.

RESULTS

For elvitegravir, in open-circuit experiments the mean (±SD) fetal transfer rate (FTR) (fetal/maternal concentration at steady state from 30 to 90 min) was 19 ± 13% and the mean clearance index was 0.46 ± 0.21; in the closed-circuit model, after 3 h of perfusion the FTR was 20 ± 10% and the mean accumulation index was 12.28 ± 5.57. For cobicistat, in the open perfusions the FTR was 23 ± 13% and the mean clearance index was 0.63 ± 0.34; in the closed perfusions after 3 h the fetal-to-maternal ratio of cobicistat was 21 ± 11%. The mean accumulation index was 3.46 ± 2.19 CONCLUSION:: The two models concurred to show moderate placental transfer of elvitegravir and cobicistat across the placenta as well as elvitegravir accumulation in the placenta tissue. Whether this may lead to toxicities and modifications in fetal or placental metabolism requires clinical studies.

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.

Model-Based Analysis of Unbound Lopinavir Pharmacokinetics in HIV-Infected Pregnant Women Supports Standard Dosing in the Third Trimester

Physiological changes during pregnancy can affect drug pharmacokinetics. Here we present a population pharmacokinetic model to describe the longitudinal change of unbound lopinavir/ritonavir (LPV/RTV) PK parameters with gestational age, and to predict unbound LPV concentrations under different dosing regimens. The changes in apparent intrinsic clearances of LPV and RTV during pregnancy are described using an exponential function of gestational age. The unbound fractions of LPV/RTV are not significantly different between pregnancy and postpartum. Simulation reveals that despite increases in LPV intrinsic clearance, effective LPV inhibitory quotient (IQ) values are predicted with the standard dosing (400/100 mg b.i.d.) in >90% of simulations, with ≤4‐fold increase in viral IC₅₀. As viral susceptibility decreases, higher doses increase the likelihood of efficacy. With ≥40‐fold increases in IC₅₀, IQs suggest alternate regimens be considered. This approach refines previous LPV PK reports, and supports that standard dosing is effective with susceptible virus.