Safety, tolerability, and pharmacokinetics of Aurora kinase B inhibitor AZD2811: a phase 1 dose-finding study in patients with advanced solid tumours.

BACKGROUND: AZD2811 is a potent, selective Aurora kinase B inhibitor. We report the dose-escalation phase of a first-in-human study assessing nanoparticle-encapsulated AZD2811 in advanced solid tumours. METHODS: AZD2811 was administered in 12 dose-escalation cohorts (2-h intravenous infusion; 15‒600 mg; 21-/28-day cycles) with granulocyte colony-stimulating factor (G-CSF) at higher doses. The primary objective was determining safety and maximum tolerated/recommended phase 2 dose (RP2D). RESULTS: Fifty-one patients received AZD2811. Drug exposure was sustained for several days post-dose. The most common AZD2811-related adverse events (AEs) were fatigue (27.3%) at ≤200 mg/cycle and neutropenia (37.9%) at ≥400 mg/cycle. Five patients had dose-limiting toxicities: grade (G)4 decreased neutrophil count (n = 1, 200 mg; Days 1, 4; 28-day cycle); G4 decreased neutrophil count and G3 stomatitis (n = 1 each, both 400 mg; Day 1; 21-day cycle); G3 febrile neutropenia and G3 fatigue (n = 1 each, both 600 mg; Day 1; 21-day cycle +G-CSF). RP2D was 500 mg; Day 1; 21-day cycle with G-CSF on Day 8. Neutropenia/neutrophil count decrease were on-target AEs. Best overall responses were partial response (n = 1, 2.0%) and stable disease (n = 23, 45.1%). CONCLUSIONS: At RP2D, AZD2811 was tolerable with G-CSF support. Neutropenia was a pharmacodynamic biomarker. CLINICAL TRIAL REGISTRATION: NCT02579226.

Concentration-QT modelling in early clinical oncology settings: Simulation evaluation of performance.

AIMS: Concentration-QT modelling (C-QTc) of first-in-human data has been rapidly adopted as the primary evaluation of QTc interval prolongation risk. Here, we evaluate the performance of C-QTc in early oncology settings (i.e., patients, no placebo or supratherapeutic dose, 3 + 3 designs). METHODS: C-QTc performance was evaluated across three oncology scenarios using a simulation-estimation approach: (scen1) typical dose-escalation testing six dose levels (n = 21); (scen2) small dose-escalation testing two dose levels (n = 9); (scen3) expansion cohorts at one dose level (n = 6-140). True ΔΔQTc effects ranged from 3 ms ("no effect") to 20 ms ("large effect"). Performance was assessed based on the upper limit of the ΔQTc two-sided 90% CI against a threshold of 10 or 20 ms. RESULTS: The performance against the 10 ms threshold was limited based on C-QTc data from typical dose escalation (scen1) and acceptable performance was observed only for relatively large expansions (n ≥ 45; scen3). Performance against the 20 ms threshold was acceptable based on C-QTc data from a typical dose escalation (scen1) or dose expansion cohort n > 10 (scen3). In general, pooling C-QTc data from dose escalation and expansion cohorts substantially improved the performance and reduced the ΔQTc 90% CI width. CONCLUSION: C-QTc performance appeared limited using a 10 ms threshold, but acceptable against a 20 ms threshold. Selection of threshold may be informed by the benefit-risk balance in a specific disease area. Acceptable precision (i.e., confidence intervals) of the estimated ΔQTc, regardless of its magnitude, can be facilitated by pooling data from dose escalation and expansion cohorts.

Clinical evaluation of the potential drug-drug interactions of savolitinib: Interaction with rifampicin, itraconazole, famotidine or midazolam.

AIMS: We investigated savolitinib pharmacokinetics (PK) when administered alone or in combination with rifampicin, itraconazole or famotidine, and investigated midazolam PK when administered with or without savolitinib in healthy males. METHODS: Savolitinib PK was evaluated before/after: rifampicin (600 mg once daily [QD] for 5 days); itraconazole (200 mg QD for 5 days); a single dose of famotidine (40 mg QD) 2 hours before savolitinib. Midazolam PK was evaluated before/after midazolam (1 mg QD) with or without savolitinib (600 mg QD). Each study enrolled 20, 16, 16 and 14 volunteers, respectively. Plasma samples were collected to determine the effect on PK. RESULTS: The geometric mean ratios (GMR, %) (90% confidence intervals [CIs]) for savolitinib alone and in combination for Cmax , AUC respectively, were 45.4 (41.4-49.9), 38.5 (34.2-43.3) in the rifampicin study (n = 18); 105.2 (87.7-126.3), 108.4 (96.3-122.1) in the itraconazole study (n = 16); and 78.8 (67.7-91.7), 87.4 (81.2-94.2) in the famotidine study (n = 16). The GMRs (90% CIs) for midazolam alone and in combination with savolitinib for Cmax , AUC respectively, were 84.1 (70.0-101.0), 96.7 (92.4-101.1) (n = 14). Savolitinib alone or in combination was well tolerated. CONCLUSIONS: Co-dosing of rifampicin significantly reduced exposure to savolitinib vs savolitinib alone; co-dosing of itraconazole or midazolam with savolitinib had no clinically significant effect on savolitinib or midazolam PK, respectively. Co-dosing of famotidine with savolitinib reduced exposure to savolitinib, although this was not considered clinically meaningful. No new savolitinib-related safety findings were observed.

A phase 1/2 study of the combination of acalabrutinib and vistusertib in patients with relapsed/refractory B-cell malignancies.

In a phase 1b study of acalabrutinib (a covalent Bruton tyrosine kinase (BTK) inhibitor) in combination with vistusertib (a dual mTORC1/2 inhibitor) in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL), multiple ascending doses of the combination as intermittent or continuous schedules of vistusertib were evaluated. The overall response rate was 12% (3/25). The pharmacodynamic (PD) profile for acalabrutinib showed that BTK occupancy in all patients was >95%. In contrast, PD analysis for vistusertib showed variable inhibition of phosphorylated 4EBP1 (p4EBP1) without modulation of AKT phosphorylation (pAKT). The pharmacokinetic (PK)/PD relationship of vistusertib was direct for TORC1 inhibition (p4EBP1) but did not correlate with TORC2 inhibition (pAKT). Cell-of-origin subtyping or next-generation sequencing did not identify a subset of DLBCL patients with clinical benefit; however, circulating tumor DNA dynamics correlated with radiographic response. These data suggest that vistusertib does not modulate targets sufficiently to add to the clinical activity of acalabrutinib monotherapy. Clinicaltrials.gov identifier: NCT03205046.

Physiologically Based Pharmacokinetic Modeling for Selumetinib to Evaluate Drug-Drug Interactions and Pediatric Dose Regimens.

Selumetinib (ARRY-142886), an oral, potent and highly selective allosteric mitogen-activated protein kinase kinase 1/2 inhibitor, is approved by the US Food and Drug Administration for the treatment of pediatric patients aged ≥2 years with neurofibromatosis type 1 with symptomatic, inoperable plexiform neurofibromas. A physiologically based pharmacokinetic (PBPK) model was constructed to predict plasma concentration-time profiles of selumetinib, and to evaluate the impact of coadministering moderate cytochrome P450 (CYP) 3A4/2C19 inhibitors/inducers. The model was also used to extrapolate pharmacokinetic exposures from older children with different body surface area to guide dosing in younger children. This model was built based on physiochemical data and clinical in vivo drug-drug interaction (DDI) studies with itraconazole and fluconazole, and verified against data from an in vivo rifampicin DDI study and an absolute bioavailability study. The pediatric model was updated by changing system-specific input parameters using the Simcyp pediatric module. The model captured the observed selumetinib pharmacokinetic profiles and the interactions with CYP inhibitors/inducers. The predictions from the PBPK model showed a DDI effect of 30% to 40% increase or decrease in selumetinib exposure when coadministered with moderate CYP inhibitors or inducers, respectively, which was used to inform dose management and adjustments. The pediatric PBPK model was applied to simulate exposures in specific body surface area brackets that matched those achieved with a 25 mg/m2 dose in SPRINT clinical trials. The pediatric PBPK model was used to guide the dose for younger patients in a planned pediatric clinical study.

Population pharmacokinetics and exposure-response of selumetinib and its N-desmethyl metabolite in pediatric patients with neurofibromatosis type 1 and inoperable plexiform neurofibromas.

PURPOSE: Selumetinib (ARRY-142886) is a potent, selective, MEK1/2 inhibitor approved in the US for the treatment of children (≥ 2 years) with neurofibromatosis type 1 (NF1) and symptomatic, inoperable plexiform neurofibromas (PN). We characterized population pharmacokinetics (PK) of selumetinib and its active N-desmethyl metabolite, evaluated exposure-safety/efficacy relationships, and assessed the proposed therapeutic dose of 25 mg/m2 bid based on body surface area (BSA) in this patient population. METHODS: Population PK modeling and covariate analysis (demographics, formulation, liver enzymes, BSA, patients/healthy volunteers) were based on pooled PK data from adult healthy volunteers (n = 391), adult oncology patients (n = 83) and pediatric patients with NF1-PN (n = 68). Longitudinal selumetinib/metabolite exposures were predicted with the final model. Exposure-safety/efficacy analyses were applied to pediatric patients (dose levels: 20, 25, 30 mg/m2 bid). RESULTS: Selumetinib and metabolite concentration-time courses were modeled using a joint compartmental model. Typical selumetinib plasma clearance was 11.6 L/h (95% CI 11.0-12.2 L/ h). Only BSA had a clinically relevant (> 20%) impact on exposure, supporting BSA-based administration in children. Selumetinib and metabolite exposures in responders (≥ 20% PN volume decrease from baseline) and non-responders were largely overlapping, with medians numerically higher in responders. No clear relationships between exposure and safety events were established; exposure was not associated with key adverse events (AEs) including rash acneiform, diarrhea, vomiting, and nausea. CONCLUSION: Findings support continuous selumetinib 25 mg/m2 bid in pediatric patients. Importantly, the updated dosing nomogram ensures that patients will receive a clinically active, yet tolerable, dose regardless of differences in BSA and allows dose reductions, if necessary.

Parent and Metabolite Concentration-QT Modeling to Evaluate QT-Interval Prolongation at Savolitinib Therapeutic Doses.

Savolitinib is an oral, potent, and highly selective MET-tyrosine kinase inhibitor under investigation in various tumor types. A thorough QT study evaluated effects on QT interval after a 600-mg single savolitinib dose in healthy subjects. We report exposure-response (E-R) modeling from this study to characterize the effects of savolitinib and its metabolites, M2 and M3, on QTc changes. In a novel application, in vitro potencies against hERG current provided mechanistic support to model the metabolites' effects. The hERG IC50 estimates (95% CI) were 25.8 (22.2-29.9) and 22.6 (14.7-34.6) µM for parent and M2, respectively. The E-R was described by both linear and Emax models, with exposure captured by an active moiety that consisted of savolitinib and M2 concentrations, weighted by the hERG IC50 ratio (1.14). The maximal increase in ΔΔQTcF and EC50 estimates (95% CI) was 18.5 (9.2-27.7) ms and 5709 (2889-8529) nM, respectively. Ignoring M2 contribution resulted in under prediction of QTcF prolongation in the hypothetical case of inhibited M2 clearance; at 300 mg Cmax, the mean (90% CI) of ∆∆QTcF was 9.0 (5.7-12.6) and 5.9 (2.9-8.9) ms using the hERG-informed and parent-only linear models, respectively. Simulations in normal setting confirmed modest QTcF prolongation with 600 mg, but not 300 mg. Using the linear model, the mean (90% CI) maximum ΔΔQTcF were 12.3 (8.6-16.2) and 5.5 (2.6-8.5) ms for 600 and 300 mg, respectively. Further clinical studies will monitor cardiac safety to assess the clinical significance of QT-interval prolongation with savolitinib.

Normal fat mass cannot be reliably estimated in typical pharmacokinetic studies.

PURPOSE: An influential covariate for pharmacokinetics is (body) size. Recently, the method of estimation of normal fat mass (NFM) has been advocated. Here, the relative contribution of fat mass, estimated as a fraction fat (Ffat), is used to explain differences in pharmacokinetic parameters. This concept is more and more applied. However, it remains unclear whether NFM can be reliably estimated in these typical studies. METHODS: We performed an evaluation of the reliability of NFM estimation in a typical study size (n = 30), otherwise best-case scenario, by means of a pharmacokinetic simulation study. Several values of Ffat were investigated. RESULTS: In a typical pharmacokinetic study, high imprecision was observed for NFM parameter estimates over a range of scenarios. For example, in a scenario where the true value of Ffat on clearance was 0.5, we found a 95% confidence interval of - 0.1 to 2.1, demonstrating a low precision. The implications for practice are that one could conclude that fat-free mass best describes the relationship of the pharmacokinetics with body size, while the true relationship was between fat-free mass and total body weight. Consequently, this could lead to incorrect extrapolation of pharmacokinetics to extreme body sizes. CONCLUSION: In typical pharmacokinetic studies, NFM should be used with caution because the Ffat estimates have low precision. The estimation of Ffat should always be preceded by careful study design evaluation before planning a study, to ensure that the design and sample size is sufficient to apply this potentially useful methodology.

Assessment of Maternal and Fetal Dolutegravir Exposure by Integrating Ex Vivo Placental Perfusion Data and Physiologically-Based Pharmacokinetic Modeling.

Antiretroviral therapy during pregnancy reduces the risk of vertical HIV-1 transmission. However, drug dosing is challenging as pharmacokinetics (PK) may be altered during pregnancy. We combined a pregnancy physiologically-based pharmacokinetic (PBPK) modeling approach with data on placental drug transfer to simulate maternal and fetal exposure to dolutegravir (DTG). First, a PBPK model for DTG exposure in healthy volunteers was established based on physiological and DTG PK data. Next, the model was extended with a fetoplacental unit using transplacental kinetics obtained by performing ex vivo dual-side human cotyledon perfusion experiments. Simulations of fetal exposure after maternal dosing in the third trimester were in accordance with clinically observed DTG cord blood data. Furthermore, the predicted fetal trough plasma concentration (Ctrough ) following 50 mg q.d. dosing remained above the concentration that results in 90% of viral inhibition. Our integrated approach enables simulation of maternal and fetal DTG exposure, illustrating this to be a promising way to assess DTG PK during pregnancy.

Importance of Prospective Studies in Pregnant and Breastfeeding Women Living With Human Immunodeficiency Virus.

Recently, the US Food and Drug Administration and European Medicines Agency issued warnings on the use of dolutegravir and darunavir/cobicistat for treatment of pregnant women living with human immunodeficiency virus (HIV). It took 3-5 years to identify the risks associated with the use of these antiretroviral drugs, during which time pregnant women were exposed to these drugs in clinical care, outside of controlled clinical trial settings. Across all antiretroviral drugs, the interval between registration of new drugs and first data on pharmacokinetics and safety in pregnancy becoming available is around 6 years. In this viewpoint, we provide considerations for clinical pharmacology research to provide safe and effective treatment of pregnant and breastfeeding women living with HIV and their children. These recommendations will lead to timelier availability of safety and pharmacokinetic information needed to develop safe treatment strategies for pregnant and breastfeeding women living with HIV, and are applicable to other chronic disease areas requiring medication during pregnancy.

Evaluating darunavir/ritonavir dosing regimens for HIV-positive pregnant women using semi-mechanistic pharmacokinetic modelling.

BACKGROUND: Darunavir 800 mg once (q24h) or 600 mg twice (q12h) daily combined with low-dose ritonavir is used to treat HIV-positive pregnant women. Decreased total darunavir exposure (17%-50%) has been reported during pregnancy, but limited data on unbound exposure are available. OBJECTIVES: To evaluate total and unbound darunavir exposures following standard darunavir/ritonavir dosing and to explore the value of potential optimized darunavir/ritonavir dosing regimens for HIV-positive pregnant women. PATIENTS AND METHODS: A population pharmacokinetic analysis was conducted based on data from 85 women. The final model was used to simulate total and unbound darunavir AUC0-τ and Ctrough during the third trimester of pregnancy, as well as to assess the probability of therapeutic exposure. RESULTS: Simulations predicted that total darunavir exposure (AUC0-τ) was 24% and 23% lower in pregnancy for standard q24h and q12h dosing, respectively. Unbound darunavir AUC0-τ was 5% and 8% lower compared with post-partum for standard q24h and q12h dosing, respectively. The probability of therapeutic exposure (unbound) during pregnancy was higher for standard q12h dosing (99%) than for q24h dosing (94%). CONCLUSIONS: The standard q12h regimen resulted in maximal and higher rates of therapeutic exposure compared with standard q24h dosing. Darunavir/ritonavir 600/100 mg q12h should therefore be the preferred regimen during pregnancy unless (adherence) issues dictate q24h dosing. The value of alternative dosing regimens seems limited.

Pharmacokinetics of HIV-Integrase Inhibitors During Pregnancy: Mechanisms, Clinical Implications and Knowledge Gaps.

Prevention of mother-to-child transmission of HIV and optimal maternal treatment are the most important goals of antiretroviral therapy in pregnant women with HIV. These goals may be at risk due to possible reduced exposure during pregnancy caused by physiological changes. Limited information is available on the impact of these physiological changes. This is especially true for HIV-integrase inhibitors, a relatively new class of drugs, recommended first-line agents and hence used by a large proportion of HIV-infected patients. Therefore, the objective of this review is to provide a detailed overview of the pharmacokinetics of HIV-integrase inhibitors in pregnancy. Second, this review defines potential causes for the change in pharmacokinetics of HIV-integrase inhibitors during pregnancy. Despite increased clearance, for raltegravir 400 mg twice daily and dolutegravir 50 mg once daily, exposure during pregnancy seems adequate; however, for elvitegravir, the proposed minimal effective concentration is not reached during pregnancy. Lower exposure to these drugs may be caused by increased hormone levels and, subsequently, enhanced drug metabolism during pregnancy. The pharmacokinetics of bictegravir and cabotegravir, which are under development, have not yet been evaluated in pregnant women. New studies need to prospectively assess whether adequate exposure is reached in pregnant women using these new HIV-integrase inhibitors. To further optimize antiretroviral treatment in pregnant women, studies need to unravel the underlying mechanisms behind the changes in the pharmacokinetics of HIV-integrase inhibitors during pregnancy. More knowledge on altered pharmacokinetics during pregnancy and the underlying mechanisms contribute to the development of effective and safe antiretroviral therapy for HIV-infected pregnant women.

Development and validation of an UPLC-MS/MS bioanalytical method for simultaneous quantification of the antiretroviral drugs dolutegravir, elvitegravir, raltegravir, nevirapine and etravirine in human plasma.

Dolutegravir, elvitegravir, raltegravir, nevirapine and etravirine are antiretroviral drugs used as part of combined antiretroviral treatment for HIV-infection. For quantification of these drugs in human K2EDTA plasma samples an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) bioanalytical method was developed and validated. Stable isotope labeled internal standards were used for each analyte. Simple protein precipitation with methanol was implemented to prepare plasma samples of at least 50 µL. The method was validated for dolutegravir, elvitegravir, raltegravir, nevirapine and etravirine over the ranges 9.7-9700, 52-10,470, 9.7-9730, 73-14,680 and 15-3010 ng/mL, respectively. Within-run and between-run accuracy and precision were within ±15% of the nominal concentration for quality controls at high, medium and low concentrations, and within ±20% at the lower limit of quantification for all analytes. Recovery was ≥76% and reproducible. Long-term stability of patient plasma samples was demonstrated for at least 12 months at -40 °C (4 months for etravirine). Currently, this robust method with a run time of 10 min is used in clinical research and for therapeutic drug monitoring of these frequently used antiretroviral drugs.

Efavirenz pharmacokinetics during pregnancy and infant washout.

BACKGROUND: Limited data exist on efavirenz pharmacokinetics in HIV-positive pregnant women and neonatal washout. METHODS: HIV-infected pregnant women receiving 600 mg efavirenz once daily had intensive steady-state 24-h pharmacokinetics profiles during the second trimester (2T), third trimester (3T) and 6-12 weeks postpartum (PP). Maternal and umbilical cord blood samples were drawn at delivery and neonatal washout pharmacokinetics were determined. Therapeutic targets were the estimated 10th percentile efavirenz area under the concentration-time curve (AUC) in non-pregnant historical controls (40.0 µg•h/ml) and a trough concentration (C24 h) of 1 µg/ml. Data were prospectively collected within two trials: IMPAACT P1026s (United States) and PANNA (Europe). RESULTS: Among 42 women studied, 15, 42 and 40 had efavirenz pharmacokinetic data available in 2T, 3T and PP, respectively. Median (range) 3T age 33 (20.7-43.5) years, weight 74 (50-132) kg and gestational age 33.4 (28.4-37.9 weeks). Efavirenz AUC during the 3T (60 µg•h/ml) was similar to that reported in non-pregnant adults (58 µg•h/ml). Exposure in the 2T was lower, but within the 0.80-1.25 range. C24 concentrations during pregnancy were lower compared to historical controls on 600 mg efavirenz, however, they were similar to the C24 concentrations after equally potent dose of 400 mg efavirenz. Cord blood/maternal plasma concentration ratio (range) was 0.67 (0.36-0.95). Among 23 infants with washout data available, median (interquartile range) elimination half-life was 65.6 h (40.6-129). HIV RNA viral loads at delivery were <400 and <50 copies/ml for 96.7% and 86.7% of women, respectively. In 3T and PP, respectively, 8/41 (19%) and 6/40 (15%) had AUC below target; 7/41 (17%) and 3/39 (8%) had C24 below target. CONCLUSIONS: Efavirenz exposure was similar during pregnancy compared with PP, C24 was in line with C24 after 400 mg equipotent efavirenz dosing. Efavirenz readily crossed the placenta and infant elimination half-life was over twice that of maternal participants. Clincaltrials.gov identifiers: NCT00825929 and NCT00042289.

The Impact of Dose and Simultaneous Use of Acid-Reducing Agents on the Effectiveness of Vemurafenib in Metastatic BRAF V600 Mutated Melanoma: a Retrospective Cohort Study.

BACKGROUND: The impact of dose and simultaneous use of acid-reducing agents (ARAs) on the effectiveness of vemurafenib is unknown. OBJECTIVES: To determine the association between progression of metastatic BRAF V600 mutated melanoma and (1) dose reductions of vemurafenib and (2) simultaneous use of vemurafenib and ARAs. PATIENT AND METHODS: A retrospective cohort study of 112 first-line vemurafenib users for melanoma was conducted (March 2012-March 2016), using electronic patient records and pharmacy dispensing records of a Dutch academic hospital. Cox regression analysis was used to estimate the risk of progression with full-dose (n = 64) versus reduced-dose vemurafenib (n = 48) and with simultaneous use of vemurafenib and ARAs (n = 35) versus vemurafenib alone (n = 77). Analyses were adjusted for age and sex. RESULTS: In total, disease progression occurred in 55% of treated patients on vemurafenib, with a median progression-free survival of 6.0 (95% confidence interval [CI] 5.0-6.9) months. Compared to patients on vemurafenib alone, there was no increased risk of progression among patients requiring vemurafenib at a reduced dose or among patients receiving simultaneous therapy with vemurafenib and ARAs. In addition, there was no increased risk of progression among patients who used reduced-dose vemurafenib and ARAs versus those receiving full-dose vemurafenib as sole therapy. However, a tendency for progression was observed among patients who used full-dose vemurafenib and ARAs versus full-dose vemurafenib alone (adjusted hazard ratio [HRa] 2.37; 95% CI 0.97-5.76), which became statistically significant in a sensitivity analysis (HRa 4.56; 95% CI 1.51-13.75). CONCLUSIONS: There was no association between the use of vemurafenib in a reduced dose or the simultaneous use of vemurafenib and ARAs and the risk of progression. In addition, there was no association between the simultaneous use of vemurafenib in a reduced dose and ARAs and the risk of progression. However, patients tolerating  full-dose vemurafenib simultaneously with ARAs might have an increased risk of progression. This finding requires prospective validation.

A Mechanism-Based Population Pharmacokinetic Analysis Assessing the Feasibility of Efavirenz Dose Reduction to 400 mg in Pregnant Women.

BACKGROUND: Reducing the dose of efavirenz can improve safety, reduce costs, and increase access for patients with HIV infection. According to the World Health Organization, a similar dosing strategy for all patient populations is desirable for universal roll-out; however, it remains unknown whether the 400 mg daily dose is adequate during pregnancy. METHODS: We developed a mechanistic population pharmacokinetic model using pooled data from women included in seven studies (1968 samples, 774 collected during pregnancy). Total and free efavirenz exposure (AUC24 and C12) were predicted for 400 (reduced) and 600 mg (standard) doses in both pregnant and non-pregnant women. RESULTS: Using a 400 mg dose, the median efavirenz total AUC24 and C12 during the third trimester of pregnancy were 91 and 87% of values among non-pregnant women, respectively. Furthermore, the median free efavirenz C12 and AUC24 were predicted to increase during pregnancy by 11 and 15%, respectively. CONCLUSIONS: It was predicted that reduced-dose efavirenz provides adequate exposure during pregnancy. These findings warrant prospective confirmation.

Prediction of Fetal Darunavir Exposure by Integrating Human Ex-Vivo Placental Transfer and Physiologically Based Pharmacokinetic Modeling.

BACKGROUND: Fetal antiretroviral exposure is usually derived from the cord-to-maternal concentration ratio. This static parameter does not provide information on the pharmacokinetics in utero, limiting the assessment of a fetal exposure-effect relationship. OBJECTIVE: The aim of this study was to incorporate placental transfer into a pregnancy physiologically based pharmacokinetic model to simulate and evaluate fetal darunavir exposure at term. METHODS: An existing and validated pregnancy physiologically based pharmacokinetic model of maternal darunavir/ritonavir exposure was extended with a feto-placental unit. To parameterize the model, we determined maternal-to-fetal and fetal-to-maternal darunavir/ritonavir placental clearance with an ex-vivo human cotyledon perfusion model. Simulated maternal and fetal pharmacokinetic profiles were compared with observed clinical data to qualify the model for simulation. Next, population fetal pharmacokinetic profiles were simulated for different maternal darunavir/ritonavir dosing regimens. RESULTS: An average (±standard deviation) maternal-to-fetal cotyledon clearance of 0.91 ± 0.11 mL/min and fetal-to-maternal clearance of 1.6 ± 0.3 mL/min was determined (n = 6 perfusions). Scaled placental transfer was integrated into the pregnancy physiologically based pharmacokinetic model. For darunavir 600/100 mg twice a day, the predicted fetal maximum plasma concentration, trough concentration, time to maximum plasma concentration, and half-life were 1.1, 0.57 mg/L, 3, and 21 h, respectively. This indicates that the fetal population trough concentration is higher or around the half-maximal effective darunavir concentration for a resistant virus (0.55 mg/L). CONCLUSIONS: The results indicate that the population fetal exposure after oral maternal darunavir dosing is therapeutic and this may provide benefits to the prevention of mother-to-child transmission of human immunodeficiency virus. Moreover, this integrated approach provides a tool to prevent fetal toxicity or enhance the development of more selectively targeted fetal drug treatments.

Lowered Rilpivirine Exposure During the Third Trimester of Pregnancy in Human Immunodeficiency Virus Type 1-Infected Women.

BACKGROUND: The use of antiretroviral therapy during pregnancy is important for control of maternal human immunodeficiency virus (HIV) disease and the prevention of perinatal HIV transmission. Physiological changes during pregnancy can reduce antiretroviral exposure. We studied the pharmacokinetics of rilpivirine 25 mg once daily in HIV-1-infected women during late pregnancy. METHODS: We conducted a nonrandomized, open-label, multicenter, phase 4 study. HIV-infected pregnant women receiving rilpivirine 25 mg once daily were included. Intensive 24-hour pharmacokinetic sampling was performed in the third trimester and at least 2 weeks postpartum. Pharmacokinetic parameters were calculated by noncompartmental analysis. RESULTS: Sixteen subjects were included. Geometric mean ratios of third trimester vs postpartum were 0.55 (90% confidence interval [CI], .46-.66) for the 24-hour area under the concentration-time curve (AUC0-24h); 0.65 (90% CI, .55-.76) for the maximum concentration; and 0.51 (90% CI, .41-.63) for the minimum observed concentration (Cmin). Four of 16 (25%) subjects had Cmin below the target concentration (0.04 mg/L) in the third trimester of pregnancy. No subtherapeutic levels were observed postpartum. No detectable viral loads were observed in this study. All newborns tested negative for HIV. No birth defects were reported. The median (range, n = 5) rilpivirine cord-to-maternal plasma concentration ratio was 0.50 (range, .35-.81). CONCLUSIONS: Rilpivirine exposure is substantially lowered during late pregnancy. Despite lower exposure, virologic suppression was maintained and no perinatal transmission was observed. Overall, these results suggest that rilpivirine 25 mg once daily may be an alternative treatment option for HIV-1-infected pregnant women who are virologically suppressed, in settings where therapeutic drug monitoring and/or close viral load monitoring are feasible to detect suboptimal antiretroviral therapy. CLINICAL TRIALS REGISTRATION: NCT00825929.