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BACKGROUND The World Health Organization (WHO) 2019 antiretroviral treatment guidelines recommend use of optimal treatment regimens in all populations. Dolutegravir-based regimens are the preferred first-line and second-line treatment in infants and children with HIV 4 weeks of age and above. There is an urgent need for optimal pediatric formulations of dolutegravir as single-entity (SE) and fixed-dose combination (FDC) to ensure correct dosing and adherence for swallowing and palatability. This article outlines the chronology of dolutegravir pediatric formulation development as granules and conventional and dispersible tablets in a total of 5 pharmacokinetic studies evaluating the relative bioavailability of dolutegravir SE and FDC formulations in healthy adults. METHODS The relative bioavailability studies were 2-part, Phase I, open-label, randomized studies in healthy adults. Dolutegravir SE study compared conventional dolutegravir 50 and 25 mg with equivalent conventional 10-mg and dispersible 5-mg tablets, respectively. Subsequently, dolutegravir FDC study compared adult FDC of abacavir/dolutegravir/lamivudine and adult FDC of dolutegravir/lamivudine with their respective pediatric FDC formulations, taken as dispersion immediately or swallowed whole. RESULTS As observed in previous studies, dolutegravir administered as dispersion (granules/dispersible tablets) showed relatively higher bioavailability compared with conventional tablets. The bioavailability of dolutegravir dispersible tablets (both SE and FDC) was approximately 1.6-fold higher when compared with conventional tablets. In addition, the bioavailability of abacavir/lamivudine was not impacted by dispersible formulation. CONCLUSIONS These studies demonstrate the successful development of pediatric dolutegravir-containing formulations as SE and FDC that permit pediatric dosing in line with WHO recommendations.

Pharmacokinetics, safety, and tolerability of abacavir 600 mg/dolutegravir 50 mg/lamivudine 300 mg were assessed in this phase 1, single‐arm, open‐label, single‐dose study in fasted healthy male (n = 4) and female (n = 8) participants of Japanese heritage. Participants received a single dose of abacavir 600 mg/dolutegravir 50 mg/lamivudine 300 mg after an 8‐hour fast, with safety assessments and blood samples for pharmacokinetic parameters collected through 72 hours after dosing. Geometric mean maximum plasma concentrations were 5.22 μg/mL (time to maximum concentration [tmax], 1.01 hours) for abacavir, 4.13 μg/mL (tmax, 3.50 hours) for dolutegravir, and 3.35 μg/mL (tmax, 2.98 hours) for lamivudine. Geometric mean area under the concentration‐time curve values were 18.20, 71.60, and 16.60 μg • h/mL for abacavir, dolutegravir, and lamivudine, respectively. No adverse events were reported, and no clinically significant findings were observed in laboratory values, physical examinations, or 12‐lead electrocardiographic parameters. Single‐tablet administration of abacavir 600 mg/dolutegravir 50 mg/lamivudine 300 mg was well tolerated in Japanese participants. Exposure to abacavir and lamivudine was comparable with that seen in previous studies. A modest increase in exposure to dolutegravir vs previous clinical studies was observed but is not expected to impact the clinical management of HIV‐1 or increase the risk for adverse events.

Dolutegravir 50 mg (DTG) and rilpivirine 25 mg (RPV) are a newly approved 2-drug regimen for the treatment of HIV in virally suppressed patients. A 2-part study evaluated the relative bioavailability and food effect of five experimental fixed-dose combination (FDC) tablet formulations of DTG/RPV. When given with a moderate- or high-fat meal, the absorption of both DTG and RPV was increased, resulting in higher exposures. As per product labelling, DTG/RPV FDC should be taken with a meal.

Summary Background Primary analyses of the SWORD-1 and SWORD-2 trials at 48 weeks showed that switching to a two-drug regimen of dolutegravir plus rilpivirine was non-inferior to continuing a standard three-drug or four-drug antiretroviral regimen for maintenance of virological suppression in people with HIV-1. Here, we present efficacy and safety data from the 100-week analysis of the trials. Methods SWORD-1 and SWORD-2 are identically designed, randomised, open-label phase 3 studies at 65 centres in 13 countries and 60 centres in 11 countries, respectively. Adults aged 18 years or older who were on a standard three-drug or four-drug antiretroviral therapy (ART) and had had fewer than 50 HIV-1 RNA copies per mL of plasma for at least 6 months were randomly assigned (1:1) to 50 mg dolutegravir plus 25 mg rilpivirine orally once daily (early-switch group) or to continue their standard regimen for 52 weeks before switching to the dolutegravir plus rilpivirine combination (ie, the late-switch group). In this analysis of week 100 data, the efficacy endpoint of interest was the proportion of participants with fewer than 50 copies of HIV-1 RNA per mL of plasma (per the US Food and Drug Administration snapshot algorithm). This outcome was assessed in all randomly assigned participants who received at least one dose of the study drug. Data were analysed after the last participant completed week 100 (Sept 15, 2017) and verified through the data cutoff (Nov 21, 2017). SWORD-1 and SWORD-2 are registered with ClinicalTrials.gov, numbers NCT02429791 and NCT02422797, respectively. Findings 513 participants were randomly assigned to dolutegravir plus rilpivirine (ie, the early-switch group) and 511 to continue their standard ART regimen, 477 of whom then switched to dolutegravir plus rilpivirine at week 52 (ie, the late-switch group). At week 100, 456 (89% [95% CI 86–92]) of 513 participants in the early-switch group and 444 (93% [91–95]) of 477 in the late-switch group had fewer than 50 HIV-1 RNA copies per mL. Drug-related adverse events occurred in 103 (20%) participants in the early-switch group and 58 (12%) in the late-switch group. The most common drug-related adverse events were headache (11 participants in the early-switch group [2%] vs eight [2%] in the late-switch group) and nausea (eight [2%] vs five [1%]). Interpretation The combination of dolutegravir plus rilpivirine sustained virological suppression of HIV-1, was associated with a low frequency of virological failure, and had a favourable safety profile, which support its use as a nucleoside reverse transcriptase inhibitor-sparing and protease inhibitor-sparing alternative to three-drug regimens that reduces overall exposure to ART. Funding ViiV Healthcare and Janssen Pharmaceutica.

In children aged ≤4 years, the relative bioavailability of lamivudine oral solution was 37% lower than that of a tablet formulation. An open‐label, four‐way crossover study was conducted in healthy adults to evaluate the effect of sorbitol, a common liquid excipient, on the pharmacokinetics of lamivudine oral solution (ClinicalTrials.gov identifier, NCT02634073). Sixteen subjects were randomized to one of four sequences consisting of four doses of lamivudine 300 mg (10 mg/mL) alone or with sorbitol 3.2, 10.2, or 13.4 g. Sorbitol 3.2, 10.2, and 13.4 g decreased lamivudine maximum concentration (C max) by 28%, 52%, and 55% and area under the concentration–time curve from time 0 to 24 h (AUC0‐24) by 20%, 39%, and 44%, respectively. Three subjects (19%) reported five nonserious adverse events (one drug‐related). The dose‐dependent effects of sorbitol on lamivudine C max and AUC0‐24 reveal an absorption‐based interaction that may decrease lamivudine exposure in patients coadministered sorbitol‐containing medicines.

A complete 2-drug regimen of dolutegravir at 50 mg and rilpivirine at 25 mg was approved to treat HIV-1 infection in virologically suppressed patients after demonstrating acceptable efficacy and tolerability. This study investigated the bioequivalence and pharmacokinetics of the fixed-dose combination tablet compared with those of separate tablets. Secondary endpoints were the tolerability and safety of the fixed-dose combination tablet. In this open-label, randomized-sequence, 2-way crossover trial, single doses of the fixed-dose combination tablet (the test treatment) and the combination of separate tablets (the reference treatment) were administered to healthy adults after a moderate-fat meal, with a 21-day washout between treatments. Pharmacokinetic samples were collected through 12 days after dosing. The primary endpoints were the area under the plasma concentration-time curve (AUC) and the maximum concentration of drug in plasma (Cmax). The study employed a prespecified sample size reestimation based on a blind midpoint review of Cmax variability to update the enrollment size to achieve statistical power. Of 118 participants enrolled, 113 received both treatments and underwent pharmacokinetic assessment. The 90% confidence intervals for the geometric least-squares mean ratios for the AUC from 0 h to infinity, the AUC from 0 h to the last quantifiable measurement, and Cmax (test treatment versus reference treatment) were within the bioequivalence range of 0.80 to 1.25 for both drugs, indicating bioequivalence. In this study, a single dose of either treatment was well tolerated overall, with 4% (n = 5) and 3% (n = 3) of participants reporting adverse events considered related to the test and reference treatments, respectively. The dolutegravir-rilpivirine fixed-dose combination tablet is bioequivalent to a combination of separate tablets, and no new safety signals emerged. (This study has been registered at ClinicalTrials.gov under identifier NCT02741557.).

This first-time-in-human, randomized, double-blind, placebo-controlled, dose-escalation study assessed the safety, tolerability, pharmacokinetics, and antiviral activity of GSK2485852, a hepatitis C virus (HCV) NS5B inhibitor, in 27 chronically infected HCV genotype-1 subjects. Subjects received GSK2485852 70, 420, and 70 mg with a moderate fat/caloric meal. Safety, pharmacokinetics, antiviral activity, HCV genotype/phenotype, and interleukin 28B genotype were evaluated. A statistically significant reduction in HCV ribonucleic acid (RNA) was observed after a single dose of 420 mg GSK2485852 (−1.33 log10 IU/mL) compared with placebo (−0.09 log10 IU/mL) at 24 hours post-dose. Subjects receiving 70 mg GSK2485852 were exposed to concentrations above the protein-adjusted 90% effective concentration for a short time; none experienced a significant decline in HCV RNA (−0.47 log10 copies/mL). GSK2485852 was readily absorbed; however, the observed geometric mean maximum plasma concentration (Cmax) and area under the curve (AUC) values were significantly lower than expected due to a higher-than-predicted-oral clearance. Co-administration with food reduced the AUC and Cmax of GSK2485852 by 40% and 70%, respectively. Two metabolites were detected in human blood with one having approximately 50% higher concentrations than those of the parent. GSK2485852 was well-tolerated and exhibited antiviral activity after a single 420 mg dose in HCV subjects.

Aim Lamivudine is used as first line therapy in HIV-infected children. Yet, like many other paediatric drugs, its dose rationale has been based on limited clinical data, without thorough understanding of the effects of growth on drug disposition. Here we use lamivudine to show how a comprehensive population pharmacokinetic model can account for the influence of demographic covariates on exposure (i.e. AUC and Cmax). Methods Data from three paediatric trials were used to describe the pharmacokinetics across the overall population. Modelling was based on a non-linear mixed effects approach. A stepwise procedure was used for covariate model building. Results A one compartment model with first order elimination best described the pharmacokinetics of lamivudine in children. The effect of weight on clearance (CL) and volume of distribution (V) was characterized by an exponential function, with exponents of 0.705 and 0.635, respectively. For a child with median body weight (17.6 kg), CL and V were 16.5 (95% CI 15.2, 17.7) l h−1 and 46.0 (95% CI 42.4, 49.5) l, respectively. There were no differences between formulations (tablet and solution). The predicted AUC(0,12 h) after twice daily doses of 4 mg kg−1 ranged from 4.44 mg l−1 h for children 30 kg. Conclusions The use of meta-analysis is critical to identify the correct covariate-parameter relationships, which must be assessed before a model is applied for predictive purposes (e.g. defining dosing recommendations for children). In contrast to prior modelling efforts, we show that the covariate distribution in the target population must be considered.

Aim Little attention has been paid to the effects of compliance and prescription practice on treatment outcome in HIV-infected children. In this context, an evaluation of the role of covariates on pharmacokinetics is required to establish the impact of differences in dosing regimens. Here we investigate whether a once daily dosing regimen of lamivudine provides comparable exposure to the currently approved paediatric regimen. Methods A hypothetical group of 180 patients between 3 months and 12 years old was used to evaluate the impact of body weight on systemic exposure to lamivudine. Simulation scenarios were evaluated using AUC and Cmax as parameters of interest. The analysis was performed using a population pharmacokinetic model previously implemented in nonmem v.6.2. Results The simulations show that once daily dosing of lamivudine yields comparable exposure to historical values observed in children and adults, both for liquid and solid dosage forms. Simulated steady-state AUC(0–24 h) and Cmax values after once daily doses ranged respectively from 9.95 mg l−1 h and 1.9 mg l−1 for children lighter than 14 kg to 13.75 mg l−1 h and 3.0 mg l−1 for children heavier than 30 kg. These values are comparable or higher than historical values observed after once daily dosing in children and adults. Conclusions Our findings illustrate how dosing regimens can be evaluated taking into account the effects of developmental growth on drug disposition. Most importantly, they suggest that the reduction in dosing frequency to once daily leads to comparable lamivudine exposure, as observed after administration of a twice daily dosing regimen.

This Phase I, randomized, open-label study evaluated the gastric pH-altering effects of omeprazole, a proton pump inhibitor, and the CYP3A enzyme/P-glycoprotein (Pgp)-inhibitory effects of ritonavir, an HIV protease inhibitor, on the pharmacokinetics and safety of the hepatitis C virus (HCV) non-structural protein 5A (NS5A) inhibitor GSK2336805 in healthy male and female subjects. Co-administration of GSK2336805 60 mg with omeprazole decreased GSK2336805 plasma AUC(0-∞) by 10% and Cmax by 18%; no marked effect was observed on t½ . Co-administration of GSK2336805 30 mg with ritonavir increased GSK2336805 plasma AUC(0-∞) by 52%, Cmax by 43%, and t½ by 40%; CL/F was decreased by 34%. All adverse events were minor in intensity. The gastric acid-suppressive effect of omeprazole had minimal impact on the extent and rate of GSK2336805 absorption in vivo; therefore, GSK2336805 may be co-administered with omeprazole without concern about lower GSK2336805 exposures and compromised antiviral efficacy. The modest increases in AUC and Cmax following co-administration of GSK2336805 plus ritonavir suggest that GSK2336805 when given concomitantly with a single CYP3A/Pgp inhibiting drug will not likely require dose adjustment. Final dose recommendation will be based on GSK2336805 efficacy and safety profiles from Phase III trials in HCV-infected patients.

GSK2336805 is an orally bioavailable hepatitis C virus (HCV) inhibitor working through an NS5A-mediated mechanism. This first-time-in-human study was conducted to assess the safety, tolerability, pharmacokinetics, metabolism, and efficacy of GSK2336805 in healthy subjects and subjects infected with HCV genotype 1. We performed a three-part, randomized, double-blind, placebo-controlled study in 46 healthy subjects and 23 HCV-infected subjects. After an overnight fast, healthy subjects received GSK2336805 as 10 mg, 30 mg, 30 mg plus food, and 60 mg in a single dose and 10 mg (7 days), 30 mg (7 days), and 75 mg (14 days) in a once-daily multiple dose. Subjects with HCV received GSK2336805 as a 1- to 120-mg single dose. In subjects with HCV, reductions in HCV RNA were observed within 4 h and a single dose of GSK2336805 of ≥10 mg resulted in a statistically significant ≥2-log reduction in HCV RNA compared with placebo at 24 h postdose. GSK2336805 was readily absorbed in all subjects, and the half-life ( t 1/2 ) was suitable for once-daily dosing. Administration of GSK2336805 with food had no effect on plasma GSK2336805 exposure; however, absorption was delayed, with a median t max (time to maximum concentration of drug in serum) of 4.5 versus 2.0 h. Twenty subjects who received GSK2336805 experienced mild to moderate adverse events; none were serious. GSK2336805 was well tolerated and exhibited rapid, significant antiviral activity after a single dose in HCV-infected subjects. These results support the conduct of further studies evaluating GSK2336805 administered once daily for longer durations in combination with peginterferon, ribavirin, and other direct-acting antivirals. (This study has been registered at ClinicalTrials.gov under registration no. NCT01277692.)

The objective of this study is to assess the effectiveness of physiologically based pharmacokinetic (PBPK) models for simulating human plasma concentration-time profiles for the unique drug dataset of blinded data that has been assembled as part of a Pharmaceutical Research and Manufacturers of America initiative. Combinations of absorption, distribution, and clearance models were tested with a PBPK approach that has been developed from published equations. An assessment of the quality of the model predictions was made on the basis of the shape of the plasma time courses and related parameters. Up to 69% of the simulations of plasma time courses made in human demonstrated a medium to high degree of accuracy for intravenous pharmacokinetics, whereas this number decreased to 23% after oral administration based on the selected criteria. The simulations resulted in a general underestimation of drug exposure (Cmax and AUC0- t ). The explanations for this underestimation are diverse. Therefore, in general it may be due to underprediction of absorption parameters and/or overprediction of distribution or oral first-pass. The implications of compound properties are demonstrated. The PBPK approach based on in vitro-input data was as accurate as the approach based on in vivo data. Overall, the scientific benefit of this modeling study was to obtain more extensive characterization of predictions of human PK from PBPK methods.

Aplaviroc (GW873140) binds specifically to human cellular CC chemokine receptor 5 (CCR5) and demonstrates potent anti-human immunodeficiency virus activity in vitro in the subnanomolar range. In vitro studies show that aplaviroc selectively inhibits the binding of a particular monoclonal antibody, 45531, to CCR5. Based on this observation, a flow cytometry-based assay was developed to determine percentage CCR5 receptor occupancy (RO). CCR5 receptor occupancy was aplaviroc concentration-dependent and related to anti-human immunodeficiency virus activity in vitro. In the clinical setting, CCR5 receptor occupancy in peripheral blood was >98% in all subjects within 2 to 3 hours of dosing, which is consistent with the peak plasma concentrations of drug. Longitudinal analysis in the drug washout period revealed the time to 50% CCR5 receptor occupancy averaged >100 hours, in both human immunodeficiency virus-positive and human immunodeficiency virus-negative subjects, substantially longer than the plasma pharmacokinetic half-life of 3 hours. The duration of CCR5 receptor occupancy appeared to be dose-dependent and associated with antiviral activity as measured by plasma human immunodeficiency virus RNA nadir following 10 days of multiple dose administration. These data demonstrate that the analysis of CCR5 receptor occupancy, in addition to conventional plasma-based pharmacokinetic measures, provides an informative tool to assist in evaluating the pharmacodynamic and antiviral effects of cellular CC chemokine receptor antagonists.

Aplaviroc (APL) was a new CCR5 antagonist that was investigated in two dose-ranging studies with antiretroviral therapy-naïve, human immunodeficiency virus-infected adults: ASCENT, in which 147 subjects were randomized 2:2:1 to receive zidovudine-lamivudine (ZDV-3TC) plus APL 600 mg twice a day (BID), APL 800 mg BID, or efavirenz (EFV), respectively, and EPIC, in which 195 subjects were randomized 2:2:2:1 to receive lopinavir-ritonavir (LPV-RTV) plus APL 200 mg BID, APL 400 mg BID, APL 800 mg once a day, or ZDV-3TC BID, respectively. Both studies (and, ultimately, the clinical development of APL) were discontinued after a mean of 14 weeks of therapy because of higher than anticipated severe liver toxicity; grade 2 or higher treatment-emergent elevations in alanine aminotransferase (ALT) levels were observed in 17/281 (6.0%) APL recipients but only 2/55 (3.6%) control recipients, while grade 2 or higher elevations in total bilirubin levels occurred in 29/281 (10.3%) APL recipients but only 4/55 (7.3%) controls. Two APL recipients developed grade 3 or higher treatment-emergent elevations in both ALT and total bilirubin levels, and one of these individuals had a severe case of hepatic cytolysis that was attributed to APL. Despite the high intersubject variability in APL plasma exposures, a Pearson correlation analysis of the combined study data did not reveal any significant associations between plasma concentrations and the liver enzyme elevations observed during the study. The mechanism for the idiosyncratic hepatotoxicity observed in the clinical trials of APL is unknown but is likely intrinsic to the molecule rather than its novel mechanism of action.

To promptly identify and evaluate liver safety events, an evidence-based liver safety system was created for global Phase I-III clinical trials. The goals of this system included improving clinical trial subject safety, expanding information on liver safety events, and improving data quality across studies by establishing and communicating: Two different algorithms for liver stopping criteria were developed. The most stringent criteria were selected for healthy volunteers in Phase I studies, where no treatment benefit is anticipated and clinical safety data are limited. With an interest in assessing potential liver "tolerance" or adaptation with accruing safety information, slightly higher liver chemistry thresholds were set for Phase II-III studies. This paper will describe the importance of liver safety in drug development, laboratory tests used to monitor liver safety, the rationale for selected liver chemistry subject stopping criteria, and implementation of this safety system.

Aims This study assessed the effects of the CYP3A inhibitors lopinavir/ritonavir (LPV/r) on the steady-state pharmacokinetics (PK) of aplaviroc (APL), a CYP3A4 substrate, in healthy subjects. Methods In Part 1, APL PK was determined in eight subjects who received a single oral 50-mg APL test dose with/without a single dose of 100 mg ritonavir (RTV). Part 2 was conducted as an open-label, single-sequence, three-period repeat dose study in a cohort of 24 subjects. Subjects received APL 400 mg every 12 h (b.i.d.) for 7 days (Period 1), LPV/r 400/100 mg b.i.d. for 14 days (Period 2) and APL 400 mg + LPV/r 400/100 mg b.i.d. for 7 days (Period 3). All doses were administered with a moderate fat meal. PK sampling occurred on day 7 of Periods 1 and 3 and day 14 of Period 2. Results In Part 1, a single RTV dose increased the APL AUC0–∞ by 2.1-fold [90% confidence interval (CI) 1.9, 2.4]. Repeat dose coadministration of APL with LPV/r increased APL exposures to a greater extent with the geometric least squares mean ratios (90% CI) being 7.7 (6.4, 9.3), 6.2 (4.8, 8.1) and 7.1 (5.6, 9.0) for the APL AUC, Cmax, and Cmin, respectively. No change in LPV AUC or Cmax and a small increase in RTV AUC and Cmax (28% and 32%) were observed. The combination of APL and LPV/r was well tolerated and adverse events were mild in severity with self-limiting gastrointestinal complaints most commonly reported. Conclusions Coadministration of APL and LPV/r was well tolerated and resulted in significantly increased APL plasma concentrations.

Aplaviroc is a novel CCR5 antagonist, a class of compounds under investigation as viral entry inhibitors for the treatment of human immunodeficiency virus infection. A modified Cooperstown 5 +1 cocktail was used to assess the drug interaction potential of aplaviroc. Fifteen healthy subjects were administered single oral doses of caffeine (CYP1A2), warfarin (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), and midazolam (CYP3A) alone (reference treatment) and during steady-state administration of aplaviroc (400 mg every 12 hours, test treatment). Metabolite-to-parent area under the plasma concentration versus time curve (AUC) ratios (paraxanthine/caffeine and 5-hydroxyomeprazole/omeprazole), oral clearance (S-warfarin), AUC (midazolam), and metabolite-to-parent urinary excretion ratio (dextrorphan/dextromethorphan) were determined. The test-to-reference treatment ratios (geometric mean ratio and 90% confidence interval) were caffeine, 1.06 (0.97–1.17); S-warfarin, 0.93 (0.76–1.15); omeprazole, 1.07 (0.98–1.16); dextromethorphan, 1.17 (0.97–1.42); midazolam, 1.30 (1.04–1.63). No significant inhibition of CYP1A2, CYP2C9, CYP2C19, or CYP2D6 enzyme activity was observed. Mild inhibition of CYP3A isozymes should not preclude the use of concomitant CYP3A substrates in future clinical studies with aplaviroc.

873140 is a novel CCR5 antagonist with potent in vitro anti-human immunodeficiency virus (HIV) activity. This study was a double-blind, randomized, placebo-controlled, single- and repeat-dose escalation investigation of the safety, pharmacokinetics, and food effect of 873140 in 70 adult subjects. During single-dose escalation, three cohorts (each composed of 10 subjects, with 8 subjects receiving the active drug and 2 subjects receiving the placebo [8 active and 2 placebo]) received doses of 50, 200, 400, 800, and 1,200 mg after an overnight fast, or 400 mg plus a standard high-fat breakfast in an alternating panel design. During repeat-dose escalation, four cohorts (each with 8 active and 2 placebo) received doses of 200, 400, 600, or 800 mg every 12 h (BID) for 8 days. Laboratory safety tests, vital signs, and electrocardiograms (ECGs) were performed at regular intervals, and blood samples were obtained for pharmacokinetics. Single and repeat doses of 50 mg to 800 mg were well tolerated, with no serious adverse events and no grade 3 or 4 adverse events. The mild-tomoderate side effects were primarily gastrointestinal and included abdominal cramping, nausea, and diarrhea. No specific trends in laboratory parameters or clinically significant ECG changes were noted. Plasma 873140 concentrations increased rapidly; the median time to maximum concentration of drug in serum was 1.75 to 5 h. The median area under the plasma concentration-time profile (AUC) and the maximum concentration of drug in serum (Cmax) ranged from 127 ng · h/ml and 24 ng/ml at 200 mg BID to 329 ng · h/ml and 100 ng/ml at 800 mg BID, respectively. Food consumption increased the AUC and Cmax by a mean of 1.7- and 2.2-fold, respectively. The pharmacokinetic and safety profile supports the continued investigation of 873140 with HIV-infected subjects. Despite an improvement in morbidity and mortality attributable to highly active antiretroviral therapy (HAART), the emergence of multiclass drug-resistant strains and the problematic toxicities associated with HAART warrant the development of new classes of therapies for human immunodeficiency virus (HIV) infection. Most of the currently approved antiretroviral drugs are targeted toward the inhibition of viral enzymes. The identification of the HIV coreceptors CC chemokine receptor 5 (CCR5) and CXC chemokine receptor 4 (CXCR4) on the cell surface has resulted in an improved understanding of viral entry and fusion. These discoveries have led to promising new targets for drug development (7).

GSK2336805 is a hepatitis C virus NS5A inhibitor in clinical development for the treatment of chronic hepatitis C virus infection. This was a single-center, randomized, double-blind, placebo-controlled, two-period crossover study in healthy adults to evaluate the effects of a single 150-mg dose of GSK2336805 on echocardiographic measures of contractility. GSK2336805 had no effect on ejection fraction, and there was no significant correlation between GSK2336805 plasma concentration and ejection fraction. (This study has been registered at Clinicaltrials.gov under registration no. NCT01424540.)

Cerebrospinal fluid (CSF) concentrations are used as a surrogate measure of central nervous system (CNS) availability of drugs. Systemically administered drugs can reach CSF either directly via passage across the choroid plexus, or indirectly by passage across the blood-brain barrier (BBB) followed by diffusion/convection transport from the interstitial fluid (ISF) to CSF. This review focuses on the physiological and pharmacokinetic variables that must be considered in the interpretation of the CSF-to-plasma concentration gradient. A survey of the literature suggests that the equilibrated CSF-to-unbound plasma concentration ratio reflects the balance between drug permeability across the blood-CNS barriers and the sink action of CSF turnover. As lipophilicity and membrane permeability increase, the CSF-to-plasma unbound concentration ratio rises from well below 1 toward unity. Deviations are noted in that lipophilic drugs highly bound to CSF proteins had ratio exceeding unity, and lipophilic drugs that were efflux transporter substrates exhibited ratios well less than unity. Drug concentration gradients have been observed between drug in the ISF and CSF, the direction of which depends on the CSF sink action and drug permeability/transport across the BBB and choroid plexus. Despite the complexity of CSF pharmacokinetics, for some drugs a rapid kinetic equilibrium exists between the CSF and biophase, such that CSF concentration can serve as a proximate reference for detailed investigation of factors affecting the intrinsic pharmacodynamics of a centrally acting drug. The applicability and limitations of CSF sampling for assessing the CNS availability and concentration-effect relationship of drug candidates with varying physicochemical properties during drug discovery and development is discussed.

The purpose of this study was to measure the in vivo brain distribution of antihistamines and assess the influence of in vitro permeability, P-glycoprotein (Pgp) efflux, and plasma protein binding. Six antihistamines (acrivastine, chlorpheniramine, diphenhydramine doxylamine, fexofenadine, terfenadine) were selected based on previously reported in vitro permeability and Pgp efflux properties and dosed intravenously to steady-state plasma concentrations of 2–10 µmol/l in rats. Plasma and brain concentrations were measured by LC/MS/MS, and protein binding determined by ultrafiltration. Doxylamine, diphenhydramine and chlorpheniramine had brain-to-plasma concentration ratios of 4.34 ± 1.26, 18.4 ± 2.35 and 34.0 ± 9.02, respectively. These drugs had high passive membrane permeability (>310 nm/s), moderate protein binding (71–84%) and were not Pgp substrates; features that yield high CNS penetration. In contrast, acrivastine and fexofenadine had low brain-to-plasma ratios of 0.072 ± 0.014 and 0.018 + 0.002, consistent with low passive membrane permeability for both compounds (16.2 and 66 nm/s, respectively) and Pgp efflux. Finally, terfenadine had a brain-to-plasma ratio of 2.21 ± 1.00 even though it underwent Pgp-mediated efflux (in vitro ratio = 2.88). Terfenadine’s high passive permeability (285 nm/s) overcame the Pgp-mediated efflux to yield brain-to-plasma ratio >1. The brain-to-unbound plasma ratio was 22-fold higher suggesting that protein binding (96.3% bound) limited terfenadine’s brain distribution. In conclusion, passive membrane permeability, Pgp-mediated efflux and/or high plasma protein binding influence the in vivo brain distribution of antihistamine drugs.

JNJ-56914845 (GSK2336805) is a hepatitis C virus nonstructural protein 5A inhibitor under development for the treatment of chronic hepatitis C (CHC) infection. This open-label, parallel-group, 2-part study evaluated the pharmacokinetics and safety of a single oral 60 mg dose of JNJ-56914845 in 4 cohorts: healthy, mild, moderate, and severe hepatic impairment (n = 8/cohort). Severity of hepatic impairment was categorized using Child-Pugh score, and the healthy subjects were matched for age, sex, body mass index, and smoking status to the moderate hepatic impairment cohort. JNJ-56914845 plasma AUC0-∞ was 26%, 52%, and 45% lower in subjects with mild, moderate, and severe hepatic impairment, respectively, relative to healthy subjects with no difference in half-life among the groups. The apparent oral clearance and volume of distribution were higher in subjects with hepatic impairment. The lower plasma concentrations were largely explained by decreased plasma protein binding in hepatically impaired subjects. One subject with severe hepatic impairment had 2 non-drug-related serious adverse events: an esophageal bleed requiring hospitalization, encephalopathy. Although hepatically impaired subjects have lower exposures than healthy matched controls, they had similar or slightly higher exposures than those observed in past studies of noncirrhotic, CHC patients, suggesting that no dose adjustments for hepatic impairment will be needed.

Membrane permeability and P-glycoprotein (Pgp) can be limiting factors for blood-brain barrier penetration. The objectives of this study were to determine whether there are differences in the in vitro permeability, Pgp substrate profiles, and physicochemical properties of drugs for central nervous system (CNS) and non-CNS indications, and whether these differences are useful criteria in selecting compounds for drug development. Apparent permeability (P(app)) and Pgp substrate profiles for 93 CNS (n = 48) and non-CNS (n = 45) drugs were determined by monolayer efflux. Calcein-AM inhibition assays were used to supplement the efflux results. The CNS set (2 of 48, 4.2%) had a 7-fold lower incidence of passive permeability values150 nm/s compared with the non-CNS set (13 of 45, 28.9%). The majority of drugs (72.0%, 67 of 93) were not Pgp substrates; however, 49.5% (46 of 93) were positive in the calcein-AM assay when tested at 100 microM. The CNS drug set (n = 7 of 48, 14.6%) had a 3-fold lower incidence of Pgp-mediated efflux than the non-CNS drug set (n = 19 of 45, 42.2%). Analysis of 18 physicochemical properties revealed that the CNS drug set had fewer hydrogen bond donors, fewer positive charges, greater lipophilicity, lower polar surface area, and reduced flexibility compared with the non-CNS group (p0.05), properties that enhance membrane permeability. This study on a large, diverse set of marketed compounds clearly demonstrates that permeability, Pgp-mediated efflux, and certain physicochemical properties are factors that differentiate CNS and non-CNS drugs. For CNS delivery, a drug should ideally have an in vitro passive permeability150 nm/s and not be a good (B --A/A --B ratio2.5) Pgp substrate.

The purpose of this work was (1) to determine if useful in vivo pharmacokinetic data could be obtained after simultaneous administration of 5-22 compounds of a chemically congeneric series to dogs and (2) to determine if structure-pharmacokinetic relationships could be derived from such studies. Mixtures of structurally related alpha-1 antagonist compounds (5-22) were administered intravenously to conscious dogs. Blood samples were taken over the next 24 h and analyzed by LC/MS to determine plasma levels and pharmacokinetics of each compound. The pharmacokinetics of 17 of these compounds were also determined after individual administration. Results obtained in the N-in-One format for 17 compounds correlated well with results obtained when these same compounds were administered individually. The N-in-One method is a useful method for obtaining pharmacokinetic data on 5-20 molecules in a single animal at one time. The increased throughput in obtaining important pharmacokinetic information should enhance the drug discovery process. In addition, it was possible to determine the extent to which various chemical substitutions did or did not affect pharmacokinetic parameters.

Cassette dosing, combining many test chemicals into one dose solution, is an attractive method for increasing the throughput of in vivo pharmacokinetic experiments. This dosing technique depends on the sensitivity and selectivity of modern analytical techniques, particularly HPLC/MS/MS. Cassettes vary in size, but even relatively small ones greatly increase the numbers of compounds investigated by reducing the effort devoted to animal handling, sample processing and sample analysis. The major drawback of cassette dosing is the potential for drug-drug interactions.

Background & Aims GSK2336805 is a HCV NS5A inhibitor for chronic hepatitis C (CHC). In a prior Phase I study, GSK2336805 was well tolerated and had an antiviral and pharmacokinetic profile suitable for once-daily administration. This 28-day, double-blind, randomized, placebo-controlled study evaluated once daily GSK2336805 60 mg alone or in combination with peginterferon alfa-2a (180 μg per week) and ribavirin (1000–1200 mg daily) (PEG/RIBA) in treatment-naive genotype 1 CHC subjects. Methods Five centres enrolled 16 subjects in the USA and Puerto Rico who received GSK2336805 + PEG/RIBA or placebo + PEG/RIBA. Results Following a single monotherapy dose of GSK2336805 on day 1, median reduction from baseline in HCV RNA was −2.96 log10 (N = 11) vs. −0.13 log10 (N = 4) for placebo. With the addition of PEG/RIBA on day 2, subjects receiving GSK2336805 exhibited greater decreases in viral load over the 28-day treatment period as compared with placebo. At day 28, median reduction from baseline was −4.86 log10 (N = 9) in the GSK2336805 + PEG/RIBA group as compared with −1.98 log10 (N = 4) in the placebo + PEG/RIBA group. At day 28, rapid virological response (RVR) occurred in 8/11 (73%) of the GSK2336805 + PEG/RIBA subjects as compared with 1/4 (25%) of the placebo + PEG/RIBA subjects. Adverse events were consistent with those reported in clinical trials of peginterferon and ribavirin, and no unique adverse events appeared to be associated with GSK2336805. Conclusions GSK2336805 is a potent NS5A inhibitor that showed a substantial antiviral effect as a monotherapy and in combination with peginterferon and ribavirin. ClinicalTrials.gov Identifier: NCT01439373.

This Phase I, randomized, open-label study evaluated the gastric pH-altering effects of omeprazole, a proton pump inhibitor, and the CYP3A enzyme/P-glycoprotein (Pgp)-inhibitory effects of ritonavir, an HIV protease inhibitor, on the pharmacokinetics and safety of the hepatitis C virus (HCV) non-structural protein 5A (NS5A) inhibitor GSK2336805 in healthy male and female subjects. Co-administration of GSK2336805 60 mg with omeprazole decreased GSK2336805 plasma AUC(0-∞) by 10% and Cmax by 18%; no marked effect was observed on t½ . Co-administration of GSK2336805 30 mg with ritonavir increased GSK2336805 plasma AUC(0-∞) by 52%, Cmax by 43%, and t½ by 40%; CL/F was decreased by 34%. All adverse events were minor in intensity. The gastric acid-suppressive effect of omeprazole had minimal impact on the extent and rate of GSK2336805 absorption in vivo; therefore, GSK2336805 may be co-administered with omeprazole without concern about lower GSK2336805 exposures and compromised antiviral efficacy. The modest increases in AUC and Cmax following co-administration of GSK2336805 plus ritonavir suggest that GSK2336805 when given concomitantly with a single CYP3A/Pgp inhibiting drug will not likely require dose adjustment. Final dose recommendation will be based on GSK2336805 efficacy and safety profiles from Phase III trials in HCV-infected patients.

The objective of this study was to evaluate the performance of the Wajima allometry (Css -MRT) approach published in the literature, which is used to predict the human plasma concentration-time profiles from a scaling of preclinical species data. A diverse and blinded dataset of 108 compounds from PhRMA member companies was used in this evaluation. The human intravenous (i.v.) and oral (p.o.) pharmacokinetics (PK) data were available for 18 and 107 drugs, respectively. Three different scenarios were adopted for prediction of human PK profiles. In the first scenario, human clearance (CL) and steady-state volume of distribution (Vss ) were predicted by unbound fraction corrected intercept method (FCIM) and Oie-Tozer (OT) approaches, respectively. Quantitative structure activity relationship (QSAR)-based approaches (TSrat-dog ) based on compound descriptors together with rat and dog data were utilized in the second scenario. Finally, in the third scenario, CL and Vss were predicted using the FCIM and Jansson approaches, respectively. For the prediction of oral pharmacokinetics, the human bioavailability and absorption rate constant were assumed as the average of preclinical species. Various statistical techniques were used for assessing the accuracy of the simulation scenarios. The human CL and Vss were predicted within a threefold error range for about 75% of the i.v. drugs. However, the accuracy in predicting key p.o. PK parameters appeared to be lower with only 58% of simulations falling within threefold of observed parameters. The overall ability of the Css -MRT approach to predict the curve shape of the profile was in general poor and ranged between low to medium level of confidence for most of the predictions based on the selected criteria.

This study is part of the Pharmaceutical Research and Manufacturers of America (PhRMA) initiative on predictive models of efficacy, safety, and compound properties. The overall goal of this part was to assess the predictability of human pharmacokinetics (PK) from preclinical data and to provide comparisons of available prediction methods from the literature, as appropriate, using a representative blinded dataset of drug candidates. The key objectives were to (i) appropriately assemble and blind a diverse dataset of in vitro, preclinical in vivo, and clinical data for multiple drug candidates, (ii) evaluate the dataset with empirical and physiological methodologies from the literature used to predict human PK properties and plasma concentration–time profiles, (iii) compare the predicted properties with the observed clinical data to assess the prediction accuracy using routine statistical techniques and to evaluate prediction method(s) based on the degree of accuracy of each prediction method, and (iv) compile and summarize results for publication. Another objective was to provide a mechanistic understanding as to why one methodology provided better predictions than another, after analyzing the poor predictions. A total of 108 clinical lead compounds were collected from 12 PhRMA member companies. This dataset contains intravenous (n = 19) and oral pharmacokinetic data (n = 107) in humans as well as the corresponding preclinical in vitro, in vivo, and physicochemical data. All data were blinded to protect the anonymity of both the data and the company submitting the data. This manuscript, which is the first of a series of manuscripts, summarizes the PhRMA initiative and the 108 compound dataset. More details on the predictability of each method are reported in companion manuscripts. © 2011 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4050–4073, 2011

The objective of this study was to evaluate the performance of various allometric and in vitro-in vivo extrapolation (IVIVE) methodologies with and without plasma protein binding corrections for the prediction of human intravenous (i.v.) clearance (CL). The objective was also to evaluate the IVIVE prediction methods with animal data. Methodologies were selected from the literature. Pharmaceutical Research and Manufacturers of America member companies contributed blinded datasets from preclinical and clinical studies for 108 compounds, among which 19 drugs had i.v. clinical pharmacokinetics data and were used in the analysis. In vivo and in vitro preclinical data were used to predict CL by 29 different methods. For many compounds, in vivo data from only two species (generally rat and dog) were available and/or the required in vitro data were missing, which meant some methods could not be properly evaluated. In addition, 66 methods of predicting oral (p.o.) area under the curve (AUCp.o. ) were evaluated for 107 compounds using rational combinations of i.v. CL and bioavailability (F), and direct scaling of observed p.o. CL from preclinical species. Various statistical and outlier techniques were employed to assess the predictability of each method. Across methods, the maximum success rate in predicting human CL for the 19 drugs was 100%, 94%, and 78% of the compounds with predictions falling within 10-fold, threefold, and twofold error, respectively, of the observed CL. In general, in vivo methods performed slightly better than IVIVE methods (at least in terms of measures of correlation and global concordance), with the fu intercept method and two-species-based allometry (rat-dog) being the best performing methods. IVIVE methods using microsomes (incorporating both plasma and microsomal binding) and hepatocytes (not incorporating binding) resulted in 75% and 78%, respectively, of the predictions falling within twofold error. IVIVE methods using other combinations of binding assumptions were much less accurate. The results for prediction of AUCp.o. were consistent with i.v. CL. However, the greatest challenge to successful prediction of human p.o. CL is the estimate of F in human. Overall, the results of this initiative confirmed predictive performance of common methodologies used to predict human CL.

The objective of this study was to evaluate the performance of various empirical, semimechanistic and mechanistic methodologies with and without protein binding corrections for the prediction of human volume of distribution at steady state (Vss ). PhRMA member companies contributed a set of blinded data from preclinical and clinical studies, and 18 drugs with intravenous clinical pharmacokinetics (PK) data were available for the analysis. In vivo and in vitro preclinical data were used to predict Vss by 24 different methods. Various statistical and outlier techniques were employed to assess the predictability of each method. There was not simply one method that predicts Vss accurately for all compounds. Across methods, the maximum success rate in predicting human Vss was 100%, 94%, and 78% of the compounds with predictions falling within tenfold, threefold, and twofold error, respectively, of the observed Vss . Generally, the methods that made use of in vivo preclinical data were more predictive than those methods that relied solely on in vitro data. However, for many compounds, in vivo data from only two species (generally rat and dog) were available and/or the required in vitro data were missing, which meant some methods could not be properly evaluated. It is recommended to initially use the in vitro tissue composition-based equations to predict Vss in preclinical species and humans, putting the assumptions and compound properties into context. As in vivo data become available, these predictions should be reassessed and rationalized to indicate the level of confidence (uncertainty) in the human Vss prediction. The top three methods that perform strongly at integrating in vivo data in this way were the Oie-Tozer, the rat -dog-human proportionality equation, and the lumped-PBPK approach. Overall, the scientific benefit of this study was to obtain greater characterization of predictions of human Vss from several methods available in the literature.

Background No data on once-daily dosing of nucleoside analogues in African children currently exist. We compared the pharmacokinetics (PK) of once- versus twice-daily lamivudine and abacavir treatment using the World Health Organization recommended weight band dosing of scored adult tablets. Methods HIV type-1 (HIV-1)-infected Ugandan children aged 3–12 years receiving antiretroviral therapy that included lamivudine and abacavir twice daily (total 150+300 mg, 225+450 mg and 225/300+600 mg daily for 12–0–24) and maximum concentrations (Cmax) were compared by geometric mean ratios (GMRs). Results A total of 41 HIV-1-infected children (median age of 7 years) and n=23, n=14 and n=4 in 12–0–24 was 13.0 and 12.0 mg•h/l for once- and twice-daily lamivudine (GMR 1.09, 90% confidence intervals [CI] 0.98–1.20) and 15.3 and 15.6 mg•h/l for once- and twice-daily abacavir (GMR 0.98, 90% CI 0.89–1.08), respectively, with no difference in 3–6 versus 7–12 year olds. Cmax was 76% (lamivudine) and 64% (abacavir) higher on once-daily regimens. For both children and caregivers, once-daily dosing of lamivudine plus abacavir was highly acceptable and strongly preferred over twice-daily. Conclusions In children aged 3–12 years, AUC0–24 of lamivudine and abacavir were bioequivalent on once-and twice-daily regimens. Once-daily dosing of abacavir and lamivudine could provide an alternative dosing strategy for HIV-1-infected children, with high acceptability and strong preference suggesting the potential for improved adherence.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • An increasing number of drugs on the market or under development have been identified as substrates of the ATP-binding cassette drug efflux transporter breast cancer resistance protein (BCRP; ABCG2), which can affect the pharmacokinetics of drugs by reducing absorption and/or increasing biliary elimination. • ABCG2 C421A, a single nucleotide polymorphism associated with decreased protein expression/transport activity in vitro and higher anti-cancer drug concentrations in carriers of the C421A polymorphism, may contribute to the intersubject pharmacokinetic variability of BCRP substrates. • Predicting the potential influence of BCRP on drug disposition or drug interactions is challenging because of the lack of a well-characterized, BCRP-selective clinical probe substrate. • Nitrofurantoin is potentially a suitable clinical BCRP probe substrate based on preclinical and clinical information available (e.g. in vitro transport studies, Bcrp knockout mouse studies, inhibition studies in rats, and milk secretion studies in rats and humans). WHAT THIS STUDY ADDS • The ABCG2 C421A SNP had no effect on oral nitrofurantoin plasma and urine pharmacokinetic parameters in healthy male Chinese subjects. • Nitrofurantoin does not appear to be a useful clinical BCRP probe. AIMS A number of drugs are substrates or inhibitors of the efflux transporter breast cancer resistance protein (BCRP; ABCG2), which can limit systemic exposure by reducing absorption and/or increasing biliary elimination. The identification of a BCRP-selective clinical probe drug would provide a useful tool to understand the effect of genetic polymorphisms and transporter-based drug interactions on drug pharmacokinetics. The aim of this study was to assess the utility of nitrofurantoin as a clinical probe substrate for BCRP activity by evaluating the impact of genetic variation on nitrofurantoin pharmacokinetics. METHODS Nitrofurantoin pharmacokinetics were studied in an open-label, single-oral dose (100 mg) study in 36 male Chinese subjects who were pre-screened for ABCG2 421 CC, CA and AA genotypes (n = 12 each). Plasma and urine concentrations of nitrofurantoin were determined by LC/MS/MS and LC/UV respectively. anova was used to compare pharmacokinetic parameters among genotypes. RESULTS There were no significant differences in nitrofurantoin pharmacokinetics among the genotypic cohorts. The geometric mean nitrofurantoin plasma AUC(0-∞) (95% confidence interval) values were 2.21 (2.00, 2.45), 2.42 (2.11, 2.78) and 2.32 (1.99, 2.70) µg h ml−1 and half-life values were 0.79 (0.59, 1.0), 0.76 (0.64, 0.89) and 0.72 (0.62, 0.84) h for ABCG2 421 genotypes CC, CA and AA, respectively. The percentage of dose excreted unchanged in the urine was 43, 44 and 39%, respectively. CONCLUSIONS The ABCG2 C421A polymorphism had no effect on nitrofurantoin plasma and urine pharmacokinetic parameters in healthy Chinese subjects. These results indicate that nitrofurantoin is not a suitable clinical probe substrate for assessing BCRP activity.

The design, synthesis, and SAR of a novel series of heterobiaryl phenethanolamine beta3 adrenergic receptor agonists are described. The furan analogue 49 was shown to elicit a significant dose-dependent lowering of plasma glucose in a rodent model of type 2 diabetes.

Objective: 873140 is a spirodiketopiperazine CCR5 antagonist with prolonged receptor binding and potent antiviral activity in vitro. This study evaluated plasma HIV RNA, safety, and pharmacokinetics following short-term monotherapy in HIV-infected adults. Design: Double-blind, randomized, placebo-controlled multi-center trial. Methods: Treatment-naive or experienced HIV-infected subjects with R5-tropic virus, CD4 cell count nadir > 200 × 106 cells/l, viral load > 5000 copies/ml and not receiving antiretroviral therapy for the preceding 12 weeks were enrolled. Forty subjects were randomized to one of four cohorts (200 mg QD, 200 mg BID, 400 mg QD, 600 mg BID) with 10 subjects (eight active, two placebo) in each cohort, and received treatment for 10 days. Serial HIV RNA, pharmacokinetics, and safety evaluations were performed through day 24. Results: Of the 40 subjects, 21 were treatment-experienced; 35 were male, 20 were non-white, and eight were coinfected with hepatitis C virus. Median baseline HIV RNA ranged from 4.26log10 to 4.46 log10. 873140 was generally well tolerated with no drug-related discontinuations. The most common adverse events were grade 1 gastrointestinal complaints that generally resolved within 1–3 days on therapy. No clinically significant abnormalities were observed on electrocardiogram or in laboratory parameters. Mean log changes in HIV RNA at nadir, and the percentage of subjects with > 1 log10 decrease were −0.12 (0%) for placebo, −0.46 (17%) for 200 mg once daily, −1.23 (75%) for 200 mg twice daily, −1.03 (63%) for 400 mg once daily, and −1.66 (100%) for 600 mg twice daily. An Emax relationship was observed between the area under the 873140 plasma concentration–time curve and change in HIV RNA. Conclusions: 873140 demonstrated potent antiretroviral activity and was well tolerated. These results support further evaluation in Phase 2b/3 studies.