Population pharmacokinetics of dolutegravir in HIV-infected treatment-naive patients.

AIM: Dolutegravir is the newest integrase inhibitor approved for HIV treatment and has demonstrated potent antiviral activity in patient populations with a broad range of treatment experience. This analysis aimed to characterize the population pharmacokinetics of dolutegravir in treatment-naive patients and to evaluate the influence of patient covariates. METHODS: A population pharmacokinetic model was developed using a non-linear mixed effect modelling approach based on data from 563 HIV-infected, treatment-naive adult patients in three phase 2/3 trials who received dolutegravir (ranging from 10-50 mg once daily) alone or in combination with abacavir/lamivudine or tenofovir/emtricitabine. RESULTS: The pharmacokinetics of dolutegravir were adequately described by a linear one compartment model with first order absorption, absorption lag time and first order elimination. Population estimates for apparent clearance, apparent volume of distribution, absorption rate constant and absorption lag time were 0.901 l h(-1) , 17.4 l, 2.24 h(-1) , and 0.263 h, respectively. Weight, smoking status, age and total bilirubin were predictors of clearance, weight was a predictor of volume of distribution and gender was a predictor of bioavailability. However, the magnitude of the effects of these covariates on steady-state dolutegravir plasma exposure was relatively small (<32%) and was not considered clinically significant. Race/ethnicity, HBV/HCV co-infection, CDC classification, albumin, creatinine clearance, alanine aminotransferase or aspartate aminotransferase did not influence the pharmacokinetics of dolutegravir in this analysis. CONCLUSIONS: A population model that adequately characterizes dolutegravir pharmacokinetics has been developed. No dolutegravir dose adjustment by patient covariates is necessary in HIV-infected treatment-naive patients.

Safety and efficacy of GSK2248761, a next-generation nonnucleoside reverse transcriptase inhibitor, in treatment-naive HIV-1-infected subjects.

GSK2248761 is a novel, once-daily (QD), next-generation nonnucleoside reverse transcriptase inhibitor (NNRTI) with activity against efavirenz-resistant strains. Two phase I/IIa, double-blind, randomized, placebo-controlled studies investigated the antiviral activity, safety, and pharmacokinetics (PK) of several doses of GSK2248761 monotherapy in treatment-naive HIV-infected subjects. In the initial study, 10 subjects (8 active and 2 placebo) per dose received sequentially descending GSK2248761 monotherapy regimens of 800, 400, 200, and 100 mg QD for 7 days. Because a dose-response relationship was not identified, a second study examined a lower, 30-mg QD dose in 8 subjects (6 active and 2 placebo). Adverse events, viral load (VL), PK, and reverse transcriptase mutations were assessed and combined for analysis. Treatment with GSK2248761 for 7 days was well tolerated with no serious adverse events or discontinuations. The mean VL reductions from baseline on day 8 were 0.97, 1.87, 1.84, 1.81, and 1.78 log(10) copies/ml for GSK2248761 doses of 30, 100, 200, 400, and 800 mg QD, respectively. GSK2248761 PK (maximum drug concentration in serum [C(max)], area under the plasma concentration-time curve from 0 h to the end of the dosing interval [AUC(0-τ)], and concentration at the end of the dosing interval [C(τ)]) increased proportionally over the dose range of 30 to 800 mg QD. The relationship between short-term VL change and GSK2248761 PK was best described by a maximum-effect (E(max)) model using C(τ) (E(max) = 2.0; 50% effective concentration [EC(50)] = 36.9 ng/ml). No NNRTI resistance mutations emerged during the study. GSK2248761 at 100 to 800 mg QD for 7 days was well tolerated, demonstrated potent antiviral activity in treatment-naive HIV-infected subjects, and had favorable PK and resistance profiles. GSK2248761 is no longer in clinical development.

Drug interaction profile for GSK2248761, a next generation non-nucleoside reverse transcriptase inhibitor.

AIM: To evaluate potential drug interactions with antiretroviral therapies or supportive therapies for use in conjunction with the once daily, next generation non-nucleoside reverse transcriptase inhibitor GSK2248761 in patients with HIV-1 infection. METHODS: A series of phase I drug interaction studies was conducted. RESULTS: GSK2248761 was shown to be a weak CYP3A4 and CYP2D6 inhibitor in a clinical study with a probe cocktail. Mean plasma concentration-time profiles for atazanavir, tenofovir disoproxil fumarate/emtricitabine (TDF/FTC), darunavir (DRV, administered with ritonavir [RTV]), and drospirenone/ethinylestradiol were similar following co-administration of GSK2248761. Plasma raltegravir AUC(0,τ) and C(max) increased by 18% with no change in Cτ when raltegravir was co-administered with GSK2248761. Lopinavir (LPV) plasma AUC(0,τ), C(max) and Cτ decreased by 23%, 14% and 40%, respectively, following administration of lopinavir/ritonavir with GSK2248761. Atorvastatin, rosuvastatin and simvastatin AUC(0,∞) and C(max) increased following co-administration with GSK2248761, with the largest changes observed for simvastatin (3.7-fold and 4.3-fold). Changes in maximum and extent of GSK2248761 exposure were marginal after co-administration with atazanavir, TDF/FTC and raltegravir compared with GSK2248761 administered alone. Co-administration of GSK2248761 with DRV/RTV and LPV/RTV increased plasma GSK2248761 exposures by 1.25- to ≤2-fold compared with GSK2248761 administered alone, and increases in GSK2248761 exposure were higher following single dose co-administration of DRV/RTV or LPV/RTV compared with multiple doses. There were few drug-related AEs, and no treatment-related trends in blood chemistry, haematology, urinalysis, vital signs or ECG findings. CONCLUSIONS: These studies indicate that GSK2248761 was safe and well tolerated in healthy adults treated in these studies at the doses and duration of therapy evaluated.

Pharmacokinetic properties of single-dose lamivudine/adefovir dipivoxil fixed-dose combination in healthy Chinese male volunteers.

BACKGROUND: Both lamivudine and adefovir dipivoxil are approved for the treatment of chronic hepatitis B (CHB) and have established safety profiles. A fixed-dose combination (FDC) formulation of lamivudine/adefovir dipivoxil for the treatment of CHB may provide dosing convenience and improve adherence. OBJECTIVE: This study compared the pharmacokinetic profiles of an FDC capsule containing lamivudine/adefovir dipivoxil 100/10 mg and conventional lamivudine 100-mg + adefovir dipivoxil 10-mg tablets to determine bioequivalence. METHODS: This randomized, open-label, single-dose, 2-period crossover study was conducted in healthy male Chinese subjects. The study included a screening visit, 2 treatment sessions, and a follow-up visit. Subjects who met the inclusion/exclusion criteria were assigned to receive, in randomized order, 1 FDC capsule or 1 tablet each of lamivudine and adefovir dipivoxil. After a 7- to 10-day washout period, alternate treatment was given to the subjects during the second treatment session. Blood samples were collected immediately before and after dosing for 48 hours for plasma drug concentration measurement. Data on adverse events (AEs) were collected from the start of dosing until the follow-up visit. Tolerability assessments included physical examinations with vital sign measurements and clinical laboratory evaluations throughout the study. RESULTS: Forty subjects were enrolled into the study (mean age, 22.4 years [range, 19-28 years]; weight, 63.8 kg [range, 54-78 kg]). The pharmacokinetic profiles of lamivudine and adefovir were similar between the FDC and reference formulations. The geometric mean ratios (GMRs) for lamivudine C(max) and AUC(0-last) were 1.02 (90% CI, 0.92-1.12) and 0.99 (90% CI, 0.95-1.04), respectively; adefovir, 0.94 (90% CI, 0.89-0.99) and 0.95 (90% CI, 0.91-1.00). A limited number of mild AEs were reported, with no clinically significant changes in vital signs or laboratory results. CONCLUSIONS: The FDC capsule was bioequivalent to the concurrent administration of lamivudine + adefovir dipivoxil tablets based on the 90% CIs of the GMRs for C(max), AUC(0-∞), AUC(0-last), and t12 (all were between 0.80 and 1.25). Both treatments were well-tolerated.