Study design and subjects
This was an open-label, 3-period, crossover study conducted at a single-center in healthy adult subjects. The study protocol, amendments, and consent forms were reviewed and approved prior to study initiation by the study site’s institutional review board (Quintiles Early Clinical Development, Overland Park, KS, USA), and all subjects provided their written consent prior to initiation of any study-specific procedures. The study was conducted in a manner consistent with good clinical practices and local regulatory requirements and in accordance with the ethical standards of the Declaration of Helsinki and its amendments,
Adult men and women ranging from 18 to 65 years of age with a body mass index ranging from 18.5 to 31.0 kg/m2 (inclusive) and no clinically significant abnormalities on the basis of physical examination, laboratory testing, 12-lead electrocardiogram, and medical history were eligible for study inclusion. Eligible female subjects had negative results on human chorionic gonadotropin pregnancy tests. Male or female subjects who were not surgically sterile/postmenopausal agreed to use nonhormonal contraceptive methods, including abstinence, an intrauterine device, or 2 forms of barrier contraception. Excluded subjects were those with a preexisting condition that interfered with normal gastrointestinal motility or anatomy; as well as subjects with hepatic dysfunction or renal dysfunction, or both that could have interfered with the study drugs’ absorption, metabolism, or excretion. Subjects were excluded if they had an average weekly alcoholic beverage intake of more than 14 drinks for males or more than 7 drinks for females within 6 months of the study start. Exclusion criteria also included the regular use of tobacco- or nicotine-containing products within 6 months prior to screening; or a positive test for HCV antibody, hepatitis B surface antigen, or HIV antibody. Eligible subjects were prohibited from ingesting any prescription or nonprescription drugs, including herbal and dietary supplements and vitamins within 30 days, 5 half-lives, or twice the duration of the biological effect of the investigational product, whichever was longer, before the first dose of study medication.
Twelve healthy male or female subjects were enrolled to provide data from at least 10 evaluable subjects. The sample size of 12 to obtain 10 evaluable subjects was chosen based on an expected withdrawal rate of approximately 10 % and the within-subject variability of DTG. Within-subject variability of DCV, based upon historical data, is lower than that of DTG. Using a within-subject variability (CVw) of 30 % and a sample size of 10 evaluable subjects, it was estimated that the precision for the treatment comparison would be within 25.8 % of the point estimate for the concentration-time curve over the dosing interval (AUC[0-τ]), Cmax, and Cτ. If the point estimate of the ratio of geometric means was 1, then the 90 % confidence interval would be approximately 0.79 to 1.26. Subjects were randomized into 1 of 2 treatment sequences (n = 6 in each sequence) according to a randomization schedule. Study medications were DTG as a 50-mg tablet given once daily and DCV as a 60-mg tablet given once daily. Subjects in sequence 1 received DTG for 5 days in period 1 (treatment A), followed by DCV for 5 days in period 2 (treatment B), and finally DTG plus DCV for 5 days in period 3 (treatment C). Those in sequence 2 received DCV (treatment B) for 5 days in period 1, followed by DTG (treatment A) for 5 days in period 2, and then DTG plus DCV for 5 days in period 3 (treatment C). All doses of study drug were ingested under fasting conditions. Between period 1 and period 2, there was a washout period of at least 7 days. There was no washout period between period 2 and period 3. Day 1 of period 3 started the day after the last day in period 2. Periods 1, 2, and 3 were conducted on an inpatient setting. Within 7 to 14 days after the last dose of study drug was taken, a follow-up visit was conducted.
The safety evaluations performed during the study included clinical laboratory tests (hematology, serum chemistry, and urinalysis), vital sign monitoring, and physical examinations. Electrocardiograms were performed at screening. Throughout the entire treatment phase and at the follow-up evaluation, there was close monitoring for all adverse events (AEs).
Pharmacokinetic assessments
Blood samples were collected (2 mL per collection) at predose (within 15 min prior to dosing) and at 1, 2, 3, 4, 8, 12, and 24 h postdose on day 5 in period 1 or 2 and in period 3 for the determination of plasma concentrations of DTG. Blood samples were collected for the determination of plasma concentrations of DCV using the same sample collection schedule as was used in prior drug-drug interaction studies with DCV [
10], which was 4 mL per collection at predose (within 15 min prior to dosing) and at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 16, and 24 h postdose on day 5 in period 1 or 2 and in period 3. Blood samples were drawn into potassium ethylenediaminetetraacetic acid (K
2 EDTA)-containing tubes via venipuncture or through a cannula and were kept chilled on ice until centrifugation. Plasma was separated by centrifugation at 4 °C within 45 min of sample collection and stored at−20 °C or below until analysis.
Bioanalytical methods
Plasma samples were analyzed for DTG concentrations by PPD (Middleton, WI). All samples were received frozen on dry ice and in acceptable condition and stored frozen at−20 °C upon arrival. The DTG analysis was done using a validated analytical method based on protein precipitation using acetonitrile, which was followed by high-performance liquid chromatography with tandem mass spectrometry analysis using positive-ion electrospray, which was based on previously published methods [
11]. This assay was validated over the DTG concentration range of 20.0 to 20,000 ng/mL using a 25-μL aliquot of K
2 EDTA-treated plasma.
Plasma samples were analyzed for DCV concentrations by Tandem Labs (West Trenton, NJ, USA). Analysis was performed using a validated analytical method of solid phase extraction, followed by high-performance liquid chromatography with tandem mass spectrometry analysis, which was based on a previously published method [
12]. The lower and higher limits of quantification were 2.00 ng/mL and 2000 ng/mL, respectively, using a 100-μL aliquot of K
2 EDTA-treated plasma.
Quality control (QC) samples containing 3 different analyte concentrations of DTG and DCV were analyzed with each batch of samples against separately prepared calibration standards that were stored under the same conditions as study samples. Quality control results met acceptance criteria; ≤33 % of the quality control results were to deviate from the nominal concentration by >15 %, with ≥50 % of the quality control results acceptable at each concentration. The calibration standard coefficient of variance (CV) for DTG was ≤6.7 % with a difference from theoretical of ≤4.9 %, and the interassay CV per run was ≤5.8 % with a difference from theoretical of ≤3.2 %. The between-run CV for DCV was ≤2.2 %, and the within-run CV was ≤2.0 % with a mean deviation from nominal concentration of ±3.6 %.
Pharmacokinetic data analysis
Plasma DTG and DCV concentration-time data were analyzed by noncompartmental methods using Phoenix WinNonlin version 6.3 (Pharsight Corporation, St. Louis, MO). Pharmacokinetic parameter calculations were based on the actual sampling times recorded during the study. Pharmacokinetic parameters that were determined included maximum observed concentration (Cmax), concentration at the end of the dosing interval (Cτ), AUC0-τ, apparent clearance following oral dosing (CL/F), and terminal phase half-life (t1/2).
Statistical analysis
Statistical analysis was performed on the log-transformed plasma PK parameters. Point estimates and their associated 90 % confidence intervals (CIs) were constructed for the differences between test and reference treatments. Dolutegravir (treatment A) or DCV (treatment B), when given alone under fasted conditions, was considered to be the reference treatment. The test treatments were DTG coadministered with DCV (treatment C) under fasted conditions. The point estimates and their associated 90 % CIs were back-transformed to provide the ratios of geometric least-squares means and associated 90 % CIs for test/reference for the PK parameters AUC0-τ, Cτ, Cmax, CL/F, and t1/2. Dolutegravir and DCV PK were analyzed separately using SAS (SAS Institute, Inc, Cary, NC).