This was a phase I, single-site, open-label, fixed-sequence, crossover study with three treatment periods to evaluate the effect of an oral tablet of PTN on the steady-state PK of orally administrated RIF in 18 healthy subjects. The study was conducted in accordance with the principles of the Declaration of Helsinki. A written informed consent was obtained from every subject. The study protocol was reviewed and approved by an independent Medical Ethics Committee.
All participants received a single 400 mg dose of PTN in the morning on days 1 and 13(Fig. 1). Subjects received RIF 600 mg once daily on days 6-16. PTN 400 mg once daily was co-administrated with RIF 600 mg once daily on day 13. RIF was administrated on an empty stomach, then subjects had a standard meal one hour after RIF administration. PTN were administrated orally in the morning 30 min after the start of the standard meal.
Serial blood samples for determining the plasma concentration of PTN were collected on days 1 and 13 at the following times: pre-dose, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 8 h, 10 h, 12 h, 24 h, 48 h, 72 h, 96 h post-dose.
All blood samples were collected into evacuated heparin lithium anticoagulant tubes. Plasma was separated by centrifugation at around 2500 × g for 10 min at 25±5℃, and the blood sample could be placed at room temperature no longer than one hour. The separated plasma sample should be transferred to -70℃(-60℃~-90℃)freezer, where it was stored until it was shipped for analysis.
Each subject was evaluated with physical examination, medical history, and laboratory testing at a screening visit conducted within 14 days prior to the first dose of drug. Eligible subjects were 18 to 45 years of age, had a minimum weight requirement of 45 kg for women and 50 kg for men, and a body mass index requirement between 19 and 24 kg/m2. Key exclusion criteria included history or presence of clinically significant medical, psychiatric disorder; concomitant chronic or acute illness; history or presence of drug addiction or excessive use of alcohol or tobacco; previous drug allergy. Participants whose QT interval longer than 470 msec corrected by Fridericia on 12-lead electrocardiogram were also excluded from the study. Participants were also excluded from the study if they had taken any drug in the past 14 days or any drugs that alter the activity of liver enzyme in the past 28 days. Subjects were required to have negative screening results for HIV-1, hepatitis B, hepatitis C, and syphilis. Concomitant medication was not permitted during the study except for dealing with adverse events or treating emergencies.
Safety evaluations included the monitoring of adverse events (AEs), physical examinations, clinical chemistry laboratory tests, vital signs, and electrocardiograms. Treatment-emergent adverse events (TEAEs) were recorded throughout the study.
Plasma samples were analyzed for PTN by a validated high-performance liquid chromatography tandem mass spectrometry analysis. The LLOQ (lower limit of quantification) for PTN in plasma was 1.00 ng/mL, and the upper limit of quantification was 500 ng/mL. Precision and accuracy were evaluated by replicate analyses of human plasma quality control samples prepared at five concentrations: 1.00, 3.00, 25.0, 400, and 500 ng/mL. Precision, measured as the percent coefficient of variation, the maximum of which is 5.9% across the quality control range. Accuracy, expressed as the percent difference from the mean value, ranged from -2.3 to 5.7%. Both were within acceptance standards of 15%, except that 20% for LLOQ.
A non-compartmental PK analysis of the PTN concentration-time data was conducted. PK analyses of plasma PTN concentration-time data were analyzed by Phoenix WinNonlin 8.1. Plasma PK parameters for PTN were calculated using actual elapsed times from dosing. The individual PK parameters that were determined included maximum observed plasma concentration (Cmax), time to Cmax (Tmax), area under the curve from time zero to the last quantifiable concentration (AUC0−t), area under the curve from time zero to the infinite concentration (AUC0−∞), elimination half-life (t1/2), apparent volume of distribution (VZ/F), apparent clearance(CL/F).
This study was designed to estimate the magnitude of drug-interaction effect of RIF on the PK parameters of PTN. PK parameters were log-transformed and analyzed by analysis of variance to determine the point estimate and associated 90% confidence intervals for the difference between test treatment (PTN + RIF) and reference treatment (RIF alone). These values were then back-transformed to calculate the point and interval estimates for test-to-reference treatment ratios on the original scale. Geometric least-squares mean ratios and 90% confidence intervals were generated by the mixed-effect model for within-subject treatment comparisons.