Rational dose selection for a nonnucleoside reverse transcriptase inhibitor through use of population pharmacokinetic modeling and Monte Carlo simulation

In order to choose a rational dose for GW 420867X, we first set a goal of therapy. We hypothesized that, for optimal antiretroviral activity, the trough free drug concentration should remain above the 90% effective concentration (EC90) of human immunodeficiency virus type 1. We performed population pharmacokinetic analysis on three different doses of GW 420867X (50, 100, and 200 mg). Monte Carlo simulation was performed, assuming a log-normal distribution for 1,000 simulated subjects for each dose, and was repeated three times. The trough concentrations were divided by 76 to account for protein binding and for the difference between EC50 and EC90. We then determined the fraction of the simulated population whose free drug trough concentrations would exceed an EC90 over a broad range of values. The target attainment for all three doses exceeded 95% out to a starting EC50 of 10 nM. For 16 viral isolates, the EC50 range encountered for GW 420867X did not exceed 8 nM, implying that the three doses could not be differentiated by effect in a clinical trial in naive patients. This prediction was shown to be correct in a randomized, double-blind trial with 1 week of monotherapy with GW 420867X.     

No effect of a single supratherapeutic dose of lersivirine, a next-generation nonnucleoside reverse transcriptase inhibitor, on corrected QT interval in healthy subjects

The objective of this study was to investigate the effect of a supratherapeutic dose of lersivirine (LRV) on corrected QT (QTc) interval using Fridericia's equation (QTcF) in healthy subjects. In this randomized, single-dose, placebo- and active-controlled 3-way crossover study, healthy adult males (n = 48) were randomized to receive LRV (2,400 mg), moxifloxacin (400 mg), or placebo for each treatment period. Triplicate 12-lead electrocardiogram measurements were performed, PK samples were collected, and vital signs were measured. Adverse event monitoring and safety laboratory testing were performed. All subjects were white (mean age, 39 years; body mass index [BMI], 25.6 kg/m(2)) and completed the study. Following LRV administration, the upper bound of the 90% confidence interval (CI) for time-matched adjusted mean differences to placebo QTcF at each time point postdose was below the regulatory threshold of 10 ms, satisfying the criteria for a negative thorough QT/QTc study. The highest upper bound of QTcF 90% CI occurred at 6 h for LRV (3.32 ms; 90% CI, 1.47 to 5.17 ms). The study was deemed adequately sensitive as the lower bound of the 90% CI for the adjusted mean QTcF differences between moxifloxacin and placebo at the moxifloxacin historical T(max) of 3 h was >5 ms (15.29 ms; 90% CI, 13.44 to 17.14 ms). There was no statistically significant relationship between LRV exposure and placebo-adjusted change from baseline QTcF or clinically significant changes in QRS complex, pulse rate (PR) interval, heart rate, or blood pressure. LRV (2,400 mg) did not prolong the QTcF interval, and no clinically relevant electrocardiogram or vital sign changes were observed in healthy subjects.