Determination of the HCV Protease Inhibitor Telaprevir in Plasma and Dried Blood Spot by Liquid Chromatography-Tandem Mass Spectrometry.

BACKGROUND: Telaprevir is a protease inhibitor used in the treatment of hepatitis C virus infection. Analytical methods for telaprevir should separate the compound from its R-diastereomer VRT-127394, which is 30-fold less active. The objective of this work was to develop liquid chromatography-tandem mass spectrometer (LC-MS/MS) assays for telaprevir both in plasma and in dried blood spot (DBS), capable of stabilizing the equilibrium and chromatographically separating the 2 epimers. METHODS: Human plasma was acidified with formic acid and frozen within 1 hour after collection to stabilize the equilibrium between the 2 telaprevir diastereomers ex vivo in plasma. After protein precipitation, the sample was analyzed with LC-MS/MS. For the DBS assay, sampling paper was impregnated with citric acid solution to achieve stabilization of the epimers on the sampling paper. DBS samples were extracted before LC-MS/MS analysis. LC-MS/MS analysis comprised online solid-phase extraction and separation on a C18 column, with the mass spectrometer operating in TurboIonSpray-negative ionization mode and performing multiple reaction monitoring. RESULTS: The assays were linear over the concentration range of 0.1-10 mg/L in plasma and DBS. Accuracies ranged from 97% to 106% in plasma and from 93% to 99% in DBS. Within- and between-day coefficients of variation were <7.9% in plasma and <9.3% in DBS. Human whole blood samples with hematocrit values of 27%-47% gave reproducible quantitation results in the DBS assay, and spot volume did not affect results of the DBS assay either. Acidified plasma with telaprevir was stable for 5 hours at 20°C, and telaprevir on impregnated DBS paper was stable for at least 3 months at 4°C or at 20°C. CONCLUSIONS: An assay was developed and validated for the determination of telaprevir in human plasma, separating telaprevir from its R-diastereomer VRT-127394. In addition, a DBS assay was developed, which avoids immediate centrifuging, acidification, and freezing of patient samples to stabilize the equilibrium between the 2 telaprevir diastereomers.

Lack of a clinically significant drug-drug interaction in healthy volunteers between the HCV protease inhibitor boceprevir and the proton pump inhibitor omeprazole.

OBJECTIVES: Proton pump inhibitors (PPIs) can limit the solubility of concomitant drugs, which can lead to decreased absorption and exposure. Reduced efficacy can be a consequence and in the case of an antimicrobial agent this may contribute to development of resistance. Patients chronically infected with the hepatitis C virus can be treated with a boceprevir-containing regimen and it is relevant to know if interactions between PPIs and boceprevir exist. This study was designed to investigate the influence of a frequently used PPI, omeprazole, on the pharmacokinetics of boceprevir and vice versa. METHODS: In this open-label, three-period, randomized, cross-over, Phase I study, healthy subjects were randomly assigned to 40 mg of omeprazole once daily for 5 days, 800 mg of boceprevir three times daily for 5 days and 40 mg of omeprazole once daily + 800 mg of boceprevir three times daily for 5 days, or the same treatment in a different order. Every treatment was followed by a wash-out period. At day 5 of every treatment pharmacokinetic blood sampling was performed for 8 h after medication intake. ClinicalTrials.gov: NCT01470690. RESULTS: All 24 subjects (15 males) completed the study and no serious adverse events were reported. Geometric mean ratios (90% CI) of the area under the plasma concentration-time curve up to 8 h (AUC0-8) and maximum plasma concentration (Cmax) of boceprevir with omeprazole versus boceprevir alone were 0.92 (0.87-0.97) and 0.94 (0.86-1.02), respectively. For omeprazole these values were 1.06 (0.90-1.25) for AUC0-8 and 1.03 (0.85-1.26) for Cmax for the combination versus omeprazole alone. CONCLUSIONS: Omeprazole did not have a clinically significant effect on boceprevir exposure, and boceprevir did not affect omeprazole exposure.

Drug-drug interactions between raltegravir and pravastatin in healthy volunteers.

BACKGROUND: To evaluate the potential drug-drug interaction between raltegravir and pravastatin. METHODS: This was an open-label, randomized, 3-period, cross-over, single-centre trial in 24 healthy volunteers. Subjects received the following treatments: pravastatin 40 mg every day for 4 days, raltegravir 400 mg twice a day for 4 days, and pravastatin 40 mg every day + raltegravir 400 mg twice a day for 4 days. The treatments were separated by washout periods of 10 days. On day 4 of each treatment period, blood samples for pharmacokinetics were collected throughout a 24-hour period. RESULTS: Geometric mean ratios (90% confidence interval) for pravastatin + raltegravir versus pravastatin alone were 0.96 (0.83 to 1.11) for AUC0-24 and 1.04 (0.85 to 1.26) for Cmax. The mean low-density lipoprotein cholesterol decrease after 4 days of pravastatin was 0.42 mmol/L both in the presence and the absence of raltegravir. The geometric mean ratio (90% confidence interval) AUC0-12, Cmax, and C12 for raltegravir + pravastatin versus raltegravir alone were 1.13 (0.77 to 1.65), 1.31 (0.81 to 2.13), and 0.59 (0.39 to 0.88), respectively. CONCLUSIONS: Raltegravir did not influence the pharmacokinetics or the short-term lipid-lowering effects of pravastatin, whereas pravastatin increased the Cmax but decreased the C12 of raltegravir. The effects of pravastatin on raltegravir pharmacokinetics are not likely to be clinically relevant.

International interlaboratory quality control program for measurement of antiretroviral drugs in plasma.

An international interlaboratory quality control program for measurement of antiretroviral drugs was initiated. The first round was confined to protease inhibitors and showed large variability in the performance of participating laboratories. The results demonstrate the need for and utility of an ongoing quality control program in this area of bioanalysis.