Pharmacokinetics and tolerability of paritaprevir, a direct acting antiviral agent for hepatitis C virus treatment, with and without ritonavir in healthy volunteers

Paritaprevir as a pan-antiviral against different flaviviruses

Introduction

The flavivirus infections caused by the Zika virus (ZIKV), Dengue virus (DENV), and West Nile virus (WNV) cause mild to serious pathological conditions, such as fever, joint pain, shock, internal bleeding, organ failure, nausea, breathlessness, brain tissue damage, neurodegenerative diseases, and deaths. As currently no efficient vaccine or drug is available to prevent or treat these diseases in humans, it is essential to identify potential drug-like molecules to treat these diseases. For these reasons, several known anti-viral drugs are repurposed against the proteases of ZIKV, WNV, and DENV to inhibit their activities.

Methods

The GOLD 5.0 molecular docking program was used to dock 20 HIV and HCV drugs against the ZIKV protease. Based on docking scores, 5 drugs were found to bind to the ZIKV protease with high affinities. Subsequently, the AMBER ff14SB force field was employed to simulate these drug-bound complexes of ZIKV protease. The MM/PBSA free energy method was utilized to compute the binding free energies of these complexes. Consequently, the two best ZIKV protease inhibitors were repurposed against the proteases of DENV and WNV.

Results and Discussion

It is found that out of the 5 drugs, Ritonavir and Paritaprevir bind to the NS2B-NS3 protease of the ZIKV strongly with the Gibbs binding free energies (∆Gbind) of -17.44±3.18 kcal/mol and -14.25±3.11 kcal/mol respectively. Remarkably, Ritonavir binds to the ZIKV Protease about 12 kcal/mol more strongly compared to its binding to the HIV protease. It is further found that Paritaprevir binds to DENV and WNV proteases as strongly as it binds to the ZIKV protease. Hence it is proposed that Paritaprevir may act as a potent pan-antiviral against the Zika, West Nile, and Dengue viral diseases.

In vitro demonstration of antedrug mechanism of a pharmacokinetic booster to improve CYP3A4 substrates by CYP3A4-mediated metabolism inhibition

We previously reported novel benzyl-ether derivatives with an imidazole ring and a hydroxyl group (A-01) or carboxyl group (B-01) and esters (2 esters of A-01, and 7 esters of B-01) as pharmacokinetics (PK) boosters. This study demonstrates how these ester compounds embody the concept of a safe pharmacokinetic booster, with potent and transient inhibition of CYP3A4-mediated drug metabolism. As a model CYP3A4 substrate and CYP3A4 enzyme, midazolam (MDZ) and rat liver microsomes were used. A-01 inhibited MDZ metabolism significantly, while B-01 induced only slight inhibition. Although rat liver microsomes hydrolyzed the ester compounds over time, several ester compounds strongly inhibited MDZ metabolism. Due to the significant activity of A-01, A-01 esters affected MDZ metabolism, irrespective of hydrolysis state. Time-dependent inhibition evaluation indicated that the B-01 ester inhibition is not mechanism-based, as hydrolysis eliminated MDZ metabolism inhibition. We report that the B-01 esters significantly inhibit CYP3A4-mediated drug metabolism, and upon hydrolysis this property is eliminated. In conclusion, B-01 ester compounds may be safe PK boosters with antedrug characteristics.

HCV Antiviral Drugs Have the Potential to Adversely Perturb the Fetal-Maternal Communication Axis through Inhibition of CYP3A7 DHEA-S Oxidation

The hepatitis C virus (HCV) poses a great risk to pregnant people and their developing fetus, yet no HCV antiviral treatment guidelines have been established. While there has been a substantial increase in the development of HCV antivirals, the effect they have on the developing fetus remains poorly defined. Many of these drugs are metabolized through the cytochrome P450 CYP3A pathway, which is mediated by cytochrome P450 3A7 (CYP3A7) in the fetus and developing infant. In this study, we sought to investigate the effect HCV antivirals have on CYP3A7 metabolism, as this CYP enzyme plays a vital role in proper fetal and neonatal development. Of the 13 HCV antivirals we investigated, 8 (∼62%) inhibited CYP3A7 metabolic activity by 50% or more at a concentration of 20 µM. Furthermore, paritaprevir, asunaprevir, simeprevir, danoprevir, and glecaprevir all had observed half-maximal inhibitory concentrations between the range of 10 and 20 µM, which is physiologically relevant in comparison with the Km of dehydroepiandrosterone-sulfate (DHEA-S) oxidation (reported to be between 5 and 20 µM). We also discovered that paritaprevir is a time-dependent inhibitor of CYP3A7, which shifts the IC50 ∼twofold from 11 µM to 5 µM. Upon further characterization, paritaprevir inactivates DHEA-S metabolism by CYP3A7, with KI and Kinact values of 4.66 µM and 0.00954 minute-1, respectively. Depending on treatment plan and off-label drug use, HCV treatment could adversely affect the fetal-maternal communication axis by blocking fetal CYP3A7 metabolism of important endogenous hormones. SIGNIFICANCE STATEMENT: The prevalence of HCV in pregnant people is estimated at between 1% and 8% of the global population, yet little to no information exists about the risk antiviral treatment poses to the developing fetus. There is a potential risk of drugs adversely affecting mother-fetal communication by inhibiting fetal hepatic CYP3A7, an integral enzyme for estriol production. We discovered that five HCV antivirals inhibited DHEA-S metabolism by CYP3A7, and paritaprevir inactivated the enzyme. Our studies demonstrate the potential threat these drugs pose to proper fetal development.

Main protease inhibitors and drug surface hotspots for the treatment of COVID-19: A drug repurposing and molecular docking approach

Here, drug repurposing and molecular docking were employed to screen approved MPP inhibitors and their derivatives to suggest a specific therapeutic agent for the treatment of COVID-19. The approved MPP inhibitors against HIV and HCV were prioritized, while RNA dependent RNA Polymerase (RdRp) inhibitor remdesivir including Favipiravir, alpha-ketoamide were studied as control groups. The target drug surface hotspot was also investigated through the molecular docking technique. Molecular dynamics was performed to determine the binding stability of docked complexes. Absorption, distribution, metabolism, and excretion analysis was conducted to understand the pharmacokinetics and drug-likeness of the screened MPP inhibitors. The results of the study revealed that Paritaprevir (-10.9 kcal/mol) and its analog (CID 131982844) (-16.3 kcal/mol) showed better binding affinity than the approved MPP inhibitors compared in this study, including remdesivir, Favipiravir, and alpha-ketoamide. A comparative study among the screened putative MPP inhibitors revealed that the amino acids T25, T26, H41, M49, L141, N142, G143, C145, H164, M165, E166, D187, R188, and Q189 are at potentially critical positions for being surface hotspots in the MPP of SARS-CoV-2. The top 5 predicted drugs (Paritaprevir, Glecaprevir, Nelfinavir, and Lopinavir) and the topmost analog showed conformational stability in the active site of the SARS-CoV-2 MP protein. The study also suggested that Paritaprevir and its analog (CID 131982844) might be effective against SARS-CoV-2. The current findings are limited to in silico analysis and lack in vivo efficacy testing; thus, we strongly recommend a quick assessment of Paritaprevir and its analog (CID 131982844) in a clinical trial.

Development and Validation of a New LC-MS/MS Analytical Method for Direct-Acting Antivirals and Its Application in End-Stage Renal Disease Patients

BACKGROUND AND OBJECTIVE

The effectiveness of direct-acting antivirals (DAAs) is not well established in end-stage renal disease (ESRD) patients. Assessment of the plasma concentrations may support understanding of their therapeutic outcomes in this population. The aim of this study is to develop a direct, yet matrix-effect tolerant, analytical method for determining DAAs in the plasma of ESRD patients while maintaining a moderate cost per sample and with an improved analyte extraction recovery.

METHODS

In this study, a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for the analysis of ombitasvir (OMB), paritaprevir (PRT) and ritonavir (RIT) in plasma. Sample preparation was performed using the liquid-liquid extraction (LLE) method. Isocratic separation was performed using a mixture of methanol and 10 mM ammonium acetate (79:21, v/v) followed by MS/MS detection. The method was validated and applied to determine DAAs in the plasma of ESRD patients (n = 7).

RESULTS

The developed method was linear (r²> 0.995), accurate (89.4 ± 7.8 to 108.3 ± 3.0) and precise (% CV 0.9-15.0) and showed improved recovery (> 80) over previously published ones in the range 5-250, 30-1,500, 20-1,000 ng/mL for OMB, PRT and RIT, respectively. Relative matrix effect was absent, and the method accurately determined the three DAAs in real-life samples (n = 7).

CONCLUSIONS

An efficient analytical method for the determination of DAAs is presented. The method overcomes the potential analytical response fluctuation in ESRD. The developed method show improved extraction recoveries and is suitable for routine application in developing economies where hepatitis C virus is most prevalent.

Pharmacokinetic Interactions between the Hepatitis C Virus Inhibitors Elbasvir and Grazoprevir and HIV Protease Inhibitors Ritonavir, Atazanavir, Lopinavir, and Darunavir in Healthy Volunteers

The combination of the hepatitis C virus (HCV) nonstructural protein 5A (NS5A) inhibitor elbasvir and the NS3/4A protease inhibitor grazoprevir is a potent, once-daily therapy indicated for the treatment of chronic HCV infection in individuals coinfected with human immunodeficiency virus (HIV). We explored the pharmacokinetic interactions of elbasvir and grazoprevir with ritonavir and ritonavir-boosted HIV protease inhibitors in three phase 1 trials. Drug-drug interaction trials with healthy participants were conducted to evaluate the effect of ritonavir on the pharmacokinetics of grazoprevir (n = 10) and the potential two-way pharmacokinetic interactions of elbasvir (n = 30) or grazoprevir (n = 39) when coadministered with ritonavir-boosted atazanavir, lopinavir, or darunavir. Coadministration of ritonavir with grazoprevir increased grazoprevir exposure; the geometric mean ratio (GMR) for grazoprevir plus ritonavir versus grazoprevir alone area under the concentration-time curve from 0 to 24 h (AUC_0-24) was 1.91 (90% confidence interval [CI]; 1.31 to 2.79). Grazoprevir exposure was markedly increased with coadministration of atazanavir-ritonavir, lopinavir-ritonavir, and darunavir-ritonavir, with GMRs for grazoprevir AUC_0-24 of 10.58 (90% CI, 7.78 to 14.39), 12.86 (90% CI, 10.25 to 16.13), and 7.50 (90% CI, 5.92 to 9.51), respectively. Elbasvir exposure was increased with coadministration of atazanavir-ritonavir, lopinavir-ritonavir, and darunavir-ritonavir, with GMRs for elbasvir AUC_0-24 of 4.76 (90% CI, 4.07 to 5.56), 3.71 (90% CI, 3.05 to 4.53), and 1.66 (90% CI, 1.35 to 2.05), respectively. Grazoprevir and elbasvir had little effect on atazanavir, lopinavir, and darunavir pharmacokinetics. Coadministration of elbasvir-grazoprevir with atazanavir-ritonavir, lopinavir-ritonavir, or darunavir-ritonavir is contraindicated, owing to an increase in grazoprevir exposure. Therefore, HIV treatment regimens without HIV protease inhibitors should be considered for HCV/HIV-coinfected individuals who are being treated with elbasvir-grazoprevir.

Pharmacokinetics of Ombitasvir, Paritaprevir, Ritonavir, and Dasabuvir in Healthy Chinese Subjects and HCV GT1b-Infected Chinese, South Korean and Taiwanese Patients

BACKGROUND/PURPOSE

The 3 direct-acting antiviral (3D) regimen of ombitasvir/paritaprevir/ritonavir plus dasabuvir has recently been approved in several Asian geographic regions for the treatment of hepatitis C virus (HCV) genotype (GT) 1 infection. The pharmacokinetics of the components of the 3D regimen with or without ribavirin were evaluated in healthy Chinese subjects and HCV GT1b-infected Chinese, South Korean, and Taiwanese patients, with or without cirrhosis, to determine how the drug exposures in Asian populations compare with historical data in Western populations.

METHODS

Participants received ombitasvir/paritaprevir/ritonavir 25/150/100 mg once daily plus dasabuvir 250 mg twice daily for 14 days (healthy subjects, n = 36) or 12 weeks (HCV patients, n = 754). Patients with compensated cirrhosis also received ribavirin 1000 or 1200 mg divided twice daily, per the local label. Intensive or sparse pharmacokinetic sampling was performed for assessments of plasma drug concentrations.

RESULTS

The exposures [maximum plasma concentration (C_max) and area under the plasma concentration-time curve (AUC)] of the components of the 3D regimen were comparable (< 20% difference) in healthy Chinese subjects residing in China or the United States. In addition, the trough plasma concentrations (C_trough) in HCV GT1b-infected Asian patients were either similar to (ombitasvir) or within 75% of (paritaprevir and dasabuvir) those in Western patients without cirrhosis, or similar to (ombitasvir and paritaprevir) or within 100% of (dasabuvir) those in Western patients with cirrhosis, with widely overlapping ranges of individual values. Generally comparable drug exposures were observed among Chinese, South Korean, and Taiwanese ethnicities for noncirrhotic and cirrhotic patients.

CONCLUSION

Collectively, the results of these pharmacokinetic analyses support the use of the same dose of the 3D regimen for Asian and Western patients. CLINICALTRIALS.GOV: NCT02534870, NCT02517515, NCT02517528.

Minor contribution of CYP3A5 to the metabolism of hepatitis C protease inhibitor paritaprevir in vitro

Paritaprevir (PTV) is a non-structural protein 3/4A protease inhibitor developed for the treatment of hepatitis C disease as a fixed dose combination of ombitasvir (OBV) and ritonavir (RTV) with or without dasabuvir. The aim of this study was to evaluate the effects of cytochrome P450 (CYP) 3A5 on in vitro PTV metabolism using human recombinant CYP3A4, CYP3A5 (rCYP3A4, rCYP3A5) and human liver microsomes (HLMs) genotyped as either CYP3A5*1/*1, CYP3A5*1/*3 or CYP3A5*3/*3. The intrinsic clearance (CL_int, V_max/K_m) for the production of a metabolite from PTV in rCYP3A4 was 1.5 times higher than that in rCYP3A5. The PTV metabolism in CYP3A5*1/*1 and CYP3A5*1/*3 HLMs expressing CYP3A5 was comparable to that in CYP3A5*3/*3 HLMs, which lack CYP3A5. CYP3A4 expression level was significantly correlated with PTV disappearance rate and metabolite formation. In contrast, there was no such correlation found for CYP3A5 expression level. This study represents that the major CYP isoform involved in PTV metabolism is CYP3A4, with CYP3A5 having a minor role in PTV metabolism. The findings of the present study may provide foundational information on PTV metabolism, and may further support dosing practices in HCV-infected patients prescribed PTV-based therapy.

Pharmacokinetic Interactions and Safety of Coadministration of Glecaprevir and Pibrentasvir in Healthy Volunteers

BACKGROUND AND OBJECTIVE

Glecaprevir and pibrentasvir are pangenotypic direct-acting antiviral agents for the treatment of chronic hepatitis C virus infection. The aim of the present study was to evaluate the drug-drug interaction and safety of glecaprevir and pibrentasvir coadministration in healthy volunteers.

METHODS

In this open-label, randomized, multiple-dose, Phase 1 study in 72 subjects, glecaprevir (100-1200 mg once daily) and pibrentasvir (40-200 mg once daily) were administered alone for 7 days and then in combination for another 7 days. Intensive blood sampling was performed on Days 1, 7, 8, and 14, and pharmacokinetic interactions were assessed using a repeated measures analysis of glecaprevir and pibrentasvir maximum plasma concentration (C _max) and area under the curve (AUC).

RESULTS

Coadministration of glecaprevir 400 mg increased pibrentasvir 120 and 40 mg steady-state C _max and AUC values to 2.9-6.3-fold, and coadministration of glecaprevir 700 mg increased pibrentasvir 160 mg steady-state C _max and AUC₂₄ values to up to sevenfold of the values when pibrentasvir was administered alone. Glecaprevir C _max and AUC values during coadministration were less than 1.5-fold of the values when glecaprevir was administered alone. The combination of glecaprevir and pibrentasvir at doses up to 400 mg was well tolerated by the healthy subjects in this study. High glecaprevir exposures at 700 and 1200 mg were associated with grade 2/3 elevations in alanine aminotransferase, aspartate aminotransferase, and/or bilirubin.

CONCLUSIONS

Coadministration of pibrentasvir 120 mg with glecaprevir doses up to 400 mg resulted in increases in pibrentasvir exposures without significant changes in glecaprevir exposures in the absence of any clinically significant laboratory abnormalities.

Clinical Pharmacokinetics of Paritaprevir

Paritaprevir is a potent hepatitis C virus (HCV) nonstructural (NS) protein 3/4A protease inhibitor that is used in combination with other direct-acting antivirals (DAAs) for the treatment of chronic HCV infection. Paritaprevir is primarily metabolized by cytochrome P450 (CYP) 3A4 and is administered with a low dose of ritonavir to achieve drug concentrations suitable for once-daily dosing. Coadministration of paritaprevir with ritonavir increases the half-life of single-dose paritaprevir from approximately 3 h to 5-8 h, doubles the time to maximum plasma concentration (T _max) from 2.3 to 4.7 h, and increases exposures 30-fold for maximum observed plasma concentration (C _max), 50-fold for area under the plasma concentration-time curve (AUC), and >300-fold for trough concentration (C ₂₄). Paritaprevir displays highly variable, nonlinear pharmacokinetics, with C _max and AUC increasing in a greater than dose proportional manner when administered with or without ritonavir. In the presence of ritonavir, paritaprevir is excreted mostly unchanged in feces via biliary excretion. Paritaprevir exposures are higher in Japanese subjects compared with Caucasian subjects; however, no dose adjustment is needed for Japanese patients as the higher exposures are safe and well tolerated. The pharmacokinetic characteristics of paritaprevir are similar between healthy subjects and HCV-infected patients, and are not appreciably altered by mild or moderate hepatic impairment or mild, moderate, or severe renal impairment, including those on dialysis. Paritaprevir exposures are increased in patients with severe hepatic impairment. Although the presence of a low dose of ritonavir in paritaprevir-containing regimens increases the likelihood of drug-drug interactions, results from several drug interaction studies demonstrated that paritaprevir-containing regimens can be coadministered with many comedications that are commonly prescribed in HCV-infected patients.

Potential drug-drug interactions of OMBITASVIR, PARITAPREVIR/ritonavir ± DASABUVIR ± ribavirin in clinical practice

BACKGROUND & AIMS

Drug-drug interactions (DDIs) with ombitasvir/paritaprevir/ritonavir with or without dasabuvir and with or without ribavirin (OBV/PTV/r ± DSV ± RBV) are common in clinical trials. Our aim was to analyze the prevalence and management of potential DDIs and adverse events (AEs) related to DDIs in patients with chronic hepatitis C (CHC) receiving OBV/PTV/r ± DSV ± RBV in clinical practice.

METHODS

177 CHC patients started OBV/PTV/r ± DSV ± RBV in 4 Spanish hospitals and were screened for potential DDIs using the University of Liverpool database. Patients were classified according to the most serious potential DDIs at baseline and AEs during therapy.

RESULTS

At least one potential DDI was found in 110 (62.1%) patients: 100 (56.5%) had at least one manageable potential DDI and 10 (5.6%) at least one contraindicated. Patients with potential DDIs were receiving a higher number of concomitant drugs (4 vs. 2, P < 0.001). Routine medication was modified at baseline due to potential DDIs in 49 (27.7%) patients. During antiviral treatment, 67 (37.9%) patients presented at least one AE. In 9 (4.5%) patients, a DDI was suspected between OBV/PTV/r ± DSV ± RBV and the concomitant drug, requiring antiviral discontinuation in 4 patients.

CONCLUSIONS

Potential DDIs are frequent with OBV/PTV/r ± DSV ± RBV, although a change in baseline medication is made in only one-quarter of patients. More than half of potential DDIs were only followed, and only 5% of patients developed AEs in which the implication of DDIs could not be excluded.

Gadoxetic acid-enhanced magnetic resonance imaging to predict paritaprevir-induced hyperbilirubinemia during treatment of hepatitis C

Background

Paritaprevir inhibits organic anion–transporting polypeptide (OATP)1B1 and OATP1B3, which transport bilirubin. Hyperbilirubinemia is an adverse event reported during hepatitis C treatment. Gadoxetic acid is also transported by OATP1B1/1B3. We evaluated whether the enhancement effect in gadoxetic acid–enhanced magnetic resonance (MR) imaging could predict the plasma concentration of paritaprevir and might anticipate the development of hyperbilirubinemia.

Methods

This prospective study evaluated 27 patients with hepatitis C who underwent gadoxetic acid–enhanced MR imaging prior to treatment with ombitasvir, paritaprevir, and ritonavir. The contrast enhancement index (CEI), a measure of liver enhancement during the hepatobiliary phase, was assessed. Plasma trough concentrations, and concentrations at 2, 4, and 6 h after dosing were determined 7 d after the start of treatment.

Results

Seven patients (26%) developed hyperbilirubinemia (≥ 1.6 mg/dl). Paritaprevir trough concentration (C_trough) was significantly higher in patients with hyperbilirubinemia than in those without (p = 0.022). We found an inverse relationship between CEI and C_trough (r = 0.612, p = 0.001), while there was not a significantly weak inverse relationship between AUC_{0–6 h} and CEI (r = −0.338, p = 0.085). The partial correlation coefficient between CEI and C_trough was −0.425 (p = 0.034), while excluding the effects of albumin and the FIB-4 index. Receiver operating characteristic (ROC) curve analysis showed that the CEI was relatively accurate in predicting hyperbilirubinemia, with area under the ROC of 0.882. Multivariate analysis showed that the CEI < 1.61 was the only independent predictor related to the development of hyperbilirubinemia, with an odds ratio of 9.08 (95% confidence interval 1.05–78.86, p = 0.046).

Conclusions

Hepatic enhancement with gadoxetic acid was independently related to paritaprevir concentration and was an independent pretreatment factor in predicting hyperbilirubinemia. Gadoxetic acid–enhanced MR imaging can therefore be useful in determining the risk of paritaprevir-induced hyperbilirubinemia.

Exposure-Safety Response Relationship for Ombitasvir, Paritaprevir/Ritonavir, Dasabuvir, and Ribavirin in Patients with Chronic Hepatitis C Virus Genotype 1 Infection: Analysis of Data from Five Phase II and Six Phase III Studies

BACKGROUND AND OBJECTIVES

All-oral direct-acting antiviral regimens that include combinations of ombitasvir, paritaprevir, ritonavir, and dasabuvir with or without ribavirin were evaluated in hepatitis C virus-infected patients in phase II/III clinical studies. The objective of these analyses was to quantify the relationship between exposures of the components of the regimen and laboratory values and to determine covariates that could influence the relationship.

METHODS

Exposure-safety response relationships between individual components of the direct-acting antiviral regimens and clinically important laboratory values were explored using data from 2998 patients from 11 phase II/III clinical studies. Multivariate logistic regression analyses were used to identify significant relationships between predictor variables and response variables.

RESULTS

No statistically significant associations were observed between ombitasvir, dasabuvir, or ritonavir exposures and maximum post-baseline alanine aminotransferase (ALT) or total bilirubin grade or minimum hemoglobin grade. A two-fold increase in paritaprevir exposure from therapeutic exposure was predicted to increase the probability of experiencing a grade 3 or higher increase in ALT by 0.5% and bilirubin by 1.1%. In the phase II/III clinical studies, ALT and bilirubin increases were reversible with continued dosing or after treatment cessation. Other correlates with adverse events of clinical importance included concomitant ribavirin treatment, sex, race, and presence of cirrhosis, consistent with previous observations.

CONCLUSIONS

Exposure-response analyses from phase II/III studies with the combination direct-acting antiviral regimen indicated no statistically significant relationships with ombitasvir, dasabuvir, or ritonavir exposure, but a statistically significant association was observed between paritaprevir exposure and the probability of experiencing a grade 3 or higher increase in ALT or bilirubin.

Dose- and Formulation-Dependent Non-Linear Pharmacokinetic Model of Paritaprevir, a Protease Inhibitor for the Treatment of Hepatitis C Virus Infection: Combined Analysis from 12 Phase I Studies

BACKGROUND AND OBJECTIVES

Paritaprevir is a direct-acting antiviral agent that is a component of approved multidrug regimens used in the treatment of hepatitis C virus (HCV) infection. A population pharmacokinetic model for paritaprevir was developed using data from formulation, bioavailability, and drug-drug interaction studies that evaluated the pharmacokinetics of paritaprevir (coadministered with ritonavir to enhance exposure) with or without ombitasvir and/or dasabuvir at different paritaprevir dose levels.

METHODS

A non-linear mixed-effects modeling approach was applied to data from 12 phase I, single- and multiple-dose studies that enrolled a total of 369 healthy volunteers. Age, sex, race, ethnicity, body weight, body surface area, body mass index, and baseline creatinine clearance were evaluated as covariates during model development. In addition, the influences of dose, formulation, and concomitant medications (e.g. ombitasvir and dasabuvir) on paritaprevir bioavailability were included in the model.

RESULTS

A two-compartment model with first-order absorption and elimination optimally described paritaprevir plasma concentration-time data. Paritaprevir bioavailability was formulation- and dose-dependent, and increased supraproportionally. The accumulation of paritaprevir was 1.57-fold on repeated dosing compared with the first dose. Coadministration of dasabuvir increased paritaprevir bioavailability by 59 %; however, ombitasvir coadministration did not affect the pharmacokinetic profile of paritaprevir. No subject-specific covariate influenced the paritaprevir pharmacokinetics. The pharmacokinetic model was robust in bootstrap evaluations and was consistent with observed data based on diagnostic goodness-of-fit plots and visual predictive checks.

CONCLUSION

The complex pharmacokinetics of paritaprevir were well described by the model, which can be used as a basis for clinical trial dosing and further evaluations in patients with HCV.

Drug-Drug Interactions Between the Anti-Hepatitis C Virus 3D Regimen of Ombitasvir, Paritaprevir/Ritonavir, and Dasabuvir and Eight Commonly Used Medications in Healthy Volunteers

Background and Aims

The three direct-acting antiviral regimen of ombitasvir/paritaprevir/ritonavir and dasabuvir (3D regimen) is approved for treatment of hepatitis C virus (HCV) genotype 1 infection. Drug–drug interaction (DDI) studies of the 3D regimen and commonly used medications were conducted in healthy volunteers to provide information on coadministering these medications with or without dose adjustments.

Methods

Three phase I studies evaluated DDIs between the 3D regimen (ombitasvir/paritaprevir/ritonavir 25/150/100 mg once daily + dasabuvir 250 mg twice daily) and hydrocodone bitartrate/acetaminophen (5/300 mg), metformin hydrochloride (500 mg), diazepam (2 mg), cyclobenzaprine hydrochloride (5 mg), carisoprodol (250 mg), or sulfamethoxazole/trimethoprim (SMZ/TMP) (800/160 mg twice daily), all administered orally. DDI magnitude was determined using geometric mean ratios and 90 % confidence intervals for the maximum plasma concentration (C_max) and area under the plasma concentration–time curve (AUC).

Results

Changes in exposures (C_max and AUC geometric mean ratios) of acetaminophen, metformin, sulfamethoxazole, trimethoprim, and diazepam were ≤25 % upon coadministration with the 3D regimen. The C_max and AUC of nordiazepam, an active metabolite of diazepam, increased by 10 % and decreased by 44 %, respectively. Exposures of cyclobenzaprine and carisoprodol decreased by ≤40 and ≤46 %, respectively, whereas exposures of hydrocodone increased up to 90 %. Ombitasvir, paritaprevir, ritonavir, and dasabuvir exposures changed by ≤25 %, except for a 37 % decrease in paritaprevir C_max with metformin and a 33 % increase in dasabuvir AUC with SMZ/TMP.

Conclusions

Acetaminophen, metformin, sulfamethoxazole, and trimethoprim can be coadministered with the 3D regimen without dose adjustment. Higher doses may be needed for diazepam, cyclobenzaprine, and carisoprodol based on clinical monitoring. A 50 % lower dose and/or clinical monitoring should be considered for hydrocodone. No dose adjustment is necessary for the 3D regimen.

Ombitasvir and paritaprevir boosted with ritonavir and combined with dasabuvir for chronic hepatitis C

Hepatitis C is a leading cause of cirrhosis and hepatocellular carcinoma responsible for almost 700,000 deaths worldwide annually. Until 2014, management of HCV infections was based on interferon alfa containing regimens, with efficacy of 40-70% and a high adverse event rate. Interferon-free therapeutic options improved sustained viral response (SVR) rate to >90% and safety profile to placebo-like levels. Areas covered: This article describes all-oral regimen consisting of three direct acting antivirals (DAA) - ombitasvir (OBV), paritaprevir (PTV) and dasabuvir (DSV), which in clinical practice is boosted with ritonavir (r) and sometimes with ribavirin (RBV). This combination is registered for treatment of patients infected with HCV genotype 1 and 4. We focused on the regimen characteristics, pharmacokinetics, risk of resistance as well as efficacy and safety in clinical trials and real world studies. Expert commentary: Combination of OBV/PTV/r±DSV±RBV provides SVR rate of about 95% and good safety profile even in patients with compensated liver cirrhosis and failure with previous therapy. Currently it should be of particular value in areas with a predominance of genotype 1b infections. Due to the complexity and risk of drug to drug interactions, it will probably be replaced in coming few years with pangenotypic combinations of next generation DAAs.

Paritaprevir and Ritonavir Liver Concentrations in Rats as Assessed by Different Liver Sampling Techniques

The liver is crucial to pharmacology, yet substantial knowledge gaps exist in the understanding of its basic pharmacologic processes. An improved understanding for humans requires reliable and reproducible liver sampling methods. We compared liver concentrations of paritaprevir and ritonavir in rats by using samples collected by fine-needle aspiration (FNA), core needle biopsy (CNB), and surgical resection. Thirteen Sprague-Dawley rats were evaluated, nine of which received paritaprevir/ritonavir at 30/20 mg/kg of body weight by oral gavage daily for 4 or 5 days. Drug concentrations were measured using liquid chromatography-tandem mass spectrometry on samples collected via FNA (21G needle) with 1, 3, or 5 passes (FNA₁, FNA₃, and FNA₅); via CNB (16G needle); and via surgical resection. Drug concentrations in plasma were also assessed. Analyses included noncompartmental pharmacokinetic analysis and use of Bland-Altman techniques. All liver tissue samples had higher paritaprevir and ritonavir concentrations than those in plasma. Resected samples, considered the benchmark measure, resulted in estimations of the highest values for the pharmacokinetic parameters of exposure (maximum concentration of drug in serum [C_max] and area under the concentration-time curve from 0 to 24 h [AUC_0-24]) for paritaprevir and ritonavir. Bland-Altman analyses showed that the best agreement occurred between tissue resection and CNB, with 15% bias, followed by FNA₃ and FNA₅, with 18% bias, and FNA₁ and FNA₃, with a 22% bias for paritaprevir. Paritaprevir and ritonavir are highly concentrated in rat liver. Further research is needed to validate FNA sampling for humans, with the possible derivation and application of correction factors for drug concentration measurements.

Ultra-performance liquid chromatography tandem mass spectrometry for determination of Direct Acting Antiviral drugs in human liver fine needle aspirates

An ultra-performance liquid chromatography with triple quadrupole mass spectrometry method was developed and validated for the determination of direct acting antiviral drug concentrations in human liver fine needle aspirates. Liver fine needle aspirate (FNA) biopsy samples were homogenized in acetonitrile to stabilize the analytes and precipitate protein. The acetonitrile supernatants were diluted with internal standards and mobile phase. Separation was achieved with a Waters Acquity BEH C18 column (50×2.1mm, 1.7um) with a gradient elution of 0.1% formic acid in water and acetonitrile. The total run time was 4.25min. Detection of analytes was achieved using electrospray ionization (positive mode) and triple quadrupole selected reaction monitoring. Standard curve concentrations ranged from 12.5 to 5000ng/mL for dasabuvir and the m1 metabolite of dasabuvir, 1.25 to 2500ng/mL for ombitasvir and ritonavir, and 5.00 to 5000ng/mL for paritaprevir. The intra- and inter-day accuracy and precision were less than 13.7% in low, medium, and high quality control samples. The validated method was applied to the analysis of a liver fine needle aspirate of a patient undergoing direct acting antiviral therapy for hepatitis C virus.

Population pharmacokinetics of paritaprevir, ombitasvir, dasabuvir, ritonavir and ribavirin in hepatitis C virus genotype 1 infection: analysis of six phase III trials

AIM

The aim of the current study was to characterize the population pharmacokinetics of a triple direct-acting antiviral (DAA) regimen (3D) (ombitasvir, paritaprevir-ritonavir and dasabuvir) and adjunctive ribavirin, and estimate covariate effects in a broad spectrum of subjects with hepatitis C virus (HCV) genotype 1 infection.

METHODS

Pharmacokinetic data from six phase III studies and one phase II study in subjects receiving the currently approved doses of the 3D ± ribavirin regimen for treating HCV genotype 1 infection for 12 weeks or 24 weeks were characterized using separate population pharmacokinetic models, built using each component of the regimen from nonlinear mixed-effects methodology in NONMEM 7.3. In the models, demographic and clinical covariates were tested. Models were assessed via goodness-of-fit plots, visual predictive checks and bootstrap evaluations.

RESULTS

The population pharmacokinetic models for each component of the 3D ± ribavirin regimen (DAAs and ritonavir, n = 2348) and ribavirin (n = 1841) adequately described their respective plasma concentration-time data. Model parameter estimates were precise and robust, and all models showed good predictive ability. Significant covariate effects associated with apparent clearance and volume of distribution included age, body weight, gender, cirrhosis, HCV subtype, opioid or antidiabetic agent use, and creatinine clearance.

CONCLUSION

The population pharmacokinetics of the 3D ± ribavirin regimen components in HCV-infected patients were characterized using phase II and III HCV clinical trial data. Although several statistically significant covariates were identified, their effects were modest and not clinically meaningful to necessitate dose adjustments for any component of the 3D regimen.

Pharmacokinetics, Safety, and Tolerability of Single and Multiple Doses of ABT-493: A First-In-Human Study

ABT-493 is a hepatitis C virus nonstructural protein 3/4A protease inhibitor with pangenotypic antiviral activity. This study investigated the pharmacokinetics, safety, and tolerability of single and multiple ascending doses of ABT-493 and the effect of food and ritonavir coadministration on ABT-493 pharmacokinetics in healthy adults. In the blinded, randomized, placebo-controlled phase 1 single- and multiple-dose portions of the study, ABT-493 25-800 mg were evaluated as single doses, and 200, 400, and 800 mg were evaluated as multiple doses. The effect of food and ritonavir was assessed in a crossover unblinded fashion. ABT-493 pharmacokinetic parameters were estimated using noncompartmental methods. ABT-493 25-800 mg showed a greater than dose-proportional increase in exposures. Minimal accumulation (≤15%) was observed after ABT-493 200- and 400-mg multiple dosing; higher accumulations (approximately 80%) were observed after the 800-mg dose. ABT-493 harmonic mean half-life was 6-9 hours. Food had a minimal effect on ABT-493 exposures. All adverse events were assessed by the investigator as mild to moderate in severity, no serious adverse events were reported, and no subjects discontinued from the study. No clinically significant laboratory tests, vital signs, or electrocardiogram values were reported. A maximum tolerated dose was not reached.

Metabolism and Disposition of the Hepatitis C Protease Inhibitor Paritaprevir in Humans

Paritaprevir (also known as ABT-450), a potent NS3-4A serine protease inhibitor [identified by AbbVie (North Chicago, IL) and Enanta Pharmaceuticals (Watertown, MA)] of the hepatitis C virus (HCV), has been developed in combination with ombitasvir and dasabuvir in a three-direct-acting antiviral agent (DAA) oral regimen for the treatment of patients infected with HCV genotype 1. This article describes the mass balance, metabolism, and disposition of paritaprevir in humans. After the administration of a single 200-mg oral dose of [(14)C]paritaprevir coadministered with 100 mg of ritonavir to four male healthy volunteers, the mean total percentage of the administered radioactive dose recovered was 96.5%, with recovery in individual subjects ranging from 96.0% to 96.9%. Radioactivity derived from [(14)C]paritaprevir was primarily eliminated in feces (87.8% of the dose). Radioactivity recovered in urine accounted for 8.8% of the dose. The biotransformation of paritaprevir in humans involves: 1) P450-mediated oxidation on the olefinic linker, the phenanthridine group, the methylpyrazinyl group, or combinations thereof; and 2) amide hydrolysis at the acyl cyclopropane-sulfonamide moiety and the pyrazine-2-carboxamide moiety. Paritaprevir was the major component in plasma [90.1% of total radioactivity in plasma, AUC from time 0 to 12 hours (AUC0-12hours) pool]. Five minor metabolites were identified in plasma, including the metabolites M2, M29, M3, M13, and M6; none of the metabolites accounted for greater than 10% of the total radioactivity. Paritaprevir was primarily eliminated through the biliary-fecal route followed by microflora-mediated sulfonamide hydrolysis to M29 as a major component in feces (approximately 60% of dose). In summary, the biotransformation and clearance pathways of paritaprevir were characterized, and the structures of metabolites in circulation and excreta were elucidated.

Development and validation of a UPLC-MS/MS method for the simultaneous determination of paritaprevir and ritonavir in rat liver

AIM

Determination of paritaprevir and ritonavir in rat liver tissue samples.

RESULTS

We successfully validated a UPLC-MS/MS method to measure paritaprevir and ritonavir in rat liver using deuterated internal standards (d8-paritapervir and d6-ritonavir). The method is linear from 20 to 20,000 and 5 to 10,000 pg on column for paritaprevir and ritonavir, respectively, and is normalized per milligram tissue. Interday and intraday variability ranged from 0.591 to 5.33% and accuracy ranged from -6.68 to 10.1% for quality control samples. The method was then applied to the measurement of paritaprevir and ritonavir in rat liver tissue samples from a pilot study.

CONCLUSION

The validated method is suitable for measurement of paritaprevir and ritonavir within rat liver tissue samples for PK studies.

Pharmacokinetics and tolerability of paritaprevir, a direct acting antiviral agent for hepatitis C virus treatment, with and without ritonavir in healthy volunteers

AIMS

Paritaprevir is a direct acting antiviral agent for use as part of a multidrug hepatitis C virus infection treatment regimen. To characterize the pharmacokinetics, safety, and tolerability of paritaprevir and determine an optimal dosing regimen for subsequent evaluations, clinical studies were conducted with paritaprevir alone or with ritonavir, a cytochrome P450 3A4 inhibitor anticipated to increase paritaprevir exposure.

METHODS

Two phase 1, double-blind, placebo-controlled, parallel group studies were conducted in healthy volunteers (NCT00850044 and NCT00931281). Single dose study participants (n = 87) were randomized to one time administration of either paritaprevir or placebo, or paritaprevir with ritonavir or placebo. Participants (n = 38) enrolled in the multiple dose study received paritaprevir with ritonavir or placebo once or twice daily for 14 days. Pharmacokinetics, safety and tolerability were assessed throughout the study treatment periods.

RESULTS

After single or multiple dose administration, paritaprevir displayed non-linear pharmacokinetics, with maximum plasma concentration and area under the plasma concentration-time curve increasing in a greater than dose proportional manner. Concomitant administration of 100 mg ritonavir increased paritaprevir exposure from a 300 mg dose approximately 30- to 50-fold and extended paritaprevir half-life. The tolerability of paritaprevir was similar with or without ritonavir. Asymptomatic, transient increases in bilirubin were observed but were not associated with abnormalities in other liver function tests.

CONCLUSIONS

Paritaprevir exhibits non-linear pharmacokinetics with greater than dose proportional increases in exposure after single or multiple dosing. Co-administration with ritonavir increases paritaprevir exposure and half-life without adversely influencing tolerability.