Metabolism and Disposition of Pan-Genotypic Inhibitor of Hepatitis C Virus NS5A Ombitasvir in Humans

Human absorption, distribution, metabolism, and excretion studies: Conventional or microtracer?

A human absorption, distribution, metabolism, and excretion (hADME) study is an essential clinical pharmacology study for small-molecule drugs. The study provides insights into circulating drug-related materials and the drug's elimination pathways in humans, which can guide future studies on safety and drug-drug interaction of metabolites as well as organ impairment and drug-drug interaction of the parent drug. The 2 hADME study types, namely conventional and microtracer, are comprehensively compared in this manuscript. A review of literature found that conventional hADME studies were approximately 7 times that of microtracer hADME studies for small molecule and peptide drugs based on publications in 3 peer-reviewed journals from 2010 to 2024. Each study type has advantages and disadvantages. The advantages of conventional hADME studies primarily include the ease, low cost, and flexibility of radiometric sample analysis. In contrast, the advantages of microtracer hADME studies primarily include exemption from prerequisite studies and use of non-good manufacturing practice 14C-labeled materials. The disadvantages of each study type are essentially the advantages of the other. The manuscript also discusses scenarios where a microtracer hADME study may be preferable. Finally, recommendations are provided on selecting the appropriate hADME study type for an investigational drug. SIGNIFICANCE STATEMENT: The manuscript discusses 2 primary human absorption, distribution, metabolism, and excretion study types: conventional and microtracer. It covers published literature studies, the pros and cons of each type, scenarios for conducting microtracer studies, and a recommended decision tree for selecting the appropriate human absorption, distribution, metabolism, and excretion study type.

Utility of Common In Vitro Systems for Predicting Circulating Metabolites

In vitro systems such as cultured hepatocytes are used early in drug development as a proxy for in vivo data to predict metabolites in human and the potential preclinical species. These data support preclinical species selection for toxicity studies as well as provide early evidence for potential active and reactive metabolites that can be generated in human. Although in vivo data would be best to select preclinical species for a given compound, only in vitro systems are available when selecting toxicity study species. However, as with any in vitro system, the correlation to actual in vivo results can be variable. Understanding the reliability of predicting in vivo metabolites from the various available in vitro assays and determining which system may be most predictive would help de-risk drug development teams' selection process. In this manuscript, we address these questions: can in vitro systems predict circulating metabolites? If so, is predictivity quantitative or indicative of what levels may be seen circulating? Of the currently available in vitro systems, is one better than the others at generating predictive metabolites? To address the first two issues (general in vitro/in vivo predictivity, and whether any in vitro/in vivo correlations are quantitative), we used historical data from Abbott/AbbVie to compare in vitro metabolite profiles with metabolite profiles from in vivo absorption, distribution, metabolism, excretion, and clinical studies. In this retrospective analysis of historic metabolite profiling data, in vitro systems predicted ∼50% of circulating metabolites present in vivo, across preclinical species and human, with no correlation between apparent concentrations in vitro versus in vivo. To address the final question, we selected 10 commercially available compounds with published metabolism data and incubated them in five common in vitro systems (microsomes, liver S9, suspension hepatocytes, HμREL cocultured hepatocytes, and hepatocyte spheroids); the new in vitro metabolite profiling data were compared against published in vivo data to determine whether any individual system was more accurate in generating known major human circulating metabolites. Suspension hepatocytes and cocultured hepatocytes marginally outperformed the other systems. Current in vitro systems have value early in development when in vivo studies are not feasible and are required for regulatory filings to support preclinical toxicology species selection but should not be treated as wholly representative of a given drug's in vivo metabolism. SIGNIFICANCE STATEMENT: This is a comprehensive assessment of historic metabolism data quantitating the success rate of in vitro to in vivo predictivity. Reliability of in vitro systems for metabolite profiling is important for early drug development, and understanding predictivity will help give appropriate context to the data. New data were also generated to compare common in vitro liver models to determine whether any could be definitively identified as more predictive of human circulating metabolites than others.

Progress in the Stereoselective Synthesis Methods of Pyrrolidine-Containing Drugs and Their Precursors

The presented review systematizes and summarizes the data on the synthesis of pyrrolidine derivatives, which are precursors for obtaining drugs. Based on the analysis of published data, the most promising directions in the synthesis of biologically active compounds containing a pyrrolidine ring are identified. Stereoselective synthesis methods are classified based on the source of the pyrrolidine ring. The first group includes methods that use a pyrrolidine ring as the starting compound. The second group combines stereoselective methods of cyclization of acyclic starting compounds, which lead to optically pure pyrrolidine derivatives.

Recent Updates on Viral Oncogenesis: Available Preventive and Therapeutic Entities

Human viral oncogenesis is a complex phenomenon and a major contributor to the global cancer burden. Several recent findings revealed cellular and molecular pathways that promote the development and initiation of malignancy when viruses cause an infection. Even, antiviral treatment has become an approach to eliminate the viral infections and prevent the activation of oncogenesis. Therefore, for a better understanding, the molecular pathogenesis of various oncogenic viruses like, hepatitis virus, human immunodeficiency viral (HIV), human papillomavirus (HPV), herpes simplex virus (HSV), and Epstein-Barr virus (EBV), could be explored, especially, to expand many potent antivirals that may escalate the apoptosis of infected malignant cells while sparing normal and healthy ones. Moreover, contemporary therapies, such as engineered antibodies antiviral agents targeting signaling pathways and cell biomarkers, could inhibit viral oncogenesis. This review elaborates the recent advancements in both natural and synthetic antivirals to control viral oncogenesis. The study also highlights the challenges and future perspectives of using antivirals in viral oncogenesis.

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.

Hepatitis C - New drugs and treatment prospects

Hepatitis C virus (HCV) affects approx. 3% of the world's population and accounts for ca 300 000 deaths per year. 80% of individuals with HCV develop chronic symptoms which, when untreated, may cause cirrhosis (27%) or hepatocellular carcinoma (25%). The hepatitis C virus is a (+)ssRNA enveloped virus of the family Flaviviridae. Seven major HCV genotypes and their subtypes (a, b) have been identified. In the 1990s, interferons alpha-2 were used in the treatment of HCV and in the next decade HCV therapy was based on pegylated interferon alpha-2 in combination with ribavirin. Since 2011, interferons alpha, DNA and RNA polymerase inhibitors, NS3/4A RNA protease inhibitors, NS5 RNA serine protease inhibitors, NS5B RNA polymerase inhibitors have been approved for clinical use. Monotherapy is avoided in medication due to rapidly developing viral resistance. A total of 113 papers were included comprising original publications and reviews. The paper reviews the molecular targets and chemical structures of drugs used in HCV treatment. Indications and contraindications for anti-HCV drugs are also discussed together with application regimens.

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.

Effects of chronic kidney disease stage 4, end-stage renal disease, or dialysis on the plasma concentrations of ombitasvir, paritaprevir, ritonavir, and dasabuvir in patients with chronic HCV infection: pharmacokinetic analysis of the phase 3 RUBY-I and RUBY-II trials

PURPOSE

To characterize the pharmacokinetics of ombitasvir, paritaprevir, ritonavir, dasabuvir, and ribavirin in hepatitis C virus (HCV)-infected patients with chronic kidney disease stage 4 (CKD4) or end-stage renal disease (ESRD), including those on dialysis, in the open-label phase 3 RUBY-I and RUBY-II studies.

METHODS

Patients (n = 18 CKD4, n = 68 ESRD) received ombitasvir/paritaprevir/ritonavir 25/150/100 mg once daily ± dasabuvir 250 mg twice daily ± ribavirin 200 mg once daily for 12 or 24 weeks. Intensive pharmacokinetic samples were collected from ten patients; sparse samples were collected from all patients. Arterial and venous samples were collected from three patients during hemodialysis. Area under the plasma concentration-time curve (AUC) was estimated using noncompartmental analyses for intensive data, and steady-state trough concentrations (C_trough) were obtained from the sparse data. Pharmacokinetic results from RUBY-I and RUBY-II were compared empirically to historical data.

RESULTS

The AUC values of ombitasvir, paritaprevir, ritonavir, and dasabuvir were comparable between CKD4 and ESRD patients and were within the range of values observed in historical studies; dialysis had no effect on drug exposures. Ribavirin was extracted during hemodialysis but had similar exposures on dialysis and non-dialysis days. Individual steady-state C_trough values for each drug overlapped between CKD4 and ESRD patients, and values in both groups were similar to historical values.

CONCLUSION

Plasma concentrations of ombitasvir, paritaprevir, ritonavir, and dasabuvir were not altered by renal impairment or dialysis, suggesting these agents can be administered to HCV-infected CKD4 or ESRD patients, including those on dialysis, without dose adjustment.

TRIAL REGISTRATION

Clinicaltrials.gov identifiers: NCT02207088 (RUBY-I) and NCT02487199 (RUBY-II).

Clinical Pharmacokinetics of Ombitasvir

Ombitasvir is a potent, nonstructural protein 5A inhibitor of the hepatitis C virus (HCV) that is used in combination with other direct-acting antivirals for the treatment of chronic HCV infection. Ombitasvir is predominantly metabolized by amide hydrolysis followed by oxidative metabolism and is a substrate of P-glycoprotein. Ombitasvir displays linear pharmacokinetics with minimal accumulation and is eliminated via metabolism and biliary excretion. A negligible amount of unchanged drug is excreted in urine. Exposures are comparable across Chinese, Japanese, and non-Asian subjects. The pharmacokinetic characteristics of ombitasvir are similar in healthy subjects and HCV-infected patients, and are not appreciably altered by hepatic or renal impairment. Results from several drug interaction studies demonstrated that ombitasvir has a low potential for drug interactions.

Current antiviral drugs and their analysis in biological materials - Part II: Antivirals against hepatitis and HIV viruses

This review is a Part II of the series aiming to provide comprehensive overview of currently used antiviral drugs and to show modern approaches to their analysis. While in the Part I antivirals against herpes viruses and antivirals against respiratory viruses were addressed, this part concerns antivirals against hepatitis viruses (B and C) and human immunodeficiency virus (HIV). Many novel antivirals against hepatitis C virus (HCV) and HIV have been introduced into the clinical practice over the last decade. The recent broadening portfolio of these groups of antivirals is reflected in increasing number of developed analytical methods required to meet the needs of clinical terrain. Part II summarizes the mechanisms of action of antivirals against hepatitis B virus (HBV), HCV, and HIV, their use in clinical practice, and analytical methods for individual classes. It also provides expert opinion on state of art in the field of bioanalysis of these drugs. Analytical methods reflect novelty of these chemical structures and use by far the most current approaches, such as simple and high-throughput sample preparation and fast separation, often by means of UHPLC-MS/MS. Proper method validation based on requirements of bioanalytical guidelines is an inherent part of the developed methods.

Mechanisms and Predictions of Drug-Drug Interactions of the Hepatitis C Virus Three Direct-Acting Antiviral Regimen: Paritaprevir/Ritonavir, Ombitasvir, and Dasabuvir

To assess drug-drug interaction (DDI) potential for the three direct-acting antiviral (3D) regimen of ombitasvir, dasabuvir, and paritaprevir, in vitro studies profiled drug-metabolizing enzyme and transporter interactions. Using mechanistic static and dynamic models, DDI potential was predicted for CYP3A, CYP2C8, UDP-glucuronosyltransferase (UGT) 1A1, organic anion-transporting polypeptide (OATP) 1B1/1B3, breast cancer resistance protein (BCRP), and P-glycoprotein (P-gp). Perpetrator static model DDI predictions for metabolizing enzymes were within 2-fold of the clinical observations, but additional physiologically based pharmacokinetic modeling was necessary to achieve the same for drug transporters. When perpetrator interactions were assessed, ritonavir was responsible for the strong increase in exposure of sensitive CYP3A substrates, whereas paritaprevir (an OATP1B1/1B3 inhibitor) greatly increased the exposure of sensitive OATP1B1/1B3 substrates. The 3D regimen drugs are UGT1A1 inhibitors and are predicted to moderately increase plasma exposure of sensitive UGT1A1 substrates. Paritaprevir, ritonavir, and dasabuvir are BCRP inhibitors. Victim DDI predictions were qualitatively in line with the clinical observations. Plasma exposures of the 3D regimen were reduced by strong CYP3A inducers (paritaprevir and ritonavir; major CYP3A substrates) but were not affected by strong CYP3A4 inhibitors, since ritonavir (a CYP3A inhibitor) is already present in the regimen. Strong CYP2C8 inhibitors increased plasma exposure of dasabuvir (a major CYP2C8 substrate), OATP1B1/1B3 inhibitors increased plasma exposure of paritaprevir (an OATP1B1/1B3 substrate), and P-gp or BCRP inhibitors (all compounds are substrates of P-gp and/or BCRP) increased plasma exposure of the 3D regimen. Overall, the comprehensive mechanistic assessment of compound disposition along with mechanistic and PBPK approaches to predict victim and perpetrator DDI liability may enable better clinical management of nonstudied drug combinations with the 3D regimen.

Ombitasvir/Paritaprevir/Ritonavir: A Review in Chronic HCV Genotype 4 Infection

A fixed-dose tablet comprising the NS5A inhibitor ombitasvir, the NS3/4A inhibitor paritaprevir and ritonavir (ombitasvir/paritaprevir/ritonavir) (Technivie(®), Viekirax(®)) is available for use, in combination with ribavirin, for the treatment of chronic hepatitis C virus (HCV) genotype 4 infection. High sustained virological response rates at 12 weeks post-treatment (SVR12) were achieved in treatment-naive or -experienced patients with chronic HCV genotype 4 infection, including patients without cirrhosis who received ombitasvir plus paritaprevir and ritonavir in combination with ribavirin for 12 weeks (SVR12 100 %) (PEARL-I trial), patients with compensated cirrhosis who received ombitasvir/paritaprevir/ritonavir plus ribavirin for 12 or 16 weeks (SVR12 97 and 98 %) (AGATE-I trial), or Egyptian patients without cirrhosis who received ombitasvir/paritaprevir/ritonavir plus ribavirin for 12 weeks (SVR12 94 %) or with compensated cirrhosis who received ombitasvir/paritaprevir/ritonavir plus ribavirin for 12 or 24 weeks (SVR12 97 and 93 %) (AGATE-II trial). Ombitasvir/paritaprevir/ritonavir was generally well tolerated in patients with chronic HCV genotype 4 infection without cirrhosis or with compensated cirrhosis in clinical trials. There have been postmarketing reports of hepatic decompensation and hepatic failure, which mainly occurred in patients with advanced cirrhosis who received regimens containing ombitasvir/paritaprevir/ritonavir. In conclusion, ombitasvir/paritaprevir/ritonavir is a valuable option for use in patients with chronic HCV genotype 4 infection without cirrhosis or with compensated cirrhosis.