Viral hepatitis C therapy: pharmacokinetic and pharmacodynamic considerations

Sustained Virologic Response Rates Before and After Removal of Sobriety Restriction for Hepatitis C Virus Treatment Access

OBJECTIVES

Until November 1, 2018, Illinois Medicaid restricted coverage of hepatitis C virus (HCV) medication to patients with sobriety from alcohol and illicit substances for ≥12 months. This policy limited treatment access for patients with a high risk of HCV transmission, despite clinical trial and real-world data demonstrating high sustained virologic response (SVR) rates among patients with substance use. The objective of this study was to compare HCV SVR rates between patients treated before and after removal of the Illinois Medicaid sobriety restriction.

METHODS

We performed a retrospective cohort study of Medicaid-insured patients who completed direct-acting antiviral treatment at an urban, academic medical center in Illinois from January 1, 2014, through October 21, 2020. The primary endpoint was SVR. We compared group characteristics using χ2 or Fisher exact tests for categorical variables and Wilcoxon rank-sum tests for continuous variables. We used logistic regression to compare SVR rates before and after the policy change, adjusting for differences between groups.

RESULTS

A total of 496 patients (348 pre-policy change; 148 post-policy change) started treatment; excluding loss to follow-up/early discontinuation, SVR rates were 95.4% (309 of 324) pre-policy change and 97.1% (134 of 138) post-policy change. SVR rates did not differ after adjusting for the use of historic HCV regimens and the higher cirrhosis rate in the pre-policy change group compared with the post-policy change group (odds ratio = 0.98; 95% CI, 0.32-3.67).

CONCLUSION

HCV SVR rates were similar before and after removal of the Illinois Medicaid sobriety restriction, regardless of group differences. Results support HCV treatment regardless of documented sobriety to facilitate progress toward HCV elimination.

Efficacy of ultra-short, response-guided sofosbuvir and daclatasvir therapy for hepatitis C in a single-arm mechanistic pilot study

Background

World Health Organization has called for research into predictive factors for selecting persons who could be successfully treated with shorter durations of direct-acting antiviral (DAA) therapy for hepatitis C. We evaluated early virological response as a means of shortening treatment and explored host, viral and pharmacokinetic contributors to treatment outcome.

Methods

Duration of sofosbuvir and daclatasvir (SOF/DCV) was determined according to day 2 (D2) virologic response for HCV genotype (gt) 1- or 6-infected adults in Vietnam with mild liver disease. Participants received 4- or 8-week treatment according to whether D2 HCV RNA was above or below 500 IU/ml (standard duration is 12 weeks). Primary endpoint was sustained virological response (SVR12). Those failing therapy were retreated with 12 weeks SOF/DCV. Host IFNL4 genotype and viral sequencing was performed at baseline, with repeat viral sequencing if virological rebound was observed. Levels of SOF, its inactive metabolite GS-331007 and DCV were measured on days 0 and 28.

Results

Of 52 adults enrolled, 34 received 4 weeks SOF/DCV, 17 got 8 weeks and 1 withdrew. SVR12 was achieved in 21/34 (62%) treated for 4 weeks, and 17/17 (100%) treated for 8 weeks. Overall, 38/51 (75%) were cured with first-line treatment (mean duration 37 days). Despite a high prevalence of putative NS5A-inhibitor resistance-associated substitutions (RASs), all first-line treatment failures cured after retreatment (13/13). We found no evidence treatment failure was associated with host IFNL4 genotype, viral subtype, baseline RAS, SOF or DCV levels.

Conclusions

Shortened SOF/DCV therapy, with retreatment if needed, reduces DAA use in patients with mild liver disease, while maintaining high cure rates. D2 virologic response alone does not adequately predict SVR12 with 4-week treatment.

Funding

Funded by the Medical Research Council (Grant MR/P025064/1) and The Global Challenges Research 70 Fund (Wellcome Trust Grant 206/296/Z/17/Z).

The LEAP Process: Streamlining the Development of Long-Acting Products and Formulations for Infectious Diseases

Developing long-acting products and formulations for infectious diseases is a nontrivial undertaking that is frequently classified as high risk and low reward by the pharmaceutical industry. The Long-Acting/Extended Release Antiretroviral Research Resource Program (LEAP) was founded in 2015 with the support of the National Institutes of Health to encourage, promote, and accelerate the development of such products. Assessment methodology for any new proposal brought to this group is part of a framework-the LEAP Process-that includes a landscape analysis of what is currently available in the public domain. This is followed by in silico modeling and simulation offered as a service to the relevant scientific community. A variety of preclinical and clinical outcome metrics are applied to each new agent as part of a continuous feedback loop to improve product characteristics. This allows us to catalog knowledge gaps and barriers that can be addressed by engaged stakeholders. Results are communicated in scientific articles, reviews, and position papers. This undertaking serves to de-risk discovery, development, and implementation by bridging the gaps between academic, regulatory, and industrial investigators, and by engaging those in the community who will be the eventual users of these medicines. The LEAP Process has supported formulations now approved for human immunodeficiency virus, as well as products in clinical and preclinical development for tuberculosis and hepatitis viruses B and C.

Precision Medicine: Determination of Ribavirin Urinary Metabolites in Relation to Drug Adverse Effects in HCV Patients

The most commonly used antiviral treatment against hepatitis C virus is a combination of direct-acting antivirals (DAAs) and ribavirin (RBV), which leads to a shortened duration of therapy and a sustained virologic response until 98%. Nonetheless, several dose-related side effects of RBV could limit its applications. This study aims to measure the urinary concentration of RBV and its main metabolites in order to evaluate the drug metabolism ability of HCV patients and to evaluate the adverse effects, such as anemia, with respect to RBV metabolite levels. RBV and its proactive and inactive metabolites were identified and quantified in the urine of 17 HCV males with severe liver fibrosis using proton nuclear magnetic resonance (¹H-NMR) at the fourth week (TW4) and at the twelfth week of treatment (EOT). Four prodrug urinary metabolites, including RBV, were identified and three of them were quantified. At both the TW4 and EOT stages, six HCV patients were found to maintain high concentrations of RBV, while another six patients maintained a high level of RBV proactive metabolites, likely due to nucleosidase activity. Furthermore, a negative correlation between the reduction in hemoglobin (Hb) and proactive forms was observed, according to RBV-triphosphate accumulation causing the hemolysis. These findings represent a proof of concept regarding tailoring the drug dose in relation to the specific metabolic ability of the individual, as expected by the precision medicine approach.

Evaluation of the genetic toxicity of sofosbuvir and simeprevir with and without ribavirin in a human-derived liver cell line

Direct-acting antivirals have revolutionized the treatment of chronic hepatitis C. Sofosbuvir and simeprevir are prescribed worldwide. However, there is a scarcity of information regarding their genotoxicity. Therefore, the present study assessed the cytotoxic and genotoxic effects of sofosbuvir and simeprevir, alone and combined with ribavirin. HepG2 cells were analyzed using the in vitro cytokinesis-block micronucleus cytome assay. Cells were treated for 24 h with sofosbuvir (0.011-1.511 mM), simeprevir (0.156-5.0 µM), and their combinations with ribavirin (0.250-4.0 mM). No significant differences were observed in the nuclear division cytotoxicity index, reflecting the absence of cytotoxic effects associated to sofosbuvir. However, the highest concentration of simeprevir showed a significant difference for the nuclear division cytotoxicity index. Moreover, significant results were observed for nuclear division cytotoxicity index in two combinations of sofosbuvir plus ribavirin and only in the highest combination of simeprevir plus ribavirin. Additionally, our results showed that sofosbuvir did not increase the frequency of chromosomal damage, but simeprevir significantly increased the frequency of micronuclei at the highest concentrations. The combination index demonstrated that both sofosbuvir and simeprevir produced antagonism to the genotoxic effects of ribavirin. In conclusion, our results showed that simeprevir, but not sofosbuvir, has genotoxic effects in HepG2 cells.

Ineffective Absorption? Failure of Direct-Acting Therapy for Chronic Hepatitis C in Cirrhotic Patients With Roux-en-Y Gastric Bypass

In this era of direct-acting antiviral (DAA) therapy for chronic hepatitis C virus (HCV) infection, treated patients have extremely high rates of sustained virologic response to short courses of therapy regardless of stage of fibrosis. Treatment failure is uncommon and often attributed to medication noncompliance or viral resistance to drug. This report describes 2 Child-Pugh-A cirrhotic patients who failed to clear HCV in response to therapy with DAAs. Each patient had Roux-en-Y gastric bypass (RYGB) surgery preceding DAA therapy. RYGB may create multiple barriers to adequate DAA absorption as a result of changes in gastrointestinal physiology. Treatment monitoring and duration should be carefully considered in this unique patient population.

Viral Hepatitis C Therapy: Pharmacokinetic and Pharmacodynamic Considerations: A 2019 Update

It has been estimated by the World Health Organization (WHO) that over 71 million people were infected with the hepatitis C virus (HCV) in 2015. Since then, a number of highly effective direct-acting antiviral (DAA) regimens have been licensed for the treatment of chronic HCV infection: sofosbuvir/daclatasvir, sofosbuvir/ledipasvir, elbasvir/grazoprevir, sofosbuvir/velpatasvir, glecaprevir/pibrentasvir, and sofosbuvir/velpatasvir/voxilaprevir. With these treatment regimens, almost all chronic HCV-infected patients, even including prior DAA failures, can be treated effectively and safely. It is therefore likely that further development of DAAs will be limited. In this descriptive review we provide an overview of the clinical pharmacokinetic characteristics of currently available DAAs by describing their absorption, distribution, metabolism, and excretion. Potential drug-drug interactions with the DAAs are briefly discussed. Furthermore, we summarize what is known about the pharmacodynamics of the DAAs in terms of efficacy and safety. We briefly discuss the relationship between the pharmacokinetics of the DAAs and efficacy or toxicity in special populations, such as hard to cure patients and patients with liver cirrhosis, liver transplantation, renal impairment, hepatitis B virus or HIV co-infection, bleeding disorders, and children. The aim of this overview is to educate/update prescribers and pharmacists so that they are able to safely and effectively treat HCV-infected patients even in the presence of underlying co-infections or co-morbidities.

Pharmacogenetics of the anti-HCV drug sofosbuvir: a preliminary study

Background

Sofosbuvir is a potent nucleotide HCV NS5B polymerase inhibitor that is also a P-glycoprotein (encoded by the ABCB1 gene) and breast cancer resistance protein (encoded by the ABCG2 gene) substrate. Concerning previous anti-HCV therapies, pharmacogenetics had a significant impact, particularly considering the association of interleukin28B polymorphisms with dual-therapy (ribavirin + pegylated IFN) outcomes.

Objectives

In this work, we investigated the association between sofosbuvir and its prevalent metabolite (GS-331007) plasma concentrations at 1 month of therapy and genetic variants (SNPs) in genes encoding transporters and nuclear factors (ABCB1, ABCG2 and HNF4α) related to sofosbuvir transport.

Patients and methods

Allelic discrimination was performed through real-time PCR, whereas plasma concentrations were evaluated through liquid chromatography. One hundred and thirteen patients were enrolled.

Results

Sofosbuvir concentrations were below the limit of quantification since the drug was converted into its GS-331007 metabolite. ABCB1 2677 G>T (P = 0.044) and HNF4α 975 C>G (P = 0.049) SNPs were associated with GS-331007 metabolite plasma concentrations. In linear multivariate analysis, liver stiffness, insulin resistance, baseline haemoglobin and haematocrit and SNPs in the ABCB1 gene (3435 CT/TT and 1236 TT genotypes) were significant predictors of GS-331007 concentrations. Furthermore, we performed sub-analyses considering the anti-HCV concomitant drug and HCV genotype, identifying specific polymorphisms associated with GS-331007 plasma concentrations: ABCB1 3435 C>T and HNF4α975 C>G in patients treated with daclatasvir, ABCB1 2677 G>T with ledipasvir and ABCB1 3435 C>T, ABCB1 2677 G>T, ABCG2 421 C>A and ABCG2 1194 + 928 C>A with ribavirin.

Conclusions

In this study we suggested sofosbuvir GS-331007 metabolite plasma levels were affected by variants in the ABCB1 and HNFα genes.

Drug Interchangeability of Generic and Brand Products of Fixed Dose Combination Tablets of Sofosbuvir and Ledipasvir (400/90 mg): Employment of Reference Scaled Average Bioequivalence Study on Healthy Egyptian Volunteers

BACKGROUND AND OBJECTIVES

The purpose of this study was to apply the reference-scaled average bioequivalence (RSABE) approach to evaluate the bioequivalence and to investigate the pharmacokinetic properties of two formulations of fixed dose combination (FDC) tablet of sofosbuvir (SOF) and ledipasvir (LED) (400/90 mg) in 36 healthy Egyptian volunteers.

METHODS

The study was performed in single-dose, randomized-sequence, open-label, reference-replicated, 3-period crossover design (RTR, TRR, RRT), with a washout period of 2 weeks. A rapid and simple LC-MS/MS method was developed and validated for the simultaneous estimation of SOF and LED using eplerenone as an internal standard (IS).

RESULTS

The results showed that the 90% confidence intervals (CIs) for natural log-transformed ratios of C_max, AUC_last and AUC_∞ of SOF (89.95-115.31, 98.77-109.75 and 98.79-109.75) were within the RSABE acceptance limits. The 90% CIs for natural log-transformed ratios of C_max and AUC_last of LED (87.33-115.15 and 83.82-112.26) were within the FDA bioequivalence limits (80.00-125.00). In addition, the in vitro dissolution study was done and both formulations released > 85% of drug within 15 min in the proposed dissolution medium.

CONCLUSIONS

In conclusion, bioequivalence between the two fixed-dose combination products was demonstrated for both active ingredients.

Pharmacogenetics and the treatment of HIV-/HCV-coinfected patients

This review will summarize the role of pharmacogenetics in the natural history of hepatitis C, particularly in patients with HIV/HCV and will take the perspective of pharmacogenetics and its influence on the response to antiviral therapy and the susceptibility to develop adverse effects. This review will also devote a section to host genetics in other clinical situations, such as disease progression and acute HCV infection, which may determine whether treatment of HIV-/HCV-coinfected patients is implemented or deferred.

Sofosbuvir-based antiviral therapy in hepatitis C virus patients with severe renal failure

Background

Chronic hepatitis C virus (HCV) infection is the most common chronic liver disease in patients with end-stage renal disease (ESRD). Over the last few years, second-generation direct-acting antivirals have been revolutionary in the treatment of hepatitis C, and sofosbuvir (SOF) is the backbone of most modern treatment strategies. Since SOF is eliminated through the kidney, the aim of this multicentre retrospective study was to assess its antiviral efficacy and safety in HCV-infected patients with severe renal failure [including haemodialysis (HD) patients].

Methods

Fifty patients (36 males, mean age ± standard deviation 60.5 ± 7.5 years) with chronic HCV infection (G1: 28/56%, cirrhosis: 27/54%) and severe renal failure [i.e. MDRD estimated glomerular filtration rate (eGFR) <35 mL/min], including 35 on HD, were enrolled. Antiviral treatment consisted of SOF/ribavirin (RBV) (n = 7), SOF/RBV/pegylated interferon (n = 2), SOF/daclatasvir ± RBV (n = 30) or SOF/simeprevir ± RBV (n = 11) for 12 or 24 weeks. A reduced dose of SOF (400 mg three times a week or 400 mg every other day) was given to all HD patients. Initial dose of RBV (n = 12) ranged from 400 to 4200 mg/week.

Results

On an intent-to-treat-based analysis, sustained virological response rate was 86% at 12 weeks. During therapy, haemoglobin levels were not significantly modified, but recombinant erythropoietin (rEPO) dose significantly increased in patients treated with RBV. Two patients (4%) required blood transfusion. No patient had treatment discontinuation due to side effects. Dose of RBV was reduced in two patients (16.7%) during antiviral therapy. Dose of SOF was reduced in two non-HD patients because of side effects. In non-HD patients, median eGFR was not significantly modified during treatment.

Conclusions

Our results strongly suggest that SOF-based antiviral therapy, with a reduced dose of SOF, is safe and effective for the treatment of HCV patients with ESRD, including HD patients.

Grazoprevir plus elbasvir in HCV genotype-1 or -4 infected patients with stage 4/5 severe chronic kidney disease is safe and effective

Patients with advanced chronic kidney disease who receive direct-acting antiviral drugs require special consideration regarding comorbid conditions. Here we assessed the efficacy and safety of grazoprevir plus elbasvir in 93 patients infected with HCV genotype 1 or 4 and with advanced chronic kidney disease in a non-randomized, multicenter, nationwide observational survey. Twenty patients with HCV genotype 1a, 51 patients with 1b, four unclassified genotype 1, 17 with genotype 4 and one with genotype 6 received grazoprevir plus elbasvir (100/50 mg) once daily. All patients had severe chronic kidney disease with 70 patients stage G5, including patients on hemodialysis (74.2%), and 23 were stage G4 chronic kidney disease. Severe liver disease (Metavir F3/F4) was found in 33 patients. A sustained virologic response 12 weeks after the end of therapy was achieved in 87 of 90 patients. Two patients had a virologic breakthrough and one had a relapse after treatment withdrawal. Most patients received many concomitant medications (mean 7.7) related to comorbid conditions. Serious adverse events occurred in six patients, including three deaths while on grazoprevir plus elbasvir, not related to this therapy. Thus, once-daily grazoprevir plus elbasvir was highly effective with a low rate of adverse events in this advanced chronic kidney disease difficult-to-treat population with an HCV genotype 1 or 4 infection.

Prevalence of HCV Infection in Adults with Congenital Heart Disease and Treatment with Direct Antiviral Agents

OBJECTIVES

Hepatitis C virus (HCV) infection affects >3% of the US population, which over time can lead to cirrhosis and hepatocellular carcinoma. The lack of a reliable screening method for HCV before 1992 resulted in a higher prevalence of the virus in adults with congenital heart disease who underwent corrective surgery that required blood transfusions. Direct-acting antiviral agents such as sofosbuvir/ledipasvir have significantly increased the efficacy of HCV therapy, although use of these medications in adults with congenital heart disease has not been described.

METHODS

Ours was a retrospective study of 188 adults with congenital heart conditions who had cardiac surgery before 1992. These patients were screened for HCV using HCV antibody followed by HCV RNA if the screening test was positive.

RESULTS

Of the 188 adults, 116 (43% male patients, 24-70 years) were screened for the HCV antibody, demonstrating that 104 individuals were negative and 12 subjects were positive for the virus. Subsequently, further testing for the presence of HCV demonstrated 11 of 12 were infected, with an overall prevalence of 9.5%. Five individuals chose to be treated with sofosbuvir/ledipasvir and 5 of 5 have successfully cleared the virus and are considered cured.

CONCLUSIONS

Adults with congenital heart disease who underwent cardiac surgery before 1992 warrant being screened for HCV, and, if testing positive, may be considered for therapy using direct-acting antiviral agents with close monitoring for cardiac complications.

Vitamin D pathway genetic variants are able to influence sofosbuvir and its main metabolite pharmacokinetics in HCV mono-infected patients

Vitamin D levels and genetic variants were associated with drug outcome/toxicity and concentrations. The plasma exposure of GS-331007, the main sofosbuvir metabolite, has been related to SVR. We evaluated the impact of polymorphisms in genes (CYP27B1, CYP24A1, VDBP and VDR) related to vitamin D pathway on sofosbuvir and GS-331007 plasma levels in HCV mono-infected patients at one month of treatment. Polymorphisms were investigated through real-time PCR; drug plasma quantification was performed through a UHPLC-MS/MS method. GS-331007 levels were associated with CYP24A1rs2248359 and VDRCdx2 variants in all the analyzed patients and linear regression analysis showed that sex, body mass index, HCV genotype, baseline estimated glomerular filtration rate, VDRCdx2AG/GG and CYP27B1-1260TT genotypes significantly predict concentrations. We performed sub-analyses considering the HCV genotype and the concomitant drug, identifying polymorphisms associated with GS-331007 concentrations. This is the first study focusing on vitamin D pathway gene variants and DAAs concentrations, but further studies are required.

Chromosomal instability and cytotoxicity induced by ribavirin: comparative analysis in cell lines with different drug-metabolizing profiles

Ribavirin is an important component of the treatment for hepatitis C virus (HCV) infection and, in combination with the new direct-acting antiviral (DAA) agents, comprises the major current therapeutic regimens. This study evaluated the cytotoxicity and chromosomal instability induced by ribavirin using the in vitro cytokinesis-block micronucleus cytome (CBMN-Cyt) assay in two cell lines with different expression levels of drug-metabolizing enzymes: human hepatocellular carcinoma cells (HepG2) and Chinese hamster ovary (CHO-K1) cells. HepG2 cells were treated with nine concentrations (from 15.3 μg/ml to 3.9 mg/ml) and CHO-K1 cells were exposed to eight concentrations (from 15.3 μg/ml to 1.9 mg/ml) of ribavirin for 24 h. Ribavirin inhibited cell proliferation in both cell lines, but at different concentrations: 3.9 mg/ml in HepG2 and 244.2 μg/ml in CHO-K1 cells. No significant differences were observed regarding aspects of cell death in HepG2 and CHO-K1 cells, reflecting the absence of cytotoxic effects associated to ribavirin. Ribavirin did not increase the frequency of nucleoplasmic bridges (NPBs) and nuclear bud (NBUD). However, when compared to the negative control, a significant increase in micronuclei (MNi) frequency was observed in both cell lines. However, chromosomal instability was induced by higher concentrations of ribavirin in HepG2 cells (from 61.1 to 976.8 μg/ml), compared with CHO-K1 cells (15.3 and 30.5 μg/ml). These results demonstrate the potential of ribavirin to promote chromosomal instability, and suggest that cells with different expressions of drug-metabolizing enzymes show different susceptibility to ribavirin effects.

Pharmacokinetics and Tolerability of Anti-Hepatitis C Virus Treatment with Ombitasvir, Paritaprevir, Ritonavir, with or Without Dasabuvir, in Subjects with Renal Impairment

BACKGROUND

The direct-acting antiviral agent (DAA) combination of ombitasvir and paritaprevir (administered with ritonavir) with (3D regimen) or without (2D regimen) dasabuvir has shown very high efficacy rates in the treatment of chronic hepatitis C virus (HCV) infection. Renal impairment, a common comorbidity in patients with chronic HCV infection, can influence the pharmacokinetics of antiviral agents and hence their efficacy and safety profiles.

OBJECTIVE

The aim of this study was to evaluate the influence of renal impairment on the pharmacokinetics and tolerability of the 3D and 2D regimens.

METHODS

Overall, 24 subjects, six in each of four renal function groups (normal, mild, moderate, and severe), received a single dose of the 3D and 2D regimens in separate dosing periods. Plasma and urine were analyzed to assess the effect of renal impairment on drug exposure.

RESULTS

DAA exposures changed by up to 21, 37, and 50 % in subjects with mild, moderate, and severe renal impairment, respectively, versus subjects with normal renal function. Ritonavir exposure increased with the degree of renal impairment (maximum 114 %). The half-lives of DAAs and ritonavir in subjects with renal impairment were generally comparable with those in healthy subjects. No safety or tolerability concerns arose in this study.

CONCLUSION

The 3D and 2D regimens do not require dose adjustment for patients with HCV infection and concomitant renal impairment.

Defining the optimal dose of rifapentine for pulmonary tuberculosis: Exposure-response relations from two phase II clinical trials

Rifapentine is a highly active antituberculosis antibiotic with treatment-shortening potential; however, exposure-response relations and the dose needed for maximal bactericidal activity have not been established. We used pharmacokinetic/pharmacodynamic data from 657 adults with pulmonary tuberculosis participating in treatment trials to compare rifapentine (n = 405) with rifampin (n = 252) as part of intensive-phase therapy. Population pharmacokinetic/pharmacodynamic analyses were performed with nonlinear mixed-effects modeling. Time to stable culture conversion of sputum to negative was determined in cultures obtained over 4 months of therapy. Rifapentine exposures were lower in participants who were coinfected with human immunodeficiency virus, black, male, or fasting when taking drug. Rifapentine exposure, large lung cavity size, and geographic region were independently associated with time to culture conversion in liquid media. Maximal treatment efficacy is likely achieved with rifapentine at 1,200 mg daily. Patients with large lung cavities appear less responsive to treatment, even at high rifapentine doses.

Managing drug-drug interactions with new direct-acting antiviral agents in chronic hepatitis C

Several direct-acting antiviral agents (DAAs) have marketing authorization in Europe and in the USA and have changed the landscape of hepatitis C treatment: each DAA has its own metabolism and drug-drug interactions (DDIs), and managing them is a challenge. To compile the pharmacokinetics and DDI data of the new DAA and to provide a guide for management of DDI. An indexed MEDLINE search was conducted using the keywords: DAA, hepatitis C, simeprevir, daclatasvir, ledipasvir, sofosbuvir, 3D regimen (paritaprevir/ritonavir, ombitasvir, dasabuvir), DDI and pharmacokinetics. Data were also collected from hepatology, and infectious disease and clinical pharmacology conferences abstracts. Food can play a role in the absorption of DAAs. Most of the interactions are linked to metabolism (cytochrome P450-3 A4 [CYP3A4]) or hepatic and/or intestinal transporters (organic anion-transporting polypeptide and P-glycoprotein [P-gp]). To a lesser extent other pathways can be involved such as breast cancer resistance protein transporter or UDP-glucuronosyltransferase metabolism. DDI are more likely to occur with 3D regimen, daclatasvir, simeprevir and ledipasvir, as they are all both substrates and inhibitors of P-gp and/or CYP3A4, than with sofosbuvir. They can increase concentrations of coadministered drugs and their concentrations may be influenced by P-gp or CYP3A4 inducers or inhibitors. Overdosage or low dosage can be encountered with potent inducers or inhibitors of CYP3A4 or drugs with a narrow therapeutic range. The key to interpret DDI data is a good understanding of the pharmacokinetic profiles of the drugs involved. Their ability to inhibit CYP450-3A4 and transporters (hepatic and/or intestinal) can have significant clinical consequences.

Drug-Drug Interactions with the NS3/4A Protease Inhibitor Simeprevir

Simeprevir is an NS3/4A protease inhibitor approved for the treatment of hepatitis C infection, as a component of combination therapy. Simeprevir is metabolized by the cytochrome P450 (CYP) system, primarily CYP3A, and is a substrate for several drug transporters, including the organic anion transporting polypeptides (OATPs). It is susceptible to metabolic drug–drug interactions with drugs that are moderate or strong CYP3A inhibitors (e.g. ritonavir and erythromycin) or CYP3A inducers (e.g. rifampin and efavirenz); coadministration of these drugs may increase or decrease plasma concentrations of simeprevir, respectively, and should be avoided. Clinical studies have shown that simeprevir is a mild inhibitor of CYP1A2 and intestinal CYP3A but does not inhibit hepatic CYP3A. The effects of simeprevir on these enzymes are of clinical relevance only for narrow-therapeutic-index drugs that are metabolized solely by these enzymes (e.g. oral midazolam). Simeprevir does not have a clinically relevant effect on the pharmacokinetics of rilpivirine, tacrolimus, oral contraceptives and several other drugs metabolized by CYP enzymes. Simeprevir is a substrate and inhibitor of the transporters P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and OATP1B1/3. Cyclosporine is an inhibitor of OATP1B1/3, BCRP and P-gp, and a mild inhibitor of CYP3A; cyclosporine causes a significant increase in simeprevir plasma concentrations, and coadministration is not recommended. Clinical studies have demonstrated increases in coadministered drug concentrations for drugs that are substrates of the OATP1B1/3, BRCP (e.g. rosuvastatin) and P-gp (e.g. digoxin) transporters; these drugs should be administered with dose titration and or/close monitoring.

Evaluation of the Pharmacokinetics and Renal Excretion of Simeprevir in Subjects with Renal Impairment

BACKGROUND

Simeprevir is a N3/4 protease inhibitor approved for the treatment of hepatitis C virus (HCV) infection. HCV prevalence is higher in patients with chronic kidney disease compared with the general population; safe and efficacious therapies in renal impairment are needed.

OBJECTIVES

To evaluate simeprevir renal excretion in healthy subjects and to compare the simeprevir steady-state pharmacokinetics between subjects with severe renal impairment and healthy subjects.

METHODS

In the mass balance study, healthy adults received a single 200-mg dose of (14)C-simeprevir; radioactivity in the urine and feces was quantified until concentrations were <2% of the administered dose and seven or more stools were produced. In the pharmacokinetic study, non-HCV-infected adults with severe renal impairment (estimated glomerular filtration rate ≤29 mL/min/1.73 m(2)) and matched healthy subjects (estimated glomerular filtration rate ≥80 mL/min/1.73 m(2)) received 150 mg simeprevir for 7 days. Pharmacokinetic analysis was performed post-dose on Day 7.

RESULTS

(14)C-simeprevir recovery from the urine was low (0.009-0.138% of total dose). The minimum plasma concentration, maximum plasma concentration, and area under the plasma concentration-time curve at 24 h were 71, 34, and 62% higher, respectively, in subjects with severe renal impairment compared with healthy subjects. The mean fraction of simeprevir unbound to protein was <0.0001 (all subjects). Most adverse events were grade I or II; one subject with renal impairment who was receiving fenofibrate presented with grade 3 rhabdomyolysis.

CONCLUSIONS

Simeprevir plasma concentrations were mildly elevated in subjects with severe renal impairment. The results suggest that simeprevir may be administered without dose adjustment in patients with renal impairment.

A UHPLC-MS/MS method for the quantification of direct antiviral agents simeprevir, daclatasvir, ledipasvir, sofosbuvir/GS-331007, dasabuvir, ombitasvir and paritaprevir, together with ritonavir, in human plasma

To date, the new standard for treatment of chronic hepatitis C is based on the administration of novel direct acting antivirals. Among these, sofosbuvir, simeprevir, daclatasvir, ledipasvir, dasabuvir, ombitasvir and paritaprevir already entered the clinical use. Anyway, since few pharmacokinetic studies have been conducted on these drugs in a "real life" context poor knowledge is available about their optimal therapeutic range. Without this background, therapeutic drug monitoring is not applicable for treatment optimization. Up to now, a few methods are reported to quantify these drugs in human plasma, and none of them in a simultaneous way. The aim of this work was to develop and validate a simple, fast and cheap, but still reliable UHPLC-MS/MS method for the quantification of these drugs, feasible for a clinical routine use. Solid phase extraction was performed using HLB C18 96-well plates. Chromatographic separation was performed on a BEH C18 1.7μm, 2.1mm×50mm column, settled at 50°C, with a gradient run of two mobile phases: ammonium acetate 5mM (pH 9.5) and acetonitrile, with a flow rate of 0.4mL/min for 5min. Tandem-mass detection was carried out in positive electrospray ionization mode. Both inter and intraday imprecision and inaccuracy were below 15%, as required by FDA guidelines, while both recoveries and matrix effects resulted within the acceptance criteria. The method was tested on 80 patients samples with good performance. Being robust, simple and fast and requiring a low plasma volume, this method resulted eligible for a clinical routine use.

Human immunodeficiency virus and liver disease: An update

Human immunodeficiency viral (HIV) infection affects approximately 1.2 million persons in the United States and 35 million worldwide. Progression to advanced liver disease remains a leading cause of death among HIV-infected persons in the United States and elsewhere. Though mortality from HIV complications has been dramatically reduced wherever effective combination antiretroviral therapy is used, there has been little impact on liver-related mortality. Causes of liver disease in the setting of HIV infection include viral hepatitis, nonalcoholic fatty liver disease/nonalcoholic steatohepatitis, drug-associated toxicities, and other metabolic/genetic disorders which interact in an environment modulated by persistent immune activation and altered cytokine display.

CONCLUSION

Despite significant advances in treatment of hepatitis C virus and suppression of hepatitis B virus, treatment and management principles for liver disease in HIV-infected patients remain challenging; limited resources, fragmented health care, and high levels of injection drug use, alcohol use, and depression remain relevant issues in the HIV-infected patient.

Mechanisms of Virologic Failure with Direct-Acting Antivirals in Hepatitis C and Strategies for Retreatment

The current standard of care for hepatitis C therapy is the combination of direct-acting antiviral (DAA) agents. These orally administered medications target the viral proteins and halt the hepatitis C virus lifecycle. Despite high cure rates with these novel drugs, virologic failure with DAAs are of mounting concern as real-world sustained virologic response 12 rates seem lower than expected. The mechanisms of virologic failure to DAAs are likely multifactorial, including baseline resistance variants, the efficacy of the agents used, and host factors. Salvage therapy for DAA virologic failures is an area of emerging research.

Natural history and treatment of HCV/HIV coinfection: Is it time to change paradigms?

Evidence over the past decades have shown that HIV/HCV coinfected patients did not respond as well to HCV therapy as HCV mono-infected patients. However, these paradigms are being recently reassessed with the improvements of care for HIV and HCV patients. This article reviews these original paradigms and how the new data is impacting upon them. Treatment efficacy now appears comparable for HIV/HCV coinfected and HCV mono-infected patients, while liver fibrosis progression is increasingly similar in optimally managed patients. Additional importance of therapy is directed to drug-drug interactions and the impact of HCV reinfection, as well as the possibility of transmitted drug resistance.

Discovery of Imidazo[1,2-α][1,8]naphthyridine Derivatives as Potential HCV Entry Inhibitor

RO8191 represents a newly discovered small-molecule IFN-like agent that displays potent anti-HCV activity. With it as lead, a series of compounds bearing an imidazo[1,2-α][1,8]naphthyridine core and an amide bond-linked side chain were designed and synthesized. These compounds were evaluated on HCV cell culture system (HCVcc-hRluc-JFH1), and some of them exhibited remarkable anti-HCV activity (EC50 = 0.017-0.159 μM) and low toxicity (CC50 > 25 μM). Moreover, it was revealed that these newly identified anti-HCV agents exert their antiviral effect through a distinct mechanism of action from that of RO8191 by targeting the viral entry process. Thus, our study provides a starting point for the development of potential HCV entry inhibitor.

Hepatic decompensation with sofosbuvir plus simeprevir in a patient with Child-Pugh B compensated cirrhosis

A 75-year-old male with compensated Child-Pugh B cirrhosis initiated sofosbuvir plus simeprevir, and developed hepatic decompensation and died a few days thereafter. High exposure to simeprevir leading to hepatotoxicity most likely explained this fatal outcome. This observation, along with similar cases recently reported in the literature, should raise awareness of the potential for decompensation in patients with advanced cirrhosis treated with simeprevir.

Presentation and complications associated with cirrhosis of the liver

OBJECTIVE

To provide an understanding of the detrimental impact of cirrhosis and its complications, strengths and weaknesses of current treatment options for the management of these complications, and new developments in this rapidly changing field.

RESEARCH DESIGN AND METHODS

Relevant publications were identified via PubMed and Cochrane databases, with additional references obtained by reviewing bibliographies from selected articles.

RESULTS

Cirrhosis, a progressive liver disease, is characterized by fibrosis caused by chronic liver injury. Liver fibrosis impairs hepatic function and causes structural changes that result in portal hypertension. Most patients with cirrhosis remain asymptomatic until they develop decompensated cirrhosis. At this stage, patients experience complications associated with portal hypertension (i.e., the abnormal increase in portal vein pressure), including ascites, spontaneous bacterial peritonitis (SBP), hepatic encephalopathy (HE), hepatorenal syndrome, portopulmonary hypertension, or variceal bleeding. In addition, intestinal microbial translocation in patients with cirrhosis might also cause SBP and HE. Because the survival rate for patients with cirrhosis substantially decreases once complications develop, the key goals in treating patients with cirrhosis include both managing the underlying liver disease and preventing and treating related complications. In patients with compensated cirrhosis, the management strategy is to prevent variceal bleeding and other complications that can lead to decompensated cirrhosis. Patients with decompensated cirrhosis are typically referred for liver transplantation, and the main focus of pre-transplant management is to eliminate the cause of cirrhosis (e.g., excess alcohol consumption, hepatitis virus) and prevent the recurrence of each decompensating complication.

CONCLUSIONS

Although substantial progress has been made to prevent the complications and mortality associated with cirrhosis, liver transplantation in combination with resolution of the etiology of cirrhosis remains the only curative option for most patients. Emerging therapies such as anti-fibrotic agents hold promise in potentially halting or reversing the progression of cirrhosis, even in patients with decompensated cirrhosis.

Treatment of hepatitis C in difficult-to-treat patients

Interferon-free regimes are now the treatment of choice for patients with chronic hepatitis C; previously patients who were 'difficult-to-treat' using interferon-containing treatments can now safely be treated with such therapies. More than 90% of patients infected with HCV genotype 1 or 4, compensated cirrhosis, or who have had liver transplantation, can be cured with the use of sofosbuvir combined with simeprevir, daclatasvir or ledipasvir, or by the combination of paritaprevir with ritonavir, ombitasvir and with or without dasabuvir. Addition of ribavirin seems to shorten treatment duration. However, the safety of these drugs is not fully explored in patients with decompensated cirrhosis (that is, those with Child-Pugh class C disease), and protease inhibitors should not be used in this group. The optimal use of interferon-free regimes in patients with renal failure or after kidney transplantation is currently being studied. However, new and improved drugs are needed to treat patients infected with HCV genotype 3. Unfortunately, the broad application of new HCV treatments is limited by their high costs. In this Review, I discuss the treatment of patients with hepatitis C with compensated and decompensated cirrhosis, before and after orthotopic liver transplantation and in patients with impaired kidney function.

HIV and HCV Medications in End-Stage Renal Disease

Human immunodeficiency virus (HIV) infection and hepatitis C virus (HCV) infection affect populations worldwide. With the availability of over 35 Food and Drug Administration approved medications for treatment of HIV, the morbidity and mortality associated with HIV has greatly improved. On the other hand, treatment options for HCV have been limited until very recently. While the use of protease inhibitors (such as boceprevir and telaprevir) has become standard of care for treatment of hepatitis C in the general population, data for individuals with impaired kidney function, particularly those on dialysis, are extremely limited. Use of medications in dialysis patients can be challenging given the dose adjustments that must be made for renally cleared molecules, and potentially increased impact of adverse effects such as anemia. Recommendations for dosing of marketed therapies for HIV and HCV are reviewed.