The importance of drug-drug interactions in the DAA era

A Comprehensive Review of Antiviral Therapy for Hepatitis C: The Long Journey from Interferon to Pan-Genotypic Direct-Acting Antivirals (DAAs)

The treatment landscape for hepatitis C virus (HCV) infection has transformed over the past few decades, evolving from the limited efficacy of interferon (IFN) monotherapy to the highly successful pan-genotypic direct-acting antivirals (DAAs) used today. Initially, alpha-interferon monotherapy, introduced in the 1990s, was the standard treatment, yet it provided low sustained virological response (SVR) rates and caused significant adverse effects, limiting its utility. The development of pegylated interferon (peg-IFN) improved the pharmacokinetic profile of IFN, allowing for less frequent dosing and modestly improved response rates. When combined with ribavirin, peg-IFN achieved higher SVR rates, especially in non-genotype 1 HCV infections, but the combination also brought additional side effects, such as anemia and depression. The advent of the first-generation DAAs, such as telaprevir and boceprevir, marked a significant milestone. Combined with peg-IFN and ribavirin, these protease inhibitors boosted response rates in patients with genotype 1 HCV. However, high rates of adverse effects and drug resistance remained challenges. Second-generation DAAs, like sofosbuvir and ledipasvir, introduced IFN-free regimens with improved safety profiles and efficacy. The most recent advances are pan-genotypic DAAs, including glecaprevir-pibrentasvir and sofosbuvir-velpatasvir, which offer high SVR rates across all genotypes, shorter treatment durations, and fewer side effects. Current pan-genotypic regimens represent a cornerstone in HCV therapy, providing an accessible and effective solution globally.

Hepatitis C virus eradication in people living with human immunodeficiency virus: Where are we now?

Hepatitis C virus (HCV)/human immunodeficiency virus (HIV) co-infection still involves 2.3 million patients worldwide of the estimated 37.7 million living with HIV, according to World Health Organization. People living with HIV (PLWH) are six times greater affected by HCV, compared to HIV negative ones; the greater prevalence is encountered among people who inject drugs and men who have sex with men: the risk of HCV transmission through sexual contact in this setting can be increased by HIV infection. These patients experience a high rate of chronic hepatitis, which if left untreated progresses to end-stage liver disease and hepatocellular carcinoma (HCC) HIV infection increases the risk of mother to child vertical transmission of HCV. No vaccination against both infections is still available. There is an interplay between HIV and HCV infections. Treatment of HCV is nowadays based on direct acting antivirals (DAAs), HCV treatment plays a key role in limiting the progression of liver disease and reducing the risk of HCC development in mono- and coinfected individuals, especially when used at an early stage of fibrosis, reducing liver disease mortality and morbidity. Since the sustained virological response at week 12 rates were observed in PLWH after HCV eradication, the AASLD has revised its simplified HCV treatment algorithm to also include individuals living with HIV. HCV eradication can determine dyslipidemia, since HCV promotes changes in serum lipid profiles and may influence lipid metabolism. In addition to these apparent detrimental effects on the lipid profile, the efficacy of DAA in HCV/HIV patients needs to be considered in light of its effects on glucose metabolism mediated by improvements in liver function. The aim of the present editorial is to describe the advancement in HCV treatment among PLWH.

Translation of In Vitro Transport Inhibition Studies to Clinical Drug-Drug Interactions for Glecaprevir and Pibrentasvir

Glecaprevir and pibrentasvir are oral direct-acting antiviral agents approved in combination for treatment of chronic hepatitis C viral infection. In vitro studies identified the combination as potentially clinically relevant inhibitors of the efflux transporters P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and the hepatic uptake transporters organic anion transporting polypeptide (OATP) 1B1 and OATP1B3. Glecaprevir inhibited P-gp, BCRP, OATP1B1, and OATP1B3 with IC50 values of 0.33, 2.3, 0.017, and 0.064 µM, respectively. Pibrentasvir inhibited P-gp, BCRP, and OATP1B1 with IC50 values of 0.036, 14, and 1.3 µM, respectively. Neither agent inhibited organic cation transporter (OCT) 1, OCT2, organic anion transporter (OAT) 1, OAT3, multidrug and toxin extrusion (MATE) 1, or MATE2K. Open-label phase 1 clinical drug-drug interaction studies were conducted in healthy subjects to evaluate interaction potential of glecaprevir/pibrentasvir and coadministered selective substrates for P-gp (digoxin, dabigatran etexilate, and sofosbuvir), BCRP (rosuvastatin and sofosbuvir), and OATP1B1/3 (pravastatin and rosuvastatin). The pharmacokinetic maximum plasma concentration (C max) and area under the concentration-time curve (AUC) parameters were evaluated for probe substrates alone and in combination with glecaprevir/pibrentasvir. The C max central values increased by 72%, 105%, 123%, 462%, and 66% for digoxin, dabigatran, pravastatin, rosuvastatin, and sofosbuvir, respectively, and the AUC central values increased by 48%, 138%, 130%, 115%, and 125% for digoxin, dabigatran, pravastatin, rosuvastatin, and sofosbuvir, respectively. Exposure of sofosbuvir metabolite GS-331007 (nucleoside analog) was similar with or without glecaprevir/pibrentasvir. The outcomes of the clinical drug-drug interaction studies confirmed clinically relevant inhibition of P-gp, BCRP, and OATP1B1/3, and were used to provide dosing guidance for the concomitant use of glecaprevir/pibrentasvir with relevant transporter substrates.

Treatment of Chronic Hepatitis C: Efficacy, Side Effects and Complications

Background

Chronic hepatitis C virus (HCV) infection can lead to liver cirrhosis and its complications. Viral eradication is essential to prevent disease progression and reduces liver-related mortality and morbidity. Since the availability of direct-acting antivirals (DAA), HCV treatment has changed significantly. Current treatment strategies for different groups of patients as well as potential risks and caveats will be discussed in this review.

Summary

Interferon-free (IFN-free) treatment not only shortens treatment duration, but also achieves high rates of viral clearance and is overall well tolerated. Genotype-restricted but also pangenotypic combinations are available. Usually two DAA of different drug classes are combined. For the majority of the patients, treatment duration ranges from 8 to 12 weeks. Liver and kidney function as well as prior treatment experience and potential drug-drug interactions influence substance choices and treatment duration. However, modern IFN-free treatment is not only safer, but also overall far more simplified and effective. Global HCV eradication might be an ambitious but not completely unrealistic goal to pursue.

Key Messages

IFN-free antiviral treatment is safe and well tolerated. Patients can be treated almost independently of liver function or concomitant disease. Viral eradication is associated with reduced morbidity and mortality and better quality of life.

Comorbidities, concomitant medications and potential drug-drug interactions with interferon-free direct-acting antiviral agents in hepatitis C patients in Taiwan

BACKGROUND

While direct-acting antivirals have been approved for treating hepatitis C, the guidelines highlight the importance of considering potential drug-drug interactions between DAAs and concomitant medications.

AIM

To assess comorbidity prevalence, concomitant medication use and potential drug-drug interactions between DAAs and concomitant medications for hepatitis C patients in Taiwan.

METHODS

This cross-sectional study enrolled 822 patients from May to August 2016 in Taiwan. Patient demographics, comorbidities and concomitant medications were evaluated by physician surveys.

RESULTS

A total of 709 (86.3%) patients had ≥1 comorbidity; the most prevalent comorbidity categories were diseases of the digestive system (40.1%), circulatory system (38.7%) and endocrine/nutritional/metabolic diseases (35.2%). Elderly patients had more comorbidities. A total of 622 (75.7%) patients received ≥1 concomitant medication; the average number of concomitant medications was 3.2. The most common concomitant medication classes were cardiovascular (34.4%), gastrointestinal (25.7%) and central nervous system drugs (22.7%). Among patients without cirrhosis or with compensated cirrhosis, contraindications were most prevalent with paritaprevir/ritonavir/ombitasvir plus dasabuvir, daclatasvir/asunaprevir and glecaprevir/pibrentasvir (13.3%, 6.0% and 5.4% respectively), and least prevalent with sofosbuvir, sofosbuvir/daclatasvir, sofosbuvir/ledipasvir and sofosbuvir/velpatasvir (0.8%, 1.3%, 1.4% and 2.1% respectively). Sofosbuvir-based regimens had no contraindications in patients with decompensated cirrhosis.

CONCLUSION

Our population represented an elderly demographic, with a high prevalence of comorbidities and widespread use of concomitant medications. The potential drug-drug interactions between these concomitant medications and DAA regimens differed, with the fewest potential interactions with sofosbuvir-based regimens.

Drug-Drug Interactions in Hepatitis Patients: Do these Interactions Matter in Clinical Perspectives?

INTRODUCTION AND AIM

Hepatitis patients usually present with comorbidities and polypharmacy which increases risk of potential drug-drug interactions (pDDIs). We explored frequency, levels, predictors, and clinical relevance of pDDIs in hospitalized hepatitis patients.

MATERIAL AND METHODS

Retrospective cohort study was used. Clinical profiles of 413 hepatitis patients were reviewed for pDDIs using Micromedex-DrugReax. Frequency, levels and clinical relevance of pDDIs were reported. Logistic regression analysis was used to calculate odds-ratios for predictors.

RESULTS

Of total 413 patients, pDDIs were reported in 55.2%. Major-pDDIs were found in 35% patients. Total 660 pDDIs were identified, of which, 304 (46%) were of major-severity and 299 (45%) of moderateseverity. Patient's profiles of top-10 major-pDDIs were presented with signs/symptoms such as fever, hepatomegaly, anorexia, jaundice, hypertension, tachycardia, bradycardia, & pedal edema; and abnormalities in labs such as electrolytes-level, alanine aminotransferase, blood urea nitrogen, bilirubin-level, & serum creatinine. Significant association was observed for the presence of pDDIs with > 9 prescribed medicines (p < 0.001), hospitalization of > 5 days (p = 0.03), and stroke as comorbidity (p = 0.05). Moreover, odds of exposure to major-pDDIs were significantly higher in patients taking > 9 prescribed medicines (p < 0.001), hospitalization of > 5 days (p = 0.002), and stroke as comorbidity (p = 0.002).

CONCLUSION

We observed hepatitis patients presented with a considerable number of clinically relevant pDDIs. Attention should be given to widespread major-pDDIs and their potential adverse outcomes. Clinically relevant parameters, such as labs and signs/symptoms should be monitored particularly in high risk patients having polypharmacy, prolong hospitalization, and stroke as comorbidity.

Real-world effectiveness of direct-acting antiviral agents for chronic hepatitis C in Taiwan: Real-world data

BACKGROUND/PURPOSE

Treatment of chronic hepatitis C (CHC) has entered a new era since the introduction of direct-acting antiviral agents (DAAs). Numerous clinical trials have shown that treatment response as well as tolerability of DAAs are superior to those of conventional therapy with pegylated interferon and ribavirin. However, the results of clinical trials may not be directly applied to real-world practice. Therefore our study tried to investigate the effectiveness of various DAA regimens in Taiwanese patients with chronic hepatitis C.

METHODS

We performed a retrospective study on 400 CHC patients. The primary endpoint was undetectable HCV RNA (an HCV RNA level of <25 IU/mL) at 12 weeks posttreatment (SVR12). The results were stratified by different DAAs and HCV genotypes.

RESULTS

Genotype 1b was the major genotype (297, 74.3%), followed by genotype 2 (65, 16.3%). The patients were treated according to HCV genotype, clinical practice and reimbursement guidelines. The SVR12 rates of 57 patients treated with sofosbuvir and ribavirin, 107 treated with ledipasvir/sofosbuvir with or without ribavirin, 60 treated with daclatasvir/asunaprevir with or without ribavirin, 129 treated with ombitasvir/paritaprevir/ritonavir/dasabuvir with or without ribavirin, 12 treated with sofosbuvir/daclatasvir with or without ribavirin, and 35 treated with elbasvir/grazoprevir were 98.2%, 97.2%, 85.0%, 97.7%, 100.0%, and 100.0%, respectively.

CONCLUSIONS

The overall SVR12 rates in our study were comparable with those in previous pivotal trials. DAAs are generally safe. The interaction of HBV and HCV during DAA therapy and the observation of de novo HCC development and HCC recurrence during or after DAAs warrants additional studies.

Clinical impact of pharmacokinetic interactions between the HCV protease inhibitor simeprevir and frequently used concomitant medications

AIMS

Direct-acting antiviral agents (DAAs) for the treatment of hepatitis C (HCV) can be associated with drug-drug interactions (DDIs) with concomitant medications. The practical clinical implications of such DDIs are poorly understood. We assessed the clinical impact of possible pharmacokinetic (PK) interactions between simeprevir and frequently prescribed concomitant medications.

METHODS

This post hoc analysis pooled data from nine studies which evaluated simeprevir (SMV)-based interferon-free HCV treatment. Three classes of frequently used concomitant medications of interest (CMOIs) were analysed [antihypertensive drugs (AHDs), anxiolytic drugs (AXDs) and lipid-lowering drugs (LLDs)] and categorized as amber or green according to their DDI potential with SMV (green: no DDIs; amber: potential/known PK interactions). Concomitant medications not recommended to be coadministered with SMV were not included. The composite primary endpoint was defined as the frequency of either discontinuation, interruption or dose modification of the CMOI during 12 weeks of SMV treatment.

RESULTS

Few patients met the composite endpoint in the various subgroups. Patients on amber CMOIs tended to experience CMOI modification more often (13.4-19.4%) than those on green CMOIs (3.1-10.8%). There was no difference in the frequency of adverse events between patients taking green and those taking amber CMOIs.

CONCLUSIONS

In this large pooled analysis, coadministration of the evaluated commonly prescribed medications with known or potential PK interactions with SMV was manageable and resulted in few adjustments of concomitant medications. Our method could serve as a blueprint for the evaluation of the impact of DDIs.

Drug-Drug Interactions Between Direct-Acting Antivirals and Psychoactive Medications

Treatment options for chronic hepatitis C virus (HCV) infection have drastically changed since the development and licensing of new potent direct-acting antivirals (DAAs). The majority of DAAs are extensively metabolized by liver enzymes and have the ability to influence cytochrome P450 (CYP) enzymes. Additionally, these DAAs are both substrates and inhibitors of drug transporters, which makes the DAAs both possible victims or perpetrators of drug–drug interactions (DDIs). There is a high prevalence of mental illnesses such as depression or psychosis in HCV-infected patients; therefore, psychoactive medications are frequently co-administered with DAAs. The majority of these psychoactive medications are also metabolized by CYP enzymes but remarkably little information is available on DDIs between psychoactive medications and DAAs. Hence, the aim of this review is to provide an overview of the interaction mechanisms between DAAs and psychoactive agents. In addition, we describe evidenced-based interactions between DAAs and psychoactive drugs and identify safe options for the simultaneous treatment of mental illnesses and chronic HCV infection.

Flavokawain A inhibits Cytochrome P450 in in vitro metabolic and inhibitory investigations

ETHNOPHARMACOLOGICAL RELEVANCE

Flavokawain A, the major chalcone in kava extracts, was served as beverages for informal social occasions and traditional ceremonials in most South Pacific islands. It exhibited strong antiproliferative and apoptotic effects against human prostate and urinary bladder cancer cells.

AIM OF THE STUDY

The current study was purposed to investigate the interaction between Flavokawain A and Cytochrome P450, including the inhibitory effects of Flavokawain A on predominant CYP450 isotypes and further clarified the inhibitory mechanism of FKA on CYP450 enzymes. Besides, study about identifying the key CYP450 isotypes responsible for the metabolism of FKA was also performed.

MATERIALS AND METHODS

In this study, probe-based assays with rat liver microsome system were used to characterize the inhibitory effects of FKA. Molecular docking study was performed to further explore the binding site of FKA on CYP450 isoforms. In addition, chemical inhibition experiments using specific inhibitors (a-naphthoflavone, quinidine, sulfamethoxazde, ketoconazole, omeprazole) were performed to clarify the individual CYP450 isoform that are responsible for the metabolism of FKA.

RESULTS

FKA showed significant inhibition on CYP1A2, CYP2D1, CYP2C6 and CYP3A2 activities with IC50 values of 102.23, 20.39, 69.95, 60.22μmol/L, respectively. The inhibition model was competitive, mixed-inhibition, uncompetitive, and noncompetitive for CYP1A2, CYP2D1, CYP2C6 and CYP3A2 enzymes. Molecular docking study indicated the ligand-binding conformation of FKA in the active site of CYP450 isoforms. The chemical inhibition experiments showed that the metabolic clearance rate of Flavokawain A decreased to 19.84%, 50.38%, and 67.02% of the control in the presence of ketoconazole, sulfamethoxazde and a-naphthoflavone.

CONCLUSION

The study showed that Flavokawain A has varying inhibitory effect on CYP450 enzymes and CYP3A2 was the principal CYP isoform contributing to the metabolism of Flavokawain A. Besides, CYP2C6 and CYP1A2 isoforms also play important roles in the metabolism of FKA. Our results provided a basis for better understanding the biotransformation of FKA and prediction of drug-drug interaction of FKA.

Effect of co-medications on paritaprevir, ritonavir, ombitasvir, dasabuvir and ribavirin pharmacokinetics: analysis of data from seven Phase II/III trials

BACKGROUND

The three drug direct-acting antiviral regimen (3D regimen) of ombitasvir, paritaprevir/ritonavir and dasabuvir, with and without ribavirin, was evaluated in one Phase II trial and six Phase III trials in over 2,300 HCV genotype-1-infected patients. Patients continued taking their protocol-permitted co-medications while receiving the 3D ± ribavirin regimen. The effects of the co-medications on exposures of the 3D regimen and ribavirin were examined.

METHODS

Population pharmacokinetic model-predicted steady-state area under the curve (AUC_24,ss) values were evaluated in the presence/absence of the co-medications. Interactions resulting in a greater than 50% reduction or 100% increase in an AUC_24,ss value were examined as covariates for an effect on apparent clearance (CL/F).

RESULTS

More than 1,200 co-medications belonging to 15 drug classes and/or 19 enzyme and transporter inhibitor and/or inducer categories were used concomitantly with the 3D regimen in the trials. Approximately 1,500 patients (65%) in Phase III trials received two or more co-medications from multiple drug classes or categories. No co-medication class/category decreased or increased ombitasvir, dasabuvir, ritonavir or ribavirin AUC_24,ss by more than half or twofold, respectively. Opioids, antipsychotics, anti-epileptics, antidiabetics and non-ethinyl estradiol-containing hormone replacement therapies appeared to have an effect (AUC_24,ss ratio ≤0.5 or ≥2.0) on paritaprevir exposures. However, when these classes were included in the paritaprevir population pharmacokinetic model, only opioids and antidiabetics had a statistically significant effect on CL/F, but with no clinically meaningful increase in exposures (≤55%).

CONCLUSIONS

No dose adjustment is necessary for the 3D ± ribavirin regimen when used with the co-medications included in this analysis as there were no clinically meaningful effects on exposures of the DAAs.

Review article: safety and tolerability of direct-acting anti-viral agents in the new era of hepatitis C therapy

BACKGROUND

Direct-acting anti-virals (DAAs) licensed to treat chronic HCV infection have revolutionised treatment algorithms by drastically mitigating side effects while enhancing efficacy relative to interferon-based therapy.

AIM

To review adverse events (AEs) uniquely associated with DAA therapy across a broad spectrum of patient populations.

METHODS

Searches of PubMed and FDA surveillance studies were undertaken to complete an exhaustive review. Search terms included 'DAAs', 'safety', and 'tolerability'.

RESULTS

While DAAs are remarkably well tolerated, they are accompanied by unique AEs. Simeprevir, an NS3/4A protease inhibitor, has been known, albeit infrequently, to cause mild hyperbilirubinemia and photosensitivity reactions; and paritaprevir boosted with ritonavir causes bilirubin and ALT elevations. Asunaprevir, another protease inhibitor, infrequently causes elevated transaminase levels. NS5A and NS5B inhibitors are well tolerated, although sofosbuvir is contraindicated in patients with severe renal impairment. Ribavirin co-administered in certain treatment regimens has been associated with cough, rash and haemolytic anaemia.

CONCLUSIONS

With the impending reality of a more tolerable interferon-sparing regimen, the future of DAA therapy offers shorter treatment duration, simplified disease management, and a patient-centred regimen. With advantages come drawbacks, including development of resistance to therapy and accessibility to this expensive treatment. DAA therapy continues to advance at a brisk pace with a promising trend for higher tolerability, even in difficult-to-treat subgroups such as those with cirrhosis, nonresponders to prior therapy, and transplant recipients. Subgroup-specific contraindications and safety-related limitations are active areas of research. Concerted research efforts and continuing advances lend hope to the goal of rendering HCV a routinely curable disease.

Drug-Drug Interaction of Omeprazole With the HCV Direct-Acting Antiviral Agents Paritaprevir/Ritonavir and Ombitasvir With and Without Dasabuvir

Paritaprevir (administered with low-dose ritonavir), ombitasvir, and dasabuvir are direct-acting antiviral agents administered as combination regimens for the treatment of chronic hepatitis C virus infection. Drug-drug interactions between 2D (ombitasvir/paritaprevir/ritonavir) or 3D (ombitasvir/paritaprevir/ritonavir and dasabuvir) regimens and omeprazole, a CYP2C19 substrate and acid-reducing agent, were evaluated in 24 healthy volunteers. Subjects received omeprazole (40 mg once daily) on day 1 and days 20-24 and the 2D or 3D regimen (ombitasvir/paritaprevir/ritonavir 25/150/100 mg once daily ± dasabuvir 250 mg twice daily) on days 6-24. Compared with omeprazole alone, coadministration with the 2D or 3D regimen decreased omeprazole geometric mean Cmax and AUCt values by 40% to 50%. Ombitasvir, dasabuvir, and ritonavir mean exposures showed <10% change, and paritaprevir mean exposures showed <20% change when the 2D or 3D regimen was administered with omeprazole compared with administration without omeprazole. Although no a priori dose adjustment is needed, a higher omeprazole dose should be considered if clinically indicated when coadministered with the 2D or 3D regimen. No dose adjustment is required for the 2D or 3D regimen when administered with omeprazole, other acid-reducing agents, or CYP2C19 inhibitors.

Evaluation of Hepatitis C Patients in the Direct-Acting Antiviral Era

Hepatitis C is a major worldwide cause of liver morbidity and mortality. A substantial proportion of infected patients will develop chronic disease, which may progress over decades to cirrhosis. This can lead to decompensation and hepatocellular carcinoma. With the advent of the direct-acting antivirals, hepatitis C has become increasingly curable with limited adverse events and a shorter duration of therapy. This review discusses the evaluation process of the hepatitis C patient in the direct-acting antiviral era, including screening, clinical evaluation, drug-drug interactions, treatment urgency, and counseling.

Dual antiviral therapy for HIV and hepatitis C - drug interactions and side effects

INTRODUCTION

Roughly 20% of HIV-positive persons worldwide are coinfected with hepatitis C virus (HCV). The recent advent of direct-acting antivirals (DAA) that cure most hepatitis C patients has attracted much attention. Knowledge on drug interactions between DAA and antiretrovirals (ARV) may allow maximizing antiviral efficacy while minimizing drug-related toxicities.

AREAS COVERED

We review the most frequent side effects and clinically significant drug interactions between DAA and ARV. We further discuss how they can be prevented and managed in HIV/HCV-coinfected patients.

EXPERT OPINION

The safety profile of current DAA and the most recently approved ARV is quite favorable. Interactions between DAA and ARV could be frequent in clinical practice. The most common drug interactions affect drug metabolism by inducing or inhibiting the cytochrome P450 system, leading to abnormal drug exposures. Throughout this mechanism HCV and HIV protease inhibitors interact, especially when co-formulated with ritonavir as a pharmacoenhancer, and non-nucleoside HCV and HIV polymerase inhibitors. In contrast, HIV and HCV nucleos(t)ide polymerase inhibitors, and most HCV NS5A inhibitors (i.e., ledipasvir) and HIV integrase inhibitors (i.e., dolutegravir), do not or only marginally affect CYP450, and therefore are free of significant drug interactions. Exposure to HIV and HCV nucleos(t)ide analogues (i.e., tenofovir and sofosbuvir, respectively) is subject to induction/inhibition of drug transporters (i.e., P-glycoprotein).

Drug-drug interaction profile of the all-oral anti-hepatitis C virus regimen of paritaprevir/ritonavir, ombitasvir, and dasabuvir

BACKGROUND & AIMS

Paritaprevir (administered with ritonavir, PTV/r), ombitasvir (OBV), and dasabuvir (DSV) are direct-acting antiviral agents (DAAs) for the treatment of chronic hepatitis C virus (HCV) infection. Thirteen studies were conducted to characterize drug-drug interactions for the 3D regimen of OBV, PTV/r, and DSV and various medications in healthy volunteers to inform dosing recommendations in HCV-infected patients.

METHODS

Mechanism-based drug-drug interactions were evaluated for gemfibrozil, ketoconazole, carbamazepine, warfarin, omeprazole, digoxin, pravastatin, and rosuvastatin. Drug-drug interactions with medications commonly used in HCV-infected patients were evaluated for amlodipine, furosemide, alprazolam, zolpidem, duloxetine, escitalopram, methadone, buprenorphine/naloxone, and oral contraceptives. Ratios of geometric means with 90% confidence intervals for maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) were used to determine the magnitude of interaction.

RESULTS

Coadministration with the 3D regimen of OBV, PTV/r, and DSV resulted in a <2-fold change in mean Cmax and AUC for most medications and the DAAs, indicating minimal to modest interactions. Carbamazepine decreased PTV, ritonavir, and DSV exposures substantially, while gemfibrozil increased DSV exposures substantially. Although coadministration with ethinyl estradiol-containing contraceptives resulted in elevated alanine aminotransferase levels, coadministration with a progestin-only contraceptive did not.

CONCLUSIONS

The majority of medications can be coadministered with the 3D regimen of OBV, PTV/r, and DSV without dose adjustment, or with clinical monitoring or dose adjustment. Although no dose adjustment is necessary for the 3D regimen when coadministered with 17 of the 20 medications, coadministration with gemfibrozil, carbamazepine, or ethinyl estradiol-containing contraceptives is contraindicated.

Liver toxicity and risk of discontinuation in HIV/hepatitis C virus-coinfected patients receiving an etravirine-containing antiretroviral regimen: influence of liver fibrosis

OBJECTIVES

The aim of the study was to establish the risk of liver toxicity in HIV/hepatitis C virus (HCV)-coinfected patients receiving etravirine, according to the degree of liver fibrosis.

METHODS

A prospective cohort study of 211 HIV-infected patients initiating an etravirine-containing regimen was carried out. HCV coinfection was defined as a positive HCV RNA test, and baseline liver fibrosis was assessed by transient elastography. Hepatotoxicity was defined as clinical symptoms, or an aspartate aminotransferase (AST) or alanine aminotransferase (ALT) value > 5-fold higher than the upper limit of normal if baseline values were normal, or 3.5-fold higher if values were altered at baseline.

RESULTS

Overall, 145 patients (69%) were HCV coinfected, with a lower nadir (165 versus 220 cells/μL, respectively; p = 0.03) and baseline (374 versus 498 cells/μL, respectively; p = 0.04) CD4 count than monoinfected patients. Etravirine was mainly used with two nucleoside reverse transcriptase inhibitors (129; 61%) or with a boosted protease inhibitor (PI) (28%), with no significant differences according to HCV serostatus. Transient elastography in 117 patients (81%) showed a median (range) stiffness value of 8.25 (3.5-69) kPa, with fibrosis stage 1 in 43 patients (37%) and fibrosis stage 4 in 28 patients (24%). During an accumulated follow-up time of 449.3 patient-years (median 548 days), only one patient with advanced fibrosis (50.8 kPa) had grade 3-4 liver toxicity (0.7%). Transaminases changed slightly, with no significant differences compared with baseline fibrosis, and nine and six patients had grade 1 and 2 transaminase increases, respectively. Also, HCV coinfection was not associated with a higher risk of discontinuation (25% discontinued versus 21% of monoinfected patients; p = 0.39, log-rank test) or virological failure (8% versus 12%, respectively; p = 0.4).

CONCLUSIONS

Our data suggest that etravirine is a safe option for HIV/HCV-coinfected patients, including those with significant liver fibrosis.

[In Process Citation]

Approximately 70,000 people are infected with hepatitis C virus in Hungary, and more than half of them are not aware of their infection. From the point of infected individuals early recognition and effective treatment of related liver injury may prevent consequent advanced liver diseases and complications (liver cirrhosis, liver failure and liver cancer) and can increase work productivity and life expectancy. From a socioeconomic aspect, this could also prevent further spread of the virus as well as reduce substantially long term financial burden of related morbidity. Pegylated interferon + ribavirin dual therapy, which is available in Hungary since 2003, can clear the virus in 40-45% of previously not treated (naïve), and in 5-21% of previous treatment-failure patients. Addition of a direct acting first generation protease inhibitor drug (boceprevir or telaprevir) to the dual therapy increases the chance of sustained viral response to 63-75% and 59-66%, respectively. These two protease inhibitors are available and financed for a segment of Hungarian patients since May 2013. Between 2013 and February 2015, other direct acting antiviral interferon-free combination therapies have been registered for the treatment of chronic hepatitis C, with a potential efficacy over 90% and typical short duration of 8-12 weeks. Indication of therapy includes exclusion of contraindications to the drugs and demonstration of viral replication with consequent liver injury, i.e., inflammation and / or fibrosis in the liver. Non-invasive methods (elastography and biochemical methods) are accepted and preferred for staging liver damage (fibrosis). For initiation of treatment as well as for on-treatment decisions, accurate and timely molecular biology tests are mandatory. Eligibility for treatment is a subject of individual central medical review. Due to budget limitations therapy is covered only for a proportion of patients by the National Health Insurance Fund. Priority is given to those with urgent need based on a Hungarian Priority Index system reflecting primarily the stage of liver disease, and considering also additional factors, i.e., activity and progression of liver disease, predictive factors of treatment and other special issues. Approved treatments are restricted to the most cost-effective combinations based on the cost per sustained viral response value in different patient categories with consensus between professional organizations, National Health Insurance Fund and patient organizations. More expensive therapies might be available upon co-financing by the patient or a third party. Interferon-free treatments and shorter therapy durations preferred as much as financially feasible. A separate budget is allocated to cover interferon-free treatments for the most-in-need interferon ineligible/intolerant patients, and for those who have no more interferon-based therapy option. Orv. Hetil., 2015, 156(Suppl. 1), 3-23.

Antiviral drug discovery: broad-spectrum drugs from nature

Covering: up to April 2014. The development of drugs with broad-spectrum antiviral activities is a long pursued goal in drug discovery. It has been shown that blocking co-opted host-factors abrogates the replication of many viruses, yet the development of such host-targeting drugs has been met with scepticism mainly due to toxicity issues and poor translation to in vivo models. With the advent of new and more powerful screening assays and prediction tools, the idea of a drug that can efficiently treat a wide range of viral infections by blocking specific host functions has re-bloomed. Here we critically review the state-of-the-art in broad-spectrum antiviral drug discovery. We discuss putative targets and treatment strategies, with particular focus on natural products as promising starting points for antiviral lead development.

Drug interactions with new hepatitis C oral drugs

INTRODUCTION

Chronic hepatitis C virus (HCV) infection has recently become a curable disease with antiviral therapy. The knowledge of drug interactions using direct-acting antivirals (DAA) may permit maximizing antiviral efficacy and avoiding drug-related toxicities. Ageing in the chronic hepatitis C population, along with added co-morbidities that require other medications, has increased the attention on drug interactions using DAA.

AREAS COVERED

This review provides an update of the most clinically significant pharmacokinetic and pharmacodynamic drug interactions occurring between currently available DAA and other medications. The review also revisits how drug interactions with DAA can be prevented and managed.

EXPERT OPINION

Interactions between DAA and other drugs are frequent in clinical practice. The most frequent drug interactions modify drug metabolism by inducing or inhibiting the cytochrome P450, leading to abnormal drug exposures. Through this mechanism HCV protease inhibitors, especially when co-formulated with ritonavir as pharmacoenhancer, and non-nucleoside HCV polymerase inhibitors interact with other medications. In contrast, NS5B nucleos(t)ide analog inhibitors (i.e., sofosbuvir) and some HCV NS5A inhibitors (i.e., ledipasvir), which do not or only marginally affect CYP450, are relatively free of significant pharmacokinetic interactions. However, exposure to HCV nucleos(t)ide analogs may be influenced by induction/inhibition of drug transporters (i.e., P-glycoprotein) as well as by pharmacodynamic interference with other nucleos(t)ide analogs used as antivirals or cancer drugs. Drug interactions for some NS5A inhibitors (i.e., daclatasvir) are generally moderate and can be managed with dose adjustments.

Viral hepatitis C therapy: pharmacokinetic and pharmacodynamic considerations

Chronic hepatitis C is a global health problem. To prevent or reduce complications, the hepatitis C virus (HCV) infection needs to be eradicated. There have been several developments in treating these patients since the discovery of the virus. As of 1 January 2014, the drugs that are approved for treatment of chronic HCV infection are peginterferon-α, ribavirin, boceprevir, telaprevir, simeprevir and sofosbuvir. In this review we provide an overview of the clinical pharmacokinetic characteristics of these agents by describing their absorption, distribution, metabolism and excretion. In the pharmacodynamic part we summarize what is known about the relationships between the pharmacokinetics of each drug and efficacy or toxicity. We briefly discuss the pharmacokinetics and pharmacodynamics of chronic hepatitis C treatment in special patient populations, such as patients with liver cirrhosis, renal insufficiency or HCV/HIV coinfection, and children. With this knowledge, physicians, pharmacists, nurse practitioners, etc. should be educated to safely and effectively treat HCV-infected patients.

Medication use and medical comorbidity in patients with chronic hepatitis C from a US commercial claims database: high utilization of drugs with interaction potential

BACKGROUND

With the advent of the direct-acting antiviral agents, significant drug-drug interaction (DDI) potential now exists for patients treated for chronic hepatitis C virus (HCV) infection. However, little is known about how often patients with HCV infection use medications that may interact with newer HCV treatments, especially those with cytochrome P450 3A (CYP3A) DDI potential.

METHODS

Using a large US commercial insurance database, medication use and comorbidity burden were examined among adult patients with a chronic HCV diagnosis from 2006 to 2010. Medications were examined in terms of total number of prescription claims, proportion of patients exposed, and DDI potential with the prototypical CYP3A direct-acting antiviral agents boceprevir and telaprevir, for which data were available.

RESULTS

Patient comorbidity burden was high and increased over the study period. Medication use was investigated in 53 461 patients with chronic HCV. Twenty-one (53%) of the top 40 most utilized medications were classified as having interaction potential, with 62% of patients receiving at least one of the top 22 interacting medications by exposure. Of these, 59 and 41% were listed in a common DDI resource but not in medication-prescribing information, 77 and 77% had not been investigated in DDI studies, 41 and 36% did not have clear recommendations for DDI management, and only 14 and 23% carried a recommendation to avoid coadministration for boceprevir and telaprevir, respectively.

CONCLUSION

Practitioners may expect a medication with CYP3A DDI potential in two-thirds of patients with HCV and may expect almost one-half of the most frequently used medications to have CYP3A DDI potential. However, DDI potential may not be reflected in prescribing information.

Common GI Drug Interactions in the Elderly

OPINION STATEMENT

The careful review of drug-drug interactions is vital to the safe prescribing of medications for chronic medical conditions. The elderly population suffers from multiple medical problems, and polypharmacy leads to further morbidity in this vulnerable group of patients. We discuss gastrointestinal conditions such as GERD, peptic ulcer disease, gastroparesis, diarrhea, constipation, irritable bowel syndrome, inflammatory bowel disease, chronic liver disease and the commonly used medications in these conditions. Treatment options must be individualized and tailored to accommodate the underlying pharmacokinetics and known drug-drug interactions. The indication for the use of a therapeutic agent in the elderly and the duration of use must be frequently readdressed to help prevent polypharmacy and adverse drug reactions. Medications should be started at a low dose with careful titration to achieve a clinical response to prevent toxicity. The aim of this article is to increase awareness of important drug-drug interactions of commonly prescribed gastrointestinal medications in the elderly.

[Diagnosis, treatment, and follow-up of hepatitis C-virus related liver disease. Hungarian national consensus guideline]

Approximately 70 000 people are infected with hepatitis C virus in Hungary, more than half of whom are not aware of their infection. Early recognition and effective treatment of related liver injury may prevent consequent advanced liver diseases (liver cirrhosis and liver cancer) and its complications. In addition, it may increase work productivity and life expectancy of infected individual, and can prevent further viral transmission. Early recognition can substantially reduce the long term financial burden of related morbidity from socioeconomic point of view. Pegylated interferon + ribavirin dual therapy, which is available in Hungary since 2003, can kill the virus in 40-45% of previously not treated (naïve), and in 5-21% of previous treatment-failure patients. Addition of two direct acting first generation protease inhibitor drugs (boceprevir and telaprevir) to the dual therapy increased the chance of sustained clearance of virus to 63-75% and 59-66%, respectively. These two protease inhibitor drugs are available and financed for a segment of Hungarian patients since May 2013. Indication of therapy includes exclusion of contraindications to the drugs and demonstration of viral replication with consequent liver injury, i.e., inflammation and/or fibrosis in the liver. For initiation of treatment as well as for on-treatment decisions accurate and timely molecular biology tests are mandatory. Staging of liver damage (fibrosis) non-invasive methods (transient elastography and biochemical methods) are acceptable to avoid concerns of patients related to liver biopsy. Professional decision for treatment is balanced against budget limitations in Hungary, and priority is given to those with urgent need using a national Priority Index system reflecting stage of liver disease as well as additional factors (activity and progression of liver disease, predictive factors and other special circumstances). All naïve patients are given a first chance with dual therapy. Those with genotype 1 infection and with on-treatment or historic failure to dual therapy are eligible to receive protease inhibitor based triple therapy provided, they reach financial cutoff eligibility based on Priority Index. Duration of therapy is usually 48 weeks in genotype 1 with a response-guided potential to reduce duration for non-cirrhotic patients. Patients with non-1 genotypes are treated with dual therapy (without protease inhibitors) for a genotype and response driven duration of 16, 24, 48, or 72 week. Careful monitoring for early recognition and management of side-effects as well as viral response and potential breakthrough during protease-inhibitor therapy are recommended.

Using patient-reported outcomes to improve the management of co-infection with HIV and HCV: the ANRS CO13 HEPAVIH cohort

The management of co-infection with HIV and hepatitis C virus (HCV) is complicated by viral and drug-drug interactions, treatment-related side effects, and the poor response to therapy of certain HCV genotypes. Current or past drug use may also have a negative impact. HEPAVIH (ANRS CO13) is an ongoing French cohort study of co-infected individuals which combines medical and socio-behavioral follow-up. This cohort study aims at analyzing the course of HCV infection and access to HCV treatment in HIV-HCV co-infected patients, using both clinical and patient-reported outcomes. This article documents the main lessons learned to date from the HEPAVIH data and published literature, while describing research prospects and needs requiring further investigation in the field of patient-reported outcomes.

How to optimize current therapy of HCV genotype 1 infection with boceprevir

Treatment with first generation protease inhibitors (PIs) is a milestone in the history of HCV therapy. Triple therapy with boceprevir (BOC) improves sustained virological response (SVR) by 30% in treatment naïve genotype 1 patients and by 50-60% in relapsers, 40-45% in partial responders and 25% in null responders compared with the Pegylated Interferon (PEG-IFN) and ribavirin regimen. To optimize BOC treatment, screening and access to treatment must be improved in genotype 1 patients. To select the ideal candidate for immediate treatment with triple therapy, an individual risk/benefit ratio must be assessed. Recent data have shown that patients with compensated cirrhosis and more advanced disease may also benefit from this regimen. Moreover, in HCV patients with extrahepatic manifestations, patients with HCV recurrence after liver transplantation and HIV-HCV co-infected patients, immediate treatment with triple therapy should be discussed. There is growing evidence that triple therapy with BOC is cost-effective in genotype 1 patients. Finally, the treatment design of BOC must be optimized in relation to baseline characteristics, so that optimal stopping rules can be followed, Drug-drug interactions (DDIs) can be prevented and AEs can be accurately prevented and managed.