Triflic Acid-Promoted 1,2-Amino Migration Reactions in α-Arylaminoacrylamides: Access to Substituted β-Aminoamides

A straightforward synthesis of substituted β-aminoamides from α-arylamino-β-hydroxyacrylamides, α-arylamino-β-oxoamides, or their tautomeric mixture has been described. The (E)-enol triflate intermediates are readily generated in situ from these substrates in the presence of triflic anhydride (Tf2O) and triethylamine (Et3N) in a chemoselective manner and undergo triflic acid (TfOH)-promoted cyclization and ring-opening reactions with alcohols to deliver the desired products. The one-pot two-step synthetic protocol features the use of readily available starting materials, mild reaction conditions, high chemoselectivity, operational simplicity, and a wide range of synthetic potential of the products.

Invention of MK-7845, a SARS-CoV-2 3CL Protease Inhibitor Employing a Novel Difluorinated Glutamine Mimic

As SARS-CoV-2 continues to circulate, antiviral treatments are needed to complement vaccines. The virus's main protease, 3CLPro, is an attractive drug target in part because it recognizes a unique cleavage site, which features a glutamine residue at the P1 position and is not utilized by human proteases. Herein, we report the invention of MK-7845, a novel reversible covalent 3CLPro inhibitor. While most covalent inhibitors of SARS-CoV-2 3CLPro reported to date contain an amide as a Gln mimic at P1, MK-7845 bears a difluorobutyl substituent at this position. SAR analysis and X-ray crystallographic studies indicate that this group interacts with His163, the same residue that forms a hydrogen bond with the amide substituents typically found at P1. In addition to promising in vivo efficacy and an acceptable projected human dose with unboosted pharmacokinetics, MK-7845 exhibits favorable properties for both solubility and absorption that may be attributable to the unusual difluorobutyl substituent.

Aryl N-[ω-(6-Fluoroindol-1-yl)alkyl]carbamates as Inhibitors of Fatty Acid Amide Hydrolase, Monoacylglycerol Lipase, and Butyrylcholinesterase: Structure-Activity Relationships and Hydrolytic Stability

A series of aryl N-[ω-(6-fluoroindol-1-yl)alkyl]carbamates with alkyl spacers of varying lengths between the indole and the carbamate group and with differently substituted aryl moieties at the carbamate oxygen were synthesized and tested for inhibition of the pharmacologically interesting serine hydrolases fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), butyrylcholinesterase (BuChE), and acetylcholinesterase (AChE). Furthermore, the chemical stability in an aqueous solution and the metabolic stability toward esterases in porcine liver homogenate and porcine blood plasma were determined. While most of the synthesized derivatives were potent inhibitors of FAAH, a considerable inhibition of MAGL and BuChE was elicited only by compounds with a high carbamate reactivity, as evidenced by a significant hydrolysis of these compounds in an aqueous solution. However, the high inhibitory potency of some compounds toward MAGL and BuChE, especially that of the ortho-carboxyphenyl derivative 37, could not be explained by chemical reactivity alone. Several of the carbamates studied possessed varying degrees of stability toward esterases from liver and blood plasma. In some cases, marked inactivation by the pseudo-esterase activity of plasma albumin was observed. Mass spectrometric studies showed that such carbamates formed covalent bonds with albumin at several sites.

Urea Derivatives in Modern Drug Discovery and Medicinal Chemistry

The urea functionality is inherent to numerous bioactive compounds, including a variety of clinically approved therapies. Urea containing compounds are increasingly used in medicinal chemistry and drug design in order to establish key drug-target interactions and fine-tune crucial drug-like properties. In this perspective, we highlight physicochemical and conformational properties of urea derivatives. We provide outlines of traditional reagents and chemical procedures for the preparation of ureas. Also, we discuss newly developed methodologies mainly aimed at overcoming safety issues associated with traditional synthesis. Finally, we provide a broad overview of urea-based medicinally relevant compounds, ranging from approved drugs to recent medicinal chemistry developments.

Mental disorders in HIV/HCV coinfected patients under antiviral treatment for hepatitis C

This paper aims to review the epidemiology and management of mental disorders in human immunodeficiency virus (HIV)/hepatitis C virus (HCV) coinfected patients, the need for antiviral therapy in this specific population, and current treatment strategies for HIV/HCV patients with psychiatric and/or substance use disorders. This is a narrative review. Data was sourced from electronic databases and was not limited by language or date of publication. HIV infection has become a survivable chronic illness. Prevalence of HCV infection among HIV-infected patients is high ranging from 50% to 90%. Patients with psychiatric diseases have also an increased risk for HIV/HCV coinfection. The most effective strategy to decrease HCV-related morbidity and mortality in coinfection is to achieve viral eradication. Although psychiatric symptoms often appear during antiviral treatment and may be associated with the use of interferon-alpha (IFN-α), recent evidence suggests that many patients with comorbid mental and substance use disorders can be treated safely. Recent data indicate that IFNα-induced psychiatric side effects have a similar prevalence in HIV/HCV coinfected patients than in monoinfected patients and they can be managed and even prevented successfully with psychopharmacological strategies in the frame of a multidisciplinary team. New antivirals offer INF-free therapies for this specific population.

Clinical pharmacology profile of boceprevir, a hepatitis C virus NS3 protease inhibitor: focus on drug-drug interactions

Boceprevir is a potent, orally administered ketoamide inhibitor that targets the active site of the hepatitis C virus (HCV) non-structural (NS) 3 protease. The addition of boceprevir to peginterferon plus ribavirin resulted in higher rates of sustained virologic response (SVR) than for peginterferon plus ribavirin alone in phase III studies in both previously treated and untreated patients with HCV infection. Because boceprevir is metabolized by metabolic routes common to many other drugs, and is an inhibitor of cytochrome P450 (CYP) 3A4/5, there is a high potential for drug-drug interactions when boceprevir is administered with other therapies, particularly when treating patients with chronic HCV infection who are often receiving other medications concomitantly. Boceprevir is no longer widely used in the US or EU due to the introduction of second-generation treatments for HCV infection. However, in many other geographic regions, first-generation protease inhibitors such as boceprevir continue to form an important treatment option for patients with HCV infection. This review summarizes the interactions between boceprevir and other therapeutic agents commonly used in this patient population, indicating dose adjustment requirements where needed. Most drug interactions do not affect boceprevir plasma concentrations to a clinically meaningful extent, and thus efficacy is likely to be maintained when boceprevir is coadministered with the majority of other therapeutics. Overall, the drug-drug interaction profile of boceprevir suggests that this agent is suitable for use in a wide range of HCV-infected patients receiving concomitant therapies.

Intracellular accumulation of boceprevir according to plasma concentrations and pharmacogenetics

Boceprevir (BOC) is a directly-acting antiviral agent for the treatment of hepatitis C virus genotype 1 (HCV-1) infection. It is a mixture of two stereoisomers, the inactive R and the active S isomers. No data have previously been published on BOC intracellular accumulation. In this study, BOC isomer concentrations in peripheral blood mononuclear cells (PBMCs) and plasma were determined. The influence of various single nucleotide polymorphisms (SNPs) on plasma and intracellular drug exposure at Week 4 of triple therapy were also evaluated. Plasma and intracellular BOC concentrations were determined at the end of the dosing interval (C(trough)) using a UPLC-MS/MS validated method. Allelic discrimination was performed through real-time PCR. Median plasma concentrations were 65.97 ng/mL for the S isomer and 36.31 ng/mL for the R isomer; the median S/R plasma concentration ratio was 1.66. The median PBMC concentration was 2285.88 ng/mL for the S isomer; the R isomer was undetectable within PBMCs. The median S isomer PBMC/plasma concentration ratio was 28.59. A significant positive correlation was found between plasma and PBMC S isomer concentrations. ABCB1 1236, SLC28A2 124 and IL28B rs12979860 SNPs were associated with the S isomer PBMC/plasma concentration ratio. In regression models, S isomer plasma levels and FokI polymorphism were able to predict S isomer intracellular exposure, whereas SNPs in AKR1, BCRP1 and SLC28A2 predicted the S isomer PBMC/plasma concentration ratio. No similar data regarding BOC pharmacogenetics and pharmacokinetics have been published previously. This study adds a novel and useful overview of the pharmacological properties of this drug.

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.

Pharmacokinetic interaction between HCV protease inhibitor boceprevir and methadone or buprenorphine in subjects on stable maintenance therapy

PURPOSE

Intravenous opioid use is a common route of hepatitis C virus (HCV) infection; consequently, the prevalence of HCV is high among patients on methadone or buprenorphine/naloxone. The authors evaluated the pharmacokinetic interaction of boceprevir with methadone or buprenorphine/naloxone in patients on stable maintenance therapy.

METHODS

This was a two-center, open-label, fixed-sequence study in 21 adult volunteers on stable maintenance therapy. Oral methadone (20-150 mg once daily) or sublingual buprenorphine/naloxone (8/2-24/6 mg once daily) was administered alone or in combination with boceprevir (800 mg every 8 h) on days 2-7. Pharmacokinetic sampling occurred before and up to 24 h after the dose on days 1 and 7.

RESULTS

Coadministration of boceprevir reduced the area under the concentration-time curve during a dosing interval τ (AUC τ ) and maximum observed plasma (or serum) concentration (C max) of R-methadone (geometric mean ratios (GMRs) [90 % confidence intervals (CIs)], 0.85 [0.74, 0.96] and 0.90 [0.71, 1.13]) and S-methadone (GMRs [90 % CIs], 0.78 [0.66, 0.93] and 0.83 [0.64, 1.09]). Boceprevir increased the AUC τ and C max of buprenorphine (GMRs [90 % CIs], 1.19 [0.91, 1.58] and 1.18 [0.93, 1.50]) and naloxone (GMRs [90 % CIs], 1.33 [0.90, 1.93] and 1.09 [0.79, 1.51]). Boceprevir exposure upon methadone or buprenorphine/naloxone coadministration was not clinically different from historical controls and there was no evidence of opioid withdrawal or excess.

CONCLUSIONS

There was no clinically meaningful impact of boceprevir on methadone or buprenorphine pharmacokinetics, suggesting that methadone/buprenorphine dose adjustments are not required upon coadministration with boceprevir. Individual patients may differ in their clinical experience and clinicians should maintain vigilance when coadministering these medications.

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.

[Drug-drug interaction with telaprevir or boceprevir in liver transplant patients: about four cases]

Boceprevir and telaprevir are both direct-acting antivirals indicated, as part of combination therapy for the management of chronic hepatitis C virus (HCV) genotype 1 infection. Transplanted patients treated with anticalcineurines (tacrolimus and cyclosporine) are confronted with major risks of interactions. Indeed, these antiviral are strong inhibitors of the enzyme cytochrome 3A4/A5, responsible for the metabolisme of ciclosprine and tacrolimus. The literature gives evidence of the dangerousness of this drug-drug interaction. We report four clinical cases illustrating the dosage adaptations at liver transplant patients and treated by telaprevir or boceprevir. To protect the immunosuppressive efficiency, a multidisciplinary care and narrow monitoring of the interaction between immunosuppressing agents and protease inhibitors were necessary.

Pharmacokinetic and pharmacodynamic interactions between the hepatitis C virus protease inhibitor, boceprevir, and the oral contraceptive ethinyl estradiol/norethindrone

PURPOSE

The purpose of this study was to examine drug interactions between boceprevir, a hepatitis C virus NS3/4A protease inhibitor, and a combined oral contraceptive containing ethinyl estradiol (EE) and norethindrone (NE).

METHODS

A single-center, open-label study was conducted in 20 healthy female volunteers. In three consecutive 28-day treatment periods, subjects received EE/NE (0.035 mg/1 mg; 21 days on, 7 days off). During period 3, subjects also received boceprevir (800 mg three times daily) for 28 days.

RESULTS

Coadministration of boceprevir with EE/NE did not affect NE AUC0-24 but slightly reduced NE C max. Geometric mean ratios (GMRs) for NE AUC0-24 and C max with EE/NE alone and EE/NE plus boceprevir were 0.96 (90% confidence interval (CI), 0.87-1.06) and 0.83 (90% CI, 0.76-0.90). Coadministration of boceprevir with EE/NE reduced EE AUC0-24 and C max by 26 and 21%, with GMRs of 0.74 (90% CI, 0.68-0.80) and 0.79 (90% CI, 0.75-0.84). Boceprevir had no effect on mid-cycle luteinizing hormone (LH), follicle-stimulating hormone (FSH), or sex hormone-binding globulin levels, and progesterone concentrations remained <1 ng/ml during the luteal phase. Adverse events reported in this study were consistent with the well-established safety profile of boceprevir.

CONCLUSION

Serum progesterone, LH, and FSH levels indicate that ovulation was suppressed during coadministration of boceprevir with EE/NE. Coadministration of boceprevir with combined oral contraceptives containing EE and ≥1 mg of NE is therefore unlikely to alter contraceptive effectiveness. The ovulation suppression activity of oral contraceptives containing lower doses of NE, and of other forms of hormonal contraception during coadministration with boceprevir, has not been established.

Drug interactions and protease inhibitors used in the treatment of hepatitis C: how to manage?

PURPOSE

The first-generation protease inhibitors (PI) boceprevir and telaprevir combined with pegylated interferon have revolutionized the treatment of type-1 hepatitis C by increasing the rates of sustained virologic response. However, they induce drug interactions, and their clinical relevance is difficult to predict. This review compiles available data on drug-drug interactions (DDI) based on their pharmacokinetic and pharmacodynamic properties with the aim of assisting clinicians in managing DDI METHODS: PubMed, drug interaction databases and hepatology and infectious disease conference abstracts were systematically searched using the key search terms "interaction", "hepatitis C", "telaprevir" and "boceprevir". All known interactions were compiled and reclassified according to their pharmacokinetic and pharmacodynamic mechanisms. The state of knowledge of interaction mechanisms are reported and a therapeutic approach is proposed.

RESULTS

Boceprevir and telaprevir are both substrates and potent inhibitors of cytochrome P450 3A4 and the drug transporter P-glycoprotein. They induce overdosage but can sometimes decrease the effect of other drugs by inducing other cytochromes. Overdosage or low dosage mainly affects drugs with a narrow therapeutic range, such as immunosuppressants or antiretrovirals. The distribution and elimination of PI are unaffected by interactions. In terms of pharmacodynamic interactions, PI can trigger drug-induced QT interval prolongation, which means that clinicians should manage such risk factors as potassium/magnesium levels or avoid other QT-prolonging drugs.

CONCLUSIONS

Management of hepatitis C therapy is complex. The key to interpreting DDI data is a solid understanding of the pharmacokinetic and pharmacodynamic profiles of the drugs involved. Their ability to inhibit cytochrome P450 3A4 and prolong the QT interval can have significant clinical consequences. This review provides a practical guide to the safe and effective management of therapy with boceprevir and telaprevir.

Drug-drug interactions in the treatment of HCV among people who inject drugs

Boceprevir and telaprevir are inhibitors and substrates of the cytochrome P450 3A4 family. With the use of these HCV protease inhibitors as part of standard therapy for chronic hepatitis C genotype 1 infection, drug-drug interactions with multiple medications being inductors, inhibitors, or substrates of cytochrome P450 3A4 can be expected. Due to the complexity of these interactions, predicting the expected magnitude and sometimes even the direction of the effect has proven to be difficult. Pharmacokinetic studies should be carried out to evaluate drugs with clinical relevance and possible interactions. This review focuses on the data available regarding drugs that are frequently used in the setting of addiction or used by patients with addiction. In addition to highlighting relevant drug-drug interactions, alternative drugs that can be safely used are suggested.

Effect of fibrosis on adverse events in patients with hepatitis C treated with telaprevir

BACKGROUND

Data about adverse events are needed to optimise telaprevir-based therapy in a broad spectrum of patients.

AIM

To investigate adverse events of telaprevir-based therapy in patients with and without advanced fibrosis or cirrhosis in a real-world setting.

METHODS

Data on 174 hepatitis C-infected patients initiating telaprevir-based therapy at Mount Sinai and Montefiore medical centres were collected. Biopsy data and FIB-4 scores identified patients with advanced fibrosis. Multivariable fully adjusted models were built to assess the effect of advanced fibrosis on specific adverse events and discontinuation of treatment due to an adverse event.

RESULTS

Patients with (n = 71) and without (n = 103) advanced fibrosis were similar in BMI, ribavirin exposure, gender, prior treatment history, haemoglobin and creatinine, but differed in race. Overall, 47% of patients completed treatment and 40% of patients achieved SVR. Treated patients with and without advanced fibrosis or cirrhosis had similar rates of adverse events; advanced fibrosis, however, was independently associated with ano-rectal discomfort (P = 0.03). Three patients decompensated and had advanced fibrosis. The discontinuation of all treatment medications due to an adverse event was significantly associated with older age (P = 0.01), female gender (P = 0.01) and lower platelets (P = 0.03).

CONCLUSIONS

Adverse events were common, but were not significantly related to the presence of advanced fibrosis or cirrhosis. More critical monitoring in older and female patients with low platelets throughout treatment may reduce adverse event-related discontinuations.

A review of pharmacological interactions between HIV or hepatitis C virus medications and opioid agonist therapy: implications and management for clinical practice

Global access to opioid agonist therapy and HIV/hepatitis C virus (HCV) treatment is expanding but when used concurrently, problematic pharmacokinetic and pharmacodynamic interactions may occur. Articles published from 1966 to 2012 in Medline were reviewed using the following keywords: HIV, AIDS, HIV therapy, HCV, HCV therapy, antiretroviral therapy, highly active antiretroviral therapy, drug interactions, methadone and buprenorphine. In addition, a review of abstracts from national and international meetings and conference proceedings was conducted; selected reports were reviewed as well. The metabolism of both opioid and antiretroviral therapies, description of their known interactions and clinical implications and management of these interactions were reviewed. Important pharmacokinetic and pharmacodynamic drug interactions affecting either methadone or HIV medications have been demonstrated within each class of antiretroviral agents. Drug interactions between methadone, buprenorphine and HIV medications are known and may have important clinical consequences. Clinicians must be alert to these interactions and have a basic knowledge regarding their management.

Antiretroviral and anti-hepatitis C virus direct-acting antiviral-related hepatotoxicity

Antiretroviral-related hepatotoxicity occurs commonly in patients with human immunodeficiency virus (HIV). Liver injury ranges from unconjugated hyperbilirubinemia and nodular regenerative hyperplasia to lactic acidosis and toxic hepatitis. Effective antiretroviral therapy has changed coinfected patients' primary morbidities and mortality to chronic liver disease rather than complications from HIV. Treatment for hepatitis C virus (HCV) is strongly encouraged early in all coinfected patients. However, drug-drug interactions must be considered to ensure safe and tolerable use alone or in combination with antiretroviral therapies. The first-generation and newer HCV direct-acting antivirals are promising in coinfected patients, with minimal side effects and hepatotoxicity.

The pharmacokinetic evaluation of boceprevir for treatment of hepatitis C virus

INTRODUCTION

Boceprevir is an NS3/NS4A serine protease inhibitor that was approved for use in Hepatitis C virus (HCV) genotype 1 patients by the US Food and Drug Administration (FDA) in May 2011. The approval of this protease inhibitor marked a major paradigm shift in the treatment of HCV, as it was one of the first of many new small molecules specifically designed and approved for HCV.

AREAS COVERED

In this article, the authors summarize boceprevir's pharmacokinetic and pharmacodynamic properties. In addition, they review Phase II and III trials of boceprevir as well as its clinical efficacy, dosing and safety.

EXPERT OPINION

Boceprevir is a potent protease inhibitor for the treatment of genotype 1 HCV. It has a well-tolerated side-effect profile and increases the likelihood of SVR in naïve and previously treated patients. The impending release of newer more efficacious direct-acting antivirals may limit the use of boceprevir for patients infected with HCV.

The importance of drug-drug interactions in the DAA era

With the licensing of the direct acting antivirals telaprevir and boceprevir the topic of drug-drug interactions has come to the forefront. These first generation hepatitis C virus protease inhibitors are metabolized by and inhibit the key drug metabolizing enzyme CYP3A4, which means that knowledge of drug-drug interactions has become an essential component of the evaluation of a patient starting triple therapy. The number of potential co-medications means that many drugs will be used in hepatitis C virus patients where there are no pharmacokinetic study data. Here we have to use the data that are available and seek to extrapolate to unstudied drugs using key principles of clinical pharmacology (disposition characteristics, concentration-effect relationships, therapeutic window) in order to give some guidance for management of patients. This is a rapidly moving area in hepatitis C therapy, both in terms of understanding the drug interaction profile of telaprevir and boceprevir, interaction mechanisms that sometimes appear counterintuitive and that may involve enzymes other than CYP3A4 or transporters, but then seeking to understand the interaction potential of the next wave of drugs that will soon be with us.

Boceprevir: a review of its use in the management of chronic hepatitis C genotype 1 infection

Boceprevir (Victrelis®) is an inhibitor of the hepatitis C virus (HCV) non-structural protein NS3-4A serine protease and is used in combination with pegylated interferon (peginterferon)-alpha and ribavirin in the treatment of adults with chronic HCV (chronic hepatitis C) genotype 1 infection. Of the various genotypes of HCV, genotype 1 is one of the least responsive to interferon and ribavirin-based therapy, and thus most in need of novel treatments. This article reviews the available pharmacological properties of boceprevir and its clinical efficacy and tolerability in the treatment of chronic hepatitis C genotype 1 infection in adult patients who are either treatment-naive or have failed previous standard therapy. Boceprevir, when co-administered with peginterferon-alpha and ribavirin in patients with chronic hepatitis C genotype 1 infection who were treatment-naive or had previously not fully responded to or had relapsed following treatment, was associated with a significantly higher sustained virological response rate (defined as the proportion of patients with an undetectable plasma HCV RNA level at week 24 of the follow-up period [week 72 overall]) [primary endpoint] than peginterferon-alpha-2b and ribavirin alone, regardless of the boceprevir administration regimen, in the phase III SPRINT-2 (treatment-naive patients) and RESPOND-2 (previously treated patients) trials. There was no significant difference between full-duration (44 weeks) and response-guided (24 or 32 weeks followed by follow-up or peginterferon-alpha-2b plus ribavirin alone) boceprevir regimen recipients with regard to sustained virological response rate. All patients received an initial 4-week lead-in treatment period before the comparative treatment period began. Overall, boceprevir is generally well tolerated when administered concomitantly with peginterferon-alpha plus ribavirin in patients with chronic hepatitis C genotype 1 infection. The most common adverse events in any treatment group were flu-like symptoms, which are typically reported in patients receiving peginterferon-ribavirin therapy. The addition of boceprevir to peginterferon-alpha and ribavirin is associated with an increased risk of anaemia and neutropenia. In conclusion, boceprevir in combination with peginterferon-alpha and ribavirin is an effective and generally well tolerated treatment for treatment-naive or previously treated adult patients with chronic hepatitis C genotype 1 infection. The drug is associated with higher sustained virological response rates in these patients, in whom treatment with interferon and ribavirin alone may not be successful. Thus, boceprevir in combination with peginterferon-alpha and ribavirin is a valuable new treatment option for use in patients with chronic hepatitis C genotype 1 infection.

Boceprevir: a recently approved protease inhibitor for hepatitis C virus infection

PURPOSE

The pharmacologic properties, clinical efficacy, and safety profile of the first oral protease inhibitor approved for the treatment of chronic infection with hepatitis C virus (HCV) genotype 1 are reviewed.

SUMMARY

Boceprevir, approved by the Food and Drug Administration as an adjunct to the standard regimen for HCV genotype 1 infection (peginterferon alfa and ribavirin), is available in 200-mg capsules, to be administered thrice daily at seven-to nine-hour intervals (total daily dose, 2400 mg). In two Phase III clinical trials involving a total of nearly 1500 previously untreated patients who were not sufficiently responsive to or had relapsed after standard therapy, the adjunctive use of boceprevir was associated with significantly higher rates of sustained virologic response and a shorter cumulative duration of treatment. Adverse effects occurring significantly more often in clinical trial participants receiving boceprevir relative to control groups included anemia (47% versus 20%), dysgeusia (35% versus 16%), and neutropenia (25% versus 19%); these were generally not treatment-limiting effects. Due to the potential for serious or potentially life-threatening adverse events, boceprevir use is contraindicated in patients receiving any of a wide range of drugs whose clearance is highly dependent on cytochrome P-450 (CYP) isoenzymes 3A4/5 (e.g., cisapride, lovastatin, midazolam, sildenafil); boceprevir is also contraindicated for patients receiving potent CYP3A4/5 inducers such as carbamazepine, phenytoin, and rifampin, whose concurrent use can diminish boceprevir's virologic activity. Close monitoring is critical to ensure patient adherence to triple-drug therapy and, more broadly, to reduce the risk of the development and transmission of resistant HCV strains.

CONCLUSION

Previously untreated patients with chronic HCV monoinfection, as well as patients who do not respond adequately to or relapse after standard dual therapy, may benefit from adjunctive boceprevir therapy. Careful selection and close monitoring of patients receiving boceprevir are essential to avoid drug-drug interactions, reduce adverse effects, and optimize treatment outcomes.

Current and future therapies for hepatitis C virus infection

Only 20 years after the discovery of the Hepatitis C Virus (HCV), a cure is now likely for most people affected by this chronic infection, which carries a substantial disease burden, not only in the United States but also worldwide.1 The recent approval of two direct-acting antiviral agents that specifically inhibit viral replication has dramatically increased the viral clearance rate, from less than 10% with the initial regimen of interferon monotherapy to more than 70% with current therapy. Moreover, many other drugs targeting viral or host factors are in development, and some will almost certainly be approved in the coming years. The questions of who should be treated and with what regimen will be increasingly complex to address and will require careful consideration. As therapy improves, systemwide identification and care of patients who need treatment will be the next challenge. Because most infected persons are unaware of their diagnosis, the Centers for Disease Control and Prevention recently recommended screening for HCV all persons born between 1945 and 1965.2 ,3 It is anticipated that in the course of such a screening process, a large number of persons will be found to be infected with the virus; whether it will be possible to treat all these people is unclear. This article reviews the current therapy for HCV infection and the landscape of drug development.

Clinical management of drug-drug interactions in HCV therapy: challenges and solutions

Hepatitis C virus (HCV) infected patients often take multiple co-medications to treat adverse events related to HCV therapy, or to manage other co-morbidities. Drug-drug interactions associated with this polypharmacy are relatively new to the field of HCV pharmacotherapy. With the advent of the direct-acting antivirals telaprevir and boceprevir, which are both substrates and inhibitors of the cytochrome P450 (CYP) 3A iso-enzyme, knowledge and awareness of drug-drug interactions have become a cornerstone in the evaluation of patients starting and continuing HCV combination therapy. In our opinion, an overview of conducted drug-drug interaction studies and a list of contraindicated medications is not enough for the clinical management of these drug-drug interactions. Knowledge of pharmacokinetic profiles and concentration-effect relationships is key for the interpretation of these data, and insight into how to manage these interactions (e.g., dose adjustments, safe alternatives and therapeutic drug monitoring) is of equal importance. This review provides a practical overview of the safe and effective management of these clinical challenges.

Pharmacokinetic evaluation of the interaction between hepatitis C virus protease inhibitor boceprevir and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors atorvastatin and pravastatin

Boceprevir is a potent orally administered inhibitor of hepatitis C virus and a strong, reversible inhibitor of CYP3A4, the primary metabolic pathway for many 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Thus, the aim of the present study was to investigate drug-drug interactions between atorvastatin or pravastatin and boceprevir. We conducted a single-center, open-label, fixed-sequence, one-way-crossover study with 20 healthy adult volunteers. Subjects received single-dose atorvastatin (40 mg) or pravastatin (40 mg) on day 1, followed by boceprevir (800 mg three times daily) for 7 to 10 days. Repeat single doses of atorvastatin or pravastatin were administered in the presence of steady-state boceprevir. Atorvastatin exposure increased in the presence of boceprevir, with atorvastatin area under the concentration-time curve from time zero to infinity after single dosing (AUC(inf)) increasing 2.3-fold (90% confidence interval [CI], 1.85, 2.90) and maximum observed concentration in plasma (Cmax) 2.7-fold (90% CI, 1.81, 3.90). Pravastatin exposure was slightly increased in the presence of boceprevir, with pravastatin AUC(inf) increasing 1.63-fold (90% CI, 1.03, 2.58) and C(max) 1.49-fold (90% CI, 1.03, 2.14). Boceprevir exposure was generally unchanged when the drug was coadministered with atorvastatin or pravastatin. All adverse events were mild and consistent with the known safety profile of boceprevir. The observed 130% increase in AUC of atorvastatin supports the use of the lowest possible effective dose of atorvastatin when coadministered with boceprevir, without exceeding a maximum daily dose of 40 mg. The observed 60% increase in pravastatin AUC with boceprevir coadministration supports the initiation of pravastatin treatment at the recommended dose when coadministered with boceprevir, with close clinical monitoring.

In vitro assessment of drug-drug interaction potential of boceprevir associated with drug metabolizing enzymes and transporters

The inhibitory effect of boceprevir (BOC), an inhibitor of hepatitis C virus nonstructural protein 3 protease was evaluated in vitro against a panel of drug-metabolizing enzymes and transporters. BOC, a known substrate for cytochrome P450 (P450) CYP3A and aldo-ketoreductases, was a reversible time-dependent inhibitor (k(inact) = 0.12 minute(-1), K(I) = 6.1 µM) of CYP3A4/5 but not an inhibitor of other major P450s, nor of UDP-glucuronosyltransferases 1A1 and 2B7. BOC showed weak to no inhibition of breast cancer resistance protein (BCRP), P-glycoprotein (Pgp), or multidrug resistance protein 2. It was a moderate inhibitor of organic anion transporting polypeptide (OATP) 1B1 and 1B3, with an IC(50) of 18 and 4.9 µM, respectively. In human hepatocytes, BOC inhibited CYP3A-mediated metabolism of midazolam, OATP1B-mediated hepatic uptake of pitavastatin, and both the uptake and metabolism of atorvastatin. The inhibitory potency of BOC was lower than known inhibitors of CYP3A (ketoconazole), OATP1B (rifampin), or both (telaprevir). BOC was a substrate for Pgp and BCRP but not for OATP1B1, OATP1B3, OATP2B1, organic cation transporter, or sodium/taurocholate cotransporting peptide. Overall, our data suggest that BOC has the potential to cause pharmacokinetic interactions via inhibition of CYP3A and CYP3A/OATP1B interplay, with the interaction magnitude lower than those observed with known potent inhibitors. Conversely, pharmacokinetic interactions of BOC, either as a perpetrator or victim, via other major P450s and transporters tested are less likely to be of clinical significance. The results from clinical drug-drug interaction studies conducted thus far are generally supportive of these conclusions.

Single-dose pharmacokinetics of boceprevir in subjects with impaired hepatic or renal function

BACKGROUND AND OBJECTIVE

Boceprevir is a novel inhibitor of the hepatitis C virus NS3 protease and was recently approved for the treatment of patients with chronic hepatitis C infection. The objective of this study was to evaluate the impact of impaired hepatic or renal function on boceprevir pharmacokinetics and safety/tolerability.

METHODS

We conducted two open-label, single-dose, parallel-group studies comparing the safety and pharmacokinetics of boceprevir in patients with varying degrees of hepatic impairment compared with healthy controls in one study and patients with end-stage renal disease (ESRD) on haemodialysis with healthy controls in the other. Patients with hepatic impairment (mild [n = 6], moderate [n = 6], severe [n = 6] and healthy controls [n = 6]) received a single dose of boceprevir (400 mg) on day 1, and whole blood was collected at selected timepoints up to 72 hours postdose to measure plasma drug concentrations. Patients with ESRD and healthy subjects received a single dose of boceprevir 800 mg orally on days 1 and 4, with samples for pharmacokinetic analyses collected at selected timepoints up to 48 hours postdose on both days. In addition, 4 hours after dosing on day 4, patients with ESRD underwent haemodialysis with arterial and venous blood samples collected up to 8 hours postdose.

RESULTS

In the hepatic impairment study, there was a trend toward increased mean maximum (peak) plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC) of boceprevir with increasing severity of liver impairment. Point estimates for the geometric mean ratio for C(max) ranged from 100% in patients with mild hepatic impairment to 161% in patients with severe hepatic impairment, with the geometric mean ratio for AUC ranging from 91% in patients with mild hepatic impairment to 149% for patients with severe hepatic impairment, relative to healthy subjects. The mean elimination half-life (t(1/2;)) and median time to C(max) (t(max)) values of boceprevir were similar in healthy subjects and patients with hepatic impairment. In the renal impairment study, mean boceprevir C(max) and AUC values were comparable in patients with ESRD and in healthy subjects, with point estimates for the geometric mean ratio of 81% and 90%, respectively, compared with healthy subjects. Mean t(1/2;), median t(max) and mean apparent oral total clearance (CL/F) values were similar in healthy subjects and patients with ESRD. Boceprevir exposure was also similar in patients with ESRD on day 1 (no dialysis) and day 4 (dialysis beginning 4 hours postdose), with point estimates for the geometric mean ratio of C(max) and AUC to the last measurable sampling time (AUC(last)) on day 1 compared with day 4 of 88% and 98%, respectively. Treatment-emergent adverse events were reported in one patient with severe hepatic impairment (mild vomiting) and two patients with ESRD (moderate ventricular extrasystoles, flatulence and catheter thrombosis).

CONCLUSION

In the present studies, the pharmacokinetic properties of boceprevir were not altered to a clinically meaningful extent in patients with impaired liver or renal function. These data indicate that boceprevir dose adjustment is not warranted in patients with impaired hepatic function or ESRD, including those receiving dialysis. Boceprevir is not removed by haemodialysis.

Single-dose pharmacokinetics of boceprevir in subjects with impaired hepatic or renal function

BACKGROUND AND OBJECTIVE

Boceprevir is a novel inhibitor of the hepatitis C virus NS3 protease and was recently approved for the treatment of patients with chronic hepatitis C infection. The objective of this study was to evaluate the impact of impaired hepatic or renal function on boceprevir pharmacokinetics and safety/tolerability.

METHODS

We conducted two open-label, single-dose, parallel-group studies comparing the safety and pharmacokinetics of boceprevir in patients with varying degrees of hepatic impairment compared with healthy controls in one study and patients with end-stage renal disease (ESRD) on haemodialysis with healthy controls in the other. Patients with hepatic impairment (mild [n = 6], moderate [n = 6], severe [n = 6] and healthy controls [n = 6]) received a single dose of boceprevir (400 mg) on day 1, and whole blood was collected at selected timepoints up to 72 hours postdose to measure plasma drug concentrations. Patients with ESRD and healthy subjects received a single dose of boceprevir 800 mg orally on days 1 and 4, with samples for pharmacokinetic analyses collected at selected timepoints up to 48 hours postdose on both days. In addition, 4 hours after dosing on day 4, patients with ESRD underwent haemodialysis with arterial and venous blood samples collected up to 8 hours postdose.

RESULTS

In the hepatic impairment study, there was a trend toward increased mean maximum (peak) plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC) of boceprevir with increasing severity of liver impairment. Point estimates for the geometric mean ratio for C(max) ranged from 100% in patients with mild hepatic impairment to 161% in patients with severe hepatic impairment, with the geometric mean ratio for AUC ranging from 91% in patients with mild hepatic impairment to 149% for patients with severe hepatic impairment, relative to healthy subjects. The mean elimination half-life (t(1/2;)) and median time to C(max) (t(max)) values of boceprevir were similar in healthy subjects and patients with hepatic impairment. In the renal impairment study, mean boceprevir C(max) and AUC values were comparable in patients with ESRD and in healthy subjects, with point estimates for the geometric mean ratio of 81% and 90%, respectively, compared with healthy subjects. Mean t(1/2;), median t(max) and mean apparent oral total clearance (CL/F) values were similar in healthy subjects and patients with ESRD. Boceprevir exposure was also similar in patients with ESRD on day 1 (no dialysis) and day 4 (dialysis beginning 4 hours postdose), with point estimates for the geometric mean ratio of C(max) and AUC to the last measurable sampling time (AUC(last)) on day 1 compared with day 4 of 88% and 98%, respectively. Treatment-emergent adverse events were reported in one patient with severe hepatic impairment (mild vomiting) and two patients with ESRD (moderate ventricular extrasystoles, flatulence and catheter thrombosis).

CONCLUSION

In the present studies, the pharmacokinetic properties of boceprevir were not altered to a clinically meaningful extent in patients with impaired liver or renal function. These data indicate that boceprevir dose adjustment is not warranted in patients with impaired hepatic function or ESRD, including those receiving dialysis. Boceprevir is not removed by haemodialysis.

Pharmacokinetic interaction between the hepatitis C virus protease inhibitor boceprevir and cyclosporine and tacrolimus in healthy volunteers

The hepatitis C virus protease inhibitor boceprevir is a strong inhibitor of cytochrome P450 3A4 and 3A5 (CYP3A4/5). Cyclosporine and tacrolimus are calcineurin inhibitor immunosuppressants used to prevent organ rejection after liver transplantation; both are substrates of CYP3A4. This two-part pharmacokinetic interaction study evaluated boceprevir with cyclosporine (part 1) and tacrolimus (part 2). In part 1, 10 subjects received single-dose cyclosporine (100 mg) on day 1, single-dose boceprevir (800 mg) on day 3, and concomitant cyclosporine/boceprevir on day 4. After washout, subjects received boceprevir (800 mg three times a day) for 7 days plus single-dose cyclosporine (100 mg) on day 6. In part 2A, 12 subjects received single-dose tacrolimus (0.5 mg). After washout, they received boceprevir (800 mg three times a day) for 11 days plus single-dose tacrolimus (0.5 mg) on day 6. In part 2B, 10 subjects received single-dose boceprevir (800 mg) and 24 hours later received boceprevir (800 mg) plus tacrolimus (0.5 mg). Coadministration of boceprevir with cyclosporine/tacrolimus was well tolerated. Concomitant boceprevir increased the area under the concentration-time curve from time 0 to infinity after single dosing (AUC(inf) ) and maximum observed plasma (or blood) concentration (C(max) ) of cyclosporine with geometric mean ratios (GMRs) (90% confidence interval [CI]) of 2.7 (2.4-3.1) and 2.0 (1.7-2.4), respectively. Concomitant boceprevir increased the AUC(inf) and C(max) of tacrolimus with GMRs (90% CI) of 17 (14-21) and 9.9 (8.0-12), respectively. Neither cyclosporine nor tacrolimus coadministration had a meaningful effect on boceprevir pharmacokinetics.

CONCLUSION

Dose adjustments of cyclosporine should be anticipated when administered with boceprevir, guided by close monitoring of cyclosporine blood concentrations and frequent assessments of renal function and cyclosporine-related side effects. Administration of boceprevir plus tacrolimus requires significant dose reduction and prolongation of the dosing interval for tacrolimus, with close monitoring of tacrolimus blood concentrations and frequent assessments of renal function and tacrolimus-related side effects.

Boceprevir: a novel NS3/4 protease inhibitor for the treatment of hepatitis C

Hepatitis C virus (HCV) infection affects over 170 million people worldwide and is the most common blood-borne infection in the United States. Standard treatment with peginterferon alfa-ribavirin results in low sustained virologic response (SVR) rates in many patients, especially those who are African-American, are coinfected with human immunodeficiency virus (HIV), or have liver cirrhosis. Because of suboptimal SVR rates, new direct-acting antiviral agents that target HCV viral replication steps are in development. Boceprevir is one of the novel NS3/4A protease inhibitors that was recently approved by the U.S. Food and Drug Administration. We evaluated the literature regarding boceprevir by performing a MEDLINE search (January 1996-July 2011) to identify relevant clinical trials. Abstracts and poster and oral presentations from hepatology and HIV conferences were also reviewed. Potent anti-HCV activity was seen in clinical trials with boceprevir when it was studied in HCV genotype 1-infected patients who were naïve to or had experience with HCV therapy. Data with boceprevir in HIV-HCV-coinfected patients are currently lacking; however, initial data on drug-drug interactions between boceprevir and antiretrovirals have become available. Resistance to boceprevir has been evaluated in trials as well, although more data are needed in this area. The most common adverse events with boceprevir included anemia and dysgeusia. Based on available data, boceprevir is one of the promising novel direct-acting antiviral agents that will likely reshape the treatment of patients with HCV infection.

Important Drug-Drug Interactions in HIV-Infected Persons on Antiretroviral Therapy: An Update on New Interactions Between HIV and Non-HIV Drugs

Advances in antiretroviral therapy have turned HIV into a chronic, manageable disease. Patients often require treatment for co-morbid conditions as well as HIV, and consequently, pharmacokinetic interactions between antiretrovirals (ARVs) and other drug classes are an increasing concern. Protease inhibitors and non-nucleoside reverse transcriptase inhibitors are involved in the CYP450 or other transporter systems, and may be associated with higher risk of clinically significant drug interactions. One reverse transcriptase inhibitor, abacavir, has demonstrated weak inhibition of CYP3A4, 2D6 and 2C9 in vitro, but is not associated with any clinically significant interactions involving the CYP450 system. The integrase inhibitor raltegravir is not involved in the CYP450 system, and may be a suitable option to use when trying to minimize interactions with other drug classes. This review summarizes recently published data on clinically significant drug interactions between ARVs and other drug classes including antineoplastics, immunosuppressant transplant drugs, directly acting antivirals for hepatitis C, antifungals, antimalarials, corticosteroids, psychotropics, hormonal contraceptives, anticoagulants, drugs for pulmonary hypertension, and herbal products. In situations of suspected or potential interactions, close monitoring is warranted, and dose adjustments or substitutions may be required.

Boceprevir and personalized medicine in hepatitis C virus infection

Boceprevir was the first agent, along with telaprevir, of a novel class of direct-acting antivirals that entered clinical practice for the treatment of chronic hepatitis C. Boceprevir is an antiprotease that directly blocks hepatitis C virus (HCV) replication. Two studies in patients with HCV genotype 1 infection have shown that addition of boceprevir to the standard of care, ie, pegylated interferon-alfa (PEG-IFN-α) and ribavirin, markedly increased the rate of sustained virological response. A sustained virological response was obtained in about 70% of patients who had never been treated, as well as in 69%-75% and 40% of previous relapsers and nonresponders to PEG-IFN-α-ribavirin, respectively. Side effects were observed in almost all treated patients. Anemia, the most frequent adverse event related to administration of boceprevir, occurred in about 50% of patients. The decision to add boceprevir to the standard of care is made on an individual basis, and takes into account the prognosis of the liver disease, the efficacy of therapy, as it could be at best predicted, and the side effects that may arise, taking into account the comorbidities of the patient. Ultimately, the treatment must be accepted by the patient, who should fully understand the benefits and risks. Boceprevir trials were designed with the concept of individualized and response-guided therapy which establishes treatment decisions on how rapidly patients respond to treatment. Individualized therapy for chronic hepatitis C is based on patient and viral characteristics to make the best choice about whether a person will benefit from therapy and to evaluate on-treatment predictors of response to shorten therapy in patients with a rapid response as well as in patients who did not respond sufficiently to expect HCV eradication. This review focuses on the main results obtained so far, their impact on the treatment of patients with chronic hepatitis C, and potential therapeutic perspectives.

Boceprevir: a protease inhibitor for the treatment of hepatitis C

BACKGROUND

Boceprevir is a protease inhibitor indicated for the treatment of chronic hepatitis C virus (HCV) genotype 1 infection in combination with peginterferon and ribavirin for treatment-naive patients and those who previously failed to improve with interferon and ribavirin treatment.

OBJECTIVE

This article provides an overview of the mechanism of action, pharmacologic and pharmacokinetic properties, clinical efficacy, and tolerability of boceprevir.

METHODS

Relevant information was identified through a search of PubMed (1990-July 2012), EMBASE (1990-July 2012), International Pharmaceutical Abstracts (1970-July 2012), and Google Scholar using the key words boceprevir, SCH 503034, non-structural protein 3 (NS3) serine protease inhibitor, and direct-acting antiviral agent (DAA). Additional information was obtained from the US Food and Drug Administration's Web site, review of the reference lists of identified articles, and posters and abstracts from scientific meetings.

RESULTS

Clinical efficacy of boceprevir was assessed in 2 Phase III trials, Serine Protease Inhibitor Therapy-2 (SPRINT-2) for treatment-naive patients and Retreatment with HCV Serine Protease Inhibitor Boceprevir and PegIntron/Rebetol 2 (RESPOND-2) for treatment-experienced patients. In SPRINT-2, patients were randomized to receive peginterferon + ribavirin (PR) or peginterferon + ribavirin + boceprevir (PRB); duration of boceprevir therapy varied from 24, 32, to 44 weeks on the basis of HCV RNA results. The primary endpoint was achievement of sustained virologic response (SVR; lower limit of detection, 9.3 IU/mL). The addition of boceprevir was shown to be superior, with overall SVR rates ranging from 63% to 66% compared with 38% with PR (P < 0.001). Results of SVR in SPRINT-2 were also reorganized to monitor SVRs in black and non-black patients. Treatment-experienced patients were assessed in RESPOND-2; however, null responders were excluded. Patients were again randomized to PR or PRB; duration of boceprevir therapy varied from 32 to 44 weeks on the basis of HCV RNA results. SVR was significantly higher in patients receiving boceprevir (59%-66% vs 21% with PR; P < 0.001). This benefit was seen in both previous nonresponders (SVR, 40%-52% vs 7% with PR), as well as previous relapsers (SVR, 69%-75% vs 29% with PR). Importantly, SVR could be attained with a shortened course of therapy in almost one half of all treated patients in SPRINT-2 (44%) and RESPOND-2 (46%).

CONCLUSIONS

Boceprevir was well tolerated in clinical trials and a welcomed addition to our HCV armamentarium.

Practical management of boceprevir and immunosuppressive therapy in liver transplant recipients with hepatitis C virus recurrence

Hepatitis C virus (HCV) recurrence is the most important complication in HCV liver transplant patients. Boceprevir with pegylated interferon and ribavirin (PegIFN/RBV) enabled improvement in sustained virological response rates of patients with genotype 1 HCV. Boceprevir interacts with immunosuppressive therapy (IT) by inhibiting the cytochrome P450 3A enzyme. Our aim was to study interactions and assess the safety of boceprevir in the context of HCV recurrence. Boceprevir (800 mg three times a day) initiated after a 4-week lead-in phase was associated with cyclosporine (three patients), tacrolimus (two patients), and everolimus (one patient) in five liver transplant patients with genotype 1 HCV infection who experienced HCV recurrence. The mean follow-up period after HCV therapy was 14.8 ± 3.1 weeks. Estimated oral clearances of IT decreased on average by 50%, requiring reduced dosing regimens. Anemia occurred in all patients, with a mean fall in hemoglobin levels between baseline and week 12 of 3.12 ± 2.27 g/dl. All patients required administration of β-erythropoietin (n = 5), three needed ribavirin dose reduction, and one needed a blood transfusion. A virological response was observed in all patients (mean HCV viral load [HVL] decrease at week 12, 6.64 ± 0.35 log(10) IU/ml). These preliminary results in liver transplant patients with HCV recurrence demonstrate the feasibility and safety of coadministration of boceprevir and IT.

Liver kidney microsomal type 1 antibodies reduce the CYP2D6 activity in patients with chronic hepatitis C virus infection

Liver kidney microsomal type 1 (LKM-1) antibodies have been shown to decrease the CYP2D6 activity in vitro and are present in a minority of patients with chronic hepatitis C infection. We investigated whether LKM-1 antibodies might reduce the CYP2D6 activity in vivo. All patients enrolled in the Swiss Hepatitis C Cohort Study and tested for LKM-1 antibodies were assessed (n = 1723): 10 eligible patients were matched with patients without LKM-1 antibodies. Patients were genotyped for CYP2D6 variants to exclude individuals with a poor metabolizer genotype. CYP2D6 activity was measured by a specific substrate using the dextromethorphan/dextrorphan metabolic ratio to classify patients into four activity phenotypes. All patients had a CYP2D6 extensive metabolizer genotype. The observed phenotype was concordant with the CYP2D6 genotype in most LKM-negative patients, whereas only three LKM-1 positive patients had a concordant phenotype (six presented an intermediate and one a poor metabolizer phenotype). The median DEM/DOR ratio was sixfold higher in LKM-1 positive than in LKM-1 negative patients (0.096 vs. 0.016, P = 0.004), indicating that CYP2D6 metabolic function was significantly reduced in the presence of LKM-1 antibodies. In chronic hepatitis C patients with LKM-1 antibodies, the CYP2D6 metabolic activity was on average reduced by 80%. The impact of LKM-1 antibodies on CYP2D6-mediated drug metabolism pathways warrants further translational studies.

A human monoclonal antibody targeting scavenger receptor class B type I precludes hepatitis C virus infection and viral spread in vitro and in vivo

Endstage liver disease caused by chronic hepatitis C virus (HCV) infection is the leading indication for liver transplantation in the Western world. However, immediate reinfection of the grafted donor liver by circulating virus is inevitable and liver disease progresses much faster than the original disease. Standard antiviral therapy is not well tolerated and usually ineffective in liver transplant patients, whereas anti-HCV immunotherapy is hampered by the extreme genetic diversity of the virus and its ability to spread by way of cell-cell contacts. We generated a human monoclonal antibody against scavenger receptor class B type I (SR-BI), monoclonal antibody (mAb)16-71, which can efficiently prevent infection of Huh-7.5 hepatoma cells and primary hepatocytes by cell-culture-derived HCV (HCVcc). Using an Huh7.5 coculture system we demonstrated that mAb16-71 interferes with direct cell-to-cell transmission of HCV. Finally we evaluated the in vivo efficacy of mAb16-71 in "human liver urokinase-type plasminogen activator, severe combined immune deficiency (uPA-SCID) mice" (chimeric mice). A 2-week anti-SR-BI therapy that was initiated 1 day before viral inoculation completely protected all chimeric mice from infection with serum-derived HCV of different genotypes. Moreover, a 9-day postexposure therapy that was initiated 3 days after viral inoculation (when viremia was already observed in the animals) suppressed the rapid viral spread observed in untreated control animals. After cessation of anti-SR-BI-specific antibody therapy, a rise of the viral load was observed.

CONCLUSION

Using in vitro cell culture and human liver-chimeric mouse models, we show that a human mAb targeting the HCV coreceptor SR-BI completely prevents infection and intrahepatic spread of multiple HCV genotypes. This strategy may be an efficacious way to prevent infection of allografts following liver transplantation in chronic HCV patients, and may even hold promise for the prevention of virus rebound during or following antiviral therapy.