Interferon treatment for thrombocytopenia associated with chronic HCV infection

Thrombocytopenia is commonly seen in patients with chronic liver disease, due mainly to hypersplenism secondary to portal hypertension. We report a case of chronic hepatitis C admitted with thrombocytopenia of unknown cause. The patient s symptoms and platelet count improved markedly with interferon treatment. We conclude that interferon treatment in chronic C hepatitis may improve HCV-induced thrombocytopenia.     

The effect of treatment with a protease inhibitor on mycobacterial infection

Mycobacterial infection occurs frequently in patients that receive protease inhibitors, which are drugs used to treat AIDS, but are known for metabolic effects. Proteases of microbial antigens have been recognized as important regulators of host inflammation and cellular response. To evaluate protease inhibitor effect on a mycobacterial infection, a pilot animal model was established. Mycobacterium bovis (bacillus Calmette-Guerin, or BCG) infection was compared in rats that received ritonavir and those that did not. Tissues and serum from one drug-treated and one control were analyzed weekly. Fewer acid-fast bacilli (AFBs) were consistently found in the drug-treated group by 3 separate measures: culture of tissue homogenates on solid media, tissue granuloma counts on organ sections, and staining of tissues for AFBs. Possible mechanisms of the observed relative resistance to BCG infection in ritonavir-treated rats were explored, by evaluating M. bovis cell wall lipids and proteins and by measuring infection-related cytokines in treated and control animals.     

Impact of HCV protease-inhibitor-based triple therapy for chronic HCV genotype 1 infection

Boceprevir and telaprevir are the first HCV protease inhibitors to be approved for the treatment of chronic hepatitis C genotype 1 infection. These drugs must be used in combination with pegylated interferon plus ribavirin (P/R) to maximize efficacy and prevent the emergence of resistance-associated variants (RAVs). In randomized, placebo-controlled international studies in treatment-naive and previously treated HCV patients, treatment with either boceprevir- or telaprevir-based triple therapy regimens significantly increased sustained virological response rates compared with placebo plus P/R. Protease inhibitors have the potential, not only to significantly increase cure rates among patients with genotype 1 infection, but also to reduce the duration of treatment for patients who have an extended rapid virological response. Boceprevir is associated with an increased incidence of anaemia and dysgeusia and telaprevir is associated with an increased incidence of rash and anaemia. The emergence of RAVs was associated with an increased risk of virological failure in clinical studies. Although these new drugs bring significant promise, it remains unclear if all genotype 1 patients will need triple therapy. Here, we review some of the complexities uncovered and controversies highlighted by the introduction of HCV protease inhibitors.     

Darunavir: an effective protease inhibitor for HIV-infected patients

Darunavir is a new-generation nonpeptidic HIV protease inhibitor (PI), used with low doses of ritonavir for pharmacologic enhancement (boosting). It has demonstrated potent activity against multidrug-resistant HIV, with a robust resistance profile and a distinct set of mutations. In heavily treatment-experienced patients with HIV infection, darunavir administered twice daily with ritonavir has shown higher rates of efficacy than the control PI. In less treatment-experienced patients, boosted darunavir was noninferior to boosted lopinavir. In treatment-naive patients, boosted darunavir administered once daily was noninferior to boosted lopinavir, and showed higher virologic and immunological response rates in patients with high baseline viral load and low baseline CD4(+) cell counts. Monotherapy with boosted darunavir is an acceptable option in some specific conditions. Boosted darunavir was generally well tolerated, with lower incidence of diarrhea and a more favorable lipid profile than boosted lopinavir in treatment-naive patients.     

Evaluation of operational chronic infection endpoints for HCV vaccine trials

Hepatitis C virus (HCV) is a leading cause of chronic liver disease. The natural history of HCV infection is heterogeneous, and a person infected with HCV can clear the virus or progress to a chronic infection. The chronic infection can remain asymptomatic for decades before the development of liver cirrhosis and/or carcinoma. Currently, there are no assays that can differentiate a transient infection (an acute infection that would clear) from a chronic infection, and serial HCV RNA testing is used to operationally define chronic hepatitis C (e.g. detectable HCV over 6 months). Therefore, HCV vaccine trial planning can benefit from the assessment of the endpoint candidates that are aimed at the chronic infection. Operationally defined endpoints based on the virological tests at study visits have been previously studied in the context of human papillomavirus (HPV) vaccine trials. However, HCV natural history is different from HPV, requiring separate considerations. In this work, several definitions of chronic infection that are based on the periodically observed HCV RNA statuses are evaluated, using a multi-state, time-homogeneous Markov model for transient and chronic infections under various infection settings. Our results show some inflation in the type I error in the log-rank test on the vaccine efficacy against chronic infections in the presence of vaccine efficacy related to transient infections. A type I error up to almost four times the planned rate of 5% is observed in one setting. Overall, simple operational endpoints yield higher power than more complex endpoints, but the simplest endpoint is most affected by the type I error inflation and misclassification error due to the assay imperfection.     

Therapeutic advances: protease inhibitors for the treatment of HIV-1 infection

Background: Anti-retroviral treatment of human immunodeficiency virus (HIV) infection is undergoing great changes, brought about by a better understanding of the disease pathology. One of the most recent advances has been the introduction of the protease inhibitors, reversible inhibitors of HIV aspartic protease. Published data on the clinical efficacy of these drugs are limited, but preliminary results suggest that, in combination with one or more nucleoside analogues, they represent an important advance in the treatment of patients with advanced HIV infection. The adverse effects and potential for drug interactions, together with the additional cost associated with prescribing these drugs, mean that careful selection and supervision of these patients is imperative. Aim: To present an up-to-date review of the three most recently introduced protease inhibitors. Methods: Based on a review of the literature, abstracts from relevant meetings and information from the pharmaceutical companies. Content: A review including background data on HIV infection and the treatment options. Detailed information on ritonavir, saquinavir and indinavir. Conclusions: These new drugs are useful additions to the therapeutic current aims for the treatment of HIV infection. They need to be used under close supervision by specialists.     

A cysteine protease inhibitor cures Chagas' disease in an immunodeficient-mouse model of infection

Chagas' disease, caused by the parasite Trypanosoma cruzi, remains the leading cause of cardiopathy in Latin America with about 12 million people infected. Classic clinical manifestations derive from infection of muscle cells leading to progressive cardiomyopathy, while some patients develop megacolon or megaesophagus. A very aggressive clinical course including fulminant meningoencephalitis has been reported in patients who contract Chagas' disease in the background of immunodeficiency. This includes patients with human immunodeficiency virus infection as well as patients receiving immunosuppressive therapy for organ transplant. Currently, only two drugs are approved for the treatment of Chagas' disease, nifurtimox and benznidazole. Both have significant limitations due to common and serious side effects as well as limited availability. A promising group of new drug leads for Chagas' disease is cysteine protease inhibitors targeting cruzain, the major protease of T. cruzi. The inhibitor N-methyl-Pip-F-homoF-vinyl sulfonyl phenyl (N-methyl-Pip-F-hF-VS phi) is in late-stage preclinical development. Therefore, the question arose as to whether protease inhibitors targeting cruzain would have efficacy in Chagas' disease occurring in the background of immunodeficiency. To address this question, we studied the course of infection in recombinase-deficient (Rag1(-/-)) and normal mice infected with T. cruzi. Infections localized to heart and skeletal muscle in untreated normal animals, while untreated Rag1(-/-) mice showed severe infection in all organs and predominantly in liver and spleen. Treatment with the dipeptide N-methyl-Pip-F-hF-VS phi rescued immunodeficient animals from lethal Chagas' infection. The majority (60 to 100%) of inhibitor-treated Rag1(-/-) mice had increased survival, negative PCR, and normal tissues by histopathological examination.     

Mutations conferring resistance to a hepatitis C virus (HCV) RNA-dependent RNA polymerase inhibitor alone or in combination with an HCV serine protease inhibitor in vitro

Compounds A-782759 (an N-1-aza-4-hydroxyquinolone benzothiadiazine) and BILN-2061 are specific anti-hepatitis C virus (HCV) agents that inhibit the RNA-dependent RNA polymerase and the NS3 serine protease, respectively. Both compounds display potent activity against HCV replicons in tissue culture. In order to characterize the development of resistance to these anti-HCV agents, HCV subgenomic 1b-N replicon cells were cultured with A-782759 alone or in combination with BILN-2061 at concentrations 10 times above their corresponding 50% inhibitory concentrations in the presence of neomycin. Single substitutions in the NS5B polymerase gene (H95Q, N411S, M414L, M414T, or Y448H) resulted in substantial decreases in susceptibility to A-782759. Similarly, replicons containing mutations in the NS5B polymerase gene (M414L or M414T), together with single mutations in the NS3 protease gene (A156V or D168V), conferred high levels of resistance to both A-782759 and BILN-2061. However, the A-782759-resistant mutants remained susceptible to nucleoside and two other classes of nonnucleoside NS5B polymerase inhibitors, as well as interferon. In addition, we found that the frequency of replicons resistant to both compounds was significantly lower than the frequency of resistance to the single compound. Furthermore, the dually resistant mutants displayed significantly reduced replication capacities compared to the wild-type replicon. These findings provide strategic guidance for the future treatment of HCV infection.     

Ximelagatran: an oral direct thrombin inhibitor

OBJECTIVE: To present the chemistry, pharmacology, and pharmacokinetics of ximelagatran, an oral direct thrombin inhibitor (DTI), and to review available comparative clinical trial data evaluating its efficacy and safety relative to other antithrombotic agents in the prevention and treatment of thromboembolism. DATA SOURCES: A search of the PubMed and Cochrane databases (1995-August 2004), supplemented by a manual search of article bibliographies, conference abstracts, and data on file from the manufacturer, was conducted. Key search terms were ximelagatran, melagatran, H376/95, and direct thrombin inhibitors. STUDY SELECTION AND DATA EXTRACTION: Pertinent information from available clinical trials, including study design, patient demographics, dosing regimens, anticoagulant comparators, methods for evaluating effectiveness, treatment outcomes, adverse events, and pharmacokinetic and pharmacodynamic evaluations, was extracted. DATA SYNTHESIS: Ximelagatran is an orally administered DTI under development for use in the treatment of venous thromboembolism (VTE), long-term prevention of a second VTE event, stroke secondary to atrial fibrillation, prevention of VTE after orthopedic procedures, and recurrent ischemic events after acute myocardial infarction. CONCLUSIONS: Ximelagatran, in twice-daily doses of 24 or 36 mg, is an alternative to low-molecular-weight heparins or warfarin in thromboprophylaxis following orthopedic knee replacement, atrial fibrillation, or initial treatment of VTE. Improved outcomes versus placebo were seen in the long-term prevention of VTE in patients who completed an initial 6 months of treatment. Liver-related effects need further clarification.     

Elastography assessment in patients with chronic HCV infection

Introduction: Liver fibrosis (LB) assessment plays an important role in hepatology. A common characteristic of all chronic liver diseases is the occurrence and progression of fibrosis towards cirrhosis. Besides its plain interest for prognosis purposes, determining the fibrosis reveals the natural history of the disease and the risk factors associated with its progression to guide the antifibrotic action of different treatments. Discussion: Today, in clinical practice there are three available methods for the evaluation of LB. Biopsy, which is still considered as the ‘gold standard’ method. Serological markers and their mathematical combination are suggested in the last years in alternative to LB. More recently, transient elastography (TE) was proposed. TE is a simple and noninvasive method for measuring liver stiffness. This technique is based on the progression speed of an elastic shear wave within the liver. Conclusions: Currently, there are just a few studies capable of evaluating the TE effectiveness in chronic liver diseases, mainly in patients infected with hepatitis C virus (HCV). Its application must also be studied in the monitoring of patients suffering from chronic HCV infection and subjected to a treatment that can modify their degree of liver fibrosis. The results of TE must be interpreted according to the clinical background of the specialist.     

Developments in the treatment of HCV genotype 3 infection

ABSTRACT

Introduction: Unlike other hepatitis C virus (HCV) genotypes (GTs), patients infected with GT3 are associated with an increased risk of accelerated liver disease progression. Although early immuno-modulator therapies yielded moderate sustained virologic response (SVR) rates, treatment of GT3 patients has proven more challenging in the era of direct-acting antivirals (DAAs).

Areas covered: The review provides an overview of the evolution of therapies against GT3 since the approval of the first immunomodulatory agent nearly 30 years ago.

Expert opinion: A greater choice of treatment options is now available for HCV GT3-infected patients. In treatment-naïve patients with or without compensated cirrhosis, SVR rates are comparably high approaching 100% irrespective of treatment option. For treatment-experienced patients, choosing the right therapy is important, especially for those with advanced liver disease. For the few patients who fail with multiple persistent highly resistant DAA substitutions, retreatment options are limited. Additional real-world treatment comparisons are required to confirm differences in SVR in these more difficult-to-treat patients. This also includes patients infected with GT3 subtypes such as GT3b where multiple DAA-resistant substitutions occur naturally. In the absence of new drugs with non-overlapping drug-resistant profiles, an interferon-based therapy may still be beneficial in select patient populations with high-level multiple DAA-resistant substitutions.     

Potential role of RNAi in the treatment of HCV infection

Chronic HCV infection is a leading cause of chronic hepatitis and its sequelae, liver cirrhosis and hepatocellular carcinoma. Current therapeutic options are limited, associated with significant adverse effects and costly. Accordingly, there is strong impetus to develop novel therapeutic strategies that act through alternate mechanisms. RNAi has been widely used for the analysis of gene function and represents a potentially promising approach for the treatment of HCV infection. siRNAs are short RNA duplexes approximately 21 nts long. When introduced into mammalian cells, siRNA can silence specific gene expression. Although efficient suppression of HCV replicon RNA in cell culture has been demonstrated with siRNAs, there is much work to be done to improve delivery, limit off-target effects and minimize development of virus resistance. Here, we review the use of RNAi as a tool to inhibit HCV gene expression and discuss the potential advantages and obstacles for this new potential therapeutic approach against HCV infection.