Metabolism of Direct-acting Antiviral Agents (DAAs) in Hepatitis C Therapy: A Review of the Literature

BACKGROUND

Hepatitis C virus (HCV) infection is still one of the leading causes of chronic liver disease, with chronically infected making up approximately 1% of the global population. Of those infected, 70% (55-85%) will develop chronic HCV infection. Chronic HCV infection causes substantial morbidity and mortality, with complications including cirrhosis, end-stage liver disease, hepatocellular carcinoma, and eventually death.

OBJECTIVE

Therapeutic options for chronic HCV infection have evolved dramatically since 2014, with a translation from pegylated interferon and ribavirin (associated with suboptimal cure and high treatment-related toxicity) to oral direct-acting antiviral treatment. There are four classes of direct-acting antivirals which differ by their mechanism of action and therapeutic target. They are all pointed to proteins that form the cytoplasmic viral replication complex. Multiple studies have demonstrated that direct-acting antiviral therapy is extremely well tolerated, highly efficacious, with few side effects.

METHODS

We performed an indexed MEDLINE search with keywords regarding specific direct-acting antiviral regimes and their pharmacokinetics, drug-drug interactions, and metabolism in specific settings of pregnancy, lactation, liver cirrhosis, liver transplantation and HCC risk, kidney failure and kidney transplantation.

RESULTS

We present a comprehensive overview of specific direct-acting antiviral metabolism and drug-drug interaction issues in different settings.

CONCLUSION

Despite its complex pharmacokinetics and the possibility of drug-drug interactions, direct-acting antivirals are highly efficacious in providing viral clearance, which is an obvious advantage compared to possible interactions or side effects. They should be administered cautiously in patients with other comorbidities, and with tight control of immunosuppressive therapy.

Noninvasive markers of liver steatosis and fibrosis after liver transplantation - Where do we stand?

In the last two decades, advances in immunosuppressive regimens have led to fewer complications of acute rejection crisis and consequently improved short-term graft and patient survival. In parallel with this great success, long-term post-transplantation complications have become a focus of interest of doctors engaged in transplant medicine. Metabolic syndrome (MetS) and its individual components, namely, obesity, dyslipidemia, diabetes, and hypertension, often develop in the post-transplant setting and are associated with immuno-suppressive therapy. Nonalcoholic fatty liver disease (NAFLD) is closely related to MetS and its individual components and is the liver manifestation of MetS. Therefore, it is not surprising that MetS and its individual components are associated with recurrent or "de novo" NAFLD after liver transplantation (LT). Fibrosis of the graft is one of the main determinants of overall morbidity and mortality in the post-LT period. In the assessment of post-LT steatosis and fibrosis, we have biochemical markers, imaging methods and liver biopsy. Because of the significant economic burden of post-LT steatosis and fibrosis and its potential consequences, there is an unmet need for noninvasive methods that are efficient and cost-effective. Biochemical scores can overestimate fibrosis and are not a good method for fibrosis evaluation in liver transplant recipients due to frequent post-LT thrombocytopenia. Transient elastography with controlled attenuation parameter is a promising noninvasive method for steatosis and fibrosis. In this review, we will specifically focus on the evaluation of steatosis and fibrosis in the post-LT setting in the context of de novo or recurrent NAFLD.

Relationship between coffee consumption, sleep duration and smoking status with elastographic parameters of liver steatosis and fibrosis; controlled attenuation parameter and liver stiffness measurements

AIM

our aim was to explore the association between life habits and the controlled attenuation parameter (CAP) and liver stiffness measurements (LSM) as the surrogate markers of liver steatosis and fibrosis in a large cohort of non-alcoholic fatty liver disease (NAFLD) patients.

METHODS

In this prospective, cross-sectional study we had analysed 1998 patients with diagnosed NAFLD. Sleeping duration was categorised in three groups: short (S) (<6 hours), moderate (M) (6-8 hours) and long (L) (>8 hours) sleep duration. Coffee drinking was categorized into no (0), moderate (1-2) and frequent (≥3) consumption (in cups/day). Smoking was categorised as yes versus no.

RESULTS

Frequent coffee consumers had the lowest prevalence of obesity, hypertension, dyslipidaemia and diabetes. Furthermore, coffee non-consumers had highest values of hepatic enzymes, CAP and LSM. Moderate sleep duration was associated with lower values of CAP and LSM. Coffee consumption was associated with lower CAP in all the multivariate models (CAP unadjusted and model 1, 2 and 3), with largest effect in most frequent coffee consumers (≥3, model 3). Also, most frequent coffee consumers were associated with lower LSM in unadjusted model, model 1 and 2, while this was not the case for model 3 and those who consumed 1-2 cups of coffee per day. Reduced sleeping was confirmed as risk factor for elevated CAP in most of the models (unadjusted and model 1 and 2). Also, negative association of LSM was also confirmed in unadjusted model and model 2. Patients which slept 6-8 hours per day were mostly associated with lower CAP and LSM. Smoking status was not associated with CAP or LSM values.

CONCLUSION

Coffee consumption has beneficial effect on CAP and LSM and this effect is dose dependent since and independent of a variety of relevant confounders. We have shown that moderate sleep duration has also beneficial effect on CAP and LSM.

Accuracy of Controlled Attenuation Parameter and Liver Stiffness Measurement in Patients with Non-alcoholic Fatty Liver Disease

We evaluated the diagnostic accuracy of the controlled attenuation parameter (CAP) and liver stiffness measurements (LSM) measured with either an M or XL probe against liver biopsy (LB) in patients with non-alcoholic fatty liver disease (NAFLD). This study was a cross-sectional prospective study that included 179 NAFLD patients. With a cutoff value for CAP ≥345, we can exclude significant steatosis in 87% (79.4%-92.5%) of our population. With respect to the LSM, the highest accuracy was obtained for F ≥ F3 (area under the receiver operating characteristic curve [AUROC] = 0.98) and F = F4 (AUROC = 0.98). In a multivariable linear regression model, significant predictors influencing LSM were fibrosis stage (β = 2.6, p < 0.001) as a positive predictor and lobular inflammation (β = -0.68, p = 0.04) as a negative predictor, without significant influence after adjustment for CAP and probe type. We found that CAP is a satisfactory method for excluding advanced steatosis, while LSM is a good non-invasive marker for the exclusion of fibrosis.

Screening for nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus using transient elastography - a prospective, cross sectional study

AIM

To investigate the prevalence and severity of nonalcoholic fatty liver disease (NAFLD) in patients with diabetes mellitus type 2 (T2DM), based on increased controlled attenuation parameter (CAP) and liver stiffness measurements obtained by transient elastography. In addition, we aimed to identify parameters that correlate with increased elastographic parameters of steatosis and fibrosis to provide a better indication when a patient with T2DM should be screened for NAFLD.

METHODS

We conducted prospective, cross-sectional study of 679 consecutive adult patients with diagnosed T2DM mean age 65.2±11.6. NAFLD was defined by transient elastography. In 105 patients a percutaneous liver biopsy (LB) was done.

RESULTS

The prevalence of NAFLD based on transient elastography was 83.6%. Independent factors associated with increased CAP were higher body mass index, longer T2DM duration, higher serum triglyceride, lower levels of vitamin D, higher C-reactive protein, and higher HOMA-IR. The prevalence of moderate liver fibrosis was 26.9% and advanced liver fibrosis 12.6%. Independent factors associated with moderated fibrosis based on elastography were higher body mass index and higher levels of alanine aminotransferase (ALT), while independent factors associated with advanced fibrosis were female gender, higher body mass index, higher levels of ALT, gama-glutamil transferase and C-reactive protein. Sixty-four (60.9%) of 105 patients with LB had NAFLD activity score ≥5. Regarding the presence and stages of fibrosis based on LB, moderate fibrosis was found in 29.5% of patients, while 29.5% had advanced fibrosis and 6.7% cirrhosis.

CONCLUSION

This study supports more aggressive screening for NAFLD and fibrosis in patients with T2DM.

Non-alcoholic fatty liver disease and transient elastography

Nonalcoholic fatty liver disease (NAFLD) is a serious condition that can lead to fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD is associated with metabolic syndrome (MetS) and all of its components. According to data, around 25-30% of population has NAFLD. Giving the growing incidence of MetS, obesity and diabetes mellitus type 2, NAFLD related terminal-stage liver disease is becoming prevailing indication for liver transplantation. In order to prevent terminal stage of this disease, it is crucial to determine those that are in risk group, to modify their risk factors and monitor their potential progression. In the absence of other causes of chronic liver disease, the prime diagnosis of NAFLD in daily clinical practice includes anamnesis, laboratory results (increased levels of aminotransferases and gammaglutamil transferases) and imaging methods. The biggest challenge with NAFLD patients is to differentiate simple steatosis from nonalcoholic steatohepatitis, and detection of fibrosis, that is the main driver in NAFLD progression. The gold standard for NAFLD diagnosis still remains the liver biopsy (LB). However, in recent years many noninvasive methods were invented, such as transient elastography (TE). TE (FibroScan®, Echosens, Paris, France) is used for diagnosis of pathological differences of liver stiffness measurement (LSM) and controlled attenuation parameter (CAP). Investigations in the last years have confirmed that elastographic parameters of steatsis (CAP) and fibrosis (LSM) are reliable biomarkers to non-invasively assess liver steatosis and fibrosis respectively in NAFLD patients. A quick, straightforward and non-invasive method for NAFLD screening in patients with MetS components is TE-CAP. Once diagnosed, the next step is to determine the presence of fibrosis by LSM which should point out high risk patients. Those patients should be referred to hepatologists. LB may be avoided in a substantial number of patients if TE with CAP is used for screening.