Ribavirin: How Does it Work and is it Still Needed?

Inosine monophosphate dehydrogenase 2 (IMPDH2) modulates response to therapy and chemo-resistance in triple negative breast cancer

Triple negative breast cancer (TNBC) is one of the deadliest subtypes of breast cancer, whose high frequency of relapse is often due to resistance to chemotherapy. Here, we identify inosine monophosphate dehydrogenase 2 (IMPDH2) as a contributor to doxorubicin resistance, in multiple TNBC models. Analysis of publicly available datasets reveals elevated IMPDH2 expression to associate with worse overall TNBC prognosis in the clinic, including lower recurrence-free survival post adjuvant/neoadjuvant therapy. Importantly, both genetic depletion and pharmacological inhibition of IMPDH2 leads to reduction of pro-tumorigenic phenotypes in multiple doxorubicin-resistant TNBC models, both in vitro and in vivo. Overall, we propose IMPDH2 as a novel vulnerability that could be leveraged therapeutically to suppress and/or prevent the growth of chemo-resistant lesions.

Effects of Mild and Moderate Renal Impairment on Ombitasvir, Paritaprevir, Ritonavir, Dasabuvir, and Ribavirin Pharmacokinetics in Patients with Chronic HCV Infection

BACKGROUND AND AIMS

Ombitasvir, paritaprevir (given with low-dose ritonavir), and dasabuvir are direct-acting antivirals (DAAs) used with or without ribavirin for the treatment of chronic hepatitis C virus (HCV) infection. The objective of this analysis was to evaluate the effect of renal function as determined by creatinine clearance (CrCL) on the pharmacokinetics of the DAAs, ritonavir, and ribavirin in HCV genotype 1-infected patients with or without cirrhosis.

METHODS

Total exposure, measured by area under the plasma concentration-time curve (AUC), was generated for the DAAs, ritonavir, and ribavirin using population pharmacokinetic modeling of data (N = 2093 patients) from 6 Phase 3 studies and 1 Phase 2 study. The effect of CrCL on the AUC values of each DAA, ritonavir, and ribavirin was separately evaluated and adjusted for any significant patient-specific covariates including, age, sex, body weight, cirrhosis, and Asian race in multiple linear regression analysis. Using the final models, AUC values were predicted for patients with normal renal function (CrCL = 105 mL/min), mild renal impairment (CrCL = 75 mL/min) and moderate renal impairment (CrCL = 45 mL/min).

RESULTS

CrCL was not a statistically significant predictor of DAA or ritonavir AUC values. Age, sex, and cirrhosis were significant covariates for the AUC values of all the DAAs and body weight was a significant covariate for the AUC values of ombitasvir and dasabuvir. Asian race was significant only for dasabuvir. Only age and sex were statistically significant predictors for the AUC values of ritonavir. CrCL showed a significant relationship with the ribavirin AUC values, consistent with ribavirin's renal excretion. Age, sex, body weight, and cirrhosis were also significant covariates for the AUC values of ribavirin. The DAA and ritonavir AUC values were comparable (≤10 % difference) among different levels of renal function, while ribavirin AUC values were up to 17 % higher in mild/moderate renal impairment compared with normal renal function.

CONCLUSIONS

No dose adjustments are needed for the 3D regimen in HCV genotype-1 infected patients with mild or moderate renal impairment. Ribavirin doses should be adjusted for renal impairment as recommended in the ribavirin label.

Potential Liver Transplant Recipients with Hepatitis C: Should They Be Treated Before or After Transplantation?

Treatment of hepatitis C virus (HCV) with newer directly acting antivirals (DAAs) and lead to sustained viral response (SVR) in majority of patients and SVR has been documented to be associated with reversal of liver cirrhosis. The improved SVR rates and safety profiles of DAAs have led to the treatment of patients with decompensated cirrhosis awaiting liver transplantation (LT). Several clinical trials of DAAs in decompensated HCV patients have recently demonstrated SVR rates above 80%, which have been associated with significant improvements, in the Child-Pugh-Turcotte scores/or model for end-stage liver disease scores in a proportion of patients. Moreover, it has been shown that HCV RNA becomes negative after 2-4 weeks of treatment, and those who are transplanted after becoming HCV RNA negative will be have very low the risk of HCV recurrence after transplantation. Some of the patients may have reached the "point of no return" and may proceed to worsening of decomposition over time. To avoid the risk of worsening, there is an additional option of treating these patients after LT should they develop recurrent HCV infection. Currently there are no guidelines as to select patients who would benefit from treatment prior to LT as opposed to those who will be better off being treated after the transplant surgery. The article discusses a possible approach for such selection.

Treat chronic hepatitis C virus infection in decompensated cirrhosis - pre- or post-liver transplantation? the ironic conundrum in the era of effective and well-tolerated therapy

The management of hepatitis C virus (HCV) infection in patients with decompensated cirrhosis has evolved dramatically over the past few years mainly due to the availability of all-oral antiviral regimens. The currently approved all-oral direct-acting antivirals (DAA) containing sofosbuvir, ledipasvir, daclatasvir and ribavirin, in various combinations, have shown to be safe and effective in patients with decompensated cirrhosis with sustained virological response (SVR) rates nearly comparable to those with well-compensated liver disease. Unique issues yet remain such as the challenges with renal insufficiency, tolerability of ribavirin and risk of further hepatic decompensation with a protease inhibitor-based regimen. While most patients who achieve SVR have demonstrated improvement in hepatic synthetic function over the short course of follow, the long-term beneficial effects are unknown. Further, the baseline predictors of improvement in hepatic function have not been well delineated and thus have left us in a quandary as to what we might expect with successful therapy and thus we are at a loss to well educate our patients. The major concern, in potential liver transplant candidates, is of unintended 'harm' by achieving SVR but without improvement in hepatic function to an extent where the patients might function well. As HCV therapies are as effective in liver transplant recipients, there is a growing sentiment in some of the transplant quarters that those with decompensated liver disease and awaiting liver transplant be treated for HCV after liver transplant. This strategy would thus eliminate any concern of leaving a patient in 'no person's' land by treating HCV successfully pretransplant but not to the point of functional normalcy, while also would maintain the risk of HCC. Yet a contrarian view would be that not all patients have access to liver transplantation (LT), cannot bear the cost, have comorbidities or contraindications to LT. While the debate continues, it is essential that we develop robust predictors of improvement in liver function so that we can carefully select our patients for therapy in the context of liver transplantation.

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.

Treatment of Chronic Hepatitis C in Special Populations

The management of hepatitis C virus (HCV) infection in special populations is challenging. The efficacy and safety data of the currently approved all-oral direct-acting antiviral combinations, including sofosbuvir, ledipasvir, daclatasvir, paritaprevir/ritonavir/ombitasvir plus dasabuvir (3D), and ribavirin, is compelling for use in special HCV populations, as has recently been recommended by expert guidelines. The treatment regimens and sustained virological response rates for special populations are nearly similar to those of the general HCV population. Sofosbuvir is not recommended in patients with severe renal impairment, and simeprevir and 3D regimen are not recommended for those with decompensated liver disease.

Management of patients with hepatitis C infection and renal disease

Hepatitis C virus (HCV) infection in patients with end-stage renal disease (ESRD) is associated with more rapid liver disease progression and reduced renal graft and patients' survival following kidney transplantation. Evaluations and management of HCV in patients with renal disease are challenging. The pharmacokinetics of interferons (IFN), ribavirin (RBV) and some direct acting antiviral (DAA), such as sofosbuvir, are altered in patients with ESRD. With dose adjustment and careful monitoring, treatment of HCV in patients with ESRD can be associated with sustained virological response (SVR) rates nearly comparable to that of patients with normal renal function. DAA-based regimens, especially the IFN-free and RBV-free regimens, are theoretically preferred for patients with ESRD and KT in order to increase SVR rates and to reduce treatment side effects. However, based on the data for pharmacokinetics, dosing safety and efficacy of DAA for patients with severe renal impairment are lacking. This review will be focused on the evaluations, available pharmacologic data, and management of HCV in patients with severe renal impairment, patients who underwent KT, and those who suffered from HCV-related renal disease, according to the available treatment options, including DAA.