Feasibility of ribavirin therapeutic drug monitoring in hepatitis C

Sofosbuvir-based antiviral therapy in hepatitis C virus patients with severe renal failure

Background

Chronic hepatitis C virus (HCV) infection is the most common chronic liver disease in patients with end-stage renal disease (ESRD). Over the last few years, second-generation direct-acting antivirals have been revolutionary in the treatment of hepatitis C, and sofosbuvir (SOF) is the backbone of most modern treatment strategies. Since SOF is eliminated through the kidney, the aim of this multicentre retrospective study was to assess its antiviral efficacy and safety in HCV-infected patients with severe renal failure [including haemodialysis (HD) patients].

Methods

Fifty patients (36 males, mean age ± standard deviation 60.5 ± 7.5 years) with chronic HCV infection (G1: 28/56%, cirrhosis: 27/54%) and severe renal failure [i.e. MDRD estimated glomerular filtration rate (eGFR) <35 mL/min], including 35 on HD, were enrolled. Antiviral treatment consisted of SOF/ribavirin (RBV) (n = 7), SOF/RBV/pegylated interferon (n = 2), SOF/daclatasvir ± RBV (n = 30) or SOF/simeprevir ± RBV (n = 11) for 12 or 24 weeks. A reduced dose of SOF (400 mg three times a week or 400 mg every other day) was given to all HD patients. Initial dose of RBV (n = 12) ranged from 400 to 4200 mg/week.

Results

On an intent-to-treat-based analysis, sustained virological response rate was 86% at 12 weeks. During therapy, haemoglobin levels were not significantly modified, but recombinant erythropoietin (rEPO) dose significantly increased in patients treated with RBV. Two patients (4%) required blood transfusion. No patient had treatment discontinuation due to side effects. Dose of RBV was reduced in two patients (16.7%) during antiviral therapy. Dose of SOF was reduced in two non-HD patients because of side effects. In non-HD patients, median eGFR was not significantly modified during treatment.

Conclusions

Our results strongly suggest that SOF-based antiviral therapy, with a reduced dose of SOF, is safe and effective for the treatment of HCV patients with ESRD, including HD patients.

Efficiency and Safety of an Early Dose Adjustment of Ribavirin in Patients Infected With Hepatitis C Underexposed to the Drug and Treated With Peginterferon Ribavirin

BACKGROUND

Ribavirin exposure after the first dose (D0AUC0-4h) >1755 mcg·h·L is predictive of sustained virological response (SVR) in patients with hepatitis C treated with peginterferon and ribavirin. The aim of this study was to test the benefit of ribavirin early dose adjustment based on this target in naïve patients infected with genotype 1.

METHODS

A multicenter randomized controlled trial with two parallel groups; fixed-dose (FD) group: standard of care in 2010-2011, ie, peginterferon-α2a 180 mcg·wk and weight-based ribavirin 1000-1200 mg/d during 48 weeks; adapted-dose (AD) group: increase of ribavirin dose if D0AUC0-4h <1755 mcg·h·L.

RESULTS

A total of 221 patients were included, 110 in the AD group and 111 in the FD group with similar baseline characteristics. In the perprotocol analysis, SVR was higher in the AD group (55.1% versus 40.4%; P = 0.042), especially in patients with D0AUC0-4h <1755 mcg·h·L (54.3% versus 31.9%; P = 0.029). In the intention-to-treat analysis, the difference was not significant (50% versus 41%; P = 0.197). Ribavirin trough concentrations (C0s) at week 4 of treatment (intention-to-treat analysis) were higher in patients achieving SVR (2.06 versus 1.72 mg/L, P = 0.003). In the subgroup of patients with AUC0-4h <1755 mcg·h·L, 46% of patients with AD achieved a C0 >2.0 mg/L versus 22% of patients with FD (P = 0.013). Grade 1 anemia (but not other grades) was more frequent in the AD group (70% versus 48%, P = 0.001). The number of dose reductions or discontinuation of ribavirin was similar in both groups.

CONCLUSIONS

Early ribavirin dose adjustment increases SVR in patients underexposed to ribavirin without increasing grade II-IV anemia. Such a strategy could be useful in patients with no access to new antiviral drugs.

Concentration Monitoring of Plasma Ribavirin: Validation of a Liquid Chromatography-Mass Spectrometric Method and Clinical Sample Collection

BACKGROUND

A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for routine measurement of ribavirin concentrations in EDTA-anticoagulated plasma.

METHODS

After protein precipitation, we used a bridged ethylene hybrid (hydrophilic interaction) chromatography column, 0.1 mmol/L ammonium formate pH 3.0, and a gradient of 85%-96% acetonitrile to achieve baseline separation of ribavirin from isobaric uridine. Quantitation was assured using both primary (m/z 245.3 > 113.0) and secondary transitions (m/z 245.3 > 96.0) of the protonated species. Chromatographic separation and column washing also negated interference from major phospholipid species.

RESULTS

There was a linear relationship between concentration and response to 10 mg/L, with a minimum detectable level and a minimum level of quantitation both of 0.1 mg/L. Imprecision within the assay was <10% at 0.1 mg/L and <6% between assays for concentrations >0.4 mg/L. Bias was <4%. In clinical samples (n = 12), there was no difference in ribavirin concentrations obtained by an established liquid chromatographic assay with ultraviolet detection. Ribavirin concentrations were stable in plasma stored at room temperature for 3 days but then decreased significantly on day 7. Plasma concentrations were stable for 15 weeks at -20 °C. Concentrations in plasma separated from whole blood at room temperature fell by a median of 19.4% at 4 hours and then rose substantially (median 251% by 3 days). Dose-normalized ribavirin concentrations reached a steady state after a mean of >6 weeks treatment in 76 patients with hepatitis C.

CONCLUSIONS

A hydrophilic interaction liquid chromatography-tandem mass spectrometric method to measure ribavirin in plasma was developed. Samples for ribavirin estimation should be kept at 4 °C, separated within 2 hours of collection and stored at 4 °C before analysis, with long-term storage at -20 °C. This method was applied to a study of the ribavirin therapeutic monitoring in patients with hepatitis C.

[Not Available]

Ribavirin in combination with pegylated interferon alpha is the current treatment for chronic hepatitis C (HCV). Ribavirin presents a wide inter-individual pharmacokinetic variability and adequate exposure seems crucial for achieving sustained virologic response. Severe anaemia frequently occurred under ribavirin treatment and is a dose-dependent limiting side effect. Several studies have been carried out in HVC-infected or HIV-HCV co-infected patients to evaluate the pharmacokinetic-pharmacodynamic relationships of ribavirin. Achievement of a sustained virologic response, defined as undetectable HCV-RNA six months after the end of treatment, have been significantly associated with ribavirin concentration. A cut-off for the trough concentration of ribavirin ranging between 2-3μg/ml at week 4 has been proposed. A significant correlation has also been reported between ribavirin concentration and the extent of haemoglobin decline. A ribavirin concentration>2μg/ml is significantly associated to an increase risk of severe anaemia. Non randomized studies have shown that therapeutic drug monitoring of ribavirin improve the management of therapeutic response and haematologic toxicity. Therefore, the level of evidence of the therapeutic drug monitoring of ribavirin is recommended.

Increased Ribavirin Bioavailability Associated With Telaprevir Use in Hepatitis C Patients Treated With PEGylated -Interferon/Ribavirin/Telaprevir Triple Therapy

BACKGROUND

Anemia is more frequent in patients receiving telaprevir with PEGylated interferon/ribavirin (PEG-IFN/RBV) than in those receiving PEG-IFN/RBV alone.

OBJECTIVES

The objective was to measure the impact of telaprevir on RBV bioavailability and to assess the concomitant renal function.

MATERIALS AND METHODS

Thirty-seven hepatitis C virus (HCV) patients non-responders to a previous course of PEG-IFN/RBV therapy and re-treated with triple therapy combining PEG-IFN/RBV and telaprevir were analyzed. RBV bioavailability was measured before the triple therapy initiation, during telaprevir treatment at week (W) 4 and W8, and after telaprevir cessation (post W16). The renal function was assessed by estimating the glomerular filtration rate (eGFR).

RESULTS

At W4, RBV bioavailability, expressed as mg/L/daily dose/kg body weight, was significantly increased (median increase = 0.06 mg/L/dose/kg; P < 0.001). In parallel, the renal function was impaired with a mean eGFR decrease of -6.8 mL/minutes/1.73 m² (P = 0.109). Between W4 and W8, RBV bioavailability continued to increase (P < 0.001) but subsequently decreased slightly after telaprevir discontinuation with a concomitant restoration of the renal function (eGFR increase of 6.34 mL/minutes/1.73 m²).

CONCLUSIONS

Our results indicated a reversible increase in RBV bioavailability after telaprevir exposure, which might be linked to the impairment of the GFR. This also suggests a RBV-telaprevir pharmacological interaction, a possible source of severe anemia observed under triple therapy. These results suggest that RBV pharmacological monitoring may be clinically relevant, especially in the context of first-generation HCV protease inhibitor-based therapy.

Lower ribavirin biodisponibility in patients with HIV-HCV coinfection in comparison with HCV monoinfected patients

Background

In HIV infected patients, the impact of ribavirin (RBV) pharmacology on sustained virologic response (SVR) to hepatitis C virus (HCV) treatment has not been fully investigated. The objective of this study was to compare the early RBV plasma exposure between a population of HIV-HCV coinfected patients and an HCV monoinfected group.

Methods

Early RBV plasma exposure (expressed as Area Under the Curve (AUC) from 0 to 4 h) after a 600 mg first dose of RBV was measured in a population of HIV-HCV coinfected patients in comparison with an HCV monoinfected group. Peripheral blood samples were collected before the 600 mg RBV first dose (T0) to ensure no detectable baseline plasma RBV, and then 30 mn, 1, 2 and 4 hours after RBV intake (T0.5, T1, T2 and T4).

Results

Eighty-six patients with chronic hepatitis C entered the study among whom 23 (27%) were HIV-HCV coinfected. Coinfected patients had a significantly lower RBV-AUC _0-4h (median: 1469 μg*h/L [range 936–3677]) compared with monoinfected patients (2030 μg*h/L [851–7700]; p = 0.018). This RBV under exposure in coinfected patients persisted after normalization of AUC to RBV dose per kilogram of body weight (182 μg*h/L [110–425] versus 271 μg*h/L [82–1091], p = 0.001).

Conclusions

These results suggest that lower early bioavailability of RBV could be one of the reasons for lower SVR in HIV-HCV coinfected patients treated with pegylated interferon/RBV combination therapy. RBV plasma underexposure seems to be associated with the immunological status of the patients with lower AUC_0-4h values observed in the more immunosuppressed coinfected patients.

Multiplex liquid chromatography-tandem mass spectrometry assay for simultaneous therapeutic drug monitoring of ribavirin, boceprevir, and telaprevir

New directly acting antivirals (DAAs) that inhibit hepatitis C virus (HCV) replication are increasingly used for the treatment of chronic hepatitis C. A marked pharmacokinetic variability and a high potential for drug-drug interactions between DAAs and numerous drug classes have been identified. In addition, ribavirin (RBV), commonly associated with hemolytic anemia, often requires dose adjustment, advocating for therapeutic drug monitoring (TDM) in patients under combined antiviral therapy. However, an assay for the simultaneous analysis of RBV and DAAs constitutes an analytical challenge because of the large differences in polarity among these drugs, ranging from hydrophilic (RBV) to highly lipophilic (telaprevir [TVR]). Moreover, TVR is characterized by erratic behavior on standard octadecyl-based reversed-phase column chromatography and must be separated from VRT-127394, its inactive C-21 epimer metabolite. We have developed a convenient assay employing simple plasma protein precipitation, followed by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) for the simultaneous determination of levels of RBV, boceprevir, and TVR, as well as its metabolite VRT-127394, in plasma. This new, simple, rapid, and robust HPLC-MS/MS assay offers an efficient method of real-time TDM aimed at maximizing efficacy while minimizing the toxicity of antiviral therapy.

Pitfalls Associated with the Use of Liquid Chromatography–Tandem Mass Spectrometry in the Clinical Laboratory

BACKGROUND

Novel mass spectrometric techniques such as atmospheric pressure ionization and tandem mass spectrometry have substantially extended the spectrum of clinical chemistry methods during the past decade. In particular, liquid chromatography tandem–mass spectrometry (LC-MS/MS) has become a standard tool in research laboratories as well as in many clinical laboratories. Although LC-MS/MS has features that suggest it has a very high analytical accuracy, potential sources of inaccuracy have recently been identified.

CONTENT

The sources of inaccuracy in LC-MS/MS methods used in the routine quantification of small molecules are described and discussed. Inaccuracy of LC-MS/MS methods can be related to the process of ionization through the insource transformation of conjugate metabolites or target analytes and may also be attributable to ionization matrix effects that have a differential impact on target analytes and internal-standard compounds. Inaccuracy can also be associated with the process of ion selection, which mainly occurs when compounds from the sample matrix share mass transitions with a target analyte. In individual assays, most potential sources of inaccuracy can be controlled by sufficient LC separation–based sample workup before MS analysis.

SUMMARY

LC-MS/MS methods should undergo rigorous and systematic validation before introduction into patient care.

Stability of ribavirin concentrations depending on the type of blood collection tube and preanalytical conditions

Ribavirin pharmacokinetic and exposure effect trials based on either plasma or serum concentrations have yielded diverging results. This study aimed to compare ribavirin concentrations in serum and plasma and to investigate the influence of blood collection and preanalytical conditions on ribavirin concentration stability. Blood samples from patients with hepatitis virus C and receiving ribavirin were collected in plain (dry) tubes, in tubes containing ethylenediaminetetra-acetic acid or lithium-heparinate, in Type II Serum Separating Tubes with clot activator, or Type II lithium heparinate Plasma Separating Tubes. Different time and temperature conditions were tested before and after blood centrifugation. Ribavirin was determined using liquid chromatography-dual mass spectroscopy. Multiple-way analysis of variance was used for statistical analyses. Ribavirin concentrations showed a higher interlaboratory variability in serum than in plasma. Results were fairly stable over 2 hours in whole blood collected in dry or ethylenediaminetetra-acetic acid tubes and very stable up to 24 hours in serum or plasma kept in gel-containing tubes after immediate centrifugation. When Plasma Separating II gel tubes were kept at +4 degrees C or at ambient temperature for up to 24 hours before centrifugation, ribavirin concentrations decreased by 1% to 8% and 12% to 18%, respectively. These results suggest that blood samples should be collected in gel-containing tubes and centrifuged immediately, after which the tubes can be kept at ambient temperature for the next 24 hours. In case of clinical constraints, Plasma Separating II gel tubes can be kept at +4 degrees C for a maximum of 2 hours before centrifugation with limited impact on the measured concentrations.