Measurement of Ribavirin Plasma Concentrations by High-performance Liquid Chromatography Using a Novel Solid-phase Extraction Method in Patients Treated for Chronic Hepatitis C

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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.

Measuring ribavirin concentrations during the earliest stages of antiviral therapy for hepatitis C: potential relevance for treatment outcome

BACKGROUND

Correlations between ribavirin (RBV) concentrations and sustained virological response (SVR) to hepatitis C virus treatment have been demonstrated previously. As steady state is reached after several weeks of RBV treatment, dose modifications based on steady-state levels can only be applied relatively late in treatment, possibly too late to influence SVR rates. The authors aimed to determine whether measurement of early concentrations is useful to predict optimal steady-state RBV concentrations.

METHODS

In 61 treatment-naive genotype 1/4 patients RBV concentrations were determined in samples collected after 1, 2, 4, 8, 12, and 24 weeks of therapy. RBV concentrations were compared between responders and nonresponders; Receiver Operating Characteristic analyses were conducted to find optimal cut-off values to predict week 8 concentrations from earlier measurements.

RESULTS

Median week 8 RBV concentrations were significantly higher in patients with SVR compared with those without: 3.4 (interquartile range 2.4-3.9) versus 2.6 (interquartile range 2.0-3.5) mg/L (P < 0.05). RBV concentration at week 8 was an independent predictor of SVR [adjusted odds ratio 2.3 (95% confidence interval: 1.1-4.9; P = 0.03)]. The optimal cut-off value of week 8 RBV concentration to predict SVR was 2.20 mg/L [sensitivity 87%, specificity 40%, positive predictive value 64%, negative predictive value 71%]. Optimal cut-off values at weeks 1, 2, or 4 to predict an RBV concentration ≥2.20 mg/L at week 8 were 0.92, 1.29, and 1.67 mg/L, respectively, with positive predictive values and negative predictive values ranging from 88% to 91% and 71% to 86%, respectively.

CONCLUSIONS

RBV concentrations in the earliest stages of antiviral therapy predict therapeutic steady-state concentrations, allowing timely dose adjustments with potential implications for treatment outcome.

Development and validation of a useful UPLC-MS/MS method for quantification of total and phosphorylated-ribavirin in peripheral blood mononuclear cells of HCV+ patients

The current standard-of-care therapy in HCV consists in ribavirin (RBV) plus pegylated-interferon-α 2a or 2b and, for HCV-1 infected patients, also directly acting antivirals (DAAs). Despite the increase in the number of patients who reach sustained virological response (SVR) for HCV-1, a great inter-individual variability in the response to therapy remains. Whether new drugs are available in combination with RBV and Peg-IFN for HCV-1, the treatment of the other viral genotypes remains the same: this issue highlights the lasting importance of RBV and Peg-IFN in anti-HCV treatment. Moreover, a strong limiting factor to the usefulness of anti-HCV treatment remains the occurrence of adverse events, first of all hemolytic anemia, which have increased with the addition of DAAs, but is mainly an RBV-dependent effect. For these reasons, the monitoring of RBV exposure in the various compartments should be important. Since the routinely determination of RBV in the target cells as the hepatocytes is impracticable for of its invasiveness, the quantification in easier to obtain cells could be a good choice. In this work, we developed and validated an ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay method to quantify RBV concentrations in peripheral blood mononucleated cells (PBMCs). QCs were prepared with RBV and RBV-monophosphate (RMP). Each sample was divided into two aliquots, which undergone the same extraction procedure: one was treated with acid phosphatase to convert RBV phosphorylated metabolites into free RBV, the other one was not-treated. The extracts were analyzed with reverse-phase column with UPLC-MS/MS. Calibration curves fitted a least squares model (weighed 1/X) for ribavirin levels in a range from 0.1 ng to 200 ng (mean r(2)=0.9993). Accuracy, intra-day and inter-day precision of the methods were in accordance with FDA guidelines. Moreover, phosphorylated QCs were used to assess the correct determination of total RBV concentration. We tested this method by monitoring RBV concentrations in PBMCs from 20 HCV+ patients, receiving alpha interferon-plus RBV combination therapy. This method showed to be reliable, precise, accurate and suitable for evaluation of intracellular RBV concentrations.

Microsample analyses via DBS: challenges and opportunities

The use of DBS is an appealing approach to employing microsampling techniques for the bioanalysis of samples, as has been demonstrated for the past 50 years in the metabolic screening of metabolites and diseases. In addition to its minimally invasive sample collection procedures and its economical merits, DBS microsampling benefits from the very high sensitivity, selectivity and multianalyte capabilities of LC–MS, which has been especially well demonstrated in newborn screening applications. Only a few microliters of a biological fluid are required for analysis, which also translates to significantly reduced demands on clinical samples from patients or from animals. Recently, the pharmaceutical industry and other arenas have begun to explore the utility and practicality of DBS microsampling. This review discusses the basis for why DBS techniques are likely to be part of the future, as well as offering insights into where these benefits may be realized.

A pharmacological profile of ribavirin and monitoring of its plasma concentration in chronic hepatitis C infection

Chronic hepatitis C (CHC) infection, usually an asymptomatic infection, has long-term serious complications such as cirrhosis, hepatocellular carcinoma, and end-stage liver disease requiring liver transplantation (LT). Several novel drugs against hepatitis C which form part of 'specifically targeted antiviral therapy for hepatitis C' (STAT-C) have been developed. These include NS3/4A protease inhibitors telaprevir, boceprevir, and nucleoside/non-nucleoside polymerase inhibitors (NS5A) which hold promise for future therapy. Despite the development of new anti-hepatitis C virus (HCV) drugs, ribavirin (RBV) remains the single most important drug to prevent relapse and is frequently included among newer regimens being developed with novel small molecule anti-HCV drugs. The current approved treatment is a combination therapy of once weekly subcutaneous pegylated-interferon (PEG-IFN)-α plus body-weight-based oral RBV regimen. The most significant dose-dependent side effect of RBV is hemolytic anemia warranting dose reduction or discontinuation in severe cases compromising sustained virological response (SVR). Monitoring RBV plasma concentration has been challenging due to its peculiar pharmacokinetics and has been done to predict both efficacy and toxicity. Herein, we review the pharmacological profile of RBV and the monitoring of its plasma concentration, monitoring in renal impairment, post-LT, and human immunodeficiency virus (HIV)-HCV co-infection in patients being treated with combination therapy of PEG-IFN-α and RBV.

Variants in the ITPA gene protect against ribavirin-induced hemolytic anemia in HIV/HCV-coinfected patients with all HCV genotypes

BACKGROUND

A recent genome-wide association study reported a strong association with a single-nucleotide polymorphism (SNP) in the inosine triphosphate (ITPA) gene and hemolytic anemia in patients infected with hepatitis C virus (HCV) receiving pegylated interferon and ribavirin. We investigate these polymorphisms in a cohort of human immunodeficiency virus (HIV)/HCV-coinfected patients.

METHODS

DNA was available for 161 patients with validated outcomes. We analyzed the association between the variants and week 4 hemoglobin reduction. Anemia over the course of therapy, ribavirin (RBV) dose reduction, serum RBV level, and rapid virological response (RVR) and sustained virological response (SVR) were also investigated. Using a candidate gene approach, ITPA variants rs1127354 and rs7270101 were tested using the ABI TaqMan kit. Multivariable models were used to identify predictors of anemia.

RESULTS

A significant minority (33%) of patients were predicted to have reduced ITPase activity. The minor allele of each variant was associated with protection against week 4 anemia. In multivariable models only the genetic variants, creatinine, and zidovudine exposure remained significant. ITPase deficiency was not associated with RBV-dose reduction, RVR, or SVR.

CONCLUSIONS

This study confirms that polymorphisms in the ITPA gene are associated with protection from RBV-induced anemia in HIV/HCV-coinfected patients but not improved clinical outcomes.

Impact of IL28B polymorphisms on response to peginterferon and ribavirin in HIV–hepatitis C virus-coinfected patients with prior nonresponse or relapse

IL28B polymorphisms predict treatment response in chronic hepatitis C. However, no information exists in prior treatment failures. A total of 62 HIV/hepatitis C virus (HCV) patients who completed retreatment with peginterferon-α/ribavirin were examined, of whom 25 (40%) had been cured. Predictors of response [odds ratio, OR (95% confidence interval, CI)] were HCV genotypes 2/3 [16.1 (2.7-90.9)], prior relapse [9.6 (1.5-62.4)] and ribavirin plasma trough concentrations at week 4 [4.9 (1.3-18.4)]. IL28B-CC only predicted response in prior nonresponders carrying HCV genotypes 1/4 [25.1 (1.9-337)].

Ribavirin plasma concentration is a predictor of sustained virological response in patients treated for chronic hepatitis C virus genotype 2/3 infection

In hepatitis C virus (HCV) genotype 1 infection, the likelihood of obtaining sustained virological response (SVR) is associated with higher ribavirin exposure. Such an association has not been demonstrated for HCV genotype 2/3 infection, where a fixed 800 mg daily dosing of ribavirin is generally recommended. The primary aim of this study was to investigate the correlation between ribavirin concentration at day 29 and therapeutic response in patients with HCV genotype 2/3 infection. A total of 382 patients were randomized to 12 or 24 weeks of treatment with pegylated interferon-alfa 2a 180 μg weekly and 800 mg ribavirin daily. Trough plasma concentration of ribavirin was measured at day 29 and week 12 and the primary outcome was SVR (HCV-RNA undetectable 24 weeks after treatment). Of the 382 patients, 355 had a ribavirin concentration available at day 29. SVR was 84% among patients with a ribavirin concentration ≥2 mg/L at day 29 compared to 66% in those with concentrations <2 mg/L (P = 0.002). The corresponding figures in the 12-week treatment group were 74% and 57% (P = 0.12), and in the 24-week treatment group 91% and 75% (P = 0.02), respectively. In a multivariate analysis, ribavirin concentration at day 29 was an independent predictor of SVR (P = 0.002). In conclusion, a higher plasma ribavirin concentration is associated with an increased likelihood of achieving SVR in HCV genotype 2/3 infection. Individualization of ribavirin dosing may be helpful in improving outcome, especially in the presence of unfavourable baseline characteristics. This, however, requires evaluation in a prospective trial.

Preemptive erythropoietin plus high ribavirin doses to increase rapid virological responses in HIV patients treated for chronic hepatitis C

Chronic hepatitis C affects one-third of HIV(+) patients worldwide. High ribavirin (RBV) exposure is crucial to maximize the response to hepatitis C therapy in this population, although it may increase the risk for hemolytic anemia. PERICO is a prospective multicenter trial in which HIV/HCV-coinfected patients are randomized to receive peginterferon (pegIFN) alfa-2a 180 microg/week plus either weight-based RBV (1000-1200 mg/day) or RBV 2000 mg/day, the latest along with erythropoietin alfa (EPO) 30,000 IU/week from the first day until week 4. A total of 149 patients were assessed in a planned interim analysis at week 4. In both arms, 22% of patients achieved negative HCV-RNA (rapid virological response, RVR). Multivariate analysis [OR (IC 95%), p] showed that factors associated with RVR were HCV genotypes 2/3 vs. 1/4 [20 (5-100), <0.01] and baseline HCV-RNA [0.16 (0.07-0.37) per log IU/ml, <0.01]. The occurrence of severe anemia (hemoglobin <10 g/dl) did not differ when comparing RBV vs. high RBV + EPO (7% vs. 3%; p = 0.4). Moreover, RBV plasma trough levels were comparable at week 4 (1.9 vs. 2.4 microg/ml; p = 0.2). Use of high RBV doses with preemptive EPO during the first 4 weeks of hepatitis C therapy is safe, but fails to enhance significantly RBV plasma exposure and RVR rates. Extensive intraerythrocyte accumulation of RBV following boosted production of red blood cells by EPO could explain these findings.

Rate and predictors of success in the retreatment of chronic hepatitis C virus in HIV/hepatitis C Virus coinfected patients with prior nonresponse or relapse

BACKGROUND

In hepatitis C virus (HCV)/HIV-coinfected patients who failed a course of suboptimal hepatitis C therapy, retreatment with adequate doses and duration of pegylated interferon (pegIFN) plus ribavirin (RBV) is advisable in the presence of compensated advanced liver fibrosis.

METHODS

The efficacy and safety of pegIFN-alpha2a (180 microg/wk) plus RBV (<75 kg: 1000 mg/d; > or = 75 kg: 1200 mg/d) given for 12 months was prospectively assessed in HIV/HCV patients with nonresponse or relapse to a prior course of suboptimal hepatitis C therapy. The main endpoint was the achievement of sustained virological response (SVR).

RESULTS

A total of 52 patients were enrolled in the study (78% HCV genotypes 1 or 4; 56% with advanced liver fibrosis). Prior suboptimal regimens were IFN monotherapy (20%), IFN plus RBV (29%), and pegIFN plus RBV 800 mg/d (51%). Overall, 61% were nonresponders and 39% relapsers. Retreatment provided SVR in 30.8% of patients (19.5% for genotypes 1/4 vs. 72.7% for genotypes 2/3; P = 0.002). In multivariate analysis, HCV genotypes 2/3 [OR 22.2, 95% confidence interval (CI), 2.9-166.7, P = 0.003] and RBV plasma trough concentrations at week 4 [OR 3.9 (95% CI, 1.3-11.8), P = 0.01] were the only independent predictors of SVR.

CONCLUSIONS

Retreatment with pegIFN-alpha2a plus weight-based RBV for 12 months permits to achieve HCV clearance in nearly onethird of HIV/HCV-coinfected patients who failed a prior suboptimal course of hepatitis C therapy. Patients with HCV genotypes 2/3 and those with RBV plasma trough levels above 2.07 microg/mL show the highest chances of SVR.

Plasma ribavirin trough concentrations at week 4 predict hepatitis C virus (HCV) relapse in HIV-HCV-coinfected patients treated for chronic hepatitis C

The influence of ribavirin trough concentrations (RBV C(trough)) on the risk of hepatitis C virus (HCV) relapse was retrospectively analyzed in 99 HIV-HCV-coinfected patients who achieved end-of-treatment response with pegylated alpha interferon plus weight-based RBV. The independent predictors (odds ratio [OR] [95% confidence interval (CI)]) of HCV relapse were RBV plasma C(trough) of <2.5 microg/ml (4.5 [1.3 to 15.5]), baseline serum HCV RNA (2.5 [1.2 to 5.1]), and HCV genotype 1 or 4 (13.3 [2.6 to 66.7]). Monitoring of RBV C(trough) may permit early adjustment of RBV dosage to avoid HCV relapse.

The utility of therapeutic drug monitoring for ribavirin in patients with chronic hepatitis C--a critical review

OBJECTIVE

To evaluate the utility of therapeutic drug monitoring (TDM) for ribavirin in chronic hepatitis C.

DATA SOURCES

Literature searches were conducted through PubMed (1949-June 2009), EMBASE (1980-June 2009), BIOSIS Previews (1969-June 2009), International Pharmaceutical Abstracts (1970-June 2009), Google, and www.clinicaltrials.gov using the terms ribavirin, therapeutic monitoring, hepatitis C, and drug levels. In addition, pertinent reference citations from identified publications were reviewed. Studies were limited to English language, adult age, and human subjects.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated. Studies that measured ribavirin concentrations or dose and treatment response were included in the review.

DATA SYNTHESIS

While monitoring of ribavirin plasma concentrations to improve treatment response in patients with chronic hepatitis C has been described in the literature, the utility of TDM for ribavirin in this group of patients has not been systematically studied. Thus, a previously published 9-step decision-making algorithm was employed to help determine whether TDM is warranted, based on currently available evidence. Thirty articles involving patients with chronic hepatitis C mono-infection, 12 for hepatitis C-HIV coinfection, 5 for renal dysfunction, and 5 for post-liver transplant patients were reviewed. In all subpopulations, studies exist that either support or refute the usefulness of ribavirin TDM. Additionally, the majority of the included studies had methodologic limitations, such as small sample size, retrospective analyses, and lack of p value adjustment for multiple analyses. Large randomized controlled trials would help to definitively answer this question.

CONCLUSIONS

There is conflicting evidence about the existence of a correlation between ribavirin concentrations and virologic response or development of toxicity. This inconsistent evidence, coupled with the currently employed effective strategies that maximize sustained virologic response and minimize development of anemia, precludes the utility of TDM for ribavirin.

Feasibility of ribavirin therapeutic drug monitoring in hepatitis C

Ribavirin, a nucleoside analog, is administered in combination with interferon to patients with chronic hepatitis C. To evaluate the feasibility of ribavirin therapeutic drug monitoring, we investigated the influence of blood collection and preanalytical conditions on ribavirin concentrations and compared the results obtained from interlaboratory blind tests by 3 laboratories using different analytical techniques. On 3 occasions, blank serum samples spiked with ribavirin and pooled serum samples from patients on ribavirin were sent to the 3 laboratories. Two analytical techniques were based on liquid chromatography with tandem mass spectrometry (LC-MS/MS) and 1 on high-performance liquid chromatography with UV detection (HPLC-UV), with protein precipitation or solid-phase extraction, all validated according to international guidelines. Inter- and intra-batch mean relative errors ranged from -7.4% to +10.3% and from -10.3% to +7.4%, respectively. Relative standard deviations were <13.5% and <10.6%, respectively. Linearity, assessed blindly, between 125 and 4550 ng/mL was excellent (r > 0.991) for all 3 methods. The 2 LC-MS/MS techniques were slightly less precise and accurate than HPLC-UV, perhaps because the internal standard used was not a ribavirin isotope. Accurate and precise LC-MS/MS and HPLC-UV methods developed in 3 different laboratories provided excellent and consistent results to blind tests for ribavirin determination in spiked serum samples and pools of serum samples from patients with chronic hepatitis C virus infection.

Comparison of a new enzymatic assay with a high-performance liquid chromatography/ ultraviolet detection method for therapeutic drug monitoring of mycophenolic acid in adult liver transplant recipients

Mycophenolic acid (MPA) is used to prevent graft rejection. The methods used for determining the plasma MPA concentration in liver transplant recipients are the enzyme-multiplied immunoassay technique (EMIT), high-performance liquid chromatography with ultraviolet detection (HPLC-UV), and most recently mass spectrometry. EMIT has been reported to overestimate the MPA concentration by 30% to 35% in comparison with HPLC-UV. Recently, a new automated enzymatic assay based on inosine monophosphate dehydrogenase inhibition has been designed. The aim of the present investigation was to compare this technique with validated HPLC-UV in adult liver transplant recipients treated with tacrolimus or cyclosporine. One hundred seventy-six samples from 50 adult liver transplant recipients were analyzed with both techniques. Patients received mycophenolate mofetil (2 or 3 times daily) coadministered with cyclosporine microemulsion (n = 18) or tacrolimus (n = 32). Samples were drawn over an interdose interval during the early or late posttransplantation period. The Passing-Bablok regression and Bland-Altman plot were used to compare the 2 techniques. The Passing-Bablock regression, calculated from 166 samples, showed very good agreement between the enzymatic assay and the HPLC-UV method: enzymatic assay = 1.0204 (95% confidence interval, 0.9942, 1.0478) x HPLC-UV + 0.0201 (-0.0442, 0.0882). No significant bias was found between the techniques (Bland-Altman plot), and the median relative difference was 2.7% (95% confidence interval, -0.4, 6.6). In conclusion, the enzymatic assay showed an excellent correlation with HPLC-UV. Therefore, this method was proved valid and reliable for the monitoring of the plasma MPA concentration in adult liver transplant recipients treated with cyclosporine microemulsion or tacrolimus.

Increase in serum bilirubin in HIV/hepatitis-C virus-coinfected patients on atazanavir therapy following initiation of pegylated-interferon and ribavirin

Atazanavir use is associated with increases in serum bilirubin. Ribavirin, used to treat hepatitis-C infection, cause hemolysis and may worsen hyperbilirubinemia. We studied HIV/hepatitis-C virus-coinfected patients who initiated hepatitis-C therapy. Hyperbilirubinemia grade 3-4 increased from 9% to 45% after the start of hepatitis-C treatment in patients who used atazanavir concomitantly. Atazanavir use and hemoglobin (Hb) drops were predictors of increases in bilirubin. A substantial proportion of patients under atazanavir-therapy experienced significant hyperbilirubinemia and jaundice following initiation of hepatitis-C therapy.