A UPLC–MS/MS method for the simultaneous plasma quantification of all isomeric forms of the new anti-HCV protease inhibitors boceprevir and telaprevir

Matrix effect management in liquid chromatography mass spectrometry: the internal standard normalized matrix effect

LC-MS is becoming a standard for many applications, thanks to high sensitivity and selectivity; nevertheless, some issues are still present, particularly due to matrix effect (ME). Considering this, the use of optimal internal standards (ISs, usually stable-isotope labeled) is important, but not always possible because of cost or availability. Therefore, a deep investigation of the inter-lot variability of the ME and of the correcting power of the chosen IS (isotope-labeled or not) is mandatory. While the adoption of isotopically labeled ISs considered as a 'gold standard' to mitigate ME impact on analytical results, there is not consensus about the standard technique to evaluate it during method validation. In this paper, currently available techniques to evaluate, reduce or counterbalance ME are presented and discussed. Finally, these techniques were summarized in a flowchart for a robust management of ME, particularly considering the concept of 'internal standard normalized ME'.

UPLC-MS/MS method for the simultaneous quantification of three new antiretroviral drugs, dolutegravir, elvitegravir and rilpivirine, and other thirteen antiretroviral agents plus cobicistat and ritonavir boosters in human plasma

Rilpivirine (RPV), dolutegravir (DTG) and elvitegravir (EVG) are the latest antiretroviral drugs approved for treatment of HIV infection. Currently, poor information is currently available concerning their pharmacokinetic and pharmacodynamic properties, thus making the use of therapeutic drug monitoring for these drugs not useful. This lack of information is partially due to the absence of an high-throughput method for their simultaneous quantification together with other antiretroviral drugs. In this work, we describe the development and validation of a new UPLC-MS/MS method to quantify these drugs, together with other fourteen antiretroviral agents, in human plasma. One hundred microliters of plasma samples were added with internal standard (6,7-Dimethyl- 2,3-di(2-pyridyl) quinoxaline), underwent a simple protein precipitation with methanol:acetonitrile (50:50v/v) followed by sample dilution with water. Chromatographic separation was performed on a Acquity^® UPLC HSS T3 column (150mm x 2.1mm I.D) with a particle size of 1.8μm and compounds were detected with a tandem mass detector, monitoring two ion transitions for each drugs. The mean recovery of RPV, DTG and EVG were 101%, 87% and 112.3% respectively. Accuracy and precision inter/intra-day were below 15% for all drugs, in accordance to Food and Drug Administration guidelines requirements. The UPLC-MS/MS method reported here could be used routinely to monitor plasma concentrations of antiviral drugs, including RPV, DTG and EVG.

Current trends in the treatment of hepatitis C: interventions to avoid adverse effects and increase effectiveness of anti-HCV drugs

Viral hepatitis, an inflammatory liver disease, is caused by various genotypes of hepatitis C viruses (HCV). Hepatitis C slowly sprouts into fibrosis, which progresses to cirrhosis. Over a prolonged period of time compensated cirrhosis can advance to decompensated cirrhosis culminating in hepatic failure and death. Conventional treatment of HCV involves the administration of interferons. However, association of interferon with the adverse drug reactions led to the development of novel anti-HCV drugs given as monotherapy or in combination with the other drugs. Advances in drug delivery systems (DDS) improved the pharmacokinetic profile and stability of drugs, ameliorated tissue damages on extravasation and increased the targeting of affected sites. Liposomes and lipid based vehicles have been employed with polyethylene glycol (PEG) so as to stabilize the formulations as PEG drug complex. Sofosbuvir, a novel anti-HCV drug, is administered as monotherapy or in combination with daclatasvir, ledipasivir, protease inhibitors, ribavirin and interferon for the treatment of HCV genotypes 1, 2 and 3. These drug combinations are highly effective in eradicating the interferon resistance, recurrent HCV infection in liver transplant, concurrent HIV infection and preventing interferon related adverse effects. Further investigations to improve drug targeting and identification of new drug targets are highly warranted due to the rapid emergence of drug resistance in HCV.

Pharmacogenetics of ribavirin-induced anemia in HCV patients

Dual therapy (pegylated interferon plus ribavirin) was considered the standard of care for hepatitis C virus (HCV) treatment until 2011, when the first-wave direct-acting antivirals were added to this regimen for HCV genotype-1 patients to increase the sustained virological response rate. The second-wave direct-acting antivirals entered the clinical use also in some ribavirin (RBV)- and/or interferon-free combinations. Nevertheless, since some of the new therapeutic regimens also include RBV and its use results still associated with hemolytic anemia, this requires countermeasures to be prevented. These include the identification of several host predictive factors involved in RBV absorption, distribution, metabolism, elimination and many others that might influence this toxic effect. For this reason, we provided an overview of the potential role of pharmacogenomics in predisposing RBV-treated HCV patients to anemia.

UPLC-MS/MS method with automated on-line SPE for the isomer-specific quantification of the first-generation anti-HCV protease inhibitors in peripheral blood mononuclear cells

HCV infection affects over 170 million people worldwide. The current standard for treatment of genotype 1 infection is the association of the first generation protease inhibitors boceprevir or telaprevir to ribavirin and peginterferon α. Although the response rate has been improved with these new drugs, some pharmacokinetic/pharmacodinamic issues emerged in the past years. To date, some analytical methods are available for the quantification of these drugs in plasma; however, the real active concentrations of the two drugs are those in hepatocytes. Being the withdrawal of hepatocytes too invasive, in this work we aimed to develop and validate a chromatographic method coupled with tandem mass spectrometry capable of quantifying boceprevir and telaprevir isomers in peripheral blood mononuclear cells, used as an "in-vivo" cellular model of compartmentalization. The method used an on-line solid phase extraction protocol based on the new OSM(®) platform and was fully validated following FDA guidelines. This method showed mean intra- and inter-day inaccuracy and imprecision both lower than 15%, high and stable recovery and contained matrix effect, with a run time of 6min, comprehensive of SPE extraction. The method was then applied on 35 real samples from patients treated with boceprevir or telaprevir, with good analytical performances, thus assessing its eligibility for a possible future routine use. Peculiar pharmacokinetic data have been observed, suggesting the usefulness of investigating intracellular pharmacokinetics of these drugs. Further studies will be required to test the correlation of intracellular concentrations with effectiveness and toxicity of triple therapy.

Development and validation of an ultra performance liquid chromatography tandem mass method for sildenafil and N-desmethyl sildenafil plasma determination and quantification

Sildenafil is a selective inhibitor of cGMP-specific type 5 phosphodiesterase (PDE5) used for the treatment of masculine erectile dysfunction and Pulmonary Arterial Hypertension (PAH). Sildenafil causes vasodilatation; relax of the smooth muscle and reduction of pulmonary arterial pressure. In the liver cytocrome P450 metabolizes sildenafil into its active metabolite, N-desmethyl sildenafil. The determination of plasma levels of sildenafil and N-desmethyl sildenafil could be useful for therapy optimization and pharmacokinetic studies. We have developed and validated a new method for the quantification of sildenafil and its metabolite in human plasma by rapid protein precipitation extraction, using an UPLC system, coupled with a tandem mass spectrometric detector (UPLC-MS/MS). The calibration range was fitted at least square model (r(2)≥0.999), with an accuracy and an intra- and inter-day RSD% (Relative Standard Deviation), both for sildenafil and N-desmethyl sildenafil, lower than 15%, as required by the FDA guidelines; LLOQ, LLOD, ULOQ were 3.9ng/mL, 1.95ng/mL and 1000ng/mL, respectively, for both analytes. Matrix effect, expressed as mean percent deviation of peak areas, was in the range between 2.6% and 5.8%, lower than 15% as required by guidelines. The mean recovery was 83.2 % for sildenafil and 84.5% for N-desmethyl sildenafil. This method has successfully been applied to a clinical pharmacokinetic study of sildenafil and N-desmethyl sildenafil in patients with PAH undergoing cardiac surgery.

Intracellular accumulation of boceprevir according to plasma concentrations and pharmacogenetics

Boceprevir (BOC) is a directly-acting antiviral agent for the treatment of hepatitis C virus genotype 1 (HCV-1) infection. It is a mixture of two stereoisomers, the inactive R and the active S isomers. No data have previously been published on BOC intracellular accumulation. In this study, BOC isomer concentrations in peripheral blood mononuclear cells (PBMCs) and plasma were determined. The influence of various single nucleotide polymorphisms (SNPs) on plasma and intracellular drug exposure at Week 4 of triple therapy were also evaluated. Plasma and intracellular BOC concentrations were determined at the end of the dosing interval (C(trough)) using a UPLC-MS/MS validated method. Allelic discrimination was performed through real-time PCR. Median plasma concentrations were 65.97 ng/mL for the S isomer and 36.31 ng/mL for the R isomer; the median S/R plasma concentration ratio was 1.66. The median PBMC concentration was 2285.88 ng/mL for the S isomer; the R isomer was undetectable within PBMCs. The median S isomer PBMC/plasma concentration ratio was 28.59. A significant positive correlation was found between plasma and PBMC S isomer concentrations. ABCB1 1236, SLC28A2 124 and IL28B rs12979860 SNPs were associated with the S isomer PBMC/plasma concentration ratio. In regression models, S isomer plasma levels and FokI polymorphism were able to predict S isomer intracellular exposure, whereas SNPs in AKR1, BCRP1 and SLC28A2 predicted the S isomer PBMC/plasma concentration ratio. No similar data regarding BOC pharmacogenetics and pharmacokinetics have been published previously. This study adds a novel and useful overview of the pharmacological properties of this drug.

Pharmacokinetic interactions between telaprevir and antiretroviral drugs in HIV/HCV-coinfected patients with advanced liver fibrosis and prior HCV non-responders

Complex drug-drug interactions have been reported with concurrent administration of telaprevir (TVR) and human immunodeficiency virus (HIV) protease inhibitors (PIs), leading to relevant limitations of the therapeutic options for patients coinfected with hepatitis C virus (HCV) and HIV. However, little is known about the pharmacokinetics and drug interactions between TVR and antiretrovirals in HIV/HCV-coinfected patients with advanced liver fibrosis. Here we report the pharmacokinetics of TVR and antiretrovirals in a cohort of HIV/HCV genotype 1-coinfected patients with advanced liver fibrosis treated with TVR-based triple anti-HCV therapy. No significant differences were observed in the pharmacokinetics of atazanavir, amprenavir or tenofovir at baseline and at Day 15 of TVR, whereas the AUC0-4h of darunavir was 36% lower in the presence of TVR (AUC0-4h 15007ngh/mL and 9563ngh/mL at baseline and at Day 15 of TVR administration, respectively). Noteworthy, the AUC0-4h, Cmin and Cmax of raltegravir were reduced by 61%, 50% and 64%, respectively. However, none of the patient's plasma levels of tenofovir, atazanavir, amprenavir or raltegravir declined below their minimum effective concentrations even in association with TVR, and no HIV treatment failure occurred. A non-significant trend for lower TVR exposure was seen in patients concomitantly given amprenavir versus those given atazanavir (AUC0-4h, 9840ngh/mL and 13345ngh/mL, respectively). In conclusion, this study highlighted the feasibility of maintaining the current antiretroviral regimen in HIV/HCV-coinfected patients, even when significant interactions with TVR are predictable, whenever a change of HIV PIs is not deemed appropriate.

ABCB11 and ABCB1 gene polymorphisms impact on telaprevir pharmacokinetic at one month of therapy

In 2011 direct-acting antivirals, including telaprevir, have been developed to achieve a better antiviral effect. It was reported that telaprevir is a substrate of P-glycoprotein (ABCB1) and cytochrome P450 3A4. The aim of this retrospective study was the evaluation of the influence of some single nucleotide polymorphisms (SNPs) of genes (ABCB1, SLC28A2/3, SLC29A1) involved in TLV and RBV transport and their correlation with plasma TLV drug exposure at 1 month of therapy. We also investigated the association of a SNP in ABCB11 gene, whose role in TLV transport was not yet shown. Twenty-nine HCV-1 patients treated with telaprevir, ribavirin and pegylated-interferon-α were retrospectively analyzed; allelic discrimination was performed by real-time PCR. Telaprevir Ctrough levels were influenced by Metavir score (P=0.023), ABCB1 2677 G>T (P=0.006), ABCB1 1236 C>T (P=0.015) and ABCB11 1131 T>C (P=0.033) SNPs. Regarding ABCB1 3435 C>T, a not statistically significant trend in telaprevir plasma concentration was observed. Metavir score (P=0.002, OR -336; 95% CI -535;-138), ABCB1 2677 (P=0.020, OR 497; 95% CI 86; 910), ABCB11 1131 (P=0.002, OR 641; 95% CI 259;1023) and CNT2 -146 (P=0.006, OR -426; 95% CI -721;-132) were able to predict telaprevir plasma levels in the regression analysis. Other SNPs showed no association. This study reveals BSEP implication in telaprevir transport and confirms the involvement and influence of P-glycoprotein on telaprevir plasma levels. To date, no similar data concerning pharmacogenetics and pharmacokinetics were published, but further studies in different and bigger cohorts are needed.

Relationship between the early boceprevir-S isomer plasma concentrations and the onset of breakthrough during HCV genotype 1 triple therapy

In a prospective cohort of 18 patients treated with boceprevir, we examined the role of boceprevir plasma concentration at the onset of breakthrough during the treatment. Nine patients experienced breakthrough during therapy. The resistance patterns were as follows: S122S/R, I132V, T54A/I132V, V156S/I170A, V36M/T54S/R155K, V36M/R155K and T54/R155K. Boceprevir-S isomer (SCH 534128) median concentration in patients with breakthrough was 48.3 ng/mL (interquartile range 43-58 ng/mL); in others, it was significantly (p 0.019) higher: 151 ng/mL. Low boceprevir plasma concentration can lead to virologic resistance; therapeutic drug monitoring should be used to prevent the onset of viral breakthrough during triple-regimen therapy with boceprevir.

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.

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.