Determination of the HCV Protease Inhibitor Telaprevir in Plasma and Dried Blood Spot by Liquid Chromatography-Tandem Mass Spectrometry

Stability study of the antiviral agent camphecene in dried blood spots at different temperatures

In this study, an optimized procedure of sample preparation for quantitative determination of the antiviral agent camphecene in dried rat blood spots was developed. It has been shown that when using methanol containing 0.1% HCOOH as an extractant, the recovery of the substance increases in comparison with the previously developed method. In addition to this, there is no need to dilute the obtained solutions with water for the analysis of the sample by high-performance liquid chromatography (HPLC) on a column with a reversed-phase sorbent. By using the developed method, the stability of samples of dried rat blood spots containing camphecene in different concentrations at different temperatures was studied. It was found that while the samples were stored at room temperature, apparently, desorption of the substance occurs leading to a loss of more than 15% of its initial amount after 5-10 days. Lowering the temperature increases the stability of samples and their storage at -70°C is possible for 4 weeks.

Multiplexed therapeutic drug monitoring (TDM) of antiviral drugs by LC-MS/MS

Background

Therapeutic drug monitoring (TDM) can be a useful tool in the clinical management of anti-hepatitis C virus (anti-HCV) drugs. Methods for the determination of various types of anti-HCV drugs in biological samples are, therefore, needed for clinical laboratories.

Objective

In this work, employing the LC-MS/MS approach, we aimed to develop a multiplexed method for identification of the following anti-HCV drugs: Ribavirin (RBV), Boceprevir (BOC), Telaprevir (TVR), Simeprevir (SIM), Daclatasvir (DAC), Sofosbuvir (SOF) and its metabolite GS 331007 (SOFM) in liquid plasma and in dried plasma spots (DPSs).

Method

A single-step extractive-deproteinization was employed for both liquid plasma and DPSs. Reverse-phase liquid chromatography coupled with MRM detection was developed for multiplexed drug detection and quantification.

Results

Sensitivities (expressed as LOQ) were 10 (±1.2), 10 (±4.9), 10 (±4.4), 10 (±4.4), 10 (±6.4), 10 (±3.4), 10 (±6.4) ng/ml for RBV, SOFM, SOF, DAC, BOC, TVR, and SIM, respectively; accuracy (expressed as BIAS%) was <10% for all drugs; reproducibility (intra- and inter-day CV%) was <10% for all drugs; dynamic range was 10-10,000 ng/ml for all drugs.

Conclusions

A novel, simple, rapid and robust LC-MS/MS multiplex assay for the TDM of various anti-HCV drugs that are currently in the clinic was successfully developed. Application to DPS samples enabled TDM to be used for outpatients as well.

Dried Blood Spot Methodology in Combination With Liquid Chromatography/Tandem Mass Spectrometry Facilitates the Monitoring of Teriflunomide

Background:

Teriflunomide, a once-daily oral immunomodulator approved for treatment of relapsing-remitting multiple sclerosis, is eliminated slowly from plasma. If necessary to rapidly lower plasma concentrations of teriflunomide, an accelerated elimination procedure using cholestyramine or activated charcoal may be used. The current bioanalytical assay for determination of plasma teriflunomide concentration requires laboratory facilities for blood centrifugation and plasma storage. An alternative method, with potential for greater convenience, is dried blood spot (DBS) methodology. Analytical and clinical validations are required to switch from plasma to DBS (finger-prick sampling) methodology.

Methods:

Using blood samples from healthy subjects, an LC-MS/MS assay method for quantification of teriflunomide in DBS over a range of 0.01–10 mcg/mL was developed and validated for specificity, selectivity, accuracy, precision, reproducibility, and stability. Results were compared with those from the current plasma assay for determination of plasma teriflunomide concentration.

Results:

Method was specific and selective relative to endogenous compounds, with process efficiency ∼88%, and no matrix effect. Inaccuracy and imprecision for intraday and interday analyses were <15% at all concentrations tested. Quantification of teriflunomide in DBS assay was not affected by blood deposit volume and punch position within spot, and hematocrit level had a limited but acceptable effect on measurement accuracy. Teriflunomide was stable for at least 4 months at room temperature, and for at least 24 hours at 37°C with and without 95% relative humidity, to cover sampling, drying, and shipment conditions in the field. The correlation between DBS and plasma concentrations (R² = 0.97), with an average blood to plasma ratio of 0.59, was concentration independent and constant over time.

Conclusions:

DBS sampling is a simple and practical method for monitoring teriflunomide concentrations.

Dried blood spots analysis with mass spectrometry: Potentials and pitfalls in therapeutic drug monitoring

Therapeutic drug monitoring (TDM) relays in the availability of specialized laboratory assays, usually available in reference centers that are not accessible to all patients. In this context, there is a growing interest in the use of dried blood spot (DBS) sampling, usually obtained from finger pricks, which allows simple and cost-effective logistics in many settings, particularly in Developing Countries. The use of DBS assays to estimate plasma concentrations is highly dependent on the hematocrit of the blood, as well as the particular characteristics of the measured analyte. DBS assays require specific validation assays, most of them are related to hematocrit effects. In the present manuscript, the application of mass spectrometric assays for determination of drugs for TDM purposes in the last ten years is reviewed, as well as the particular validation assays for new DBS methods.

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.