A convenient strategy to overcome interference in LC-MS/MS analysis: Application in a microdose absolute bioavailability study

A high-throughput UPLC-MS/MS method for the determination of eight anti-tumor drugs in plasma

Rapidly developing UPLC-MS/MS bioassays with high throughput and quality are challenging yet desired in routine clinics. METHODS & RESULTS: A high-throughput UPLC-MS/MS bioassay has been built for simultaneously quantifying gefitinib, ruxolitinib, dasatinib, imatinib, ibrutinib, methotrexate, cyclophosphamide and paclitaxel. After the protein precipitation with methanol, samples were separated on an Acquity BEH C₁₈ column following a gradient elution system with methanol and 2 mM ammonium acetate in water at 40 °C with a run time of 3 min (flow rate 0.4 mL/min). Mass quantification in the positive ion SRM mode was then performed with electrospray ionization. The method of specificity, linearity, accuracy, precision, matrix effects, recovery, stability, dilution integrity and carryover were all validated as per the guideline of the China Food and Drug Administration whose values met the admissible limits. Application of the bioassay to therapeutic drug monitoring revealed important variability in the studied anti-tumour drugs. CONCLUSION: This validated approach was shown to be reliable and effective in clinical management, being a valuable support in therapeutic drug monitoring and subsequent individualized dosing optimization.

Mitigating analyte to stable isotope labelled internal standard cross-signal contribution in quantitative liquid chromatography-tandem mass spectrometry

Background

Utilising stable isotope labelled internal standards (SIL-IS) in quantitative LC-MS/MS drug analysis is the most widely used approach to normalise for variability during sample quantification processes. However, compounds containing atoms such as Sulphur, Chlorine or Bromine, could potentially cause cross-signal contribution to the SIL-IS from the naturally occurring isotopes, resulting in non-linear calibration curves. A simple, novel method of mitigating the effect is presented here. It entails monitoring of a less abundant SIL-IS isotope, as the precursor ion, of a mass that has no/minimal isotopic contribution from the analyte isotopes.

Methods

Experiments were conducted on two LC-MS/MS analysers: Waters Xevo TQ-S and Shimadzu 8050. Flucloxacillin (FLX) was used as an example. Two transitions were selected for FLX (m/z 454 → 160 → 295) and one for each of the SIL-IS isotopes (m/z 458 → 160 for the isotope 457 g/mol and m/z 460 → 160 for the isotope 459 g/mol). Assay biases were assessed at three SIL-IS concentrations: 0.7, 7 and 14 mg/L for each isotope.

Results

When using the SIL-IS isotope m/z 458 → 160 at a concentration of 0.7 mg/L, biases were up to 36.9 % on both instruments. Increasing the SIL-IS concentration to 14 mg/L, reduced the bias to 5.8 %. Using the less abundant isotope, m/z 460 → 160, resulted in biases of 13.9 % at an SIL-IS concentration of 0.7 mg/L.

Conclusions

Applying this method will mitigate cross-signal contribution from the analyte isotopes to the corresponding SIL-IS, minimise the use of SIL-IS, and, thereby, reduce overall cost.

Study of the metabolism of myricetin in rat urine, plasma and feces by ultra-high-performance liquid chromatography

Myricetin is a common natural flavonoid compound with various pharmacological activities. However, the metabolite characterization of this substance remains inadequate. In this study, a simple and rapid system strategy based on UHPLC-Q-Exactive Orbitrap mass spectrometry combining parallel reaction monitoring mode was established to screen and identify myricetin metabolites in rat urine, plasma and feces after oral administration. A total of 38 metabolites were fully or partially characterized based on their accurate mass, characteristic fragment ions, retention times, corresponding cLogP values, etc. These metabolites were presumed to be generated through glucuronidation, glucosylation, sulfation, dihydroxylation, acetylation, hydrogenation, hydroxylation and their composite reactions. In addition, the characteristic fragmentation pathways of flavonoids with more metabolites were summarized for the subsequent metabolite identification. The study provides an overall metabolic profile of myricetin, which would be of great help in predicting the in vivo pharmacokinetic profiles and understanding the action mechanism of this active ingredient.

Limitations of deuterium-labeled internal standards for quantitative electrospray ionization mass spectrometry analysis of fatty acid metabolites

RATIONALE

The electrospray ionization mass spectrometry (ESI-MS) methodology often shows poor ionization reproducibility in the analysis of biological samples. Therefore, normalization of the measured peak intensities is essential. It is believed that quantitative data with high reproducibility can be obtained by adding a constant amount of an internal standard (IS) material labeled with stable isotopes to each sample, thus allowing the correction of the quantitative value of the target compound by that of the IS. We investigated whether the presence or absence of a labeled IS improves the accuracy of these quantitative values.

METHODS

Triple quadrupole MS coupled with liquid chromatography was used to analyze fatty acid metabolites in biological samples as target compounds. Two independent systems were used to provide a measure of reproducibility in two different laboratories.

RESULTS

Data having poor reproducibility in the raw peak areas were efficiently normalized using the IS, but, crucially, the IS method using stable isotopes was not always necessary. In some cases, the reproducibility was relatively good even without using the IS. In a contaminant matrix, the MS response behavior of the target compound and its stable isotope-labeled material was complicated. Since ion suppression by matrix contaminants was dependent on the concentration of the target compound, the added amounts of the ISs were also important, Furthermore, an equivalent normalization effect was obtained by using a pooled quality control sample as an external standard, thus obviating the need for labeled IS samples, which are often expensive and sometimes not commercially available.

CONCLUSIONS

Our results raise the question as to whether the quantitative method using stable-isotope-labeled ISs is always necessary and beneficial. However, the results obtained in this study cannot be generalized because only fatty acid metabolites were examined using ESI-MS and only a highly substituted deuterium-labeled IS was used.

2019 White Paper on Recent Issues in Bioanalysis: Chromatographic Assays (Part 1 - Innovation in Small Molecules and Oligonucleotides & Mass Spectrometric Method Development Strategies for Large Molecule Bioanalysis)

The 2019 13^th Workshop on Recent Issues in Bioanalysis (WRIB) took place in New Orleans, LA, USA on April 1-5, 2019 with an attendance of over 1000 representatives from pharmaceutical/biopharmaceutical companies, biotechnology companies, contract research organizations and regulatory agencies worldwide. WRIB was once again a 5-day, week-long event - a full immersion week of bioanalysis, biomarkers, immunogenicity and gene therapy. As usual, it was specifically designed to facilitate sharing, reviewing, discussing and agreeing on approaches to address the most current issues of interest including both small- and large-molecule bioanalysis involving LCMS, hybrid LBA/LCMS, LBA cell-based/flow cytometry assays and qPCR approaches. This 2019 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2019 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 1) covers the recommendations on Innovation in Small Molecules and Oligonucleotides & Mass Spec Method Development Strategies for Large Molecules Bioanalysis. Part 2 (2018 FDA BMV Guidance, 2019 ICH M10 BMV Draft Guideline and regulatory agencies' input on bioanalysis, biomarkers, immunogenicity and gene therapy) and Part 3 (New Insights in Biomarkers Assays Validation, Current & Effective Strategies for Critical Reagent Management, Flow Cytometry Validation in drug discovery & development & CLSI H62, Interpretation of the 2019 FDA Immunogenicity Guidance and The Gene Therapy Bioanalytical Challenges) are published in volume 11 of Bioanalysis, issues 23 and 24 (2019), respectively.

Application of in-sample calibration curve methodology for regulated bioanalysis: Critical considerations in method development, validation and sample analysis

Traditionally, for a liquid chromatography tandem mass spectrometry (LC-MS/MS) bioanalytical assay, an external calibration curve is required to achieve accurate quantitation of an analyte. Recently, a novel in-sample calibration curves (ISCC) methodology that can achieve quick and accurate LC-MS/MS bioanalysis without the use of an external calibration curve was reported. The ISCC methodology utilizes the presence of multiple naturally occurring isotopologues of a stable isotopically labeled analyte to construct an in-sample calibration curve for the quantification. This methodology has great potential in many applications, for example biomarker measurement, quantitative proteomics and clinical diagnosis. Here, we assessed the feasibility of applying this ISCC-LC-MS/MS methodology in regulated bioanalysis using BMS-984478, a drug candidate, as the model compound. We also proposed method validation procedures/processes for this new approach for industry peers' consideration and feedback. A LC-MS/MS method using the ISCC strategy was successfully developed and validated for the quantitative analysis of BMS-984478 in human plasma over the range of 1.33-993.42 ng/mL. The validated ISCC-LC-MS/MS method was compared with a previously validated method using the conventional external calibration curve approach, and the two methods showed equivalent performance. Critical considerations and practical approaches in method development, validation and sample analysis were also discussed. Our work demonstrated that the ISCC-LC-MS/MS methodology is a promising approach for regulated LC-MS/MS bioanalysis. ISCC-LC-MS/MS methodology has its unique advantages and has great potential to be widely applied for various quantitative applications, and may even change the landscape of quantitative analysis.