Challenges of developing a bioanalytical method for a macrolide immunosuppressant compound by LC-MS/MS

Sensitive UHPLC–MS/MS method for the determination of tacrolimus in minipig whole blood

Background: Tacrolimus, a potent immunosuppressant drug widely used systemically to reduce the risk of organ rejection in transplants, has been repositioned for topical treatment of atopic dermatitis. Results & methodology: This work describes the optimization of a new method for the determination of tacrolimus in whole blood after topical administration. Sample treatment consisted of an automated procedure based on protein precipitation followed by solid-phase extraction. The present method showed good performance with quantitation limits of 10 pg ml-1 and intra- and interday precision and accuracy lower than 15 and 10%, respectively. Conclusion: A new highly sensitive UHPLC–MS/MS method has been developed enabling a better characterization of the minipig blood plasma pharmacokinetic behavior of tacrolimus after topical administration.

Application of a Volumetric Absorptive Microsampling Device to a Pharmacokinetic Study of Tacrolimus in Rats: Comparison with Wet Blood and Plasma

BACKGROUND AND OBJECTIVES

Volumetric absorptive microsampling (VAMS) devices are useful for sampling a smaller volume of blood from rodents in the preclinical setting. In the present study, we evaluated the proof of concept of a VAMS device by comparing the pharmacokinetic data of tacrolimus in rats among dried blood in VAMS, wet blood, and plasma.

METHODS

Tacrolimus was administered orally, to rats, at a dose of 10 mg/kg. Only 10 μL aliquots of blood were absorbed by VAMS devices at designated time points. Tacrolimus was extracted with a methanol-water mixture (1:1, v/v) via sonication. Tacrolimus levels in wet blood (10 μL) and plasma (10 μL) were quantified after protein precipitation.

RESULTS

Tacrolimus in VAMS devices was quantifiable from 0.2 ng/mL using high-performance liquid chromatography with tandem mass spectrometer. Accuracy and precision were within the acceptance criteria. Bland-Altman plots showed that tacrolimus concentrations in VAMS devices were similar to those in wet blood, regardless of tacrolimus levels. On the other hand, tacrolimus levels in plasma were different from those in VAMS devices, especially at lower concentrations, likely due to partition of tacrolimus to blood cells. However, pharmacokinetic parameters were comparable among the three matrices.

CONCLUSIONS

Collectively, these findings suggest that the VAMS device can be a useful device for pharmacokinetic studies in rats.

Aging of biological matrices and its effect on bioanalytical method performance

Apart from the well-known matrix effects that can occur in ESI LC–MS, biological matrices may have other effects influencing the quantitative reliability of bioanalytical methods. In this paper, six case studies are presented that show the effect that aging, that is the change in properties and composition of biological matrices over time, can have on the performance of bioanalytical methods. It is shown that selectivity can be affected due to the formation or disappearance of endogenous compounds. Stability can be influenced because of the decrease (or increase) of enzyme activities and recovery can be impacted if the extractability from binding sites in the matrix is enhanced or decreased. A general discussion on the importance of these matrix effects is provided as well as a perspective on how to properly address them in the method-development and validation stages of regulated bioanalysis.

Tissue sample preparation in bioanalytical assays

Analytical quantitation of compounds in tissue has become a more prevalent addition to biological sample analysis in recent times. This increase will most certainly continue to bring the question of proper analytical method validation to the forefront of discussion. Thoughtful design of sample homogenization, analyte fortification and extraction can ensure a successful analysis. This review presents current trends in tissue sample preparation by harvesting, homogenization techniques, as well as concerns for calibrator and QC preparation. Strategies for consideration and resolution of common pitfalls in method development, for example stability issues and control biomatrices in endogenous analysis, are also presented.

Comparison of triple quadrupole and high-resolution TOF-MS for quantification of peptides

Background: With an increased interest in peptides and proteins as potential new drug candidates, new approaches for sensitive and selective quantitative analysis are required. LC–MS/MS analysis provides a good alternative to immunoassays with reduced method development times and increased specificity. Results: We have evaluated two state-of-the-art triple quadrupole and high-resolution TOF mass spectrometers with respect to their performance for quantification of six peptides (glufibrinopeptide B, somatostatin, enfuvirtide, TRI1144, C34 and exenatide). The peptides were spiked into protein-precipitated plasma supernatant. Triple quadrupole quantification was performed in SRM mode, and in high-resolution, MS narrow-width extracted chromatograms were generated for quantification. Specificity, accuracy, reproducibility and robustness were found to be comparable between the two instruments. The triple quadrupole instrument is still the most sensitive instrument for quantification of peptides with a median factor of about four-times higher sensitivity (based on LLOQ evaluation). Conclusion: Based on sensitivity, the newest generation triple quadrupole MS systems are still the preferred technology for quantification of peptides. Since the sensitivity difference between triple quadrupole instruments and the new-generation high-resolution TOF-MS instruments is minor, the latter offer a useful alternative whenever additional selectivity is preferred or the use of a generic approach not requiring method optimization is advantageous.