Automation of mass spectrometric detection of analytes and related workflows: A review

The developments in mass spectrometry (MS) in the past few decades reveal the power and versatility of this technology. MS methods are utilized in routine analyses as well as research activities involving a broad range of analytes (elements and molecules) and countless matrices. However, manual MS analysis is gradually becoming a thing of the past. In this article, the available MS automation strategies are critically evaluated. Automation of analytical workflows culminating with MS detection encompasses involvement of automated operations in any of the steps related to sample handling/treatment before MS detection, sample introduction, MS data acquisition, and MS data processing. Automated MS workflows help to overcome the intrinsic limitations of MS methodology regarding reproducibility, throughput, and the expertise required to operate MS instruments. Such workflows often comprise automated off-line and on-line steps such as sampling, extraction, derivatization, and separation. The most common instrumental tools include autosamplers, multi-axis robots, flow injection systems, and lab-on-a-chip. Prototyping customized automated MS systems is a way to introduce non-standard automated features to MS workflows. The review highlights the enabling role of automated MS procedures in various sectors of academic research and industry. Examples include applications of automated MS workflows in bioscience, environmental studies, and exploration of the outer space.

Advances in high-resolution MS and hepatocyte models solve a long-standing metabolism challenge: the loratadine story

BACKGROUND

Loratadine (LOR, Claritin(®)) is a long-acting antihistamine used to treat allergic rhinitis. The major active human metabolite, desloratadine (DL, Clarinex(®)), is extensively metabolized to 3-hydroxydesloratadine (3-OH-DL) (M40) and subsequently glucuronidated before elimination. This study revealed the ability of a novel, long-term hepatocyte micropatterned co-culture (MPCC) model to generate in vivo metabolites. Metabolites were detected and characterized using non-targeted MS/MS(ALL) with SWATH™ acquisition by a UHPLC-Q-TOF system. Results & methodology: Human MPCCs extensively metabolized LOR and formed 3-OH-DL-glucuronide (M13). Cross-species comparisons revealed monkey- and rat-specific metabolites with gender-specific DL-pyridine-N-oxide formation in male rats. These results demonstrate a first for an in vitro hepatocyte model to generate circulating metabolites of LOR and detect species-specific differences. Early focus on human metabolites could have spared characterization of nonhuman metabolites in preclinical species.

Absolute quantification of imipramine and its metabolites in vivo utilizing calibrators from radiolabeled in vitro incubations

BACKGROUND

We have demonstrated the use of a single-point calibration approach, derived from in vitro metabolite identification studies utilizing radiolabeled imipramine, that allows for the quantitation of metabolites from in vivo studies in the absence of metabolite synthetic standards.

RESULTS

From the in vivo study of imipramine in rats, the concentration of parent and metabolites were determined using the single-point calibration approach. Sixty seven percent of the dosed imipramine was recovered within 24 h, with 95 and 5% of drug-related material detected in feces and urine, respectively.

CONCLUSION

Using a novel single-point calibration approach from radiolabeled in vitro studies, we quantified metabolites in vivo and determined various disposition pathways.

Data-driven approach for cross-species comparative metabolite exposure assessment: how to establish fundamental bioanalytical parameters for the peak area ratio method

We previously developed an high-performance LC–MS peak area ratio approach to demonstrate whether an animal species used in a toxicology study has greater exposures to drug metabolites relative to humans, meeting regulatory guidances regarding safety assessment of drug metabolites. Herein we explain the underlying bioanalytical principals, how to establish all fundamental bioanalytical parameters, and how to evaluate data quality in sample analysis, in the absence of authentic standards of analyte(s). A data-driven tiered approach was used in which data from the peak area ratio method can stand based on statistical analysis, as well as assuring that fundamental elements of bioanalytical method and bioanalysis are met. This strategy offers considerable time- and resource-saving advantage while providing high confidence in the safety assessment of human metabolites in drug development.

Meeting report: metabolites in safety testing (MIST) symposium-safety assessment of human metabolites: what's REALLY necessary to ascertain exposure coverage in safety tests?

In the 2012 AAPS metabolites in safety testing (MIST) symposium held in Chicago, IL, USA, on October 15, 2012, regulatory experts and industrial scientists joined together to discuss their perspectives and strategies in addressing contemporary MIST recommendations (FDA 2008, International Conference on Harmonization (ICH) M3(R2), ICH M(R2) Q&A). Overall, these regulatory guidances indicate that metabolites identified in human plasma should circulate at similar or greater concentrations in at least one of the animal species used in nonclinical safety assessment of the parent drug. However, synthetic standards for the metabolites often do not exist or they are intractable to synthesize, thus introducing multiple challenges in drug development for the quantitative comparison of metabolites between human and animals. A tiered bioanalytical strategy for metabolite analysis is a prevalent approach to demonstrate coverage in animals. Recent developments in bioanalytical methodology have yielded several time- and resource-sparing strategies to provide fit-for-purpose approaches that can enable critical decisions related to metabolite quantification and monitoring in plasma. This report summarizes the presentations and panel discussions at the symposium.