Development of a quantification method for arginase inhibitors by LC-MS/MS with benzoyl chloride derivatization

Arginase is an enzyme responsible for converting arginine, a semi-essential amino acid, to ornithine and urea. Arginine depletion suppresses immunity via multiple mechanisms including inhibition of T-cell and NK cell proliferation and activity. Arginase inhibition is therefore an attractive mechanism to potentially reverse immune suppression and thus has been explored as a therapy for oncology and respiratory indications. Small molecules targeting arginase present significant bioanalytical challenges for in vitro and in vivo characterization as inhibitors of arginase are typically hydrophilic in nature. The resulting low or negative LogD characteristics are incompatible with common analytical methods such as RP-ESI-MS/MS. Accordingly, a sensitive, high-throughput bioanalytical method was developed by incorporating benzoyl chloride derivatization to increase the hydrophobic characteristics of these polar analytes. Samples were separated by reversed phase chromatography on a Waters XBridge BEH C18 3.5 μm, 30 × 3 mm column using gradient elution. The mass spec was operated in positive mode using electrospray ionization. The m/z 434.1→176.1, 439.4→181.2, 334.9→150.0 and 339.9→150.0 for AZD0011, AZD0011 IS, AZD0011-PL and AZD0011-PL IS respectively were used for quantitation. The linear calibration range of the assay was 1.00-10,000 ng/mL with QC values of 5, 50 and 500 ng/mL. The qualified method presented herein exhibits a novel, robust analytical performance and was successfully applied to evaluate the in vivo ADME properties of boronic acid-based arginase inhibitor prodrug AZD0011 and its active payload AZD0011-PL.

Determination of caffeine, paraxanthine, theophylline and theobromine in premature infants by HILIC-MS/MS

Aim: Caffeine is a central nervous system stimulant, used to treat apnea of prematurity. A hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS) approach was developed to detect caffeine, paraxanthine, theophylline and theobromine in premature infants. Method: Protein precipitation of plasma samples (10 μl) was carried out by treating with acetonitrile containing caffeine-¹³C₃. The separation was carried out on an ACQUITY HPLC^® BEH HILIC column. Caffeine and its metabolites were quantified by multiple reaction monitoring modes with positive electrospray ionization. Results: The established method had a good linear relationship in the range of 0.0600-60.0 μg/ml for caffeine, 0.0250-7.50 μg/ml for theobromine and 0.0150-4.50 μg/ml for paraxanthine and theophylline. Conclusion: A HILIC-MS/MS method was developed and validated to determine caffeine and its major metabolites in plasma of premature infants.

Metabolic profiling for water-soluble metabolites in patients with schizophrenia and healthy controls in a Chinese population: A case-control study

Objectives: Objective measures integrated with clinical symptoms may improve early prevention and detection of schizophrenia. Herein we aim to evaluate potential water-soluble metabolic biomarkers in schizophrenia.Methods: We recruited adults with schizophrenia (n = 113) who had not received pharmacological treatment for at least 1 month prior to enrollment and 111 age- and sex-matched healthy subjects from Weifang, Shandong province, China. All serum samples were analysed using liquid chromatography-tandem mass spectrometry coupled with a hydrophilic interaction liquid chromatography column.Results: Eleven metabolites, namely carnitines (oleoylcarnitine, l-palmitoylcarnitine, 9-decenoylcarnitine and 2-trans,4-cis-decadienoylcarnitine), polar lipids (lysophosphatidylcholine (LPC)(P-16:0), LPC (16:0), LPC (15:0) and LPC(14:0)), amino acids (taurine and l-arginine), and organic acid (2,5-dichloro-4-oxohex-2-enedioate), separated the patients and healthy controls. Compared with healthy controls, taurine, l-palmitoylcarnitine and oleoylcarnitine levels were higher, whereas the remaining eight metabolites were lower in patients with schizophrenia. A combination of four metabolites, i.e., oleoylcarnitine, 9-decenoylcarnitine, LPC (15:0) and LPC (14:0), provided the most robust between-group separation.Conclusions: This study appears to distinguish between groups of patients and controls, which should be considered as a contribution to putative potential biomarkers. The water-soluble metabolites were determined to be significantly different between the groups in the current study, and were primarily related to cellular bioenergetics, notably oxidative stress.

Serum metabolic profiling using small molecular water-soluble metabolites in individuals with schizophrenia: A longitudinal study using a pre-post-treatment design

AIM

We sought to compare alterations in serum bioenergetic markers within a well-characterized sample of adults with schizophrenia at baseline and after 8 weeks of pharmacological treatment with the hypothesis that treatment would be associated with significant changes in bioenergetic markers given the role of bioenergetic dysfunction in schizophrenia.

METHODS

We recruited adults with schizophrenia (n = 122) who had not received pharmacological treatment for at least 1 month prior to enrollment, including drug-naïve (i.e., first-episode) participants and treatment non-adherent participants. Pre- and post-treatment serum samples were analyzed using liquid chromatography-tandem mass spectrometry.

RESULTS

Metabolites with the greatest change, when comparing pre- and post-treatment levels, were identified revealing 14 water-soluble metabolites of interest. The composition of these metabolites was: amino acids (n = 6), carnitines (n = 4), polar lipids (n = 3), and organic acid (n = 1). All amino acids and lysophosphatidylcholines (LysoPC) were increased, while the four carnitines - oleoylcarnitine, L-palmitoylcarnitine, linoleyl carnitine, and L-acetylcarnitine - were decreased post-treatment. Of these metabolite biomarkers, six - oleoylcarnitine, linoleyl carnitine, L-acetylcarnitine, LysoPC(15:0), D-glutamic acid, and L-arginine - were identified as having most consistently and predictably changed after 8 weeks of treatment.

CONCLUSION

The current study identified several bioenergetic markers that consistently change with pharmacological treatment. These bioenergetic changes may provide further insights into the pathophysiology of schizophrenia along with furthering our understanding of the mechanisms subserving both the effects (e.g., antipsychotic effects) and side-effects (e.g., metabolic syndrome) of antipsychotics.

LC–MS/MS assay for N1-methylnicotinamide in humans, an endogenous probe for renal transporters

Background: N1-methylnicotinamide (1-NMN) has been proposed as a potential clinical biomarker to assess drug–drug interactions involving organic cation transporters (OCT2) and multidrug and toxin extrusion protein transporters. Results: A hydrophilic interaction liquid chromatography–MS/MS assay, to quantify 1-NMN, in human plasma and urine is reported. Materials & methods: A hydrophilic interaction chromatography (HILIC)-tandem mass spectrometry (MS/MS) assay to quantify 1-NMN in human plasma and urine is reported. The basal 1-NMN levels in plasma and urine were 4–120 and 2000–15,000 ng/ml, respectively. Conclusion: 1-NMN plasma AUCs increased two- to fourfold versus placebo following the administration of a clinical candidate that in vitro experiments indicated was an OCT2 inhibitor. The described hydrophilic interaction liquid chromatography–MS/MS assay can be used to assess a clinical compound candidate for the inhibition of OCT2 and multidrug and toxin extrusion protein transporter in first-in-human studies.

Development and validation of HILIC-ESI/MS/MS methods for simultaneous quantitation of several antipsychotics in human plasma and blood

BACKGROUND

Knowledge of antipsychotic drug levels at point of care (POC) may significantly aid therapeutic decision-making. To support the development of future POC devices and to validate the use of fingerstick capillary blood sampling, two robust hydrophilic interaction LC-ESI/MS/MS methods were developed and validated. Two PK studies were completed evaluating the correlation between fingerstick blood and plasma concentrations with corresponding venous blood and plasma concentrations for several commonly prescribed atypical antipsychotics and selected metabolites. Sensitive and reliable LC-MS/MS bioanalytical assays were developed to support these studies.

RESULTS

Three methods, requiring only 25-μl matrix volumes, were developed using supported liquid extraction with hydrophilic interaction LC-MS/MS detection and validated according to regulatory guidance.

CONCLUSION

Robust and efficient LC-MS/MS assays were established and were effective in providing antipsychotic drug matrix comparator results in the intended clinical studies.

Recent advances in the application of hydrophilic interaction chromatography for the analysis of biological matrices

Hydrophilic interaction chromatography (HILIC) is being increasingly used for the analysis of hydrophilic compounds in biological matrices. The complexity of biological samples demands adequate sample preparation procedures, specifically adjusted for HILIC analyses. Currently, most bioanalytical assays are performed on bare silica and ZIC-HILIC columns. Trends in HILIC for bioanalysis include smaller particle sizes and miniaturization of the analytical column. For complex biological samples, multidimensional techniques can separate and identify more compounds than 1D separations. The high volatility of the mobile phase, the added separation power and high sensitivity make MS the detection method of choice for bioanalysis using HILIC, although other detectors such as evaporative light scattering detection, charged aerosol detection and nuclear magnetic resonance have been reported.

Case studies: the impact of nonanalyte components on LC–MS/MS-based bioanalysis: strategies for identifying and overcoming matrix effects

Achieving sufficient selectivity in bioanalysis is critical to ensure accurate quantitation of drugs and metabolites in biological matrices. Matrix effects most classically refer to modification of ionization efficiency of an analyte in the presence of matrix components. However, nonanalyte or matrix components present in samples can adversely impact the performance of a bioanalytical method and are broadly considered as matrix effects. For the current manuscript, we expand the scope to include matrix elements that contribute to isobaric interference and measurement bias. These three categories of matrix effects are illustrated with real examples encountered. The causes, symptoms, and suggested strategies and resolutions for each form of matrix effects are discussed. Each case is presented in the format of situation/action/result to facilitate reading.

Hydrophilic interaction chromatography (HILIC) for LC–MS/MS analysis of monoamine neurotransmitters

Background: Hydrophilic interaction chromatography (HILIC) is becoming an increasingly popular alternative to traditional reversed-phase chromatography for the analysis of polar compounds. The ability to retain the most polar compounds in HILIC makes it attractive for the analysis of certain large groups of compounds, such as monoamines, which are inherently very polar. Results: This paper details the development of a HILIC LC–MS/MS method for the analysis of monoamine neurotransmitters. The emphasis is on method development; in particular, the factors influencing sensitivity, peak shape and resolution. Mobile-phase ionic strength, temperature and stationary phase functionality are shown to be key parameters for the successful development of HILIC methods. Conclusion: HILIC is shown to be an appropriate and suitable method for the analysis of monoamine neurotransmitters and an attractive alternative to reversed-phase analysis. The most polar analytes, which are essentially unretained by reversed-phase chromatography, demonstrate superior retention and resolution when analyzed by HILIC.

Analysis of polar metabolites by hydrophilic interaction chromatography–MS/MS

Increasing emphasis has been placed on quantitative characterization of drug metabolites during drug discovery and development. Due to the more polar nature of drug metabolites, quantitative analysis using traditional reversed-phase liquid chromatography tandem mass spectrometry (RPLC–MS/MS) can be quite challenging. As an alternative chromatographic mode, hydrophilic interaction chromatography (HILIC) offers unique advantages for analysis of polar metabolites, providing better retention/separation, higher sensitivity, higher efficiency and potential for ultra-fast analysis to improve throughput. In this article, selected case studies from the authors’ own laboratory, and examples from current literature, will be discussed to demonstrate some practical considerations for method development of HILIC–MS/MS assays. The effectiveness of using HILIC–MS/MS for mitigating analytical challenges associated with quantitation of polar metabolites, including phase I and II metabolites of drugs, as well as endogenous metabolites, will be exhibited.

Validation of a high-sensitivity assay for zatebradine in dried blood spots of human blood at pg/ml concentrations using HILIC–MS/MS

Background: One of the main reasons for the increased popularity of dried blood spots (DBS) is related to the 3Rs principles (replacement, refinement and reduction) for animal use in drug development. The small blood volume collected using this technique may have a significant impact on the assay sensitivity. An approach that made use of hydrophilic interaction chromatography (HILIC) to enhance the LC–MS assay sensitivity was explored and optimized for a tool compound. Results: A very high-sensitivity assay in dried spots of human blood was validated in the range of 5 to 5000 pg/ml. The use of HILIC increased LC–MS sensitivity up to fivefold compared with other reversed phase chromatographic methods. Conclusion: The good compatibility of the DBS extracts with HILIC and the results of the assay validation for zatebradine at a very low LLOQ demonstrate the high potential and the high performance of this approach.