Bioanalysis of therapeutic peptides: Differentiating between total and anti-drug antibody bound drug using liquid chromatography–tandem mass spectrometry quantitation

Simultaneous quantification of rituximab and eculizumab in human plasma by liquid chromatography-tandem mass spectrometry and comparison with rituximab ELISA kits

OBJECTIVES

Specific and sensitive analytical techniques to quantify therapeutic monoclonal antibodies (mAbs) are required for therapeutic drug monitoring. The quantification of mAbs has been historically performed using enzyme-linked immunosorbent assays (ELISAs), for which the limitations in terms of specificity have led to the development of alternative analytical strategies.

METHODS

Here, we describe the validation of a liquid chromatography tandem mass-spectrometry (LC-MS/MS) method for the simultaneous quantification of rituximab (RTX - anti-CD20) and eculizumab (ECU - anti-C5). Sample preparation was based on our previously published method, using protein G purification and trypsin digestion. A new specific peptide for RTX, containing an N-terminal pyroglutamine and a trypsin miss-cleavage, enables better sensitivity, while peptide of ECU was chosen thanks to an in silico trypsin digestion and the Skyline® software. Full-length stable-isotope-labeled adalimumab was added to plasma samples as an internal standard. RTX in 50 human serum samples was quantified by LC-MS/MS and the concentrations obtained compared to those obtained with two commercial ELISA kits (Lisa Tracker® and Promonitor®).

RESULTS

Calibration curves were linear from 1 to 200 µg.mL^-1 for RTX and 5 to 200 µg.mL^-1 for ECU, and within-day and between-day accuracy and precision fulfilled Food and Drug Administration validation criteria. Comparison of the LC-MS/MS method with ELISA showed a negligible bias with the Lisa Tracker® kit (4%), but significant bias with the Promonitor® assay (mean underestimation of 69% for the Promonitor® assay).

CONCLUSIONS

This new LC-MS/MS method allows the simultaneous quantification of RTX and ECU in human samples and could be used for therapeutic drug monitoring.

A novel LC-MS/MS approach to the pharmacokinetic study of free and bound aflibercept simultaneously

To comprehensively evaluate the pharmacokinetic (PK) characteristics of aflibercept, we established a liquid chromatography with tandem mass spectrometry (LC-MS/MS) method to determine the concentration of vascular endothelial growth factor (VEGF)-A-bound aflibercept and free aflibercept. A specific sample preparation method of nano-surface and molecular-orientation limited (nSMOL) proteolysis was performed to extract both free and bound aflibercept from plasma. The tryptic peptides unique to aflibercept and VEGF-A were selected to quantify the amounts of total aflibercept and aflibercept-VEGF complex, respectively. The method was validated by evaluating its selectivity, linearity, precision, accuracy, extraction recovery, matrix effect, and stability. It was then successfully used to quantify total and bound aflibercept concentrations in cynomolgus monkey plasma, while indirectly obtaining the concentration of free aflibercept by subtraction. The PK results of this LC-MS/MS method are comparable to the traditional enzyme-linked immunosorbent assay (ELISA) results. It is thus a reliable and complementary method for the PK evaluation of aflibercept. Graphical abstract.

A new LC-MS/MS bioanalytical method for atenolol in human plasma and milk

AIM

A new sensitive LC-MS/MS method for the quantification of atenolol in human plasma and milk has been developed for clinical lactation studies.

METHODS & RESULTS

Atenolol and the internal standard, phenazone, were extracted from biological matrices by protein precipitation. A Phenomenex^® C-18 column and gradient chromatographic conditions were used for separation of the analyte, followed by detection with MS. Stability of samples was confirmed for atenolol in human plasma and milk for up to 3 months. Linearity range of 1-800 ng/ml (r² = 0.9995), the precision within 15% CV and the recovery of the analyte (80-100% range) were achieved.

CONCLUSION

A new validated analytical method for atenolol in plasma and milk was developed.

Antimycobacterial Activity of a New Peptide Polydim-I Isolated from Neotropical Social Wasp Polybia dimorpha

Mycobacterium abscessus subsp. massiliense, a rapidly growing mycobacteria (RGM) that is becoming increasingly important among human infectious diseases, is virulent and pathogenic and presents intrinsic resistance to several antimicrobial drugs that might hamper their elimination. Therefore, the identification of new drugs to improve the current treatment or lower the risk of inducing resistance is urgently needed. Wasp venom primarily comprises peptides that are responsible for most of the biological activities in this poison. Here, a novel peptide Polydim-I, from Polybia dimorpha Neotropical wasp, was explored as an antimycobacterial agent. Polydim-I provoked cell wall disruption and exhibited non-cytotoxicity towards mammalian cells. Polydim-I treatment of macrophages infected with different M. abscessus subsp. massiliense strains reduced 40 to 50% of the bacterial load. Additionally, the Polydim-I treatment of highly susceptible mice intravenously infected with M. abscessus subsp. massiliense induced 0.8 to 1 log reduction of the bacterial load in the lungs, spleen, and liver. In conclusion, this is the first study to show the therapeutic potential of a peptide derived from wasp venom in treating mycobacteria infections. Polydim-I acts on the M. abscessus subsp. massiliense cell wall and reduce 40–90% of the bacterial load both in vitro and in vivo. The presented results encourage further studies on the use of Polydim-I as one of the components for M. abscessus subsp. massiliense treatment.

An ex vivo potency assay to assess active drug levels of a GLP-1 agonistic peptide during preclinical safety studies

BACKGROUND

During development of biologics, safety and efficacy assessments are often hampered by immune responses to the treatment. To assess active exposure of a drug peptide in a toxicology study, we developed an ex vivo potency assay which complemented the total drug quantification assay.

METHODOLOGY

Compound activity was assessed in samples of treated monkeys by cell-based cAMP measurements. For each animal, activity was compared with its predose sample to which the compound has been added at the postdose concentration as determined by a total LC-MS/MS assay.

CONCLUSION

We were able to show that despite a high total test compound level, activity was reduced tremendously in antidrug-antibody-positive monkeys. Therefore, the applied ex vivo potency assay supplements drug quantification methods to determine active exposures.

Antibody-free workflows for protein quantification by LC–MS/MS

Antibody-free approaches for quantitative LC–MS/MS-based protein bioanalysis are reviewed and critically evaluated, and compared with the more widely used immunoaffinity-based approaches. Antibody-free workflows will be divided into four groups and discussed in the following order: direct analysis of signature peptides after proteolytic digestion; enrichment of target proteins and signature peptides by fractionated protein precipitation; enrichment of target proteins and signature peptides by reversed-phase and ion-exchange solid-phase extraction; and enrichment of target proteins and signature peptides by (antibody-free) affinity-solid-phase extraction.