Development of a general method for quantifying IgG-based therapeutic monoclonal antibodies in human plasma using protein G purification coupled with a two internal standard calibration strategy using LC-MS/MS

A liquid chromatography - Tandem mass spectrometry method for determination of ocrelizumab in serum of patients with multiple sclerosis

Ocrelizumab is a second generation recombinant humanized IgG1 monoclonal antibody used for the treatment of multiple sclerosis that selectively target B cells expressing the CD20 antigen. This study aimed to develop and validate a UPLC-MS/MS method for quantification of ocrelizumab in human serum, which can be used in clinical applications for therapeutic drug monitoring. The analysis of ocrelizumab was performed using a bottom-up approach on a liquid chromatography coupled to tandem mass spectrometry detection. The method involved immunoglobulin precipitation with cold methanol followed by peptide digestion with trypsin. The resulting specific peptides were separated on an Acquity UPLC BEH C18 column at 55 °C using gradient elution. The method was validated according to European Medicines Agency (EMEA) guidelines and demonstrated intra- and inter-assay precision with coefficients of variation ranging from 1.6 % to 6.1 % and accuracies between 90.2 % and 107.2 %. Stability testing, including autosampler, long-term and freeze-thaw stability, showed no more than 15 % variation. The method was successfully applied to 169 patient samples, revealing ocrelizumab concentrations ranging from 0.5 to 21.8 mg/L in patients on 6-month dosing regimen and 20.5-65.0 mg/L in 16 patients receiving an initial two-week dose of 300 mg. The newly developed UPLC-MS/MS method met all criteria for accuracy, precision and stability, confirming its suitability for clinical use in monitoring ocrelizumab levels in multiple sclerosis patients.

Evaluation of the association between bevacizumab concentration and clinical outcomes in patients with breast cancer brain metastasis

Bevacizumab is widely used in various clinical indications, but investigations into its optimal dosage for treating CNS metastases remain limited. The BEEP regimen, comprising bevacizumab, etoposide, and cisplatin, has recently demonstrated promising clinical outcomes for patients with breast cancer brain metastasis (BCBM) or leptomeningeal metastasis (LM). This study aimed to evaluate the exposure-response relationship of bevacizumab in BCBM patients and to explore the improved CNS penetration of chemotherapy by bevacizumab with LM patients. Twenty-two BCBM patients and six LM patients receiving the BEEP regimen were enrolled. For BCBM patients, blood samples were drawn at trough level of cycles 1 and 6 to investigate the association between bevacizumab concentrations and clinical outcomes. For LM patients, plasma and cerebrospinal fluid (CSF) concentrations of bevacizumab and etoposide were measured to investigate the enhancement of etoposide penetration provided by bevacizumab. Concentration evaluation revealed that bevacizumab plasma concentrations substantially varied between individuals. Additionally, concentrations increased after 6 cycles, indicating bevacizumab accumulation during treatment. Although bevacizumab concentrations did not associate with therapeutic response and progression-free survival, patients with higher bevacizumab concentrations exhibited longer overall survival (adjusted HR 0.78; p = 0.039). Furthermore, a positive correlation was observed between time-weighted average concentration of plasma bevacizumab and CSF penetration of etoposide on day 2 (post-bevacizumab) relative to day 1 (pre-bevacizumab) (r = 0.83; p = 0.042). These findings offer valuable insights into the application of therapeutic drug monitoring of bevacizumab to improve survival outcomes in BCBM patients. Further studies are warranted to determine the optimal bevacizumab concentration.

Challenges and Insights in Absolute Quantification of Recombinant Therapeutic Antibodies by Mass Spectrometry: An Introductory Review

This review describes mass spectrometry (MS)-based approaches for the absolute quantification of therapeutic monoclonal antibodies (mAbs), focusing on technical challenges in sample treatment and calibration. Therapeutic mAbs are crucial for treating cancer and inflammatory, infectious, and autoimmune diseases. We trace their development from hybridoma technology and the first murine mAbs in 1975 to today's chimeric and fully human mAbs. With increasing commercial relevance, the absolute quantification of mAbs, traceable to an international standard system of units (SI units), has attracted attention from science, industry, and national metrology institutes (NMIs). Quantification of proteotypic peptides after enzymatic digestion using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) has emerged as the most viable strategy, though methods targeting intact mAbs are still being explored. We review peptide-based quantification, focusing on critical experimental steps like denaturation, reduction, alkylation, choice of digestion enzyme, and selection of signature peptides. Challenges in amino acid analysis (AAA) for quantifying pure mAbs and peptide calibrators, along with software tools for targeted MS data analysis, are also discussed. Short explanations within each chapter provide newcomers with an overview of the field's challenges. We conclude that, despite recent progress, further efforts are needed to overcome the many technical hurdles along the quantification workflow and discuss the prospects of developing standardized protocols and certified reference materials (CRMs) for this goal. We also suggest future applications of newer technologies for absolute mAb quantification.

Nivolumab plasma concentration and clearance associated with overall survival in patients with renal cell carcinoma

BACKGROUND

Nivolumab is an immune checkpoint inhibitor (ICI) that selectively inhibits programmed cell death protein 1 activation, restoring antitumor immunity. ICIs are indicated for various types of advanced solid tumors; however, not all patients benefit from them, and tools that could be used in the clinic to predict response to treatment represent an unmet need. Here we describe the development of a new population pharmacokinetic (PPK) model in patients treated with nivolumab in clinical trials. Applying the model to a patient population with renal cell carcinoma identified nivolumab clearance and plasma concentration as predictors of overall survival (OS).

METHODS

A custom liquid chromatography with tandem mass spectrometry method for quantifying nivolumab plasma concentration was developed and validated following the European Medicines Agency guidelines for bioanalytical method validation. The PPK model was developed using data from patients treated in the NIVIPIT (n=38) and NIVOREN (n=137) trials of nivolumab in metastatic melanoma and renal cell carcinoma, respectively. The PPK model was used to determine pharmacokinetic (PK) parameters such as baseline clearance and simulate individual clearance changes over time. The relationship between PK characteristics (including clearance at Cycle 1 (CLC1), plasma concentration at Cycle 3 and clinical outcomes was assessed in 137 patients treated in NIVOREN. Kaplan-Meier methodology was used in time-to-event analyses.

RESULTS

In 137 patients, the median nivolumab CLC1 was 6 mL/hour and the median plasma concentration at Cycle 3 was 48 µg/mL. Median follow-up was 21.0 months (95% CI 20.2 to 22.5 months) with a survival rate at 6 months of 91.2% and 77.9% at 12 months. In univariate analysis, OS was significantly higher in patients with CLC1<6 mL/hour versus ≥6 mL/hour (HR 2.2 (95% CI 1.2 to 4.1), p=0.0146). Shorter OS was observed in patients with plasma concentration at Cycle 3 below the median (48 µg/mL) versus those above the median (HR 0.4 (95% CI 0.2 to 0.8), p=0.0069). Multivariate analysis showed a trend towards lower clearance, but this did not reach statistical significance (p=0.0694).

CONCLUSIONS

Results of the study may potentially be used to predict outcomes of nivolumab therapy in patients with renal cell carcinoma. Additional applications may include guiding dose adjustments of nivolumab in those who are less likely to respond to the initial dose.

High-throughput, low-cost quantification of 11 therapeutic antibodies using caprylic acid precipitation and LC-MS/MS

BACKGROUND

Therapeutic drug monitoring of treatment with therapeutic antibodies is hampered by the application of a wide range of different methods in the quantification of serum levels. LC-MS based methods could significantly improve comparability of results from different laboratories, but such methods are often considered complicated and costly. We developed a method for LC-MS/MS based quantification of 11 therapeutic antibodies concomitantly measured in a single run, with emphasis on simplicity in sample preparation and low cost.

RESULTS

After a single-step sample purification using caprylic acid precipitation to remove interfering proteins, the sample underwent proteolysis followed by LC-MS/MS analysis. Infliximab is used as internal standard for sample preparation while isotope-labeled signature peptides identified for each analyte are internal standards for the LC-MS/MS normalization. The method was validated according to recognized guidelines, and pipetting steps can be performed by automated liquid handling systems. The total precision of the method ranged between 2.7 and 7.3 % (5.1 % average) across the quantification range of 4-256 μg/ml for all 11 drugs, with an average accuracy of 96.3 %. Matrix effects were xamined in 55 individual patient samples instead of the recommended 6, and 147 individual patient samples were screened for interfering compounds.

SIGNIFICANCE AND NOVELTY

Our method for simultaneous quantification of 11 t-mAb in human serum allows an unprecedented integration of robustness, speed and reduced complexity, which could pave the way for uniform use in research projects and clinical settings alike. In addition, the first LC-MS protocol for signature peptide-based quantification of durvalumab is described. This high throughput method can be readily adapted to a drug panel of choice.

Quantifying payloads of antibody‒drug conjugates using a postcolumn infused-internal standard strategy with LC‒MS

BACKGROUND

Antibody‒drug conjugates (ADCs) are innovative biopharmaceutics consisting of a monoclonal antibody, linkers, and cytotoxic payloads. Monitoring circulating payload concentrations has the potential to identify ADC toxicity; however, accurate quantification faces challenges, including low plasma concentrations, severe matrix effects, and the absence of stable isotope-labeled internal standards (SIL-IS) for payloads and their derivatives. Previous studies used structural analogs as internal standards, but different retention times between structural analogs and target analytes may hinder effective matrix correction. Therefore, a more flexible approach is required for precise payload quantification.

RESULTS

We developed an LC‒MS/MS method incorporating a postcolumn-infused internal standard (PCI-IS) strategy for quantifying payloads and their derivatives of trastuzumab emtansine, trastuzumab deruxtecan, and sacituzumab govitecan, including DM1, MCC-DM1, DXd, SN-38, and SN-38G. Structural analogs (maytansine, Lys-MCC-DM1, and exatecan) were selected as PCI-IS candidates, and their accuracy performance was evaluated based on the percentage of samples within 80%-120% quantification accuracy. Compared to the approach without PCI-IS correction, exatecan enhanced the accuracy performance from 30-40%-100% for SN-38 and DXd, while maytansine and Lys-MCC-DM1 showed comparable accuracy for DM1 and MCC-DM1. This validated PCI-IS analytical method showed superior normalization of matrix effect in all analytes compared to the conventional internal standard approach. The clinical application of this approach showed pronounced differences in DXd and SN-38 concentrations before and after PCI-IS correction. Moreover, only DXd concentrations after PCI-IS correction were significantly higher in patients with thrombocytopenia (p = 0.037).

SIGNIFICANCE

This approach effectively addressed the issue of unavailability of SIL-IS for novel ADC payloads and provided more accurate quantification, potentially yielding more robust statistical outcomes for understanding the exposure-toxicity relationship in ADCs. It is anticipated that this PCI-IS strategy may be extrapolated to quantify payloads and derivatives in diverse ADCs, thereby providing invaluable insights into drug toxicity and fortifying patient safety in ADC usage.

A novel ultrasensitive chemiluminescence enzyme immunoassay by employment of a signal enhancement of horseradish peroxidase-luminol-hydrogen peroxide reaction for the quantitation of atezolizumab, a monoclonal antibody used for cancer immunotherapy

This study describes, for the first time, the development and validation of a novel ultrasensitive chemiluminescence enzyme immunoassay (CLEIA) for the quantification of atezolizumab (ATZ), a monoclonal antibody approved by the FDA for treatment of different types of cancer. The assay involved the non-competitive binding of ATZ to its specific antigen (PD-L1 protein). The immune complex of PD-L1/ATZ formed on the internal surface of the plate wells was quantified by a novel chemiluminescence (CL)-producing horseradish peroxidase (HRP) reaction. The reaction employed a highly efficient CL enhancer for the HRP-luminol-hydrogen peroxide reaction which was 4-(imidazol-1-yl)phenol. The conditions of the CLEIA and its detection system were refined, and the optimum procedures were established. The CLEIA was validated in accordance with the guidelines of immunoassay validation for bioanalysis, and all the validation criteria were acceptable. The assay's limit of detection and limit of quantitation were 12.5 and 37.5 pg mL-1, respectively, with a working dynamic range of 25-800 pg mL-1. The assay enables the accurate and precise quantitation of ATZ in human plasma samples without any interferences from endogenous substances and/or the plasma matrix. The results of the proposed CLEIA were favourably comparable with those of a pre-validated enzyme-linked immunosorbent assay using a colorimetric detection system. The CLEIA is characterized by simple and high throughput features. The CLEIA is superior to the existing analytical methodologies for ATZ. The proposed CLEIA has a great value in the quantitation of ATZ in clinical settings for assessment of its pharmacokinetics, therapeutic drug monitoring, and refining the safety profile.

A robust and validated LC-MS/MS method for the quantification of ramucirumab in rat and human serum using direct enzymatic digestion without immunoassay

A new liquid chromatography tandem mass spectrometry (LC-MS/MS) method was established to quantify the anti-gastric cancer fully human monoclonal antibody (ramucirumab) in rat and human serum. The surrogate peptide (GPSVLPLAPSSK) for ramucirumab was generated by trypsin hydrolysis and quantified using the isotopically labeled peptide GPSVLPLAPSSK[13C6, 15N2]ST containing two more amino acids at the carboxyl end as an internal standard to correct for variations introduced during the enzymatic hydrolysis process and any mass spectrometry changes. Additionally, the oxidation and deamidation of unstable peptides (VVSVLTVLHQDWLNGK and NSLYLQMNSLR) were detected. The quantitative range of the proposed method was 1-1000 μg/mL, and complete methodological validation was performed. The precision, accuracy, matrix effect, sensitivity, stability, selectivity, carryover, and interference of the measurements met the required standards. The validated LC-MS/MS method was applied to pharmacokinetic studies in rats administered ramucirumab at 15 mg/kg intravenously. Overall, a robust, efficient, and cost-effective LC-MS/MS method was successfully developed for quantifying ramucirumab in rat and human serum.

Voltammetric studies and spectroscopic investigations of the interaction of an anticancer drug bevacizumab-DNA and analytical applications of disposable pencil graphite sensor

A sensitive, simple, fast electrochemical biosensor for the DNA interaction of bevacizumab (BEVA), which is used as a targeted drug in cancer treatment, was developed using the differential pulse voltammetry (DPV) technique with pencil graphite electrode (PGE). In the work, PGE was electrochemically activated in a supporting electrolyte medium of +1.4 V/60 s (PBS pH 3.0). Surface characterization of PGE was carried out by SEM, EDX, EIS, and CV techniques. Determination and electrochemical properties of BEVA were examined with CV and DPV techniques. BEVA gave a distinct analytical signal on the PGE surface at a potential of +0.90 V (vs. Ag/AgCl). In the procedure proposed in this study, BEVA gave a linear response on PGE in PBS (pH 3.0 containing 0.02 M NaCl) (0.1 mg mL-1 - 0.7 mg mL-1) with LOD and LOQ values of 0.026 mg mL-1 and 0.086 μg mL-1, respectively. BEVA was reacted with 20 μg mL-1 DNA in PBS for 150 s and analytical peak signals for adenine and guanine bases were evaluated. The interaction between BEVA-DNA was supported by UV-Vis. Absorption spectrometry and the binding constant was determined as 7.3 × 104.

Prognostic Value of Nivolumab Clearance in Non-Small Cell Lung Cancer Patients for Survival Early in Treatment

INTRODUCTION

Immune checkpoint inhibitors improved survival of advanced stage non-small cell lung cancer patients, but the overall response rate remains low. A biomarker that identifies non-responders would be helpful to allow treatment decisions. Clearance of immune checkpoint inhibitors is related to treatment response, but its prognostic potential early in treatment remains unknown. Our primary aim was to investigate the prognostic potential of nivolumab clearance for overall survival early in treatment. Our secondary aim was to evaluate the performance of nivolumab clearance as prognostic biomarker.

PATIENTS AND METHODS

Individual estimates of nivolumab clearances at first dose, 6 and 12 weeks after treatment initiation were obtained via nonlinear mixed-effects modelling. Prognostic value of nivolumab clearance was estimated using univariate Cox regression at first dose and for the ratios between 6 and 12 weeks to first dose. The performance of nivolumab clearance as biomarker was assessed by calculating sensitivity and specificity.

RESULTS

During follow-up of 75 months, 69 patients were included and 865 died. Patients with a nivolumab clearance ≥ 7.3 mL/h at first dose were more likely to die compared to patients with a nivolumab clearance < 7.3 mL/h at first dose (hazard ratio [HR] = 3.55, 955 CI 1.75-7.20). The HRs of dose nivolumab clearance ratios showed similar results with a HR of 3.93 (955 CI 1.66-9.32) for 6 weeks to first-dose clearance ratio at a 0.953 cut-point and a HR of 2.96 (955 CI 1.32-6.64) for 12 weeks to first-dose clearance ratio at a cut-point of 0.814. For nivolumab clearance at all early time points, sensitivity was high (≥ 0.95) but specificity was low (0.11-0.29).

CONCLUSION

Nivolumab clearance is indicative of survival early in treatment. Our results encourage to further assess the prognostic potential of immunotherapy clearance.

Determination of plasma concentration of Belimumab by LC-MS/MS: Method development, validation, and clinical application

INTRODUCTION

Belimumab is a monoclonal antibody against B cell activating factor (BLyS). This monoclonal antibody (mAb) has been shown to be effective in reducing disease activity in patients with systemic lupus erythematosus (SLE). Belimumab is available in two forms as a lyophilized powder for intravenous (IV) use, or single-dose syringe for subcutaneous (SC) use. The aim of this study was to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantitation of belimumab in human serum.

MATERIAL AND METHODS

All analyses relied on nano-surface and molecular-orientation limited (nSMOL) proteolysis coupled with LC-MS/MS. Quantifications was performed in multiple reactions monitoring (MRM) mode, and electrospray ionization was conducted in positive mode.

RESULTS

Belimumab was quantified with signature peptide QAPGQGLEWMGGIPFGTAK and normalized using P14R. The total run time per assay was 10 min. Linearity was measured from 5 to 800 μg/mL (r² > 0.995). Accuracy and precision based on three quality control levels range from 11.2 - 9.51 % and 1.24 - 13.12 % respectively. The carryover was less than 7 %. In all, 87 patient samples were processed (65, IV; 22, SC). Mean concentration of belimumab was significantly higher for SC (93.0 ± 74.0 µg/mL) than for IV (67.4 ± 38.9 µg/mL) administration.

CONCLUSION

We have developed the first method of belimumab quantification combining LC-MS/MS and nSMOL proteolysis. It can be used for future clinical pharmacokinetic studies of belimumab and for investigating the relationship between belimumab concentration, efficacy, and toxicity in SLE patients.

A validated LC-MS/MS method for the quantification of bevacizumab in rat, cynomolgus monkey, and human serum

Bevacizumab is a humanized monoclonal antibody used in the treatment of advanced colorectal and non-small cell lung cancer. Our main aim was to establish a simple, economical, and high efficiency liquid chromatography tandem mass spectrometry (LC-MS/MS) method for quantifying the content of bevacizumab in various biological fluids (rat, cynomolgus monkey, and human serum). A surrogate peptide of bevacizumab, specifically FTFSLDTSK, was generated through trypsin hydrolysis, and quantified using an isotopically labeled peptide containing two amino acids, FTFSLDTSK[13C6, 15N2]ST, as an internal standard to correct for variations introduced during the enzymatic hydrolysis process and any mass spectrometry variabilities. The pre-treatment process included denaturation, disulfide bond reduction and alkylation, trypsin hydrolysis, and termination of the reaction, with a total duration of approximately 2.5-3 h. The results of the methodological validation showed that the linear range in three different biological matrices was 0.2 µg/mL to300 µg/mL, with an LLOQ of 0.2 µg/mL. The precision and accuracy of the measurements met the required standards. The validated LC-MS/MS method was used to conduct pharmacokinetic analysis in rats administered bevacizumab at a dose of 10 mg/kg intravenously.

Liquid chromatography - tandem mass spectrometry method for determination of natalizumab in serum and cerebrospinal fluid of patients with multiple sclerosis

Natalizumab is a humanized recombinant monoclonal IgG4 antibody used in the treatment of multiple sclerosis. Commonly used methods for natalizumab and anti-natalizumab antibodies quantification are enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay, respectively. Measurement of therapeutic monoclonal antibodies can be challenging due to the resemblance to human plasma immunoglobulins. Recent developments in mass spectrometry enables to analyze vast variety of large protein molecules. The aim of this study was to develop a LC-MS/MS method for determining natalizumab in human serum and cerebrospinal fluid (CSF) and apply it to clinical settings. For successful quantification, it was necessary to find specific sequences of peptides in natalizumab. This immunoglobulin was treated with dithiothreitol and iodoacetamide, cleaved with trypsin into short specific peptides and determined on a UPLC-MS/MS system. An Acquity UPLC BEH C18 column at 55 °C and gradient elution was used for analysis. Intra- and interassay accuracies and precisions were tested at four concentration levels. Precision was determined by coefficients of variation and was in the range of 0.8-10.2 %, with accuracy in the range of 89.8-106.4 %. The concentration of natalizumab in patient samples ranged from 1.8 to 193.3 μg/mL. The method was validated according to the European Medicines Agency (EMA) guideline, met all acceptance criteria for accuracy and precision, and is suitable for clinical applications. In comparison to immunoassay, which can be elevated by cross-reaction with endogenous immunoglobulins, the results of developed LC-MS/MS method are more accurate and specific.

Development of a highly sensitive chemiluminescence immunoassay using a novel signal-enhanced detection system for quantitation of durvalumab, an immune-checkpoint inhibitor monoclonal antibody used for immunotherapy of lung cancer

Durvalumab (DUR) is a human monoclonal antibody used for the immunotherapy of lung cancer. It is a novel immune-checkpoint inhibitor, which blocks the programmed death 1 (PD-1) and programmed death-ligand 1 (PD-L1) proteins and works to promote the normal immune responses that attack the tumour cells. To support the pharmacokinetic (PK) studies, therapeutic drug monitoring (TDM) and refining the safety profile of DUR, an efficient assay is required, preferably immunoassay. This study describes, for the first time, the development of a highly sensitive chemiluminescence immunoassay (CLIA) for the quantitation of DUR in plasma samples with enhanced chemiluminescence detection system. The CLIA protocol was conducted in 96-microwell plates and involved the non-competitive binding reaction of DUR to its specific antigen (PD-L1 protein). The immune complex of DUR with PD-L1 formed onto the inner surface of the assay plate wells was quantified by a chemiluminescence (CL)-producing horseradish peroxidase (HRP) reaction. The reaction employed 4-(1,2,4-triazol-1-yl)phenol (TRP) as an efficient enhancer of the HRP-luminol-hydrogen peroxide (H2O2) CL reaction. The optimum protocol of the proposed CLIA was established, and its validation parameters were assessed as per the guidelines for the validation of immunoassays for bioanalysis. The working dynamic range of the assay was 10-800 pg mL-1 with a limit of detection (LOD) of 10.3 pg mL-1. The assay enables the accurate and precise quantitation of DUR in human plasma at a concentration as low as 30.8 pg mL-1. The CLIA protocol is simple and convenient; an analyst can analyse several hundreds of samples per working day. This high throughput property enables the processing of many samples in clinical settings. The proposed CLIA has a significant benefit in the quantitation of DUR in clinical settings for assessment of its PK, TDM and refining the safety profile.

Quantification of canakinumab in human plasma by liquid chromatography-high resolution mass spectrometry

Canakinumab is a fully-human monoclonal immunoglobulin gamma 1 kappa. This interleukin-1β blocker is used for the treatment of autoinflammatory diseases. Various studies have demonstrated the value of therapeutic drug monitoring of monoclonal antibodies in the management of inflammatory diseases. The purpose of this study was to develop a method to quantify canakinumab plasmatic concentration using liquid chromatography-high-resolution (Orbitrap®) mass spectrometry. The quantification was based on a bottom-up approach with the analysis of one surrogate peptide after an immunopurification of IgG followed by tryptic proteolysis. Rituximab and cetuximab, both IgG1, were tested as internal standards. Chromatographic separation was performed on a bioZenTM Peptide PS-C18 column. Mass detection was conducted in positive ionization mode with Parallel Reaction Monitoring at a resolution of 70,000. The method was fully validated in terms of linearity, sensitivity, selectivity, accuracy and matrix effect. Standards ranged from 2.5 to 75 µg/mL. Intra- and inter-day coefficients of variation ranged from 3.7 to 14.7 %, and accuracy from 97.4 to 104.1 %. This method allowed the determination of canakinumab plasmatic concentrations from eight treated patients. This method is efficient and suitable for routine use in therapeutic drug monitoring or pharmacokinetic studies.

A Rapid Method for Direct Quantification of Antibody Binding-Site Concentration in Serum

The quantitation of the available antibody binding-site concentration of polyclonal antibodies in serum is critical in defining the efficacy of vaccines against substances of abuse. We have conceptualized an equilibrium dialysis (ED)-based approach coupled with fluorimetry (ED-fluorimetry) to measure the antibody binding-site concentration to the ligand in an aqueous environment. The measured binding-site concentrations in monoclonal antibody (mAb) and sera samples from TT-6-AmHap-immunized rats by ED-fluorimetry are in agreement with those determined by a more established equilibrium dialysis coupled with ultraperformance liquid chromatography tandem mass spectrometry (ED-UPLC-MS/MS). Importantly, we have shown that the measured antibody binding-site concentrations to the ligand by ED-fluorimetry were not influenced by the sample serum matrix; thus, this method is valid for determining the binding-site concentration of polyclonal antibodies in sera samples. Further, we have demonstrated that under appropriate analytical conditions, this method resolved the total binding-site concentrations on a nanomolar scale with good accuracy and repeatability within the microliter sample volumes. This simple, rapid, and sample preparation-free approach has the potential to reliably perform quantitative antibody binding-site screening in serum and other more complex biological fluids.

Review of the Clinical Pharmacokinetics, Efficacy and Safety of Pembrolizumab

BACKGROUND

Treatment of various types of cancer has been improved significantly with the discovery of biologic drugs that act as immune checkpoint inhibitors (ICIs). Pembrolizumab is a humanized monoclonal anti-PD-1 antibody currently approved for the treatment of a wide range of tumors, with more indications still being investigated in ongoing clinical trials.

OBJECTIVE

The aim of this paper is to present all currently available data regarding pembrolizumab pharmacokinetic and pharmacodynamic characteristics. Also, the possibility of using predicative biomarkers to monitor patients during cancer treatment is discussed.

METHODS

Database research was carried out (PubMed, ScienceDirect). Information was gathered from original articles, the European Medicines Agency datasheets and results from clinical trials.

RESULTS

This review summarizes present-day knowledge about the pharmacokinetics, different modeling approaches and dosage regimens, efficacy and safety of pembrolizumab and therapeutic monitoring of disease progression.

CONCLUSION

This review points out consistent pharmacokinetic characteristics of pembrolizumab in various cancer patients, the lack of pharmacokinetic-pharmacodynamic/outcome relationships, the need of adequate biomarkers predicting treatment success. Hence, there is a clear necessity for more data and experience in order to optimize pembrolizumab treatment for each individual patient.

Anlotinib Downregulates RGC32 Which Provoked by Bevacizumab

Background

Bevacizumab is the representative drug in antiangiogenic therapy for lung cancer. However, it induced resistance in some neoplasm. Anlotinib, a novel multi-target tyrosine kinase inhibitor which has an inhibitory action on both angiogenesis and malignancy, is possible to reverse the resistance.

Methods

Transwell migration and invasion experiments of bevacizumab with or without anlotinib were conducted to verify the activated/inhibited ability of lung adenocarcinoma cells. We sequenced A549 cells with enhanced migration and invasion abilities after bevacizumab treatment, screened out the differentially expressed gene and further confirmed by western blot and q-PCR assays. We also investigated immunohistochemical staining of tumor tissue in mice and human lung adenocarcinoma.

Results

Bevacizumab facilitated migration and invasion of lung adenocarcinoma cells. Differentially expressed gene RGC32 was screened out. Bevacizumab upregulated the expression of RGC32, N-cadherin, and MMP2 through ERK-MAPK and PI3K-AKT pathways. Anlotinib downregulated their expression and reversed the effect of bevacizumab on A549 cells. In vivo experiments confirmed that higher-dose bevacizumab facilitated metastasis in tumor-bearing nude mice and upregulated the expression of RGC32, N-cadherin, and MMP2, whereas anlotinib abrogated its effect. Expression of both RGC32 and N-cadherin positively correlated with lymph node metastasis and stage in lung adenocarcinoma was found. Survival analysis revealed that higher expressions of RGC32 and N-cadherin were associated with poor progression-free survival and overall survival.

Conclusions

Bevacizumab may promote invasion and metastasis of lung adenocarcinoma cells by upregulating RGC32 through ERK-MAPK and PI3K-AKT pathways to promote epithelial-mesenchymal transition, whereas anlotinib reverses the effect. RGC32 and N-cadherin are independent prognostic factors in lung adenocarcinoma.

2021 White Paper on Recent Issues in Bioanalysis: Mass Spec of Proteins, Extracellular Vesicles, CRISPR, Chiral Assays, Oligos; Nanomedicines Bioanalysis; ICH M10 Section 7.1; Non-Liquid & Rare Matrices; Regulatory Inputs (Part 1A - Recommendations on Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC & Part 1B - Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine)

The 15th edition of the Workshop on Recent Issues in Bioanalysis (15th WRIB) was held on 27 September to 1 October 2021. Even with a last-minute move from in-person to virtual, an overwhelmingly high number of nearly 900 professionals representing pharma and biotech companies, contract research organizations (CROs), and multiple regulatory agencies still eagerly convened to actively discuss the most current topics of interest in bioanalysis. The 15th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on biomarker assay development and validation (BAV) (focused on clarifying the confusion created by the increased use of the term "Context of Use - COU"); mass spectrometry of proteins (therapeutic, biomarker and transgene); state-of-the-art cytometry innovation and validation; and, critical reagent and positive control generation were the special features of the 15th edition. This 2021 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 2021 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 1A) covers the recommendations on Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC. Part 1B covers the Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine. Part 2 (ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/Oral & Multispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry) and Part 3 (TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9 & CAR-T Immunogenicity; PCR & Vaccine Assay Performance; ADA Assay Comparabil ity & Cut Point Appropriateness) are published in volume 14 of Bioanalysis, issues 10 and 11 (2022), respectively.

Research Progress on Quantification Methods of Drug Concentration of Monoclonal Antibodies

Background:

With the development of monoclonal antibodies (mAbs) from the first generation of mice to the fourth generation of human origin, the efficacy and safety in the treatment of many diseases have been continuously improved. MAbs have been widely used in the treatment of cancer, chronic inflammatory diseases, and so on. However, the treatment response of mAbs varies greatly among individuals, and drug exposure may be affected by a variety of physiological and pathological factors, such as combined use of drugs and progression of disease. Therefore, studies tend to recommend therapeutic drug monitoring and individualized treatment strategies.

Objective:

In this paper, the commonly used methods of quantification of monoclonal antibodies were reviewed, especially liquid chromatography- mass spectrometry (LC-MS/MS) and enzyme-linked immunosorbent assay (ELISA), to provide technical support for therapeutic drug detection and individualize dosing for patients.

Conclusion:

For patients achieving mAbs treatment, it is necessary to carry out therapeutic drug monitoring and take it as a routine monitoring index. We recommend that for pharmaceutical laboratories in hospitals, establishing an appropriate assay formats, such as ELISA and LC-MS/MS is critical to determine drug concentration and antidrug antibody (ADA) for mAbs.

Development of an efficient mAb quantification assay by LC-MS/MS using rapid on-bead digestion

The use of monoclonal antibody (mAb) therapeutics is increasing rapidly, but mAb concentrations vary widely between individuals and might subsequently affect mAb exposure and treatment response. Precision medicine has gained much attention in recent years, but little is known about the personalized dosage of mAb therapeutics. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been demonstrated as a selective and sensitive approach to quantify mAb therapeutics in biological samples, but current methods to quantify mAbs are usually time-consuming and require tedious sample preparation. This study developed an efficient LC-MS/MS method using an on-bead trypsin digestion procedure at a higher digestion temperature. Five mAbs, bevacizumab, evolocumab, nivolumab, pembrolizumab, and trastuzumab, used for treating different diseases, were selected for method development. Tocilizumab was selected as the internal standard. The result of the on-bead digestion protocol was compared to the conventional low-pH elution method, and it showed better sensitivity and reproducibility for most mAbs. The optimized on-bead digestion protocol used 75 μL of digestion buffer at 60 °C for a 60 min digestion. The calibration curve was generated from 10 to 200 μg mL^-1. The accuracies at the three QC levels of the 5 mAbs were all within 94.5 ± 5.2% to 111.6 ± 3.7%. The repeatability and intermediate precision of the 5 mAbs were all lower than 6.1 and 9.5% RSD, respectively. The newly developed method was successfully applied to quantify trastuzumab in six breast cancer patients under different treatment cycles, and the concentrations ranged from 66.4 to 173.2 μg mL^-1. In conclusion, the developed method is more efficient and more practical for real-world analysis of a large number of clinical samples, it could be used for routine therapeutic drug monitoring, and it could contribute to personalized mAb treatment.

Development of an LC-MS/MS method to simultaneously quantify therapeutic mAbs and estimate hematocrit values in dried blood spot samples

Recently, monoclonal antibody (mAb) therapy has gained increasing attention in the medical field due to its high specificity. Dried blood spots (DBSs) have been used in various clinical fields due to their unique characteristics, such as easy transportation, low invasiveness, and home sampling. However, hematocrit (HCT)-associated issues may lead to inaccurate quantification; moreover, the HCT value is required for converting the drug concentration from DBS to plasma. To simultaneously measure HCT levels and quantify mAb concentrations in DBS samples, this study used volumetrically applied 15 μL DBS, and combined protein G purification and ethanol precipitation approaches as the sample preparation method. Sixty-two clinical samples were used to investigate the HCT estimation ability by using hemoglobin (Hb) peptides. Four mAbs, bevacizumab, trastuzumab, nivolumab and tocilizumab, were selected to demonstrate our method, and pembrolizumab was used as the internal standard. The optimized method could measure four mAbs and Hb peptides simultaneously within 11 min. Moreover, a correlation study revealed that the correlation coefficient for the Hb peptides and the HCT value was larger than 0.9. The HCT estimation results revealed that for over 90% of the real DBS samples the HCT could be obtained within ±20% estimation error acceptance criteria. The method was validated in terms of accuracy and precision for the four mAbs. The developed method was further applied to simultaneously quantify mAb concentrations and estimate HCT values in six patient DBS samples to demonstrate its clinical applicability. It is believed that this newly developed method could facilitate various clinical studies and provide benefits for mAb therapies in clinical fields.

Development and validation of a UPLC-MS/MS method to quantitate anti-PD1 monoclonal antibody (Toripalimab), and comparison with electrochemiluminescence immunoassay

Toripalimab, a humanized IgG4 monoclonal antibody (mAb) against programmed death receptor-1, is being extensively studied to treat various malignancies. At present, there is no complete methodology reported for quantifying toripalimab, except for an electrochemiluminescence immunoassay (ECLIA) mentioned in several clinical studies. Therefore, a sensitive and robust ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed to accurately detect toripalimab levels, compared with the ECLIA. Plasma samples were pretreated by a five-step process, encompassing denaturation, reduction, alkylation, enzymatic hydrolysis and quenching. And a unique, sensitive and stable enzymatic peptide (ASGYTFTDYEMHWVR) selected as surrogate of toripalimab was eluted and monitored by UPLC-MS/MS system with the linear range of 5.0375-201.5 μg/mL. After fully validated, the UPLC-MS/MS method was applied to determine 77 plasma samples from 29 patients in a phase I clinical trial, and compared with ECLIA based on 56 samples. Wilcoxon paired samples test showed toripalimab levels by UPLC-MS/MS were significantly higher than that by ECLIA (p < 0.001), though a strong correlation was observed (r = 0.96). Moreover, Passing-Bablok regression analysis exhibited constant and proportional biases: UPLC-MS/MS = 2.25 + 1.21 * ECLIA. This discrepancy could be mainly attributed to different forms determined: total mAb for UPLC-MS/MS and free mAb for ECLIA, respectively. As a result, this UPLC-MS/MS method may be complementary to ECLIA to monitor different forms of toripalimab. Beyond that, it can be easily modified to simultaneously quantitate multiple-analyte with a small volume of plasma.

Bevacizumab promotes active biological behaviors of human umbilical vein endothelial cells by activating TGFβ1 pathways off-VEGF signaling

Objective: Bevacizumab is a recombinant humanized monoclonal antibody that blocks vascular endothelial growth factor (VEGF) with clear clinical benefits. However, overall survival of some cancer types remains low owing to resistance to bevacizumab therapy. While resistance is commonly ascribed to tumor cell invasion induced by hypoxia-inducible factor (HIF), less attention has been paid to the potential involvement of endothelial cells (ECs) in vasculature activated by anti-angiogenic drugs.

Methods: Human umbilical vein ECs (HUVECs), bEnd.3 cells, and mouse retinal microvascular ECs (MRMECs) were treated with bevacizumab under conditions of hypoxia and effects on biological behaviors, such as migration and tube formation, examined. Regulatory effects on TGFβ1 and CD105 (endoglin) were established via determination of protein and mRNA levels. We further investigated whether the effects of bevacizumab could be reversed using the receptor tyrosine kinase inhibitor anlotinib.

Results: Bevacizumab upregulated TGFβ1 as well as CD105, a component of the TGFβ receptor complex and an angiogenesis promoter. Elevated CD105 induced activation of Smad1/5, the inflammatory pathway and endothelial–mesenchymal transition. The migration ability of HUVECs was enhanced by bevacizumab under hypoxia. Upregulation of CD105 was abrogated by anlotinib, which targets multiple receptor tyrosine kinases including VEGFR2/3, FGFR1-4, PDGFRα/β, C-Kit, and RET.

Conclusions: Bevacizumab promotes migration and tube formation of HUVECs via activation of the TGFβ1 pathway and upregulation of CD105 expression. Anlotinib reverses the effects of bevacizumab by inhibiting the above signals.

Cross-Validation of a Multiplex LC-MS/MS Method for Assaying mAbs Plasma Levels in Patients with Cancer: A GPCO-UNICANCER Study

BACKGROUND

Different liquid chromatography tandem mass spectrometry (LC-MS/MS) methods have been published for quantification of monoclonal antibodies (mAbs) in plasma but thus far none allowed the simultaneous quantification of several mAbs, including immune checkpoint inhibitors. We developed and validated an original multiplex LC-MS/MS method using a ready-to-use kit to simultaneously assay 7 mAbs (i.e., bevacizumab, cetuximab, ipilimumab, nivolumab, pembrolizumab, rituximab and trastuzumab) in plasma. This method was next cross-validated with respective reference methods (ELISA or LC-MS/MS).

METHODS

The mAbXmise kit was used for mAb extraction and full-length stable-isotope-labeled antibodies as internal standards. The LC-MS/MS method was fully validated following current EMA guidelines. Each cross validation between reference methods and ours included 16-28 plasma samples from cancer patients.

RESULTS

The method was linear from 2 to 100 µg/mL for all mAbs. Inter- and intra-assay precision was <14.6% and accuracy was 90.1-111.1%. The mean absolute bias of measured concentrations between multiplex and reference methods was 10.6% (range 3.0-19.9%).

CONCLUSIONS

We developed and cross-validated a simple, accurate and precise method that allows the assay of up to 7 mAbs. Furthermore, the present method is the first to offer a simultaneous quantification of three immune checkpoint inhibitors likely to be associated in patients.

Analysis of Pembrolizumab in Human Plasma by LC-MS/HRMS. Method Validation and Comparison with Elisa

Pembrolizumab is a humanized immunoglobulin G4-kappa anti-PD1 antibody used in the treatment of different solid tumors or haematological malignancies. A liquid chromatography coupled with a high resolution mass spectrometry (orbitrap technology) method was fully developed, optimized, and validated for quantitative analysis of pembrolizumab in human plasma. A mass spectrometry assay was used for the first time a full-length stable isotope-labelled pembrolizumab-like (Arginine ¹³C₆-¹⁵N₄ and Lysine ¹³C₆-¹⁵N₂) as an internal standard; the sample preparation was based on albumin depletion and trypsin digestion and, finally, one surrogate peptide was quantified in positive mode. The assay showed good linearity over the range of 1–100 μg/mL, a limit of quantification at 1 μg/mL, excellent accuracy from 4.4% to 5.1%, and also a between-day precision below 20% at the limit of quantification. In parallel, an in-house ELISA was developed with a linearity range from 2.5 to 50 µg/mL. Then, results were obtained from 70 plasma samples of cancer patients that were treated with pembrolizumab and quantified with both methods were compared using the Passing-Bablok regression analysis and Bland-Altman plotting. The LC-MS/HRMS method is easy to implement in the laboratory for use in the context of PK/PD studies, clinical trials, or therapeutic drug monitoring.

LC-MS/MS-based non-isotopically paired labeling (NIPL) strategy for the qualification and quantification of monosaccharides

Investigation into monosaccharides is critical for studies of oligosaccharides structure and function in biological processes. However, monosaccharides quantification is still challenge due to their isomeric structure and high hydrophilic properties. Besides, it was difficult to obtain isotopic internal standards (IS) of each monosaccharide in complex matrixes. Herein, we developed a novel strategy for the qualification and quantification of monosaccharides in urine using two structure analogs 1-(4-methylphenyl)-3-methyl-5-pyrazolone (MPMP) and1-phenyl-3-methyl-5-pyrazolone (PMP) as non-isotopically paired labeling (NIPL) reagents by liquid chromatograph-tandem mass spectrometry (LC-MS/MS). The derivatized monosaccharides by NIPL method not only had sufficient retention time differences on reversed-phase column, but also exhibited predominant product ion pairs (m/z 189 & m/z 175) in the multiple reaction monitoring (MRM) mode. In this method, PMP labeled standards were adopted as one-to-one internal standards (ISs). 12 urinary monosaccharides were successfully determined and the linear ranges expanded five orders of magnitude with limit of quantification (LOQ) varied from 0.09 ng mL^-1 to 0.36 ng mL^-1 as well as the accuracy higher than 98.15% and the relative standard derivation (RSD) lower than 7.92%. With assistance of multivariate analysis, the targeted monosaccharide biomarkers were firstly obtained for the diagnosis of bladder cancer. By the inexpensive NIPL reagents-MPMP/PMP, the developed strategy possessed the specific advantages of low cost, simple operation, high sensitivity and high accuracy for the qualification and quantitation of monosaccharides. As expected, this method will provide an alternative application potential for targeted metabolomics analysis.

Personalized Medicine of Monoclonal Antibodies in Inflammatory Bowel Disease: Pharmacogenetics, Therapeutic Drug Monitoring, and Beyond

The pharmacotherapy of inflammatory bowel diseases (Crohn’s disease and ulcerative colitis) has experienced significant progress with the advent of monoclonal antibodies (mABs). As therapeutic proteins, mABs display peculiar pharmacokinetic characteristics that differentiate them from chemical drugs, such as aminosalicylates, antimetabolites (i.e., azathioprine, 6-mercaptopurine, and methotrexate), and immunosuppressants (corticosteroids and cyclosporine). However, clinical trials have demonstrated that biologic agents may suffer from a pharmacokinetic variability that could influence the desired clinical outcome, beyond primary resistance phenomena. Therefore, therapeutic drug monitoring (TDM) protocols have been elaborated and applied to adaptation drug doses according to the desired plasma concentrations of mABs. This activity is aimed at maximizing the beneficial effects of mABs while sparing patients from toxicities. However, some aspects of TDM are still under discussion, including time-changing therapeutic ranges, proactive and reactive approaches, the performance and availability of instrumental platforms, the widely varying individual characteristics of patients, the severity of the disease, and the coadministration of immunomodulatory drugs. Facing these issues, personalized medicine in IBD may benefit from a combined approach, made by TDM protocols and pharmacogenetic analyses in a timeline that necessarily considers the frailty of patients, the chronic administration of drugs, and the possible worsening of the disease. Therefore, the present review presents and discusses the activities of TDM protocols using mABs in light of the most recent results, with special attention on the integration of other actions aimed at exploiting the most effective and safe therapeutic effects of drugs prescribed in IBD patients.

Use of an alternative signature peptide during development of a LC-MS/MS assay of plasma nivolumab levels applicable for multiple species

Recently, immune checkpoint inhibitors, including anti-programmed cell death protein 1 (PD-1) antibodies, have dramatically changed treatment strategies for several cancers. In pharmacokinetic/pharmacodynamic studies, experiments using a variety of animal species are assumed. We have identified optimal multiple reaction monitoring transitions for signature candidate peptides of nivolumab in human, mouse, and rat plasma and developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify nivolumab (an anti-PD-1 antibody) using trastuzumab as the internal standard. Calibration curves were linear in the range of 1-200 µg/mL. The intra- and inter-day precision and accuracy in human plasma fulfilled Food and Drug Administration guideline criteria for bioanalytical validation. There was no need to change the measurement method in mouse plasma. On the other hand, in rat plasma, an interference peak was observed at a retention time similar to that of the surrogate peptide ASGITFSNSGMHWVR (550.75 > 661.50) employed in human and mouse plasma. Therefore, we confirmed that ASQSVSSYLAWYQQKPGQAPR (785.0 > 940.2) can be used as an alternate nivolumab surrogate peptide in rat plasma at the same concentration range as used in human and mouse plasma. Using our method, the concentration range and a gradual increase in trough value were confirmed in clinical samples from two antibody-treated patients, including one with gastric cancer and one with non-small-cell lung cancer. The time course and blood concentration transition also were evaluated in nivolumab administration experiments in mouse and rat. The present study showed that the selection of the optimal peptide is essential for accurate LC-MS/MS measurement of nivolumab concentration in human, mouse, and rat plasma. The method developed here is expected to be of use in non-clinical and clinical pharmacokinetic studies.

Reliable and generic liquid chromatography/mass spectrometry quantification of short peptides using a stable-isotope-labeled labeling agent

RATIONALE

It is important to investigate the behavior of protein hydrolysate components in both in vitro and in vivo studies, to support the elucidation of their biological functions. As protein hydrolysates and biological matrices are highly complex mixtures, it is essential to apply fully reliable and flexible analytical approaches.

METHODS

A novel and generic Liquid Chromatography/Mass Spectrometry methodology was developed to analyze short peptides. A stable-isotope-labeled labeling agent 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (¹³ C₃ ) was synthesized and used to prepare internal standards from non-labeled analyte peptides. The amino acid and peptides p, pG, Pp, GPp and PpG (where p stands for hydroxyproline) were used for proof of principle.

RESULTS

The method showed acceptable performance in solvent, in simulated gastrointestinal fluid and in serum. The (linear) dynamic range expanded to over four orders of magnitude, which is very useful when multiple analytes are analyzed in a biological matrix, due to the large differences in concentrations observed for endogenous and protein hydrolysate components. The method provides absolute-quantitative results and is fully accountable on the single-sample and single-component level.

CONCLUSIONS

The methodology can be applied to reliably quantify protein hydrolysate nutraceutical components at various stages during their in vivo processing. Internal standards can also be synthesized for other short peptides whenever they are expected to have biological relevance and require quantification. Overall this provides an excellent analytical tool to support the elucidation of the biological functions of protein hydrolysate components.

Quantification of nivolumab in human plasma by LC-MS/HRMS and LC-MS/MS, comparison with ELISA

Nivolumab is a fully human immunoglobulin G4 used for the treatment of several advanced solid cancers as immune checkpoint inhibitors. There are some challenges for the quantification of mAb in plasma because IgG are present intrinsically in complex biologic matrices and this determination must be based on reliable, selective, and accurate analytical methods. This study described two validated methods carried out in two separate laboratories, one developed with a triple quadrupole tandem mass spectrometry (LC-MS/MS) and the other with high resolution mass spectrometry with an orbitrap system (LC-MS/HRMS). Both methods used full-length stable isotope-labeled nivolumab-like (Arginine ¹³C6-¹⁵N₄ and Lysine ¹³C₆-¹⁵N₂) as internal standard. The sample preparation was based on IgG immunocapture, then trypsin digestion was performed and one surrogate peptide was quantified in positive mode. Assays showed good linearity over the range of 5-100 μg/mL and 5-150 μg/mL for LC-MS/HRMS and LC-MS/MS, respectively. The limit of quantification was set at 2 and 5 μg/mL for LC-MS/HRMS and LC-MS/MS, respectively. Acceptable accuracy (from - 13.6% to 3.0%) and precision (within 20%) values were also obtained with both methods. The two LC-MS methods showed a very different matrix effect linked to the use of different analytical columns and elution gradients. Nivolumab plasma concentrations from 60 cancer outpatients were compared with the two mass spectrometry methods and also with a home-made ELISA method. The Bland-Altman analysis did not show any significant bias between the three methods. The Passing-Bablock linear regression analysis showed a good agreement between the three methods with a better correlation between the two mass spectrometry methods.

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.

Bottom-up sample preparation for the LC-MS/MS quantification of anti-cancer monoclonal antibodies in bio matrices

Therapeutic monoclonal antibodies (mAbs) are rapidly taking over the treatment of many malignancies, and an astonishing number of mAbs is in development. This causes a high demand for quantification of mAbs in biomatrices both for measuring therapeutic mAb concentrations and to support pharmacokinetics and pharmacodynamics studies. Conventionally, ligand-binding assays are used for these purposes, but LC-MS is gaining popularity. Although intact (top-down) and subunit (middle-down) mAb quantification is reported, signature peptide (bottom-up) quantification is currently most advantageous. This review provides an overview of the reported bottom-up mAb quantification methods in biomatrices as well as general recommendations regarding signature peptide and internal standard selection, reagent use and optimization of digestion in bottom-up quantification methods.

Approaching sites of action of drugs in clinical pharmacology: New analytical options and their challenges

Clinical pharmacology is an important discipline for drug development aiming to define pharmacokinetics (PK), pharmacodynamics (PD) and optimum exposure to drugs, i.e. the concentration-response relationship and its modulators. For this purpose, information on drug concentrations at the anatomical, cellular and molecular sites of action is particularly valuable. In pharmacological assays, the limited accessibility of target cells in readily available samples (i.e. blood) often hampers mass spectrometry-based monitoring of the absolute quantity of a compound and the determination of its molecular action at the cellular level. Recently, new sample collection methods have been developed for the specific capture of rare circulating cells, especially for the diagnosis of circulating tumour cells. In parallel, new advances and developments in mass spectrometric instrumentation now allow analyses to be scaled down to the cellular level. Together, these developments may permit the monitoring of minute drug quantities and show their effect at the cellular level. In turn, such PK/PD associations on a cellular level would not only enrich our pharmacological knowledge of a given compound but also expand the basis for PK/PD simulations. In this review, we describe novel concepts supporting clinical pharmacology at the anatomical, cellular and molecular sites of action, and highlight the new challenges in mass spectrometry-based monitoring. Moreover, we present methods to tackle these challenges and define future needs.

Development and validation of an LC-MS/MS method for simultaneous quantification of co-administered trastuzumab and pertuzumab

Given the increasing use of combination therapy with multiple monoclonal antibodies (mAbs), there is a clinical need for multiplexing assays. For the frequently co-administered anti-human epidermal growth factor receptor 2 (HER2) mAbs trastuzumab and pertuzumab, we developed a high-throughput and robust hybrid ligand-binding liquid chromatography-mass spectrometry (LC-MS)/MS quantitative assay. Nanomolar concentrations of trastuzumab and pertuzumab were determined in 10 µL serum samples after extraction by affinity purification through protein A beads, followed by on-bead reduction, alkylation, and trypsin digestion. After electrospray ionization, quantification was obtained by multiple reaction monitoring LC-MS/MS using SILuMab as an internal standard. The method was validated according to the current guidelines from the US Food and Drug Administration and the European Medicines Agency. Assay linearity was established in the ranges 0.250-250 μg/mL for trastuzumab and 0.500-500 μg/mL for pertuzumab. The method was accurate and selective for the simultaneous determination of trastuzumab and pertuzumab in clinical samples, thereby overcoming the limitation of ligand binding assays that cannot quantify mAbs targeting the same receptor. Furthermore, this method requires a small blood volume, which reduces blood collection time and stress for patients. The assay robustness was verified in a clinical trial where trastuzumab and pertuzumab concentrations were determined in 670 serum samples. As we used commercially available reagents and standards, the described generic bioanalytical strategy can easily be adapted to multiplex quantifications of other mAb combinations in non-clinical and clinical samples.

Quantification of the anti-murine PD-1 monoclonal antibody RMP1-14 in BALB/c mouse plasma by liquid chromatography-tandem mass spectrometry and application to a pharmacokinetic study

RMP1-14 is a monoclonal antibody that targets the murine PD-1 protein, and has been used extensively to probe the effects of PD-1 inhibition in preclinical murine models. However, to date, no quantitative analytical methods have been published for RMP1-14. To evaluate its anti-tumor activity in BALB/c mice inoculated with CT26.WT murine colon cancer cells, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify RMP1-14 in BALB/c mouse K₃EDTA plasma was developed and validated. The methodology used a signature peptide (GFYPPDIYTEWK) as a surrogate for RMP1-14 quantitation and an isotopically labeled analog of the signature peptide as the internal standard. Initial method development focused on a hybrid LC-MS/MS assay involving Protein G immunoprecipitation, but this strategy was abandoned due to lack of selectivity. The final validated method consisted of dilution with Tris-buffered saline, trypsin digestion, and desalting using micro solid-phase extraction. Analytical run time was 3.50 min, and the method demonstrated linearity between 0.500 and 50.0 μg/mL of intact RMP1-14. Accuracy, precision, and robustness were all acceptable, and the method was demonstrated to be comparable to a commercially available fit-for-purpose enzyme-linked immunosorbent assay (ELISA) capable of measuring RMP1-14. The validated method was used to generate pharmacokinetic parameters from tumor-bearing BALB/c mice dosed with RMP1-14 at either 2.50 or 7.50 mg/kg. Overall, the validated method represents a novel tool that can be used to evaluate RMP1-14 activity in future immuno-oncology studies.

Determination of Cetuximab in Plasma by Liquid Chromatography-High-Resolution Mass Spectrometry Orbitrap With a Stable Labeled 13C,15N-Cetuximab Internal Standard

BACKGROUND

Cetuximab (CTX) is a chimeric IgG1 Kappa monoclonal antibody used to treat head and neck cancer and colorectal cancer. Previous clinical studies indicated that the pharmacokinetics of CTX influences patient survival. Thus, individualizing CTX treatment by measuring trough levels of the drug in plasma could have a major impact on clinical efficacy.

METHODS

To measure these levels, a full-length stable isotope-labeled CTX standard was used in a generic, rapid, and high-throughput sample preparation protocol based on IgG capture followed by trypsin digestion, on-line solid-phase extraction cleanup, and liquid chromatography-high resolution mass spectrometry (LC-HRMS).

RESULTS

The optimized method displayed good analytical performance and was linear over a range from 5 to 150 mcg/mL. The within-run and between-run imprecision of the assay were equal to or less than 10%, for 6 replicates at 3 different concentrations and for runs performed on 5 separate days. The plasma CTX concentrations in 19 patients were also determined.

CONCLUSIONS

The results showed that quantification of mAb in clinical samples does not strictly require a tandem mass spectrometry system, and LC-HRMS is also relevant in this context. This first study implementing a quantitative LC-HRMS assay with a specific stable isotope-labeled mAb internal standard paves the way for more robust clinical monitoring of anticancer mAbs.

Six-step workflow for the quantification of therapeutic monoclonal antibodies in biological matrices with liquid chromatography mass spectrometry - A tutorial

The promising pipeline of therapeutic monoclonal antibodies (mAbs) demands robust bioanalytical methods with swift development times for pharmacokinetic studies. Over the past decades ligand binding assays were the methods of choice for absolute quantification. However, the production of the required anti-idiotypic antibodies and ligands limits high-throughput method development for sensitive, accurate, and reproducible quantification of therapeutic mAbs. In recent years, high-resolution liquid chromatography tandem mass-spectrometry (LC-MS) systems have enabled absolute quantification of therapeutic mAbs with short method development times. These systems have additional benefits, such as a large linear dynamic range, a high specificity and the option of multiplexing. Here, we briefly discuss the current strategies for the quantification of therapeutic mAbs in biological matrices using LC-MS analysis based on top-down and middle-down quantitative proteomics. Then, we present the widely used bottom-up method in a six-step workflow, which can be used as guidance for quantitative LC-MS/MS method development of mAbs. Finally, strengths and weaknesses of the bottom-up method, which currently provides the most benefits, are discussed in detail.

A multiplex liquid chromatography tandem mass spectrometry method for the quantification of seven therapeutic monoclonal antibodies: Application for adalimumab therapeutic drug monitoring in patients with Crohn's disease

The use of therapeutic monoclonal antibodies (mAbs) is steadily increasing. Previous studies have reported the clinical interest of mAb therapeutic-drug monitoring (TDM), including that of adalimumab, for patients with Crohn's disease (CD). Proof of concept mAb-quantification studies by liquid chromatography mass spectrometry (LC-MS/MS) have been published, but a specific and reliable routine-suited multiplex quantification method is still needed to facilitate mAb TDM. We describe an electrospray ionization LC-MS/MS method for the simultaneous quantification of seven mAbs (adalimumab, cetuximab, infliximab, rituximab, secukinumab, tocilizumab, and trastuzumab) in human plasma. Sample preparation was performed using protein-G purification and trypsin digestion to obtain proteotypic peptides. We retrospectively measured the adalimumab concentration in 65 plasma samples from 56 CD patients and determined the adalimumab therapeutic cut-off concentration associated with biological remission. Calibration curves were linear from 1 to 100 μg mL^-1, except for rituximab (5-100 μg mL^-1). This method was reproducible, repeatable, and accurate (coefficient of variation and bias < 20%), with no cross contamination. Adalimumab concentrations were significantly higher (p = 0.0198) for patients with biological remission (median: 11.3 μg mL^-1 [4.6; 18.3]) than that for patients without a biological response (9.5 μg mL^-1 [3.94;17.0]). An adalimumab cut-off concentration of 8.0 μg mL^-1 correctly discriminated patients with or without biological remission (sensitivity: 74.1%, specificity: 57.9%). This validated LC-MS/MS routine-suited method is the first allowing simultaneous quantification of up to seven mAbs acting against different pharmacological targets. It opens the field of TDM to numerous mAbs.

Simple and rapid analysis of tocilizumab using HPLC-fluorescence detection method

We developed a novel assay using high-performance liquid chromatography (HPLC) with fluorescence detection for the determination of tocilizumab (TCZ), after it has undergone a facile and rapid pretreatment. TCZ belongs to the same subclass as IgG1 (Immunoglobulin G subclass 1), and we could separate TCZ from IgG1 without antigen-antibody reactions, with the novel detection method. The separation of these antibodies was achieved by pretreatment with an organic solvent containing a base, such as trimethylamine and triethylamine. The effect of these bases on the separation of TCZ is related to the hydrophobicity of the base rather than the electrostatic charge. The results indicated that the surface charge of antibodies changed because of the structural change, even though the difference in the amino acid sequences of the antibodies was very low. Our method is available for the separation of the antibody subclasses, and it would be useful to assay TCZ in blood.