Bringing mass spectrometry into the care of patients with multiple myeloma

Detecting M-Protein via Mass Spectrometry and Affinity Beads: Enrichment With Mixed Kappa-Lambda Beads Enables Prompt Application in Clinical Laboratories

Background

Detecting monoclonal protein (M-protein), a hallmark of plasma cell disorders, traditionally relies on methods such as protein electrophoresis, immune-electrophoresis, and immunofixation electrophoresis (IFE). Mass spectrometry (MS)-based methods, such as matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and electrospray ionization-quadrupole time-of-flight (ESI-qTOF) MS, have emerged as sensitive methods. We explored the M-protein-detection efficacies of different MS techniques.

Methods

To isolate immunoglobulin and light chain proteins, six types of beads (IgG, IgA, IgM, kappa, lambda, and mixed kappa and lambda) were used to prepare samples along with CaptureSelect nanobody affinity beads (NBs). After purification, both MALDI-TOF MS and liquid chromatography coupled with Synapt G2 ESI-qTOF high-resolution MS analysis were performed. We purified 25 normal and 25 abnormal IFE samples using NBs and MALDI-TOF MS (NB-MALDI-TOF).

Results

Abnormal samples showed monoclonal peaks, whereas normal samples showed polyclonal peaks. The IgG and mixed kappa and lambda beads showed monoclonal peaks following the use of daratumumab (an IgG/kappa type of monoclonal antibody) with both MALDI-TOF and ESI-qTOF MS analysis. The limits of detection for MALDI-TOF MS and ESI-qTOF MS were established as 0.1 g/dL and 0.025 g/dL, respectively. NB-MALDI-TOF and IFE exhibited comparable sensitivity and specificity (92% and 92%, respectively).

Conclusions

NBs for M-protein detection, particularly with mixed kappa-lambda beads, identified monoclonal peaks with both MALDI-TOF and ESI-qTOF analyses. Qualitative analysis using MALDI-TOF yielded results comparable with that of IFE. NB-MALDI-TOF might be used as an alternative method to replace conventional tests (such as IFE) to detect M-protein with high sensitivity.

Evaluating the HYDRASHIFT 2/4 Daratumumab assay: a powerful approach to assess treatment response in multiple myeloma

OBJECTIVES

This study evaluates the HYDRASHIFT assay's effectiveness in mitigating daratumumab interference on serum protein tests during multiple myeloma (MM) treatment, aiming to ensure an accurate assessment of treatment response.

METHODS

We analyzed 113 serum samples from 68 MM patients undergoing daratumumab treatment, employing both standard IF and the HYDRASHIFT assay. The assay's precision was determined through intra-day and inter-day variability assessments, while its specificity was verified using serum samples devoid of daratumumab. Comparative analysis of IF results, before and after the application of the HYDRASHIFT assay, facilitated the categorization of treatment responses in alignment with the International Myeloma Working Group's response criteria.

RESULTS

The precision underscored the assay's consistent repeatability and reproducibility, successfully eliminating interference of daratumumab-induced Gκ bands. Specificity assessments demonstrated the assay's capability to distinguish daratumumab from both isatuximab and naturally occurring M-proteins. Of the analyzed cases, 91 exhibited successful migration of daratumumab-induced Gκ bands, thereby enhancing the accuracy of treatment response classification. The remaining 22 cases did not show a visible migration complex, likely due to the low concentration of daratumumab in the serum. These findings underscore the assay's critical role in distinguishing daratumumab from endogenous M-protein, particularly in samples with a single Gκ band on standard IF, where daratumumab and endogenous M-protein had co-migrated.

CONCLUSIONS

The HYDRASHIFT assay demonstrates high precision, specificity, and utility in the accurate monitoring of treatment responses in MM patients receiving daratumumab. This assay represents a significant advancement in overcoming the diagnostic challenges posed by daratumumab interference.

Monitoring Minimal Residual Disease in Patients with Multiple Myeloma by Targeted Tracking Serum M-Protein Using Mass Spectrometry (EasyM)

PURPOSE

We investigated both the clinical utilities and the prognostic impacts of the clonotypic peptide mass spectrometry (MS)-EasyM, a blood-based minimal residual disease (MRD) monitoring protocol in multiple myeloma.

EXPERIMENTAL DESIGN

A total of 447 sequential serum samples from 56 patients with multiple myeloma were analyzed using EasyM. Patient-specific M-protein peptides were sequenced from diagnostic samples; sequential samples were quantified by EasyM to monitor the M-protein. The performance of EasyM was compared with serum immunofixation electrophoresis (IFE), bone marrow multiparameter flow cytometry (MFC), and next-generation flow cytometry (NGF) detection. The optimal balance of EasyM sensitivity/specificity versus NGF (10-5 sensitivity) was determined and the prognostic impact of MS-MRD status was investigated.

RESULTS

Of the 447 serum samples detected and measured by EasyM, 397, 126, and 92 had time-matching results for comparison with serum IFE, MFC-MRD, and NGF-MRD, respectively. Using a dotp >0.9 as the MS-MRD positive, sensitivity was 99.6% versus IFE and 100.0% versus MFC and NGF. Using an MS negative cutoff informed by ROC analysis (<1.86% of that at diagnosis), EasyM sensitivity remained high versus IFE (88.3%), MFC (85.1%), and NGF (93.2%), whereas specificity increased to 90.4%, 55.8%, and 93.2%, respectively. In the multivariate analysis, older diagnostic age was an independent predictor for progression-free survival [PFS; high risk (HR), 3.15; 1.26-7.86], the best MS-MRD status (MS-MRD negative) was independent predictor for both PFS (HR, 0.25; 0.12-0.52) and overall survival (HR, 0.16; 0.06-0.40).

CONCLUSIONS

EasyM is a highly sensitive and minimal invasive method of MRD monitoring in multiple myeloma; MS-MRD had significant predictive ability for survival outcomes.

A Qualitative Method to Detect Paraproteins from Serum Using Ultra Performance Liquid Chromatography Electrospray Triple Quadrupole Mass Spectrometry

BACKGROUND

Mass spectrometry-based techniques are increasingly reported in the literature for identifying paraproteins due to their improved specificity and sensitivity. The present study demonstrates the capability of ultra performance liquid chromatography (UPLC) electrospray ionization triple quadrupole mass spectrometry for the qualitative analysis of paraproteins.

METHODS

Paraproteins from patient serum (n = 40) were immunopurified using agarose beads coated with camelid antibodies that are specific for various subtypes of immunoglobulins (Igs; G, A, M, and light chains κ, λ). The extracted Igs are reduced to separate light chains from heavy chains in solution. The reduced sample was subjected to UPLC and mass measured using electrospray ionization-mass spectrometry. The mass spectral peaks at specific retention times were deconvoluted after clean-up to obtain the mass of light chains. The interpretation of liquid chromatography peaks and LC-MS data was validated by comparing them with immunofixation electrophoresis (IFE) results.

RESULTS

The interpretation from the chromatographic pattern had a 92.5% (37/40) agreement when compared with mass information. The correlation of mass spectrometry data to IFE was 90% (36/40). The high mass of light chains (>25 kDa) was suggestive of glycosylation. Patient sera positive for IgGκ on IFE (n = 15) were analyzed for the interference of tAbs. The mass of Daratumumab observed in a sample was confirmed by the treating physician. A biclonal of same isotype (IgGκ) was identified.

CONCLUSIONS

The feasibility of using liquid chromatography triple quadrupole mass spectrometry for the identification of the subtype of paraproteins has been demonstrated. The method's applicability to screen for interference from tAbs and identification of biclonals of the same isotype has been highlighted.

M-protein diagnostics in multiple myeloma patients using ultra-sensitive targeted mass spectrometry and an off-the-shelf calibrator

OBJECTIVES

Minimal residual disease status in multiple myeloma is an important prognostic biomarker. Recently, personalized blood-based targeted mass spectrometry (MS-MRD) was shown to provide a sensitive and minimally invasive alternative to measure minimal residual disease. However, quantification of MS-MRD requires a unique calibrator for each patient. The use of patient-specific stable isotope labelled (SIL) peptides is relatively costly and time-consuming, thus hindering clinical implementation. Here, we introduce a simplification of MS-MRD by using an off-the-shelf calibrator.

METHODS

SILuMAB-based MS-MRD was performed by spiking a monoclonal stable isotope labeled IgG, SILuMAB-K1, in the patient serum. The abundance of both M-protein-specific peptides and SILuMAB-specific peptides were monitored by mass spectrometry. The relative ratio between M-protein peptides and SILuMAB peptides allowed for M-protein quantification. We assessed linearity, sensitivity and reproducibility of SILuMAB-based MS-MRD in longitudinally collected sera from the IFM-2009 clinical trial.

RESULTS

A linear dynamic range was achieved of over 5 log scales, allowing for M-protein quantification down to 0.001 g/L. The inter-assay CV of SILuMAB-based MS-MRD was on average 11 %. Excellent concordance between SIL- and SILuMAB-based MS-MRD was shown (R2>0.985). Additionally, signal intensity of spiked SILuMAB can be used for quality control purpose to assess system performance and incomplete SILuMAB digestion can be used as quality control for sample preparation.

CONCLUSIONS

Compared to SIL peptides, SILuMAB-based MS-MRD improves the reproducibility, turn-around-times and cost-efficacy of MS-MRD without diminishing its sensitivity and specificity. Furthermore, SILuMAB can be used as a MS-MRD quality control tool to monitor sample preparation efficacy and assay performance.

M-protein detection by mass spectrometry for minimal residual disease in multiple myeloma

Multiple myeloma (MM) is characterized by excessive production of monoclonal immunoglobulins (M proteins). Routine screening methods for M proteins to assess prognosis are unable to detect low levels of M proteins produced by residual tumor cells, ie, minimal residual disease (MRD). Assessment of MRD can be conducted by examining residual tumor cells in bone marrow or circulating M proteins. Advances in mass spectrometry have enabled reliable and highly sensitive detection of low abundance serum biomarkers making it a viable and significantly less invasive approach. Mass spectrometry can achieve dynamic monitoring of MRD and identify therapeutic monoclonal antibodies as well as oligoclonal proteins. In this review we summarize mass spectrometry methods in M protein detection and their applications of MRD detection in MM.

A sensitive high-resolution mass spectrometry method for quantifying intact M-protein light chains in patients with multiple myeloma

To determine the disease status and the response to treatment for patients with multiple myeloma, measuring serum M-protein levels is a widely used alternative to invasive punctures to count malignant plasma cells in the bone marrow. However, the quantification of this monoclonal antibody, which varies from patient to patient, poses significant analytical challenges. This paper describes a sensitive and specific mass spectrometry assay that addresses two objectives: to overcome the potential interference of biotherapeutics in the measurement of M-proteins, and to determine the depth of response to treatment by assessing minimal residual disease. After immunocapture of immunoglobulins and free light chains in serum, heavy and light chains were dissociated by chemical reduction and separated by liquid chromatography. M-proteins were analyzed by high-resolution mass spectrometry using a method combining a full MS scan for isotyping and identification and a targeted single ion monitoring scan for quantification. This method was able to discriminate M-protein from the therapeutic antibody in all patient samples analyzed and allowed quantification of M-protein with a LLOQ of 2.0 to 3.5 µg/ml in 5 out of 6 patients. This methodology appears to be promising for assessing minimal residual disease with sufficient sensitivity, specificity, and throughput.

Advances in minimal residual disease monitoring in multiple myeloma

Multiple myeloma (MM) is characterized by the clonal expansion of plasma cells and the excretion of a monoclonal immunoglobulin (M-protein), or fragments thereof. This biomarker plays a key role in the diagnosis and monitoring of MM. Although there is currently no cure for MM, novel treatment modalities such as bispecific antibodies and CAR T-cell therapies have led to substantial improvement in survival. With the introduction of several classes of effective drugs, an increasing percentage of patients achieve a complete response. This poses new challenges to traditional electrophoretic and immunochemical M-protein diagnostics because these methods lack sensitivity to monitor minimal residual disease (MRD). In 2016, the International Myeloma Working Group (IMWG) expanded their disease response criteria with bone marrow-based MRD assessment using flow cytometry or next-generation sequencing in combination with imaging-based disease monitoring of extramedullary disease. MRD status is an important independent prognostic marker and its potential as a surrogate endpoint for progression-free survival is currently being studied. In addition, numerous clinical trials are investigating the added clinical value of MRD-guided therapy decisions in individual patients. Because of these novel clinical applications, repeated MRD evaluation is becoming common practice in clinical trials as well as in the management of patients outside clinical trials. In response to this, novel mass spectrometric methods that have been developed for blood-based MRD monitoring represent attractive minimally invasive alternatives to bone marrow-based MRD evaluation. This paves the way for dynamic MRD monitoring to allow the detection of early disease relapse, which may prove to be a crucial factor in facilitating future clinical implementation of MRD-guided therapy. This review provides an overview of state-of-the-art of MRD monitoring, describes new developments and applications of blood-based MRD monitoring, and suggests future directions for its successful integration into the clinical management of MM patients.

Liquid chromatography–tandem mass spectrometry for clinical diagnostics

Mass spectrometry is a powerful analytical tool used for the analysis of a wide range of substances and matrices; it is increasingly utilized for clinical applications in laboratory medicine. This Primer includes an overview of basic mass spectrometry concepts, focusing primarily on tandem mass spectrometry. We discuss experimental considerations and quality management, and provide an overview of some key applications in the clinic. Lastly, the Primer discusses significant challenges for implementation of mass spectrometry in clinical laboratories and provides an outlook of where there are emerging clinical applications for this technology.

Tandem mass spectrometry is increasingly utilized for clinical applications in laboratory medicine. In this Primer, Thomas et al. discuss experimental considerations and quality management for implementing clinical tandem mass spectrometry in the clinic with an overview of some key applications.