Characteristics of isatuximab-derived interference in serum protein electrophoresis and immunofixation, and an absence of sustained in vivo interference due to belantamab mafodotin and denosumab

OBJECTIVES

Some therapeutic monoclonal antibodies, like daratumumab and elotuzumab, produce interfering monoclonal bands on serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE). Whether other common therapeutic antibodies also produce interference has not been systematically evaluated.

DESIGN AND METHODS

SPEP/IFE from patients receiving isatuximab (48 patients), belantamab mafodotin (BM; 41), and denosumab (41) were retrospectively reviewed for therapeutic antibody interference. Cases exhibiting isatuximab interference were quantified and the maximum duration of isatuximab effect was evaluated. To characterize band position, neat human serum was spiked with BM or denosumab at supratherapeutic concentrations. Band migration patterns were compared on SPEP and IFE, with band position expressed relative to other constant protein fractions.

RESULTS

Isatuximab-induced IFE interference was common (81.3 % of evaluated patients) with a maximum observed duration of 8 weeks. 10.4 % of isatuximab patients had IgG kappa monoclonal gammopathies that co-migrated with the drug; this subset could benefit from HYDRASHIFT 2/4 isatuximab testing. 8.3 % of IFE cases were negative for an isatuximab band but showed large, endogenous M-spikes migrating elsewhere. All patients in this group expired within 1 year of this finding. We hypothesize that an inability to detect isatuximab in this setting corresponds to a large residual myeloma burden that reduces isatuximab serum concentration. This observation may serve as a negative prognostic factor. Spiking studies demonstrated that BM and denosumab produce interference in vitro, but sustained interference was not observed in >40 treated patients.

CONCLUSIONS

Therapeutic antibody interference in patients receiving isatuximab is common, and can persist for at least 8 weeks after administration. >10 % of patients receiving isatuximab may benefit from HYDRASHIFT testing post-therapy. In contrast, BM and denosumab fail to produce sustained interference in treated patients.

Screening for and diagnosis of monoclonal gammopathy

Monoclonal gammopathy is a spectrum of disorders characterised by clonal proliferation of plasma cells or lymphocytes, which produce abnormal immunoglobulin or its components (monoclonal proteins). Monoclonal gammopathies are often categorised as low-tumour-burden diseases (eg, amyloid light chain (AL) amyloidosis), premalignant disorders (such as monoclonal gammopathy of undetermined significance and smouldering multiple myeloma), and malignancies (eg, multiple myeloma and Waldenström's macroglobulinaemia). Such diversity of concentration and structure makes monoclonal protein a challenging clonal marker. This article provides an overview on initial laboratory testing of monoclonal gammopathy to guide clinicians and laboratory professionals in the selection and interpretation of appropriate investigations.

An unusual pattern in serum protein electrophoresis to take in mind: A case report

Here we described a case of an asymptomatic 73 years-old female patient in geriatric routine consultation, whose laboratory testing showed hyperproteinemia with accompanying hyperglobulinemia. A diagnosis of BGUS was made only after a correlation among SPEP, densitometry tracing and IFE results was established, evidencing a second peak, that was less evident and not reported at first. These biclonal conditions are of very low incidence in the clinical laboratory, requiring the laboratory professional to have particular skills for their identification. As far as is known, clinical findings in BGUS are similar to those found in MGUS. However, they remain not well understood. Therefore, for an accurate diagnosis of BGUS, the clinical laboratory technician must be trained and sensitized to detect a second M - protein as a band or peak; taking in mind the possible different scenarios in heavy and light chain typing.

A thin-film interferometry-based label-free immunoassay for the detection of daratumumab interference in serum protein electrophoresis

BACKGROUND

Daratumumab (DARA) is a fully human anti-CD38 IgG1-κ monoclonal antibody drug used in the treatment of multiple myeloma (MM). While serum protein electrophoresis (SPEP) is an important assay for diagnosis and monitoring of patients with MM, DARA can appear in the γ-region as a single band and interfere with the interpretation of SPEP results. An approach to detect the interference is measuring the quantity of DARA in serum samples and assessing its impact on SPEP results. Immunoassays based on label-free technologies, i.e. label-free immunoassays (LFIA's), can achieve real-time immunometric measurement without attaching a reporter molecule (enzyme, fluorophore, etc.) to the immunocomplex. The recorded time course of the immunocomplex formation allows for quantitation on initial binding rate, which facilitates rapid measurement within a few minutes. Based on the thin-film interferometry (TFI) technology, a rapid LFIA was established for the quantitation of DARA in serum samples.

METHODS

The TFI-based LFIA for DARA was validated for imprecision (CV), accuracy, limit of quantitation (LOQ), and analytical measurement range (AMR). Interference to the LFIA was evaluated using a group of protein samples, as well as hemolytic, lipemic, and icteric clinical samples.

RESULTS

The precision of the TFI-based LFIA's for DARA ranged from 6.5% to 10.7% (within-run CV), and 7.4% to 11.6% (between-run CV), with a bias of -2.1% to 10.1%. The LOQ was 10 μg/ml (n = 4, CV 9.8%), with an AMR ranging from the LOQ to 1000 μg/ml. The LFIA was used to measure 37 patient samples submitted for SPEP testing. The LFIA results were 100% consistent with the history of DARA use as documented in the medical record.

CONCLUSIONS

The TFI-based LFIA was successful at accurately identifying DARA in serum samples and can be used to identify DARA interference in SPEP testing. This work demonstrates the applicability of label-free technologies, particularly the TFI technology, to clinical diagnostic needs. Given the simplicity and the speed of the testing process, the TFI technology provides a unique testing approach for the measurement of proteins in clinical samples.

MALDI-TOF mass spectrometry distinguishes daratumumab from M-proteins

BACKGROUND

Daratumumab, a therapeutic IgG kappa monoclonal antibody, can cause a false positive interference on electrophoretic assays that are routinely used to monitor patients with monoclonal gammopathies. In this study, we evaluate the ability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to distinguish daratumumab from disease-related IgG kappa monoclonal proteins (M-protein).

METHODS

Waste clinical samples from 31 patients who were receiving daratumumab and had a history of IgG kappa monoclonal gammopathy were collected. Immunoglobulins were purified from serum and analyzed by MALDI-TOF MS. Mass spectra were assessed for the presence of distinct monoclonal proteins. For samples in which only one monoclonal peak was identified near the expected m/z of daratumumab, the Hydrashift 2/4 Daratumumab Assay was used to confirm the presence of an M-protein.

RESULTS

Using MALDI-TOF MS, daratumumab could be distinguished from M-proteins in 26 out of 31 samples (84%). Results from 2 samples were inconclusive since the M-protein was not detected by the Hydrashift assay and may also be undetectable by MALDI-TOF MS. Comparatively, daratumumab was distinguishable from M-proteins in 14 out of 31 samples (45%) by immunofixation.

CONCLUSIONS

MALDI-TOF MS offers greater specificity compared to immunofixation for distinguishing daratumumab from M-proteins.

Implications of Monoclonal Antibody Therapeutics Use for Clinical Laboratory Testing

BACKGROUND

Monoclonal antibody therapeutics (MATs) represent a rapidly expanding class of biological drugs used to treat a variety of diseases. The widespread use of MATs increasingly affects clinical laboratory medicine.

CONTENT

This review provides an overview of MATs currently approved for clinical use in the US, starting from basic biology of antibodies to the engineering, pharmacokinetic and pharmacodynamic properties, nomenclature, and production of MATs. Immunogenicity and the production of antidrug antibodies (ADAs) play a major role in loss of therapeutic response and the development of treatment failure to certain MATs. Laboratory-based monitoring for MATs and detection of ADAs represent emerging needs for optimizing the use of MATs to achieve the best outcomes at affordable cost. In addition, the increased use of MATs affects clinical laboratory testing by interference of MATs with clinical laboratory tests across different areas of laboratory medicine, including histocompatibility, blood bank, and monoclonal protein testing.

SUMMARY

The number of MATs is rapidly growing each year to address previously unmet clinical needs. Laboratory monitoring of MATs and detecting ADAs represent expanding areas of laboratory testing. Test-based strategies allow for treatment optimization at the level of the individual patient, thus providing a personalized medicine approach. In addition, clinical laboratories must be aware that the increasing use of MATs affects laboratory testing and be ready to implement methods to eliminate or mitigate interference with clinical tests.

Interference of Therapeutic Monoclonal Antibodies With Routine Serum Protein Electrophoresis and Immunofixation in Patients With Myeloma: Frequency and Duration of Detection of Daratumumab and Elotuzumab

OBJECTIVES

We investigated the frequency and pattern of detection of therapeutic monoclonal antibodies (t-mAbs) daratumumab and elotuzumab by routine serum protein electrophoresis (SPE) and immunofixation (IF) in treated patients with myeloma.

METHODS

Detection of t-mAb was assessed in 22 patients by retrospective review of SPE/IF ordered prior to, during, and after 26 individual courses of therapy.

RESULTS

t-mAb was distinguishable from M-protein in 16 of 26 courses, with daratumumab detected in nine of nine and elotuzumab in six of seven patients. t-mAb was detected on first follow-up SPE/IF in 12 patients, with earliest detection 7 days after therapy initiation and latest detection 70 days after therapy. t-mAb persisted throughout induction therapy in most patients, with loss of detection during maintenance daratumumab.

CONCLUSIONS

When distinguishable from M-protein, t-mAbs are detectable in 93% of treated patients as soon as 7 days after the initial dose and are consistently observed throughout induction therapy, warranting increased monitoring and careful interpretation of SPE/IF.

Cinderella in Serum Protein Electrophoresis

Paraproteinemia is characterised by clonal proliferation of plasma cells. A common laboratory finding in paraproteinemia being a monoclonal peak in serum protein electrophoresis (M band). But there are factors which produce a peak similar to M spike in serum protein electrophoresis and these factors are known as pseudoparaproteins. This case report discusses a rare cause of pseudo M spike in a known case of autoimmune hemolytic anaemia due to administration of drug-Rituximab, a monoclonal antibody by itself.

Treatment of multiple myeloma with monoclonal antibodies and the dilemma of false positive M-spikes in peripheral blood

OBJECTIVES

To characterize the effect of three humanized IgG κ monoclonal antibodies (daratumumab, isatuximab, and elotuzumab) on the interpretation of results generated by protein electrophoresis, immunofixation, free light chain, and heavy/light chain assays performed on human serum.

METHODS

Healthy volunteer serum and serum from multiple myeloma patients were supplemented with clinically relevant concentrations of each of the three monoclonal antibodies. These specimens then underwent analysis via serum protein electrophoresis, immunofixation, serum free light chain quantification, heavy/light chain quantification, total IgG, and total protein. In addition, serum specimens from patients who had undergone treatment with elotuzumab for multiple myeloma underwent similar analysis.

RESULTS

Addition of the study drugs to serum from both the healthy donor as well as multiple myeloma patients resulted in a visible and quantifiable M-protein on SPEP and a visible IgGκ band by IFE. Increases were also noted in total IgG, IgGκ, and IgGκ/IgGλ-ratios. Analysis of serum from multiple myeloma patients receiving study drug showed similar findings with an additional IgGκ band and quantifiable M-protein with similar migration patterns in specimens drawn after administration.

CONCLUSION

The treatment of multiple myeloma patients with monoclonal antibodies results in a visible and quantifiable M-protein that has the potential to falsely indicate poor response to therapy.

Clinical efficacy and management of monoclonal antibodies targeting CD38 and SLAMF7 in multiple myeloma

Immunotherapeutic strategies are emerging as promising therapeutic approaches in multiple myeloma (MM), with several monoclonal antibodies in advanced stages of clinical development. Of these agents, CD38-targeting antibodies have marked single agent activity in extensively pretreated MM, and preliminary results from studies with relapsed/refractory patients have shown enhanced therapeutic efficacy when daratumumab and isatuximab are combined with other agents. Furthermore, although elotuzumab (anti-SLAMF7) has no single agent activity in advanced MM, randomized trials in relapsed/refractory MM have demonstrated significantly improved progression-free survival when elotuzumab is added to lenalidomide-dexamethasone or bortezomib-dexamethasone. Importantly, there has been no significant additive toxicity when these monoclonal antibodies are combined with other anti-MM agents, other than infusion-related reactions specific to the therapeutic antibody. Prevention and management of infusion reactions is important to avoid drug discontinuation, which may in turn lead to reduced efficacy of anti-MM therapy. Therapeutic antibodies interfere with several laboratory tests. First, interference of therapeutic antibodies with immunofixation and serum protein electrophoresis assays may lead to underestimation of complete response. Strategies to mitigate interference, based on shifting the therapeutic antibody band, are in development. Furthermore, daratumumab, and probably also other CD38-targeting antibodies, interfere with blood compatibility testing and thereby complicate the safe release of blood products. Neutralization of the therapeutic CD38 antibody or CD38 denaturation on reagent red blood cells mitigates daratumumab interference with transfusion laboratory serologic tests. Finally, therapeutic antibodies may complicate flow cytometric evaluation of normal and neoplastic plasma cells, since the therapeutic antibody can affect the availability of the epitope for binding of commercially available diagnostic antibodies.