Barnidge, David R.

Abstract Background Multiple myeloma (MM) evolves from monoclonal gammopathy of undetermined significance (MGUS), a clinically detectable but asymptomatic premalignant phase seen in ~3% of the general population 50 years of age or older. The prevalence of MGUS has not been described in a population at high risk of developing MM, specifically Black/African American (AA) individuals or first-degree relatives of patients with hematologic malignancies (HM). In 2019, we launched the first nationwide US screening study for individuals at high risk of MM to help better identify what population would benefit most from screening and early intervention for precursor MM stages. We aim to assess the prevalence of MGUS in a population at high risk of MM and characterize clinical variables of individuals who screen positive. Here, we report interim screening data on the first 2,960 participants. Methods Individuals aged 40 or older with an additional MM risk factor are eligible to be screened in the PROMISE Study. High-risk individuals include Black/AAs and those with a first-degree relative diagnosed with a hematologic malignancy or a precursor condition to MM. Blood from all participants was analyzed via serum protein electrophoresis, immunofixation, and Optilite® to measure the serum free light chains (sFLC), IgG, IgA and IgM. Results were returned to all participants, and those who tested positive for a monoclonal gammopathy (MGUS/SMM) were referred to a hematologist for clinical follow-up and invited to periodically complete epidemiologic exposure and psychosocial questionaries, including a 4-item cancer worry questionnaire and the RAND 36-item Short Form Survey (SF-36). To investigate the use of the higher-sensitivity matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) with the Optilite® IgG, IgA, IgM and sFLC results as a screening test for all participants, we rescreened 1,092 samples from PROMISE. The Binding Site Group proprietary software was used for the analysis of the combined MS/Optilite® results, allowing for the detection and quantification of M-protein. Heavy-Chain MGUS (HC-MGUS) was defined by the presence of one or more paired heavy and light chain monoclonal peaks detected by MS. Pairing was based on mass to charge ratio of identified peaks. To enrich the PROMISE cohort with Black/AA individuals, we identified and screened 1,868 Black/AA additional individuals from the Mass General Brigham (MGB) Biobank who met the PROMISE enrollment criteria. Screening was performed by MS/Optilite®, and results have not been returned to participants. Results We screened 2,960 participants with the combined MS/Optilite® approach. We report here the prevalence of HC-MGUS and plan on presenting the estimated rate of light chain MGUS in our cohort, at the meeting. We detected HC-MGUS in 9.6% (95% CI: 8.6-11%) of our cohort, with a prevalence of 10% (95% CI: 8.3-12%) in the PROMISE cohort and 9.4% (95% CI: 8.1-11%) in the MGB cohort (Table 1 and Figure 1). HC-MGUS prevalence increased with age in high-risk individuals from 4.9% (CI: 3.3-6.9%) for participants aged 40-49 to 13% (CI: 10-17%) in the 70-79 range (P < 1.2E-5). Among monoclonal HC-MGUS, we found 65% IgG, 18% IgM, and 18% IgA. M-spike was quantified in 97% of samples. Median M-spike concentration was, 0.058g/dL (max. 2.6g/dL) for IgG, 0.0043g/dL (max. 0.6g/dL) for IgM, and 0.067g/dL (max. 0.8g/dL) for IgA. In the Promise cohort, no significant change in cancer worry was observed across the pre- and post-screening interval among participants who screened positive (P = 0.52). Health-related quality of life, as measured by the SF-36, was not significantly different in screen-positive vs. screen-negative individuals for any of the eight subscales (all P > 0.20). Conclusions We present the largest dataset on monoclonal gammopathy prevalence and screening in individuals at high risk for MM, and more specifically the largest cohort of Black/AA, using a novel high-sensitivity testing approach. Our results confirm that older adults who are Black/AA or have a first-degree relative with an HM have a high prevalence MGUS and may benefit from precision screening approaches to allow for early detection and clinical intervention. Preliminary data on cancer worry and quality of life indicates that the psychosocial burden of screening in this population is likely minimal. Figure 1 Figure 1. Disclosures Sakrikar: The Binding Site: Current Employment. Krause: The Binding Site: Current Employment. Barnidge: The Binding Site: Current Employment. Bustoros: Takeda: Consultancy, Honoraria; Janssen, Bristol Myers Squibb: Honoraria, Speakers Bureau. Perkins: The Binding Site: Current Employment. Harding: The Binding Site: Current Employment, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Kapoor: Ichnos Sciences: Research Funding; Amgen: Research Funding; Pharmacyclics: Consultancy; Takeda: Research Funding; Sanofi: Consultancy; Regeneron Pharmaceuticals: Research Funding; AbbVie: Research Funding; BeiGene: Consultancy; Sanofi: Research Funding; Karyopharm: Research Funding; Glaxo SmithKline: Research Funding; Karyopharm: Consultancy; Cellectar: Consultancy. Mo: Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Epizyme: Consultancy; Eli Lilly: Consultancy; Janssen: Honoraria; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees. Murray: The Binding Site: Patents & Royalties: Potential Royalties for use of mass spectrometry in M-protein detection. Getz: Scorpion Therapeutics: Consultancy, Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; IBM, Pharmacyclics: Research Funding. Marinac: JBF Legal: Consultancy; GRAIL Inc: Research Funding. Ghobrial: AbbVie, Adaptive, Aptitude Health, BMS, Cellectar, Curio Science, Genetch, Janssen, Janssen Central American and Caribbean, Karyopharm, Medscape, Oncopeptides, Sanofi, Takeda, The Binding Site, GNS, GSK: Consultancy.

Abstract Objectives Multiple myeloma (MM) is a malignant plasma cell neoplasm, requiring the integration of clinical examination, laboratory and radiological investigations for diagnosis. Detection and isotypic identification of the monoclonal protein(s) and measurement of other relevant biomarkers in serum and urine are pivotal analyses. However, occasionally this approach fails to characterize complex protein signatures. Here we describe the development and application of next generation mass spectrometry (MS) techniques, and a novel adaptation of immunofixation, to interrogate non-canonical monoclonal immunoproteins. Methods Immunoprecipitation immunofixation (IP-IFE) was performed on a Sebia Hydrasys Scan2. Middle-down de novo sequencing and native MS were performed with multiple instruments (21T FT-ICR, Q Exactive HF, Orbitrap Fusion Lumos, and Orbitrap Eclipse). Post-acquisition data analysis was performed using Xcalibur Qual Browser, ProSight Lite, and TDValidator. Results We adapted a novel variation of immunofixation electrophoresis (IFE) with an antibody-specific immunosubtraction step, providing insight into the clonal signature of gamma-zone monoclonal immunoglobulin (M-protein) species. We developed and applied advanced mass spectrometric techniques such as middle-down de novo sequencing to attain in-depth characterization of the primary sequence of an M-protein. Quaternary structures of M-proteins were elucidated by native MS, revealing a previously unprecedented non-covalently associated hetero-tetrameric immunoglobulin. Conclusions Next generation proteomic solutions offer great potential for characterizing complex protein structures and may eventually replace current electrophoretic approaches for the identification and quantification of M-proteins. They can also contribute to greater understanding of MM pathogenesis, enabling classification of patients into new subtypes, improved risk stratification and the potential to inform decisions on future personalized treatment modalities.

Abstract The IgVH mutation status is an independent predictor of time to treatment and survival in CLL. However, the biological basis of this difference is unknown. Clinical use of the IgVH mutation status as a prognostic marker is limited due to the technical difficulties of assessing this feature. As such, we probed for differences in protein expression by CLL cells with unmutated (UM) vs mutated (M) IgVH using phage peptide display libraries (PDPL). Methods: PDPL consists of phages engineered to express random peptides (7-mer) on the coat protein. From approximately 2x1011 phages displaying all possible permutations of 7-mer peptide, we selected phages binding to UM cells by incubation with 106 UM cells and elution of bound phages. Then, from numerous phages initially binding to UM cells, we subtracted phages binding to M cells by multiple incubations with M cells (106). Thus, the phages that bound only to UM cells were selected. The procedure was repeated multiple times to increase selection specificity. The peptide sequences displayed by selected phages were evaluated. We identified phage targets on UM cells by immunoprecipitation (IP) of CLL protein with specific phage and by sequencing of precipitated protein. The expression of target protein in CLL cells was confirmed by immunobloting and flow cytometry. Results: Sequencing of phages from the 3rd round of selection (UM v. M) revealed several peptides, with the most predominant being FPSAHFL. IP identified the cellular target for FPSAHFL as vimentin, an intermediate filament protein involved in cell motility and activation. The level of vimentin expressed by CLL cells varied between patient samples (n=15). UM CLL cases were found to express higher levels of vimentin (the mean MFI was 1002; SD 381), than cases of M CLL (mean MFI 547; SD 109), p=0.0128. To evaluate the prognostic significance of vimentin, we assessed vimentin expression by flow cytometry in a separate subgroup of 40 CLL patients. Archived cell samples collected between 6/2000 – 6/2001 were used. The median follow up was 81 months (40–233). Vimentin expression (MFI) as a continuous variable was a risk factor for a shortened time to treatment (TTT) with a proportional hazard ratio of 4.152 (95% CI 1.33–15.220, p=0.0317). Using MFI closest to the median (and rounded to 2 decimal places) as a cutoff, we stratified patients in high (n=21) and low (n=19) vimentin expression groups. The median times to treatment (TTT) in patients with high vs low level expression of vimentin were 2.8 and 12.9 years respectively, p=0.0025 (Fig.). Conclusion: Using novel proteomic technology, we found that CLL cells with unmutated IgVH expressed higher levels of vimentin than CLL cells with mutated IgVH. A high-level of vimentin expression defined by flow cytometry appears to be associated with high-risk disease. Validation of these findings could allow for the vimentin level to be used as a surrogate marker for expression of unmutated IgVH in CLL. Figure Figure

Abstract Detection of an M-protein (monoclonal immunoglobulin) has been used to diagnose and monitor multiple myeloma (MM). As therapies for MM have improved, more sensitive methods have been used to define response: immunofixation electrophoresis (IFX) of serum and urine, normalization of the serum immunoglobulin free light chain (FLC) ratio, and high sensitivity flow cytometry to detect clonal plasma bone marrow cells. It is hoped that these more sensitive approaches will differentiate those patients with minimal residual disease (MRD) versus no residual disease (NRD), that later which could mean a cure. Flow cytometry of plasma cells requires bone marrow aspiration, which is inconvenient and expensive and is potentially limited by sampling bias. More sensitive methods to differentiate MRD from NRD using serum would be advantageous. We have developed a sensitive test for the presence of the monoclonal antibody produced by the plasma cells which may serve as a substitute for invasive bone marrow biopsy. Briefly, patient serum is enriched for immunoglobulins (Ig) and the Ig light chains are decoupled from the heavy chain by reduction with DTT. The mass distribution of the light chains is resolved using a micro LC-ESI-Q-TOF mass spectrometry and the presence of the M-protein is detected as a spike in the mass distribution. In addition to the detection, the accurate mass measurement of the light chain serves as a unique individualized marker which can aid in detection in subsequent patient monitoring. We have termed this method: monoclonal-immunoglobulin-Rapid-Accurate-Mass-Measurement (miRAMM). By spiking monoclonal immunoglobulins into human serum, we have demonstrated that miRAMM is approximately 1000x more sensitive than SPEP at detecting M-proteins. Initial results on 21 patients in stringent complete response (sCR) demonstrated that 67% (n=14) had detectable malignant specific clones by miRAMM. Given these promising results we have extended the method to a larger series of myeloma patients for whom we had long term follow-up and serum samples prior to treatment and at 6-12 months status post stem cell treatment. The results of this data will be correlated to the clinical outcomes for these patients. Early results demonstrate the potential of miRAMM to be a more sensitive, cost effective approach to detect MRD compared with current methods. Disclosures Murray: Mayo Clinic: Patent Application filed Patents & Royalties. Barnidge:Mayo Clinic: Patent filed Patents & Royalties.

Abstract Proteomics with great sensitivity and specificity effectively analyzes proteins by prior tryptic digestion and subsequent analysis by LC-MS/MS of the tryptic digest. We have utilized this approach in the development of a LC-MS/MS method to characterize minimum residual disease in multiple myeloma. The abundant antibodies produced by multiple myeloma plasma cells are identical and appear as a spike (M-spike) upon protein electrophoresis. The M-spike and histological examination of the bone marrow constitute part of the myeloma diagnostic repertoire. Upon treatment, myeloma cells and the antibodies they produce are reduced in number and amount and become increasingly hard to detect. The bone marrow biopsy serves as the “gold standard” test for clinical remission. We have developed a sensitive test for the presence of the monoclonal antibody produced by the plasma cells which may serve as a substitute for invasive bone marrow biopsy. We have focused on tryptic peptides comprising the variable CDR regions of the Ig light chains that are unique to each patients antibody clone. Utilizing 2-5 µL of patient plasma/serum from the initial M-spike sample we have utilized SDS-PAGE to yield a crudely purified immunoglobulin light chain. The light chain band is isolated, reduced, alkylated and trypsin digested with subsequent LC-MS/MS analysis to identify CDR specific tryptic peptide(s). These can be identified as variable peaks (elution time and mass) in a base peak ion chromatogram where constant region peptides of either lambda or kappa light chains (clone dependent) serve as “internal standards” for identifying the CDR tryptic peptides. The peptide’s mass and its corresponding MS/MS spectra are unique to this CDR tryptic peptide and this patient’s clone. The unique diagnostic peptide is isolated in subsequent samples by immunoaffinity purification of the target kappa/lambda clone, SDS-PAGE separation and LC-MS/MS analysis of the light chain gel band. An extracted ion chromatogram is generated based upon the CDR peptides identified in the initial analysis of the M-spike sample. In patients in clinical remission the presence of a significant signal from the targeted peptides indicates that targeting a CDR peptide from the M-spike protein is more sensitive than currently available diagnostic tools including immunofixation. Comparison of this test to the gold standard bone marrow biopsy will be examined. Disclosures: Barnidge: Mayo Foundation: provisional patent application for technology, provisional patent application for technology Patents & Royalties.

Abstract Background: Current laboratory methods for detection of monoclonal gammopathies include a panel of serum protein electrophoresis (SPEP), immunofixation electrophoresis (IFE) and serum free light chain quantitation (FLC). Our group has recently described a new assay based on matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS) which is capable of detecting, isotyping and quantitating M-proteins in a single assay. The basic principle of the method involves leveraging the unique mass resulting from light chain (LC) Ig gene rearrangement in B-cells. In a similar fashion to SPEP, the mass distribution of LCs after dissociation from their heavy chains can be examined for the presence of an over expressed light chain. In this study we retrospectively compared the MALDI-TOF MS method to SPEP, IFE and Hevylite ratios for monitoring patients with monoclonal gammopathies. Methods: Serum from patients who had at least 1 diagnostic and 4 serial follow-up samples was enriched for IgG, IgA, IgM, kappa and lambda using nanobodies. After disassociating the heavy and light chains by reduction, the five purified samples were spotted onto a Bruker Microflex MALDI plate. Automated acquisition (~10 seconds/sample) was performed and the five LC mass spectra from each enrichment were overlaid. M-proteins were detected, quantitated and isotyped by the presence of distinct peaks (m-spike) within LC mass to charge regions. The serial patient samples were then measured by MALDI-TOF and a comparison of results was made to previous aquired data. The results were then analyze in light of clinical and lab data in order to evaluate the ability of the MALDI-TOF MS method to monitor patients with monoclonal gammopathies. Results: In M-protein positive patient samples, serial dilution revealed MALDI-TOF MS to have ~10-times lower limit of detection than IFE. M-protein isotype in the cohort by MALDI-TOF MS was 100 percent concordant with the isotype from IFE. The MALDI TOF M-protein quantitation was linear over a clinically acceptable range (0.1 to 6 g/dL) and had improved linearity over SPEP at lower M-protein levels. M-proteins quantitation by MALDI-TOF MS compared well with SPEP with a slope of 1.16 (R2 -0.93). Hevylite Ig ratios for each isotype were statistically similar to those from MALDI-TOF MS demonstrating the ability of the MALDI to measure isotype suppression. For some patients, the MALDI method was able to detect M-proteins in patients with normal Hevylite ratios. Finally, the results for each patient were then compared over the course of monitoring. The time evolution change in M-protein concentration was similar among the three methods with the exception of a few samples in which the MALDI-TOF detected residual M-proteins in treated patients not detected by the other methods. Conclusion: This preliminary study demonstrates that MALDI-TOF MS method can provide detection, quantitation and isotyping data suitable for monitoring patients. This is a significant finding since the MALDI-TOF method is amendable to automation, is rapid and in its current format is cost-competitive with current clinical assays. Disclosures Murray: Mayo Clinic: Patents & Royalties: Patent Application Filed. Mills:Mayo Clinci: Patents & Royalties: Patent Application Filed. Barnidge:Mayo Clinic: Patents & Royalties: Patent Application Filed.

Abstract Background: Immunoglobulin light chain (AL) amyloidosis is a fatal complication of B-cell clonal proliferation. Currently, the best biomarker for treatment monitoring is serum free light chain (FLC) assay. Despite its higher sensitivity, it cannot distinguish clonality thus ultralow levels of monoclonal gammopathy can be missed. Urinary exosomes (UExs) are the smallest members of the extracellular vesicle family that are excreted in the urine. They exhibit different characteristics in patients with AL amyloidosis vs multiple myeloma. This study was undertaken to determine if urinary exosomes have different characteristics in patients AL amyloidosis who progress despite being in complete response (CR) vs those who have a renal response. Methods: UEx were extracted from 4 patients at different stages of AL (Table 1). Immunoglobin light chains (LC) were identified in the UEx using western blotting. Intact immunoglobulin light chains were identified in plasma, UEx, and kidney biopsy amyloid deposits using mass spectrometry (MS). cDNAs from bone marrow plasma cells (BMPC) collected at the time of diagnosis from patient 4 were sequened. Results: Oligomeric LC (250 kd) were identified in the UEx of patient 1 (newly diagnosed, Fig 1a) and 4 (renal progression in CR, Fig 1d) but only monomeric LC (25 kd) were detected in patient 2 (Fig 1b) and 3 (CR and renal response, Fig 1c). MS of the UEx and plasma of patient 4 detected 2 monoclonal λ LC. The mass of one of the LC was consistent with a lambda 6a LC which is also the most common cDNA (IGLV-6-57) found in the BMPC. Amino acid sequences derived from the tryptic digestion of the amyloid deposits matched the predicted sequence of the cDNA. The calculated weight of the peptide produced by the cDNA (23,304 Da ) was within margin of error of the mass of the lambda 6a LC (23,306 Da). The mass of the second LC (23,092 Da) was consistent with a λ4/λ5 LCs. A search of the amino acid and cDNA sequences failed to identify any similarity. The density ratio of the oligomeric LC to monomeric LC in the UEx was 0.47 which was similar to the intensity ratio by MS of the lambda 6a LC (23,306 Da) to the 23,092 Da LC in the blood (0.43). Discussion: Urinary EXs identified oligomeric LC in a patient with progressive renal disease despite achieving a CR. The mass one of the λ LC matched the predicted peptide product of the cDNA obtained from BMPC. The amino acid sequence predicted by the cDNA matched the trypsin digested sequences from the amyloid deposits. This strongly suggests the oligomeric LC represents the amyloidogenic λ6a LC detected in the blood which was being produced by the BMPC clone which is being deposited as amyloid in the kidney. The origin of the second λ LC is unknown but is likely a new monoclonal gammopathy of undetermined significance that developed after the initial bone marrow biopsy. The blood and urine samples were obtained 3 years after the BMPC. The development of a new monoclonal gammopathy in patients with plasma cell dyscrasia is not uncommon. Unfortunately, bone marrow biopsy collected at the time of the urine and blood sample had insufficient number of plasma cells (CR) for analysis. Conclusion: UEx can identify amyloidogenic LC even when current standard methods could not. The persistent presence of the amyloidogenic LC helps explain why patients can progress despite being in CR. The presence of a second λ LC which was not part of the amyloid deposit also has clinical implication. It may explain why some patients do well despite having a persistent monoclonal protein. If these results are confirmed, UEx may have a powerful role in the determination of organ and hematologic response in patients with AL amyloidosis. Disclosures Dispenzieri: Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Membership on an entity's Board of Directors or advisory committees; Alnylam: Research Funding; GSK: Membership on an entity's Board of Directors or advisory committees; pfizer: Research Funding; Jannsen: Research Funding; Celgene: Research Funding.

e19534 Background: Our group has developed a mass spectrometry (MS) method that can identify circulating monoclonal proteins, based on their unique molecular mass signatures. Given the propensity for patients with AL amyloidosis to have MS patterns consistent with post-translational modifications (PTMs), we posed the question whether these changes might be present long before the diagnosis of AL and potentially serve as a predictor for AL in patients with an asymptomatic plasma cell dyscrasia (aPCD). Methods: We included 64 patients with AL who had a preceding aPCD and who had stored serum samples at both time-points. The mass/charge (m/z) of monoclonal LC peaks (P) was noted for each sample. Presence of a PTM was defined as the presence of ≥1 “heavy” Ps at a particular charge state. A P was considered heavy if its m/z exceeded the right sided 95% C.I. of the m/z distribution of the respective normal LC. We used 9 patients with relapsed multiple myeloma (MM) without AL as controls. Results: Prior aPCDs were MGUS (N = 33), smoldering myeloma (n = 9) and MM (N = 1). In 21 patients aPCD was not further classified with a bone marrow biopsy. The median interval between aPCD and AL diagnosis was 77 months. At aPCD diagnosis, 42 patients had a single, typical P and 21 patients (33%) had PTMS: 13 patients had a single heavy P; 5 patients had 2 P (only one of which was heavy); and 3 patients had 2 heavy peaks. No PTMs were noted in our MM controls. The m/z of all typical and heavy P observed at aPCD remained unchanged for 63 patients as they transitioned to AL, which suggests no new PTMs occurred with the exception of one patient, who had a single PTM at aPCD diagnosis, but developed 2 additional heavy P appearing at +1232 and +1392 Dalton at AL diagnosis, suggestive of new PTMs. In all but 3 aPCD, the typical P was more abundant relative to heavy P. Heavy P abundance increased in 6 patients as they transitioned from the aPCD to the AL state and exceeded that of the typical P in 3 patients, suggestive of increasing abundance of existing PTMs in these cases. Conclusions: Pre-existing PTMs are present in 1/3 of AL patients and not in MM and can be used to identify patients at risk for AL. New PTMs are uncommon, but the relative abundance can change over time.