Kappa Myeloma Research Articles

Joint AI-driven event prediction and longitudinal modeling in newly diagnosed and relapsed multiple myeloma

Multiple myeloma management requires a balance between maximizing survival, minimizing adverse events to therapy, and monitoring disease progression. While previous work has proposed data-driven models for individual tasks, these approaches fail to provide a holistic view of a patient’s disease state, limiting their utility to assist physician decision-making. To address this limitation, we developed a transformer-based machine learning model that jointly (1) predicts progression-free survival (PFS), overall survival (OS), and adverse events (AE), (2) forecasts key disease biomarkers, and (3) assesses the effect of different treatment strategies, e.g., ixazomib, lenalidomide, dexamethasone (IRd) vs lenalidomide, dexamethasone (Rd). Using TOURMALINE trial data, we trained and internally validated our model on newly diagnosed myeloma patients (N = 703) and externally validated it on relapsed and refractory myeloma patients (N = 720). Our model achieved superior performance to a risk model based on the multiple myeloma international staging system (ISS) (p < 0.001, Bonferroni corrected) and comparable performance to survival models trained separately on each task, but unable to forecast biomarkers. Our approach outperformed state-of-the-art deep learning models, tailored towards forecasting, on predicting key disease biomarkers (p < 0.001, Bonferroni corrected). Finally, leveraging our model’s capacity to estimate individual-level treatment effects, we found that patients with IgA kappa myeloma appear to benefit the most from IRd. Our study suggests that a holistic assessment of a patient’s myeloma course is possible, potentially serving as the foundation for a personalized decision support system.

Multiple Myeloma in a 27-Year-Old Female Presenting with Recurrent Low Back Pain

Multiple Myeloma or Kahler's disease is a neoplasm characterized by proliferation of plasma cells in bone marrow where the most common clinical manifestations include bone pain secondary to osteolysis, kidney damage and hypercalcemia. The most common risk factors associated with this pathology are advanced age, family history of multiple myeloma, alcoholism, smoking, among others. Diagnosis includes the presence of monoclonal protein or paraprotein in serum and urine by electrophoresis, presence of free chain protein in 24-hour urine and immunofixation in serum. We present a clinical case of a 27-year-old female patient who presented lumbar pain as the initial manifestation and on requesting laboratory tests showed alterations compatible with myeloma. Laboratory studies were requested confirming the diagnosis of Multiple Myeloma kappa stage ISS-III in current treatment with cyclophosphamide, dexamethasone and thalidomide.

P-015 A Novel CAR-T cell therapy targeting kappa myeloma antigen for the treatment of multiple myeloma

P-015 A Novel CAR-T cell therapy targeting kappa myeloma antigen for the treatment of multiple myeloma

A sequential cohort study evaluating single-agent KappaMab and KappaMab combined with lenalidomide and low-dose dexamethasone in relapsed and/or refractory kappa light chain-restricted multiple myeloma (AMaRC 01-16).

KappaMab (KM; formerly MDX-1097) is a monoclonal antibody specific for the kappa myeloma antigen (KMA), a cell-surface antigen expressed on malignant plasma cells in kappa-restricted multiple myeloma (κMM), some lymphomas, occasional tonsillar B cells and in vitro activated B cells, but not on normal B cells in bone marrow. Phase I/IIa studies of single-agent KM confirmed a favourable toxicity profile and evidence of anti-myeloma activity. Ex-vivo studies demonstrating upregulation of KMA by lenalidomide, and enhanced effector-cell cytotoxicity provided the rationale for this phase IIb study where KM or KM in combination with lenalidomide and dexamethasone (KM-Rd) was administered in relapsed, refractory κMM patients. In addition, outcomes for a real-world matched case-control cohort from the Australian and New Zealand Myeloma and Related Diseases Registry (MRDR) who received Rd were compared to the KM-Rd cohort. KM-Rd demonstrated an overall response rate of 82.5% which compared favourably to the Rd-MRDR cohort of 45.1%. Both single-agent KM and KM-Rd regimens were well tolerated, with the KM-Rd safety profile similar to patients given only Rd in other clinical settings. Based on the excellent safety profile and significant efficacy, further clinical trials escalating the KM dose and pairing KM with other standard-of-care treatments are planned.

BI11 Cutaneous presentation of Kaposi sarcoma following allogeneic haematopoietic stem cell transplantation for myeloma

Abstract Iatrogenic Kaposi sarcoma (KS) is a relatively frequent occurrence following solid-organ transplants (0–5%), in part due to prolonged immunosuppression. However, its occurrence after haematopoietic stem cell transplantation (HSCT) is rare, with only 15 cases described in the literature. We report a case of KS presenting in the skin of a patient who had received a matched unrelated donor allogeneic HSCT for IgG kappa myeloma. A 55-year-old HIV-negative white man with myeloma underwent an allogeneic HSCT from a matched, unrelated donor following conditioning chemotherapy with fludarabine–melphalan and antithymocyte globulin. Post-transplant, he was maintained on ciclosporin as graft-versus-host disease (GVHD) prophylaxis. On day 14 post-transplant, he developed a widespread eczematous eruption that rapidly evolved into an erythroderma; a skin biopsy was consistent with acute GVHD. He was managed with superpotent topical steroids and a 5-day course of oral prednisolone. He began extracorporeal photopheresis (ECP) on day 33 post-transplant, having failed to respond adequately to systemic steroids. He also completed four cycles of rituximab. Ciclosporin was stopped by day 130 post-transplant. He had completed 14 cycles of ECP by day 139 post-transplant, with resolution of cutaneous GVHD; however, he had developed a rapidly growing solitary dusky-red nodule on his right neck that was excised due to diagnostic uncertainty. Histology revealed a dermal haemorrhagic exophytic vascular tumour composed of lobules and sheets of epithelioid cells with an eosinophilic cytoplasm and pleomorphic nuclei. Immunoperoxidase staining was negative for S100, MNF-116 and AE1/AE3. The same cells were strongly and diffusely positive for the vascular markers CD31, CD34 and ERG. The lesional cells were positive for human herpesvirus (HHV)-8 confirming a diagnosis of Kaposi sarcoma. He subsequently developed a second lesion on his left forearm, despite being off all immunosuppression. A repeat bone biopsy confirmed that he remains in morphological remission from his myeloma. Positron emission tomography–computed tomography has not identified extracutaneous disease. KS following HSCT is rare, but it can be fatal. Skin lesions are the dominant clinical presentation. HHV-8 has an important role in the pathogenesis, and transplant-related KS may occur secondary to reactivation of the virus as a result of significant immunosuppression following HSCT. However, it could also occur as primary infection or be transmitted with donor cells. The outcome of KS after HSCT is variable. A watch and wait strategy can be applied if immune recovery is expected. In our patient, it developed 5 months after HSCT; shortly after immunosuppression had been tapered, he remains well and will be closely monitored for further suspicious lesions.

KAPPA MYELOMA ANTIGEN (KMA) AND LAMBDA MYELOMA ANTIGEN (LMA) ARE EXPRESSED ON B CELL MALIGNANCIES AND ARE PROMISING NOVEL TARGETS ON MALIGNANT PLASMA CELLS

Introduction: The kappa myeloma antigen (KMA) and the lambda myeloma antigen (LMA) are found on the surface of malignant plasma cells (PCs) in multiple myeloma (MM), other plasma cell dyscrasia patient bone marrow (BM) samples, human myeloma cell lines and in patient BM samples from plasmacytomas, lymphoplasmacytoid and B cell lymphoproliferative disorders (BLPD). KMA and LMA are not present on normal B cells in BM but are found on occasional mononuclear cells in tonsillar tissue and secondary mucosal lymphoid tissue. KappaMab is a therapeutic antibody that specifically targets KMA and a phase IIb study in combination with lenalidomide and dexamethasone has recently been completed. In early clinical trials, KappaMab was shown to have an excellent safety profile, with low-grade infusion-related reactions and no haematological toxicities. Two human therapeutic LambdaMabs (10B3 and 7F11) bind specifically to LMA expressed only on malignant cells in lambda restricted B cell diseases. Here we compare the expression of KMA and LMA to that of BCMA in MGUS, newly diagnosed MM and relapsed, refractory (RRMM) myeloma BM samples. We describe the difference in phenotype between KMA and LMA expressing malignant PCs and their enrichment in RRMM compared to early disease stages. Methods: Patient BM samples (κ = 70 and λ = 40) were analysed using multiparametric FCM immunophenotyping with APC labelled LambdaMab (10B3) and KappaMab Fab’2 fragments, CD38, CD138, CD269 (BCMA), CD319 (SLAM F7), CD56 and CD45 monoclonal antibodies. PCs were identified by initial gating using CD38 and CD138. LMA and KMA expression was determined and compared with the other cell markers. Results: KMA was expressed on the majority of kappa restricted BM PCs from MGUS through to RRMM, on lymphoplasmacytoid cells in 2 out of 3 BM samples and in all 4 plasmacytoma BM samples. LMA was expressed on the surface of BM PCs in lambda restricted MGUS through to RRMM and in all 4 AL amyloidosis BM samples. KMA and LMA antigen densities were both higher than BCMA in the RRMM population: KMA mean 1899 (range 468–7943) versus BCMA mean 1426 (range 350-2630) and LMA mean 2439 (range 263–6664) versus BCMA mean 817 (range 537–1065) molecules of PE/cell. Conclusions: Although there are smaller numbers of samples from other B cell malignancies such as lymphoplasmacytoid, amyloidosis and BLPDs, we have demonstrated that KMA or LMA are expressed on malignant BM PCs. In the myeloma cases, the antigen density of both KMA and LMA was increased compared to BCMA on RRMM BM PCs, which suggests a clonal advantage of KMA and LMA expressing plasma cells that are resistant to standard of care treatments. These data suggest that KappaMab and LambdaMabs have therapeutic potential in RRMM where the combination of high antigen density and restriction of the target antigen to the malignant subpopulation of PCs may confer clinical benefit by retaining normal plasma cells following treatment. Keywords: Immunotherapy, Multiple Myeloma Conflicts of interests pertinent to the abstract D. Gottlieb Consultant or advisory role David sits on the Scientific Advisory Board for HaemaLogiX Ltd. R. Dunn Employment or leadership position: Employee at HaemaLogiX Ltd. Stock ownership: Yes

Abstract 4074: Cellular immunotherapy targeting kappa myeloma antigen for the treatment of multiple myeloma

Abstract Multiple myeloma (MM), the second most common blood cancer, is characterized by the accumulation of malignant plasma cells in the bone marrow. Chimeric Antigen Receptor (CAR)-T cell therapy has recently entered the standard of care for relapsed and refractory MM, following the recent FDA-approval of two CAR-T cell products, ide-cel® and cilta-cel®, which target the B cell maturation antigen (BCMA). However, despite impressive response rates, most patients relapse within 1-3 years. Kappa (κ) myeloma antigen (KMA) is a tumour specific membrane associated protein expressed on malignant plasma cells in patients with kappa light-chain restricted (κ-type) MM. KMA is absent on normal plasma cells and haematopoietic stem cells, making it an attractive and alternative target antigen for CAR-T cell therapy for MM. The monoclonal antibody, KappaMab (MDX-1097), binds to a conformational epitope on KMA, and has been assessed in phase I, IIa and IIb clinical trials in relapse refractory myeloma patients (1). Here, we have engineered a lentiviral vector encoding a second-generation CAR expressing a scFv from MDX-1097, fused to a 4-1BB co-stimulatory domain and CD3 zeta chain. We successfully generated human anti-KMA CAR-T cells with high and stable CAR expression and a predominately memory T cell phenotype. The CAR-T cells selectively killed KMA-expressing tumour lines, secreted interferon-gamma upon target recognition, and demonstrated potent anti-tumour activity in a xenograft model. Anti-KMA CAR-T cell therapy therefore represents a novel and potent treatment ready to enter a phase I clinical trial for patients with myeloma. (1) Spencer et al. Blood Cancer Journal (2019) 9:58 Citation Format: Jessica Li, Nicole Haynes, Katherine Cummins, Kavitha Gowrishankar, Kenneth Micklewaithe, Halley Hilton, Rosanne Dunn, Jane Oliaro, Simon Harrison. Cellular immunotherapy targeting kappa myeloma antigen for the treatment of multiple myeloma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4074.

Changes in immune cell populations following KappaMab, lenalidomide and low-dose dexamethasone treatment in multiple myeloma.

Lenalidomide (LEN) is used to treat multiple myeloma (MM) and shows in vitro synergy with KappaMab (KM), a chimeric antibody specific for Kappa Myeloma antigen, an antigen exclusively expressed on the surface of kappa-restricted MM cells. Lenalidomide, dexamethasone (DEX) and KM control MM via multiple immunomodulatory mechanisms; however, there are several additional effects of the drug combination on immune cells. Lenalidomide can increase T cell and NKT cell cytotoxicity and dendritic cell (DC) activation in vitro. We investigated the immune cell populations in bone marrow of patients treated with KM, LEN and low-dose DEX in kappa-restricted relapsed/refractory MM ex vivo and assessed association of those changes with patient outcome. A cohort (n = 40) of patients with kappa-restricted relapsed/refractory MM, treated with KM, LEN and low-dose DEX, was analysed using a mass cytometry panel that allowed identification of immune cell subsets. Clustering analyses were used to determine significant changes in immune cell populations at time periods after treatment. We found changes in five DC and 17 T-cell populations throughout treatment. We showed an increase in activated conventional DC populations, a decrease in immature/precursor DC populations, a decrease in activated CD4 T cells and an increase in effector-memory CD4 T cells and effector CD8 T cells, indicating an activated immune response. These data characterise the effects of LEN, DEX, and KM treatment on non-target immune cells in MM. Treatment may support destruction of MM cells by both direct action and indirect mechanisms via immune cells.

Novel Antigens LMA and Kma Are Expressed on Malignant Bone Marrow Plasma Cells from Patients with Relapsed Refractory Multiple Myeloma and Plasma Cell Dyscrasias

Introduction Previous studies have identified the lambda myeloma antigen (LMA) and kappa myeloma antigen (KMA) on the surface of malignant plasma cells in myeloma patient bone marrow samples, human myeloma cell lines and other plasma cell dyscrasias1-3. LMA and KMA are not present on normal B cells and are found on occasional mononuclear cells in tonsillar tissue and secondary mucosal lymphoid tissue. Targeting KMA and LMA through cellular and other immunological therapies has the potential advantage of leaving a population of normal plasma cells untouched and minimising the risk of serious post-treatment infection. Characteristics of the antibodies called KappaMab and LambdaMabs (10B3 and 7F11) that bind to specific conformational epitopes in the constant regions of these surface-bound light chains have been described in clinical trials and in vitro experiments1, 2, 4-6. Here, we present data on a larger series of patients with plasma cell dyscrasias, demonstrating the expression of LMA on plasma cells from patients in whom myeloma evolves from monoclonal gammopathy of unknown significance (MGUS). We also describe the difference in phenotype between LMA and KMA expressing malignant plasma cells and the frequent expression of KMA in relapsed refractory myeloma patient (RRMM) samples. Methods Patient BM samples (κ=49 and λ=31) were analysed using multiparametric FCM immunophenotyping with APC labelled LambdaMab (10B3) and KappaMab Fab'2 fragments, CD38, CD138, CD269 (BCMA), CD319 (SLAM F7), CD56 and CD45 monoclonal antibodies. Plasma cells were identified as previously described by initial gating using CD38 and CD138. LMA and KMA expression was determined and compared with the other cell markers. Results Nine of 12 (75%) newly diagnosed λ-type patients with MGUS or SMM expressed LMA on the surface of BM plasma cells. Longitudinal data from two patients was available. One patient showed LMA expression and antigen density increasing on the surface of bone marrow plasma cells during progression from MGUS (2020) to smoldering myeloma (SMM) (2022) (% of plasma cells positive for LMA rose from 61% to 92%, antigen density increased from 532 to 5164 molecules of PE/cell). In a second individual, LMA expression and antigen density increased on bone marrow plasma cells during progression from SMM (2020) to myeloma (2022) (% of plasma cells positive for LMA rose from 94% to 100%, antigen density increased from 3981 to 8941 molecules of PE/cell). KMA expression continued to be observed on plasma cells in 4 of 6 patients after autologous stem cell transplant. KMA was expressed in 86% of patients with ĸRRMM (n=14). LMA expression was observed in 2 of 4 patients with λRRMM. Both KMA and LMA antigen densities were higher than BCMA in the RRMM population (KMA mean 1802, range 468-7943 vs BCMA mean 1306, range 350-2630 molecules of PE/cell), (LMA mean 2439, range 263-6664 vs BCMA mean 817, range 537-1065 molecules of PE/cell). Conclusions In an enlarged cohort of patients with myeloma, we have confirmed that KMA and LMA are expressed at all stages of disease. Our data examining longitudinal expression in individual patients suggests that expression of LMA on BM plasma cells increases from MGUS to MM. The majority of patients with relapsed refractory kappa myeloma expressed KMA. Further data is required to confirm LMA expression in this population. The antigen density of both LMA and KMA is higher than BCMA on RRMM BM plasma cells. KMA and LMA expression is independent of serum Ig and FLC levels and % marrow plasma cells. These data show that KappaMab and LambdaMab have therapeutic potential in the treatment of myeloma patients, especially in the setting of relapsed refractory disease where the combination of high antigen density and restriction of the target antigen to the malignant subpopulation of plasma cells will confer valuable clinical benefit.

An Unusual Case of Floating Separator Gel

After prompt centrifugation of a serum separator tube, the technologist observed that the separator gel had migrated above the serum and was on the topmost layer. Investigation revealed that the patient was a 66-year-old male who had presented to the Emergency Department with fatigue, headache, weight loss, and chest and back pain with retinal hemorrhage and epistaxis. The clinical team was asked to draw a red top serum tube (no gel) and to add on immunoglobulins and viscosity testing (Table 1). ... Hyperproteinemia or radiocontrast dye can increase the density of serum thereby causing the separator gel in the serum separator tube to float above the serum (1). Clinical presentation, along with increased viscosity (>3 cP) and IgG concentrations (>10 000 mg/dL), suggested hyperviscosity syndrome (2–4). Hypergammaglobulinemia is the most common cause of hyperviscosity syndrome, a critical condition that requires therapeutic apheresis (5). The patient was later found to have an IgG kappa myeloma.

The potential role of mass spectrometry for the identification and monitoring of patients with plasma cell disorders: Where are we now and which questions remain unanswered?

Mass spectrometry (MS) techniques provide a highly sensitive methodology for the assessment and monitoring of paraproteins compared to standard electrophoretic techniques. The International Myeloma Working Group (IMWG) recently approved the use of intact light chain matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in lieu of immunofixation in the clinical assessment of patients and the assessment of patients enrolled on clinical trials. The increased sensitivity of these assays may help to detect and monitor monoclonal proteins (MP) in many patients with previously non-measurable disease, will reduce complete response (CR) rates and increase detection of low-level MP. The ability to track the unique mass or amino acid sequence of the MP also eliminates interference from therapeutic monoclonal antibodies (tmAbs) in most patients with IgG kappa myeloma. The intact light chain assays also provide structural information about the monoclonal light chain, including the presence of N-linked glycosylation, which has been shown to be commoner on amyloidogenic light chains and may have prognostic significance in monoclonal gammopathy of undetermined significance (MGUS). In this review, we discuss these issues alongside differences in the analytical and practical aspects related to the different MS assays under development and the challenges for MS.

Hypertensive uveitis in a patient with uveal plasmacytoma

A 63-year-old female with IgA kappa myeloma in remission on maintenance therapy with lenalidomide developed a left intraocular pressure of 30 mm Hg, anterior granulomatous uveitis, and an iridociliary amelanotic mass inferiorly (Fig. 1A, inset) that infiltrated the angle from 2–11 o'clock meridians (arrows). The patient previously had been unresponsive to maximum steroid and hypotensive eyedrops. Systemic work-up was negative for infection, inflammation, and myeloma activity. Intralesional aspiration biopsy with immunohistochemistry confirmed plasmacytoma (Fig.

A Novel B Cell Antigen Designated Lambda Myeloma Antigen (LMA) Has Been Identified Using Two Fully Human Monoclonal Antibodies (Mabs) That Bind to Similar Epitopes on Plasma Cells from Patients with Plasma Cell Dyscrasias

Introduction:The novel kappa (κ) myeloma antigen (KMA) has been described and a specific monoclonal antibody KappaMab (formerly MDX-1097) developed which is currently in a Phase IIb clinical trial. In this study 2 human LambdaMabs (10B3 and 7F11) were shown to specifically bind to a conformational epitope in the lambda (λ) light chain constant region when it is held in non-covalent association with lipids in the cell membrane (LMA). The 10B3 Mab binds to all λ isotypes and 7F11 binds to isotypes 2 and 3; neither antibody binds κ light chain or immunoglobulin (Igλ or Igκ).Methods:To detect LMA on λ+ myeloma cell lines and on λ-restricted patient bone marrow (BM) samples, 7F11 and 10B3 Fab'2 fragments were conjugated to APC and R-PE and used to stain the λ myeloma cell lines LP-1, RPMI8226 and OPM-2 followed by flow cytometry analysis. KappaMab Fab'2 (KMA Fab'2) and the κ myeloma cell line JJN3 were used as a negative control and to identify KMA on κ-restricted patient BM samples.Patient BM samples (κ=43 and λ=22) included Monoclonal Gammopathy of Undetermined Significance (MGUS), untreated and treated multiple myeloma (MM) patients, AL amyloidosis, plasmacytoma and Waldenstroms macroglobulinemia (WM). Multiparametric FCM immunophenotyping was performed with the 10B3 Fab'2 fragments and CD38, CD138, CD269 (BCMA), CD319 (SLAM F7), CD56 and CD45 Mabs. Plasma cells (PCs) were identified by the co-expression of CD38 and CD138, then CD138+/CD38+ gated cells were analyzed for 10B3 or KMA, CD269, CD319, and CD56. KMA and LMA Fab'2 fragments were used as negative controls for each other. The antigen density of KMA or LMA versus BCMA on PCs in 55 samples was assessed using Quantibrite beads.Immunohistochemistry (ICH) tissue cross-reactivity studies using validated automated methods on tissue with whole antibody 7F11-biotin and 10B3-FITC were performed on MM cell lines, λ myeloma lung tissue (plasmacytoma) and a panel of 38 normal human tissues. Serial sections from snap frozen blocks were used to retain the conformational epitope and then stained with the λ Mabs and visualised by light microscopy.Results:The conjugated 10B3 Fab'2 fragment bound to LMA-expressing cell lines LP-1, RPMI8226 and OPM-2 (isotypes 1-3) and 7F11 bound to RPMI8226 and OPM-2, (isotypes 2-3); neither bound JJN3. KMA Fab'2 did not bind to λ myeloma cell lines but bound JJN3.Expression profiles for patient BM samples (Table 1) showed KMA was expressed on PCs from untreated (N=9/17; 53%) and treated (N=8/11; 73%) MM samples, whereas BCMA expression was 88% (N=15/17) and 82% (N=9/11) respectively. BM PCs from all 3 plasmacytoma cases and 1 WM case were positive for both KMA and BCMA. BM PCs from MGUS cases were all positive for BCMA and positive for KMA in half the cases studied. The expression of KMA and CD56 was highest on PCs from treated MM patient samples. Antigen density for KMA and BCMA was similar in the untreated patients. In treated patients KMA density was higher than BCMA, other samples had lower antigen density of both KMA and BCMA.LMA (Table 2) and BCMA were expressed on 50% and 90% of untreated MM samples and all LMA+ samples co-expressed BCMA but only 1 co-expressed CD56. All treated λMM samples expressed BCMA and 60% expressed LMA. LMA was positive on PCs from the 3 amyloidosis samples, BCMA was expressed weakly in only 1 of these whereas CD56 was always co-expressed with LMA. MGUS and WM samples did not express LMA. Similar to KMA, the antigen density of LMA and BCMA was equivalent in untreated patients but in treated patients LMA density was higher than BCMA. All 3 amyloidosis samples were λ isotype.IHC results showed that 10B3 and 7F11 bound to myeloma cell lines and 10B3 bound to PCs in λ plasmacytoma sections. Both Mabs bound occasional PCs or dendritic cells in the GI tract mucosa, tonsil and various secondary lymphoid organs. No off-target binding of 10B3 and 7F11 was observed and both antibodies bound occasional PCs in secondary lymphoid tissue.Conclusion:These studies used mostly myeloma samples and a small number of other plasma cell dyscrasias. Nevertheless expression of KMA and LMA was identified on PCs across the spectrum of disease. Within the treated patient cohort the antigen density of KMA or LMA was higher than that of BCMA and implies there is an enrichment of these novel antigens in relapsed refractory myeloma. No off-target binding was observed in normal human tissues and binding was limited to occasional leukocytes in secondary lymphoid tissue. [Display omitted] DisclosuresHu: HaemaLogiX Pty Ltd: Current Employment. Dunn: HaemaLogiX Pty Ltd: Current Employment.

A hybridoma-derived monoclonal antibody with high homology to the aberrant myeloma light chain.

The identification of antibody variable regions in the heavy (VH) and light (VL) chains from hybridomas is necessary for the production of recombinant, sequence-defined monoclonal antibodies (mAbs) and antibody derivatives. This process has received renewed attention in light of recent reports of hybridomas having unintended specificities due to the production of non-antigen specific heavy and/or light chains for the intended antigen. Here we report a surprising finding and potential pitfall in variable domain sequencing of an anti-human CD63 hybridoma. We amplified multiple VL genes from the hybridoma cDNA, including the well-known aberrant Sp2/0 myeloma VK and a unique, full-length VL. After finding that the unique VL failed to yield a functional antibody, we discovered an additional full-length sequence with surprising similarity (~95% sequence identify) to the non-translated myeloma kappa chain but with a correction of its key frameshift mutation. Expression of the recombinant mAb confirmed that this highly homologous sequence is the antigen-specific light chain. Our results highlight the complexity of PCR-based cloning of antibody genes and strategies useful for identification of correct sequences.

Anaplastic Myeloma Arising from Myeloma: Successful Management of Two Diseases in an Individual

IntroductionMultiple myeloma is known to have progressive mutations that lead to a dominant aberrant plasma cell clone and a number of subclones. Mutations can lead to more aggressive forms of myeloma, but rarely does it transform into an immature variant such as anaplastic myeloma. This particular variant has a predisposition for extramedullary sites and is related to IgA plasma cell variants. Unlike standard myeloma that responds better to novel agents such as proteasome inhibitors and immunomodulators, this poorly differentiated cell is highly resistant to therapy and has very poor outcomes.In the following case report, we present a patient with IgA kappa anaplastic myeloma that evolved from multiple myeloma. We will demonstrate how a combination of novel agents in conjunction with conventional chemotherapy was a successful therapy for both plasma cell variants.Case ReportA 60 year-old man had a three month history of confusion, headaches, and leg weakness. He did not seek medical attention until he lost vision on his right eye. On exam, he had right ptosis with a dilated pupil fixed downward and laterally. MRI of the orbit showed a right orbital apex mass surrounding the optic nerve and diffuse leptomeningeal enhancement. A PET/CT, to better characterize the extent of disease showed right laryngeal, lung, and femoral hypermetabolic lesions in addition to the orbital mass. A biopsy of the laryngeal mass showed an IgG kappa anaplastic myeloma with Ki-67 of 70% and FISH positive for +12 and +14. Serology demonstrated an IgA M-spike of 1.56 with an abnormal serum free light chain ratio of 118.31. He underwent a bone marrow biopsy that showed 30% kappa-restricted plasma cells with 13q- and +11 by FISH and a lumbar puncture that demonstrated CNS involvement by CD38+ clonal plasma cells. He was classified as systemic stage I IgA kappa myeloma by R-ISS with localized anaplastic myeloma showing similar light chain restriction by immunohistochemistry.The patient received HD methotrexate 3 g IV with evidence of leptomeningeal response but evidence of sytemic progression on eye mass within a week despite of stable myeloma serology. He received 4 Gy as a single dose to the eye mas that shrunk the tumor. HyperCVAD with IT cytarabine alternating with MTX was started with a significant improvement in plasmacytomas by PET scan after 2 cycles of therapy. Flow cytometry from CNS became negative at that time but paraprotein remained unchanged.A bone marrow biopsy performed after the 4th cycle of chemotherapy showed 30% clonal plasma cells with stable M-spike at 1.45 and serum free light chain ratio of 79. Seeing that the CNS fluid was now negative and the orbital and leptomeningeal lesions had improved, therapy was changed to carfilzomib, pomalidomide, and dexamethasone but continued on IT chemotherapy alternating cytarabine and MTX. His M-spike resolved after 3 cycles of treatment. His immunofixation continued to detect IgA kappa clone and serum free light chain ratio dropped to 19.08.Follow upThe patient continues tolerating treatment with no evidence of systemic or CNS relapse disease. He remains on carfilzomib, pomalidomide, and dexamethasone as maintenance for systemic therapy combined with monthly IT chemotherapy. He developed one episode of confusion thought to be from white matter changes from IT chemotherapy but those symptoms have resolved.DiscussionThis unique scenario of a patient having both myeloma and anaplastic myeloma poses a challenge in management. While novel agents may be good to control the myeloma, more primitive forms of myeloma cells do not have the epitopes these agents bind to in order to cause cell destruction. Since anaplastic myeloma is more aggressive, targeting it with conventional chemotherapy that penetrated the CNS barrier seemed like a good initial treatment until CNS disease control was achieved, with focus on the more indolent myeloma afterwards with novel agents. Out of those, we included one known to have CNS penetration (pomalidomide). This approach was effective in this case and could be applied in future cases as clinical trials on such rare disease wouldn't be feasible.The similarities between the two plasma cell neoplasms shows the significant difference myeloma subclones can have. This proves the concept that myeloma does not behave as a single tumor, but more like clusters of different myeloma strains that can branch off the dominant clone and lead to relapse or refractory disease. DisclosuresRodriguez:Celgene: Other: advisory board, Speakers Bureau; Takeda: Speakers Bureau.

Rapid Removal of Myeloma Light Chains By Continuous Veno-Venous Hemofiltration in a Patient with Acute Cast Nephropathy As a Result of Lambda Light Chain Myeloma

Myeloma cast nephropathy or myeloma kidney (MK) is a complication observed in up to one third of patients with multiple myeloma (MM). MM patients who recover kidney function have longer remissions and increased overall survival. Previous attempts at light chain reduction with the use of plasma exchange in addition to chemotherapy have not consistently improved patient outcomes and remains an area of research. The inefficiency of plasma exchange is due to the high volume of distribution of light chains in the extravascular space which will repopulate the vascular space once the exchange procedure is complete.Continuous Veno-Venous Hemofiltration (CVVH) is a form of continuous hemodialysis (HD). The use of CVVH in addition to chemotherapy in MK is rational, as continuous filtration allows for ongoing equilibrium between the extravascular and intravascular compartments, thus reducing the total body MM protein load. The Purema 500 (NxStage Medical, Lawrence, MA) filter used for CVVH has an average pore size of 65 kDa, and albumin Sieving co-efficient of 0.05. The myeloma kappa light chain is approximately 25 kDa whereas the lambda light chain (LLC), circulating as a dimer, is approximately 45 kDa and the average IgG complex is approximately 150 kDa. These data suggest that CVVH filtration could reduce the light chain MM protein in patients with MK, but would likely be ineffective for IgG, IgA or IgM MM.This hypothesis was tested in a 60 year-old-man with known normal baseline kidney function and LLC MM, who developed MK in the perioperative period, of a hip stabilization procedure, at the time of MM recurrence. Biopsy showed the kidney failure was due to MK. The LLC concentration at the time of kidney failure was 3,750 mg/L. We employed CVVH, run 24 hours a day for 72 hours, with concurrent high dose intravenous dexamethasone 40mg days 1-4 and IV bortezomib 1.3mg/m2 days 1,4,8, 11.Serum protein electrophoresis (SPEP) obtained prior to CVVH showed a monoclonal spike of 6.7 g/L or 11.5% of the total protein (figure 1A). Protein electrophoresis (PEP) of the first bag of spent dialysate showed a restricted peak 1.1g/L or 2.1% of the total protein with a similar appearance to the monoclonal spike on the SPEP, demonstrating removal of the LLC by CVVH (figure 1B). 72 hours after the initiation of CVVH and chemotherapy, the LLC concentration decreased 77% from 3,750 to 850 mg/L (figure 1D), SPEP showed the monoclonal spike had decreased to 0.5 g/L or 1% of the total protein (figure 1C). The patient became dialysis independent three months following CVVH.Previous series have reported on 11 patients with acute MK, who have been treated with as specialized high cut-off hemodialysis (HCO-HD) filter, which has a pore size of 45 kDa, and concurrent chemotherapy. Seven of these patients (63%) became dialysis independent. These studies showed an overall reduction of serum light chain protein in their patients, but did not report if the light chains were present in the dialysate. The EUropean trial of free LIght chain removal by exTEnded haemodialysis in cast nephropathy (EuLITE) reported an improved rate of renal recovery 33% vs 43% with the use of HCO-HD versus standard HD.By way of comparison, CVVH, which is widely available in the United States, rapidly decreased the LLC myeloma protein. Our data supports the depletion of the LLC stores in the extravascular compartment as we did not see a rebound of LLC after stopping CVVH (figure 1D). As kappa light chains have a lower molecular weight than LLC, we would expect the same result with kappa light chain MM. Patients with IgG MK may also benefit from CVVH, as we saw proteins with a molecular weight higher than 65 kDa in the spent dialysate PEP, including proteins in the IgG range (figure 1C). CVVH filters lead to less protein wasting as compared to the HCO-HD filters which would negate the need for albumin replacement. The observed rapid rate of decline of the light chain concentration in this case supports the addition of CVVH to chemotherapy, as the clearance of the myeloma protein was more rapid than has been described in previous trials using bortezomib and dexamethasone alone. Randomized clinical trials would need to be conducted to know if this approach is superior to chemotherapy alone. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Clearing drug interferences in myeloma treatment using mass spectrometry

ObjectiveTo explore the possibility of using a combination of a rapid MALDI-TOF-MS method (Mass-Fix) in conjunction with higher resolution LC-ESI-QTOF-MS (miRAMM) measurements to discriminate the IgG kappa M-protein from daratumumab, elotuzumab and isatuximab in myeloma patients. Design & Methods86 patients with an IgG kappa M-protein were spiked with therapeutic levels of the drugs and examined by Mass-Fix and miRAMM to establish the percent of cases that could be resolved by each method. The method was then applied to 21 samples from patients receiving one of the drugs. ResultsMass-Fix was capable of resolving the t-mAb from M-protein for 87 percent of the spiked samples. For the cases unresolved by Mass-Fix, miRAMM was capable of resolving the remaining drug interferences. The 21 IgG kappa myeloma patients that were receiving the drugs were all resolved by Mass-Fix. ConclusionThis proposed algorithm allows use of a clinical available assay (Mass-Fix) while maximizing the number of cases that can accurately resolve the t-mAb from the M-protein.

A Sequential Cohort Study Comparing Kappamab Alone to Kappamab, Lenalidomide and Low Dose Dexamethasone in Kappa-Restricted Relapsed Refractory Multiple Myeloma (AMaRC 01-16)

A Sequential Cohort Study Comparing Kappamab Alone to Kappamab, Lenalidomide and Low Dose Dexamethasone in Kappa-Restricted Relapsed Refractory Multiple Myeloma (AMaRC 01-16)

PS1383 A SEQUENTIAL COHORT STUDY COMPARING KAPPAMAB ALONE TO KAPPAMAB, LENALIDOMIDE AND LOW DOSE DEXAMETHASONE IN KAPPA‐RESTRICTED RELAPSED REFRACTORY (RR) MULTIPLE MYELOMA (AMARC 01–16)

Background:KappaMab is a chimeric IgG1 monoclonal antibody specific for Kappa Myeloma antigen (KMA), a tumour specific cell antigen exclusively expressed on the surface of kappa restricted MM cells. Early safety and efficacy signals seen with single‐agent treatment in phase I/II studies in conjunction with observations that IMiD®‐treatment upregulates the KMA target and enhances effector cell cytotoxicity, provide rationale for this proof‐of principal immune‐oncology (IO) approach in a minimally pre‐treated MM population.Aims:To establish the clinical benefit rate (CBR) of KappaMab alone (Stage 1) and in combination with lenalidomide (LEN) and low dose dexamethasone (DEX) (Stage 2). Secondary aims: to determine the safety of KappaMab in combination with LEN and DEX, in particular, the incidence of immunological adverse events (AEs); and to evaluate the kinetics of response and loss of response (time to response [TTOR], time to disease progression [PFS], overall survival [OS]).Methods:Investigator initiated, phase IIb, multi‐centre, open label sequential cohort study comparing KappaMab alone to KappaMab in combination with LEN and DEX in RR MM (funded by the Victorian Cancer Agency, Australia). Key inclusion criteria were kappa‐restricted myeloma, 1–3 prior lines of therapy but no prior LEN. In Stage 1 (n = 30), patients received KappaMab (10 mg/kg IV infusion) weekly for 8/52 (induction), then every 4/52 (maintenance). [One cycle = 28d] For patients in Stage 2 (n = 30), KappaMab dosing was as per stage 1 with the addition of LEN (25 mg D1–21) and DEX 40 mg weekly. In cycle 1 of Stage 2, LEN and DEX commenced 1/52 prior to KappaMab. [Cycle 1 was of 35 days duration: LEN 25 mg D1–28 and DEX 40 mg weekly (D1, 8, 15, 22, 29)]. Treatment continued until toxicity/progression. This is a planned interim analysis of the primary endpoint (CBR).Results:40 patients have commenced therapy. Following review by the DMC, recruitment to Stage 1 was terminated early (n = 19). 21 of a planned 40 patients for Stage 2 have commenced treatment. Cut‐off date for analysis: 15/2/2019. 13 patients remain on study (Stage 1 = 1, Stage 2 = 12). 19 have progressed (Stage 1 = 14, Stage 2 = 5), 6 withdrew consent (3 each stage), 1 other and 4 patients have died (Stage 1 = 2, Stage 2 = 2).Observed CBR in Stage 1 was 5.3% (1/19, PR = 1) compared to 66.7% in stage 2 (14/21, VGPR = 2, PR = 11, MR = 1). (Response assessments are continuing and will be updated at the June meeting). Proof of concept (PoC) criteria were not met for Stage 1, but were met for Stage 2: observed CBR ≥ 55%, and the posterior probability (PP) that the true CBR exceeds 35% was &gt; 0.95 (PP = 0.998). ORR for Stage 1 was 5.3% (1/19) compared to 61.9% (13/21) for Stage 2. TTOR was not reached in Stage 1, and was 1.8m in Stage 2 (95% CI: 1.2 – 2.3m). Median PFS for stage 1 was 1.97m (95% CI: 1.67 ‐ 4.63m), compared to 8.2m for patients in Stage 2 (95% CI 3.9 – 8.2m) (p = 0.004). Median OS for stage 1 was 16.4m (95% CI 4m and above), median OS for Stage 2 not reached (p = 0.682).AEs of interest: 3/19 patients in Stage 1 had infusion reactions (grade 1 = 1, grade 2 = 2), compared to 4/21 patients in Stage 2 (grade 2 = 4). There were no haematologic toxicities reported in Stage 1, in comparison to anaemia 2/21, neutropenia 3/21 (grade 3 = 3), thrombocytopenia 4/21 (grade 3 = 1, grade 4 = 2) reported in Stage 2.Summary/Conclusion:PoC for efficacy was met for KappaMab when combined with LEN and DEX, and the combination is well tolerated. This novel IO combination may represent a promising new therapeutic option for MM patients. This study is ongoing.image

PS1384 TREATMENT CHOICES AND OUTCOMES FOR PATIENTS WITH MULTIPLE MYELOMA AFTER RELAPSE ON LENALIDOMIDE MAINTENANCE THERAPY: RESULTS FROM THE CONNECT® MM REGISTRY

Background: KappaMab is a chimeric IgG1 monoclonal antibody specific for Kappa Myeloma antigen (KMA), a tumour specific cell antigen exclusively expressed on the surface of kappa restricted MM cells. Early safety and efficacy signals seen with single-agent treatment in phase I/II studies in conjunction with observations that IMiD®-treatment upregulates the KMA target and enhances effector cell cytotoxicity, provide rationale for this proof-of principal immune-oncology (IO) approach in a minimally pre-treated MM population. Aims: To establish the clinical benefit rate (CBR) of KappaMab alone (Stage 1) and in combination with lenalidomide (LEN) and low dose dexamethasone (DEX) (Stage 2). Secondary aims: to determine the safety of KappaMab in combination with LEN and DEX, in particular, the incidence of immunological adverse events (AEs); and to evaluate the kinetics of response and loss of response (time to response [TTOR], time to disease progression [PFS], overall survival [OS]). Methods: Investigator initiated, phase IIb, multi-centre, open label sequential cohort study comparing KappaMab alone to KappaMab in combination with LEN and DEX in RR MM (funded by the Victorian Cancer Agency, Australia). Key inclusion criteria were kappa-restricted myeloma, 1–3 prior lines of therapy but no prior LEN. In Stage 1 (n = 30), patients received KappaMab (10 mg/kg IV infusion) weekly for 8/52 (induction), then every 4/52 (maintenance). [One cycle = 28d] For patients in Stage 2 (n = 30), KappaMab dosing was as per stage 1 with the addition of LEN (25 mg D1–21) and DEX 40 mg weekly. In cycle 1 of Stage 2, LEN and DEX commenced 1/52 prior to KappaMab. [Cycle 1 was of 35 days duration: LEN 25 mg D1–28 and DEX 40 mg weekly (D1, 8, 15, 22, 29)]. Treatment continued until toxicity/progression. This is a planned interim analysis of the primary endpoint (CBR). Results: 40 patients have commenced therapy. Following review by the DMC, recruitment to Stage 1 was terminated early (n = 19). 21 of a planned 40 patients for Stage 2 have commenced treatment. Cut-off date for analysis: 15/2/2019. 13 patients remain on study (Stage 1 = 1, Stage 2 = 12). 19 have progressed (Stage 1 = 14, Stage 2 = 5), 6 withdrew consent (3 each stage), 1 other and 4 patients have died (Stage 1 = 2, Stage 2 = 2). Observed CBR in Stage 1 was 5.3% (1/19, PR = 1) compared to 66.7% in stage 2 (14/21, VGPR = 2, PR = 11, MR = 1). (Response assessments are continuing and will be updated at the June meeting). Proof of concept (PoC) criteria were not met for Stage 1, but were met for Stage 2: observed CBR ≥ 55%, and the posterior probability (PP) that the true CBR exceeds 35% was > 0.95 (PP = 0.998). ORR for Stage 1 was 5.3% (1/19) compared to 61.9% (13/21) for Stage 2. TTOR was not reached in Stage 1, and was 1.8m in Stage 2 (95% CI: 1.2 – 2.3m). Median PFS for stage 1 was 1.97m (95% CI: 1.67 - 4.63m), compared to 8.2m for patients in Stage 2 (95% CI 3.9 – 8.2m) (p = 0.004). Median OS for stage 1 was 16.4m (95% CI 4m and above), median OS for Stage 2 not reached (p = 0.682). AEs of interest: 3/19 patients in Stage 1 had infusion reactions (grade 1 = 1, grade 2 = 2), compared to 4/21 patients in Stage 2 (grade 2 = 4). There were no haematologic toxicities reported in Stage 1, in comparison to anaemia 2/21, neutropenia 3/21 (grade 3 = 3), thrombocytopenia 4/21 (grade 3 = 1, grade 4 = 2) reported in Stage 2.Summary/Conclusion: PoC for efficacy was met for KappaMab when combined with LEN and DEX, and the combination is well tolerated. This novel IO combination may represent a promising new therapeutic option for MM patients. This study is ongoing.