Plasma Cell Leukemia Patients Research Articles

Secondary plasma cell leukaemia (PCL) with plasmablastic morphology.

A 71-year-old female with relapsed IgA lambda myeloma developed progressive cytopenia. The peripheral blood film showed 5% blastoid cells. Flow cytometry analysis was indicative of plasma cells. The bone marrow smear was packed with plasmablasts. Target CD138-cell FISH and molecular karyotyping identified a complex genome. NGS identified high-risk mutations. Bone marrow histology confirmed myeloma with no evidence of acute leukaemia. The patient was diagnosed with plasmablastic progression of myeloma and secondary PCL. Secondary PCL patients have a poor prognosis. It is essential to recognize this subtype and explore a novel treatment approach.

Distinct Genetic Features in Peripheral Blood Represent the Characteristics of Circulating Plasma Cells in Primary Plasma Cell Leukemia

Clonal plasma cells in peripheral blood (PB) are crucial for diagnosing plasma cell neoplasm. The diagnostic criteria for plasma cell leukemia (PCL) have recently been revised to 5% or more circulating plasma cells (CPCs) in PB. Considering that CPCs are an independent worse prognostic factor in multiple myeloma (MM), elucidating how many CPCs are sufficient for distinguishing patients between PCL and other plasma cell neoplasm is important yet uncertain. These CPCs have been recently discussed in MM, characterized by more immature phenotype, clonogenic potential, and high expression of cancer stem cell (CTC) markers. Though the exact mechanism of peripheral circulation still needs further studies, MM CTCs are considered subclones of bone marrow (BM) plasma cells. On the other hand, previous studies regarding PB plasma cells in primary PCL (pPCL) have been mainly focused on similar characteristics to BM plasma cells. Considering significant prognostic differences based on CPCs, PB from PCL patients should have distinct features. Previous studies on PCL revealed that high genetic heterogeneity and accumulation of diverse high-risk genetic abnormalities eventually led to the disease. Therefore, we aimed to investigate the genetic profile of CPCs in PCL to exhibit proper evidence for diagnostic criteria and improve the current practices. We retrospectively identified patients diagnosed with PCL from 2015 to 2017 at Seoul National University Hospital. Our study population included 4 pPCL and 2 secondary PCL (sPCL) patients. We retrospectively collected patients' clinical information and laboratory test results and performed targeted sequencing using the NGS panel of 647 genes related to hematologic malignancies. In all analyzed samples, 51 in PB and 40 variants in BM were detected in pPCL. The median number of variants in pPCL patients was 11 per patient (range 5-25) in PB and 10 per patient (range 3-17) in BM. When comparing variant allele frequency (VAF) between the paired samples, there was a moderate correlation (R=0.44, P<0.05). Similarly, a moderate correlation was observed in both pPCL (R=0.41, P<0.05) and sPCL (R=0.47, P<0.05) groups. When comparing paired variants between PB and BM, 38 were commonly detected in both samples in pPCL patients. Fifteen variants were identified in only one of the two samples, 12 in PB and 3 in BM. Most variants showed a heterogeneous distribution of genes. We checked the paired samples using an Integrative genomics viewer. As a result, twelve pPCL and thirteen sPCL variants were identified in the paired samples. These variants were initially excluded in the filtering process because of low VAF. Consequently, three unique variants were identified in each pPCL and sPCL group, which were considered truly unique. In pPCL patients, MED12, VPS13B variant from PB, and ZMYM3 variant from BM were identified in one of the paired samples. In sPCL patients, unique variants were identified in ARID1A, FANCE, and TP53. In addition, we determined that PB VAF is higher than BM VAF in shared variants of pPCL patients. Conversely, BM VAF tended to be higher than PB VAF in sPCL. However, plasma cell% was generally higher in BM than PB, regardless of pPCL or sPCL. Therefore, the differences in the percentage of plasma cells between PB and BM samples cannot explain the unique variants detected in only one of the paired samples. pPCL is an aggressive disease characterized by a markedly high diversity of heterogeneous mutation distribution and high mutational burden. The clinical outcomes of pPCL are still poor in the novel agent era. There is an urgent need to improve the current diagnosis and treatment strategy. As shown in this study, CPCs in pPCL are not simply part of the malignant plasma cells shed from the BM but have characteristics distinct from them. In this study, we exhibited that PB variants had higher VAF than BM variants, and some unique variants were identified only in the PB samples. Conversely, in sPCL, more diverse variants were detected mainly in BM samples, and VAF was also higher in BM than PB. Considering unique variants detected in PB and the high genetic heterogeneity of the disease, PB should be included in the diagnosis of PCL to determine the exact genetic profile.

GPER1 Activation Exerts Anti-Tumor Activity in Multiple Myeloma.

G protein-coupled estrogen receptor 1 (GPER1) activation is emerging as a promising therapeutic strategy against several cancer types. While GPER targeting has been widely studied in the context of solid tumors, its effect on hematological malignancies remains to be fully understood. Here, we show that GPER1 mRNA is down-regulated in plasma cells from overt multiple myeloma (MM) and plasma cell leukemia patients as compared to normal donors or pre-malignant conditions (monoclonal gammopathy of undetermined significance and smoldering MM); moreover, lower GPER1 expression associates with worse overall survival of MM patients. Using the clinically applicable GPER1-selective agonist G-1, we demonstrate that the pharmacological activation of GPER1 triggered in vitro anti-MM activity through apoptosis induction, also overcoming the protective effects exerted by bone marrow stromal cells. Noteworthy, G-1 treatment reduced in vivo MM growth in two distinct xenograft models, even bearing bortezomib-resistant MM cells. Mechanistically, G-1 upregulated the miR-29b oncosuppressive network, blunting an established miR-29b-Sp1 feedback loop operative in MM cells. Overall, this study highlights the druggability of GPER1 in MM, providing the first preclinical framework for further development of GPER1 agonists to treat this malignancy.

Plasma Cell Leukemia-Clinicopathological Profile from a Tertiary Care Center in Western India.

Poornima ManimaranIntroduction Plasma cell leukemia (PCL) is very uncommon and aggressive neoplasm constituting 2 to 4% of all plasma cell dyscrasias. By definition, clonal plasma cells should make up 20% of peripheral blood or have an absolute plasma cell count of 2 × 10 9 cells/cu.mm. PCL can be primary or secondary. In this study, the clinicohematological features of PCL, and correlation of immunophenotypic profile and conventional therapies with overall survival was analyzed. Materials and Methods This retrospective study involved PCL patients who were diagnosed across a 12-year period, from 2010 to 2021, at a tertiary care center in western India. Clinical, biochemical, peripheral smear, bone marrow aspirate, immunophenotyping, and molecular analysis were performed. Results Total 39 PCL patients were included in the study among which 36 were primary PCL patients. Splenomegaly (10/27), hepatomegaly (6/26), and lymphadenopathy (5/23) were noted. At presentation, all patients had anemia (<11g/dL), thrombocytopenia (33/39), hypercalcemia (>11mg/dl) 10/33 (30.3%) and lytic lesions was noted in 18/26 (69.2%). Immunophenotype of these patients showed CD 38 positivity, CD 138 positivity, CD56 positivity, and CD 117 negativity were 100, 62, 41.6, and 89%, respectively. Overall survival of our patients was 4.1 months and overall survival of patients treated with VTD (bortezomib, thalidomide, dexamethasone) and VCD (bortezomib, cyclophosphamide, dexamethasone) regimen was 3.4 and 4.1 months, respectively, which was not statically significant ( p -value 0.816). CD117 and CD56 markers were also not having any prognostic significance ( p -value 1.000 and 0.873, respectively). Conclusion Because of rarity of the disease, prospective studies are very limited and hence management and outcome of the disease are difficult to analyze. The current treatment protocols have no survival advantage and hence newer therapeutic approach is mandatory to attain better outcome.

Clinical Characteristics and Survival Analysis of Patients with Plasma Cell Leukemia

To investigate the clinical characteristics, therapeutic response and prognosis of patients with plasma cell leukemia (PCL) and improve the understanding of this disease. The clinical manifestations, laboratory tests and treatment response of 27 patients with plasma cell leukemia treated in The Second Hospital of Shanxi Medical University from December 2010 to August 2019 were analyzed retrospectively, and their clinical characteristics were summarized. Kaplan-Meier method was used for survival analysis. There were 18 cases of primary plasma cell leukemia (pPCL) and 9 cases of secondary plasma cell leukemia (sPCL). The male to female ratio was 1.7∶1. The median age was 62 years old. The first manifestations were bone pain, fatigue, fever, splenomegaly and bleeding, and a large number of plasma cell infiltration was observed in the morphological examination of peripheral blood and bone marrow cells. 13 cases were detected by immunotyping and all of them expressed CD38/CD138. 8 cases underwent karyotype analysis, and 3 cases were normal, clonal abnormalities occurred in 5 cases. FISH detection was performed in 12 cases, of which 8 cases were abnormal. In 17 cases of bortezomib based chemotherapy, the ovevall response rate was 52.9%, which was higher than that in the non-bortezomib group, but there was no significant difference between the two groups (P =0.242). The overall median survival time of 27 patients was 6.4 months, the median progression-free survival time was 3.5 months, and the median survival time of patients with pPCL and sPCL was 8.2 months and 2.4 months, respectively, the difference between the two groups was statistically significant (P =0.031). PCL is highly invasive and has diverse clinical manifestations, and is not sensitive to traditional chemotherapy. The median survival time of patients with pPCL is relatively longer than that of patients with sPCL. The chemotherapy regimen based on bortezomib improves the treatment effectiveness and prolongs the survival time of PCL patients.

Plasma cell leukemia: A multicenter retrospective study of 150 patients.

8014 Background: Despite the use of novel induction regimens, stem cell transplantation (SCT), and maintenance therapy, plasma cell leukemia (PCL) remains a challenging disease with a dismal prognosis. Currently, there is no agreed standard of care management for PCL. We conducted a multicenter retrospective analysis of the clinical presentation, treatment, and outcomes of 150 patients with PCL. Methods: Data of patients diagnosed with pPCL or sPCL between 01/2010 and 01/2021 were entered into a study-specific REDCap database from 7 different U.S. academic sites. PCL was defined as ≥ 5% circulating plasma cells. Clinical data included baseline patient characteristics, clinical presentation, treatment, therapeutic response, and survival outcomes. Overall survival (OS) curves were plotted using the Kaplan-Meier method. Cox proportional hazards regression tested associations between patient characteristics and OS, generating hazard ratios (HR) and 95% confidence intervals (CI), adjusted for PCL type (primary or secondary) and SCT. Results: The analytical cohort included 93 pPCL and 57 sPCL patients. Median age at diagnosis was 60 years. High-risk cytogenetics were found in 56.7% of the patients where it was documented. Of the 79 patients with a documented induction regimen, 58.2% received a proteasome inhibitor triplet, 22.8% received a VTD-Pace like conventional chemotherapy, and 3% received a daratumumab quadruplet regimen. SCT (autologous or allogeneic) was done in 56.1% of the patients. The median OS for all patients, those with pPCL, and those with sPCL was 20.3, 36.6, and 3.2 months, respectively. Secondary PCL was associated with worse survival outcomes compared with pPCL (HR, 2.46; 95% CI, 1.51-3.98; p&lt;0.001) (Table). Median OS was better in patients treated with a proteasome inhibitor triplet regimen vs VTD PACE-like combination (28.2 versus 12.6 months). OS was prolonged among patients who underwent any type of SCT compared with those who did not undergo SCT (44.0 versus 5.7 months, p&lt;0.001). Conclusions: This multicenter retrospective study is one of the largest PCL analyses performed to date and reveals the clinical practice patterns of treatment and survival of PCL patients across the U.S. in the novel treatment era. The survival analysis reinforces the poor prognosis in sPCL patients and the continued need for novel treatment approaches in this patient population. While limited by retrospective design, this analysis suggests prolonged survival with transplantation in both pPCL and sPCL. [Table: see text]

Meta-analysis of the Prognostic Value of microRNA-22 in Leukemia Patients.

Objective: The pathogenesis of leukemia is complex and there are no effective diagnostic and prognostic indicators. Previous studies showed that microRNA-22 (miR-22) has altered expression level in multiple leukemia subtypes, which is associated with the survival outcomes of leukemia. Methods: According to the constituted retrieval strategy, eligible studies were included from January 2010 to November 2022 by searching database. The pooled Risk Ratio (RR) and 95% confidence intervals (CI) were used to study the relationship between miR-22 and survival. Stata12.0 was used for meta-analysis. Differential expression analysis was conducted based on expression profile of miRNA. Results: Four English articles were included containing a total of 215 leukemia patients. Data showed that the pooled RR for overall survival (OS) was 1.558 (95% CI: 1.197-2.028, P < .01). Subgroup analysis for OS of acute myeloid leukemia patients and the RFS of plasma cell leukemia patients were statistically significant with different expression levels of miR-22 (RR:1.495, 95%CI:1.141-1.958, P < .01 and RR:1.517, 95%CI:1.114-2.065, P < .01, respectively). Moreover, all data included had no significant heterogeneity and publication bias. Conclusions: miR-22 is associated with the survival outcome of leukemia patients suggesting that miR-22 may be a promising prognostic biomarker for this patient population, and the expression level of miR-22 in ALL patients down-regulated.

Efficacy and Safety Analysis of VRD-PDCE in Treatment-Native Patients with Multiple Extramedullary Plasmacytomas or Plasma Cell Leukemia.

The prognosis of multiple extramedullary plasmacytomas (MEP) and plasma cell leukemia (PCL) is extremely poor, with the median overall survival (OS) of only 8months with standard chemotherapy. Innovative treatment approaches incorporating various strategies are required to improve outcome. From November 2019 to September 2021, a total of 12 newly diagnosed MEP or PCL patients were enrolled in our department. An intensive chemotherapy treatment as VRD-PDCE consisted of bortezomib, lenalidomide, dexamethasone plus cisplatin, pegylated liposomal doxorubicin, cyclophosphamide and etoposide was first proposed. Disease activity and toxicity were evaluated after each cycle. Of the patients receiving therapy achieved a rapid and sustained response, and the overall response rate (ORR) was up to 75%. Nine patients achieved partial response (PR) or better, the response was the best response and the median time to best response was 4 cycles. Median overall survival (OS) and progression-free survival (PFS) were 24 (5-30) months and 18 (2-23) months. The toxicities were acceptable and there was no treatment related mortality. Our intensive treatment showed encouraging results in terms of disease control and improving survival, VRD-PDCE may be a novel regimen which is feasible and generally well-tolerated in MEP or PCL patients.

ISB 2001, a First-in-Class Trispecific BCMA and CD38 T Cell Engager Designed to Overcome Mechanisms of Escape from Treatments for Multiple Myeloma By Targeting Two Antigens

In recent years, multiple myeloma (MM) patients have benefited from new treatments targeting MM associated antigens such as CD38 and BCMA. However, despite exceptional overall response rates observed using CAR T cell therapies or bispecific antibodies, durable responses beyond 2 years are still limited (PFS below 40% for treatment with idecabtagene vicleucel1 or teclistamab2). It has been proposed that one of the potential reasons for patient relapse may be downregulation of the target or expansion of clones lacking sufficient expression of targets3. This low expression of targets in the MM population has been observed after treatment with CD38-targeted daratumumab4, and BCMA specific CAR T cells5. Simultaneously targeting two antigens has been proposed as promising approach to prevent escape by antigen loss6. Here, we propose to simultaneously target BCMA and CD38 using ISB 2001, a first-in-class trispecific molecule based on the TREAT™ (Trispecific Engagement by Antibodies based on the TCR) technology. ISB 2001 targets CD3 on T cells and co-targets BCMA and CD38 on MM cells. ISB 2001 binding arms were derived from a synthetic phage display library with common light chain (Vκ3-15 + IgκJ1) and a silenced Fc (L234A, L235A, P329A mutations) to suppress FcγR-mediated interactions. In order to mimic antigen escape due to target downregulation post monotargeted therapies, ISB 2001 was evaluated in vitro comparing MM cell lines expressing either low levels of both CD38 and BCMA (KMS-12-BM), or high levels of CD38 and very low levels of BCMA (MOLP-8). Compared to monospecific T cell engagers, the binding of ISB 2001 to these cells was strongly increased due to avidity, while retaining reduced affinity to cells devoid of either CD38 or BCMA. ISB 2001 exhibited potent killing with EC50 ranging from 0.4 to 1.2 pM in different cell lines, which was 3 - 41-fold superior to that of EM801, a BCMA-targeted T cell engager7. The potency of ISB 2001 was superior to the combination of the CD38-specific and BCMA-specific T cell engagers constructed with the same binding domains, demonstrating the advantage of avidity augmentation when binding to CD38 and BCMA simultaneously. ISB 2001 was only modestly affected by soluble BCMA or APRIL when compared to EM801, demonstrating killing at 3 pM (EC50) in the presence of these soluble factors. Given the wide expression of CD38 on healthy immune cells, we evaluated whether the avidity induction enabled by the dual targeting could preferentially target MM cells while sparing normal immune cells. ISB 2001 induced low T cell activation and cytokine secretion in the absence of tumor cells, similar to EM801. This was in line with low binding to T cells (apparent cell-based affinity approx. 150 nM) and minimal binding to circulating CD38+ BCMA- healthy cells, indicative of low on-target off-tumour activity of ISB 2001. ISB 2001 showed potent anti-tumor activity in bone marrow aspirates of MM patients and in blood samples from plasma cell leukemia patients, indicating the ability of ISB 2001 to leverage its cytotoxic properties with available immune cells. The half-life of 7 days for ISB 2001 was determined in a preclinical study in human FcRn receptor-expressing TG32 mice. When evaluated in a therapeutic PBMC-humanized mouse model subcutaneously engrafted with KMS-12-BM cells, ISB 2001 was able to induce tumor regression at doses of 0.1 mg/kg. Even at doses as low as 0.02 mg/kg, ISB 2001 demonstrated significant growth inhibition. The in vivo efficacy was associated with T cell infiltration, T cell activation and cytokine release at the tumour site but not systemically. As reported here, ISB 2001 data support future clinical development as a potent treatment of MM through co-targeting CD38 and BCMA. Based on the specific dual targeting of MM cells, significant benefit is anticipated for relapsed/refractory patients who may experience tumor escape through target downregulation mechanisms. Preparations for the initiation of a Phase 1 clinical trial are ongoing. References Munshi, N. C. et al.384, 705-716 (2021).Moreau, P. et al. NEJMoa2203478 (2022) doi:10.1056/NEJMoa2203478.Rodríguez-Lobato, L. G., et al. Hemato2, 1-42 (2020).Nijhof, I. S. et al. Blood128, 12 (2016).Cohen, A. D. et al.J. Clin. Invest.129, 2210-2221 (2019).Fernández de Larrea, C. et al. D. Blood Cancer Discov.1, 146-154 (2020).Seckinger, A. et al.Cancer Cell31, 396-410 (2017).

Single Cell Gene Expression Predicts Plasma Cell Leukemia Patient Response to Daratumumab

The promise of precision medicine is to identify the ideal treatment for each patient, eliminating failed treatment cycles and reducing treatment burdens on patients and payors. While gene sequencing can predict effective treatment options in some cases, studies have estimated that only 10-15% of cancer patients are treated with genotype matched drugs. Gene expression is theoretically an attractive alternative to predicting therapeutic response because, it provides a direct readout of dysregulated cellular activities including druggable pathways. However, the use of bulk gene expression to predict therapeutic response is hampered by tumor heterogeneity; that is, a biopsied tumor contains multiple cells types and different tumor clones and a bulk analysis only generates an average gene expression signal across all of the cells, leading to a decreased sensitivity for identifying biomarkers found only in specific cell subgroups. More recently, single-cell gene expression analysis has shown promise in improving precision medicine through a focused look into the biology of the tumor cells themselves. For example, we previously showed (Scolnick, et al ASCO 2022) that a model trained on single-cell gene expression data collected from 17 Multiple Myeloma (MM) patient's plasma cells (PCs) could be used to predict the therapeutic response of seven independent MM patient samples at 100% accuracy. Here we combine single-cell gene expression analysis with Singleron Biotechnology's MapResponse™ machine learning algorithms to extend our predictions to data from peripheral blood mononuclear cells (PBMCs) of plasma cell leukemia patients who were treated with daratumumab. Our model accurately predicted the response to daratumumab treatment for both patients based on the PCs collected from blood samples. These early findings point to the potential value of combining single-cell RNA sequencing with machine learning methods such as MapResponse™ to bring precision medicine to more patients based on minimal invasive assessment of PBMCs.

Targeted Venetoclax Therapy in t(11;14) Multiple Myeloma: Real World Data From Seven Hungarian Centers.

Despite the introduction of novel agents, multiple myeloma remains incurable for most patients, necessitating further therapeutic options. Venetoclax, a selective BCL-2 inhibitor, had shown promising results in patients with translocation t(11;14), but questions remain open about its optimal use. We have contacted all Hungarian haematology centers for their experience treating t(11;14) myeloma patients with venetoclax. 58 patients were reported. 37 received venetoclax in the relapsed/refractory setting with few or no other therapeutic options available. 21 patients started venetoclax as salvage after failing to achieve satisfactory response to first line therapy. In the relapsed/refractory setting objective response rate (ORR) was 94%, median progression-free survival (PFS) 10.0 months and median overall survival (OS) 14.6 months. In reinduction patients, ORR was 100%, median PFS and OS were not reached. Importantly, we found no adverse effect of high risk features such as deletion 17p or renal failure, in fact renal failure ameliorated in 42% of the cases, including three patients who became dialysis independent. Our study also reports the highest number of plasma cell leukemia cases successfully treated with venetoclax published in literature, with refractory plasma cell leukemia patients achieving a median PFS of 10.0 and a median OS of 12.2 months.

LncRNAs LY86-AS1 and VIM-AS1 Distinguish Plasma Cell Leukemia Patients from Multiple Myeloma Patients.

Long non-coding RNAs (lncRNAs) are functional RNAs longer than 200 nucleotides. Due to modern genomic techniques, the involvement of lncRNAs in tumorigenesis has been revealed; however, information concerning lncRNA interplay in multiple myeloma (MM) and plasma cell leukemia (PCL) is virtually absent. Herein, we aimed to identify the lncRNAs involved in MM to PCL progression. We investigated representative datasets of MM and PCL patients using next-generation sequencing. In total, 13 deregulated lncRNAs (p < 0.00025) were identified; four of them were chosen for further validation in an independent set of MM and PCL patients by RT-qPCR. The obtained results proved the significant downregulation of lymphocyte antigen antisense RNA 1 (LY86-AS1) and VIM antisense RNA 1 (VIM-AS1) in PCL compared to MM. Importantly, these two lncRNAs could be involved in the progression of MM into PCL; thus, they could serve as promising novel biomarkers of MM progression.

CD44 Expression in Different Plasma Cell Diseases

CD44 expression in different plasma cell diseasesIntroductionMyeloma is a genetically complex disease which develops via a multistep process whereby plasma cells are driven towards malignancy through the accumulation of genetic “hits” over time. This multistep process permits myeloma to have four recognisable clinical stages including monoclonal gammopathy of undetermined significance (MGUS) , smouldering multiple myeloma (SMM) , multiple myeloma (MM) and plasma cell leukemia (PCL). CD44 as a complex adhesion molecule, is highly expressed in a variety of solid tumors and involved in metastasis and chemotherapy resistance . Previous studies had found that CD44 was also highly expressed in MM, and associated with advanced clinical stage, extramedullary myeloma (EM) and poor survival. However the relation of CD44 expression in different plasma cell disease remain unknown.Patients and MethodsNewly diagnosed MGUS (n=12), SMM (n=11), MM (n=133) and PCL (n = 8) patients who were hospitalized in our hospital from December 2017 to December 2020 were enrolled. The diagnosis was based on the criteria of the International Myeloma Working Group. CD44 was detected by flow cytometry as follows: 2 ml of heparin anticoagulated bone marrow was collected from the patients at the time of diagnosis, 1×10 6 cells were detected, and a gate was set for identifying abnormal plasma cells characterized by CD138 and CD38. CD44 positive was defined as more than 20% of the plasma cells expressed CD44.ResultsFrom December 2017 to December 2020, a total of 164 patients diagnosed in our hospital were included in the study, including 12 MGUS patients, 11 SMM patients, 133 MM patients and 8 PCL patients. The expression proportion (7.9%±11.9%, 11.2%±15.5%, 40.2%±37.7%, 81.9%±25.6%, P < 0.001) and expression intensity (the mean fluorescence intensity was 1 742.8±1 023.1, 2 915.7±923.0, 6 692.6±11 275.5, 25 359.6±22 604.5, P=0.001) of CD44 on the monoclonal plasma cells of MGUS, SMM, MM and PCL patients gradually increased. In 133 MM patients, 73 cases were for CD44 positive. CD44 positive patients were more likely to show ＞3 focal bone lesion (75.3% VS 50.0%, P=0.002), and international staging system（ISS）III stage (68.5% VS 51.7%, P=0.048) compared those with CD44 negative. CD44 expression rate was significantly higher in MM patients with extramedullary disease (n=26) than those without (n=107) (56.7%VS 36.2%, P=0.031)Conclusion: Our study showed that from MGUS, SMM, MM to PCL, the CD44 expression on abnormal plasma cells was gradually increased. CD44 overexpression was associated with osteolytic lesions, advanced ISS staging and extramedullary myeloma. The results indicated that CD44 was related to the invasion degree of plasma cell disease, and could be used as a marker for differential diagnosis between different plasma cell disease. DisclosuresNo relevant conflicts of interest to declare.

Venetoclax 400mg Combined with Bortezomib and Dexamethasone Is Efficacious and Feasible for Plasma Cell Dyscrasia

【Abstract】 Objective: To investigate the efficacy and safety of BCL-2 inhibitor Venetoclax (Ven) 400mg combined with bortezomib and dexamethasone in plasma cell dyscrasia with t(11,14). Methods: The data of twenty patients with plasma cell dyscrasia with t (11;14) were retrospectively analyzed.The majority of patients received Venetoclax 400mg combined with bortezomib and dexamethasone. The baseline clinical information, treatment efficacy and adverse effects after Ven-based regimen. Results: Seventeen multiple myeloma patients, two light-chain amyloidosis and one primary plasma cell leukemia (pPCL) patients were studied. Among seventeen MM patients, the median follow-up was 9.0 (0.5-27) months and the median treatment cycles was 4 (1-12);fourteen patients have been evaluated for response rate. The overall response rate for evaluable patients (ORR) was 85.7%, among that one patient (7.1%) achieved CR, four patients (28.6%) achieved VGPR and 7 (50%) achieved PR. The median progression-free survival (PFS) was11.0 months (95%CI 2.1-19.9); the median Overall survival (OS) was 14.0 months (95%CI 6.9-21.1). Two amyloidosis patients achieved VGPR and PR respectively, while one pPCL patient achieved CR. The most common grade 3 or worse treatment-emergent adverse events were thrombocytopenia (15%), infection (10%), neutropenia (5%), diarrhea (5%) and peripheral neuropathy (5%). There was no treatment-related death. Conclusion Ven (400mg) combined with bortezomib and dexamethasone is feasible, tolerated and efficacious in plasma cell dyscrasia.【Key words】Plasma cell dyscrasia; Venetoclax; Efficacy; Safety DisclosuresNo relevant conflicts of interest to declare.

High-Risk Gene Expression Subtype Provides Molecular Basis for Different Clinical Presentation of Primary and Secondary Plasma Cell Leukemia

Plasma cell leukemia (PCL) is rare but represents an aggressive, advanced form of multiple myeloma where neoplastic plasma cells (PCs) lose dependence on the bone marrow (BM) and circulate in the peripheral blood (PB). PCL is clinically defined by diagnosis of myeloma with ≥20% circulating plasma cells (CPCs), however, several groups have proposed a ≥5% CPC cutoff. PCL is classified as primary (pPCL) if it presents at myeloma diagnosis or secondary (sPCL) if it arises at a later progression event. These presentations of PCL are clinically distinct, with sPCL patients responding poorly to novel therapies and having inferior outcomes compared to pPCL patients. Despite recent advances in myeloma therapy, PCL prognosis remains poor, and the molecular drivers of PCL remain poorly understood.The MMRF CoMMpass study (NCT01454297) is a longitudinal, observational clinical study of 1171 newly-diagnosed myeloma patients. Tumors were characterized using whole genome (WGS), exome (WES), and RNA (RNAseq) sequencing at diagnosis and each progression event. PCs were isolated from BM-derived tumors and when >5% CPCs were detected, PCs were also isolated from the PB, creating a subcohort of patients with sequencing data from both the BM and PB compartments, with some patients assayed longitudinally.The percent CPCs determined using flow cytometry was reported for 982 patients at myeloma diagnosis and 194 patients at progression. Patients with 5-20% CPCs (median = 19 months) at diagnosis had poor overall survival (OS) outcomes compared to those with less than 5% CPCs (median = 95 months, p<0.001). No outcome difference was observed between patients with 5-20% and >20% CPCs (median = 41 months), confirming the findings of previous independent studies. A ≥5% CPC cutoff identified 947 myeloma, 29 pPCL, and 6 sPCL patients in the CoMMpass cohort. Compared to myeloma, pPCL and sPCL patients had poor OS (p<0.001), and after sPCL detection patients had a median OS of only 53 days (range = 0-169 days). For 10 pPCL patients, the percent CPCs was reported at diagnosis and at least one progression event, and patients with persistent CPCs (n = 5, median = 16 months, p<0.01) had poor OS compared to patients with no detectable CPCs at progression (n = 5, median not met, median follow up = 64 months). This underscores the benefit of early eradication of CPCs and repeated CPC measurements in pPCL.The proliferative (PR) gene expression subtype of myeloma has been previously described and defines a high-risk group of patients with diverse genetic backgrounds and inferior outcomes. For PCL patients, we determined the subtype of all BM and PB tumor samples characterized using RNAseq. There was high subtype concordance between paired BM and PB tumor samples (12/13, 92.3%). Overall, 6/23 (26.1%) pPCL patients were in the PR subtype, and PR pPCL patients had poor OS outcomes (median = 10 months, p<0.001) compared to non-PR pPCL patients (median = 55 months). PR emerged as a robust predictor of risk in pPCL, outperforming other molecular and clinical variables including high BM or PB PCs, plasmacytomas, renal failure, high LDH, high B2M, low platelets, t(11;14), del(1p), amp(1q), del(13q), and del(17p), suggesting that RNA subtyping CPCs may represent a non-invasive tool to predict risk in pPCL.At myeloma diagnosis, all sPCL patients with RNAseq data were classified in non-PR subtypes. However, at sPCL, 5/6 (83.3%) patients were in the PR subtype, indicating that sPCL is associated with transition to PR. Two sPCL patients that transitioned to PR acquired biallelic deletion of CDKN2C, and a third acquired biallelic deletion of RB1. Overall, a subset of pPCL (26.1%) but the majority of sPCL (83.3%) patients were in the PR subtype at PCL diagnosis, providing a molecular basis for the different clinical presentations observed between these two groups, including the highly-aggressive nature of sPCL. In summary, this study supports using a lower percent CPC cutoff to clinically define PCL and highlights the importance of repeated CPC measurements in prognosticating pPCL patients. Further, PR RNA subtype emerged as a predictor of risk in pPCL and, given that the majority of sPCL patients were in the PR subtype, provides a molecular basis for the different clinical features observed between pPCL and sPCL patients. DisclosuresMikhael: Amgen: Consultancy; Takeda: Consultancy; BMS: Consultancy; Janssen: Consultancy; Karyopharm: Consultancy; Sanofi: Consultancy; GSK: Consultancy; Oncopeptides: Consultancy.

P-077: Bone marrow microenvironment analysis of exosomal microRNAs in multiple myeloma, extramedullary disease and plasma cell leukemia

<h3>Background</h3> Multiple myeloma (MM) is a heterogeneous plasma cell (PC) malignancy. These malignant PC are dependent on the bone marrow (BM) microenvironment. However, a subclone of PCs can escape the BM microenvironment and infiltrate soft tissues and organs in the so-called extramedullary disease (EMD). This subclone may also escape to peripheral blood; if there are more than 20% of circulating PC (cPC), the disease is reclassified as plasma cell leukemia (PCL). All cells in the BM microenvironment release exosomes. Exosomes are small membranous vesicles that originate from internal multivesicular bodies; they are found in all body fluids, including peripheral blood, breast milk, etc. Exosomes are important in intercellular communication, and they have been implicated in disease relapse, resistance to chemotherapy and many other processes important for tumorigenesis. They contain proteins and nucleic acids, such as microRNAs (miRNAs) - short non-coding RNA molecules that are involved in many physiological and pathological processes. <h3>Aims</h3> The aim of this work was to analyze expression of exosomal miRNAs in BM plasma samples of MM, EMD and PCL patients. <h3>Methods</h3> Exosomes were isolated using qEV columns. MiRNAs were isolated from exosomes using qEV original Size Exclusion Columns, following miRNA isolation using miRNeasy Micro Kit. For next generation sequencing (NGS), 8 MM, 7 EMD and 8 PCL samples were used. Results from NGS were validated on 40 MM, 25 EMD and 21 PCL samples by RT-qPCR using Taqman Advanced MiRNA Assays. <h3>Results</h3> NGS analysis showed 1128 different miRNAs that were present in analyzed samples. Out of these, 239 miRNAs were found in at least 8 samples and had more than 1 read per million; thus, they were included in subsequent analysis. Out of these miRNAs, there are 6 miRNAs (p<0.05) that are significantly dysregulated between MM, EMD and PCL patients. Furthermore, 11 miRNAs (p<0.05) were significantly dysregulated between MM and EMD patients, 4 miRNAs (p<0.10) between MM and PCL patients and 7 miRNAs (p<0.05) between PCL and MM patients. We validated 6 miRNAs which were differentially expressed between MM, EMD and PCL. <h3>Conclusions</h3> Using NGS, we showed that they are differentially expressed exosomal miRNAs between MM, EMD and PCL patients suggesting their role in pathogenesis of these diseases. This work was supported by AZV 17-29343A and AZV 18-003-00203.

P-087: Real world efficacy and safety of venetoclax in t(11;14) multiple myeloma in Hungary

<h3>Background</h3> Despite therapeutic advances, multiple myeloma remains incurable. Venetoclax, a selective bcl-2 inhibitor may be a step toward personalised therapy for t(11;14) patients, but questions remain about its optimal use. <h3>Methods</h3> We retrospectively evaluated hematologic response, survival and safety after venetoclax treatment in t(11;14) myeloma patients in Hungary. <h3>Results</h3> Overall, 49 patients from seven clinical centers were reported. We divided patients into two groups based on the clinical setting: 32 relapsed/refractory patients, who received venetoclax after multiple lines of therapy, often in an ultimate effort; and 17 frontline patients, who achieved unsatisfactory response to standard first line therapy and were treated with venetoclax as reinduction before intended ASCT. We observed remarkably good hematological response rates (ORR): 94% in the relapsed/refractory group and 100% in the frontline setting. This translated into a median PFS of 9.6 months and a median OS of 14.6 months in the relapsed group; median PFS and OS were not reached in the reinduction group. Known adverse prognostic factors, such as 17p deletion, kidney failure or 1q21 amplification did not convey significantly worse prognosis in our study. Almost one third of patients had impaired kidney function during venetoclax therapy, including three patients requiring dialysis. Clinically relevant improvement was observed in 42% of these patients; dialysis could be stopped in all three cases. Notably, our study also included six plasma cell leukemia patients, with a remarkable median PFS of 10 months and over one year median OS in relapsed disease. Vulnerable patients with PCL, renal failure or refractory disease reported more adverse events, requiring supportive measures or dose adjustment, but cessation of venetoclax therapy did not become necessary. <h3>Conclusion</h3> Venetoclax therapy is a promising option with few side effects and very good response rates for t(11;14) patients, both in the frontline and in the relapsed setting

OAB-012: Depth of response and MRD in newly diagnosed ultra high-risk myeloma and plasma cell leukemia treated with Dara-CVRd and V-MEL ASCT: results of the molecularly stratified UK OPTIMUM/MUKnine trial

<h3>Background</h3> Outcome for patients with ultra high-risk (UHiR) newly diagnosed multiple myeloma (NDMM) or plasma cell leukemia (PCL) continues to be adverse, and UHiR patients are underrepresented in clinical trials. Recently, deepened responses have been reported for anti-CD38 monoclonal antibody combination therapy in NDMM. We report here protocol defined endpoints for the risk-stratified OPTIMUM/MUKnine (NCT03188172) trial for UHiR NDMM and PCL. Patients received daratumumab, cyclophosphamide, bortezomib, lenalidomide, dexamethasone (Dara-CVRd) induction and bortezomib-augmented HDMEL and ASCT. Early endpoints response and MRD from induction to day 100 post ASCT are reported. <h3>Methods</h3> Between Sep 2017 and Jul 2019, 472 patients with suspected NDMM from 39 UK hospitals were centrally molecularly screened. Of these, 107 patients were identified as having UHiR NDMM by trial genetic (≥2 high-risk lesions (double-hit): t(4;14), t(14;16), t(14;20), gain(1q), del(1p), del(17p)) or gene expression SKY92 (SkylineDx) profiling, or with PCL (circulating plasmablasts >20%) and enrolled in OPTIMUM. Induction consisted of 6 cycles of Dara-CVRd, HDMEL and ASCT augmented with bortezomib, followed by Dara-VR(d) consolidation for 18 cycles and Dara-R maintenance. Primary trial endpoints are minimal residual disease (MRD) status post ASCT and progression-free survival. Secondary endpoints include response, safety and quality of life. <h3>Results</h3> Median follow-up for the 107 patients in the safety population was 22.2 months (95% CI: 20.6 – 23.9). At baseline, 27% of patients were ISS stage I, 40% stage II and 32% stage 3 with 1.0% missing data and patient median age was 60 (range 35 to 78) years. 53% of patient tumors carried double-hit genetics and 77% a SKY92 high-risk signature. Two patients died early during induction due to myeloma-related infection. Bone marrow aspirates suitable for MRD assessment by flow (10-5 sensitivity) were available for 81% of patients at end of induction and 78% at D100 post ASCT. Responses in the ITT population at end of induction were 94% ORR with 22% CR, 58% VGPR, 15% PR, 1% PD, 5% timepoint not reached (TNR; withdrew, became ineligible or died) and at D100 post ASCT 83% ORR with 47% CR, 32% VGPR, 5% PR, 7% PD, 10% TNR. For PCL patients, response post ASCT was lower with 22% CR, 22% VGPR, 22% PR and 22% PD, 11% TNR. MRD status was 41% MRD-neg, 40% MRD-pos and 19% not evaluable post induction and 64% MRD-neg, 14% MRD-pos and 22% not evaluable at D100 post ASCT. Most frequent induction grade 3/4 AEs were neutropenia (21%), thrombocytopenia (12%) and infection (12%). <h3>Conclusions</h3> We report here high response and MRD-negativity rates with Dara-CVRd quintuplet induction and augmented ASCT in difficult-to-treat UHiR NDMM and PCL patients, with good tolerability and all-oral/subcutaneous deliverability. However, some early progressors highlight the ongoing need for innovation in UHiR MM and PCL.

P-031: Importance of flow cytometry assessment of circulating plasma cells and its connection with clinical characteristics of primary and secondary plasma cell leukemia

<h3>Background</h3> Plasma cell leukemia (PCL) is a rare and very aggressive plasma cell (PC) disorder characterized by the presence of circulating plasma cells (cPC) in peripheral blood (PB). Dismal outcome of PCL requires early diagnosis with appropriate analytical tools. Development of flow cytometry (FC) together with some newly analysed antigens may reveal some marker affecting the prognosis of PCL patients. <h3>Aim</h3> Analysis of phenotypic profile of cPC/PCs to find association with clinical outcomes and to evaluate the prognostic value of analyzed markers. <h3>Methods</h3> Total of 33 primary and secondary PCL patients were investigated. PCs quantity and phenotype profile was analysed by polychromatic FC in PB and bone marrow (BM). <h3>Results</h3> Flow cytometry is an excellent method for cPCs identification as a significantly higher number was identified by FC than by morphology. Thus FC should be incorporated as a diagnostic method for preventing late diagnosis of PCL. Although the phenotypic profile of both PCLs did not differ too much, with low level of CD19, CD20, CD27, CD28, CD81 and CD117 expression, some heterogeneously expressed antigens (CD44, CD56, CD200, nestin etc.) may contribute to identification of patients with later extramedullary involvement, high risk of progression and shortened survival. <h3>Conclusions</h3> FC should be incorporated in PCL diagnostics as not only exact method providing number of cPCs, which is surprisingly overcoming morphology assessment. Moreover, PCL phenotype profile could be connected to patient's diagnosis and possible prognosis as well. <h3>Funding</h3> Supported by grant AZV NV18-03-00203.

P-096: Tackling pyrimidine biosynthesis - CTP Synthase 1 is a novel target in the treatment of multiple myeloma

<h3>Background</h3> Clinical progress in patients with high-risk multiple myeloma (MM) is limited and median survival remains at less than two years. Overexpression of cell cycle and proliferation-related genes is frequently observed in high-risk MM and novel treatment strategies for these patients are urgently needed. While the demand for pyrimidines is saturated via salvage pathways in resting cells, proliferating cells depend on the de novo synthesis of pyrimidines to meet the high demand for nucleotides. We therefore speculated that this pathway represents an attractive target in proliferation-associated high-risk myeloma. <h3>Methods</h3> In silico analysis of publicly available gene expression data sets was used to analyze CTP Synthase 1 (CTPS1) expression in different MM subgroups. In vitro, CTPS1 was evaluated as a target via generation of CRISPR/Cas9 CTPS1 knock-out cell lines. Apoptosis induction, cell cycle analysis and membrane potential of the cells were analyzed by flow cytometry. Additionally, the CTPS1 inhibitor STP938 (Step Pharma) was tested in 12 MM cell lines for its anti-myeloma properties. Uridine and cytidine rescue experiments were used to confirm the specificity of the compound. Previously established resistance models to pomalidomide and carfilzomib were used to demonstrate the efficacy of STP938 in advanced disease stages. <h3>Results</h3> In silico gene expression analysis revealed an upregulation of CTPS1 in MM and plasma cell leukemia patients compared to healthy-donor bone marrow plasma cells. Additionally, CTPS1 was found to be upregulated in patients with a proliferative gene expression pattern and high expression levels were linked to poor patient outcome. In vitro, stable CTPS1 knock-out clones failed to proliferate in the absence of exogenous cytidine which can be recycled via the nucleotide salvage pathway. Proliferation inhibition was accompanied by induction of an S-phase cell cycle arrest and apoptosis. The highly specific CTPS1 inhibitor STP938 showed potent inhibition of cell viability in 6 out of 12 cell lines. In accordance with the results obtained in genetic perturbation experiments we observed apoptosis induction, S phase arrest, and loss of mitochondrial membrane potential upon treatment with STP938. Addition of mM concentrations of exogenous cytidine, but not uridine, protected MM cell lines from apoptosis underlining the specificity of STP938. Importantly, the compound remained effective in models resistant to carfilzomib and pomalidomide. <h3>Conclusions</h3> Our in silico data establish CTPS1 as a potential novel target for proliferation associated high-risk disease. In vitro, the essential role of CTPS1 was confirmed by CRISPR/Cas9 deletion and the CTPS1 inhibitor STP938 was found to be highly efficacious in inducing apoptosis in several myeloma cell lines. Pre-clinical experiments have thus confirmed the drugability of CTPS1 and therefore strongly support the further evaluation of STP938.