Relapsed Multiple Myeloma Patients Research Articles

PB2096 HIGH PLASMA CELL PROLIFERATIVE INDEX IS ASSOCIATED WITH A DOMINANT EXPANSION OF A SINGLE IMMUNOPHENOTYPIC SUBCLONE AND PREDICTS RESPONSE TO LENALIDOMIDE/DEXAMETHASONE IN RELAPSED MULTIPLE MIELOMA

Background:Plasma cell proliferative index (PCPI) is an easily available prognostic parameter as well as a reliable progression indicator in multiple myeloma (MM). Despite this, there are no data regarding the utility of PCPI as a routine indicator to predict the response to second‐line lenalidomide based treatments.Aims:Study of theprognostic value of PCPI in patients with relapsed MM treated with lenalidomide/dexamethasone (len/dex) compared to other available indicators (International Staging System disease stage, high risk cytogenetics, serum albumin, LDH, β2‐microglobulin, depth and duration of the previous response) as well as to immunophenotypic features.MethodsStudy design: Observational retrospective study in a cohort of 108 patients with relapsed MM treated with len/dex (Jun 2014‐Dec 2018). The median age was 69.7 years (range, 44 to 90) with 55 males and 53 females. Study variables: Immunophenotype, PCPI and genetics using fluorescent in situ hibridation were performed in bone marrow specimens before the start of len/dex. Responses to len/dex were evaluated after 6 cycles, also recording time to progression. The primary efficacy endpoint was the progression‐free survival (PFS), and secondary efficacy endpoints included overall response rate (ORR) and rates of very good partial response or better (CR + VGPR). Flow‐cytometry: Flow cytometer FACSCanto II, BD CA was used. Study of PCPI (percentage of plasma cells in S‐phase) was performed using a single propidium iodide/CD138 BV421 double‐staining technique (fig 1‐A). Plasma cell subclones were identified using two specifically designed 8‐color combinations as previously described. Statistical methodology: χ2 and U Mann‐Whitney tests were used to estimate statistically significant differences. Survival curves were plotted using the Kaplan‐Meier method, and differences were assessed with the log‐rank test. For multivariate analysis, stepwise Cox proportional hazard and logistic regressions were performed with SPSS Version 15.0 software.Results:A cut‐off PCPI value of 8% discriminates between two different groups of patients according to the detected subclones (mean of 1.14 subclones in PCPI> 8% versus 1.96 in PCPI≤8%, p < 0.05%). PCPI value was not significantly correlated with the other studied variables such as R‐ISS or genetics. Univariate analysis demonstrated that only PCPI and R‐ISS staging system were significantly associated with ORR and PFS. Overall responses (71.9%) were lower in MM > 8% (57.2% vs 79.3%; P < .05). The rates of best responses (CR + VPGR: 29.5%) were also lower in MM > 8% group (8.3% vs 39.3%; P < .01). PFS (median 24.2 months) were shorter in MM > 8% (11.1 months, vs 38.2 months p<. 001, see figure 1). In the multivariable analysis only PCPI > 8% is associated with PFS (Hazard Ratio 8.1‐ IC95% 7.2‐9.0) and predicts the duration of the response independently from R‐ISS, genetics, number of subclones detected and the other studied variables.Summary/Conclusion:Plasma cell proliferation measurement using PCPI is an easy technique that provides prognostic information in relapsed MM patients independently of the other risk factors. The expansion of a single subclone seems to reflect a loss of intraclonal equilibrium and may be an important factor related to the kinetics of disease progression. The perceived impact of the PCPI in the efficacy of len/dex combination must be better studied in order to understand if subsequent modifications in lenalidomide containing regimens should be considered in selected patients.image

PS1357 FITNESS SIGNATURES IN MULTIPLE MYELOMA PROGRESSION AND RESISTANCE

Background:The amount of descriptive genetic data in multiple myeloma (MM) is growing exponentially. Clonal dynamics leading to disease progression and resistance development are evident and have been described in a number of exemplary MM patients. Still, for most identified genetic lesions, the specific impact on clinic and biology remains unclear.Aims:Aiming for a better understanding of the underlying mechanisms of clonal progression, we developed clonal competition models, based on co‐culture of fluorescence‐marked isogenic MM cells with or without the alteration under study. This experimental setting allows us to study the implications of a specific lesion and its interactions with different environmental conditions such as drug exposition.Methods:To study the effect of mono‐ and bi‐allelic TP53 lesions and the impact of proteasome subunit mutations we selected the TP53 wild‐type (WT) cell line AMO1. As this cell line has a weak response to IMiDs, we generated L363 sublines with IKZF1 or PSMB5 alterations and MM1S cells with IKZF1 or TP53 lesions. All these sublines and their parental (WT) controls were then stably marked with EGFP or LSS mKate RFP. Then, the co‐cultures with mutant and WT cells were monitored by flow cytometry under different therapeutic conditions.Results:Exploring the CoMMpass dataset, we detected one patient (MMRF_1152) who acquired two sub‐clonal nonsense CUL4B mutations after IMiD exposition. In our clonal competition assays, CUL4B KO cells were selected in the presence of LEN but they induced a survival disadvantage when the drug was not present (Figure, top). We previously described a similar observation regarding PSMB5 mutations affecting the chymotrypsin‐like catalytic core (PI binding). In vitro these alterations generated an impasse on the proteasome activity that potentially affects cell growth (Barrio S, et al. Leukemia 2019). Our results suggest that some of the acquired mutations may induce survival fitness under drug exposition but represent a disadvantage when the therapy is removed. This could explain why such alterations are not being detected more frequently in relapsed MM patients. Of note, however, a hotspot mutation identified in the LEN binding area of IKZF1 (A152T) did not have any negative impact on cell growth without treatment but was selected in the presence of LEN. IKZF1 mutations outside the LEN binding area (Q170D and R439H) did not provide any advantage to the cells. Besides survival fitness, we have also observed growth fitness, a selection that occurs independently of therapy. When cells with mono‐ or bi‐allelic TP53 lesions were co‐cultured with WT cells, a strong growth dynamic was observed. This advantage remained under exposure to Melphalan (MEL) or Bortezomib. Of interest, MEL seems to increase the fitness of cells with mono‐allelic TP53 alterations.Summary/Conclusion:In summary, we observed three different types of fitness advantages (Figure, bottom): Negative survival fitness, induced by drug exposition but with negative impact on basal cell growth as described for CUL4B or PSMB5. Neutral survival fitness (IKZF1), without this negative effect when the drug is absent. Growth fitness, independent of treatment exposition (TP53 mono‐ and bi‐allelic lesions). Altogether, our data suggest that it is possible to apply clonal competition assays to perform analytical or even quantitative genetics. This approach might help in the future to select the best regimen to control the fitness advantages induced in MM cells by patient‐specific lesions.image

PF566 INCREASE OF MITOCHONDRIAL ACTIVITY CONTRIBUTES TO RELAPSE IN MULTIPLE MYELOMA, A NOVEL THERAPEUTIC OPPORTUNITY

Background:Preliminary results (Ruiz‐Heredia, ASH 2017) showed an increase of the mitochondrial burden in the Multiple Myeloma (MM) and its progression, suggesting to have an important role in the pathogenesis of the disease.Aims:We planned to decipher the role of the mitochondria in the MM disease and its progression, and the potential exploitation of mitochondrial activity as a functional target in the MM therapy.Methods:In order to understand the role of mitochondria in MM and its therapeutic exploitation, firstly we studied factors involved in the mitochondrial function gene expression (c‐Myc, TFAM, EF‐Tu, NRF1 and HNRNPK RT‐PCR), protein expression (COXII IHC), and mitochondrial activity (histoenzymatic‐HE assay of COX) in 77 MM patients.Furthermore, we have tested the effect of tigecycline, a mitochondrial inhibitor, alone or in combination with bortezomib in the MM cell lines JJN3, L363 and NCI‐H929. To characterized the molecular mechanisms underlying the cytotoxic effect of tigecycline we analysed OXPHOS expression by WB and mitochondria activity by HE assay. Finally, we followed an in vivo experiment in NSG mice (n = 40) 6–8 week‐old engrafted with the JJN3‐GFP cell line (1 x 106) via tail vein and treated by 4 weeks. Analysis of the in vivo imaging and survival curve were obtained.Results:Mitochondrial representative gene and protein expression and activity were found increased in MM relapse stage patients. We showed overexpression of C‐Myc, TFAM and EF‐Tu, and an increased tendency for HNRNPK on the MM relapsed group (n = 34) (Fig. 1A). Moreover, IHC reveals overexpression of mitochondrial COXII protein in relapse MM patients (n = 32; p‐value ∗∗ <0.001) (Fig. 1B). By functional assays we have demonstrated that gene and protein overexpression drives to an increase of activity (COX HE) in MM at relapse (N = 11 p‐value ∗∗∗<0.0001). (Fig. 1C). Together these results suggest elevation of mitochondrial activity plays a role in the mechanism of resistance to treatment and/or progression of MM and the consequent relapse of the patients.In vitro studies with tigecyline and the combination with the frontline MM drug, bortezomib showed cytotoxic effects in three MM cell lines (IC50 JJN3 11,91 μM; IC50 L363 10,21 μM and NCI‐H929 26,37 μM, p‐value ∗<0.05). Moreover, bortezomib and tigecyline showed high levels of synergism (CI 0,19) (Fig. 1D). The cells treated with tigecycline and the combination reflect diminishing in the expression of the respiratory chain complexes, suggesting a reduction of mitochondrial activity, and being validated in lower activity measured by the HE assay of COX (Fig. 1E). Finally, mice groups treated with tigecycline alone or in combination with bortezomib reported a better survival and lower JJN3‐GFP infiltration (n = 40; p‐value ∗<0.05) (Fig. 1F).Summary/Conclusion:To sum up, we observed that mitochondria activity plays a pivotal role in MM development and specially its progression and/or potential treatment resistance, correlating the increase of activity with MM patient's poor outcomes and relapse prone.imageWe proof the potential therapeutic exploitation of mitochondria in the disease, and the value of tigecycline, in monotherapy and in a synergic combination with frontline MM treatment Bortezomib. This new approach should be considered as a novel target therapy in MM, especially in relapse patients.

PS1432 3‐WEEKLY DARATUMUMAB‐IMID‐DEXAMETHASONE IS HIGHLY EFFICACIOUS, HENCE FINANCIALLY AFFORDABLE WITH ENORMOUS ECONOMIC IMPACT FOR RELAPSED/REFRACTORY MULTIPLE MYELOMA IN LESS AFFLUENT COUNTRIES

Background:Daratumumab (dara) with immunomodulatory agents (IMiD) and dexamethasone (dex) is highly effective in relapsed multiple myeloma (MM). The recommended schedule of dara is weekly for 8 doses, followed by 2‐weekly for 8 doses, and then every 4‐weekly thereafter. Given the high cost and the long half‐life as an antibody, a 3‐weekly dosing of dara was used together with IMiD/dexamethasone.Aims:Dara at 16 mg/kg was used every 3‐weekly with lenalidomide or pomalidomide. Patient achieving best response received single agent IMiD maintenance until disease progression.Methods:Fourteen relapsed MM patients were enrolled. One had received weekly dara from a private oncologist, hence was excluded from analysis. Thirteen patients at a median age of 63 years (range: 50–84 years) were studied. The median number of previous therapies was 2 (range: 1–5), with nine patients (69.2%) having undergone autologous stem cell transplantation. Three patients (23.1%) were refractory to bortezomib, seven patients (53.8%) to lenalidomide, and eight patients (61.5%) to last treatment. At relapse, two (15.4%) had high LDH, eight (61.5%) impaired renal function, and three (23.1%) extramedullary disease. Treatment was dara‐lenalidomide‐dex in six (46.2%), and dara‐pomalidomide‐dex in seven (53.8%).Results:Responses after four cycles included CR in 5 patients (38.5%), VGPR in five patients (38.5%), and PR in three patients (23.1%). After a median of four dara infusions (range: 3–10), the best responses included CR in seven patients (53.8%), nCR in two patients (15.4%), VGPR in two patients (15.4%), and PR in two patients (15.4%). Median time to VGPR was one month. At 10 months, the OS was 90%, and PFS 54.7%. Three patients progressed, one of whom died of ruptured hepatic plasmacytoma. The most frequent toxicity was haematological especially neutropenia (all grades: 92.3%, Grade 3/4: 76.9%), infusion reaction (38.5%, all grade 1/2), neuropathy (38.5%, all grade 1/2), gastrointestinal (all grades: 38.5%, grade 3/4 : 7.7%), and sepsis (all grades: 30.8%; grade 3/4: 23.1%). Neutropenia was effectively prevented with prophylactic G‐CSF.Summary/Conclusion:In conclusion, a 3‐weekly dara‐IMiD‐dex regimen is highly efficacious, inducing deep and rapid responses, hence cost‐effective for less affluent countries. In view of prevalent grade3/4 neutropenia despite less frequent dara, 3‐weekly dara might be more suitable for Asian patients.image

PS1358 POTENT ANTI‐MYELOMA EFFICACY OF DENDRITIC CELL THERAPY IN COMBINATION WITH POMALIDOMIDE AND PROGRAMMED DEATH‐LIGAND 1 BLOCKADE IN A PRECLINICAL MODEL OF MULTIPLE MYELOMA

Background:Dendritic cell (DC)‐based vaccines are recognized as a promising immunotherapeutic strategy against cancer, and various combination approaches have been developed to enhance DC function by modulating immune responses and tumor microenvironment.Aims:In this study, we investigated the efficacy of DC vaccination in combination with pomalidomide and programmed death ligand‐1 (PD‐L1) blockade in a murine model of multiple myeloma (MM).Methods:MOPC‐315 cell lines were injected subcutaneously to establish MM bearing mice. Four test groups were used to mimic clinical protocol: (1) PBS control, (2) DCs + pomalidomide/dexamethasone, (3) Pomalidomide/dexamethasone + PD‐L1 blockade, and (4) DCs + pomalidomide/dexamethasone + PD‐L1 blockade.Results:The combination of DCs + pomalidomide with dexamethasone + PD‐L1 blockade inhibited more strongly tumor growth and prolonged survival of treated mice compared to the other groups. This effect was associated with a significant reduction in immune suppressor cells, such as myeloid‐derived suppressor cells, regulatory T cells, and M2 macrophages, and level of immunosuppressive factors, such as vascular endothelial growth factor, transforming growth factor‐β, and interleukin‐10, and with the significant induction of immune effector cells, such as CD4+ and CD8+ T cells, memory T cells, natural killer (NK) cells, and M1 macrophages, in the spleen and tumor microenvironment. Functional activities of cytotoxic T lymphocytes and NK cells in spleen were also enhanced by the combination of DCs + pomalidomide with dexamethasone + PD‐L1 blockade.Summary/Conclusion:The collective findings in the murine MM model suggest that DC vaccination combined with pomalidomide and PD‐L1 blockade synergistically enhance antitumor immunity through two‐way mechanism, which inhibits immunosuppressive cells while activating effector cells with superior polarization of the Th1/Th2 balance in favor of the tumor immune response.

3-weekly daratumumab-IMiD-dexamethasone is highly efficacious and cost-effective in relapsed/refractory multiple myeloma.

e19521 Background: Daratumumab (dara) with immunomodulatory agents (IMiD) and dexamethasone (dex) is highly effective in relapsed multiple myeloma (MM). The recommended schedule of dara is weekly for 8 doses, followed by 2-weekly for 8 doses, and then every 4-weekly thereafter. Given the high cost and the long half-life as an antibody, a 3-weekly dosing of dara was used together with IMiD/dexamethasone. Methods: Dara at 16mg/kg was used every 3-weekly with lenalidomide or pomalidomide. Patient achieving best response received single agent IMiD maintenance until disease progression. Results: Fourteen relapsed MM patients were enrolled. One had received weekly dara from a private oncologist, hence was excluded from analysis. Thirteen patients at a median age of 63 years (range: 50-84 years) were studied. The median number of previous therapies was 2 (range: 1-5), with nine patients (69.2%) having undergone autologous stem cell transplantation. Three patients (23.1%) were refractory to bortezomib, seven patients (53.8%) to lenalidomide, and eight patients (61.5%) to last treatment. At relapse, two (15.4%) had high LDH, eight (61.5%) impaired renal function, and three (23.1%) extramedullary disease. Treatment was dara-lenalidomide-dex in six (46.2%), and dara-pomalidomide-dex in seven (53.8%). Responses after four cycles included CR in 5 patients (38.5%), VGPR in five patients (38.5%), and PR in three patients (23.1%). After a median of four dara infusions (range: 3-10), the best responses included CR in seven patients (53.8%), nCR in two patients (15.4%), VGPR in two patients (15.4%), and PR in two patients (15.4%). Median time to VGPR was one month. At 10 months, the OS was 90%, and PFS 54.7%. Three patients progressed, one of whom died of ruptured hepatic plasmacytoma. The most frequent toxicity was haematological especially neutropenia (all grades: 92.3%, Grade ¾: 76.9%), infusion reaction (38.5%, all grade ½), neuropathy (38.5%, all grade ½), gastrointestinal (all grades: 38.5%, grade ¾: 7.7%), and sepsis (all grades: 30.8%; grade ¾: 23.1%). Neutropenia was effectively prevented with prophylactic G-CSF. Conclusions: In conclusion , a 3-weekly dara-IMiD-dex regimen is highly efficacious, inducing deep and rapid responses, hence cost-effective for less affluent countries. In view of prevalent grade 3/4 neutropenia despite less frequent dara, 3-weekly dara might be more suitable for Asian patients.

Healthcare utilization and costs among relapsed or refractory multiple myeloma patients on carfilzomib or pomalidomide as monotherapy or in combination with dexamethasone

Aim: To compare monthly healthcare resource utilization (HRU) and costs among adult patients with multiple myeloma (MM) receiving second or subsequent line of treatment (LOT) with carfilzomib or pomalidomide as monotherapy or in combination with dexamethasone. Methods and materials: Adult MM patients who received carfilzomib or pomalidomide as second/subsequent LOT between 2006 and 2014 were selected from the MarketScan databases. LOT was determined using Medical/pharmacy claims using a published algorithm. For each patient, first LOT with carfilzomib or pomalidomide was defined as index LOT. Patients with first LOT as index LOT, who received other chemotherapy in combination with carfilzomib or pomalidomide, or who underwent stem cell transplant (STC) during index LOT were excluded. Monthly HRU and costs during index LOT were compared using inverse probability of treatment weights (IPTW) based on propensity scores for receipt of carfilzomib estimated by logistic regression with LOT, patient demographics, Charlson index, comorbidities, pre-index healthcare cost, and receipt of prior SCT as covariates. Results: After weighting, baseline characteristics were well balanced among 114 carfilzomib and 144 pomalidomide patients. Mean (95% CI) numbers of outpatient visits per month were 7.1 (5.2–8.0) with carfilzomib and 4.7 (3.9–6.1) with pomalidomide (p = 0.006). Otherwise, there were no statistically significant differences between the groups in mean monthly HRU and costs or median time to therapy discontinuation. Mean (95% CI) monthly total healthcare costs were $19,776 (15,322–27,748) with pomalidomide and $17,321 (12,412–21,874) with carfilzomib (p = 0.522). Limitations: Comparison of carfilzomib vs pomalidomide may be biased if there are unobserved factors not balanced by IPTW. The relatively small sample size limits the power of analyses to detect potential differences between treatment groups. Conclusions: Monthly HRU and costs are similar among patients with relapse or refractory MM patients receiving carfilzomib or pomalidomide as monotherapy or in combination with dexamethasone.

Maintenance Therapy after Autologous Stem Cell Transplant Is Associated with Less Biochemical Relapse in Multiple Myeloma Patients

Maintenance therapy has been associated a significantly longer time to disease progression and significantly improved overall survival (OS) among patients with multiple myeloma (MM). However, the impact of maintenance therapy on the nature of MM relapse is largely unknown. Generally relapse can be categorized in two broad categories as symptomatic, or biochemical relapse. We hypothesized that long-term continuous exposure to lenalidomide induces crucial changes in the myeloma microenvironment leading to a discordance between the resurgence of secretory function and the recurrence of aggressive behavior of myeloma cells leading to a higher frequency of biochemical. All MM patients with measurable disease who received HSCT at the University Hospital, Cleveland, OH from 2007 to 2016 were reviewed (Fig. 1). Baseline and treatment characteristics, response status, and monitoring data prior to relapse were extracted. If the serologic relapse had coincided with clinical relapse, defined as per CRAB criteria, patient was categorized as clinical relapse, and otherwise as biochemical relapse. Type of MM was categorized as paraprotein only (PO), paraprotein and light chain (PL), light chain escape (LE) and clinical only (CO) relapse (Table 1). Baseline and treatment characteristics are detailed in Table 2. Study population included 124 pts who relapsed after ASCT (Fig. 1), divided in two cohorts based on history of receiving any maintenance therapy or no maintenance (77 vs. 47 patients, respectively). Median age was 59.8 years old (range: 36-79). The median time from diagnosis to ASCT was 10 months. There was only one CO relapse in the maintenance cohort. There was no difference in rate of high risk disease between two cohorts. The maintenance agents included immunomodulatory drugs in 70 pts (91%), proteasome inhibitors in 5 pts (6%) and a combination of both in 2 pts (3%). PFS was 40.1 months in the maintenance group vs. 29.2 months in the no maintenance group (p=0.0001). There was no statistically significant difference in serum paraprotein values at diagnosis or relapse between the two cohorts (Fig. 1A). LCE was more common in the maintenance group. Thirteen patients (28%) in the no maintenance cohort had CRAB relapse compared to 35 patients (45%) in the maintenance cohort (hazard ratio: 0.71, 95% CI: 0.51-0.92, p=0.031). The type of end organ dysfunction at clinical relapse is shown in bar graphs in Fig. 2B. Taken together, our results suggest that although maintenance therapy postpones disease relapse, it also impacts dynamics of the resurgence of secretory function and shifts the nature of recurrence toward less biochemical relapse. Future studies will employ next generation sequencing combined with high sensitivity flow cytometry to identify the molecular basis of relapse. Genomics and cell surface markers may then more accurately predict relapse in MM patients on maintenance therapy.

Assessment of Red Blood Cell Distribution Width and Multiple Myeloma in a Guangxi Population: a Retrospective Study.

Red blood cell distribution width (RDW) has been reported as a marker for inflammation and tumors. The present study aims to investigate the use of RDW in patients with multiple myeloma (MM). Seventy-three patients with newly diagnosed symptomatic multiple myeloma (SMM), 39 patients with relapsed multiple myeloma (RMM), and 91 healthy individuals were recruited into this study. The demographic and laboratory parameters were reviewed retrospectively, and the correlation between RDW and other parameters among groups were evaluated by Spearman's correlation analysis. The sensitivity and specificity of RDW were determined by receiver operating characteristic (ROC) curve analysis. The RDW values in both SMM and RMM were significantly higher than in the healthy individuals (p < 0.001). In SMM patients with International Staging System (ISS) Stages II and III, the level of RDW was higher than in the patients with ISS Stage I; however, there was no significant difference between each ISS stage in RMM patients. The RDW strongly correlated with platelet distribution width (PDW), cystatin C, serum beta2-microglobulin (Sβ2M), hemoglobin (HGB), hematocrit (HCT), albumin (Alb), and calcium (p < 0.05) in SMM patients, and RDW in RMM patients had a positive or negative correlation with PDW, Sβ2M, globulin, HGB, absolute neutrophil count, platelet count, HCT, and Alb (p < 0.05). The ROC curve analysis showed that RDW > 13.5 had 94.5% sensitivity and 63.7% specificity for SMM, and 92.3% sensitivity and 63.7% specificity for RMM. Elevated RDW in MM patients was associated with the stage of the disease.

Immunotherapy in myeloma: how far have we come?

The treatment of multiple myeloma (MM) has evolved substantially over the past decades, leading to a significantly improved outcome of MM patients. The introduction of high-dose therapy, especially, and autologous stem cell transplantation, as well as the development of new drugs, such as immunomodulatory drugs (IMiDs) and proteasome inhibitors have contributed to the improvement in survival. However, eventually most MM patients relapse, which indicates that there is a need for new agents and novel treatment strategies. Importantly, the long-term survival in a subset of MM patients after allogeneic stem cell transplantation illustrates the potential of immunotherapy in MM, but allogeneic stem cell transplantation is also associated with a high rate of treatment-related mortality. Recently, a better insight into several immune-evasion mechanisms, which contribute to tumor progression, has resulted in the development of active and well-tolerated novel forms of immunotherapy. These immunotherapeutic agents can be used as monotherapy, or, even more successfully, in combination with other established anti-MM agents to further improve depth and duration of response by preventing the outgrowth of resistant clones. This review will discuss the mechanisms used by MM cells to evade the immune system, and also provide an overview of currently approved immunotherapeutic drugs, such as IMiDs (e.g. lenalidomide and pomalidomide) and monoclonal antibodies that target cell surface antigens present on the MM cell (e.g. elotuzumab and daratumumab), as well as novel immunotherapies (e.g. chimeric antigen receptor T-cells, bispecific antibodies and checkpoint inhibitors) currently in clinical development in MM.

Novel Agents in Multiple Myeloma.

The therapeutic landscape of multiple myeloma (MM) has dramatically changed in the last 15 years with the advent of immunomodulatory drugs and proteasome inhibitors. However, majority of MM patients relapse, and new therapies are needed. Various agents with diverse mechanisms of action and distinct targets, including cellular therapies, monoclonal antibodies, and small molecules, are currently under investigation. In this review, we report novel drugs recently approved or under advanced investigation that will likely be incorporated in the future as new standard for MM treatment, focusing on their mechanisms of action, cellular targets, and stage of development.

CD14+CD16+ Monocyte Binding to Myeloma Cells Is Required for Daratumumab Dependent Killing in Multiple Myeloma Patients

Recently, the introduction of anti-CD38 monoclonal antibody, Daratumumab (DARA), in multiple myeloma (MM) therapy has improved the response rate of relapsed MM patients. However only a fraction of the DARA-treated patients respond, thus further studies on DARA mechanisms of action are needed. Because the antibody dependent cellular phagocytosis (ADCP) mediated by monocyte, is one of the mechanisms through DARA exerts its anti-MM activity, an ex-vivo approach was established in order to investigate which mechanisms or patient's immunological characteristics could influence DARA-mediated killing of MM cells.Bone marrow mononuclear cells (BM-MNCs) obtained from 25 MM patients (12 newly diagnosed and 13 relapsed MM) were analyzed at time 0 (T0) by flow cytometry. We checked the % of plasma cells (PCs) (CD138+ cells), % of total monocytes (CD14+ cells) and their two subsets (CD14+CD16- or CD14+CD16+ cells), the ratio between % of CD14+ and % of CD138+ cells (CD14+:CD138+ ratio) and the median fluorescence intensity (MFI) of CD38 and of the immuno-check points CD47 on PCs and CD172a (SIRPα) on monocytes. Subsequently, BM-MNCs were treated with control IgG (10µg/ml), DARA (10µg/ml) and the F(Ab)2 portion of DARA (DARA F(Ab)2) (10µg/ml) for 48 hours and then the % variation of surviving 7AAD- CD138+ cell, the modification of the % of monocyte or subsets analyzed and the % of PCs that are attached to monocyte (identified as CD138+ cells also positive to CD14) were evaluated by flow cytometry.Firstly, we found that DARA significantly exploited its anti-MM activity (median % variation of surviving CD138+ cells: 69.05%, p=0.0007) compared to IgG control while DARA F(Ab)2 did not have any killing effect (median % variation of surviving CD138+ cells: 97.33%) compared to the control.Secondly, we detected that the % of total of monocytes and their subsets (CD14+CD16+ or CD14+CD16-) composition were not modulated by DARA or DARA F(Ab)2 treatment compared to IgG. Indeed, only in presence of DARA, we observed that a double positive population of CD138+CD14+ cell significantly increased compared to IgG control (mean %: 15.76 vs 3.14, p=<0.0001) and to DARA F(Ab)2 condition (mean %:15,76 vs 1,48, p=<0.004). Moreover, we found that monocytes involved in the double positive population CD138+CD14+ were almost completely CD14+CD16+ monocytes. Indeed, we have divided the patient' samples in high responder (HR) and low responder (LR) based on the median % of survival cell after DARA treatment (HR: <69.05% and LR:>69.05% of surviving PCs). Interestingly, in the HR group compared to LR group were significantly increased the % of double positive CD138+CD14+ (median % HR:21.59 vs LR: 7.41, p=0.035), the % of CD138+ cells bonded to CD14+CD16+ (median % HR:13.28 vs LR: 3.93, p=0.048) and the CD14+:CD138+ ratio measured at T0 (median HR:0.63 vs LR: 0.32, p=0.0158). Moreover, in 5 relapsed MM patient, we have correlated the ex-vivo response to DARA with the type of in vivo response after DARA single-agent treatment.In addition in our cohort of patients, we observed that the % of surviving CD138+ cells after DARA treatment negatively correlate with the CD14+:CD138+ ratio at T0 (r:-0.628, p=0.0023), with the % of CD138+CD14+ population (r:-0.602, p=0.0039) and with the % of CD138+CD14+CD16+ population (r:- 0.657, p=0.0238) but did not correlate with the MFI of CD38 expression on PCs and the % of CD14+CD16+ at T0.Finally, to go further inside the mechanism involved in DARA response, we have explored the role of the inhibitory axis CD47-CD172a in the ADCP DARA-induced in 5 ex-vivo samples from our cohort of MM patients. We found that the MFI of CD47 strongly positively correlated with the % of surviving CD138+ cells (r: 0.9897; p=0.010) after DARA treatment; on the other hand, we have not reported any correlation with the MFI of CD172a on monocytes. The results of these analyses are continuously updating increasing the number of samples tested.In conclusion, these data highlight that monocyte binding to PCs, in particular those CD14+CD16+, plays a central role in DARA killing effect independently of % subset composition in the pre-treatment samples, suggesting that there are mechanisms that regulate the effectiveness of the monocyte-based killing effect on malignant PCs, as the immune-suppressive axis CD47-CD172a, giving the rationale design to identify new strategies to increase the efficiency of DARA-based therapeutic regimen. DisclosuresMalavasi:Takeda Pharmaceutical Co: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen Pharmaceutica: Membership on an entity's Board of Directors or advisory committees, Research Funding. Aversa:Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Honoraria; Basilea: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Giuliani:Takeda Pharmaceutical Co: Research Funding; Celgene Italy: Other: Avisory Board, Research Funding; Janssen Pharmaceutica: Other: Avisory Board, Research Funding.

Impact of Maintenance Therapy on Nature of First Relapse in Multiple Myeloma Patients Underwent Autologous Stem Cell Transplant

Lenalidomide maintenance therapy, initiated around day 100 after autologous stem cell transplantation (ASCT), has been associated a significantly longer time to disease progression and significantly improved overall survival (OS) among patients with multiple myeloma (MM) (McCarthy et al. NEJM 2012). However, the impact of maintenance therapy on the nature of MM relapse is largely unknown. Generally relapse can be categorized in two broad categories as symptomatic, or biochemical relapse. Symptomatic relapse is characterized mostly by high calcium, renal failure, anemia and bony lesions, i.e., CRAB criteria. Biochemical relapse is defined by a resurgence of secretory function of malignant plasma cells without CRAB criteria. We hypothesized that long-term continuous exposure to lenalidomide induces crucial changes in the myeloma microenvironment leading to a discordance between the resurgence of secretory function and the recurrence of aggressive behavior of myeloma cells leading to a higher frequency of biochemical. To define the impact of maintenance therapy on the pattern of disease recurrence and determinants of a more aggressive or indolent relapse course, we retrospectively analyzed two cohorts of MM patients that underwent ASCT.Methods: All MM patients with measurable disease who received ASCT at the University Hospital, Cleveland, OH from 2007 to 2016 were reviewed (Fig. 1). Patients that had received an allogeneic transplant or tandem ASCT, those transplanted more than one year after induction therapy, and those that died during the first three months post-transplantation were excluded. Baseline and treatment characteristics, response status, and monitoring data prior to relapse were extracted. If the serologic relapse had coincided with clinical relapse, defined as per CRAB criteria, patient was categorized as clinical relapse, and otherwise as biochemical relapse. Type of MM was categorized as paraprotein only (PO), paraprotein and light chain (PL), light chain escape (LE) and clinical only (CO) relapse (Table 1). Baseline and treatment characteristics are detailed in Table 2. The univariate association between the type of relapse and key patient and clinical characteristics were assessed using t-test or Fisher's exact test as appropriate.Results: Study population included 124 pts who relapsed after ASCT (Fig. 1), divided in two cohorts based on history of receiving any maintenance therapy or no maintenance (77 vs. 47 patients, respectively). 21 pts were excluded based on the above criteria. Median age was 59.8 years old (range: 36-79). The median time from diagnosis to ASCT was 10 months. There was only one CO relapse in the maintenance cohort. There was no difference in rate of high risk disease between two cohorts. The maintenance agents included immunomodulatory drugs in 70 pts (91%), proteasome inhibitors in 5 pts (6%) and a combination of both in 2 pts (3%). PFS was 40.1 months in the maintenance group vs. 29.2 months in the no maintenance group (p=0.0001). There was no statistically significant difference in serum paraprotein values at diagnosis or relapse between the two cohorts (Fig. 1A). LCE was more common in the maintenance group. Thirteen patients (28%) in the no maintenance cohort had CRAB relapse compared to 35 patients (45%) in the maintenance cohort (hazard ratio: 0.71, 95% CI: 0.51-0.92, p=0.031). The type of end organ dysfunction at clinical relapse is shown in bar graphs in Fig. 2B.Conclusions: Taken together, our results suggest that although maintenance therapy postpones disease relapse in the post-HSCT setting, it also impacts dynamics of the resurgence of secretory function within myeloma cells and shifts the nature of recurrence toward less biochemical relapse. Future studies will employ next generation sequencing prior to and during maintenance therapy combined with high sensitivity flow cytometry to identify the molecular basis of relapse. Genomics and cell surface markers may then more accurately predict relapse in MM patients on maintenance therapy. [Display omitted] DisclosuresCaimi:Genentech: Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Research Funding; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau. Malek:Amgen: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Sanofi: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau.

Chidamide, a Novel Histone Deacetylase Inhibitor, Inhibits Multiple Myeloma Cells Proliferation through Succinate Dehydrogenase Subunit a

Most patients with multiple myeloma (MM) would finally relapse. Current chemotherapy regimens have limited effect on relapse MM patients. As a new histone deacetylase inhibitor, chidamide has been used in malignancy treatment such as peripheral T-cell lymphoma. However, it is still unknown if chidamide can be used in MM.To determine the target gene of chidamide in MM patients, we performed RNA-Seq analysis using 3 MM patients' bone marrow mononuclear cells. Their BMMCs were cultured with 6μM chidamide or not, and six of the most significantly changed coding genes were selected. Realtime RT-PCR showed that compared with DMSO-treated cells, after adding 6μM chidamide, the expression of SDHA and FCER2 was increased and MRPL30 decreased. The expression of SDHA was upregulated and ITGA7 was downregulated in MM patients. Based on the data above, SDHA was considered as the most valuable target gene of chidamide in MM. Realtime RT PCR also showed that SDHA expression in normal volunteers was the highest and followed by patients with MGUS and initial MM. Patients with relapse MM had the lowest SDHA expression.To assess the effects of chidamide on MM cells, we next performed cell proliferation and invasion assay. Chidamide dramatically inhibited proliferation of myeloma cell lines (H929 and OPM-2). However, when SDHA was knocked down by siRNA, this inhibition effect was not dramatically as before in H929 cells. Similarly, chidamide-treated H929 cells achieved a notably lower percentage of cell invasion than those treated with DMSO. Thus, when SDHA was knocked down, this invasive ability was not significantly changed whether chidamide was added or not.CCK8 assay was used to determine dose-response curves of chemotherapeutic agents and synergistic effect of chidamide combined with other agents. he combination index (CI) of lenalidomide and low concentration of bortezomib yielded many of the data points to the area <1 when combined with chidamide treatment, denoting synergistic interactions in MM cell line. Interestingly, when SDHA was knocked down, cells apoptosis induced by bortezomib and lenalidomide combined with chidamide greatly decreased, especially by lenalidomide, which indicated the synergistic effect between chidamide and other agents was induced by SDHA. When SDHA was knocked down by siRNA, most of CI between chidamide and bortezomib or lenalidomide also raised above 1, which indicated the synergistic effect tended to disappear.In order to gain further mechanism of chidamide-SDHA-MM axis, Western Blot was used. As a result, it showed that when SDHA was knocked down in H929 cells by siRNA, expression of HIFα protein was increased. HIFα decreased after adding 6μM chidamide. However, when SDHA was knocked down, chidamide did not regulate the expression of HIFα any longer. ROS in MM patients were much higher than that in normal people, which caused by higher HIFα expression in large extent. Chidamide inhibited ROS production, and similar to HIFα, the ROS production was not sensitive to chidamide any more when SDHA was knocked down. Our findings clatify the mechanism of chidamide treatment in MM through SDHA and reveal a novel therapeutic strategy of MM treatment. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Multiple Myeloma Treatment Is Associated with Enhanced Platelet Reactivity

Multiple myeloma (MM) is associated with elevated levels of thrombotic disease. Poor mobility due to bone disease and older age are contributory factors but a satisfactory molecular or cellular explanation for this has not been established. Furthermore, the treatment of newly-diagnosed or relapsed MM patients with immunomodulatory drugs increases thrombosis risk. In this study, we therefore sought to determine whether platelet function and/or haemostasis is altered during the clinical progression from the benign monoclonal gammopathy of underdetermined significance (MGUS) to the smouldering myeloma (SM, untreated) state, and to establish the impact of lenalidomide therapy in MM patients on platelet reactivity.Patients (MGUS (N=10), SM (N=10) MM (N=4), healthy volunteer/control (N=10)) were recruited at the myeloma clinics at the Royal Berkshire and Oxford University Hospital Trusts. Single blood samples were obtained from controls, MGUS and smoldering myeloma participants. For patients undergoing therapy (lenalidomide, dexamethasone and anti-coagulant or anti-platelet therapy), samples were taken at predose Cy1, Cy1 D14, Cy1 D28 (a week free from lenalidomide administration), and Cy4 D14. All blood samples were taken less than 12 hours from Lenalidomide dosing, and analysis performed within 4 hours. High throughput platelet function analysis was performed on platelet-rich plasma and washed platelets to measure platelet aggregation, secretion and fibrinogen binding in response collagen, collagen-related peptide (a collagen receptor GPVI-selective ligand), ADP, thrombin receptor activatory peptide (TRAP), the thromboxane mimetic U46619 and epinephrine, and full concentration-response profiles obtained for each. The levels of key platelet receptors including GPVI, CD61, CD41b, CD36 and CD31, were also measured by flow cytometry and remained unaltered between groups. In comparison with control samples, platelet functional responses (maximal response, maximal gain and EC50) from MGUS and smoldering myeloma patients were unaltered (EC50: ADP 1µM, collagen-related peptide (CRP-XL) 0.1µg/ml, U46619 1µM, TRAP 1.6µM, epinephrine 1.3µM). Similarly circulating levels of platelet-bound fibrinogen and P-selectin exposure were unaltered (control: 709±194 AU, MGUS: 581±129 AU, SM: 655±148 AU 9 (Mean±SD)). In MM patients during therapy, the levels of these platelet responses (aggregation, fibrinogen binding and P-selectin exposure - a marker for a-granule secretion) were increased 2-4 fold. In most patients this was notable at week 2 and had declined approximately 50% by week 4 of cycle 1 but remained above predose levels, and remained elevated to a similar level in drug cycle 4.The study of further patients (including Bortezomib treated patients as controls) will be required in order to validate these findings which suggest that (1) baseline platelet function is not substantially compromised in MM and SM, (2) lenalidomide and other immunomodulatory drugs may be able to modulate platelets in patients causing increased platelet reactivity, and (3) effects noted are lenalidomide-dependent and not related to inflammatory state secondary to disease response. The effects of exposure of platelets to lenalidomide in vitro in the presence or absence of dexamethasone and a proteasome inhibitor are being tested to explore potential direct effects of the drugs on circulating platelets. Results from these experiments will also be presented. DisclosuresGibbins:Celgene Corporation: Research Funding. Rana:Celgene Corporation: Research Funding. Khan:Celgene Corporation: Research Funding. Shapiro:Freeline Therapeutics Ltd: Consultancy. Grech:Novartis: Other: sponsorship for scientific meetings. Ramasamy:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Ex Vivo Assessment of Tnb-383B, a Bcma-Bispecific Antibody, Against Primary Tumor and Endogenous T Cells from Relapsing Multiple Myeloma Patients

INTRODUCTION: The human B-Cell maturation antigen (BCMA) is a surface marker that is highly expressed on plasma cells and has been recognized as a novel target in multiple myeloma (MM). TNB-383B is a fully human bispecific monoclonal IgG4 antibody. TNB-383B consists of 2 heavy and 1 light chain(s) paired through knob-in-hole technology. The first heavy chain and a kappa light chain form the paratope to recognize and bind human CD3. The second heavy chain is comprised of two identical VH domains in sequence and targets human BCMA with high affinity and avidity. Herein, we describe the ability of TNB-383B to mediate killing of patient-derived tumor cell lysis by endogenous T-cells was assessed ex vivo.METHODS: Bone marrow mononuclear cells (BMMCs) were isolated by density gradient centrifugation from 7 relapsed MM patients enrolled in an IRB-approved biospecimen collection protocol. Freshly isolated BMMC subsets were characterized by flow cytometry, specifically plasma cell (PC) / cytotoxic T cell (CTL) distribution, PC BCMA expression and PC viability were determined. BMMCs were then incubated for 24h (± 2h) with TNB-383B, or negative control, at concentrations ranging from 0.001-1μg. Following incubation, PC lysis, viability, BCMA expression, as well as CTL distribution and degranulation were assessed by flow cytometry. Tukey's sequential trend test was performed for each measured variable, utilizing ANOVA models and contrast statements, to detect linear dose response trends to TNB-383B or negative control treatments. Additionally, a parametric model (EMax) was used for each measured variable to estimate dose response curves, interpolating between tested doses. Two-way factorial ANOVA was utilized to compare the main effects of E:T ratio (or PC phenotype) and dose level and the interaction effect between E:T ratio and dose level on measured variables.RESULTS: Dose-dependent PC lysis was triggered by TNB-383B at concentrations as low as 0.001μg (p=0.0102) while no significant loss of PC was observed with negative control (Figure). This effect was coupled with significant CTL degranulation as expressed by increased CD107a mean fluorescence intensity (MFI) specific to TNB-383B treatment (p=0.0153 at 1μg). Although apoptotic rates (7-AAD+, Annexin V+) of the remaining PC tend to increase among TNB-383B treated compared with isotype control-treated cells, this trend was not significant. As opposed to CTL degranulation, CTL proliferation was not significantly triggered by TNB-383B but was significantly increased when BMMCs were exposed to negative control antibody (p=0.0057 at 0.001 μg). BMMC containing effector to target (E:T) ratio >10 contained lower viable (7-AAD-) PC and higher apoptotic PC counts compared with BMMC specimen with E:T ratio <10 (p<0.001). Using CD45 expression as a surrogate marker of PC maturation and BCMA expression, CD45+ PC displayed higher BCMA expression than CD45- PC (p=0.0189) and were more sensitive TNB-383B-induced killing (p<0.001). Noticeably, overall BCMA expression pre/post TNB-383B exposure remained unaltered.CONCLUSION: Taken together, our findings demonstrate TNB-383B triggers primary PC lysis and CTL degranulation in a dose-dependent fashion ex vivo. The ex vivo bispecific monoclonal antibody assay employed in this study allowed us to identify underlying biological drivers of PC killing efficacy by TNB-383B and may provide a valuable preclinical platform to screen bispecific antibodies and clinical platform to identify mechanism of primary or acquired resistance to the drug. Enrollment of patients with relapsed/refractory MM into a phase I clinical trial with TNB-383B is expected in early 2019. [Display omitted] DisclosuresFoureau:Teneobio Inc.: Research Funding. Pham:Teneobio Inc.: Employment. Force Aldred:Teneobio Inc.: Employment. Buelow:Teneobio Inc.: Employment. Voorhees:Oncopeptides: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: served on an IRC; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Other: served on an IRC; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: served on an IRC; Amgen Inc.: Speakers Bureau; TeneoBio: Consultancy, Membership on an entity's Board of Directors or advisory committees. Usmani:Abbvie, Amgen, Celgene, Genmab, Merck, MundiPharma, Janssen, Seattle Genetics: Consultancy; Amgen, BMS, Celgene, Janssen, Merck, Pharmacyclics,Sanofi, Seattle Genetics, Takeda: Research Funding.

Phase II Trial of Ixazomib and Dexamethasone Versus Ixazomib, Dexamethasone and Lenalidomide, Randomized with NFKB2 Rearrangement. (Proteasome Inhibitor NFKB2 Rearrangement Driven Trial, PINR)

Introduction: Proteasome inhibitors (PI) and immunomodulatory drugs have become the backbone of therapy for multiple myeloma (MM). The oral boron-containing selective and reversible proteasome inhibitor ixazomib has shown to induce deep and durable responses (Kumar RK et la, Blood 2016. 128(20):2415-2422). Triplets containing ixazomib, has shown to be more efficacious than doublet regimens in the relapse setting (Moreau P, et al. N Engl J Med 2016. 374:1621-1634).However, to date there is not companion diagnostics capable of predicting PI response.We have recently discovered that MM patients resistant to PI lack of the ankyrin (ANK) and death domain (DD) present in the 3'-end of NFKB2. Loss of NFKB2 3'end frequently resulted from a structural rearrangements. We found that NFKB2-ANK and -DD are crucial at initiating bortezomib's apoptotic signal by facilitating caspase-8 activation. Activation of this caspase resulted from NFKB2 interaction with FADD/caspase-8/p62 (unpublished data). Based on this findings, we design this study to examine the efficacy of NFKB2 break apart FISH to predict the response to the duplet ixazomib and dexamethasone (Id) vs ixazomib, lenalidomide and dexamethasone (IRd) in early relapse MM patients (1-3 lines of therapy).Methods: In this phase 2 biomarker driven open label trial, relapse patients with <4 lines of therapy were randomized to ixazomib 4 mg weekly 3 of 4 weeks and 40 mg weekly dexamethasone vs Id plus 25 mg of lenalidomide daily days 21/28, based on the status of NFKB2 rearrangement in plasma cells. Patients were screened for NFKB2 rearrangement was detected by NFKB2 break apart FISH. Patients without NFKB2 rearrangement received Id and patients with NFKB2 rearrangement were subsequently randomized in a 1:1 fashion to receive Id or IRd. The primary endpoint is to compare the response rate of Id or IRd at 4 cycles according to the rearrangement status of NFKB2Results: At the moment of interim analysis, 26 patients have achieved 4 cycles of treatment. All treatment groups (NFKB2 FISH [-] Id, n=16, NFKB2 FISH [+] Id, n=6 and IRd, n=4) received a median of 2 prior lines of therapy. A higher ORR was observed in NFKB2 FISH negative treated with Id compared with NFKB2 FISH positive (56.3% CI:29.9%-80.3% vs. 16.7% CI:0.4%-64.1%, P=0.16), including significantly higher rates of ≥very good partial response, ≥ partial response, ≥ minimal response (12%, 37.5%, 6% vs. 0%, 0%, 16%, respectively). ORR for IRd arm is for now 25% CI:0.6%-80.6%. Patients that continue treatment after cycle 4 that achieve minimal response or better improved their depth of response in 6% in Id treated NFKB2 FISH negative patients and 25% of IRd treated NFKB2 FISH negative patients.The most common (≥10%) grade 2/4 include pneumonia 20% (Id treated NFKB2 FISH negative), thrombocytopenia 16% (Id NFKB2 FISH positive), neutropenia 60% (IRd NFKB2 FISH positive. Treatment discontinuations only occurred in 1 Id treated patient (5%).Conclusion: Interim analysis demonstrate a trend higher efficacy of ixazomib with dexamethasone in MM patients with negative NFKB2 break-apart FISH compared to those with a positive test. Efficacy and toxicity of the triplet regimen are comparable to what is seen in Tourmaline 1 trial. This study was registered at www.clinicaltrials.gov as # NCT02765854. DisclosuresBernal-Mizrachi:Takeda Pharmaceutical Company: Research Funding; Kodikaz Therapeutic Solutions: Consultancy, Equity Ownership. Cole:Cancer Support Community myeloma advisory board: Membership on an entity's Board of Directors or advisory committees; University of Michigan: Employment. Heffner:ADC Therapeutics: Research Funding; Kite Pharmaceuticals: Research Funding; Pharmacyclics: Research Funding; Genentech: Research Funding. Nooka:GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Spectrum Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Adaptive technologies: Consultancy, Membership on an entity's Board of Directors or advisory committees. Vij:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jansson: Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharma: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Kelkar:Empire Genomics: Employment. Lonial:Amgen: Research Funding. Kaufman:Karyopharm: Other: data monitoring committee; Abbvie: Consultancy; Roche: Consultancy; BMS: Consultancy; Janssen: Consultancy.

CD38low Natural Killer Cells Transiently Expressing CD16F158V m-RNA Potentiates the Therapeutic Activity of Daratumumab Against Multiple Myeloma with Minimal Effector NK Cell Fratricide

Introduction: Multiple Myeloma (MM) is a clonal plasma cell malignancy typically associated with the high and uniform expression of CD38 transmembrane glycoprotein. Daratumumab is a humanized IgG1κ CD38 monoclonal antibody (moAb) which has demonstrated impressive single agent activity even in relapsed refractory MM patients as well as strong synergy with other anti-MM drugs. Natural Killer (NK) cells are cytotoxic immune effector cells mediating tumour immunosurveillance in vivo. NK cells also play an important role during moAb therapy by inducing antibody dependent cellular cytotoxicity (ADCC) via their Fcγ RIII (CD16) receptor. Furthermore, 15% of the population express a naturally occurring high affinity variant of CD16 harbouring a single point polymorphism (F158V), and this variant has been linked to improved ADCC. However, the contribution of NK cells to the efficacy of Daratumumab remains debatable as clinical data clearly indicate rapid depletion of CD38high peripheral blood NK cells in patients upon Daratumumab administration. Therefore, we hypothesize that transiently expressing the CD16F158V receptor using a “safe” mRNA electroporation-based approach, on CD38low NK cells could significantly enhance therapeutic efficacy of Daratumumab in MM patients. In the present study, we investigate the optimal NK cell platform for generating CD38low CD16F158V NK cells which can be administered as an “off-the-shelf”cell therapy product to target both CD38high and CD38low expressing MM patients in combination with Daratumumab.Methods: MM cell lines (n=5) (MM.1S, RPMI-8226, JJN3, H929, and U266) and NK cells (n=3) (primary expanded, NK-92, and KHYG1) were immunophenotyped for CD38 expression. CD16F158V coding m-RNA transcripts were synthesized using in-vitro transcription (IVT). CD16F158V expression was determined by flow cytometry over a period of 120 hours (n=5). 24-hours post electroporation, CD16F158V expressing KHYG1 cells were co-cultured with MM cell lines (n=4; RPMI-8226, JJN3, H929, and U266) either alone or in combination with Daratumumab in a 14-hour assay. Daratumumab induced NK cell fratricide and cytokine production (IFN-γ and TNF-α) were investigated at an E:T ratio of 1:1 in a 14-hour assay (n=3). CD38+CD138+ primary MM cells from newly diagnosed or relapsed-refractory MM patients were isolated by positive selection (n=5), and co-cultured with mock electroporated or CD16F158V m-RNA electroporated KHYG1 cells. CD16F158V KHYG1 were also co-cultured with primary MM cells from Daratumumab relapsed-refractory (RR) patients.Results: MM cell lines were classified as CD38hi (RPMI-8226, H929), and CD38lo (JJN3, U266) based on immunophenotyping (n=4). KHYG1 NK cell line had significantly lower CD38 expression as compared to primary expanded NK cells and NK-92 cell line (Figure 1a). KHYG1 electroporated with CD16F158V m-RNA expressed CD16 over a period of 120-hours post-transfection (n=5) (Figure 1b). CD16F158V KHYG1 in-combination with Daratumumab were significantly more cytotoxic towards both CD38hi and CD38lo MM cell lines as compared to CD16F158V KHYG1 alone at multiple E:T ratios (n=4) (Figure 1c, 1d). More importantly, Daratumumab had no significant effect on the viability of CD38low CD16F158V KHYG1. Moreover, CD16F158V KHYG1 in combination with Daratumumab produced significantly higher levels of IFN-γ (p=0.01) upon co-culture with CD38hi H929 cell line as compared to co-culture with mock KHYG1 and Daratumumab. The combination of CD16F158V KHYG1 with Daratumumab was also significantly more cytotoxic to primary MM cell ex vivo as compared to mock KHYG1 with Daratumumab at E:T ratio of 0.5:1 (p=0.01), 1:1 (p=0.005), 2.5:1 (p=0.003) and 5:1 (p=0.004) (Figure 1e). Preliminary data (n=2) also suggests that CD16F158V expressing KHYG1 can eliminate 15-17% of primary MM cells from Daratumumab RR patients ex vivo. Analysis of more Daratumumab RR samples are currently ongoing.Conclusions: Our study provides the proof-of-concept for combination therapy of Daratumumab with “off-the-shelf” CD38low NK cells transiently expressing CD16F158V for treatment of MM. Notably, this approach was effective against MM cell lines even with low CD38 expression (JJN3) and primary MM cells cultured ex vivo. Moreover, the enhanced cytokine production by CD16F158V KHYG1 cells has the potential to improve immunosurveillance and stimulate adaptive immune responses in vivo. [Display omitted] DisclosuresSarkar:Onkimmune: Research Funding. Chauhan:Onkimmune: Research Funding. Stikvoort:Onkimmune: Research Funding. Mutis:Genmab: Research Funding; OnkImmune: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Research Funding; Celgene: Research Funding; Novartis: Research Funding. O'Dwyer:Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; BMS: Research Funding; Glycomimetics: Research Funding; Onkimmune: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Update on Clinical Safety and Efficacy of the Novel Oral Dual RAF/MEK Inhibitor RO5126766 (CH5127566) in RAS-mutant Multiple Myeloma

Update on Clinical Safety and Efficacy of the Novel Oral Dual RAF/MEK Inhibitor RO5126766 (CH5127566) in RAS-mutant Multiple Myeloma

Promises and Pitfalls in the Use of PD-1/PD-L1 Inhibitors in Multiple Myeloma.

In the biology of multiple myeloma (MM), immune dysregulation has emerged as a critical component for novel therapeutic strategies. This dysfunction is due to a reduced antigen presentation, a reduced effector cell ability and a loss of reactive T cells against myeloma, together with a bone marrow microenvironment that favors immune escape. The Programmed Death-1 (PD-1) pathway is associated with the regulation of T cell activation and with the apoptotic pathways of effector memory T cells. Specifically, the binding with PD-1 ligand (PD-L1) on the surface of tumor plasma cells down-regulates T cell-proliferation, thus contributing to the immune escape of tumor cells. In relapsed and/or refractory MM (RRMM) patients, PD-1/PD-L1 blockade was analyzed by using nivolumab, pembrolizumab, and durvalumab. Outcomes with single agents were unsatisfactory, whereas combination strategies with backbone immunomodulatory drugs (IMiDs) suggested a synergistic action in such a complex immunological landscape, even in patients previously refractory to these drugs. Nevertheless, these combinations were also associated with an increased incidence of adverse events. This review aims to analyze the available preclinical and clinical data on the role of PD-1/PD-L1 inhibitors in MM therapy, focusing on available preliminary efficacy and safety data and offering insights for future investigation.