Nicotinamide-Expanded Allogeneic Natural Killer Cells with CD38 Deletion, Expressing an Enhanced CD38 Chimeric Antigen Receptor, Target Multiple Myeloma Cells

Natural killer (NK) cells are a vital component of cancer immune surveillance. They provide a rapid and potent immune response, including direct cytotoxicity and mobilization of the immune system, without the need for antigen processing and presentation. NK cells may also be better tolerated than T cell therapy approaches and are susceptible to various gene manipulations. Therefore, NK cells have become the focus of extensive translational research. Gamida Cell's nicotinamide (NAM) platform for cultured NK cells provides an opportunity to enhance the therapeutic potential of NK cells. CD38 is an ectoenzyme ubiquitously expressed on the surface of various hematologic cells, including multiple myeloma (MM). It has been selected as a lead target for numerous monoclonal therapeutic antibodies against MM. Monoclonal antibodies target CD38, resulting in the lysis of MM plasma cells through various antibody-mediated mechanisms such as antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis, significantly improving the outcomes of patients with relapsed or refractory MM. However, this therapeutic strategy has inherent limitations, such as the anti-CD38-induced depletion of CD38-expressing NK cells, thus hindering ADCC. We have developed genetically engineered NK cells tailored to treat MM, in which CD38 was knocked-out using CRISPR-Cas9 technology and an enhanced chimeric antigen receptor (CAR) targeting CD38 was introduced using mRNA electroporation. This combined genetic approach allows for an improved cytotoxic activity directed against CD38-expressing MM cells without self-inflicted NK-cell-mediated fratricide. Preliminary results show near-complete abolition of fratricide with a 24-fold reduction in self-lysis from 19% in mock-transfected and untreated NK cells to 0.8% of self-lysis in CD38 knock-out CAR NK cells. Furthermore, we have observed significant enhancements in CD38-mediated activity in vitro, resulting in increased lysis of MM target cell lines. CD38 knock-out CAR NK cells also demonstrated significantly higher levels of NK activation markers in co-cultures with both untreated and αCD38-treated MM cell lines. These NAM-cultured NK cells with the combined genetic approach of CD38 knockout and addition of CD38 CAR represent a promising immunotherapeutic tool to target MM.

Transcriptome Analysis of Diffuse Large B-Cell Lymphoma Cells Inducibly Expressing MyD88 L265P Mutation Identifies Upregulated CD44, LGALS3, NFKBIZ, and BATF as Downstream Targets of Oncogenic NF-κB Signaling

During innate immune responses, myeloid differentiation primary response 88 (MyD88) functions as a critical signaling adaptor protein integrating stimuli from toll-like receptors (TLR) and the interleukin-1 receptor (IL-1R) family and translates them into specific cellular outcomes. In B cells, somatic mutations in MyD88 trigger oncogenic NF-κB signaling independent of receptor stimulation, which leads to the development of B-cell malignancies. However, the exact molecular mechanisms and downstream signaling targets remain unresolved. We established an inducible system to introduce MyD88 to lymphoma cell lines and performed transcriptomic analysis (RNA-seq) to identify genes differentially expressed by MyD88 bearing the L265P oncogenic mutation. We show that MyD88L265P activates NF-κB signaling and upregulates genes that might contribute to lymphomagenesis, including CD44, LGALS3 (coding Galectin-3), NFKBIZ (coding IkBƺ), and BATF. Moreover, we demonstrate that CD44 can serve as a marker of the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) and that CD44 expression is correlated with overall survival in DLBCL patients. Our results shed new light on the downstream outcomes of MyD88L265P oncogenic signaling that might be involved in cellular transformation and provide novel therapeutical targets.

Report of consensus panel 7 from the 11th international workshop on Waldenström macroglobulinemia on priorities for novel clinical trials

Recent advances in the understanding of Waldenström macroglobulinemia (WM) biology have impacted the development of effective novel agents and improved our knowledge of how the genomic background of WM may influence selection of therapy. Consensus Panel 7 (CP7) of the 11th International Workshop on WM was convened to examine the current generation of completed and ongoing clinical trials involving novel agents, consider updated data on WM genomics, and make recommendations on the design and prioritization of future clinical trials. CP7 considers limited duration and novel-novel agent combinations to be the priority for the next generation of clinical trials. Evaluation of MYD88, CXCR4 and TP53 at baseline in the context of clinical trials is crucial. The common chemoimmunotherapy backbones, bendamustine-rituximab (BR) and dexamethasone, rituximab and cyclophosphamide (DRC), may be considered standard-of-care for the frontline comparative studies. Key unanswered questions include the definition of frailty in WM; the importance of attaining a very good partial response or better (≥VGPR), within stipulated time frame, in determining survival outcomes; and the optimal treatment of WM populations with special needs.

Promises and Challenges of Immunogenic Chemotherapy in Multiple Myeloma

Immunological tolerance of myeloma cells represents a critical obstacle in achieving long-term disease-free survival for multiple myeloma (MM) patients. Over the past two decades, remarkable preclinical efforts to understand MM biology have led to the clinical approval of several targeted and immunotherapeutic agents. Among them, it is now clear that chemotherapy can also make cancer cells “visible” to the immune system and thus reactivate anti-tumor immunity. This knowledge represents an important resource in the treatment paradigm of MM, whereas immune dysfunction constitutes a clear obstacle to the cure of the disease. In this review, we highlight the importance of defining the immunological effects of chemotherapy in MM with the goal of enhancing the clinical management of patients. This area of investigation will open new avenues of research to identify novel immunogenic anti-MM agents and inform the optimal integration of chemotherapy with immunotherapy.

Abstract 5352: Genome-wide CRISPR-cas9 screening identifies KDM6A as a modulator of CD38 expression in multiple myeloma: Therapeutic implications

Daratumumab (Dara) is the first-in-class monoclonal antibody targeting CD38 which triggers both direct and immune mediated cytotoxicity in preclinical in vitro and in vivo models of multiple myeloma (MM) in the bone marrow (BM) milieu. Importantly, Dara combination therapies can achieve high frequency and extent of response in both relapsed/refractory and newly diagnosed MM. However, relapse of MM is commonly observed due, at least in part, to downregulation of CD38 on MM cells. Here we utilize genome-wide CRISPR-cas9 knockout (KO) screening to identify novel regulators mediating CD38 expression and Dara sensitivity in MM cells. We identified 46 different sgRNAs to be positively correlated with MM cytotoxicity triggered by Dara and NK cells treatment. We further performed second round screening using the cell population with lowest 5% CD38 expression after CRISPR lentiviral library transduction. Importantly, KDM6A was the top ranked of the overlapping genes from these two screenings. Next, we individually KO of KDM6A in MM cells and found that both mRNA and protein levels of CD38 were significantly decreased, as well as the cell surface CD38 expression detected by flow cytometry. Re-introduction of KDM6A into KDM6A KO cells restored the expression level of CD38 and Dara-induced cytotoxicity, indicating that KDM6A positively regulates CD38 expression in MM cells. Since KDM6A regulates demethylation of lysine 27 at histone H3 (H3K27) to activate gene expression, we next examined whether CD38 expression was altered by methylation status of H3K27. From our ChIP-seq and ChIP Q-PCR data, we identified that H3K27me3 level was highly enriched on the promotor area of CD38 in KDM6A KO cells compared to control cells. These data indicate that KDM6A modulates CD38 expression by regulating H3K27me3 level on the CD38 promotor, thereby mediating sensitivity of MM cells to Dara-induced cytotoxicity. H3K27me3 is regulated by the balance of demethylase (KDM6A) and methyltransferase (EZH2). However, downregulating H3K27me3 on the CD38 promoter by enhancing KDM6A activity is challenging. Therefore, we next explored whether EZH2 inhibitor can restore CD38 expression and overcome Dara resistance in KDM6A KO cells. Indeed, H3K27me3 level on the CD38 promotor area was significantly decreased by EZH2 inhibitor. Moreover, EZH2 inhibitor treatment upregulated both CD38 mRNA and protein levels in KDM6A KO cells. Importantly, EZH2 inhibitor also restored sensitivity of KDM6A KO cells to Dara-mediated NK cell cytotoxicity. Taken together, our studies demonstrate that KDM6A regulates H3K27me3 level on CD38 promotor area and CD38 expression in MM. Moreover, we validate that combination treatment with EZH2 inhibitor and Dara can overcome Dara resistance in preclinical MM models, providing the rationale for combination clinical trials to overcome Dara resistance and improve patient outcome.

Citation Format: Jiye Liu, Lijie Xing, Teru Hideshima, Kenneth Carl Anderson. Genome-wide CRISPR-cas9 screening identifies KDM6A as a modulator of CD38 expression in multiple myeloma: Therapeutic implications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5352.

Lenalidomide, bortezomib, and dexamethasone (RVd) ± autologous stem cell transplantation (ASCT) and R maintenance to progression for newly diagnosed multiple myeloma (NDMM): The phase 3 DETERMINATION trial

LBA4

Background: Optimal use of triplet/quadruplet induction, ASCT, and R-based maintenance in patients (pts) with NDMM who are eligible for transplant continues to evolve. The IFM 2009 trial, which used R maintenance for 1 year (y), showed progression-free survival (PFS; median, 35.0 vs. 47.3 months [mos]) but no overall survival benefit (OS; 60 vs. 62% at 8 y; median follow-up, 89.8 mos) with RVd + ASCT vs. RVd alone in the setting of multiple effective options at relapse, including ASCT at first relapse in 77% of pts (Attal M et al, N Engl J Med 2017; Perrot A et al, ASH 2020). We report primary data from our US DETERMINATION trial, which used R maintenance until progression. Methods: Pts with NDMM aged 18-65 y were randomly assigned to receive 3 RVd cycles, stem cell mobilization, and then 5 more RVd cycles (Arm A) or IV melphalan 200 mg/m2 + ASCT and 2 RVd cycles (Arm B). Each 21-d RVd cycle comprised PO R 25 mg (d 1-14), IV/SC bortezomib 1.3 mg/m2 (d 1, 4, 8, 11), and PO dexamethasone 20/10 mg (cycles 1-3/≥ 4; d 1, 2, 4, 5, 8, 9, 11, 12). Both arms received R 10-15 mg/d maintenance until progression or intolerance. The primary endpoint was PFS (90% power to detect PFS hazard ratio [HR] of 1.43 [Arm A vs. B] with α = 0.05 on stratified two-sided log-rank test; full information: 329 events in 720 pts). Data cut-off was Dec 10, 2021. Results: 357 and 365 pts were randomly assigned to Arms A and B, respectively; median age was 57 and 55 y, 14% and 13% had ISS stage III MM, and 18% each had high-risk cytogenetics [t(4;14), t(14;16), del17p]. In the respective arms, 291 and 290 pts received R maintenance for a median duration of 36 and 41 mos. After median follow-up of 76 mos and 328 events, median PFS was 46.2 vs. 67.6 mos in Arm A vs. B (HR 1.53; 95% CI, 1.23–1.91; p < .0001). Best responses in pts assessed to date were 52 vs. 62% ≥ CR (p = .006), 79 vs. 83% ≥ VGPR and 94 vs. 96% ≥ PR; in 251 evaluable pts, rate of MRD negativity (10-5) was 37.3 vs. 52.1% (p = .021) within 1 y of maintenance. 63 vs. 53% of pts have received subsequent treatment; of Arm A, 22% had ASCT as first non-protocol therapy. With 90 vs. 88 pts having died in Arm A vs. B, 4-y OS was 84% (95% CI, 80–88%) vs. 85% (95% CI, 81–88%); HR 1.10 (95% CI, 0.81–1.47; p = .274). Grade ≥ 3 related adverse events were less common in Arm A vs. B (78 vs. 94%; hematologic: 61 vs. 90%, p < .0001); 10 vs. 11% had secondary malignancies (ALL, 7 vs. 3 pts, p = .22; AML/MDS, 0 vs. 10 pts, p = .002). Difference in mean change from baseline in EORTC QLQ-C30 global health status score was < 10 points throughout treatment except at RVd cycle 5 vs. post-ASCT (compliance rate, 75% vs. 55%; mean change +3.0 vs. –11.1; p < .0001). Whole-genome sequencing, additional QOL, and correlative analyses are ongoing. Conclusions: RVd ± ASCT and R maintenance to progression resulted in the longest median PFS reported for each approach, and a highly significant 21.4-mo gain in median PFS benefit using RVd + ASCT. No OS advantage has been observed to date. Clinical trial information: NCT01208662.

Development of B-cell maturation antigen (BCMA)-specific CD8+ cytotoxic T lymphocytes using induced pluripotent stem cell technology for multiple myeloma

2542

Background: A strategy for reversal of T cell exhaustion is reprograming of antigen-specific CTL to early lineage memory T cells with selective anti-tumor activities. To accomplish this goal, we epigenetically reprogrammed BCMA-specific CD8+ CTL to a pluripotent state through key defined transcription factors, established “induced Pluripotent Stem Cells (iPSC)” exhibiting transcriptional and epigenetic features, re-differentiated them back into antigen-specific CTL and evaluated their properties and functional activities against multiple myeloma (MM). Methods: Functionally activeIFN-g producing HLA-A2 heteroclitic BCMA72-80 (YLMFLLRKI)-specific CD8+ CTL were applied for iPSC via transduction of four reprogramming factors (OCT3/4, SOX2, KLF4, c-MYC). Upon characterization of the BCMA-specific iPSC with high pluripotency potential, embryoid body was formed from the iPSC and further polarized into mesoderm layer development as evidenced by upregulation of transcriptional regulators (ABCA4, BMP10, CDH5, FOXF1, HAND1, PLVAP, SNAI2, TBX3). Next, BCMA-specific embryoid body-derived hematopoietic progenitor cells (HPC; CD34+ CD43+/CD14- CD235a-) were sorted and induced to undergo T cell differentiation in the presence of Fc-DLL4 signaling and rectonectin. Results: Our RNAseq analyses demonstrated unique transcriptional profiles of HPC from different iPSC clones committing to CD8+ T cells or other cell lineages (monocytes/granulocytes, B lymphocytes/NK cells). Principal component analyses demonstrated a high similarity and low variability of transcription profiles within the replicates of HPC committed to the same cell lineage. In addition, distinct genome-wide shifts and differential gene expression profiles were detected in HPC committed to each specific cell differentiation pathway. Specifically, the HPC commit to CD8+ T cells utilized a diverse repertoire of modulators promoting development of T cell maturation, specific immune response regulation, memory T cells, cytotoxicity and interferon induction, which were significantly higher than shown in HPC that differentiate to other cell lineages. In parallel, specific repression genes were identified in the HPC commit to CD8+ T cells, which develop TGF-β receptor, rearrangement of Ig heavy chain genes and inhibitory receptors. The T cells differentiated were mainly CD45RO+ memory CTL and fully rejuvenated without immune checkpoints expression and regulatory T cells and with high anti-MM activities. Conclusions: These findings identify genetic and epigenetic mechanisms and regulatory elements, which play key roles during lineage specific commitment of HPC developed in iPSC into CD8+ CTL and help to further design a next generation of regenerative medicine that provide the appropriate signals for T cell lineage commitment from progenitor cells.

Updates from ICARIA-MM, a phase 3 study of isatuximab (Isa) plus pomalidomide and low-dose dexamethasone (Pd) versus Pd in relapsed and refractory multiple myeloma (RRMM)

8017

Background: Isa is an approved monoclonal antibody that binds to a specific epitope on the CD38 receptor. The Phase 3 ICARIA-MM study (NCT02990338) demonstrated significantly improved progression-free survival (PFS) with Isa-Pd vs Pd ( P= 0.001) and a manageable safety profile (Attal M, et al. Lancet 2019;394:2096-2107). Here we report updated ICARIA results. Methods: Pts with RRMM (N = 307) who have received ≥2 prior therapies, including lenalidomide (Len) and a proteasome inhibitor (PI), were randomized to Isa-Pd (n = 154) or Pd (n = 153). Isa was administered intravenously at 10 mg/kg weekly for 4 weeks, and every other week thereafter. This preplanned second interim analysis assessed longer term outcomes, including time to next treatment (TTNT), overall survival (OS), time from randomization to disease progression on first subsequent therapy or death (PFS2), and safety. Results: Pts had a median of 3 prior lines of therapy (IQR 2–4; table). As of Oct 1, 2020 (median follow-up, 35.3 months [mo]), 27 Isa-Pd pts (18%) vs 12 Pd pts (8%) were still on treatment; 60% vs 72% had proceeded to subsequent therapy. Median TTNT was 15.5 mo with Isa-Pd vs 8.9 mo with Pd (hazard ratio [HR] 0.56; 95% confidence interval [CI] 0.42–0.74; P< 0.0001); 24% vs 58% of pts with subsequent therapy received daratumumab (dara). Overall response rate (ORR) in subsequent treatment with dara monotherapy was higher after Pd (38%) than Isa-Pd (14%), but was similar (32% vs 31%) with dara combination therapy (table). Median PFS2 in the intent-to-treat population was 17.5 mo with Isa-Pd vs 12.9 mo with Pd (HR 0.76; 95% CI 0.58–0.99; P= 0.0202). Median OS was 24.6 mo with Isa-Pd vs 17.7 mo with Pd (HR 0.76; 95% CI 0.58–1.01; one-sided P= 0.0280). Median treatment duration was 47.6 weeks (range 1.3–171.6) with Isa-Pd vs 24.0 weeks (range 1.0–168.6) with Pd. Serious treatment-emergent adverse event (TEAEs) were seen in 73% of Isa-Pd pts vs 60% of Pd pts. Most frequent non-hematologic TEAEs (any grade) with Isa-Pd were infusion reaction (38%), upper respiratory tract infection (34%), and diarrhea (30%). Grade 3–4 neutropenia (85% vs 71%) and thrombocytopenia (34% vs 25%) were more frequent with Isa-Pd than with Pd. Conclusions: Isa-Pd demonstrates a significant improvement in TTNT and PFS2 compared with Pd. A strong trend in OS benefit was also seen in the Isa-Pd arm, with approximately 7 mo improvement in median OS. The overall safety profile remains unchanged from prior analyses. Funding: Sanofi. Clinical trial information: NCT02990338. [Table: see text]

Perceptions of prognosis in caregivers of multiple myeloma (MM) patients

12082

Background: Caregivers of patients with cancer play a critical role in supporting patients when making informed decisions about their medical care. Although MM patients and their caregivers face an incurable illness, data describing caregiver perceptions of the patient’s prognosis and factors associated with accurate prognostic perceptions are lacking. Methods: We conducted a cross-sectional, multisite study of caregivers of MM patients between 6/2020-1/2021. Eligible caregivers were identified by the patient as the primary caregiver and enrolled in 1 of 3 cohorts based on lines of therapy: 1) caregivers of newly diagnosed patients receiving first-line therapy; 2) 2-3 lines; 3) ≥4 lines. Caregivers completed the Perception of Treatment and Prognosis Questionnaire to assess their perceptions of the illness and prognosis. We also used the CareGiver Oncology Quality of Life (QOL) questionnaire, the Hospital Anxiety and Depression Scale, the Post-Traumatic Stress Disorder Checklist–Civilian Version, and the Brief COPE to assess caregiver QOL, psychological distress, and coping strategies. We used a multivariate logistic regression analysis to examine whether caregiver factors (i.e. demographics), line of therapy, QOL, psychological distress, or coping were associated with caregiver perceptions of the patient’s prognosis. Results: We enrolled 113 caregivers of MM patients (newly diagnosed (n=39), 2-3 lines (n=37), and ≥ 4 lines (n=37)). Overall, 89.2% (99/111) of caregivers reported that it is ‘extremely’ or ‘very’ important to know about the patient’s prognosis and the majority (58.0%, 65/112) stated that they had received adequate information regarding the patient’s prognosis. Caregivers reported that prognostic information was ‘extremely’ or ‘very’ helpful in making decisions about treatment (93.3%, 97/104), preparing for the future (88.2%, 90/102), and coping with the disease (85.6%, 89/104). Most caregivers (84.7%, 94/111) reported that the oncologist told them the patient’s cancer was incurable. In contrast, only 53.6% (59/110) of caregivers reported that they thought the patient’s cancer was incurable and 48.6% (52/107) acknowledged that the patient is terminally ill. In a multivariate analysis, we found that the use of positive reframing coping (OR=0.71, 95%CI=0.52-0.97, P=0.033) was associated with lower odds of reporting an accurate perception of prognosis. Caregiver demographics, line of therapy, QOL, and psychological distress were not associated with their perceptions of the patient’s prognosis. Conclusions: Although the majority of caregivers of MM patients report that knowing the patient’s prognosis is extremely important, a substantial minority still have significant misperceptions of the patient’s prognosis. Interventions are needed to promote effective coping and enhance caregiver perceptions of the patient’s prognosis to facilitate informed decision-making in this population.

Harnessing the Immune System Against Multiple Myeloma: Challenges and Opportunities

Multiple myeloma (MM) is an incurable malignancy of plasma cells that grow within a permissive bone marrow microenvironment (BMM). The bone marrow milieu supports the malignant transformation both by promoting uncontrolled proliferation and resistance to cell death in MM cells, and by hampering the immune response against the tumor clone. Hence, it is expected that restoring host anti-MM immunity may provide therapeutic benefit for MM patients. Already several immunotherapeutic approaches have shown promising results in the clinical setting. In this review, we outline recent findings demonstrating the potential advantages of targeting the immunosuppressive bone marrow niche to restore effective anti-MM immunity. We discuss different approaches aiming to boost the effector function of T cells and/or exploit innate or adaptive immunity, and highlight novel therapeutic opportunities to increase the immunogenicity of the MM clone. We also discuss the main challenges that hamper the efficacy of immune-based approaches, including intrinsic resistance of MM cells to activated immune-effectors, as well as the protective role of the immune-suppressive and inflammatory bone marrow milieu. Targeting mechanisms to convert the immunologically “cold” to “hot” MM BMM may induce durable immune responses, which in turn may result in long-lasting clinical benefit, even in patient subgroups with high-risk features and poor survival.

Biological correlates to support a clinical role for tagraxofusp, a novel targeted therapy directed to CD123, in combination with pomalidomide and dexamethasone, to target plasmacytoid dendritic cells in poor-risk patients with multiple myeloma

e20537

Background: We have previously described the pivotal pathogenetic role of plasmacytoid dendritic cells (pDCs; CD123/IL-3Ra+) in multiple myeloma (MM) (Chauhan et al Cancer Cell, 2009,16:309). In preclinical MM models, we demonstrated that tagraxofusp, a novel targeted therapy directed to CD123, triggers anti-MM activity by reducing the viability of MM-promoting pDCs. These observations led to an ongoing phase 1/2 clinical trial of tagraxofusp in MM patients (NCT02661022). The treatment regimen demonstrated safety and efficacy, with 5 of 9 heavily pretreated patients achieving durable partial response (PR). Here, we report the initial results of our translational exploratory studies using bone marrow (BM), peripheral blood (PB), and serum from the study cohort. Methods: pDCs and MM tumor cells were purified from BM/PB samples and quantified using FACS, as described ( Ray et al Leukemia, 2018,32:843). A high-throughput seroproteomics platform SOMAscan was utilized to analyze 1,310 protein analytes in serum samples from MM patients (N = 9). SOMAscan data were subjected to meta-analysis to generate heatmaps, followed by hierarchical cluster analysis. SOMAscan results were validated with ELISA using supernatants from MM patient pDCs cultured with or without tagraxofusp. Results: Analysis of BM/PB samples from MM patients receiving tagraxofusp therapy showed a marked reduction in the frequency of viable pDCs [average 2% at screen vs 0.75% post-tagraxofusp; N = 6; p = 0.036]. pDCs isolated from tagraxofusp-treated patients showed decreased ability to trigger MM cell growth. Seroproteomics analysis of MM patient serum before and after tagraxofusp therapy showed alterations in the levels of 100 proteins [Median Fold Change in expression: 0.39 to 4.5; n = 6; 3 each; p < 0.05]. Importantly, we found that tagraxofusp treatment reduced pDC-related soluble proteins, in particular, IFN-a and IL-3Rα. Additionally, our earlier study showed that pDC-MM interactions triggered secretion of MM cell growth including IL-3, which serves a dual role of promoting pDC survival and MM cell growth. Importantly, tagraxofusp decreased serum IL-3, suggesting that tagraxofusp attenuates survival mechanisms for tumor-promoting pDCs. Conclusions: Our current correlative studies validate target specificity of tagraxofusp and support further evaluation for this novel therapeutic to improve the clinical outcome of patients with MM.

Enhanced CD138 peptide-specific cytotoxic T lymphocyte activities against breast, colon and pancreatic cancers in combination with pembrolizumab (anti-PD1)

e14302

Background: We investigated the ability of CD138 antigen-specific CD8+ cytotoxic T lymphocytes (CD138-CTL), generated using a novel HLA-A2-specific CD138260-268 (GLVGLIFAV) peptide, in combination with various immune checkpoint inhibitors, to target breast, colon, and pancreatic cancer. Methods: This study was designed to evaluate anti-tumor activities of CD138-CTL, alone or in combination with Pembrolizumab (anti-PD1), against solid tumors. Results: Upregulation of CD138 protein expression was detected on breast, colon, and pancreatic cancer cells. CD138-CTL induced ex vivo by repeated stimulations with HLA-A2-specific CD138260-268 (GLVGLIFAV) peptide were enriched for CD45RO+ memory CTL and demonstrated antigen-specific and HLA-A2-restricted anti-tumor activities. Treatment of CD138-CTL with anti-PD1, anti-TIM3, or anti-LAG3 or tumor cells with anti-PDL1, anti-Gal9 or anti-LAG3 resulted in an increased proliferation of CD138-specific CD8+ CTL, which express costimulatory and activation markers (CD28, CD40L, 41BB, CD69, CD38). However, expression of immune checkpoints (PD1, LAG3, CTLA4) was also induced on these CD138-CTL upon stimulation. Importantly, anti-tumor activities of CD138 peptide-CTL was significantly enhanced in combination with Pembrolizumab, especially within the antigen-specific memory CD8+ T cell subsets (central memory > effector memory), directed against HLA-A2+ breast cancer, colon cancer and pancreatic cancer. Conclusions: These data provide the framework for an immunotherapeutic strategy encompassing a CD138260-268 (GLVGLIFAV) peptide-based cancer vaccine in combination with Pembrolizumab to enhance antigen-specific central memory cells with more potent and long-lasting CD8+ CTL immune responses in patients with solid tumors. Based on these result, clinical trials evaluating CD138260-268 (GLVGLIFAV) in multi-peptide cancer vaccine are on-going in patients with triple negative breast cancer in combination with anti-PD1 (Pembrolizumab) in metastatic setting (NCT 03362060) or anti-PD-L1 (Durvalumab) in stage II/III, adjuvant setting (NCT 02826434).

The myeloma-developing regimens using genomics (MyDRUG) master protocol

TPS8057

Background: Multiple myeloma (MM) is the second most prevalent blood cancer, representing approximately 1% of all cancers. Although overall survival has improved in recent years due to new approved agents, the vast majority of MM patients (pts) ultimately stop responding to treatment. Moreover, about a quarter of MM pts characterized as “high risk” experience limited benefit from existing treatments. Seminal genomic sequencing research efforts, such as the MMRF CoMMpass study, have highlighted that a large number of MM cases harbor potentially actionable oncogenic molecular alterations and published reports on small numbers of cases suggest that Precision Medicine (PM) interventions clinically targeting such actionable drivers may benefit MM pts. These results suggest that PM approaches in MM are possible and should be further studied clinically. To that end, we have launched MyDRUG, a master protocol aimed at developing new myeloma regimens based on individual pt’s genomics. Methods: This study is a Phase I-II, multicenter master protocol in functional high risk MM patients (i.e patients having progressed from baseline treatment within 18 months without maintenance or 3 years on maintenance) with 1-3 prior lines of therapy. Patients are screened for actionable genomic alterations on the CLIA-grade MI-ONCOSEQ platform. Patients with actionable alterations are assigned to the appropriate targeted agent used in combination with a backbone regimen ixazomib, pomalidomide and dexamethasone (IPd), whereas patients without such alterations go on an immune arm (see Table). Inclusion criteria include measurable disease (as measured by M-protein and FLC) and acceptable hematologic and metabolic functions. A maximum of 12 evaluable pts will be accrued onto the phase I portion of each arm and an additional 21 evaluable phase II pts will be accrued onto each arm for a total of 27 evaluable pts at the MTD combination dose. The primary objective of the study is to evaluate ORR per IMWG consensus criteria. Secondary objectives are to assess adverse events (AEs), progression-free survival, and overall survival (OS). Experimental correlative aims include assessing molecular or clonal response, molecular and immune signatures of resistance/response, MRD. Clinical trial information: NCT03732703. [Table: see text]

A phase III randomized, open label, multicenter study comparing isatuximab, pomalidomide, and low-dose dexamethasone versus pomalidomide and low-dose dexamethasone in patients with relapsed/refractory multiple myeloma (RRMM)

8004

Background: The primary objective of this phase 3 trial was to demonstrate progression free survival (PFS) improvement of isatuximab (Isa), a novel anti-CD38 monoclonal antibody, combined with pomalidomide (P)/dexamethasone (d) versus (vs) Pd. Methods: Patients (pts) with RRMM who received ≥2 prior lines, including lenalidomide (len) and a proteasome inhibitor (PI), refractory to last therapy were enrolled. IsaPd arm received Isa 10 mg/kg IV weekly for first 4 weeks (wks), then every 2 wks. Both arms received approved schedules of pom and dex (4mg PO days 1-21; 40mg [20mg if >75 yrs] PO or IV weekly) every 28 days until progression or unacceptable toxicity. Results: 307 pts (154 IsaPd, 153 Pd) were randomized and analyzed (ITT). Patient characteristics were well balanced across arms. Median age: 67 (36-86) yrs; median prior lines of therapy: 3 (2-11); estimated GFR: <60ml/min in 33.9% pts; 92.5% refractory to len, 75.9% to PI; and 19.5% pts had high-risk cytogenetics. At median follow-up of 11.6 months (mos), median PFS was 11.5 mos IsaPd vs 6.5 mos Pd; HR 0.596 (95% CI 0.44-0.81), P=0.001. PFS benefit was consistent across all major subgroups. ORR (≥PR) was 60.4% IsaPd vs 35.3% Pd, P<0.0001. VGPR rate or better was 31.8% IsaPd vs 8.5% Pd, and MRD negativity (NGS, 10-5) was seen in 5.2% IsaPd pts vs 0% Pd. At analysis date, overall survival (OS) was immature (99 events) but a trend to OS improvement in IsaPd (vs Pd) was observed (HR 0.687; 95% CI 0.461-1.023). Median treatment duration was 41 wks IsaPd vs 24 wks Pd; median Isa infusion (inf.) duration was 3.3h at 1st inf. and 2.8h at subsequent inf. Grade ≥3 AEs were observed in 86.8% IsaPd vs 70.5% Pd; 7.2% IsaPd and 12.8% Pd pts discontinued due to AEs; 7.9% IsaPd and 9.4% Pd pts died due to AEs. Inf. reactions were reported in 38.2% (2.6% grade 3-4) IsaPd. Grade ≥3 infections were seen in 42.8% IsaPd and 30.2% Pd, grade ≥3 neutropenia in 84.9% (febrile 11.8%) IsaPd and 70.1% (febrile 2.0%) Pd. Conclusions: IsaPd significantly improved PFS and ORR vs Pd, with a manageable safety profile. IsaPd is an important new treatment option for the management of RRMM. Clinical trial information: NCT02990338.

Protein arginine methyltransferase 5 has prognostic relevance and is a druggable target in multiple myeloma

Arginine methyltransferases critically regulate cellular homeostasis by modulating the functional outcome of their substrates. The protein arginine methyltransferase 5 (PRMT5) is an enzyme involved in growth and survival pathways promoting tumorigenesis. However, little is known about the biologic function of PRMT5 and its therapeutic potential in multiple myeloma (MM). In the present study, we identified and validated PRMT5 as a new therapeutic target in MM. PRMT5 is overexpressed in patient MM cells and associated with decreased progression-free survival and overall survival. Either genetic knockdown or pharmacological inhibition of PRMT5 with the inhibitor EPZ015666 significantly inhibited growth of both cell lines and patient MM cells. Furthermore, PRMT5 inhibition abrogated NF-κB signaling. Interestingly, mass spectrometry identified a tripartite motif-containing protein 21 TRIM21 as a new PRMT5-partner, and we delineated a TRIM21-dependent mechanism of NF-κB inhibition. Importantly, oral administration of EPZ015666 significantly decreased MM growth in a humanized murine model of MM. These data both demonstrate the oncogenic role and prognostic relevance of PRMT5 in MM pathogenesis, and provide the rationale for novel therapies targeting PRMT5 to improve patient outcome.

Management of relapsed and refractory multiple myeloma: novel agents, antibodies, immunotherapies and beyond

Despite enormous advances, management of multiple myeloma (MM) remains challenging. Multiple factors impact the decision to treat or which regimen to use at MM relapse/progression. Recent major randomized controlled trials (RCTs) showed widely varying progression-free survivals (PFS), ranging from a median of 4 months (MM-003) to 23.6 months (ASPIRE). Based on these RCTs, next-generation proteasome inhibitors (carfilzomib and ixazomib), next-generation immunomodulatory agent (pomalidomide), and monoclonal antibodies (elotuzumab and daratumumab) were approved for relapsed and refractory MM. Daratumumab, targeting CD38, has multiple mechanisms of action including modulation of the immunosuppressive bone marrow micro-environment. In addition to the remarkable single agent activity in refractory MM, daratumumab produced deep responses and superior PFS in MM when combined with lenalidomide/dexamethasone, or bortezomib/dexamethasone. Other anti-CD38 antibodies, such as isatuximab and MOR202, are undergoing assessment. Elotuzumab, targeting SLAMF7, yielded superior response rates and PFS when combined with lenalidomide/dexamethasone. New combinations of these next generation novel agents and/or antibodies are undergoing clinical trials. Venetoclax, an oral BH3 mimetic inhibiting BCL2, showed single agent activity in MM with t(11;14), and is being studied in combination with bortezomib/dexamethasone. Selinexor, an Exportin-1 inhibitor, yielded promising results in quad- or penta-refractory MM including patients resistant to daratumumab. Pembrolizumab, an anti-PD1 check-point inhibitor, is being tested in combination with lenalidomide/dexamethasone or pomalidomide/dexamethasone. Chimeric antigen receptor-T cells targeting B-cell maturation antigen have yielded deep responses in RRMM. Finally, salvage autologous stem cell transplantation (ASCT) remains an important treatment in MM relapsing/progressing after a first ASCT. Herein, the clinical trial data of these agents are summarized, cautious interpretation of RCTs highlighted, and algorithm for salvage treatment of relapse/refractory MM proposed.

Pomalidomide, bortezomib and low-dose dexamethasone in lenalidomide-refractory and proteasome inhibitor-exposed myeloma

This phase 1 dose-escalation study evaluated pomalidomide, bortezomib (subcutaneous (SC) or intravenous (IV)) and low-dose dexamethasone (LoDEX) in lenalidomide-refractory and proteasome inhibitor-exposed relapsed or relapsed and refractory multiple myeloma (RRMM). In 21-day cycles, patients received pomalidomide (1-4 mg days 1-14), bortezomib (1-1.3 mg/m2 days 1, 4, 8 and 11 for cycles 1-8; days 1 and 8 for cycle ⩾9) and LoDEX. Primary endpoint was to determine the maximum tolerated dose (MTD). Thirty-four patients enrolled: 12 during escalation, 10 in the MTD IV bortezomib cohort and 12 in the MTD SC bortezomib cohort. Patients received a median of 2 prior lines of therapy; 97% bortezomib exposed. With no dose-limiting toxicities, MTD was defined as the maximum planned dose: pomalidomide 4 mg, bortezomib 1.3 mg/m2 and LoDEX. All patients discontinued treatment by data cutoff (2 April 2015). The most common grade 3/4 treatment-emergent adverse events were neutropenia (44%) and thrombocytopenia (26%), which occurred more frequently with IV than SC bortezomib. No grade 3/4 peripheral neuropathy or deep vein thrombosis was reported. Overall response rate was 65%. Median duration of response was 7.4 months. Pomalidomide, bortezomib and LoDEX was well tolerated and effective in lenalidomide-refractory and bortezomib-exposed patients with RRMM.

A novel BCMA/CD3 bispecific T-cell engager for the treatment of multiple myeloma induces selective lysis in vitro and in vivo

This corrects the article DOI: 10.1038/leu.2016.388.

A phase III, randomized, open-label study of isatuximab (SAR650984) plus pomalidomide (Pom) and dexamethasone (Dex) versus Pom and Dex in relapsed/refractory multiple myeloma

TPS8057

Background: Treatment for refractory or relapsed and refractory multiple myeloma (MM) remains an unmet need. Isatuximab (ISA), an anti-CD38 monoclonal antibody with multiple mechanisms of tumor killing, has shown efficacy and an acceptable tolerability profile in Phase 1/2 studies in patients with refractory or relapsed and refractory MM (RRMM) (Richter et al. ASCO 2016; Vij et al. ASCO 2016). Methods: This Phase III, prospective, multicenter, randomized, open-label study (NCT02990338; ICARIA-MM) is being conducted to evaluate the clinical benefit of ISA in combination with Pom and low-dose Dex (Pom/Dex) versus Pom/Dex for the treatment of adult patients with RRMM and demonstrated disease progression within 60 days of the last therapy, and who have received at least 2 prior lines of therapy, including lenalidomide and a proteasome inhibitor (bortezomib, carfilzomib, or ixazomib) alone or in combination. Patients will be randomly assigned in a 1:1 ratio to either ISA (10 mg/kg IV on Days 1, 8, 15, and 22 in the 1st cycle; Days 1 and 15 in subsequent cycles) plus Pom (4 mg on Days 1–21) and Dex (40 mg for patients < 75 years of age and 20 mg for patients ≥75 years of age, on Days 1, 8, 15, and 22) or Pom and Dex. Treatment cycles will be 28 days each. Patients will continue therapy until disease progression, occurrence of unacceptable adverse events (AEs), or their decision to discontinue the study, whichever comes first. The primary endpoint is progression-free survival (PFS), i.e. time from randomization to progressive disease or death from any cause. Response will be determined by IMWG criteria (2016). Key secondary endpoints include overall response rate and overall survival (OS). Safety evaluations include treatment-emergent AEs/serious AEs (including infusion-associated reactions), laboratory parameters, vital signs and assessment of physical examination. Statistical analyses will be conducted according to a pre-specified plan; approximately 300 patients (150 in each arm) are expected to be enrolled in this study. The first patient was recruited in January 2017. Study funding: Sanofi. Clinical trial information: NCT02990338.

Phase 3 ELOQUENT-2 study: Extended four year follow-up (FU) of elotuzumab plus lenalidomide/dexamethasone (ELd) vs Ld in relapsed/refractory multiple myeloma (RRMM)

8028

Background: Elotuzumab, an immunostimulatory monoclonal antibody, has a dual mechanism of action: directly activating NK cells and tagging myeloma cells for recognition/death via antibody-dependent cell-mediated cytotoxicity. In a 3-y FU, ELOQUENT-2 (NCT01239797) showed a sustained 27% reduction in risk of disease progression/death for ELd vs Ld and OS trend in favor of ELd (Dimopoulos et al, ASH 2015). Here we present extended 4-y FU data (median FU 46 mo). Methods: RRMM patients (pts) were randomized 1:1 to ELd or Ld in 28-d cycles until disease progression/unacceptable toxicity. Coprimary endpoints: PFS, ORR. Secondary endpoint: OS. Results: Of 646 RRMM pts, 321 were randomized to ELd, 325 to Ld; ~ twice as many pts remain on therapy in ELd vs Ld (17 vs 9%) at data cut-off (Oct 18, 2016). Discontinuation was mainly due to disease progression (both arms 54%). At 4-y FU, ELd had 29% reduction in risk of progression/death vs Ld (HR 0.71, 95% CI 0.59–0.86) and relative improvement of 50% in PFS (21 vs 14%). Pts with ≥VGPR (ELd 112 [35%], Ld 95 [29%]) had greatest reduction in risk of progression/death (HR 0.65, 95% CI 0.46–0.94). ORR was 79% (ELd) vs 66% (Ld). OS will be presented. G3–4 AEs in ≥5% of pts included second primary malignancies (SPMs), vascular diseases, cardiac disorders and infections (ELd vs Ld: 9 vs 6%, 10 vs 8%, 5 vs 8%, 33 vs 26%). Overall rate (any grade) of infection and SPMs was 84 vs 75% and 17 vs 11% for ELd vs Ld. However, pts had longer exposure to ELd vs Ld (median [Q1, Q3] treatment cycles (19 [9, 42] vs 14 [6, 25]). There were fewer deaths with ELd vs Ld (165 vs 186), mainly due to disease progression and infection in both arms. Conclusions: Elotuzumab in combination with Ld consistently met its efficacy objectives at 4-y FU. ELd showed durable, clinically relevant improvement in PFS, with 29% reduction in risk of progression/death, consistent with 2-y (30%) and 3-y FU (27%). Safety, including rate of SPMs, was consistent with previous findings, with minimal incremental AEs with addition of elotuzumab to Ld. These data represent the longest median FU of an immuno-oncology agent in MM. Study funding: BMS. Writing support: C Tomas, Caudex, funded by BMS. Clinical trial information: NCT01239797.

Function and expression of checkpoint inhibitors and immune agonists on immune cells in monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM) and MM and tumor-specific T lymphocytes

11577

Background: Characterization of expression and function of immune regulatory molecules in tumor microenvironment will provide the framework for developing novel therapeutic strategies. Methods: We evaluated the expression and functional impact of various immuno-regulatory molecules, PD-1, PDL-1, PDL-2, LAG3, TIM3, OX40 and GITR, on the CD138+ tumor cells, myeloid derived suppressor cells (MDSC), and T cell subsets from patients with MGUS, SMM and active MM (newly diagnosed, relapsed, relapsed/refractory), and the myeloma-specific cytotoxic T lymphocytes (CTL) induced with XBP1/CD138/CS1 peptides. Results: PDL-1/PDL-2 was more highly expressed on CD138+ myeloma cells in active MM than SMM or MGUS. G-type MDSC (CD11b+CD33+HLA-DRlowCD15+). Treg cells (CD3+CD4+/CD25+FOXP3+) numbers were increased and expressed higher levels of PD1/PD-L1 in active MM than in MGUS, SMM or healthy donors. Among the checkpoint molecules (PD-1, PDL-1, PDL-2, LAG3, OX40, GITR) evaluated, PD-1 showed the highest expression on CD3+CD4+ and CD3+CD8+T cells in BMMC and PBMC from patients with active MM. Functionally, T cells from MM patients showed increased proliferation upon treatment with an individual immune agonist ( > 150%) or checkpoint inhibitor ( > 100%). Interestingly, each individual anti-checkpoint molecule induced proliferation of T cells expressing other checkpoint molecules. In addition, the blockade of PD1, LAG3 or TIM3 enhanced MM antigen-specific cytotoxicity, assessed by parameters including CD107a, granzyme B and IFN-g production, which was most prominent within the memory CTL subset of MM antigen-specific T cells. Conclusions: These results demonstrate an increased frequency of immune regulatory cells, which highly express checkpoint inhibitors in active MM. Direct stimulation with an immune agonist or blockade of a checkpoint inhibitor increased MM patients’ T cell proliferation and myeloma-specific CTL function, supporting development of combination immune regulatory therapies to improve patient outcome in MM.

Targeting proteasome ubiquitin receptor Rpn13 in multiple myeloma

Proteasome inhibitor bortezomib is an effective therapy for relapsed and newly diagnosed multiple myeloma (MM); however, dose-limiting toxicities and the development of resistance can limit its long-term utility. Recent research has focused on targeting ubiquitin receptors upstream of 20S proteasome, with the aim of generating less toxic therapies. Here we show that 19S proteasome-associated ubiquitin receptor Rpn13 is more highly expressed in MM cells than in normal plasma cells. Rpn13-siRNA (small interfering RNA) decreases MM cell viability. A novel agent RA190 targets Rpn13 and inhibits proteasome function, without blocking the proteasome activity or the 19S deubiquitylating activity. CRISPR/Cas9 Rpn13-knockout demonstrates that RA190-induced activity is dependent on Rpn13. RA190 decreases viability in MM cell lines and patient MM cells, inhibits proliferation of MM cells even in the presence of bone marrow stroma and overcomes bortezomib resistance. Anti-MM activity of RA190 is associated with induction of caspase-dependent apoptosis and unfolded protein response-related apoptosis. MM xenograft model studies show that RA190 is well tolerated, inhibits tumor growth and prolongs survival. Combining RA190 with bortezomib, lenalidomide or pomalidomide induces synergistic anti-MM activity. Our preclinical data validates targeting Rpn13 to overcome bortezomib resistance, and provides the framework for clinical evaluation of Rpn13 inhibitors, alone or in combination, to improve patient outcome in MM.

Pimavanserin

Pimavanserin (ACP-103) is a selective inverse agonist of the 5-hydroxytryptamine 2A (5-HT2A) receptor intended to treat patients with Parkinson's disease psychosis (PDP). Currently there are no FDA-approved medications in the United States for the treatment of PDP, although on September 2, 2014, the United States Food and Drug Administration granted breakthrough therapy status to pimavanserin, highlighting the unmet need for therapeutics in this class. Most antipsychotic medications worsen motor dysfunction due to dopamine antagonism, and all carry a black box warning for an increased risk of mortality in elderly patients with dementia-related psychosis. Data from phase II and phase III clinical trials suggest that pimavanserin is a safe and effective treatment option for PDP. Trial results indicate a significant reduction in hallucinations and delusions in patients with PDP without worsening motor symptoms. Additional studies are ongoing for the treatment of Alzheimer's psychosis, schizophrenia and insomnia. Such promising outcomes warrant a review of the available literature regarding pimavanserin and its use in the treatment of PDP symptoms.

miR-23b/SP1/c-myc forms a feed-forward loop supporting multiple myeloma cell growth

Deregulated microRNA (miR)/transcription factor (TF)-based networks represent a hallmark of cancer. We report here a novel c-Myc/miR-23b/Sp1 feed-forward loop with a critical role in multiple myeloma (MM) and Waldenstrom's macroglobulinemia (WM) cell growth and survival. We have found miR-23b to be downregulated in MM and WM cells especially in the presence of components of the tumor bone marrow milieu. Promoter methylation is one mechanism of miR-23b suppression in myeloma. In gain-of-function studies using miR-23b mimics-transfected or in miR-23b-stably expressing MM and WM cell lines, we observed a significant decrease in cell proliferation and survival, along with induction of caspase-3/7 activity over time, thus supporting a tumor suppressor role for miR-23b. At the molecular level, miR-23b targeted Sp1 3'UTR and significantly reduced Sp1-driven nuclear factor-κB activity. Finally, c-Myc, an important oncogenic transcription factor known to stimulate MM cell proliferation, transcriptionally repressed miR-23b. Thus MYC-dependent miR-23b repression in myeloma cells may promote activation of oncogenic Sp1-mediated signaling, representing the first feed-forward loop with critical growth and survival role in myeloma.

SAR650984 directly induces multiple myeloma cell death via lysosomal-associated and apoptotic pathways, which is further enhanced by pomalidomide

The anti-CD38 monoclonal antibody SAR650984 (SAR) is showing promising clinical activity in treatment of relapsed and refractory multiple myeloma (MM). Besides effector-mediated antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity, we here define molecular mechanisms of SAR-directed MM cell death and enhanced anti-MM activity triggered by SAR with Pomalidomide (Pom). Without Fc-cross-linking agents or effector cells, SAR specifically induces homotypic aggregation (HA)-associated cell death in MM cells dependent on the level of cell surface CD38 expression, actin cytoskeleton and membrane lipid raft. SAR and its F(ab)'2 fragments trigger caspase 3/7-dependent apoptosis in MM cells highly expressing CD38, even with p53 mutation. Importantly, SAR specifically induces lysosome-dependent cell death (LCD) by enlarging lysosomes and increasing lysosomal membrane permeabilization associated with leakage of cathepsin B and LAMP-1, regardless of the presence of interleukin-6 or bone marrow stromal cells. Conversely, the lysosomal vacuolar H+-ATPase inhibitor blocks SAR-induced LCD. SAR further upregulates reactive oxygen species. Pom enhances SAR-induced direct and indirect killing even in MM cells resistant to Pom/Len. Taken together, SAR is the first therapeutic monoclonal antibody mediating direct cytotoxicity against MM cells via multiple mechanisms of action. Our data show that Pom augments both direct and effector cell-mediated MM cytotoxicity of SAR, providing the framework for combination clinical trials.

Targeting IL-17A in multiple myeloma: a potential novel therapeutic approach in myeloma

We have previously demonstrated that interleukin-17A (IL-17) producing Th17 cells are significantly elevated in blood and bone marrow (BM) in multiple myeloma (MM) and IL-17A promotes MM cell growth via the expression of IL-17 receptor. In this study, we evaluated anti-human IL-17A human monoclonal antibody (mAb), AIN457 in MM. We observe significant inhibition of MM cell growth by AIN457 both in the presence and absence of BM stromal cells (BMSC). While IL-17A induces IL-6 production, AIN457 significantly down-regulated IL-6 production and MM cell-adhesion in MM-BMSC co-culture. AIN-457 also significantly inhibited osteoclast cell–differentiation. More importantly, in the SCIDhu model of human myeloma administration of AIN-457 weekly for 4 weeks after the first detection of tumor in mice led to a significant inhibition of tumor growth and reduced bone damage compared to isotype control mice. To understand the mechanism of action of anti-IL-17A mAb, we report here, that MM cells express IL-17A. We also observed that IL-17A knock-down inhibited MM cell growth and their ability to induce IL-6 production in co-cultures with BMSC. These pre-clinical observations suggest efficacy of AIN 457 in myeloma and provide the rationale for its clinical evaluation for anti-myeloma effects and for improvement of bone disease.

Class IIa HDAC inhibition enhances ER stress-mediated cell death in multiple myeloma

Histone deacetylase (HDAC) inhibitors have been extensively investigated as therapeutic agents in cancer. However, the biological role of class IIa HDACs (HDAC4, 5, 7 and 9) in cancer cells, including multiple myeloma (MM), remains unclear. Recent studies show HDAC4 interacts with activating transcription factor 4 (ATF4) and inhibits activation of endoplasmic reticulum (ER) stress-associated proapoptotic transcription factor C/EBP homologous protein (CHOP). In this study, we hypothesized that HDAC4 knockdown and/or inhibition could enhance apoptosis in MM cells under ER stress condition by upregulating ATF4, followed by CHOP. HDAC4 knockdown showed modest cell growth inhibition; however, it markedly enhanced cytotoxicity induced by either tunicamycin or carfilzomib (CFZ), associated with upregulating ATF4 and CHOP. For pharmacological inhibition of HDAC4, we employed a novel and selective class IIa HDAC inhibitor TMP269, alone and in combination with CFZ. As with HDAC4 knockdown, TMP269 significantly enhanced cytotoxicity induced by CFZ in MM cell lines, upregulating ATF4 and CHOP and inducing apoptosis. Conversely, enhanced cytotoxicity was abrogated by ATF4 knockdown, confirming that ATF4 has a pivotal role mediating cytotoxicity in this setting. These results provide the rationale for novel treatment strategies combining class IIa HDAC inhibitors with ER stressors, including proteasome inhibitors, to improve patient outcome in MM.

MiR-29b replacement inhibits proteasomes and disrupts aggresome+autophagosome formation to enhance the antimyeloma benefit of bortezomib

Evading apoptosis is a cancer hallmark that remains a serious obstacle in current treatment approaches. Although proteasome inhibitors (PIs) have transformed management of multiple myeloma (MM), drug resistance emerges through induction of the aggresome+autophagy pathway as a compensatory protein clearance mechanism. Genome-wide profiling identified microRNAs (miRs) differentially expressed in bortezomib-resistant myeloma cells compared with drug-naive cells. The effect of individual miRs on proteasomal degradation of short-lived fluorescent reporter proteins was then determined in live cells. MiR-29b was significantly reduced in bortezomib-resistant cells as well as in cells resistant to second-generation PIs carfilzomib and ixazomib. Luciferase reporter assays demonstrated that miR-29b targeted PSME4 that encodes the proteasome activator PA200. Synthetically engineered miR-29b replacements impaired the growth of myeloma cells, patient tumor cells and xenotransplants. MiR-29b replacements also decreased PA200 association with proteasomes, reduced the proteasome's peptidase activity and inhibited ornithine decarboxylase turnover, a proteasome substrate degraded through ubiquitin-independent mechanisms. Immunofluorescence studies revealed that miR-29b replacements enhanced the bortezomib-induced accumulation of ubiquitinated proteins but did not reveal aggresome or autophagosome formation. Taken together, our study identifies miR-29b replacements as the first-in-class miR-based PIs that also disrupt the autophagy pathway and highlight their potential to synergistically enhance the antimyeloma effect of bortezomib.

A multiepitope of XBP1, CD138 and CS1 peptides induces myeloma-specific cytotoxic T lymphocytes in T cells of smoldering myeloma patients

We evaluated a cocktail of HLA-A2-specific peptides including heteroclitic XBP1 US184-192 (YISPWILAV), heteroclitic XBP1 SP367-375 (YLFPQLISV), native CD138260-268 (GLVGLIFAV) and native CS1239-247 (SLFVLGLFL), for their ability to elicit multipeptide-specific cytotoxic T lymphocytes (MP-CTLs) using T cells from smoldering multiple myeloma (SMM) patients. Our results demonstrate that MP-CTLs generated from SMM patients' T cells show effective anti-MM responses including CD137 (4-1BB) upregulation, CTL proliferation, interferon-γ production and degranulation (CD107a) in an HLA-A2-restricted and peptide-specific manner. Phenotypically, we observed increased total CD3(+)CD8(+) T cells (>80%) and cellular activation (CD69(+)) within the memory SMM MP-CTL (CD45RO(+)/CD3(+)CD8(+)) subset after repeated multipeptide stimulation. Importantly, SMM patients could be categorized into distinct groups by their level of MP-CTL expansion and antitumor activity. In high responders, the effector memory (CCR7(-)CD45RO(+)/CD3(+)CD8(+)) T-cell subset was enriched, whereas the remaining responders' CTL contained a higher frequency of the terminal effector (CCR7(-)CD45RO(-)/CD3(+)CD8(+)) subset. These results suggest that this multipeptide cocktail has the potential to induce effective and durable memory MP-CTL in SMM patients. Therefore, our findings provide the rationale for clinical evaluation of a therapeutic vaccine to prevent or delay progression of SMM to active disease.

New drugs and novel mechanisms of action in multiple myeloma in 2013: a report from the International Myeloma Working Group (IMWG)

Treatment in medical oncology is gradually shifting from the use of nonspecific chemotherapeutic agents toward an era of novel targeted therapy in which drugs and their combinations target specific aspects of the biology of tumor cells. Multiple myeloma (MM) has become one of the best examples in this regard, reflected in the identification of new pathogenic mechanisms, together with the development of novel drugs that are being explored from the preclinical setting to the early phases of clinical development. We review the biological rationale for the use of the most important new agents for treating MM and summarize their clinical activity in an increasingly busy field. First, we discuss data from already approved and active agents (including second- and third-generation proteasome inhibitors (PIs), immunomodulatory agents and alkylators). Next, we focus on agents with novel mechanisms of action, such as monoclonal antibodies (MoAbs), cell cycle-specific drugs, deacetylase inhibitors, agents acting on the unfolded protein response, signaling transduction pathway inhibitors and kinase inhibitors. Among this plethora of new agents or mechanisms, some are specially promising: anti-CD38 MoAb, such as daratumumab, are the first antibodies with clinical activity as single agents in MM. Moreover, the kinesin spindle protein inhibitor Arry-520 is effective in monotherapy as well as in combination with dexamethasone in heavily pretreated patients. Immunotherapy against MM is also being explored, and probably the most attractive example of this approach is the combination of the anti-CS1 MoAb elotuzumab with lenalidomide and dexamethasone, which has produced exciting results in the relapsed/refractory setting.

A novel TLR-9 agonist C792 inhibits plasmacytoid dendritic cell-induced myeloma cell growth and enhance cytotoxicity of bortezomib

Our prior study in multiple myeloma (MM) patients showed increased numbers of plasmacytoid dendritic cells (pDCs) in the bone marrow (BM), which both contribute to immune dysfunction as well as promote tumor cell growth, survival and drug resistance. Here we show that a novel Toll-like receptor (TLR-9) agonist C792 restores the ability of MM patient-pDCs to stimulate T-cell proliferation. Coculture of pDCs with MM cells induces MM cell growth; and importantly, C792 inhibits pDC-induced MM cell growth and triggers apoptosis. In contrast, treatment of either MM cells or pDCs alone with C792 does not affect the viability of either cell type. In agreement with our in vitro data, C792 inhibits pDC-induced MM cell growth in vivo in a murine xenograft model of human MM. Mechanistic studies show that C792 triggers maturation of pDCs, enhances interferon-α and interferon-λ secretion and activates TLR-9/MyD88 signaling axis. Finally, C792 enhances the anti-MM activity of bortezomib, lenalidomide, SAHA or melphalan. Collectively, our preclinical studies provide the basis for clinical trials of C792, either alone or in combination, to both improve immune function and overcome drug resistance in MM.

CRM1 inhibition induces tumor cell cytotoxicity and impairs osteoclastogenesis in multiple myeloma: molecular mechanisms and therapeutic implications

The key nuclear export protein CRM1/XPO1 may represent a promising novel therapeutic target in human multiple myeloma (MM). Here we showed that chromosome region maintenance 1 (CRM1) is highly expressed in patients with MM, plasma cell leukemia cells and increased in patient cells resistant to bortezomib treatment. CRM1 expression also correlates with increased lytic bone and shorter survival. Importantly, CRM1 knockdown inhibits MM cell viability. Novel, oral, irreversible selective inhibitors of nuclear export (SINEs) targeting CRM1 (KPT-185, KPT-330) induce cytotoxicity against MM cells (ED50<200 nM), alone and cocultured with bone marrow stromal cells (BMSCs) or osteoclasts (OC). SINEs trigger nuclear accumulation of multiple CRM1 cargo tumor suppressor proteins followed by growth arrest and apoptosis in MM cells. They further block c-myc, Mcl-1, and nuclear factor κB (NF-κB) activity. SINEs induce proteasome-dependent CRM1 protein degradation; concurrently, they upregulate CRM1, p53-targeted, apoptosis-related, anti-inflammatory and stress-related gene transcripts in MM cells. In SCID mice with diffuse human MM bone lesions, SINEs show strong anti-MM activity, inhibit MM-induced bone lysis and prolong survival. Moreover, SINEs directly impair osteoclastogenesis and bone resorption via blockade of RANKL-induced NF-κB and NFATc1, with minimal impact on osteoblasts and BMSCs. These results support clinical development of SINE CRM1 antagonists to improve patient outcome in MM.