Anti-CS1 humanized monoclonal antibody HuLuc63 inhibits myeloma cell adhesion and induces antibody-dependent cellular cytotoxicity in the bone marrow milieu

Multifunctional Bispecific Nanovesicles Targeting SLAMF7 Trigger Potent Antitumor Immunity

The effectiveness of immune checkpoint inhibitor (ICI) therapy is hindered by the ineffective infiltration and functioning of cytotoxic T cells and the immunosuppressive tumor microenvironment (TME). Signaling lymphocytic activation molecule family member 7 (SLAMF7) is a pivotal co-stimulatory receptor thought to simultaneously trigger NK-cell, T-cell, and macrophage antitumor cytotoxicity. However, the potential of this collaborative immune stimulation in antitumor immunity for solid tumors is underexplored due to the exclusive expression of SLAMF7 by hematopoietic cells. Here, we report the development and characterization of multifunctional bispecific nanovesicles (NVs) targeting SLAMF7 and glypican-3-a hepatocellular carcinoma (HCC)-specific tumor antigen. We found that by effectively "decorating" the surfaces of solid tumors with SLAMF7, these NVs directly induced potent and specific antitumor immunity and remodeled the immunosuppressive TME, sensitizing the tumors to programmed cell death protein 1 (PD1) blockade. Our findings highlight the potential of SLAMF7-targeted multifunctional bispecific NVs as an anticancer strategy with implications for designing next-generation targeted cancer therapies.

Preclinical activity of allogeneic SLAMF7-specific CAR T-cells (UCARTCS1) in multiple myeloma

BACKGROUND

Autologous BCMA-specific CAR T-cell therapies have substantial activity in multiple myeloma (MM). However, due to logistical limitations and BCMAlow relapses, there is a need for alternatives. UCARTCS1 cells are 'off-the-shelf' allogeneic CAR T-cells derived from healthy donors targeting SLAMF7 (CS1), which is highly expressed in MM cells. In this study, we evaluated the preclinical activity of UCARTCS1 in MM cell lines, in bone marrow (BM) samples obtained from MM patients and in an MM mouse model.

METHODS

Luciferase-transduced MM cell lines were incubated with UCARTCS1 cells or control (non-transduced, SLAMF7/TCRαβ double knock-out) T-cells at different effector to target ratios for 24 hours. MM cell lysis was assessed by bioluminescence. Anti-MM activity of UCARTCS1 was also evaluated in 29 BM samples obtained from newly diagnosed patients (n=10), daratumumab-naïve relapsed/refractory patients (n=10) and daratumumab-refractory patients (n=9) in 24-hour flow cytometry-based cytotoxicity assays. Finally, UCARTCS1 activity was assessed in mouse xenograft models.

RESULTS

UCARTCS1 cells induced potent CAR-mediated, and dose-dependent lysis of both MM cell lines and primary MM cells. There was no difference in ex vivo activity of UCARTCS1 between heavily pretreated and newly diagnosed patients. In addition, efficacy of UCARTCS1 was not affected by SLAMF7 expression level on MM cells, proportion of tumor cells, or frequency of regulatory T-cells in BM samples obtained from MM patients. UCARTCS1 treatment eliminated SLAMF7+ non-malignant immune cells in a dose-dependent manner, however lysis of normal cells was less pronounced compared to that of MM cells. Additionally, durable anti-MM responses were observed with UCARTCS1 in an MM xenograft model.

CONCLUSIONS

These results demonstrate that UCARTCS1 has potent anti-MM activity against MM cell lines and primary MM cells, as well as in an MM xenograft model and support the evaluation of UCARTCS1 in patients with advanced MM.

"Find Me" and "Eat Me" signals: tools to drive phagocytic processes for modulating antitumor immunity

Phagocytosis, a vital defense mechanism, involves the recognition and elimination of foreign substances by cells. Phagocytes, such as neutrophils and macrophages, rapidly respond to invaders; macrophages are especially important in later stages of the immune response. They detect "find me" signals to locate apoptotic cells and migrate toward them. Apoptotic cells then send "eat me" signals that are recognized by phagocytes via specific receptors. "Find me" and "eat me" signals can be strategically harnessed to modulate antitumor immunity in support of cancer therapy. These signals, such as calreticulin and phosphatidylserine, mediate potent pro-phagocytic effects, thereby promoting the engulfment of dying cells or their remnants by macrophages, neutrophils, and dendritic cells and inducing tumor cell death. This review summarizes the phagocytic "find me" and "eat me" signals, including their concepts, signaling mechanisms, involved ligands, and functions. Furthermore, we delineate the relationships between "find me" and "eat me" signaling molecules and tumors, especially the roles of these molecules in tumor initiation, progression, diagnosis, and patient prognosis. The interplay of these signals with tumor biology is elucidated, and specific approaches to modulate "find me" and "eat me" signals and enhance antitumor immunity are explored. Additionally, novel therapeutic strategies that combine "find me" and "eat me" signals to better bridge innate and adaptive immunity in the treatment of cancer patients are discussed.

Daratumumab‑resistant multiple myeloma with extramedullary disease successfully treated with combination elotuzumab, pomalidomide and dexamethasone: A case report

Despite the emergence of monoclonal antibodies, the prognosis of patients with multiple myeloma (MM) with extramedullary disease remains poor. The present report describes a rare case of daratumumab-refractory MM that was successfully treated with elotuzumab, pomalidomide and dexamethasone. A 66-year-old male patient diagnosed with MM was treated with bortezomib, lenalidomide and dexamethasone, followed by high-dose chemotherapy and autologous stem cell transplantation. Thereafter, the patient was treated with lenalidomide and dexamethasone as maintenance therapy. This was changed to daratumumab, bortezomib and dexamethasone when new paraskeletal lesions were identified, resulting in marked tumor shrinkage. After 15 months, an increase in serum monoclonal protein levels, development of a skeletal lesion in the right second rib and extramedullary disease of the right thoracic mediastinal lymph nodes were noted. Treatment with elotuzumab, pomalidomide and dexamethasone (EPd) resulted in expeditious symptomatic improvement and regression of the lesions. Notably, during daratumumab, bortezomib and dexamethasone treatment, lymphocyte counts gradually increased to a level at which elotuzumab was sufficiently effective. EPd might be a promising strategy for the treatment of patients with relapsed extramedullary MM while on daratumumab treatment.

Nivolumab, Pomalidomide, and Elotuzumab Combination Regimens for Treatment of Relapsed and Refractory Multiple Myeloma: Results from the Phase 3 CheckMate 602 Study

BACKGROUND

Preclinical studies suggest that combining nivolumab, a programmed death-1 (PD-1) immune checkpoint inhibitor, with pomalidomide/dexamethasone (Pd) with or without elotuzumab, an antisignaling lymphocytic activation molecule F7 monoclonal antibody, may improve multiple myeloma (MM) treatment efficacy.

PATIENTS AND METHODS

The phase 3 CheckMate 602 study (NCT02726581) assessed the efficacy and safety of nivolumab plus pomalidomide/dexamethasone (NPd) and NPd plus elotuzumab (NE-Pd). Eligible patients (aged ≥ 18 years) had measurable MM after ≥ 2 prior lines of therapy, that included an immunomodulatory drug (IMiD) and proteasome inhibitor (PI), each for ≥ 2 consecutive cycles, alone or combined, and were refractory to their last line of therapy. Patients were randomized 3:3:1 to receive NPd, Pd, or NE-Pd. The primary endpoint was progression-free survival (PFS); overall response rate (ORR) was a key secondary endpoint.

RESULTS

At a median follow-up of 16.8 months, PFS was similar between treatment arms (Pd, 7.3 months [95% CI, 6.5-8.4]; NPd, 8.4 months [95% CI, 5.8-12.1]; NE-Pd, 6.3 months [95% CI, 2.4-11.1]). ORR was similar in the Pd (55%), NPd (48%), and NE-Pd (42%) arms. Nivolumab-containing arms were associated with a less favorable safety profile versus Pd, including a higher rate of thrombocytopenia (NPd, 25.0%; NE-Pd, 16.7%; Pd, 15.7%), any-grade immune-mediated adverse events (NPd, 13.9%; NE-Pd, 16.7%; Pd, 2.9%), and adverse events leading to discontinuation (NPd, 25.0%; NE-Pd, 33.3%; Pd, 18.6%). No new safety signals were identified.

CONCLUSION

CheckMate 602 did not demonstrate clinical benefit of nivolumab (+/- elotuzumab) plus Pd versus Pd for patients with relapsed/refractory MM (RRMM).

Beyond BCMA: the next wave of CAR T cell therapy in multiple myeloma

Chimeric antigen receptor (CAR) T cell therapy has transformed the treatment landscape of relapsed/refractory multiple myeloma. The current Food and Drug Administration approved CAR T cell therapies idecabtagene vicleucel and ciltacabtagene autoleucel both target B cell maturation antigen (BCMA), which is expressed on the surface of malignant plasma cells. Despite deep initial responses in most patients, relapse after anti-BCMA CAR T cell therapy is common. Investigations of acquired resistance to anti-BCMA CAR T cell therapy are underway. Meanwhile, other viable antigenic targets are being pursued, including G protein-coupled receptor class C group 5 member D (GPRC5D), signaling lymphocytic activation molecule family member 7 (SLAMF7), and CD38, among others. CAR T cells targeting these antigens, alone or in combination with anti-BCMA approaches, appear to be highly promising as they move from preclinical studies to early phase clinical trials. This review summarizes the current data with novel CAR T cell targets beyond BCMA that have the potential to enter the treatment landscape in the near future.

Cytomegalovirus Reactivation during Elotuzumab Therapy in Patients with Multiple Myeloma

INTRODUCTION

Some treatments are associated with cytomegalovirus (CMV) reactivation (CMVRA) in patients with multiple myeloma (MM). However, no reports exist on the association between elotuzumab and CMVRA. Therefore, we assessed the incidence of CMVRA in patients with MM who received elotuzumab therapy.

METHODS

The medical records of 85 patients who underwent elotuzumab therapy were included in the retrospective analysis for CMV positivity.

RESULTS

Thirty patients were tested for CMV antigenemia during elotuzumab therapy, and 16 were positive for CMV antigenemia; the cumulative incidence rate of CMVRA 6 months after elotuzumab initiation was 18.4%. The history of allogeneic stem cell transplantation (allo-HSCT) was significantly more common in the CMVRA group (31.2%) than that of the group without CMVRA (8.7%). However, even among patients who did not undergo allo-HSCT, the cumulative incidence rate of CMVRA at 6 months was 15.1%. During CMVRA, the symptoms included fever in 8 cases, while retinitis was observed in 1 case. Five patients required antiviral therapy and CMV antigenemia resolved in all but 1 case.

CONCLUSION

Although the patient population was heterogeneous, CMVRA cannot be underestimated during elotuzumab therapy, and evaluation of CMVRA, especially in symptomatic cases, is clinically important.

CS1 Expression Pattern in NK Cells and Correlated Factors in Plasma Cell dyscrasias: Implications for Elotuzumab Therapy and CAR-T Efficacy

Treatment with elotuzumab alone has no discernible antitumor effect and progress in chimeric antigen receptor T cells (CAR-T) therapy targeting CS1 is relatively slow. A retrospective analysis was performed on 236 patients with multiple myeloma (MM) and 30 patients with other plasma cell dyscrasias (PCDs). CS1 expression in NK cells, lymphocytes, and monoclonal plasma cells was assessed using multiparameter flow cytometry. Furthermore, new explorations were undertaken regarding the antitumor applications of elotuzumab. Patients with MM had significantly higher CS1 expression levels in plasma cells than other patients with PCDs, with no significant differences between lymphocytes and NK cells. In both patients with MM and other PCDs, CS1 expression was significantly higher in plasma cells than in NK cells and lymphocytes. Univariate and multivariate analyses revealed a significant correlation between CS1 expression in plasma (r = 0.60; P < 0.001) and NK (r = 0.79; P < 0.001) cells. Factors such as cytogenetic abnormalities, disease progression, and survival were not associated with CS1 expression in NK cells. Moreover, this study showed that elotuzumab strongly increases the cytotoxicity of NK cells against non-plasma and plasma tumor cells independent of their CS1 expression level. This underscores the potential of elotuzumab in combination with NK cells as an effective therapeutic strategy against a broad spectrum of tumor types.

Monoclonal Antibodies in the Treatment of Multiple Myeloma

The incorporation of monoclonal antibodies into backbone regimens has substantially improved the clinical outcomes of patients with newly diagnosed and relapsed/refractory multiple myeloma (MM). Although the SLAMF7-targeting antibody elotuzumab has no single- agent activity, there is clinical synergy between elotuzumab and immunomodulatory drugs in patients with relapsed/refractory disease. Daratumumab and isatuximab are CD38-targeting antibodies which have single-agent activity and a favorable safety profile, which make these agents an attractive component of combination regimens. Monoclonal antibodies may cause infusion-related reactions, but with subcutaneous administration these are less frequently observed. All therapeutic antibodies may interfere with assessment of complete response. Next-generation Fc-engineered monoclonal antibodies are in development with the potential to further improve the outcome of patients with MM.

Bispecific Antibodies in the Treatment of Multiple Myeloma

The treatment of multiple myeloma (MM) is evolving rapidly. In recent years, T-cell-based novel immunotherapies emerged as new treatment strategies for patients with relapsed/refractory MM, including highly effective new options like chimeric antigen receptor (CAR)-modified T cells and bispecific antibodies (bsAbs). Currently, B-cell maturation antigen is the most commonly used target antigen for CAR T-cell and bsAb therapies in MM. Results from different clinical trials have demonstrated promising efficacy and acceptable safety profile of bsAb in RRMM.

Epigenetic regulation of CD38/CD48 by KDM6A mediates NK cell response in multiple myeloma

Anti-CD38 monoclonal antibodies like Daratumumab (Dara) are effective in multiple myeloma (MM); however, drug resistance ultimately occurs and the mechanisms behind this are poorly understood. Here, we identify, via two in vitro genome-wide CRISPR screens probing Daratumumab resistance, KDM6A as an important regulator of sensitivity to Daratumumab-mediated antibody-dependent cellular cytotoxicity (ADCC). Loss of KDM6A leads to increased levels of H3K27me3 on the promoter of CD38, resulting in a marked downregulation in CD38 expression, which may cause resistance to Daratumumab-mediated ADCC. Re-introducing CD38 does not reverse Daratumumab-mediated ADCC fully, which suggests that additional KDM6A targets, including CD48 which is also downregulated upon KDM6A loss, contribute to Daratumumab-mediated ADCC. Inhibition of H3K27me3 with an EZH2 inhibitor resulted in CD38 and CD48 upregulation and restored sensitivity to Daratumumab. These findings suggest KDM6A loss as a mechanism of Daratumumab resistance and lay down the proof of principle for the therapeutic application of EZH2 inhibitors, one of which is already FDA-approved, in improving MM responsiveness to Daratumumab.

Elotuzumab, lenalidomide, bortezomib, dexamethasone, and autologous haematopoietic stem-cell transplantation for newly diagnosed multiple myeloma (GMMG-HD6): results from a randomised, phase 3 trial

BACKGROUND

The aim of this trial was to investigate the addition of the anti-SLAMF7 monoclonal antibody elotuzumab to lenalidomide, bortezomib, and dexamethasone (RVd) in induction and consolidation therapy as well as to lenalidomide maintenance treatment in transplant-eligible patients with newly diagnosed multiple myeloma.

METHODS

GMMG-HD6 was a phase 3, randomised trial conducted at 43 main trial sites and 26 associated trial sites throughout Germany. Adult patients (aged 18-70 years) with previously untreated, symptomatic multiple myeloma, and a WHO performance status of 0-3, with 3 being allowed only if caused by myeloma disease and not by comorbid conditions, were randomly assigned 1:1:1:1 to four treatment groups. Induction therapy consisted of four 21-day cycles of RVd (lenalidomide 25 mg orally on days 1-14; bortezomib 1·3 mg/m2 subcutaneously on days 1, 4, 8, and 11]; and dexamethasone 20 mg orally on days 1, 2, 4, 5, 8, 9, 11, 12, and 15 for cycles 1-2) or, RVd induction plus elotuzumab (10 mg/kg intravenously on days 1, 8, and 15 for cycles 1-2, and on days 1 and 11 for cycles 3-4; E-RVd). Autologous haematopoietic stem-cell transplantation was followed by two 21-day cycles of either RVd consolidation (lenalidomide 25 mg orally on days 1-14; bortezomib 1·3 mg/m2 subcutaneously on days 1, 8, and 15; and dexamethasone 20 mg orally on days 1, 2, 8, 9, 15, and 16) or elotuzumab plus RVd consolidation (with elotuzumab 10 mg/kg intravenously on days 1, 8, and 15) followed by maintenance with either lenalidomide (10 mg orally on days 1-28 for cycles 1-3; thereafter, up to 15 mg orally on days 1-28; RVd/R or E-RVd/R group) or lenalidomide plus elotuzumab (10 mg/kg intravenously on days 1 and 15 for cycles 1-6, and on day 1 for cycles 7-26; RVd/E-R or E-RVd/E-R group) for 2 years. The primary endpoint was progression-free survival analysed in a modified intention-to-treat (ITT) population. Safety was analysed in all patients who received at least one dose of trial medication. This trial is registered with ClinicalTrials.gov, NCT02495922, and is completed.

FINDINGS

Between June 29, 2015, and on Sept 11, 2017, 564 patients were included in the trial. The modified ITT population comprised 559 (243 [43%] females and 316 [57%] males) patients and the safety population 555 patients. After a median follow-up of 49·8 months (IQR 43·7-55·5), there was no difference in progression-free survival between the four treatment groups (adjusted log-rank p value, p=0·86), and 3-year progression-free survival rates were 69% (95% CI 61-77), 69% (61-76), 66% (58-74), and 67% (59-75) for patients treated with RVd/R, RVd/E-R, E-RVd/R, and E-RVd/E-R, respectively. Infections (grade 3 or worse) were the most frequently observed adverse event in all treatment groups (28 [20%] of 137 for RVd/R; 32 [23%] of 138 for RVd/E-R; 35 [25%] of 138 for E-RVd/R; and 48 [34%] of 142 for E-RVd/E-R). Serious adverse events (grade 3 or worse) were observed in 68 (48%) of 142 participants in the E-RVd/E-R group, 53 (39%) of 137 in the RVd/R, 53 (38%) of 138 in the RVd/E-R, and 50 (36%) of 138 in the E-RVd/R (36%) group. There were nine treatment-related deaths during the study. Two deaths (one sepsis and one toxic colitis) in the RVd/R group were considered lenalidomide-related. One death in the RVd/E-R group due to meningoencephalitis was considered lenalidomide and elotuzumab-related. Four deaths (one pulmonary embolism, one septic shock, one atypical pneumonia, and one cardiovascular failure) in the E-RVd/R group and two deaths (one sepsis and one pneumonia and pulmonary fibrosis) in the E-RVd/E-R group were considered related to lenalidomide or elotuzumab, or both.

INTERPRETATION

Addition of elotuzumab to RVd induction or consolidation and lenalidomide maintenance in patients with transplant-eligible newly diagnosed multiple myeloma did not provide clinical benefit. Elotuzumab-containing therapies might be reserved for patients with relapsed or refractory multiple myeloma.

FUNDING

Bristol Myers Squibb/Celgene and Chugai.

New Biological Therapies for Multiple Myeloma

Multiple myeloma is a cancer of bone marrow plasma cells that represents approximately 10% of hematologic malignancies. Though it is typically incurable, a remarkable suite of new therapies developed over the last 25 years has enabled durable disease control in most patients. This article briefly introduces the clinical features of multiple myeloma and aspects of multiple myeloma biology that modern therapies exploit. Key current and emerging treatment modalities are then reviewed, including cereblon-modulating agents, proteasome inhibitors, monoclonal antibodies, other molecularly targeted therapies (selinexor, venetoclax), chimeric antigen receptor T cells, T cell-engaging bispecific antibodies, and antibody-drug conjugates. For each modality, mechanism of action and clinical considerations are discussed. These therapies are combined and sequenced in modern treatment pathways, discussed at the conclusion of the article, which have led to substantial improvements in outcomes for multiple myeloma patients in recent years.

Development of therapeutic monoclonal antibodies against DKK1 peptide-HLA-A2 complex to treat human cancers

BACKGROUND

Targeted immunotherapy with monoclonal antibodies (mAbs) is an effective and safe method for the treatment of malignancies. Development of mAbs with improved cytotoxicity, targeting new and known tumor-associated antigens, therefore continues to be an active research area. We reported that Dickkopf-1 (DKK1) is a good target for immunotherapy of human cancers based on its wide expression in different cancers but not in normal tissues. As DKK1 is a secreted protein, mAbs binding directly to DKK1 have limited effects on cancer cells in vivo.

METHODS

The specificity and antibody-binding capacity of DKK1-A2 mAbs were determined using indirect ELISA, confocal imaging, QIFIKIT antibody-binding capacity and cell surface binding assays. The affinity of mAbs was determined using a surface plasmon resonance biosensor. A flow cytometry-based cell death was performed to detect tumor cell apoptosis. Antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) assays were used to evaluate the ability of DKK1-A2 mAbs to mediate ADCC and CDC activities against tumor cells in vitro. Flow cytometry data were collected with an FACSymphony A3 cell analyzer and analyzed with FlowJo V.10.1 software. Human cancer xenograft mouse models were used to determine the in vivo therapeutic efficacy and the potential safety and toxicity of DKK1-A2 mAbs. In situ TUNEL assay was performed to detect apoptosis in tumors and mouse organs.

RESULTS

We generated novel DKK1-A2 mAbs that recognize the DKK1 P20 peptide presented by human HLA-A*0201 (HLA-A2) molecules (DKK1-A2 complexes) that are naturally expressed by HLA-A2+DKK1+ cancer cells. These mAbs directly induced apoptosis in HLA-A2+DKK1+ hematologic and solid cancer cells by activating the caspase-9 cascade, effectively lysed the cancer cells in vitro by mediating CDC and ADCC and were therapeutic against established cancers in their xenograft mouse models. As DKK1 is not detected in most human tissues, DKK1-A2 mAbs neither bound to or killed HLA-A2+ blood cells in vitro nor caused tissue damage in tumor-free or tumor-bearing HLA-A2-transgenic mice.

CONCLUSION

Our study suggests that DKK1-A2 mAbs may be a promising therapeutic agent to treat human cancers.

Bispecific CS1-BCMA CAR-T cells are clinically active in relapsed or refractory multiple myeloma

Multiple myeloma (MM) bears heterogeneous cells that poses a challenge for single-target immunotherapies. Here we constructed bispecific CS1-BCMA CAR-T cells aiming to augment BCMA targeting with CS1. Sixteen patients with relapsed or refractory (RR) MM received CS1-BCMA CAR-T infusion. Six patients (38%) had cytokine release syndrome, which was of grade 1-2 in 31%. No neurological toxicities were observed. The most common severe adverse events were hematological, including leukopenia (100%), neutropenia (94%), lymphopenia (100%) and thrombocytopenia (31%). Three patients with solitary extramedullary disease (sEMD) did not respond. At a median follow-up of 246 days, 13 patients (81%) had an overall response and attained minimal residual disease-negativity, and six (38%) reached a stringent complete response (sCR). Among the 13 responders, 1-year overall survival and progression-free survival were 72.73% and 56.26%, respectively. Four patients maintained sCR with a median duration of 17 months. Four patients experienced BCMA+ and CS1+ relapse or progression. One patient responded after anti-BCMA CAR-T treatment failure. Lenalidomide maintenance after CAR-T infusion and the resistance mechanism of sEMD were preliminarily explored in three patients. CAR-T cells persisted at a median of 406 days. Soluble BCMA could serve as an ideal biomarker for efficacy monitoring. CS1-BCMA CAR-T cells were clinically active with good safety profiles in patients with RRMM. Clinical trial registration: This study was registered on ClinicalTrials.gov, number NCT04662099.

Ex-vivo CS1-OKT3 dual specific bivalent antibody-armed effector T cells mediate cellular immunity against multiple myeloma

Bispecific T cell engaging antibodies (bsAbs) have emerged as novel and powerful therapeutic agents for redirecting T cells towards antigen-specific tumor killing. The cell surface glycoprotein and SLAM family member, CS1, exhibits stable and high-level expression on malignant plasma cells including multiple myeloma, which is indicative of an ideal target for bsAb therapy. Here, we developed a CS1 bsAb (CS1-dbBiTE) using Click chemistry to conjugate intact anti-CS1 antibody (Elotuzumab) and anti-huOKT3 antibody at their respective hinge regions. Using a cellular therapy approach, human T cells were armed ex-vivo with CS1-dbBiTE prior to examining effector activity. Our data indicates that arming T cells with CS1-dbBiTE induced T cell activation and expansion and subsequent cytotoxic activity against CS1-bearing MM tumors, demonstrated by significant CD107a expression as well as inflammatory cytokine secretion. As expected, CS1-dbBiTE armed T cells showed significantly reduced effector activity in the absence of CS1 expression. Similarly, in MM mouse xenograft studies, armed T cells exhibited effective anti-tumor efficacy highlighted by reduced tumor burden in MM.1S tumor-bearing mice compared to controls. On the basis of these findings, the rationale for CS1 targeting by human T cells armed with CS1-dbBiTE presents a potentially effective therapeutic approach for targeting MM.

Real-World Clinical Outcomes in Patients With Multiple Myeloma Administered With Elotuzumab-Based Treatment

Objective Elotuzumab is used to treat relapsed and/or refractory multiple myeloma (MM). However, the optimal patient selection and sequencing in MM therapy are less clear. Therefore, this retrospective cohort study assessed the clinical outcomes of patients with MM who underwent elotuzumab-based therapy. Methods We reviewed the medical records of 85 patients with relapsed/refractory MM who received elotuzumab for the first time. Participants were divided into progressive disease (PD group) and those without PD (non-PD group) at elotuzumab treatment initiation, and each group was analyzed separately. Survival rates were calculated using Kaplan-Meier curves and compared using log-rank tests. Results The median follow-up period was 33.6 (range: 0.5-72.0) months. The median progression-free survival (PFS) and overall survival (OS) of PD and non-PD groups at elotuzumab therapy initiation were 5.3 months and not reached (NR), respectively (P < 0.0001), and 26.8 months and NR, respectively. Patients with triple-class refractory disease in both groups had worse PFS and OS. Twenty-one patients in the non-PD group received elotuzumab as post-hematopoietic stem cell transplantation, whose PFS and OS were NR (95% CI, 21.4 months-NR) and NR (95% CI, NR-NR), respectively. Conclusions Elotuzumab exhibited limited therapeutic efficacy in patients with triple-class refractory MM but better treatment outcomes in situations with adequate disease control and post-transplant treatment.

SLAMF7 as a Promising Immunotherapeutic Target in Multiple Myeloma Treatments

Multiple myeloma (MM) is a common hematological malignancy that has fostered several new therapeutic approaches to combat newly diagnosed or relapsed MM. While the field has advanced over the past 2 decades, the majority of patients will develop resistance to these treatments, causing the need for new therapeutic targets. SLAMF7 is an attractive therapeutic target in multiple myeloma, and a monoclonal antibody that targets SLAMF7 has shown consistent beneficial outcomes in clinical trials to date. In this review, we will focus on the structure and regulation of SLAMF7 and its mechanism of action. The most recent clinical trials will be reviewed to further understand the clinical implications and improve the prognosis of MM. Furthermore, the efficacy of anti-SLAMF7 monoclonal antibodies combined with standard therapies and possible resistance mechanisms will be discussed. This review aimed to provide a detailed summary of the role of SLAMF7 in the pathogenesis of patients with MM and the rationale for further investigation into SLAMF7-mediated molecular pathways associated with MM development.

Targeting B Cell Maturation Antigen in Patients with Multiple Myeloma: Current Perspectives

Relapsed/refractory multiple myeloma remains a challenging disease necessitating the development of more effective treatment options. In the past decade, myeloma therapies have made significant advancements with the introduction of new treatment modalities. One of the new major targets for these novel therapeutics has been B-cell maturation antigen (BCMA), which is expressed on mature B-lymphocytes and plasma cells. There are three main categories of BCMA-targeted therapies currently available, including bispecific antibodies (BsAbs), antibody drug conjugates (ADCs), and chimeric antigen receptor (CAR) T-cell therapies. In this review, we discuss the existing BCMA-targeted therapies and provide insights into currently available treatment and future developments, with a particular focus on clinical efficacy and common drug-related adverse events.

Determining Optimal Combination Regimens for Patients with Multiple Myeloma

While many novel therapies have been approved in recent years for treating patients with multiple myeloma, there is still no established curative regimen, especially for patients with high-risk disease. In this work, we use a mathematical modeling approach to determine combination therapy regimens that maximize healthy lifespan for patients with multiple myeloma. We start with a mathematical model for the underlying disease and immune dynamics, which was presented and analyzed previously. We add the effects of three therapies to the model: pomalidomide, dexamethasone, and elotuzumab. We consider multiple approaches to optimizing combinations of these therapies. We find that optimal control combined with approximation outperforms other methods, in that it can quickly produce a combination regimen that is clinically-feasible and near-optimal. Implications of this work can be used to optimize doses and advance the scheduling of drugs.

Multi-targeted immunotherapeutics to treat B cell malignancies

The concept of multi-targeted immunotherapeutic systems has propelled the field of cancer immunotherapy into an exciting new era. Multi-effector molecules can be designed to engage with, and alter, the patient's immune system in a plethora of ways. The outcomes can vary from effector cell recruitment and activation upon recognition of a cancer cell, to a multipronged immune checkpoint blockade strategy disallowing evasion of the cancer cells by immune cells, or to direct cancer cell death upon engaging multiple cell surface receptors simultaneously. Here, we review the field of multi-specific immunotherapeutics implemented to treat B cell malignancies. The mechanistically diverse strategies are outlined and discussed; common B cell receptor antigen targeting strategies are outlined and summarized; and the challenges of the field are presented along with optimistic insights for the future.

SLAM-family receptors come of age as a potential molecular target in cancer immunotherapy

The signaling lymphocytic activation molecule (SLAM) family receptors were discovered in immune cells for the first time. The SLAM-family receptors are a significant player in cytotoxicity, humoral immune responses, autoimmune diseases, lymphocyte development, cell survival, and cell adhesion. There is growing evidence that SLAM-family receptors have been involved in cancer progression and heralded as a novel immune checkpoint on T cells. Previous studies have reported the role of SLAMs in tumor immunity in various cancers, including chronic lymphocytic leukemia, lymphoma, multiple myeloma, acute myeloid leukemia, hepatocellular carcinoma, head and neck squamous cell carcinoma, pancreas, lung, and melanoma. Evidence has deciphered that the SLAM-family receptors may be targeted for cancer immunotherapy. However, our understanding in this regard is not complete. This review will discuss the role of SLAM-family receptors in cancer immunotherapy. It will also provide an update on recent advances in SLAM-based targeted immunotherapies.

Treatment Strategy for Ultra-High-Risk Multiple Myelomas with Chromosomal Aberrations Considering Minimal Residual Disease Status and Bone Marrow Microenvironment

Despite the development of anti-myeloma therapeutics, such as proteasome inhibitors, immunomodulatory drugs, anti-CD38 monoclonal antibodies, and autologous stem cell transplantation (ASCT), multiple myeloma remains incurable. A trial treatment combining four drugs-daratumumab, carfilzomib, lenalidomide, and dexamethasone-followed by ASCT frequently results in minimal residual disease (MRD) negativity and prevents progressive disease in patients with standard- and high-risk cytogenetics; however, it is insufficient to overcome the poor outcomes in patients with ultra-high-risk chromosomal aberration (UHRCA). In fact, MRD status in autografts can predict clinical outcomes after ASCT. Therefore, the current treatment strategy might be insufficient to overcome the negative impact of UHRCA in patients with MRD positivity after the four-drug induction therapy. High-risk myeloma cells lead to poor clinical outcomes not only by aggressive myeloma behavior but also via the generation of a poor bone marrow microenvironment. Meanwhile, the immune microenvironment effectively suppresses myeloma cells with a low frequency of high-risk cytogenetic abnormalities in early-stage myeloma compared to late-stage myeloma. Therefore, early intervention might be key to improving clinical outcomes in myeloma patients. The purpose of this review is to improve clinical outcomes in patients with UHRCA by considering MRD assessment results and improvement of the microenvironment.

Ex vivo drug response heterogeneity reveals personalized therapeutic strategies for patients with multiple myeloma

Multiple myeloma (MM) is a plasma cell malignancy defined by complex genetics and extensive patient heterogeneity. Despite a growing arsenal of approved therapies, MM remains incurable and in need of guidelines to identify effective personalized treatments. Here, we survey the ex vivo drug and immunotherapy sensitivities across 101 bone marrow samples from 70 patients with MM using multiplexed immunofluorescence, automated microscopy and deep-learning-based single-cell phenotyping. Combined with sample-matched genetics, proteotyping and cytokine profiling, we map the molecular regulatory network of drug sensitivity, implicating the DNA repair pathway and EYA3 expression in proteasome inhibitor sensitivity and major histocompatibility complex class II expression in the response to elotuzumab. Globally, ex vivo drug sensitivity associated with bone marrow microenvironmental signatures reflecting treatment stage, clonality and inflammation. Furthermore, ex vivo drug sensitivity significantly stratified clinical treatment responses, including to immunotherapy. Taken together, our study provides molecular and actionable insights into diverse treatment strategies for patients with MM.

Targeting BCMA in Multiple Myeloma: Advances in Antibody-Drug Conjugate Therapy

Multiple myeloma (MM) is an incurable cancer of the plasma cells. In the last twenty years, treatment strategies have evolved toward targeting MM cells-from the shotgun chemotherapy approach to the slightly more targeted approach of disrupting important MM molecular pathways to the immunotherapy approach that specifically targets MM cells based on protein expression. Antibody-drug conjugates (ADCs) are introduced as immunotherapeutic drugs which utilize an antibody to deliver cytotoxic agents to cancer cells distinctively. Recent investigations of ADCs for MM treatment focus on targeting B cell maturation antigen (BCMA), which regulates B cell proliferation, survival, maturation, and differentiation into plasma cells (PCs). Given its selective expression in malignant PCs, BCMA is one of the most promising targets in MM immunotherapy. Compared to other BCMA-targeting immunotherapies, ADCs have several benefits, such as lower price, shorter production period, fewer infusions, less dependence on the patient's immune system, and they are less likely to over-activate the immune system. In clinical trials, anti-BCMA ADCs have shown safety and remarkable response rates in patients with relapsed and refractory MM. Here, we review the properties and clinical applications of anti-BCMA ADC therapies and discuss the potential mechanisms of resistance and ways to overcome them.

Efficacy of elotuzumab for multiple myeloma in reference to lymphocyte counts and kappa/lambda ratio or B2 microglobulin

Novel therapeutic drugs have dramatically improved the overall survival of patients with multiple myeloma. We sought to identify the characteristics of patients likely to exhibit a durable response to one such drug, elotuzumab, by analyzing a real-world database in Japan. We analyzed 179 patients who underwent 201 elotuzumab treatments. The median time to next treatment (TTNT) with the 95% confidence interval was 6.29 months (5.18–9.20) in this cohort. Univariate analysis showed that patients with any of the following had longer TTNT: no high risk cytogenic abnormalities, more white blood cells, more lymphocytes, non-deviated κ/λ ratio, lower β2 microglobulin levels (B2MG), fewer prior drug regimens, no prior daratumumab use and better response after elotuzumab treatment. A multivariate analysis showed that TTNT was longer in patients with more lymphocytes (≥ 1400/μL), non-deviated κ/λ ratio (0.1–10), lower B2MG (< 5.5 mg/L) and no prior daratumumab use. We proposed a simple scoring system to predict the durability of the elotuzumab treatment effect by classifying the patients into three categories based on their lymphocyte counts (0 points for ≥ 1400/μL and 1 point for < 1400/μL) and κ/λ ratio (0 points for 0.1–10 and 1 point for < 0.1 or ≥ 10) or B2MG (0 points for < 5.5 mg/L and 1 point for ≥ 5.5 mg/L). The patients with a score of 0 showed significantly longer TTNT (p < 0.001) and better survival (p < 0.001) compared to those with a score of 1 or 2. Prospective cohort studies of elotuzumab treatment may be needed to validate the usefulness of our new scoring system.

Emerging phagocytosis checkpoints in cancer immunotherapy

Cancer immunotherapy, mainly including immune checkpoints-targeted therapy and the adoptive transfer of engineered immune cells, has revolutionized the oncology landscape as it utilizes patients' own immune systems in combating the cancer cells. Cancer cells escape immune surveillance by hijacking the corresponding inhibitory pathways via overexpressing checkpoint genes. Phagocytosis checkpoints, such as CD47, CD24, MHC-I, PD-L1, STC-1 and GD2, have emerged as essential checkpoints for cancer immunotherapy by functioning as "don't eat me" signals or interacting with "eat me" signals to suppress immune responses. Phagocytosis checkpoints link innate immunity and adaptive immunity in cancer immunotherapy. Genetic ablation of these phagocytosis checkpoints, as well as blockade of their signaling pathways, robustly augments phagocytosis and reduces tumor size. Among all phagocytosis checkpoints, CD47 is the most thoroughly studied and has emerged as a rising star among targets for cancer treatment. CD47-targeting antibodies and inhibitors have been investigated in various preclinical and clinical trials. However, anemia and thrombocytopenia appear to be formidable challenges since CD47 is ubiquitously expressed on erythrocytes. Here, we review the reported phagocytosis checkpoints by discussing their mechanisms and functions in cancer immunotherapy, highlight clinical progress in targeting these checkpoints and discuss challenges and potential solutions to smooth the way for combination immunotherapeutic strategies that involve both innate and adaptive immune responses.

Safety and efficacy of Elotuzumab combination therapy for patients with multiple myeloma: A systematic review and meta-analysis

OBJECTIVE

We evaluate the efficacy and safety of Elotuzumab, an immunostimulatory monoclonal antibody, in combination with concomitant treatment regimens for multiple myeloma (MM) patients.

RESEARCH DESIGN AND METHODS

PubMed, Scopus, Web of Science, and EMBASE databases were searched systematically up to 2 August 2022.

RESULTS

Five randomized control trials with a total of 1,763 participants were included. Elotuzumab combination therapy improved PFS and OS by 14% (hazard ratio [HR] 0.86) and 20% (HR 0.80), respectively, relative to the non-Elotuzumab regimen. Adding Elotuzumab to Lenalidomide plus Dexamethasone regimen (HR 0.82) or Pomalidomide plus Dexamethasone regimen (HR 0.54) were considered to improve the PFS. Meanwhile, the risk of disease progression was only reduced for patients with relapsed/refractory MM (HR 0.70) but not for newly diagnosed/untreated MM (HR 0.93). Finally, the risk of serious adverse events (RR 1.12) and the risk of infection (RR 1.09) and cardiac disorders (RR 1.32) were higher for the experimental group compared to the control group.

CONCLUSIONS

Our findings showed that Elotuzumab combination therapy prolonged OS and PFS compared to non-Elotuzumab treatments in patients with MM. However, further investigations are required to establish the most effective combination of the Elotuzumab regimen.

Elotuzumab Plus Pomalidomide and Dexamethasone for Relapsed/Refractory Multiple Myeloma: Final Overall Survival Analysis From the Randomized Phase II ELOQUENT-3 Trial

PURPOSE

In the phase II ELOQUENT-3 trial (ClinicalTrials.gov identifier: NCT02654132), elotuzumab combined with pomalidomide/dexamethasone (EPd) significantly improved progression-free survival (PFS) versus pomalidomide/dexamethasone (Pd) in patients with relapsed/refractory multiple myeloma (RRMM) previously treated with lenalidomide and a proteasome inhibitor (PI). Here, we present the final overall survival (OS) results.

METHODS

Patients with RRMM who had received ≥ 2 prior lines of therapy, with disease refractory to last therapy and either refractory or relapsed and refractory to lenalidomide and a PI were randomly assigned (1:1) to receive EPd or Pd. The primary end point was PFS per investigator assessment. ORR and OS were secondary end points planned to be tested hierarchically.

RESULTS

A total of 117 patients were randomly assigned to EPd (n = 60) and Pd (n = 57). Among treated patients (EPd 60, Pd 55), there were 37 (61.7%) deaths in the EPd group and 41 (74.5%) in the Pd group, most commonly because of disease progression (EPd 41.7%, Pd 49.1%). Median (95% CI) OS was significantly improved with EPd (29.8 [22.9 to 45.7] months) versus Pd (17.4 [13.8 to 27.7] months), with a hazard ratio of 0.59 (95% CI, 0.37 to 0.93; P = .0217). OS benefit with EPd was observed in most patient subgroups. The safety profile of EPd was consistent with prior reports with no new safety signals detected.

CONCLUSION

EPd demonstrated a statistically significant improvement in OS versus Pd in patients with RRMM previously treated with lenalidomide and a PI who had disease refractory to last therapy. In this setting, ELOQUENT-3 is the first randomized study of a triplet regimen incorporating a monoclonal antibody and Pd to improve both PFS and OS significantly.

The emerging therapeutic landscape of relapsed/refractory multiple myeloma

From a historic lens, treatment for patients with relapsed/refractory multiple myeloma (R/R MM) has advanced significantly since the advent of immunomodulatory agents (IMiDs) in the 1990s, proteasome inhibitors in the 2000s, monoclonal antibodies in the 2010s, and CAR-T treatments in the 2020s. However, the availability of multiple new therapies has also created significant ambiguity regarding therapy selection and sequencing, as consensus guidelines are limited, and cross-trial comparisons of the novel agents are challenging. In this focused review, we discuss the novel Food & Drug Administration (FDA)-approved medications for R/R MM, including the recently approved first-in-class BCMA-directed bispecific antibody teclistamab. We highlight the seminal clinical trials data and discuss optimal sequencing considerations based on the goal of treatment, with an emphasis on the two novel CAR-T cell products. We consider the limited tolerability of certain agents, prospects for our aging population, and financial aspects of these therapies. Finally, we spotlight ongoing trials involving promising agents making their way through the pharmacologic pipeline including the BCMA-directed bispecific antibody elranatamab and the GPRC5D-directed bispecific antibody talquetamab. We summarize our recommendations based on the best available evidence as we enter 2023.

Chimeric antigen receptor T-cell therapy for multiple myeloma

Multiple myeloma (MM) is a malignant plasma cell disorder that remains incurable for most patients, as persistent clonal evolution drives new mutations which confer MM high-risk signatures and resistance to standard care. The past two decades have significantly refashioned the therapeutic options for MM, especially adoptive T cell therapy contributing to impressive response rate and clinical efficacy. Despite great promises achieved from chimeric antigen receptor T-cell (CAR-T) therapy, the poor durability and severe toxicity (cytokine release syndrome and neurotoxicity) are still huge challenges. Therefore, relapsed/refractory multiple myeloma (RRMM), characterized by the nature of clinicopathologic and molecular heterogeneity, is frequently associated with poor prognosis. B Cell Maturation Antigen (BCMA) is the most successful target for CAR-T therapy, and other potential targets either for single-target or dual-target CAR-T are actively being studied in numerous clinical trials. Moreover, mechanisms driving resistance or relapse after CAR-T therapy remain uncharacterized, which might refer to T-cell clearance, antigen escape, and immunosuppressive tumor microenvironment. Engineering CAR T-cell to improve both efficacy and safety continues to be a promising area for investigation. In this review, we aim to describe novel tumor-associated neoantigens for MM, summarize the data from current MM CAR-T clinical trials, introduce the mechanism of disease resistance/relapse after CAR-T infusion, highlight innovations capable of enhanced efficacy and reduced toxicity, and provide potential directions to optimize manufacturing processes.

Treating Multiple Myeloma in the Context of the Bone Marrow Microenvironment

The treatment landscape of multiple myeloma (MM) has evolved considerably with the FDA-approval of at least 15 drugs over the past two decades. Together with the use of autologous stem cell transplantation, these novel therapies have resulted in significant survival benefit for patients with MM. In particular, our improved understanding of the BM and immune microenvironment has led to the development of highly effective immunotherapies that have demonstrated unprecedented response rates even in the multiple refractory disease setting. However, MM remains challenging to treat especially in a high-risk setting. A key mediator of therapeutic resistance in MM is the bone marrow (BM) microenvironment; a deeper understanding is necessary to facilitate the development of therapies that target MM in the context of the BM milieu to elicit deeper and more durable responses with the ultimate goal of long-term control or a cure of MM. In this review, we discuss our current understanding of the role the BM microenvironment plays in MM pathogenesis, with a focus on its immunosuppressive nature. We also review FDA-approved immunotherapies currently in clinical use and highlight promising immunotherapeutic approaches on the horizon.

KIR-based inhibitory CARs overcome CAR-NK cell trogocytosis-mediated fratricide and tumor escape

Trogocytosis is an active process that transfers surface material from targeted to effector cells. Using multiple in vivo tumor models and clinical data, we report that chimeric antigen receptor (CAR) activation in natural killer (NK) cells promoted transfer of the CAR cognate antigen from tumor to NK cells, resulting in (1) lower tumor antigen density, thus impairing the ability of CAR-NK cells to engage with their target, and (2) induced self-recognition and continuous CAR-mediated engagement, resulting in fratricide of trogocytic antigen-expressing NK cells (NKTROG+) and NK cell hyporesponsiveness. This phenomenon could be offset by a dual-CAR system incorporating both an activating CAR against the cognate tumor antigen and an NK self-recognizing inhibitory CAR that transferred a 'don't kill me' signal to NK cells upon engagement with their TROG+ siblings. This system prevented trogocytic antigen-mediated fratricide, while sparing activating CAR signaling against the tumor antigen, and resulted in enhanced CAR-NK cell activity.

Multiple Myeloma Therapy: Emerging Trends and Challenges

Multiple myeloma (MM) is a complex hematologic malignancy characterized by the uncontrolled proliferation of clonal plasma cells in the bone marrow that secrete large amounts of immunoglobulins and other non-functional proteins. Despite decades of progress and several landmark therapeutic advancements, MM remains incurable in most cases. Standard of care frontline therapies have limited durable efficacy, with the majority of patients eventually relapsing, either early or later. Induced drug resistance via up-modulations of signaling cascades that circumvent the effect of drugs and the emergence of genetically heterogeneous sub-clones are the major causes of the relapsed-refractory state of MM. Cytopenias from cumulative treatment toxicity and disease refractoriness limit therapeutic options, hence creating an urgent need for innovative approaches effective against highly heterogeneous myeloma cell populations. Here, we present a comprehensive overview of the current and future treatment paradigm of MM, and highlight the gaps in therapeutic translations of recent advances in targeted therapy and immunotherapy. We also discuss the therapeutic potential of emerging preclinical research in multiple myeloma.

Race for the Cure: From the Oldest to the Newest Monoclonal Antibodies for Multiple Myeloma Treatment

Multiple myeloma is characterized by a wide clinical heterogeneity due to an intricate network of interactions between bone marrow-resident clonal plasma cells and the microenvironment. Over the last years, dramatic improvement in the understanding of these pathways led to the introduction of novel drugs with immune-mediated mechanisms of action. Some of these compounds, such as the anti-cd38 daratumumab and isatuximab, the anti-slamf-7 elotuzumab, and the antibody-drug conjugate belantamab-mafodotin, have been tested in large clinical trials and have now fully entered the real-life management. The bispecific T-cell engagers are under investigation with promising results, and other satisfactory data is expected from the application of nanotechnologies. The perfect timing to introduce these drugs in the sequence of treatment and their adverse events represent new challenges to be addressed, and further experience is required to improve their use.

Treatment Options for Patients With Heavily Pretreated Relapsed and Refractory Multiple Myeloma

Despite the increasing number of treatment options available for multiple myeloma, relapse is still inevitable and there remains a critical unmet need for treatments for patients with late-stage, highly refractory disease. In this review, we discuss currently approved treatment options for heavily pretreated patients with relapsed and refractory multiple myeloma, with a focus on the optimal management of patients with MM refractory to lenalidomide, bortezomib, and in some cases, daratumumab or an anti-CD38 monoclonal antibody. Data from recent clinical trials of immunomodulatory agents (pomalidomide), proteasome inhibitors (PIs; carfilzomib and ixazomib), monoclonal antibodies (elotuzumab, daratumumab, and isatuximab), and other novel therapies (including panobinostat-based therapy) are summarized. We also provide potential therapeutic strategies for patients according to different treatment histories, and include case studies to illustrate the practical use of various treatment options in a clinical setting. Regimens containing pomalidomide, elotuzumab, next-generation PIs, panobinostat, or selinexor may provide effective treatment options in patients with triple-refractory disease. The choice of agents used, and combinations thereof should be individualized as well as strategically planned from early- to late-stage relapse.

Highly expressed genes in multiple myeloma cells - what can they tell us about the disease?

Cancer cells can convert proto‐oncoproteins into oncoproteins by increasing the expression of genes that are oncogenic when expressed at high levels. Such genes can promote oncogenesis without being mutated. To find overexpressed genes in cancer cells from patients with multiple myeloma, we retrieved mRNA expression data from the CoMMpass database and ranked genes by their expression levels. We grouped the most highly expressed genes based on a set of criteria and we discuss the role a selection of them can play in the disease pathophysiology. The list was highly concordant with a similar list based on mRNA expression data from the PADIMAC study. Many well‐known “myeloma genes” such as MCL1, CXCR4, TNFRSF17, SDC1, SLAMF7, PTP4A3, and XBP1 were identified as highly expressed, and we believe that hitherto unrecognized key players in myeloma pathogenesis are also enriched on the list. Highly expressed genes in malignant plasma cells that were absent or expressed at only a low level in healthy plasma cells included IFI6, IFITM1, PTP4A3, SIK1, ALDOA, ATP5MF, ATP5ME, and PSMB4. The ambition of this article is not to validate the role of each gene but to serve as a guide for studies aiming at identifying promising treatment targets.

The efficacy of combination treatment with elotuzumab and lenalidomide is dependent on crosstalk between natural killer cells, monocytes and myeloma cells

Patients with refractory relapsed multiple myeloma respond to combination treatment with elotuzumab and lenalidomide. The mechanisms underlying this observation are not fully understood. Furthermore, biomarkers predictive of response have not been identified to date. To address these issues, we used a humanized myeloma mouse model and adoptive transfer of human natural killer (NK) cells to show that elotuzumab and lenalidomide treatment controlled myeloma growth, and this was mediated through CD16 on NK cells. In co-culture studies, we showed that peripheral blood mononuclear cells from a subset of patients with refractory relapsed multiple myeloma were effective killers of OPM2 myeloma cells when treated with elotuzumab and lenalidomide, and this was associated with significantly increased expression of CD54 on OPM2 cells. Furthermore, elotuzumab- and lenalidomide-induced OPM2 cell killing and increased OPM2 CD54 expression were dependent on both monocytes and NK cells, and these effects were not mediated by soluble factors alone. At the transcript level, elotuzumab and lenalidomide treatment significantly increased OPM2 myeloma cell expression of genes for trafficking and adhesion molecules, NK cell activation ligands and antigen presentation molecules. In conclusion, our findings suggest that multiple myeloma patients require elotuzumab- and lenalidomide-mediated upregulation of CD54 on autologous myeloma cells, in combination with NK cells and monocytes to mediate an effective anti-tumor response. Furthermore, our data suggest that increased myeloma cell CD54 expression levels could be a powerful predictive biomarker for response to elotuzumab and lenalidomide treatment.

Macrophage-mediated anti-tumor immunity against high-risk neuroblastoma

Neuroblastoma is the most common extracranial childhood solid tumor. The majority of high-risk neuroblastoma is resistant/refractory to the current high intensity therapy. Neuroblastoma lacks classical HLA Class I expression and exhibits low mutation burden, allowing neuroblastoma cells to evade CD8+ T cell-mediated immunity. Neuroblastoma cells do not express PD-L1, and tumor-associated macrophages are the predominant PD-L1+ cells in the tumor. In this study, we performed gene expression profiling and survival analyses on large neuroblastoma datasets to address the prognostic effect of PD-L1 gene expression and the possible involvement of the SLAMF7 pathway in the anti-neuroblastoma immunity. High-level expression of PD-L1 was found significantly associated with better outcome of high-risk neuroblastoma patients; two populations of PD-1+ PD-L1+ macrophages could be present in high-risk tumors with PD-1/PD-L1 ratios, ≈1 and >1. Patients with the PD-1/PD-L1 ratio >1 tumor showed inferior survival. High-level co-expression of SLAMF7 and SH2D1B was significantly associated with better survival of the high-risk neuroblastoma patients. Together, this study supports the hypothesis that macrophages are important effector cells in the anti-high-risk neuroblastoma immunity, that PD-1 blockade therapy can be beneficial to the high-risk neuroblastoma subset with the PD-1/PD-L1 expression ratio >1, and that SLAMF7 is a new therapeutic target of high-risk neuroblastoma.

CS1 CAR-T targeting the distal domain of CS1 (SLAMF7) shows efficacy in high tumor burden myeloma model despite fratricide of CD8+CS1 expressing CAR-T cells

Despite improvement in treatment options for myeloma patients, including targeted immunotherapies, multiple myeloma remains a mostly incurable malignancy. High CS1 (SLAMF7) expression on myeloma cells and limited expression on normal cells makes it a promising target for CAR-T therapy. The CS1 protein has two extracellular domains - the distal Variable (V) domain and the proximal Constant 2 (C2) domain. We generated and tested CS1-CAR-T targeting the V domain of CS1 (Luc90-CS1-CAR-T) and demonstrated anti-myeloma killing in vitro and in vivo using two mouse models. Since fratricide of CD8 + cells occurred during production, we generated fratricide resistant CS1 deficient Luc90- CS1- CAR-T (ΔCS1-Luc90- CS1- CAR-T). This led to protection of CD8 + cells in the CAR-T cultures, but had no impact on efficacy. Our data demonstrate targeting the distal V domain of CS1 could be an effective CAR-T treatment for myeloma patients and deletion of CS1 in clinical production did not provide an added benefit using in vivo immunodeficient NSG preclinical models.

An update on novel multiple myeloma targets

Introduction: despite therapeutic progress, leading to a significant improvement of outcome, multiple myeloma (MM) remains a difficult to treat hematologic disease due to its biological heterogeneity and clinical complexity.

Areas covered: Treatment of patients refractory and resistant to all classes of agents used in newly diagnosed MM, is becoming a relevant problem for every hematologist. New generation immunotherapies, such as conjugated mAb, bispecific mAbs and CAR-T cells, targeting novel molecules as BCMA, have showed relevant results in very advanced MM. In the same setting, small molecules, such as selinexor and melflufen, also proved to be effective. We are currently waiting for the results of under evaluation personalized therapy, directed against specific gene mutations or signaling pathways, responsible for disease progression.

Expert Opinion: In the near future, many therapeutic strategies will become available for MM and the challenge will be to position each approach in order to cure, maintaining a good quality of life in these patients.

Contribution of the Tumor Microenvironment to Metabolic Changes Triggering Resistance of Multiple Myeloma to Proteasome Inhibitors

Virtually all patients with multiple myeloma become unresponsive to treatment with proteasome inhibitors over time. Relapsed/refractory multiple myeloma is accompanied by the clonal evolution of myeloma cells with heterogeneous genomic aberrations, diverse proteomic and metabolic alterations, and profound changes of the bone marrow microenvironment. However, the molecular mechanisms that drive resistance to proteasome inhibitors within the context of the bone marrow microenvironment remain elusive. In this review article, we summarize the latest knowledge about the complex interaction of malignant plasma cells with its surrounding microenvironment. We discuss the pivotal role of metabolic reprograming of malignant plasma cells within the tumor microenvironment with a subsequent focus on metabolic rewiring in plasma cells upon treatment with proteasome inhibitors, driving multiple ways of adaptation to the treatment. At the same time, mutual interaction of plasma cells with the surrounding tumor microenvironment drives multiple metabolic alterations in the bone marrow. This provides a tumor-promoting environment, but at the same time may offer novel therapeutic options for the treatment of relapsed/refractory myeloma patients.

Blocking the PCNA/NKp44 Checkpoint to Stimulate NK Cell Responses to Multiple Myeloma

Simple Summary

Membrane-associated PCNA is expressed on the surface of human MM cell lines and primary MM cells. Mab 14-25-9 interacts with membrane-associated PCNA and blocks its binding to NK-expressed NKp44, thus activating NK function. We showed that mAb 14-25-9 can serve as an immune checkpoint blocker, enhancing the function of NK cells on target human MM cell lines and primary cells.

Abstract

Multiple Myeloma (MM) is a devastating malignancy that evades immune destruction using multiple mechanisms. The NKp44 receptor interacts with PCNA (Proliferating Cell Nuclear Antigen) and may inhibit NK cells’ functions. Here we studied in vitro the expression and function of PCNA on MM cells. First, we show that PCNA is present on the cell membrane of five out of six MM cell lines, using novel anti-PCNA mAb developed to recognize membrane-associated PCNA. Next, we stained primary bone marrow (BM) mononuclear cells from MM patients and showed significant staining of membrane-associated PCNA in the fraction of CD38⁺CD138⁺ BM cells that contain the MM cells. Importantly, blocking of the membrane PCNA on MM cells enhanced the activity of NK cells, including IFN-γ-secretion and degranulation. Our results highlight the possible blocking of the NKp44-PCNA immune checkpoint by the mAb 14-25-9 antibody to enhance NK cell responses against MM, providing a novel treatment option.

Novel treatment strategies for acetylcholine receptor antibody-positive myasthenia gravis and related disorders

The presence of autoantibodies directed against the muscle nicotinic acetylcholine receptor (AChR) is the most common cause of myasthenia gravis (MG). These antibodies damage the postsynaptic membrane of the neuromuscular junction and cause muscle weakness by depleting AChRs and thus impairing synaptic transmission. As one of the best-characterized antibody-mediated autoimmune diseases, AChR-MG has often served as a reference model for other autoimmune disorders. Classical pharmacological treatments, including broad-spectrum immunosuppressive drugs, are effective in many patients. However, complete remission cannot be achieved in all patients, and 10% of patients do not respond to currently used therapies. This may be attributed to production of autoantibodies by long-lived plasma cells which are resistant to conventional immunosuppressive drugs. Hence, novel therapies specifically targeting plasma cells might be a suitable therapeutic approach for selected patients. Additionally, in order to reduce side effects of broad-spectrum immunosuppression, targeted immunotherapies and symptomatic treatments will be required. This review presents established therapies as well as novel therapeutic approaches for MG and related conditions, with a focus on AChR-MG.

Chimeric antigen receptor (CAR) T-cell therapy for multiple myeloma

Although treatment outcomes of multiple myeloma patients have improved significantly during the last two decades, myeloma is still an incurable disease. There are newly emerging immunotherapies to treat multiple myeloma including monoclonal antibodies, antibody-drug conjugate, bispecific antibodies, and chimeric antigen receptor (CAR) T cell therapy. Impressive response rate and clinical efficacy in heavily pretreated myeloma patients led to the FDA approval of the first myeloma CAR-T therapy in March 2021. Among many different targets for myeloma CAR-T therapies, B Cell Maturation Antigen (BCMA) has been the most successful target so far, but other targets which can be used either for single-target or dual-target CAR-T's are actively being explored. Clinical efficacy and safety of current myeloma CAR-T therapies will be presented here. Potential mechanisms leading to resistance include clearance of CAR-T cells, antigenic escape, and immunosuppressive tumor microenvironment. Novel strategies to enhance myeloma CAR-T will also be described. In this article, we provide a comprehensive review of the current data and the future directions of myeloma CAR-T therapies.

Emerging Role of Antibody-Drug Conjugates and Bispecific Antibodies for the Treatment of Multiple Myeloma

Multiple myeloma (MM) is characterized by malignant proliferation of malignant plasma cells; it is the second most common hematological malignancy associated with significant morbidity. Genetic intricacy, instability, and diverse clinical presentations remain a barrier to cure. The treatment of MM is modernized with the introduction of newer therapeutics agents, i.e., target-specific monoclonal antibodies. The currently available literature lacks the benefits of newer targeted therapy being developed with an aim to reduce side effects and increase effectiveness, compared to conventional chemotherapy regimens. This article aims to review literature about the current available monoclonal antibodies, antibody-drug conjugates, and bispecific antibodies for the treatment of MM.

Natural Killer Cell-Mediated Immunotherapy for Leukemia

Simple Summary

Conventional therapies such as chemotherapy and radiation in leukemia increase infection susceptibility, adverse side effects and immune cell inactivation. Natural killer (NK) cells are the first line of defense against cancer and are critical in the recognition and cytolysis of rapidly dividing and abnormal cell populations. In this review, we describe NK cells and NK cell receptors, functional impairment of NK cells in leukemia, NK cell immunotherapies currently under investigation including monoclonal antibodies (mAbs), adoptive transfer, chimeric antigen receptor-NKs (CAR-NKs), bi-specific/tri-specific killer engagers (BiKEs/TriKEs) and potential targets of NK cell-mediated immunotherapy for leukemia in the future.

Abstract

Leukemia is a malignancy of the bone marrow and blood resulting from the abnormal differentiation of hematopoietic stem cells (HSCs). There are four main types of leukemia including acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML), and chronic lymphocytic leukemia (CLL). While chemotherapy and radiation have been conventional forms of treatment for leukemia, these therapies increase infection susceptibility, adverse side effects and immune cell inactivation. Immunotherapies are becoming promising treatment options for leukemia, with natural killer (NK) cell-mediated therapy providing a specific direction of interest. The role of NK cells is critical for cancer cell elimination as these immune cells are the first line of defense against cancer proliferation and are involved in both recognition and cytolysis of rapidly dividing and abnormal cell populations. NK cells possess various activating and inhibitory receptors, which regulate NK cell function, signaling either inhibition and continued surveillance, or activation and subsequent cytotoxic activity. In this review, we describe NK cells and NK cell receptors, functional impairment of NK cells in leukemia, NK cell immunotherapies currently under investigation, including monoclonal antibodies (mAbs), adoptive transfer, chimeric antigen receptor-NKs (CAR-NKs), bi-specific/tri-specific killer engagers (BiKEs/TriKEs) and future potential targets of NK cell-based immunotherapy for leukemia.