Phase I trial of anti-CS1 monoclonal antibody elotuzumab in combination with bortezomib in the treatment of relapsed/refractory multiple myeloma

A review: Mechanisms and molecular pathways of signaling lymphocytic activation molecule family 3 (SLAMF3) in immune modulation and therapeutic prospects

The signaling lymphocytic activation molecule (SLAM) family participates in the modulation of various innate and adaptive immune responses. SLAM family (SLAMF) receptors include nine transmembrane glycoproteins, of which SLAMF3 (also known as CD229 or Ly9) has important roles in the modulation of immune responses, from the fundamental activation and suppression of immune cells to the regulation of intricate immune networks. SLAMF3 is mainly expressed in immune cells, such as T, B, and natural killer cells. It has a unique molecular structure, including four immunoglobulin-like domains in the extracellular domain and two immunoreceptor tyrosine-based signaling motifs in the intracellular structural domains. These unique structures have important implications for protein functioning. SLAMF3 is involved in pathogenesis of various disease, particularly autoimmune diseases and cancer. However, despite its potential clinical significance, a comprehensive overview of the current paradigm of SLAMF3 research is lacking. This review summarizes the structure, functional mechanisms, and therapeutic implications of SLAMF3. Our findings highlight the significance of SLAMF3 in both physiological and pathological contexts, and underline its dual role in autoimmunity and malignancies, and including disease progression and prognosis. The review also proposes that future studies on SLAMF3 should explore its context-specific inhibitory and stimulatory effects, expand on its potential in disease mapping, investigate related signaling pathways, and explore its value as a drug target. Research in these areas related to SLAMF3 can provide more precise directions for future therapeutic strategies.

Immune checkpoint inhibitors for multiple myeloma immunotherapy

Multiple myeloma (MM) is related to immune disorders, recent studys have revealed that immunotherapy can greatly benefit MM patients. Immune checkpoints can negatively modulate the immune system and are closely associated with immune escape. Immune checkpoint-related therapy has attracted much attention and research in MM. However, the efficacy of those therapies need further improvements. There need more thoughts about the immune checkpoint to translate their use in clinical work. In our review, we aggregated the currently known immune checkpoints and their corresponding ligands, further more we propose various ways of potential translation applying treatment based on immune checkpoints for MM patients.

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.

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.

Immunotherapy of Multiple Myeloma: Promise and Challenges

Whereas the treatment of MM was dependent solely on alkylating agents and corticosteroids during the prior three decades, the landscape of therapeutic measures to treat the disease began to expand enormously early in the current century. The introduction of new classes of small-molecule drugs, such as proteasome blockers (bortezomib and carfilzomib), immunomodulators (lenalidomide and pomalidomide), nuclear export inhibitors (selinexor), and histone deacetylase blockers (panobinostat), as well as the application of autologous stem cell transplantation (ASCT), resulted in a seismic shift in how the disease is treated. The picture changed dramatically once again starting with the 2015 FDA approval of two monoclonal antibodies (mAbs) - the anti-CD38 daratumumab and the anti-SLAMF7 elotuzumab. Daratumumab, in particular, has had a great impact on MM therapy and today is often included in various regimens to treat the disease, both in newly diagnosed cases and in the relapse/refractory setting. Recently, other immunotherapies have been added to the arsenal of drugs available to fight this malignancy. These include isatuximab (also anti-CD38) and, in the past year, the antibody-drug conjugate (ADC) belantamab mafodotin and the chimeric antigen receptor (CAR) T-cell product idecabtagene vicleucel (ide-cel). While the accumulated benefits of these newer agents have resulted in a doubling of the disease's five-year survival rate to more than 5 years and improved quality of life, the disease remains incurable. Almost without exception patients experience relapse and/or become refractory to the drugs used, making the search for innovative therapies all the more essential. This review covers the current scope of anti-myeloma immunotherapeutic agents, both those in clinical use and on the horizon, including naked mAbs, ADCs, bi- and multi-targeted mAbs, and CAR T-cells. Emphasis is placed on the benefits of each along with the challenges that need to be overcome if MM is to be considered curable in the future.

Targeted Therapies for Multiple Myeloma

Multiple myeloma continues to be a challenging disorder to treat despite improved therapies and the widespread use of proteasome inhibitors and immunomodulatory drugs. Although patient outcomes have improved, the disease continues to invariably relapse, and in the majority of cases, a cure remains elusive. In the last decade, there has been an explosion of novel drugs targeting cellular proteins essential for malignant plasma cell proliferation and survival. In this review, we focus on novel druggable targets leading to the development of monoclonal antibodies and cellular therapies against surface antigens (CD38, CD47, CD138, BCMA, SLAMF7, GPRC5D, FcRH5), inhibitors of epigenetic regulators such as histone deacetylase (HDAC), and agents targeting anti-apoptotic (BCL-2), ribosomal (eEF1A2) and nuclear export (XPO1) proteins.

Immunotherapy with Antibodies in Multiple Myeloma: Monoclonals, Bispecifics, and Immunoconjugates

In the 2010s, immunotherapy revolutionized the treatment landscape of multiple myeloma. CD38-targeting antibodies were initially applied as monotherapy in end-stage patients, but are now also approved by EMA/FDA in combination with standards-of-care in newly diagnosed disease or in patients with early relapse. The approved SLAMF7-targeting antibody can also be successfully combined with lenalidomide or pomalidomide in relapsed/refractory myeloma. Although this has resulted in improved clinical outcomes, there remains a high unmet need in patients who become refractory to immunomodulatory drugs, proteasome inhibitors and CD38-targeting antibodies. Several new antibody formats, such as antibody–drug conjugates (e.g., belantamab mafodotin, which was approved in 2020 and targets BCMA) and T cell redirecting bispecific antibodies (e.g., teclistamab, talquetamab, cevostamab, AMG-420, and CC-93269) are active in these triple-class refractory patients. Based on their promising efficacy, it is expected that these new antibody formats will also be combined with other agents in earlier disease settings.

Monoclonal antibodies in relapsed/refractory myeloma: updated evidence from clinical trials, real-life studies, and meta-analyses

Introduction: In the last few years, monoclonal antibodies have rapidly modified the therapeutic strategies for treating patients with multiple myeloma.Areas covered: In this review, the most recent literature data regarding indications for which monoclonal antibodies are currently or will be shortly approved as salvage therapies in relapsed/refractory myeloma are discussed. In particular, updated results until March 22, 2020 of antibodies directed against CD38 (daratumumab and isatuximab), SLAMF7 (elotuzumab), BCMA (GSK2857916/belantamab mafodotin), and PD-1/PD-1 L axis (nivolumab and pembrolizumab) will be analyzed in detail.Expert opinion: Monoclonal antibodies represent a new, very effective approach that will open novel and dynamic treatment scenarios for myeloma patients in the coming years. Optimal positioning and selection of different antibodies that are or will be soon available, appropriate combinations and careful evaluation of possible new toxicities should be considered in the future management of these patients.

A simple method to distinguish residual elotuzumab from monoclonal paraprotein in immunofixation assays for multiple myeloma patients

Negative immunofixation electrophoresis (IFE) of serum and/or urine is a diagnostic marker for determining a complete response (CR) after immunotherapy for multiple myeloma (MM). However, residual therapeutic antibodies such as elotuzumab (IgG-κ), can compromise IFE evaluation when the affected immunoglobulins belong to the same IgG-κ subclass. We thus sought to develop a simple and rapid method to treat patient serum before IFE to distinguish the residual elotuzumab. Serum samples from patients receiving elotuzumab were treated with a predetermined amount of soluble signaling lymphocyte activation molecule F7 (SLAMF7) protein and then subjected to conventional IFE testing. We tested our method in samples from 12 patients. The IgG-κ band in IFE disappeared or shifted after elotuzumab treatment in four patients with no bone marrow minimal residual disease and normalized free light chain, whereas seven patients with any sign of residual MM showed a remaining IgG-κ band after treatment. One-hour incubation of samples with 6-9 molar excess soluble SLAMF7 before IFE was sufficient to distinguish residual elotuzumab in 11 of 12 samples. This simple method does not require special reagents, can be performed in most clinical laboratories, and enables differentiation between patients with a CR and those requiring further treatment.

Elotuzumab in the treatment of relapsed and refractory multiple myeloma

Multiple myeloma (MM) is still considered an incurable disease. However, drugs with different mechanisms of action that can improve the efficiency of treatment offer hope. Still, there are concerns about an unacceptable increase in toxicity with such regimens. The results of recently published clinical studies of elotuzumab in combination with lenalidomide/dexamethasone or pomalidomide/dexamethasone confirm previous hopes to improve the effect of that treatment. Humanized monoclonal antibodies aimed at SLAMF7 stimulate natural killer cells to fight against MM cells. Elotuzumab used in combination with lenalidomide/dexamethasone or with pomalidomide/dexamethasone is approved by the US FDA to treat patients with relapsed and/or refractory MM. The article is a summary of the recent knowledge about the possibility of using elotuzumab in the treatment of relapsed and/or refractory MM and shows its potential uses in the future.

Bortezomib, lenalidomide, and dexamethasone with or without elotuzumab in patients with untreated, high-risk multiple myeloma (SWOG-1211): primary analysis of a randomised, phase 2 trial

BACKGROUND

The introduction of immunomodulatory agents, proteasome inhibitors, and autologous haematopoietic stem-cell transplantation has improved outcomes for patients with multiple myeloma, but patients with high-risk multiple myeloma have a poor long-term prognosis. We aimed to address optimal treatment for these patients.

METHODS

SWOG-1211 is a randomised phase 2 trial comparing eight cycles of lenalidomide (25 mg orally on days 1-14 every 21 days), bortezomib (1·3 mg/m² subcutaneously on days 1, 4, 8, and 11 every 21 days), and dexamethasone (20 mg orally on days 1, 2, 4, 5, 8, 9, 11, and 12 every 21 days; RVd) induction followed by dose-attenuated RVd maintenance (bortezomib 1 mg/m² subcutaneously on days 1, 8, and 15; lenalidomide 15 mg orally on days 1-21; dexamethasone 12 mg orally on days 1, 18, and 15 every 28 days) until disease progression with or without elotuzumab (10 mg/kg intravenously on days 1, 8, and 15 for cycles 1-2, on days 1 and 11 for cycles 3-8, and on days 1 and 15 during maintenance). Patients were randomly assigned (1:1) to either RVd or RVd-elotuzumab. High-risk multiple myeloma was defined by one of the following: gene expression profiling high risk (GEP^hi), t(14;16), t(14;20), del(17p) or amp1q21, primary plasma cell leukaemia and elevated serum lactate dehydrogenase (two times the upper limit of normal or more). The primary endpoint was progression-free survival, and all analyses were done on intention-to-treat basis among eligible patients who were evaluable for response. This study is registered with ClinicalTrials.gov, NCT01668719.

FINDINGS

100 (RVd n=52, RVd-elotuzumab n=48) patients were enrolled between Oct 27, 2013, and May 15, 2016, across 26 cooperative group institutions in the USA. Median age was 64 years (IQR 57-70, range 36-85). 74 (75%) of 99 had International Staging System stage II or stage III disease, 47 (47%) of 99 had amp1q21, 37 (37%) of 100 had del17p, 11 (11%) of 100 had t(14;16), eight (9%) of 90 were GEP^hi, seven (7%) of 100 had primary plasma cell leukaemia, five (5%) of 100 had t(14;20), four (4%) of 100 had elevated serum lactate dehydrogenase, and 17 (17%) had two or more features. With a median follow-up of 53 months (IQR 46-59), no difference in median progression-free survival was observed (RVd 33·64 months [95% CI 19·55-not reached], RVd-elotuzumab 31·47 months [18·56-53·98]; hazard ratio 0·968 [80% CI 0·697-1·344]; one-sided p=0·45]. 37 (71%) of 52 patients in the RVd group and 37 (77%) of 48 in the RVd-elotuzumab group had grade 3 or worse adverse events. No significant differences in the safety profile were observed, although some notable results included grade 3-5 infections (four [8%] of 52 in the RVd group, eight [17%] of 48 in the RVd-elotuzumab group), sensory neuropathy (four [8%] of 52 in the RVd group, six [13%] of 48 in the RVd-elotuzumab group), and motor neuropathy (one [2%] of 52 in the RVd group, four [8%] of 48 in the RVd-elotuzumab group). There were no treatment-related deaths in the RVd group and one death in the RVd-elotuzumab group for which study treatment was listed as possibly contributing by the investigator.

INTERPRETATION

In the first randomised study of high-risk multiple myeloma reported to date, the addition of elotuzumab to RVd induction and maintenance did not improve patient outcomes. However, progression-free survival in both study groups exceeded the original statistical assumptions and supports the role for continuous proteasome inhibitors and immunomodulatory drug combination maintenance therapy for this patient population.

FUNDING

National Institutes of Health, National Cancer Institute, Bristol Myers Squibb, Celgene, Leukemia and Lymphoma Society.

Deregulation of Adaptive T Cell Immunity in Multiple Myeloma: Insights Into Mechanisms and Therapeutic Opportunities

Immunotherapy has recently emerged as a promising treatment option for multiple myeloma (MM) patients. Profound immune dysfunction and evasion of immune surveillance are known to characterize MM evolution and disease progression. Along with genomic changes observed in malignant plasma cells, the bone marrow (BM) milieu creates a protective environment sustained by the complex interaction of BM stromal cells (BMSCs) and malignant cells that using bidirectional connections and cytokines released stimulate disease progression, drug resistance and enable immune escape. Local immune suppression and T-cell exhaustion are important mediating factors of clinical outcomes and responses to immune-based approaches. Thus, further characterization of the defects present in the immune system of MM patients is essential to develop novel therapies and to repurpose the existing ones. This review seeks to provide insights into the mechanisms that promote tumor escape, cause inadequate T-cell stimulation and impaired cytotoxicity in MM. Furthermore, it highlights current immunotherapies being used to restore adaptive T-cell immune responses in MM and describes strategies created to escape these multiple immune evasion mechanisms.

Natural Killer Cells: Tumor Surveillance and Signaling

Natural killer (NK) cells play a pivotal role in cancer immunotherapy due to their innate ability to detect and kill tumorigenic cells. The decision to kill is determined by the expression of a myriad of activating and inhibitory receptors on the NK cell surface. Cell-to-cell engagement results in either self-tolerance or a cytotoxic response, governed by a fine balance between the signaling cascades downstream of the activating and inhibitory receptors. To evade a cytotoxic immune response, tumor cells can modulate the surface expression of receptor ligands and additionally, alter the conditions in the tumor microenvironment (TME), tilting the scales toward a suppressed cytotoxic NK response. To fully harness the killing power of NK cells for clinical benefit, we need to understand what defines the threshold for activation and what is required to break tolerance. This review will focus on the intracellular signaling pathways activated or suppressed in NK cells and the roles signaling intermediates play during an NK cytotoxic response.

Novel Agents in Multiple Myeloma

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

Therapeutic Monoclonal Antibodies and Antibody Products: Current Practices and Development in Multiple Myeloma

Immunotherapy is the latest innovation for the treatment of multiple myeloma (MM). Monoclonal antibodies (mAbs) entered the clinical practice and are under evaluation in clinical trials. MAbs can target highly selective and specific antigens on the cell surface of MM cells causing cell death (CD38 and CS1), convey specific cytotoxic drugs (antibody-drug conjugates), remove the breaks of the immune system (programmed death 1 (PD-1) and PD-ligand 1/2 (L1/L2) axis), or boost it against myeloma cells (bi-specific mAbs and T cell engagers). Two mAbs have been approved for the treatment of MM: the anti-CD38 daratumumab for newly-diagnosed and relapsed/refractory patients and the anti-CS1 elotuzumab in the relapse setting. These compounds are under investigation in clinical trials to explore their synergy with other anti-MM regimens, both in the front-line and relapse settings. Other antibodies targeting various antigens are under evaluation. B cell maturation antigens (BCMAs), selectively expressed on plasma cells, emerged as a promising target and several compounds targeting it have been developed. Encouraging results have been reported with antibody drug conjugates (e.g., GSK2857916) and bispecific T cell engagers (BiTEs^®), including AMG420, which re-directs T cell-mediated cytotoxicity against MM cells. Here, we present an overview on mAbs currently approved for the treatment of MM and promising compounds under investigation.

Novel Immunotherapeutic Agents for the Treatment of Multiple Myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by the abnormal proliferation of clonal plasma cells in the bone marrow leading to end-organ manifestations. Despite the advancement in the therapy and care of patients with MM, relapse and resistance to standard therapy remain significant. The development of immunotherapy as a treatment modality for many types of cancers has led investigators to explore its use in MM in order to elicit myeloma-targeted immune responses, especially given that immune dysregulation is an underlying feature in the pathogenesis and progression of MM. In this concise review, we discuss the different advances in the immune-based therapy of MM, from immunomodulation, vaccines, to monoclonal antibodies, checkpoint inhibitors, adoptive T-cell therapies, and future promising therapies under investigation.

Monoclonal Antibody Therapies in Multiple Myeloma: A Challenge to Develop Novel Targets

The treatment options in multiple myeloma (MM) has changed dramatically over the past decade with the development of novel agents such as proteasome inhibitors (PIs); bortezomib and immunomodulatory drugs (IMiDs); thalidomide, and lenalidomide which revealed high efficacy and improvement of overall survival (OS) in MM patients. However, despite these progresses, most patients relapse and become eventually refractory to these therapies. Thus, the development of novel, targeted immunotherapies has been pursued aggressively. Recently, next-generation PIs; carfilzomib and ixazomib, IMiD; pomalidomide, histone deacetylase inhibitor (HDADi); panobinostat and monoclonal antibodies (MoAbs); and elotuzumab and daratumumab have emerged, and especially, combination of mAbs plus novel agents has led to dramatic improvements in the outcome of MM patients. The field of immune therapies has been accelerating in the treatment of hematological malignancies and has also taken center stage in MM. This review focuses on an overview of current status of novel MoAb therapy including bispecific T-cell engager (BiTE) antibody (BsAb), antibody-drug conjugate (ADC), and chimeric antigen receptor (CAR) T cells, in relapsed or refractory MM (RRMM). Lastly, investigational novel MoAb-based therapy to overcome immunotherapy resistance in MM is shown.

Novel p97/VCP inhibitor induces endoplasmic reticulum stress and apoptosis in both bortezomib-sensitive and -resistant multiple myeloma cells

p97/VCP is an endoplasmic reticulum (ER)‐associated protein that belongs to the AAA (ATPases associated with diverse cellular activities) ATPase family. It has a variety of cellular functions including ER‐associated protein degradation, autophagy, and aggresome formation. Recent studies have shown emerging roles of p97/VCP and its potential as a therapeutic target in several cancer subtypes including multiple myeloma (MM). We conducted a cell‐based compound screen to exploit novel small compounds that have cytotoxic activity in myeloma cells. Among approximately 2000 compounds, OSSL_325096 showed relatively strong antiproliferative activity in MM cell lines (IC₅₀, 100‐500 nmol/L). OSSL_325096 induced apoptosis in myeloma cell lines, including a bortezomib‐resistant cell line and primary myeloma cells purified from patients. Accumulation of poly‐ubiquitinated proteins, PERK, CHOP, and IREα, was observed in MM cell lines treated with OSSL_325096, suggesting that it induces ER stress in MM cells. OSSL_325096 has a similar chemical structure to DBeQ, a known p97/VCP inhibitor. Knockdown of the gene encoding p97/VCP induced apoptosis in myeloma cells, accompanied by accumulation of poly‐ubiquitinated protein. IC₅₀ of OSSL_325096 to myeloma cell lines were found to be lower (0.1‐0.8 μmol/L) than those of DBeQ (2‐5 μmol/L). In silico protein–drug‐binding simulation suggested possible binding of OSSL_325096 to the ATP binding site in the D2 domain of p97/VCP. In cell‐free ATPase assays, OSSL_325096 showed dose‐dependent inhibition of p97/VCP ATPase activity. Finally, OSSL_325096 inhibited the growth of subcutaneous myeloma cell tumors in vivo. The present data suggest that OSSL_325096 exerts anti‐myeloma activity, at least in part through p97/VCP inhibition.

Update on elotuzumab for the treatment of relapsed/refractory multiple myeloma: patients' selection and perspective

Monoclonal antibodies (mAbs) targeting antigens expressed by plasma cells demonstrated major clinical activity in multiple myeloma patients and therefore became a new major class of drug for these patients. Elotuzumab is a humanized mAb targeting the cell surface signaling lymphocytic activation molecule family member 7, a glycoprotein highly expressed on plasma cells, that is the second mAb approved for the treatment of myeloma patients. The mechanism of action of elotuzumab includes natural killer cell (NK) mediated antibody-dependent cellular cytotoxicity and direct activation of NK-cells. Elotuzumab has been approved in combination with lenalidomide and dexamethasone (Elo-Rd) and pomalidomide and dexamethasone (Elo-Pd) for the treatment of relapsed myeloma patients. The present review will focus on elotuzumab, providing a summary of the mechanism of action, efficacy and safety and taking into consideration patients’ selection.

The Clinical Pharmacology of Elotuzumab

Novel treatment options are needed to improve long-term outcomes for patients with multiple myeloma (MM). In this article, we comprehensively review the clinical pharmacology of elotuzumab, a first-in-class monoclonal anti-SLAMF7 antibody approved in combination with lenalidomide and dexamethasone (ELd) for the treatment of patients with MM and one to three prior therapies. Elotuzumab has a dual mechanism of action to specifically kill myeloma cells: binding SLAMF7 on myeloma cells facilitates natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC), and direct engagement of SLAMF7 on NK cells further enhances NK cell activity. Elotuzumab administration causes transient elevations of selected cytokines (tumor necrosis factor-α, interferon-γ-induced protein-10 and monocyte chemoattractant protein-1). The temporary nature of these elevations (greatest after the first dose, with a trend to return to baseline by day 7) suggests a low likelihood of facilitating clinically meaningful drug-drug interactions. Elotuzumab exposure increases more than proportionally to dose and >80% SLAMF7 receptor occupancy is achieved with the approved elotuzumab 10 mg/kg regimen. Population pharmacokinetic data from 375 patients demonstrated weight-based dosing is appropriate for elotuzumab, and that ethnicity and hepatic/renal function have minimal effects on exposure. Exposure-response analysis of patients treated with ELd demonstrated that increased elotuzumab exposure does not elevate the risk of grade 3+ adverse events (AEs) or AEs leading to discontinuation/death. Elotuzumab antidrug antibodies occurred in 18.5% of patients treated with ELd or elotuzumab plus bortezomib and dexamethasone, but were generally transient and did not affect elotuzumab efficacy or safety. A monotherapy study indicated elotuzumab does not have clinically relevant effects on QT intervals.

Rationale and design of the German-speaking myeloma multicenter group (GMMG) trial HD6: a randomized phase III trial on the effect of elotuzumab in VRD induction/consolidation and lenalidomide maintenance in patients with newly diagnosed myeloma

Background

Despite major advances in therapy, multiple myeloma is still an incurable malignancy in the majority of patients. To increase survival, deeper remissions (i.e. CR) translating into longer PFS need to be achieved. Incorporation of new drugs (i.e. bortezomib and lenalidomide) as induction and maintenance treatment in an intensified treatment concept, including high dose melphalan (200 mg/m²), has resulted in increased CR rates, and is considered the standard of care for younger patients. Elotuzumab in combination with lenalidomide and dexamethasone has given better results as lenalidomide and dexamethasone alone in a phase III trial. The GMMG-HD6 trial will be the first phase III trial investigating the role of elotuzumab in combination with bortezomib, lenalidomide and dexamethasone (VRD) induction/consolidation and lenalidomide maintenance within a high dose concept.

Methods

GMMG-HD6 is a randomized, open, multicenter phase III trial. The planned recruitment number is 564 NDMM patients. All patients will receive 4 VRD cycles as induction and undergo peripheral blood stem cell mobilization and harvesting. Thereafter they will be treated with high dose melphalan therapy plus autologous stem cell transplantation followed by 2 cycles of VRD consolidation and lenalidomide maintenance. Patients in arm B1 + B2 will additionally receive elotuzumab in the induction phase, whereas patients in A2 + B2 will be treated with elotuzumab added to consolidation and maintenance. The primary endpoint of the trial is PFS. Secondary objectives and endpoints are OS, CR rates after induction therapy comparing the two arms VRD (A1 + A2) vs VRD + elotuzumab (B1 + B2), CR rates after consolidation treatment, best response to treatment during the study, time to progression (TTP), duration of response (DOR), toxicity and quality of life.

Results

Since this is the publication of a study protocol of an ongoing study, no results can be presented.

Discussion

This phase III trial is designed to evaluate whether the addition of elotuzumab to an intensified treatment concept with high dose melphalan chemotherapy plus autologous stem cell transplantation and induction, consolidation and maintenance treatment with bortezomib and lenalidomide is able to improve PFS compared to the same concept without elotuzumab.

Trial registration

NCT02495922 on June 24th, 2015.

Potential of NK cells in multiple Myeloma therapy

Introduction: Despite rapid advances in myeloma treatment with the development of new drugs, curative therapies remain elusive. Relapsed/refractory disease related to progressive dysregulation of immune system and acquired genetic abnormalities continues to be a major obstacle in achieving cure. Immune-based therapy harnessing the host defense mechanism of natural killer (NK) cells is a promising avenue in the treatment of myeloma. Areas covered: Here, we discuss the biology and cytotoxic activity of NK cells and the potential role of these innate immune cells in defense against cancer and specifically multiple myeloma. We also discuss the role of NK cells in the anti-myeloma effects of autologous and allogeneic stem cell transplantation, various novel drugs, and treatment modalities such as chimeric antigen receptor therapy. Immune evasion, either directly or indirectly involving NK cell dysfunction, may be a key and under-recognized mechanism in myeloma progression. We reviewed extensive literature identified using the keywords immunotherapy, natural killer cells, and multiple myeloma. Expert opinion: Novel treatment approaches in myeloma utilizing the immunomodulatory and cytotoxic properties of NK cells to eradicate resistant and quiescent clones could pave the way for potentially curative interventions.

Immunotherapeutics in Multiple Myeloma: How Can Translational Mouse Models Help?

Multiple myeloma (MM) is usually diagnosed in older adults at the time of immunosenescence, a collection of age-related changes in the immune system that contribute to increased susceptibility to infection and cancer. The MM tumor microenvironment and cumulative chemotherapies also add to defects in immunity over the course of disease. In this review we discuss how mouse models have furthered our understanding of the immune defects caused by MM and enabled immunotherapeutics to progress to clinical trials, but also question the validity of using immunodeficient models for these purposes. Immunocompetent models, in particular the 5T series and Vk^⁎MYC models, are increasingly being utilized in preclinical studies and are adding to our knowledge of not only the adaptive immune system but also how the innate system might be enhanced in anti-MM activity. Finally we discuss the concept of immune profiling to target patients who might benefit the most from immunotherapeutics, and the use of humanized mice and 3D culture systems for personalized medicine.

Mechanisms of NK Cell Activation and Clinical Activity of the Therapeutic SLAMF7 Antibody, Elotuzumab in Multiple Myeloma

Multiple myeloma (MM) is a bone marrow plasma cell neoplasm and is the second most-common hematologic malignancy. Despite advances in therapy, MM remains largely incurable. Elotuzumab is a humanized IgG1 monoclonal antibody targeting SLAMF7, which is highly expressed on myeloma cells, and the antibody is approved for the treatment of relapsed and/or refractory (RR) MM in combination with lenalidomide and dexamethasone. Elotuzumab can stimulate robust antibody-dependent cellular cytotoxicity (ADCC) through engaging with FcγRIIIA (CD16) on NK cells and antibody-dependent cellular phagocytosis (ADCP) by macrophages. Interestingly, SLAMF7 is also expressed on cytolytic NK cells, which also express the requisite adaptor protein, EAT-2, to mediate activation signaling. Accumulating evidence indicates that antibody crosslinking of SLAMF7 on human and mouse NK cells can stimulate EAT-2-dependent activation of PLCγ, ERK, and intracellular calcium mobilization. The binding of SLAMF7 by elotuzumab can directly induce signal transduction in human NK cells, including co-stimulation of the calcium signaling triggered through other surface receptors, such as NKp46 and NKG2D. In RRMM patients, elotuzumab monotherapy did not produce objective responses, but did enhance the activity of approved standard of care therapies, including lenalidomide or bortezomib, which are known to enhance anti-tumor responses by NK cells. Taken together, these preclinical results and accumulating experience in the clinic provide compelling evidence that the mechanism of action of elotuzumab in MM patients involves the activation of NK cells through both CD16-mediated ADCC and direct co-stimulation via engagement with SLAMF7, as well as promoting ADCP by macrophages. We review the current understanding of how elotuzumab utilizes multiple mechanisms to facilitate immune-mediated attack of myeloma cells, as well as outline goals for future research.

CD26 is a potential therapeutic target by humanized monoclonal antibody for the treatment of multiple myeloma

CD26, a 110-kDa transmembrane glycoprotein that is expressed on several tumor cells including malignant lymphoma, has been implicated in tumorigenesis: however, little is known regarding its role in multiple myeloma (MM). Recently, we identified CD26 expression on human osteoclasts (OCs) and demonstrated that humanized IgG₁ monoclonal antibody targeting CD26, huCD26mAb, inhibits human OC differentiation. Herein, we show that CD26 expression was present on plasma cells in the bone marrow tissues of MM patients. In vitro immunostaining studies revealed that although CD26 expression was low or absent on MM cell lines cultured alone, it was intensely and uniformly expressed on MM cell lines co-cultured with OCs. The augmented CD26 expression in MM cells was exploited to enhance anti-MM efficacy of huCD26mAb via a substantial increase in antibody-dependent cytotoxicity (ADCC) but not complement-dependent cytotoxicity (CDC). Moreover, huCD26mAb in combination with novel agents synergistically enhanced huCD26mAb induced ADCC activity against CD26+ MM cells compared with each agent alone. huCD26mAb additionally reduced the ratio of the side population (SP) fraction in CD26+ MM cells by ADCC. Finally, huCD26mAb significantly reduced the MM tumor burden and OC formation in vivo. These results suggest that CD26 is a potential target molecule in MM and that huCD26mAb could act as a therapeutic agent.

2B4 (CD244, SLAMF4) and CS1 (CD319, SLAMF7) in systemic lupus erythematosus and cancer

Signaling Lymphocyte Activation Molecule (SLAM) family receptors are expressed on different types of hematopoietic cells and play important role in immune regulation in health and disease. 2B4 (CD244, SLAMF4) and CS1 (CD319, CRACC, SLAMF7) were originally identified as NK cell receptors regulating NK cell cytolytic activity. 2B4 is expressed on all NK cells, a subpopulation of T cells, monocytes and basophils. Unlike other activating and inhibitory receptors, 2B4 (CD244) interaction with its ligand CD48 has been shown to mediate both activating and inhibitory functions. Defective signaling via 2B4 due to mutations in signaling adaptor SAP contributes to X-linked lymphoproliferative Disease (XLP). Expression of 2B4 and CS1 are altered in systemic lupus erythematosus (SLE). CS1 is overexpressed in multiple myeloma (MM) and anti-CS1 mab (Elotuzumab/Empliciti) has been approved by FDA as a breakthrough drug for treatment for MM patients. CAR -T cells or CAR- NK cells containing full length CS1 or the signaling domain of 2B4 with TCR-ζ have shown promising results to treat cancer and autoimmune diseases.

How I treat the young patient with multiple myeloma

The treatment landscape for multiple myeloma has been transformed by the introduction of novel agents, including immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies. These have been shown to be more effective and generally better tolerated than conventional chemotherapy, with their introduction into clinical practice leading to improved survival. Furthermore, a better understanding of disease biology, improved diagnostic criteria, and the development of sensitive and specific tools for disease prognostication have contributed to better outcome. Treatment in the younger patient can now be individualized based on host and disease features with enhanced monitoring of response and use of high-sensitivity techniques for evaluating residual disease. The current standard of care has been significantly enhanced by novel agents with a paradigm shift toward optional or delayed autologous stem cell transplant as a reasonable choice in selected patients. Conversely, extended treatment with induction of remission followed by maintenance strategies is now a standard of care, conferring prolonged disease control with more manageable toxicities in both the short and long term, as well as improved quality of life.

CAR T Cells with Enhanced Sensitivity to B Cell Maturation Antigen for the Targeting of B Cell Non-Hodgkin's Lymphoma and Multiple Myeloma

Autologous T cells genetically modified with a chimeric antigen receptor (CAR) redirected at CD19 have potent activity in the treatment of B cell leukemia and B cell non-Hodgkin's lymphoma (B-NHL). Immunotherapies to treat multiple myeloma (MM) targeted the B cell maturation antigen (BCMA), which is expressed in most cases of MM. We developed a humanized CAR with specificity for BCMA based on our previously generated anti-BCMA monoclonal antibody. The targeting single-chain variable fragment (scFv) domain exhibited a binding affinity in the low nanomolar range, conferring T cells with high functional avidity. Redirecting T cells by this CAR allowed us to explore BCMA as an alternative target for mature B-NHLs. We validated BCMA expression in diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma, and chronic lymphocytic leukemia. BCMA CAR T cells triggered target cell lysis with an activation threshold in the range of 100 BCMA molecules, which allowed for an efficient eradication of B-NHL cells in vitro and in vivo. Our data corroborate BCMA is a suitable target in B cell tumors beyond MM, providing a novel therapeutic option for patients where BCMA is expressed at low abundance or where anti-CD19 immunotherapies have failed due to antigen loss.

Anti-CD38 and anti-SLAMF7: the future of myeloma immunotherapy

INTRODUCTION

the high expression of a number of surface antigens on malignant plasma cells, the bone marrow micro-environment and immune effector T cells, makes these appealing targets for immune therapy with monoclonal antibodies (mAbs). Areas covered: Two mAbs, anti-CD38 daratumumab (Dara) and anti-SLAMF7 elotuzumab (Elo), have achieved recent regulatory approval for relapsed or refractory MM (RRMM) and are currently being explored as possible treatment options in novel combinations and different settings. This review discusses the current landscape and possible development of anti-CD38 and anti-SLAMF7 mAbs. Expert commentary: Three phase III trials demonstrated a significant advantage in terms of response and PFS when Dara or Elo are combined with lenalidomide-dexamethsone (Rd) or bortezomib-dexamethsone (Vd), in comparison to doublet regimens, for patients with RRMM. Treatment algorithms including Dara- or Elo-based triplets may be defined on the basis of disease and patients' characteristics, as well as of their prior exposure to different classes of novel agents. Evaluation of these agents in new combination regimens, including second and third generation PIs and IMiDs, are under investigation. Moreover, use of mAbs in phases of the disease where the immune system is less compromised, such as newly diagnosed MM or even high-risk smoldering myeloma, appears logical.

Systematic review and meta-analysis of the efficacy and safety of novel monoclonal antibodies for treatment of relapsed/refractory multiple myeloma

Although two newly launched monoclonal antibodies (mAbs), elotuzumab and daratumumab, performed well in patients with relapsed or relapsed/refractory multiple myeloma (RRMM), their efficacy and safety remain uncertain. We therefore performed a systematic review and meta-analysis of the most recent clinical trials that evaluated elotuzumab and/or daratumumab for the treatment of patients with RRMM. Our meta-analysis included 13 clinical trials with 2,402 patients participating. The overall response rate (ORR) was 57% (95% confidence interval [CI]: 38-76%), and the at least very good partial response rate (VGPR) was 32% (95% CI: 19-46%). mAb-based regimens prolonged progression-free survival (PFS, hazard ratio: 0.52, 95% CI: 0.36-0.75) compared to non-mAb-based regimens. Additionally, the efficacy of triplet regimens was superior to that of single or doublet regimens. The same trend was observed in a subgroup analysis of daratumumab and elotuzumab. The most common grade 3/4 adverse events included neutropenia, lymphopenia, thrombocytopenia, anemia, leukopenia, pneumonia, and fatigue. Elotuzumab and daratumumab improved the ORR, at least VGPR, and PFS compared to non-mAb-based regimens. In a pooled analysis, both mAbs had promising efficacy and safety profiles, particularly in triplet regimens. The same trend was observed in daratumumab- and elotuzumab-based regimens. Daratumumab triplet therapy (daratumumab, lenalidomide, and dexamethasone) was superior to other triplet regimens for the treatment of RRMM, and daratumumab monotherapy was more effective than either single agent in heavily pretreated MM patients, suggesting CD38 is an effective target for treatment of RRMM. Additional clinical studies of elotuzumab and daratumumab will be required to validate these results.

Signaling lymphocytic activation molecules Slam and cancers: friends or foes?

Signaling Lymphocytic Activation Molecules (SLAM) family receptors are initially described in immune cells. These receptors recruit both activating and inhibitory SH2 domain containing proteins through their Immunoreceptor Tyrosine based Switch Motifs (ITSMs). Accumulating evidence suggest that the members of this family are intimately involved in different physiological and pathophysiological events such as regulation of immune responses and entry pathways of certain viruses. Recently, other functions of SLAM, principally in the pathophysiology of neoplastic transformations have also been deciphered. These new findings may prompt SLAM to be considered as new tumor markers, diagnostic tools or potential therapeutic targets for controlling the tumor progression. In this review, we summarize the major observations describing the implications and features of SLAM in oncology and discuss the therapeutic potential attributed to these molecules.

Elotuzumab for the Treatment of Relapsed or Refractory Multiple Myeloma, with Special Reference to its Modes of Action and SLAMF7 Signaling

Elotuzumab, targeting signaling lymphocytic activation molecule family 7 (SLAMF7), has been approved in combination with lenalidomide and dexamethasone (ELd) for relapsed/refractory multiple myeloma (MM) based on the findings of the phase III randomized trial ELOQUENT-2 (NCT01239797). Four-year follow-up analyses of ELOQUENT-2 have demonstrated that progression-free survival was 21% in ELd versus 14% in Ld. Elotuzumab binds a unique epitope on the membrane IgC2 domain of SLAMF7, exhibiting a dual mechanism of action: natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) and enhancement of NK cell activity. The ADCC is mediated through engagement between Fc portion of elotuzumab and FcgRIIIa/CD16 on NK cells. Enhanced NK cell cytotoxicity results from phosphorylation of the immunoreceptor tyrosine-based switch motif (ITSM) that is induced via elotuzumab binding and recruits the SLAM-associated adaptor protein EAT-2. The coupling of EAT-2 to the phospholipase Cg enzymes SH2 domain leads to enhanced Ca²⁺ influx and MAPK/Erk pathway activation, resulting in granule polarization and enhanced exocytosis in NK cells. Elotuzumab does not stimulate the proliferation of MM cells due to a lack of EAT-2. The inhibitory effects of elotuzumab on MM cell growth are not induced by the lack of CD45, even though SHP-2, SHP-1, SHIP-1, and Csk may be recruited to phosphorylated ITSM of SLAMF7. ELd improves PFS in patients with high-risk cytogenetics, i.e. t(4;14), del(17p), and 1q21 gain/amplification. Since the immune state is paralytic in advanced MM, the efficacy of ELd with minimal toxicity may bring forward for consideration of its use in the early stages of the disease.

Current developments in immunotherapy in the treatment of multiple myeloma

Multiple myeloma (MM) is the second most common hematologic malignancy and represents approximately 10% of all hematological neoplasms. Standard therapy consists of induction therapy followed by high-dose chemotherapy and autologous stem cell transplantation (ASCT) or, if ASCT cannot be performed, standard doublet, triplet, or quadruplet, novel agent-containing induction treatment until progression. Although MM is still regarded as mostly incurable by current standards, the development of several novel compounds, combination therapies, and immunotherapy approaches has raised great hopes about transforming MM into an indolent, chronic disease and possibly achieving a cure for individual patients. Several new inhibitory and immunological agents have been approved or are under intensive investigation and may lead to new therapeutic options for patients with relapsed/refractory MM, for patients ineligible for ASCT, and for patients after ASCT. Especially in the field of immunotherapy, including monoclonal antibodies, checkpoint inhibition, and chimeric antigen receptor T cells, current advances are rapid and highly promising. This review aims to summarize the newest and most promising immunotherapeutic agents for MM, their clinical efficacy, their adverse event (AE) profiles, and the ways in which these AEs can best be overcome or avoided. Cancer 2018;124:2075-85. © 2018 American Cancer Society.

Monoclonal Antibody Therapies for Hematological Malignancies: Not Just Lineage-Specific Targets

Today, monoclonal antibodies (mAbs) are a widespread and necessary tool for biomedical science. In the hematological cancer field, since rituximab became the first mAb approved by the Food and Drug Administration for the treatment of B-cell malignancies, a number of effective mAbs targeting lineage-specific antigens (LSAs) have been successfully developed. Non-LSAs (NLSAs) are molecules that are not restricted to specific leukocyte subsets or tissues but play relevant pathogenic roles in blood cancers including the development, proliferation, survival, and refractoriness to therapy of tumor cells. In consequence, efforts to target NLSAs have resulted in a plethora of mAbs-marketed or in development-to achieve different goals like neutralizing oncogenic pathways, blocking tumor-related chemotactic pathways, mobilizing malignant cells from tumor microenvironment to peripheral blood, modulating immune-checkpoints, or delivering cytotoxic drugs into tumor cells. Here, we extensively review several novel mAbs directed against NLSAs undergoing clinical evaluation for treating hematological malignancies. The review focuses on the structure of these antibodies, proposed mechanisms of action, efficacy and safety profile in clinical studies, and their potential applications in the treatment of hematological malignancies.

Immune Therapies in Multiple Myeloma

Treatment paradigms have changed rapidly for multiple myeloma, and immune therapies have taken center stage. Advances in therapies for myeloma have led to a dramatic improvement in the survival of patients with this incurable malignancy. The immune system is significantly impaired in patients with myeloma as a result of the disease leading to suppression of normal plasma cells as well the negative effects on cellular immunity. Given this scenario, immune approaches have not been successful until recently. Monoclonal antibodies directed against CD38 (daratumumab) and SLAMF7 (elotuzumab) are already in the clinic, and several other antibodies directed against different plasma cell antigens are under evaluation. Although immune checkpoint inhibition with PD-1 inhibitors had no clinical efficacy when the inhibitors were used as single agents, it has led to some dramatic results when the inhibitors are combined with immunomodulatory drugs such as lenalidomide and pomalidomide. Vaccination strategies have shown in vivo immune responses but no clear clinical efficacy. Newer approaches to vaccination with multiple antigens, used in combinations with immunomodulatory drugs and in the setting of minimal residual disease, have all increased possibility of this approach succeeding. Ex vivo effector cell expansion also appears to be promising and is in clinical trials. Finally, a chimeric antigen receptor T-cell approach appears to have some promise based on isolated reports of success and remains an area of intense investigation. Immune-based approaches can potentially augment or even supplant some of the current approaches and, given the low toxicity profile, may hold great potential in the early treatment of precursor-stage diseases. Clin Cancer Res; 22(22); 5453-60. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "MULTIPLE MYELOMA MULTIPLYING THERAPIES".

The role of elotuzumab in the treatment of relapsed or refractory multiple myeloma

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy and safety, cost, and place in therapy of elotuzumab for treatment of relapsed or refractory multiple myeloma (MM) are reviewed.

SUMMARY

Elotuzumab is a humanized monoclonal antibody that targets the signaling lymphocytic activation molecule (SLAM) protein SLAMF7 and facilitates an antibody-dependent cellular cytotoxicity interaction between myeloma cells and natural killer cells. Elotuzumab has U.S. marketing approval for use in combination with lenalidomide and dexamethasone in patients with relapsed or refractory MM who have received 1-3 previous therapies; this regimen is among the preferred regimens for relapsed or refractory MM recommended by the National Comprehensive Cancer Network (NCCN). A Phase III trial involving 321 patients demonstrated a median progression-free survival duration of 19.4 months with elotuzumab plus lenalidomide and dexamethasone versus 14.9 months with lenalidomide and dexamethasone alone (hazard ratio for progression or death, 0.70; 95% confidence interval, 0.57-0.85; p < 0.001). Common adverse effects of elotuzumab-lenalidomide-dexamethasone therapy include hematologic toxicities, fatigue, pyrexia, diarrhea, constipation, muscle spasms, and cough. Elotuzumab plus bortezomib and dexamethasone is an NCCN-recommended alternative option for relapsed or refractory MM.

CONCLUSION

While elotuzumab plus lenalidomide and dexamethasone is a promising regimen for patients with MM, it is only one of several regimens recommended by NCCN for relapsed or refractory MM. Key factors in patient selection for elotuzumab therapy include adverse effects, prior treatments received, and cost considerations.

Monoclonal Antibody: A New Treatment Strategy against Multiple Myeloma

2015 was a groundbreaking year for the multiple myeloma community partly due to the breakthrough approval of the first two monoclonal antibodies in the treatment for patients with relapsed and refractory disease. Despite early disappointments, monoclonal antibodies targeting CD38 (daratumumab) and signaling lymphocytic activation molecule F7 (SLAMF7) (elotuzumab) have become available for patients with multiple myeloma in the same year. Specifically, phase 3 clinical trials of combination therapies incorporating daratumumab or elotuzumab indicate both efficacy and a very favorable toxicity profile. These therapeutic monoclonal antibodies for multiple myeloma can kill target cells via antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent phagocytosis, as well as by direct blockade of signaling cascades. In addition, their immunomodulatory effects may simultaneously inhibit the immunosuppressive bone marrow microenvironment and restore the key function of immune effector cells. In this review, we focus on monoclonal antibodies that have shown clinical efficacy or promising preclinical anti-multiple myeloma activities that warrant further clinical development. We summarize mechanisms that account for the in vitro and in vivo anti-myeloma effects of these monoclonal antibodies, as well as relevant preclinical and clinical results. Monoclonal antibody-based immunotherapies have already and will continue to transform the treatment landscape in multiple myeloma.

A review discussing elotuzumab and its use in the second-line plus treatment of multiple myeloma

Monoclonal antibodies (mAb) represent a new frontier to treat newly diagnosed and relapsed-refractory multiple myeloma (MM). Elotuzumab, an mAb targeted SLAM7 in the plasma cells and natural killer cells surface, is the first mAb approved for the treatment of relapsed-refractory MM in combination with lenalidomide and dexamethasone. This approval was the final result of several preclinical and Phase I-II clinical studies leading to ELOQUENT-2 Phase III trial that demonstrated that elotuzumab adds a significant and durable value to standard therapy, paved the way of this new treatment strategy for MM. In this review we will describe elotuzumab mechanisms of action, clinical pharmacology and clinical studies that have led to these developments.

SLAMF7-CAR T cells eliminate myeloma and confer selective fratricide of SLAMF7+ normal lymphocytes

SLAMF7 is under intense investigation as a target for immunotherapy in multiple myeloma. In this study, we redirected the specificity of T cells to SLAMF7 through expression of a chimeric antigen receptor (CAR) derived from the huLuc63 antibody (elotuzumab) and demonstrate that SLAMF7-CAR T cells prepared from patients and healthy donors confer potent antimyeloma reactivity. We confirmed uniform, high-level expression of SLAMF7 on malignant plasma cells in previously untreated and in relapsed/refractory (R/R) myeloma patients who had received previous treatment with proteasome inhibitors and immunomodulatory drugs. Consequently, SLAMF7-CAR T cells conferred rapid cytolysis of previously untreated and R/R primary myeloma cells in vitro. In addition, a single administration of SLAMF7-CAR T cells led to resolution of medullary and extramedullary myeloma manifestations in a murine xenograft model in vivo. SLAMF7 is expressed on a fraction of normal lymphocytes, including subsets of natural killer (NK) cells, T cells, and B cells. After modification with the SLAMF7-CAR, both CD8⁺ and CD4⁺ T cells rapidly acquired and maintained a SLAMF7^- phenotype and could be readily expanded to therapeutically relevant cell doses. We analyzed the recognition of normal lymphocytes by SLAMF7-CAR T cells and show that they induce selective fratricide of SLAMF7^+/high NK cells, CD4⁺ and CD8⁺ T cells, and B cells. Importantly, however, the fratricide conferred by SLAMF7-CAR T cells spares the SLAMF7^-/low fraction in each cell subset and preserves functional lymphocytes, including virus-specific T cells. In aggregate, our data illustrate the potential use of SLAMF7-CAR T-cell therapy as an effective treatment against multiple myeloma and provide novel insights into the consequences of targeting SLAMF7 for the normal lymphocyte compartment.

Emerging drugs and combinations to treat multiple myeloma

In the past few years, multiple targeted therapies and immunotherapies including second generation immunomodulatory drugs (pomalidomide) and proteasome inhibitors (carfilzomib, ixazomib), monoclonal antibodies and checkpoint inhibitors were approved for the treatment of myeloma or entered advanced phases of clinical testing. These agents showed significant activity in advanced myeloma and increased the available treatment strategies. Pomalidomide is well-tolerated and effective in patients with relapsed/refractory multiple myeloma who have exhausted any possible treatment with lenalidomide and bortezomib. Carfilzomib, a second-generation proteasome inhibitor, is active as a single agent and in combination with other anti-myeloma agents. Ixazomib is the first oral proteasome inhibitor to be evaluated in myeloma and is associated with a good safety profile and anti-myeloma activity in relapsed/refractory patients, even in those refractory to bortezomib. Monoclonal antibodies and immune checkpoint inhibitors are likely to play a major role in the treatment of myeloma over the next decade. In phase 3 studies, triplet regimens based on these agents combined with a backbone therapy (including lenalidomide, pomalidomide or bortezomib) were more efficacious than doublet regimens in patients with relapsed/refractory multiple myeloma, with limited additional toxic effects. This paper aims to provide an overview of the recent use of these agents for the treatment of myeloma, in particular focusing on the role of multi-agent combinations.

CS1 (SLAMF7, CD319) is an effective immunotherapeutic target for multiple myeloma

CS1 (also known as CD319, CRACC and SLAMF7) was identified as an NK cell receptor regulating immune functions. It is also expressed on B cells, T cells, Dendritic cells, NK-T cells, and monocytes. CS1 is overexpressed in multiple myeloma and makes it a target for immunotherapy. A humanized anti-CS1 antibody, Elotuzumab or Empliciti has shown promising results in clinical studies. This review focuses on the biology of CS1 in NK and other hematopoietic cells and multiple myeloma. Anti-CS1 mAb can activate natural cytotoxicity of NK cells as well as enhance ADCC (antibody-dependent cell-mediated cytotoxicity) and thus makes an effective target for immunotherapy of MM.

Emerging combination therapies for the management of multiple myeloma: the role of elotuzumab

Treatment options for patients with multiple myeloma (MM) have increased during the past decade. Despite the significant advances, challenges remain on which combination strategies will provide the optimal response for any given patient. Defining optimal combination strategies and corresponding companion diagnostics, that will guide clinical decisions are required to target relapsed or refractory multiple myeloma (RRMM) in order to improve disease progression, survival and quality of life for patients with MM. Elotuzumab is a humanized monoclonal antibody that targets signaling lymphocytic activation molecule F7 (SLAMF7), approved by the US Food and Drug Administration (FDA) in 2015 and the European Medicines Agency in 2016 for the treatment of MM. SLAMF7 is expressed in normal and malignant plasma cells and has lower expression on natural killer (NK) cells. Experimental evidence indicates that elotuzumab exhibits anti-myeloma activity through 1) antibody-dependent cell-mediated cytotoxicity, 2) enhancing NK cells cytotoxicity and 3) interfering with adhesion of MM cells to bone marrow stem cells (BMSCs). Although elotuzumab has no single agent activity in patients with RRMM who have received one to three prior therapies, the combination of elotuzumab with anti-myeloma agents, such as immunomodulatory drugs-lenalidomide, or proteasome inhibitors (PIs)-bortezomib, remarkably improved the overall response rates and progression-free survival in MM patients with only minimal incremental toxicity. In brief, the clinical data for elotuzumab indicate that targeting SLAMF7 in combination with the use of conventional therapies is feasible and effective with a tolerable safety profile for the treatment of RRMM.

Current and developing synthetic pharmacotherapy for treating relapsed/refractory multiple myeloma

INTRODUCTION

The introduction of novel agents has significantly improved multiple myeloma (MM) patient outcome during the last two decades. MM received the most drug approvals for any one malignancy during this time period, both in the United States as well as in Europe. Areas covered: Proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies are prototype drug classes, which target both specific MM cell functions, as well as the tumor supportive bone marrow microenvironment, and represent current cornerstones of MM therapy. Importantly, the unprecedented extent and frequency of durable responses, in relapsed/refractory multiple myeloma (RRMM), in particular, is predominantly based on the combinatorial use of these agents with conventional chemotherapeutics or representatives of other drug classes. This article will summarize past landmark discoveries in MM that led to the dramatic progress of today's clinical practice. Moreover, developing strategies will be discussed that are likely to yet improve patient outcome even further. Expert opinion: Despite significant therapeutic advancements, MM remains an incurable disease. With several novel agents in the preclinical and early clinical pipeline, among those novel CD38 and BCMA mAbs, immune checkpoint inhibitors, as well as ricolinostat, selinexor, venetoclax, CAR-T cells, and vaccines, further advances in MM patient outcome are expected in the near future.

Elotuzumab as a novel anti-myeloma immunotherapy

Treatment of multiple myeloma has undergone significant change in the last decade with the introduction of new immunomodulatory agents, proteasome inhibitors, and immunotherapeutic approaches. Elotuzumab is a humanized monoclonal antibody targeting CS1, which is a member of the SLAM (Signaling Lymphocyte Activation Molecule) family of proteins, expressed on the surface of myeloma plasma cells. Here we review the preclinical investigations that led to the development of elotuzumab and the clinical studies that resulted in its approval for the treatment of relapsed/refractory multiple myeloma. Although preclinical data looked very promising, elotuzumab monotherapy did not result in objective clinical responses in patients with relapsed/refractory multiple myeloma. However, combination treatment with immunomodulators and proteasome inhibitors resulted in substantial clinical activity in relapsed/refractory MM. Currently, there are several clinical trials ongoing investigating the role of elotuzumab in newly diagnosed myeloma patients and in patients receiving maintenance therapy.

Role of the Immune Response in Disease Progression and Therapy in Multiple Myeloma

Multiple myeloma (MM) is a hematologic cancer derived from malignant plasma cells within the bone marrow. Unlike most solid tumors, which originate from epithelial cells, the myeloma tumor is a plasma cell derived from the lymphoid cell lineage originating from a post-germinal B-cell. As such, the MM plasma cell represents an integral component of the immune system in terms of both antibody production and antigen presentation, albeit not efficiently. This fundamental difference has significant implications when one considers the implications of immunotherapy. In the case of lymphoid malignancies such as myeloma, immune-based strategies must take into consideration this important difference, potentially necessitating immunotherapy targeted toward MM to be altered from that targeted at solid tumors. Typically, the immune system "surveys" cells within our body and is able to recognize and attack cancerous cells that may arise. However, some cancer cells are able to evade immune surveillance and continue to flourish, causing disease. The major mechanism leading to an effective tumor-specific response is one that enables effective antigen processing and presentation with subsequent T-cell activation, expansion, and effective trafficking to the tumor site. Plasma cells employ several mechanisms to escape immune surveillance which include altered interactions with T-cells, DCs, bone marrow stromal cells (BMSC's), and natural killer cells (NK Cells) that can be mediated by immunosuppressive cells such as and myeloid-derived suppressor cells (MDSC's) and cytokines such as IL-10, TGFβ, and IL-6 as well as down-regulation of the antigen processing machinery. Many therapies have been developed to reestablish a functional immune system in MM patients. These include adoptive T-cell therapies to deliver more tumor-specific T-cells, vaccines to increase the tumor-specific precursor frequency of the endogenous T-cell population, immunomodulatory agents (IMiDs) such as thalidomide and lenalidomide to enhance global endogenous immunity, immunostimulatory cytokines, and antibodies to specifically target tumor-specific cell-surface proteins or cytokines. This review will dissect these various approaches currently being explored in MM as well as highlight some future directions for myeloma-specific immune-based strategies.

Daratumumab, Elotuzumab, and the Development of Therapeutic Monoclonal Antibodies in Multiple Myeloma

There has been substantial progress in clinical outcomes for patients with multiple myeloma (MM). This encouraging trend derives in large part from the increasing number of effective therapeutic options and the ability because of this to achieve higher quality responses to treatment. The approval of both daratumumab and of elotuzumab in combination with lenalidomide and dexamethasone, in late 2015, was a notable achievement in the field, as daratumumab and elotuzumab represent the first monoclonal antibodies available for use in MM. Given their unique mechanisms of action and favorable side effect profiles, daratumumab and elotuzumab have considerable potential as therapeutic partners with agents in other drug classes and in different clinical settings ranging from newly diagnosed to relapsed disease. This review discusses the development of daratumumab and elotuzumab as well as other monoclonal antibodies currently being evaluated for use in MM.