APRIL and BCMA promote human multiple myeloma growth and immunosuppression in the bone marrow microenvironment

B-cell maturation antigen directed monoclonal antibody therapies for multiple myeloma

Multiple myeloma affects 30,000 new patients in the USA yearly, with 5-year median overall survival rates of 82, 62 and 40% for patients in groups I, II and III of the revised international staging system. Novel therapeutic and prognostic tools are changing the way we treat patients with this historically difficult to manage condition. B-cell maturation antigen (BCMA) represents an ideal therapeutic target in myeloma because of its high expression rate and high specificity for myeloma cells. Preclinical data indicate that anti-BCMA monoclonal antibody therapies are highly potent, and initial data from Phase I clinical trials indicate that these drugs are well tolerated. Numerous ongoing Phase I and II clinical trials of anti-BCMA monoclonal antibodies are currently under way.

Survival of Long-Lived Plasma Cells (LLPC): Piecing Together the Puzzle

Durable humoral immunity is dependent upon the generation of antigen-specific antibody titers, produced by non-proliferating bone marrow resident long-lived plasma cells (LLPC). Longevity is the hallmark of LLPC, but why and how they survive and function for years after antigen exposure is only beginning to be understood. LLPC are not intrinsically long-lived; they require continuous signals from the LLPC niche to survive. Signals unique to LLPC survival (vs. PC survival in general) most notably include those that upregulate the anti-apoptotic factor Mcl-1 and activation of the CD28 receptor expressed on LLPC. Other potential factors include expression of BCMA, upregulation of the transcription factor ZBTB20, and upregulation of the enzyme ENPP1. Metabolic fitness is another key component of LLPC longevity, facilitating the diversion of glucose to generate pyruvate during times of stress to facilitate long term survival. A third major component of LLPC survival is the microenvironment/LLPC niche itself. Cellular partners such as stromal cells, dendritic cells, and T regulatory cells establish a niche for LLPC and drive survival signaling by expressing ligands such as CD80/CD86 for CD28 and producing soluble and stromal factors that contribute to LLPC longevity. These findings have led to the current paradigm wherein both intrinsic and extrinsic mechanisms are required for the survival of LLPC. Here we outline this diverse network of signals and highlight the mechanisms thought to regulate and promote the survival of LLPC. Understanding this network of signals has direct implications in increasing our basic understanding of plasma cell biology, but also in vaccine and therapeutic drug development to address the pathologies that can arise from this subset.

Heme oxygenase-1 attenuates the inhibitory effect of bortezomib against the APRIL-NF-κB-CCL3 signaling pathways in multiple myeloma cells: Corelated with bortezomib tolerance in multiple myeloma

Osteoclasts (OCs) play an essential role in bone destruction in patients with multiple myeloma (MM). Bortezomib can ameliorate bone destruction in patients with MM, but advanced MM often resists bortezomib. We studied the molecular mechanisms of bortezomib tolerance in MM. The expression of the MM-related genes in newly diagnosed patients with MM and normal donors were studied. C-C motif chemokine ligand 3 (CCL3) is a cytokine involved in the differentiation of OCs, and its expression is closely related to APRIL (a proliferation-inducing ligand). We found that bortezomib treatment inhibited APRIL and CCL3. But the heme oxygenase-1 (HO-1) activator hemin attenuated the inhibitory effects of bortezomib on APRIL and CCL3. We induced mononuclear cells to differentiate into OCs, and the enzyme-linked immunosorbent assay showed that the more OCs differentiated, the higher the levels CCL3 secretions detected. Animal experiments showed that hemin promoted MM cell infiltration in mice. The weight and survival rate of tumor mice were associated with HO-1 expression. Immunohistochemical staining showed that HO-1, APRIL, and CCL3 staining were positively stained in the tumor infiltrating sites. Then, MM cells were transfected with L-HO-1/si-HO-1 expression vectors and cultured with an nuclear factor (NF)-kappa B (κB) pathway inhibitor, QNZ. The results showed that HO-1 was the upstream gene of APRIL, NF-κB, and CCL3. We showed that HO-1 could attenuate the inhibitory effect of bortezomib against the APRIL-NF-κB-CCL3 signaling pathways in MM cells, and the tolerance of MM cells to bortezomib and the promotion of bone destruction are related to HO-1.

Exploratory trial of a biepitopic CAR T-targeting B cell maturation antigen in relapsed/refractory multiple myeloma

Relapsed and refractory (R/R) multiple myeloma (MM) patients have very poor prognosis. Chimeric antigen receptor modified T (CAR T) cells is an emerging approach in treating hematopoietic malignancies. Here we conducted the clinical trial of a biepitope-targeting CAR T against B cell maturation antigen (BCMA) (LCAR-B38M) in 17 R/R MM cases. CAR T cells were i.v. infused after lymphodepleting chemotherapy. Two delivery methods, three infusions versus one infusion of the total CAR T dose, were tested in, respectively, 8 and 9 cases. No response differences were noted among the two delivery subgroups. Together, after CAR T cell infusion, 10 cases experienced a mild cytokine release syndrome (CRS), 6 had severe but manageable CRS, and 1 died of a very severe toxic reaction. The abundance of BCMA and cytogenetic marker del(17p) and the elevation of IL-6 were the key indicators for severe CRS. Among 17 cases, the overall response rate was 88.2%, with 13 achieving stringent complete response (sCR) and 2 reaching very good partial response (VGPR), while 1 was a nonresponder. With a median follow-up of 417 days, 8 patients remained in sCR or VGPR, whereas 6 relapsed after sCR and 1 had progressive disease (PD) after VGPR. CAR T cells were high in most cases with stable response but low in 6 out of 7 relapse/PD cases. Notably, positive anti-CAR antibody constituted a high-risk factor for relapse/PD, and patients who received prior autologous hematopoietic stem cell transplantation had more durable response. Thus, biepitopic CAR T against BCMA represents a promising therapy for R/R MM, while most adverse effects are clinically manageable.

Preclinical Evaluation of Allogeneic CAR T Cells Targeting BCMA for the Treatment of Multiple Myeloma

Clinical success of autologous CD19-directed chimeric antigen receptor T cells (CAR Ts) in acute lymphoblastic leukemia and non-Hodgkin lymphoma suggests that CAR Ts may be a promising therapy for hematological malignancies, including multiple myeloma. However, autologous CAR T therapies have limitations that may impact clinical use, including lengthy vein-to-vein time and manufacturing constraints. Allogeneic CAR T (AlloCAR T) therapies may overcome these innate limitations of autologous CAR T therapies. Unlike autologous cell therapies, AlloCAR T therapies employ healthy donor T cells that are isolated in a manufacturing facility, engineered to express CARs with specificity for a tumor-associated antigen, and modified using gene-editing technology to limit T cell receptor (TCR)-mediated immune responses. Here, transcription activator-like effector nuclease (TALEN) gene editing of B cell maturation antigen (BCMA) CAR Ts was used to confer lymphodepletion resistance and reduced graft-versus-host disease (GvHD) potential. The safety profile of allogeneic BCMA CAR Ts was further enhanced by incorporating a CD20 mimotope-based intra-CAR off switch enabling effective CAR T elimination in the presence of rituximab. Allogeneic BCMA CAR Ts induced sustained antitumor responses in mice supplemented with human cytokines, and, most importantly, maintained their phenotype and potency after scale-up manufacturing. This novel off-the-shelf allogeneic BCMA CAR T product is a promising candidate for clinical evaluation.

B cell maturation antigen-specific CAR T cells are clinically active in multiple myeloma

BACKGROUND

Chimeric antigen receptor (CAR) T cells are a promising therapy for hematologic malignancies. B-cell maturation antigen (BCMA) is a rational target in multiple myeloma (MM).

METHODS

We conducted a phase I study of autologous T cells lentivirally-transduced with a fully-human, BCMA-specific CAR containing CD3ζ and 4-1BB signaling domains (CART-BCMA), in subjects with relapsed/refractory MM. Twenty-five subjects were treated in 3 cohorts: 1) 1-5 x 108 CART-BCMA cells alone; 2) Cyclophosphamide (Cy) 1.5 g/m2 + 1-5 x 107 CART-BCMA cells; and 3) Cy 1.5 g/m2 + 1-5 x 108 CART-BCMA cells. No pre-specified BCMA expression level was required.

RESULTS

CART-BCMA cells were manufactured and expanded in all subjects. Toxicities included cytokine release syndrome and neurotoxicity, which were grade 3-4 in 8 (32%) and 3 (12%) subjects, respectively, and reversible. One subject died at day 24 from candidemia and progressive myeloma, following treatment for severe CRS and encephalopathy. Responses (based on treated subjects) were seen in 4/9 (44%) in cohort 1, 1/5 (20%) in cohort 2, and 7/11 (64%) in cohort 3, including 5 partial, 5 very good partial, and 2 complete responses, 3 of which were ongoing at 11, 14, and 32 months. Decreased BCMA expression on residual MM cells was noted in responders; expression increased at progression in most. Responses and CART-BCMA expansion were associated with CD4:CD8 T cell ratio and frequency of CD45RO-CD27+CD8+ T cells in the pre-manufacturing leukapheresis product.

CONCLUSION

CART-BCMA infusions with or without lymphodepleting chemotherapy are clinically active in heavily-pretreated MM patients.

TRIAL REGISTRATION

NCT02546167.

FUNDING

University of Pennsylvania-Novartis Alliance and NIH.

Anti-BCMA antibodies in the future management of multiple myeloma

INTRODUCTION

B-cell maturation antigen (BCMA) belongs to the tumor necrosis factor receptor family and is expressed on late B-cells and plasma cells. Serum BCMA is elevated in patients with multiple myeloma (MM) and chronic lymphocytic leukemia (CLL), and might represent a novel prognostic and monitoring tool. Serum BCMA levels can predict both progression free survival (PFS) and overall survival (OS). Several therapeutic strategies are currently under investigation including BCMA-directed monoclonal Abs (either naked or with drug conjugates, and bispecific Abs) and cellular T-cell therapies (chimeric antigen receptor T-cells) with impressive clinical results. Areas covered: This review aims to present the mechanisms of action and the available data on efficacy and safety of therapies targeting BCMA. Expert opinion: The preliminary preclinical and clinical results from the phase 1 and 2 studies have demonstrated significant activity of the anti-BCMA therapeutic strategies. The main toxicities induced include Cytokine Release Syndrome (CRS) and ocular toxicity. The management of these adverse events remains currently an issue of controversy.

Arrayed molecular barcoding identifies TNFSF13 as a positive regulator of acute myeloid leukemia-initiating cells

Dysregulation of cytokines in the bone marrow (BM) microenvironment promotes acute myeloid leukemia (AML) cell growth. Due to the complexity and low throughput of in vivo stem-cell based assays, studying the role of cytokines in the BM niche in a screening setting is challenging. Here, we developed an ex vivo cytokine screen using 11 arrayed molecular barcodes, allowing for a competitive in vivo readout of leukemia-initiating capacity. With this approach, we assessed the effect of 114 murine cytokines on MLL-AF9 AML mouse cells and identified the tumor necrosis factor ligand superfamily member 13 (TNFSF13) as a positive regulator of leukemia-initiating cells. By using Tnfsf13^−/− recipient mice, we confirmed that TNFSF13 supports leukemia initiation also under physiological conditions. TNFSF13 was secreted by normal myeloid cells but not by leukemia mouse cells, suggesting that mature myeloid BM cells support leukemia cells by secreting TNFSF13. TNFSF13 supported leukemia cell proliferation in an NF-κB-dependent manner by binding TNFRSF17 and suppressed apoptosis. Moreover, TNFSF13 supported the growth and survival of several human myeloid leukemia cell lines, demonstrating that our findings translate to human disease. Taken together, using arrayed molecular barcoding, we identified a previously unrecognized role of TNFSF13 as a positive regulator of AML-initiating cells. The arrayed barcoded screening methodology is not limited to cytokines and leukemia, but can be extended to other types of ex vivo screens, where a multiplexed in vivo read-out of stem cell functionality is needed.

The future of myeloma precision medicine: integrating the compendium of known drug resistance mechanisms with emerging tumor profiling technologies

Multiple myeloma (MM) is a hematologic malignancy that is considered mostly incurable in large part due to the inability of standard of care therapies to overcome refractory disease and inevitable drug-resistant relapse. The post-genomic era has been a productive period of discovery where modern sequencing methods have been applied to large MM patient cohorts to modernize our current perception of myeloma pathobiology and establish an appreciation for the vast heterogeneity that exists between and within MM patients. Numerous pre-clinical studies conducted in the last two decades have unveiled a compendium of mechanisms by which malignant plasma cells can escape standard therapies, many of which have potentially quantifiable biomarkers. Exhaustive pre-clinical efforts have evaluated countless putative anti-MM therapeutic agents and many of these have begun to enter clinical trial evaluation. While the palette of available anti-MM therapies is continuing to expand it is also clear that malignant plasma cells still have mechanistic avenues by which they can evade even the most promising new therapies. It is therefore becoming increasingly clear that there is an outstanding need to develop and employ precision medicine strategies in MM management that harness emerging tumor profiling technologies to identify biomarkers that predict efficacy or resistance within an individual's sub-clonally heterogeneous tumor. In this review we present an updated overview of broad classes of therapeutic resistance mechanisms and describe selected examples of putative biomarkers. We also outline several emerging tumor profiling technologies that have the potential to accurately quantify biomarkers for therapeutic sensitivity and resistance at genomic, transcriptomic and proteomic levels. Finally, we comment on the future of implementation for precision medicine strategies in MM and the clear need for a paradigm shift in clinical trial design and disease management.

Immunotherapy in myeloma: how far have we come?

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

Forsythiaside inhibited titanium particle-induced inflammation via the NF-κB signaling pathway and RANKL-induced osteoclastogenesis and titanium particle-induced periprosthetic osteolysis via JNK, p38, and ERK signaling pathways

Wear particle-induced periprosthetic osteolysis is the primary complication of the total joint replacement; however, no conservative treatment except for reversal surgery is available for this disease. During the past decade, Chinese herbal medicines have been widely investigated to inhibit osteoclast differentiation, which may exhibit the potential to treat wear particle-induced periprosthetic osteolysis. The present study was aimed at the investigation of the effects of forsythiaside on osteocytes. The current data revealed that the forsythiaside treatment notably inhibited the titanium (Ti) particle-induced inflammation through impaired NF-κB signaling, thereby inhibiting TNF-α and IL-1β. In addition, the in vitro study demonstrated that forsythiaside effectively prevented the RANKL-induced differentiation of osteoclasts and inhibited the expression of osteoclast-specific genes in osteoclasts via inhibition of the JNK signaling pathway. The in vivo study of Ti particle-induced implant-associated osteolysis indicated that forsythiaside could also inhibit osteoclastogenesis. In summary, forsythiaside could inhibit osteoclastogenesis and particle-induced inflammation, resulting in decreased secretion of inflammatory cytokines such as TNF-α and IL-1β. On the other hand, forsythiaside could inhibit RANKL-induced osteoclastogenesis and Ti particle-induced periprosthetic osteolysis via JNK, ERK and p38 signaling pathways. Both the abovementioned biofunctions of forsythiaside contributed to the implant-associated particle-induced osteolysis. Thus, forsythiaside can act as a candidate drug for the precaution of implant-associated particle-induced osteolysis.

Forsythiaside can act as a candidate drug for the precaution of implant-associated particle-induced osteolysis.

Therapeutic antibodies for multiple myeloma

In recent years, many antibody therapies for multiple myeloma have been developed. Antibodies against SLAMF7, CD38, B-cell maturation antigen and PD-1 have been developed and clinical trials are currently under way. As of July 2017, antibodies clinically available in Japan for the treatment of multiple myeloma are elotuzumab against SLAMF7 and daratumumab against CD38. Elotuzumab is a humanized IgG1-kappa monoclonal antibody targeting human SLAMF7. SLAMF7 is a cell surface glycoprotein receptor highly expressed on multiple myeloma cells, and it is also expressed on natural killer cells and is critical for natural killer function. Binding of elotuzumab to natural killer cells leads to activation of natural killer cells, resulting in antibody-dependent cell-mediated cytotoxicity of elotuzumab-bound multiple myeloma cells, but not complement-dependent cytotoxicity. The result of a randomized phase III trial of elotuzumab+lenalidomide+dexamethasone (ELOQUENT-2) reduced the risk of disease progression/death by 30% vs lenalidomide+dexamethasone in relapse/refractory multiple myeloma. Daratumumab is a human anti-CD38 IgG1-kappa antibody. CD38 is expressed ubiquitously virtually in all tissues that are highly expressed on plasma cells and it represents an attractive target for immunotherapy using monoclonal antibodies. In the phase III CASTOR trial, patients treated with daratumumab+bortezomib+dexamethasone had a better CR rate and progression-free survival rate compared with bortezomib+dexamethasone-treated patients (29% vs 10%, median progression-free survival: 16.7 vs 7.1 months, respectively). Moreover, in the phase III POLLUX trial, patients treated with daratumumab+lenalidomide+dexamethasone had a better response and progression-free survival (CRR or better: 55% vs 23%, 30-month progression-free survival: 58% vs 35%), compared with lenalidomide+dexamethasone-treated patients.

Monoclonal Antibodies for the Treatment of Multiple Myeloma: An Update

The past two decades have seen a revolution in multiple myeloma (MM) therapy with the introduction of several small molecules, mostly orally effective, whose mechanisms are based on proteasome inhibition, histone deacetylase (HDAC) blockade, and immunomodulation. Immunotherapeutic approaches to MM treatment using monoclonal antibodies (mAbs), while long in development, began to reap success with the identification of CD38 and SLAMF7 as suitable targets for development, culminating in the 2015 Food and Drug Administration (FDA) approval of daratumumab and elotuzumab, respectively. This review highlights additional mAbs now in the developmental pipeline. Isatuximab, another anti-CD38 mAb, currently is under study in four phase III trials and may offer certain advantages over daratumumab. Several antibody-drug conjugates (ADCs) in the early stages of development are described, including JNJ-63723283, which has attained FDA breakthrough status for MM. Other mAbs described in this review include denosumab, recently approved for myeloma-associated bone loss, and checkpoint inhibitors, although the future status of the latter combined with immunomodulators has been clouded by unacceptably high death rates that caused the FDA to issue clinical holds on several of these trials. Also highlighted are the therapies based on the B Cell Maturation Antigen (BCMA), another very promising target for anti-myeloma development.

Targeting B-cell maturation antigen with GSK2857916 antibody-drug conjugate in relapsed or refractory multiple myeloma (BMA117159): a dose escalation and expansion phase 1 trial

BACKGROUND

B-cell maturation antigen (BCMA) is a cell-surface receptor of the tumour necrosis superfamily required for plasma cell survival. BMCA is universally detected on patient-derived myeloma cells and has emerged as a selective antigen to be targeted by novel treatments in multiple myeloma. We assessed the safety, tolerability, and preliminary clinical activity of GSK2857916, a novel anti-BCMA antibody conjugated to microtubule-disrupting agent monomethyl auristatin F, in patients with relapsed and refractory multiple myeloma.

METHODS

We did an international, multicentre, open-label, first-in-human phase 1 study with dose escalation (part 1) and dose expansion (part 2) phases, at nine centres in the USA, Canada, and the UK. Adults with histologically or cytologically confirmed multiple myeloma, Eastern Cooperative Oncology Group performance status 0 or 1, and progressive disease after stem cell transplantation, alkylators, proteasome inhibitors, and immunomodulators were recruited for this study. In part 1, patients received GSK2857916 (0·03-4·60 mg/kg) through 1 h intravenous infusions once every 3 weeks. In part 2, patients received the selected recommended phase 2 dose of GSK2857916 (3·40 mg/kg) once every 3 weeks. Primary endpoints were maximum tolerated dose and recommended phase 2 dose. Secondary endpoints for part 2 included preliminary anti-cancer clinical activity. All patients who received one or more doses were included in this prespecified administrative interim analysis (data cutoff date June 26, 2017), which was done for internal purposes. This study is registered with ClinicalTrials.gov, number NCT02064387, and is ongoing, but closed for recruitment.

FINDINGS

Between July 29, 2014, and Feb 21, 2017, we treated 73 patients: 38 patients in the dose-escalation part 1 and 35 patients in the dose-expansion part 2. There were no dose-limiting toxicities and no maximum tolerated dose was identified in part 1. On the basis of safety and clinical activity, we selected 3·40 mg/kg as the recommended phase 2 dose. Corneal events were common (20 [53%] of 38 patients in part 1 and 22 [63%] of 35 in part 2); most (18 [47%] in part 1 and 19 [54%] in part 2) were grade 1 or 2 and resulted in two treatment discontinuations in part 1 and no discontinuations in part 2. The most common grade 3 or 4 events were thrombocytopenia (13 [34%] of 38 patients in part 1 and 12 [34%] of 35 in part 2) and anaemia (6 [16%] in part 1 and 5 [14%] in part 2). There were 12 treatment-related serious adverse events and no treatment-related deaths. In part 2, 21 (60·0%; 95% CI 42·1-76·1) of 35 patients achieved an overall response.

INTERPRETATION

At the identified recommended phase 2 dose, GSK2857916 was well tolerated and had good clinical activity in heavily pretreated patients, thereby indicating that this might be a promising candidate for the treatment of relapsed or refractory multiple myeloma.

FUNDING

GlaxoSmithKline.

Clinical impact of serum soluble SLAMF7 in multiple myeloma

The signaling lymphocytic activation molecule family (SLAMF7; also known as CS1 or CD319) is highly expressed on plasma cells from multiple myeloma (MM) as well as natural killer (NK) cells and is a well-known therapeutic target of elotuzumab. The objective of this study was to evaluate the clinical significance of serum soluble SLAMF7 (sSLAMF7) levels in patients with MM (n=103) and furthermore the impact of sSLMF7 on the antitumor activity of anti-SLAMF7 antibody. Thirty-one percent of MM patients, but not patients with monoclonal gammopathy of undetermined significance and healthy controls, had detectable levels of serum sSLAMF7, which were significantly increased in advanced MM patients. Further, MM in sSLAMF7-postive patients exhibited aggressive clinical characteristics with shorter progression-free survival times in comparison with sSLAMF7-negative patients. In responders to MM therapy, the levels of sSLAMF7 were undetectable or decreased compared with those before treatment. In addition, the anti-SLAMF7 antibody-mediated antibody-dependent cellular cytotoxicity of NK cells against MM cell lines was inhibited by recombinant SLAMF7 protein. Thus, our findings suggest that high concentrations of sSLAMF7, which could transiently suppress the therapeutic effects of elotuzumab, may be a useful indicator of disease progression in MM patients.

APRIL signaling via TACI mediates immunosuppression by T regulatory cells in multiple myeloma: therapeutic implications

We here investigate how APRIL impacts immune regulatory T cells and directly contributes to the immunosuppressive multiple myeloma (MM) bone marrow (BM) microenvironment. First, APRIL receptor TACI expression is significantly higher in regulatory T cells (Tregs) than conventional T cells (Tcons) from the same patient, confirmed by upregulated Treg markers, i.e., Foxp3, CTLA-4. APRIL significantly stimulates proliferation and survival of Tregs, whereas neutralizing anti-APRIL monoclonal antibodies (mAbs) inhibit theses effects. Besides TACI-dependent induction of cell cycle progression and anti-apoptosis genes, APRIL specifically augments Foxp3, IL-10, TGFβ1, and PD-L1 in Tregs to further enhance Treg-inhibited Tcon proliferation. APRIL further increases MM cell-driven Treg (iTreg) via TACI-dependent proliferation associated with upregulated IL-10, TGFβ1, and CD15s in iTreg, which further inhibits Tcons. Osteoclasts producing APRIL and PD-L1 significantly block Tcon expansion by iTreg generation, which is overcome by combined treatment with anti-APRIL and -PD1/PD-L1 mAbs. Finally, APRIL increases IL-10-producing B regulatory cells (Bregs) via TACI on BM Bregs of MM patients. Taken together, these results define novel APRIL actions via TACI on Tregs and Bregs to promote MM cell survival, providing the rationale for targeting APRIL/TACI system to alleviate the immunosuppressive BM milieu and improve patient outcome in MM.

Targeting B Cell Maturation Antigen (BCMA) in Multiple Myeloma: Potential Uses of BCMA-Based Immunotherapy

The approval of the first two monoclonal antibodies targeting CD38 (daratumumab) and SLAMF7 (elotuzumab) in late 2015 for treating relapsed and refractory multiple myeloma (RRMM) was a critical advance for immunotherapies for multiple myeloma (MM). Importantly, the outcome of patients continues to improve with the incorporation of this new class of agents with current MM therapies. However, both antigens are also expressed on other normal tissues including hematopoietic lineages and immune effector cells, which may limit their long-term clinical use. B cell maturation antigen (BCMA), a transmembrane glycoprotein in the tumor necrosis factor receptor superfamily 17 (TNFRSF17), is expressed at significantly higher levels in all patient MM cells but not on other normal tissues except normal plasma cells. Importantly, it is an antigen targeted by chimeric antigen receptor (CAR) T-cells, which have already shown significant clinical activities in patients with RRMM who have undergone at least three prior treatments, including a proteasome inhibitor and an immunomodulatory agent. Moreover, the first anti-BCMA antibody–drug conjugate also has achieved significant clinical responses in patients who failed at least three prior lines of therapy, including an anti-CD38 antibody, a proteasome inhibitor, and an immunomodulatory agent. Both BCMA targeting immunotherapies were granted breakthrough status for patients with RRMM by FDA in Nov 2017. Other promising BCMA-based immunotherapeutic macromolecules including bispecific T-cell engagers, bispecific molecules, bispecific or trispecific antibodies, as well as improved forms of next generation CAR T cells, also demonstrate high anti-MM activity in preclinical and even early clinical studies. Here, we focus on the biology of this promising MM target antigen and then highlight preclinical and clinical data of current BCMA-targeted immunotherapies with various mechanisms of action. These crucial studies will enhance selective anti-MM response, transform the treatment paradigm, and extend disease-free survival in MM.

Osteoclast Immunosuppressive Effects in Multiple Myeloma: Role of Programmed Cell Death Ligand 1

Immunomodulatory drugs and monoclonal antibody-based immunotherapies have significantly improved the prognosis of the patients with multiple myeloma (MM) in the recent years. These new classes of reagents target malignant plasma cells (PCs) and further modulate the immune microenvironment, which prolongs anti-MM responses and may prevent tumor occurrence. Since MM remains an incurable cancer for most patients, there continues to be a need to identify new tumor target molecules and investigate alternative cellular approaches using gene therapeutic strategies and novel treatment mechanisms. Osteoclasts (OCs), as critical multi-nucleated large cells responsible for bone destruction in >80% MM patients, have become an attractive cellular target for the development of novel MM immunotherapies. In MM, OCs are induced and activated by malignant PCs in a reciprocal manner, leading to osteolytic bone disease commonly associated with this malignancy. Significantly, bidirectional interactions between OCs and MM cells create a positive feedback loop to promote MM cell progression, increase angiogenesis, and inhibit immune surveillance via both cell-cell contact and abnormal production of multiple cytokines/chemokines. Most recently, hyper-activated OCs have been associated with activation of programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway, which impairs T cell proliferation and cytotoxicity against MM cells. Importantly, therapeutic anti-CD38 monoclonal antibodies and checkpoint inhibitors can alleviate OC-induced immune suppression. Furthermore, a proliferation-inducing ligand, abundantly secreted by OCs and OC precursors, significantly upregulates PD-L1 expression on MM cells, in addition to directly promoting MM cell proliferation and survival. Coupled with increased PD-L1 expression in other immune-suppressive cells, i.e., myeloid-derived suppressor cells and tumor-associated macrophages, these results strongly suggest that OCs contribute to the immunosuppressive MM BM microenvironment. Based on these findings and ongoing osteoimmunology studies, therapeutic interventions targeting OC number and function are under development to diminish both MM bone disease and related immune suppression. In this review, we discuss the classical and novel roles of OCs in the patho-immunology of MM. We also describe novel therapeutic strategies simultaneously targeting OCs and MM interactions, including PD-1/PD-L1 axis, to overcome the immune-suppressive microenvironment and improve patient outcome.

Chimeric antigen receptor-modified T cells: CD19 and the road beyond

The ability to harness a patient's immune system to target malignant cells is now transforming the treatment of many cancers, including hematologic malignancies. The adoptive transfer of T cells selected for tumor reactivity or engineered with natural or synthetic receptors has emerged as an effective modality, even for patients with tumors that are refractory to conventional therapies. The most notable example of adoptive cell therapy is with T cells engineered to express synthetic chimeric antigen receptors (CARs) that reprogram their specificity to target CD19. CAR T cells have shown remarkable antitumor activity in patients with refractory B-cell malignancies. Ongoing research is focused on understanding the mechanisms of incomplete tumor elimination, reducing toxicities, preventing antigen escape, and identifying suitable targets and strategies based on established and emerging principles of synthetic biology for extending this approach to other hematologic malignancies. This review will discuss the current status, challenges, and potential future applications of CAR T-cell therapy in hematologic malignancies.

The role of the BAFF/APRIL system in the T cell-independent specific response to blood stage Plasmodium falciparum hemozoin

BACKGROUND

The B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are tumor necrosis factor family members that regulate B cell maturation, proliferation, survival and function. We have previously shown that blood-stage Plasmodium falciparum hemozoin (HZ) can act as a T-independent antigen (TI Ag) that induces the production of specific IgG to soluble crude P. falciparum Ag through the BAFF pathway. However, we have not yet clarified whether HZ need APRIL signaling in the TI response. Here, we aimed to clarify whether both BAFF and APRIL signaling pathways play roles in HZ induction of specific antibody production without T-cell help.

METHODS

Normal monocytes alone or co-cultured with naïve B cells were stimulated by HZ (10 µM) in vitro. Naïve B cell cultures, with HZ alone or with exogenous recombinant BAFF (rBAFF) and recombinant APRIL (rAPRIL) plus recombinant IL-4 (rIL-4) for 6 and 10 days were used as controls to investigate activation of B cells. At various times, the levels of sBAFF, sAPRIL, and HZ-specific IgG in the culture supernatants were assessed by enzyme-linked immunosorbent assay. The BAFF and APRIL expression levels on the HZ-stimulated monocytes and their specific receptors on activated B cells, including the BAFF receptor (BAFF-R), the transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) and the B cell maturation antigen (BCMA), were determined by flow cytometry. mRNA expression levels for the receptors were validated using Real-Time quantitative PCR.

RESULTS

HZ-activated monocytes released sBAFF and sAPRIL during the 72 h stimulation period. Increased mRNA encoding of their cognate receptors, BAFF-R, TACI, and BCMA, and increased HZ-specific IgG levels were also observed in HZ induction within the monocyte and B cell co-culture. The experiments under control conditions revealed that HZ alone could induce B cell culture to produce a small amount of the specific IgG compared with those in medium alone or rBAFF + rAPRIL + rIL-4.

CONCLUSION

Taken together, we suggest that in the TI response HZ stimulates monocyte and B cell co-culture to produce specific IgG through BAFF, APRIL and other independent complimentary signaling pathways.

Pre-clinical validation of B cell maturation antigen (BCMA) as a target for T cell immunotherapy of multiple myeloma

Multiple myeloma has a continued need for more effective and durable therapies. B cell maturation antigen (BCMA), a plasma cell surface antigen and member of the tumor necrosis factor (TNF) receptor superfamily, is an attractive target for immunotherapy of multiple myeloma due to its high prevalence on malignant plasma cells. The current work details the pre-clinical evaluation of BCMA expression and development of a chimeric antigen receptor (CAR) targeting this antigen using a fully human single chain variable fragment (scFv). We demonstrate that BCMA is prevalently, but variably expressed by all MM with expression on 25–100% of malignant plasma cells. Extensive Immunohistochemical analysis of normal tissue expression using commercially available polyclonal antibodies demonstrated expression within B-lineage cells across a number of tissues as expected. Based upon the highly restricted expression of BCMA within normal tissues, we generated a set of novel, fully human scFv binding domains to BCMA by screening a naïve B-cell derived phage display library. Using a series of in vitro and pre-clinical in vivo studies, we identified a scFv with high specificity for BCMA and robust anti-myeloma activity when used as the binding domain of a second-generation CAR bearing a CD137 costimulatory domain. This BCMA-specific CAR is currently being evaluated in a Phase 1b clinical study in relapsed and refractory MM patients (NCT02546167).

CAR T Cells and Other Cellular Therapies for Multiple Myeloma: 2018 Update

Cellular therapies are a rapidly evolving approach to myeloma treatment, which bring a unique mechanism of action with the potential to overcome drug resistance and induce long-term remissions. Two primary approaches are being studied: non-gene-modified strategies, which rely on the endogenous anti-myeloma T-cell repertoire, and gene-modified strategies, which introduce a new T-cell receptor (TCR) or a chimeric antigen receptor (CAR) to confer novel antigen specificity. CAR T cells show the greatest activity to date. Multiple antigen targets, including B-cell maturation antigen (BCMA), CD19, CD38, CD138, and SLAMF7, are being explored for myeloma, and BCMA has emerged as the most promising. Preliminary data from four phase I studies of BCMA CAR T cells, each using a different CAR construct, that involved 90 evaluable patients with relapsed/refractory disease have been reported. These data show response rates of 60% to 100%, including minimal residual disease (MRD)-negative complete remissions, at effective doses (> 10⁸ CAR-positive cells) after lymphodepleting conditioning. Response durability has been more variable, likely related to differences in CAR T-cell products, lymphodepleting regimens, patient selection criteria, and/or underlying biology/prognostic factors. In the two most recent studies, however, most patients remained progression free with median follow-up time of 6 to 10 months; some ongoing remissions lasted more than 1 year. Toxicities are similar to those from CD19 CAR T cells and include cytokine release syndrome and neurotoxicity that is reversible but can be severe. Multiple BCMA CAR T-cell studies are ongoing. Future directions include combinations with immunomodulatory drugs, checkpoint inhibitors, or other CAR T cells, as well as use of gene-edited cellular products to enhance the safety and efficacy of this approach.

Investigational agents in immunotherapy: a new horizon for the treatment of multiple myeloma

The treatment of multiple myeloma (MM) has gone through several major advances over the last 5 years with the introduction of next generation proteasome inhibitors (PI; carfilzomib, ixazomib) and immunomodulatory derivatives (IMiD; pomalidomide), with these new agents having a substantial impact on patient outcome. However, despite these advances, MM remains a highly resistant disease given its propensity for clonal heterogeneity and its complex interaction with the surrounding bone marrow microenvironment. Almost all patients eventually relapse despite therapeutic responses to a PI, IMiD or both. With the regulatory approval of the monoclonal antibodies Daratumumab and Elotuzumab in 2015, impressive and durable responses are being observed, even in heavily pre-treated patients who have exhausted other therapeutic options, suggesting immunological approaches in this setting have real merit. This review will focus on newer monoclonal antibodies and chimeric-antigen receptor (CAR) T cell strategies currently under investigation and in various stages of clinical development.

Lenalidomide regulates osteocytes fate and related osteoclastogenesis via IL-1β/NF-κB/RANKL signaling

Osteolytic diseases are closely associated with osteocyte fate, indicating a more efficient and crucial role of osteocyte-targeting strategy in inhibiting osteoclastogenesis. Here, we investigated the effects of lenalidomide (Lena) on osteocyte fate in order to regulate osteoclastogenesis via effective cascade-controlling response. Our data revealed that lenalidomide treatment notably rescued IL-1β induced loss of osteocyte viability by inhibiting osteocyte apoptosis with decreased osteoclast-related factors, RANKL and Sclerostin, as demonstrated by the restricted osteoclast formation and reduced bone resorption. Additionally, iTRAQ assay revealed that IL-1β induced activation of NF-κB inhibitor α/β were remarkably downregulated by lenalidomide, showing that lenalidomide impaired NF-κB signaling in osteocytes for inhibiting the expression of osteoclast specific genes in osteoclasts, which was further confirmed by KEGG pathway analysis and Western blot. More interestingly, the in vivo analysis of osteocyte apoptosis and osteoclastogenesis in osteoarthritis mice model indicated a role of lenalidomide in the regulation of osteocyte fate and the consequent inhibition of RANKL-induced osteoclastogenesis. Together, these results suggest that lenalidomide regulates osteocyte fate by attenuating IL-1β/NF-κB signaling, thereby inhibiting RANKL expression for the attenuated osteoclastogenesis both in vitro and vivo, indicating a more efficient remedy among future anti-osteoclastogenesis approaches.

The link between bone microenvironment and immune cells in multiple myeloma: Emerging role of CD38

The relationship between bone and immune cells is well established both in physiological and pathological conditions. Multiple myeloma (MM) is a plasma cell malignancy characterized by an increase of number and activity of osteoclasts (OCLs) and a decrease of osteoblasts (OBs). These events are responsible for bone lesions of MM patients. OCLs support MM cells survival in vitro and in vivo. Recently, the possible role of OCLs as immunosuppressive cells in the MM BM microenvironment has been underlined. OCLs protect MM cells against T cell-mediated cytotoxicity through the expression of several molecules including programmed death-ligand (PD-L) 1, galectin (Gal) 9, CD200, and indoleamine-2,3-dioxygenase (IDO). Among the molecules that could be involved in the link between immune-microenvironment and osteoclastogenesis the role of CD38 has been hypothesized. CD38 is a well-known adhesion molecule and an ectoenzyme highly expressed by MM cells. Moreover, CD38 is expressed by OCLs and at the surface level on OCL precursors. Targeting CD38 with monoclonal antibodies showed inhibition of both osteoclastogenesis and OCL-mediated suppression of T cell function. This review elucidates this evidence indicating that osteoclastogenesis affect MM immune-microenvironment being a potential target to improve anti-MM immunity and to ameliorate bone disease.

Development and Evaluation of an Optimal Human Single-Chain Variable Fragment-Derived BCMA-Targeted CAR T Cell Vector

B cell maturation antigen (BCMA) has recently been identified as an important multiple myeloma (MM)-specific target for chimeric antigen receptor (CAR) T cell therapy. In CAR T cell therapy targeting CD19 for lymphoma, host immune anti-murine CAR responses limited the efficacy of repeat dosing and possibly long-term persistence. This clinically relevant concern can be addressed by generating a CAR incorporating a human single-chain variable fragment (scFv). We screened a human B cell-derived scFv phage display library and identified a panel of BCMA-specific clones from which human CARs were engineered. Despite a narrow range of affinity for BCMA, dramatic differences in CAR T cell expansion were observed between unique scFvs in a repeat antigen stimulation assay. These results were confirmed by screening in a MM xenograft model, where only the top preforming CARs from the repeat antigen stimulation assay eradicated disease and prolonged survival. The results of this screening identified a highly effective CAR T cell therapy with properties, including rapid in vivo expansion (>10,000-fold, day 6), eradication of large tumor burden, and durable protection to tumor re-challenge. We generated a bicistronic construct including a second-generation CAR and a truncated-epithelial growth factor receptor marker. CAR T cell vectors stemming from this work are under clinical investigation.

Modulating PD-L1 expression in multiple myeloma: an alternative strategy to target the PD-1/PD-L1 pathway

Even with recent advances in therapy regimen, multiple myeloma patients commonly develop drug resistance and relapse. The relevance of targeting the PD-1/PD-L1 axis has been demonstrated in pre-clinical models. Monotherapy with PD-1 inhibitors produced disappointing results, but combinations with other drugs used in the treatment of multiple myeloma seemed promising, and clinical trials are ongoing. However, there have recently been concerns about the safety of PD-1 and PD-L1 inhibitors combined with immunomodulators in the treatment of multiple myeloma, and several trials have been suspended. There is therefore a need for alternative combinations of drugs or different approaches to target this pathway. Protein expression of PD-L1 on cancer cells, including in multiple myeloma, has been associated with intrinsic aggressive features independent of immune evasion mechanisms, thereby providing a rationale for the adoption of new strategies directly targeting PD-L1 protein expression. Drugs modulating the transcriptional and post-transcriptional regulation of PD-L1 could represent new therapeutic strategies for the treatment of multiple myeloma, help potentiate the action of other drugs or be combined to PD-1/PD-L1 inhibitors in order to avoid the potentially problematic combination with immunomodulators. This review will focus on the pathophysiology of PD-L1 expression in multiple myeloma and drugs that have been shown to modulate this expression.

CD38-targeting antibodies in multiple myeloma: mechanisms of action and clinical experience

INTRODUCTION

Multiple myeloma (MM) is generally an incurable hematological malignancy with heterogeneous overall survival rates ranging from a few months to more than 10 years. Survival is especially poor for patients who developed disease that is refractory to immunomodulatory drugs and proteasome inhibitors. Areas covered: This review will discuss the importance of CD38-targeting antibodies for the treatment of MM patients to improve their outcome. Expert commentary: Intense immuno-oncological laboratory research has resulted in the development of functionally active monoclonal antibodies against cell surface markers present on MM cells. In this respect, CD38-targeting antibodies such as daratumumab, MOR202, and isatuximab, have high single agent activity in heavily pretreated MM patients by virtue of their pleiotropic mechanisms of action including Fc-dependent effector mechanisms and immunomodulatory activities. Importantly, CD38-targeting antibodies are well tolerated, with infusion reactions as most frequent adverse event. Altogether, this makes them attractive combination partners with other anti-MM agents. Daratumumab is already approved as monotherapy and in combination with lenalidomide-dexamethasone as well as bortezomib-dexamethasone in pretreated MM patients. Furthermore, results from studies evaluating CD38-targeting antibodies in newly diagnosed MM patients are also promising, indicating that CD38-targeting antibodies will be broadly used in MM, resulting in further improvements in survival.

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.

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.

Neutral tumor evolution in myeloma is associated with poor prognosis

Recent studies suggest that the evolutionary history of a cancer is important in forecasting clinical outlook. To gain insight into the clonal dynamics of multiple myeloma (MM) and its possible influence on patient outcomes, we analyzed whole exome sequencing tumor data for 333 patients from Myeloma XI, a UK phase 3 trial and 434 patients from the CoMMpass study, all of which had received immunomodulatory drug (IMiD) therapy. By analyzing mutant allele frequency distributions in tumors, we found that 17% to 20% of MM is under neutral evolutionary dynamics. These tumors are associated with poorer patient survival in nonintensively treated patients, which is consistent with the reduced therapeutic efficacy of microenvironment-modulating IMiDs. Our findings provide evidence that knowledge of the evolutionary history of MM has relevance for predicting patient outcomes and personalizing therapy.

Downregulation of LRIG2 expression inhibits angiogenesis of glioma via EGFR/VEGF-A pathway

Active angiogenesis is the basic pathological feature of glioma. Tumor angiogenesis is involved in vascular endothelial cell migration to the tumor tissue and in the formation of tube-like structures. The present study aimed to investigate the role of leucine-rich repeats and immunoglobulin-like domains 2 (LRIG2) in glioma angiogenesis. Glioma (n=50) and normal brain (n=20) tissue samples were collected from patients to detect the expression of LRIG2, epidermal growth factor receptor (EGFR), vascular endothelial growth factor A (VEGF-A), and cluster of differentiation 31 (CD31) using immunohistochemistry. In addition, the association between the expression of LRIG2 in glioma tissue and the microvessel density (MVD) was analyzed. In vitro, the expression of LRIG2 in human glioma U87 and U251 cell lines was knocked down. Subsequently, cell migration and tube formation assays of human umbilical vein endothelial cells (HUVECs) were performed using a coculture system. The protein expression levels of LRIG2, EGFR, phosphorylated-EGFR and VEGF-A were determined using western blotting. The results demonstrated that the expression levels of LRIG2, EGFR, VEGF-A and CD31 were highly upregulated in glioma tissue samples. Furthermore, LRIG2 expression in glioma tissue samples was significantly correlated with the MVD. In vitro, the downregulation of LRIG2 inhibited HUVEC migration and tube formation induced by coculture with glioma cells. The downregulation of LRIG2 resulted in decreased expression of EGFR and VEGF-A. The effects of the LRIG2 knockdown were reversed following EGF treatment. These findings suggest that LRIG2 is a potential target for the inhibition of glioma angiogenesis, which is possibly mediated via the EGFR/VEGF-A signaling pathway.

Interferon-alpha-based immunotherapies in the treatment of B cell-derived hematologic neoplasms in today's treat-to-target era

B cell lymphoma and multiple myeloma (MM) are the most common hematological malignancies which benefit from therapeutic monoclonal antibodies (mAbs)-based immunotherapies. Despite significant improvement on patient outcome following the use of novel therapies for the past decades, curative treatment is unavailable for the majority of patients. For example, the 5-year survival of MM is currently less than 50%. In the 1980s, interferon-α was used as monotherapy in newly diagnosed or previously treated MM with an overall response rate of 15-20%. Noticeably, a small subset of patients who responded to long-term interferon-α further achieved sustained complete remission. Since 1990, interferon-α-containing regimens have been used as a central maintenance strategy for patients with MM. However, the systemic administration of interferon-α was ultimately limited by its pronounced toxicity. To address this, the selective mAb-mediated delivery of interferon-α has been developed to enhance specific killing of MM and B-cell malignant cells. As such, targeted interferon-α therapy may improve therapeutic window and sustain responses, while further overcoming suppressive microenvironment. This review aims to reinforce the role of interferon-α by consolidating our current understanding of targeting interferon-α with tumor-specific mAbs for B cell lymphoma and myeloma.

Changes in uninvolved immunoglobulins during induction therapy for newly diagnosed multiple myeloma

Little is known about the impact of multiple myeloma (MM) treatment on uninvolved immunoglobulins (Ig). We identified 448 patients who received high-dose dexamethasone (HD-DEX), lenalidomide and dexamethasone (RD), bortezomib and dexamethasone (VD), bortezomib, cyclophosphamide and dexamethasone (VCD) or bortezomib, lenalidomide and dexamethasone (VRD) for newly diagnosed MM at our institution between 2000 and 2013, and who had available data on absolute lymphocyte count (ALC) and quantitative uninvolved Ig at baseline and at the end of four cycles of therapy. Changes in ALC and uninvolved Ig were significantly different across treatments, with VCD and HD-DEX producing reductions in uninvolved Ig, and RD, VD and VRD leading to increases in uninvolved Ig. In addition, treatment with RD, VD and VRD was independently associated with higher odds of achieving a ⩾25% increase in or normalization of the primary uninvolved Ig on multivariate analysis. Although achievement of a humoral response in the primary uninvolved Ig was associated with a higher odds of achieving VGPR or better after four cycles of therapy, it was not associated with improved overall survival. These data highlight the different mechanisms of action of MM drugs and point toward a possible role for the use of VCD in treating antibody-mediated autoimmune disease.

NF-κB in Hematological Malignancies

NF-κB (Nuclear Factor Κ-light-chain-enhancer of activated B cells) transcription factors are critical regulators of immunity, stress response, apoptosis, and differentiation. Molecular defects promoting the constitutive activation of canonical and non-canonical NF-κB signaling pathways contribute to many diseases, including cancer, diabetes, chronic inflammation, and autoimmunity. In the present review, we focus our attention on the mechanisms of NF-κB deregulation in hematological malignancies. Key positive regulators of NF-κB signaling can act as oncogenes that are often prone to chromosomal translocation, amplifications, or activating mutations. Negative regulators of NF-κB have tumor suppressor functions, and are frequently inactivated either by genomic deletions or point mutations. NF-κB activation in tumoral cells is also driven by the microenvironment or chronic signaling that does not rely on genetic alterations.

A novel agent SL-401 induces anti-myeloma activity by targeting plasmacytoid dendritic cells, osteoclastogenesis and cancer stem-like cells

Novel therapies for multiple myeloma (MM) can target mechanism(s) in the host-MM bone marrow (BM) microenvironment mediating MM progression and chemoresistance. Our studies showed increased numbers of tumor-promoting, immunosuppressive and drug-resistant plasmacytoid dendritic cells (pDCs) in the MM BM microenvironment. pDC-MM cell interactions upregulate interleukin-3 (IL-3), which stimulates both pDC survival and MM cell growth. Since IL-3 R is highly expressed on pDCs in the MM BM milieu, we here targeted pDCs using a novel IL-3 R-targeted therapeutic SL-401. In both in vitro and in vivo models of MM in its BM milieu, SL-401 decreases viability of pDCs, blocks pDC-induced MM cell growth, and synergistically enhances anti-MM activity of bortezomib and pomalidomide. Besides promoting pDC survival and MM cell growth, IL-3 also mediates progression of osteolytic bone disease in MM. Osteoclast (OCL) progenitor cells express IL-3 R, and we show that SL-401 abrogates monocyte-derived OCL formation and bone resorption. Finally, we show that SL-401 also decreases the viability of IL-3 R-expressing cancer stem-like cells in MM. Overall, our study provides the preclinical basis for clinical trials of SL-401 to block pDC-induced MM cell growth, inhibit osteoclastogenesis and target MM stem-like cell subpopulations to improve patient outcome in MM.

Monoclonal antibody therapy in multiple myeloma

The therapeutic landscape of multiple myeloma (MM) has evolved spectacularly over the past decade with the discovery and validation of proteasome inhibitors and immunomodulatory agents as highly active agents, both in front-line therapy as well as in the relapse and maintenance settings. Although previous attempts to apply available monoclonal antibodies (Mabs) to the treatment of patients with MM has until recently been disappointing, novel targets specifically explored in the context of MM have recently lead to the first approvals of Mabs for the treatment of patients with MM. We have performed a literature search to identify preclinical targeting of MM, including in vitro and in vivo models using monoclonal antibodies, as well as clinical trials of monoclonal antibodies in patients with MM. Sources used were peer-reviewed publications, congress abstracts and on-line clinical trials data (such as clinicaltrials.gov). Several targets have been evaluated in preclinical models and a growing number of agents are being evaluated in clinical trials, as single agents or in combination and under various antibody formats. Two agents, targeting for the first time CD38 and SLAMF7, respectively, have recently been approved for the treatment of patients with MM. The recent approval of these two antibodies is expected to have a strong impact on treatment modalities and outcome in patients with MM, including both transplant eligible and elderly patients.

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

B-cell maturation antigen (BCMA) is a highly plasma cell-selective protein that is expressed on malignant plasma cells of multiple myeloma (MM) patients and therefore is an ideal target for T-cell redirecting therapies. We developed a bispecific T-cell engager (BiTE) targeting BCMA and CD3ɛ (BI 836909) and studied its therapeutic impacts on MM. BI 836909 induced selective lysis of BCMA-positive MM cells, activation of T cells, release of cytokines and T-cell proliferation; whereas BCMA-negative cells were not affected. Activity of BI 836909 was not influenced by the presence of bone marrow stromal cells, soluble BCMA or a proliferation-inducing ligand (APRIL). In ex vivo assays, BI 836909 induced potent autologous MM cell lysis in both, newly diagnosed and relapsed/refractory patient samples. In mouse xenograft studies, BI 836909 induced tumor cell depletion in a subcutaneous NCI-H929 xenograft model and prolonged survival in an orthotopic L-363 xenograft model. In a cynomolgus monkey study, administration of BI 836909 led to depletion of BCMA-positive plasma cells in the bone marrow. Taken together, these results show that BI 836909 is a highly potent and efficacious approach to selectively deplete BCMA-positive MM cells and represents a novel immunotherapeutic for the treatment of MM.

A look backward and forward in the regulatory and treatment history of multiple myeloma: Approval of novel-novel agents, new drug development, and longer patient survival

The past decade has seen significant advances in our understanding and treatment of multiple myeloma (MM) and its precursor diseases. These advances include gains in knowledge of the underlying pathobiology including molecular and cellular prognostic factors for disease progression. In parallel we have witnessed the availability of novel therapeutics. Together these advances have translated into improvements in long-term clinical benefit and survival in MM. Indeed, it has been shown that patients diagnosed in the last decade have experienced almost doubling of median survival time. We aim to review and give further insight into drug development and novel drug approvals that have revolutionized the treatment of MM.

Progress and Paradigms in Multiple Myeloma

Remarkable progress has been achieved in multiple myeloma, and patient median survival has been extended 3- to 4-fold. Specifically, there have been 18 newly approved treatments for multiple myeloma in the past 12 years, including seven in 2015, and the treatment paradigm and patient outcome have been transformed. The definition of patients benefitting from these therapies has been broadened. Response criteria now include minimal residual disease (MRD), assessed in bone marrow by multicolor flow cytometry or sequencing, and by imaging for extramedullary disease. Initial therapy for transplant candidates is a triplet incorporating novel therapies-that is, lenalidomide, bortezomib, and dexamethasone or cyclophosphamide, bortezomib, and dexamethasone. Lenalidomide maintenance until progression can prolong progression-free and overall survival in standard-risk multiple myeloma, with incorporation of proteasome inhibitor for high-risk disease. Studies are evaluating the value of early versus late transplant and MRD as a therapeutic goal to inform therapy. In nontransplant patients, triplet therapies are also preferred, with doublet therapy reserved for frail patients, and maintenance as described above. The availability of second-generation proteasome inhibitors (carfilzomib and ixazomib), immunomodulatory drugs (pomalidomide), histone deacetylase inhibitors (panobinostat), and monoclonal antibodies (elotuzumab and daratumumab) allows for effective combination therapies of relapsed disease as well. Finally, novel therapies targeting protein degradation, restoring autologous memory anti-multiple myeloma immunity, and exploiting genetic vulnerabilities show promise to improve patient outcome even further. Clin Cancer Res; 22(22); 5419-27. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "MULTIPLE MYELOMA MULTIPLYING THERAPIES".

cDNA-library testing identifies transforming genes cooperating with c-myc in mouse pre-B cells

While c-myc often contributes to the generation of B cell transformation, its transgenic overexpression alone does not lead to full transformation of B-lineage cells. Synergistically acting second genes must cooperate. Here, we constructed doxycycline-inducible cDNA-libraries from pre-B cell mRNA. These libraries were retrovirally transduced as single copies into single cells and overexpressed in fetal-liver-derived c-myc-overexpressing pre-B cell lines. We scored transformation by survival and/or expansion of differentiating B-lineage cells in vitro and in vivo. Only one double c-myc/cDNA-library-expressing cell line was found in less than 5 × 10⁶ library-transduced pre-B cells surviving and expressing a cDNA-library-derived transcript in vitro. This transcript was identified as a shortened form of the Exosc1 gene, encoding the RNA exosome complex component CSL4. Transplantations of double c-myc/Exosc1 short-form- or c-myc/Exosc1 full-length-transgenic cells into Rag1^-/- mice resulted in survival, differentiation to CD19⁺ CD93^- sIgM⁺ CD5^low/- CD11b⁺ mature B1 cells and, surprisingly, also vigorous expansion in vivo. Strikingly, after transplantations of c-myc/cDNA-library pre-BI cells the frequencies of double-transgenic pre-B cells and their differentiated progeny, expanding in vivo to heterogeneous phenotypes, was at least tenfold higher than in vitro. In a first analysis Ptprcap, Cacybp, Ndufs7, Rpl18a, and Rpl35a were identified. This suggests a strong influence of the host on B-cell transformation.

Osteoclasts promote immune suppressive microenvironment in multiple myeloma: therapeutic implication

OCs play a crucial role in myeloma-induced immunosuppressive microenvironment. Therapeutic anti-CD38 mAb partially overcomes the immunosuppressive effect of OCs.

NF-κB dysregulation in multiple myeloma

The nuclear factor-κB (NF-κB) transcription factor family plays critical roles in the pathophysiology of hematologic neoplasias, including multiple myeloma. The current review examines the roles that this transcription factor system plays in multiple myeloma cells and the nonmalignant accessory cells of the local microenvironment; as well as the evidence indicating that a large proportion of myeloma patients harbor genomic lesions which perturb diverse genes regulating the activity of NF-κB. This article also discusses the therapeutic targeting of the NF-κB pathway using proteasome inhibitors, a pharmacological class that has become a cornerstone in the therapeutic management of myeloma; and reviews some of the future challenges and opportunities for NF-κB-related research in myeloma.