Targeting the PD-1/PD-L1 axis in multiple myeloma: a dream or a reality?

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.

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

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

Status of programmed death-ligand 1 expression in sarcomas

Background

Sarcomas are challenging to study because of their rarity and histomorphological complexity. PD1 and PD-L1 inhibitors showed a promising anti-tumor effect in solid tumors, where a relationship between PD-L1 expression and the objective response has been evidenced.

Methods

In this study, we examined PD-L1 expression in 16 bone and soft tissue sarcoma cell lines of 11 different subtypes by means of western blot, flow cytometry and immunocytochemistry, and in 230 FFPE patient-derived tumor tissues by means of immunohistochemistry using three different antibody clones. The association between PD-L1 expression and clinicopathological features was evaluated.

Results

We demonstrated that PD-L1 protein is highly expressed in pleomorphic rhabdomyosarcoma, fibrosarcoma, and dedifferentiated liposarcoma (DDLPS) cell lines. From the tissue microarray, undifferentiated pleomorphic sarcoma showed ≥ 1% immunoreactivity in 20%, 17.6%, and 16.3% of the cases with PD-L1 22C3, SP263, and SP142 antibodies, respectively. In whole sections stained with a PD-L1 22C3 antibody, DDLPS showed ≥ 1% immunoreactivity in 21.9% of the cases. In DDLPS group, cases with ≥ 1% PD-L1 expression showed statistically significantly worse recurrence-free survival (P = 0.027) and overall survival (P = 0.017) rates. Upon interferon–gamma treatment, the mRNA expression levels of PD-L1 were elevated in the HS-RMS-1, LIPO-224B, MLS1765, RH30, and RH41 cell lines.

Conclusions

We found that the expression of PD-L1 in sarcoma differs depending on the histologic subtype and the PD-L1 antibody clones. These results may serve as primary data for the selection of appropriate patients when applying PD1/PD-L1 inhibitor therapy in sarcoma.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1658-5) contains supplementary material, which is available to authorized users.

Vγ9Vδ2 T Cells as Strategic Weapons to Improve the Potency of Immune Checkpoint Blockade and Immune Interventions in Human Myeloma

The advent of immune checkpoint (ICP) blockade has introduced an unprecedented paradigm shift in the treatment of cancer. Though very promising, there is still a substantial proportion of patients who do not respond or develop resistance to ICP blockade. In vitro and in vivo models are eagerly needed to identify mechanisms to maximize the immune potency of ICP blockade and overcome primary and acquired resistance to ICP blockade. Vγ9Vδ2 T cells isolated from the bone marrow (BM) from multiple myeloma (MM) are excellent tools to investigate the mechanisms of resistance to PD-1 blockade and to decipher the network of mutual interactions between PD-1 and the immune suppressive tumor microenvironment (TME). Vγ9Vδ2 T cells can easily be interrogated to dissect the progressive immune competence impairment generated in the TME by the long-lasting exposure to myeloma cellss. BM MM Vγ9Vδ2 T cells are PD-1⁺ and anergic to phosphoantigen (pAg) stimulation; notably, single agent PD-1 blockade is insufficient to fully recover their anti-tumor activity in vitro indicating that additional players are involved in the anergy of Vγ9Vδ2 T cells. In this mini-review we will discuss the value of Vγ9Vδ2 T cells as investigational tools to improve the potency of ICP blockade and immune interventions in MM.

The challenges of checkpoint inhibition in the treatment of multiple myeloma

Despite significant improvements in the overall survival of patients with multiple myeloma (MM) over the past 15 years, the disease remains incurable. Treatment options are limited for patients who have relapsed or are refractory to immunomodulatory drugs (IMiDs), proteasome inhibitors, and monoclonal antibodies. In these patients, immunotherapies such as checkpoint inhibitors, oncolytic vaccines, and chimeric antigen receptor (CAR) T cells provide a potentially effective alternative treatment. While checkpoint inhibitors are effective in prolonging overall survival in some patients with advanced solid cancers and Hodgkin lymphoma, they have not demonstrated significant activity as a single agent in MM. In fact the combination of checkpoint inhibitors with IMiDs was recently found to increase the risk of death in myeloma patients. These challenges highlight the need for a better understanding of immune dysregulation in myeloma patients, and the mechanisms of action of- and resistance to- checkpoint inhibitors. In this review, we summarize immune dysfunction in patients with MM, and review the preclinical and clinical data regarding checkpoint inhibitors in myeloma. We conclude by proposing strategies to improve the efficacy and safety of checkpoint inhibitors in this population.

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.

Role of the RANK/RANKL Pathway in Multiple Myeloma

Receptor activator of nuclear factor-kappa B (RANK) and its ligand, RANKL, are expressed in a variety of tissues throughout the body; their primary role is in the regulation of bone remodeling and development of the immune system. Consistent with these functions, evidence exists for a role of RANK/RANKL in all stages of tumorigenesis, from cell proliferation and carcinogenesis to epithelial-mesenchymal transition to neoangiogenesis and intravasation to metastasis to bone resorption and tumor growth in bone. Results from current studies also point to a role of RANK/RANKL signaling in patients with multiple myeloma, who have increased serum levels of soluble RANKL and an imbalance in RANKL and osteoprotegerin. Current therapies for patients with multiple myeloma demonstrate that RANKL may be released by tumor cells or osteoprogenitor cells. This article will review currently available evidence supporting a role for RANK/RANKL signaling in tumorigenesis, with a focus on patients with multiple myeloma.

Towards Molecular Profiling in Multiple Myeloma: A Literature Review and Early Indications of Its Efficacy for Informing Treatment Strategies

Multiple myeloma (MM), the second most common hematologic malignancy, is characterized by the clonal expansion of plasma cells. Despite dramatic improvements in patients′ survival over the past decade due to advances in therapy exploiting novel molecular targets (immunomodulatory drugs, proteasome inhibitors and monoclonal antibodies), the treatment of relapsed and refractory disease remains challenging. Recent studies confirmed complex, dynamic, and heterogeneous genomic alterations without unifying gene mutations in MM patients. In the current review, we survey recent therapeutic strategies, as well as molecular profiling data on MM, with emphasis on relapsed and refractory cases. A critical appraisal of novel findings and of their potential therapeutic implications will be discussed in detail, along with the author’s own experiences/views.

TIGIT immune checkpoint blockade restores CD8+ T-cell immunity against multiple myeloma

Immune-based therapies hold promise for the treatment of multiple myeloma (MM), but so far, immune checkpoint blockade targeting programmed cell death protein 1 has not proven effective as single agent in this disease. T-cell immunoglobulin and ITIM domains (TIGIT) is another immune checkpoint receptor known to negatively regulate T-cell functions. In this study, we investigated the therapeutic potential of TIGIT blockade to unleash immune responses against MM. We observed that, in both mice and humans, MM progression was associated with high levels of TIGIT expression on CD8⁺ T cells. TIGIT⁺ CD8⁺ T cells from MM patients exhibited a dysfunctional phenotype characterized by decreased proliferation and inability to produce cytokines in response to anti-CD3/CD28/CD2 or myeloma antigen stimulation. Moreover, when challenged with Vk*MYC mouse MM cells, TIGIT-deficient mice showed decreased serum monoclonal immunoglobulin protein levels associated with reduced tumor burden and prolonged survival, indicating that TIGIT limits antimyeloma immune responses. Importantly, blocking TIGIT using monoclonal antibodies increased the effector function of MM patient CD8⁺ T cells and suppressed MM development. Altogether our data provide evidence for an immune-inhibitory role of TIGIT in MM and support the development of TIGIT-blocking strategies for the treatment of MM patients.

Interference of Therapeutic Monoclonal Antibodies With Routine Serum Protein Electrophoresis and Immunofixation in Patients With Myeloma: Frequency and Duration of Detection of Daratumumab and Elotuzumab

OBJECTIVES

We investigated the frequency and pattern of detection of therapeutic monoclonal antibodies (t-mAbs) daratumumab and elotuzumab by routine serum protein electrophoresis (SPE) and immunofixation (IF) in treated patients with myeloma.

METHODS

Detection of t-mAb was assessed in 22 patients by retrospective review of SPE/IF ordered prior to, during, and after 26 individual courses of therapy.

RESULTS

t-mAb was distinguishable from M-protein in 16 of 26 courses, with daratumumab detected in nine of nine and elotuzumab in six of seven patients. t-mAb was detected on first follow-up SPE/IF in 12 patients, with earliest detection 7 days after therapy initiation and latest detection 70 days after therapy. t-mAb persisted throughout induction therapy in most patients, with loss of detection during maintenance daratumumab.

CONCLUSIONS

When distinguishable from M-protein, t-mAbs are detectable in 93% of treated patients as soon as 7 days after the initial dose and are consistently observed throughout induction therapy, warranting increased monitoring and careful interpretation of SPE/IF.

Vγ9Vδ2 T Cells in the Bone Marrow of Myeloma Patients: A Paradigm of Microenvironment-Induced Immune Suppression

Vγ9Vδ2 T cells are non-conventional T cells with a natural inclination to recognize and kill cancer cells. Malignant B cells, including myeloma cells, are privileged targets of Vγ9Vδ2 T cells in vitro. However, this inclination is often lost in vivo due to multiple mechanisms mediated by tumor cells and local microenvironment. Multiple myeloma (MM) is a paradigm disease in which antitumor immunity is selectively impaired at the tumor site. By interrogating the immune reactivity of bone marrow (BM) Vγ9Vδ2 T cells to phosphoantigens, we have revealed a very early and long-lasting impairment of Vγ9Vδ2 T-cell immune functions which is already detectable in monoclonal gammopathy of undetermined significance (MGUS) and not fully reverted even in clinical remission after autologous stem cell transplantation. Multiple cell subsets [MM cells, myeloid-derived suppressor cells, regulatory T cells, and BM-derived stromal cells (BMSC)] are involved in Vγ9Vδ2 T-cell inhibition via several immune suppressive mechanisms including the redundant expression of multiple immune checkpoints (ICPs). This review will address some aspects related to the dynamics of ICP expression in the BM of MM patients in relationship to the disease status (MGUS, diagnosis, remission, and relapse) and how this multifaceted ICP expression impairs Vγ9Vδ2 T-cell function. We will also provide some suggestions how to rescue Vγ9Vδ2 T cells from the immune suppression operated by ICP and to recover their antimyeloma immune effector functions at the tumor site.

Emerging small molecule approaches to enhance the antimyeloma benefit of proteasome inhibitors

Multiple myeloma (MM) is a clonal plasma cell malignancy which, despite recent treatment advances, remains incurable in the vast majority of the over 118,000 patients in the USA afflicted with this disease. Treatment of MM has dramatically improved in the past decade with the introduction of new drugs into therapeutic strategies in both the frontline and relapse settings that has led to a significant improvement in the median overall survival (OS). These drugs have been incorporated into clinical guidelines and transformed the treatment approach to MM. Numerous classes of antimyeloma agents, i.e., alkylators, steroids, proteasome inhibitors, immunomodulatory agents, deactylase inhibitors, and monoclonal antibodies, are now FDA-approved and can be combined in doublet or triplet regimens. Moreover, many patients do not respond to therapy and those that do eventually relapse. Emerging therapies that may overcome drug resistance and improve MM treatment include that inhibit regulatory and Ub-processing components of the proteasome, a specialized variant of the proteasome known as the immunoproteasome, proteolysis-targeting chimeric molecules (PROTACS and Degronomids). Emerging strategies also include accessory plasmacytoid dendritic cells (pDCs), vaccines, checkpoint inhibitors, and chimeric antigen receptor-engineered T (CAR-T) cells. Advances in understanding proteasome and plasma cell biology may allow for earlier treatment of MM patients using rationally informed combination therapies with curative potential.

Interferon-gamma in mobilized stem cells: A possible prognostic marker in early post-transplant management in multiple myeloma

INTRODUCTION

A complex network of cytokines in the bone marrow microenvironment has been implicated as an important factor in the pathogenesis of multiple myeloma (MM). Different cytokines have been studied in MM, both in peripheral blood and/or bone marrow, but there are few data correlating cytokines in leukapheresis product with post-transplant response depth to treatment.

MATERIALS AND METHODS

In a retrospective cross-sectional study, levels of tumor necrosis factor alpha (TNF-α), transforming growth factor beta-1 (TGF-β1) and interferon gamma (IFN-γ) in peripheral hematopoietic stem cells/leukapheresis product (PHSC) of patients with MM eligible for transplantation were evaluated. Association of these cytokines with certain factors such as mobilized CD34 + cells/kg, staging, response to treatment and outcome were analyzed.

RESULTS

The median baseline IFN-γ level was 826.4 pg/mL. IFN-γ levels in the leukapheresis product were significantly lower in patients who achieved complete response (CR) three months post-transplant when compared to patients with very good partial response (VGPR) (674.75 ± 80.32 pg/mL versus 939.6 ± 106.8 pg/mL, p = 0.02), respectively. Patients who lost depth of response at the third-month post-transplant had a median level of IFN-γ 1133, being considered "high-expressors" of IFN-γ, while those reaching improved response were called "low-expressors" (median level IFN-γ 485 pg/mL). Overall and progression-free survival did not have a statistically significant correlation with TNF-α, TGF-β1 or IFN-γ, as well as TNF-α and TGF-β1 levels in post-transplant response assessment.

CONCLUSION

IFN-γ in PHSC seems to be an important biomarker of loss of response in MM, suggesting a role in early post-transplant therapeutic management.

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.

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

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

PD-1 /PD-L1 checkpoint in hematological malignancies

Programmed cell death protein 1 (PD-1), is a cell surface receptor with an important role in down-regulating the immune system and promoting self-tolerance by suppressing T cell inflammatory activity. PD-1/PDL1 axis represents a checkpoint to control immune responses and it is often used as a mechanism of immune escaping by cancers and infectious diseases. Many data demonstrate its important role in solid tumors and report emerging evidences in lymphoproliferative disorders. In this review, we summarized the available data on the role of PD-1/PD-L1 checkpoint in lymphoproliferative diseases and the therapeutics use of monoclonal blocking antibodies.

Mechanisms of Resistance in Multiple Myeloma

Multiple myeloma (MM) is an incurable hematopoietic cancer that is characterized by malignant plasma cell infiltration of the bone marrow and/or extramedullary sites. Multi-modality approaches including "novel agents," traditional chemotherapy, and/or stem cell transplantation are used in MM therapy. Drug resistance, however, ultimately develops and the disease remains incurable for the vast majority of patients. In this chapter, we review both tumor cell-autonomous and non-autonomous (microenvironment-dependent) mechanisms of drug resistance. MM provides an attractive paradigm highlighting a number of current concepts and challenges in oncology. Firstly, identification of MM cancer stem cells and their unique drug resistance attributes may provide rational avenues towards MM eradication and cure. Secondly, the oligoclonal evolution of MM and alternation of "clonal tides" upon therapy challenge our current understanding of treatment responses. Thirdly, the success of MM "novel agents" provides exemplary evidence for the impact of therapies that target the immune and non-immune microenvironment. Fourthly, the rapid pace of drug approvals for MM creates an impetus for development of precision medicine strategies and biomarkers that promote efficacy and mitigate toxicity and cost. While routine cure of the disease remains the ultimate and yet unattainable prize, MM advances in the last 10-15 years have provided an astounding paradigm for the treatment of blood cancers in the modern era and have radically transformed patient outcomes.

CRISPR knock out of programmed cell death protein 1 enhances anti-tumor activity of cytotoxic T lymphocytes

Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that functions to attenuate T cell activation. In this study, we knocked out (KO) PD-1 in cytotoxic T lymphocytes (CTLs) using CRISPR-Cas9 system to evaluate its effect on the anti-tumor activity of the CTLs against multiple myeloma (MM). Results show that PD-1 KO CTLs facilitate apoptosis and caspase activation of the co-cultured MM cells and enhanced MM cell death by 36% compared with the control. PD-1 KO also increased TNF-α and IFN-γ secretion of the CTLs by 2.4 and 1.9-fold respectively. The effectiveness of PD-1 KO in enhancing anti-tumor activity of the CTLs was verified in vivo using mouse xenograft model. The xenografted mice treated with PD-1 KO CTLs demonstrated repressed MM tumor growth and prolonged survival compared with the control group. We conclude that CRISPR-Cas9 is an efficient system to knock out PD-1 from CTLs and PD-1 KO could significantly enhance the anti-tumor activity of CTLs.

Advances in immunotherapy in multiple myeloma

PURPOSE OF REVIEW

Here, we explore the significant progress made in the treatment of multiple myeloma, focusing on immunotherapy and the promise it has offered to patients suffering from advanced disease.

RECENT FINDINGS

Multiple myeloma, a B-cell malignancy, is characterized by unregulated plasma cell growth in the bone marrow as well as strong immunosuppression in the tumor microenvironment. mAbs targeting tumor antigens overcome this, increasing T-cell activation, multiple myeloma cell death, and depth of response. Similarly, adoptive T-cell therapy aims to engineer or isolate tumor-specific T cells for a targeted approach. Finally, peptide and dendritic cell/tumor fusion vaccines reeducate the immune system, expanding the immune response and generating long-term memory to prevent relapse of disease. Many of these approaches have been combined with existing therapies to enhance antitumor immunity.

SUMMARY

Immunotherapeutic approaches have remarkably changed the treatment paradigm for multiple myeloma, and encouraging patient responses have warranted further investigation into mAbs, adoptive T-cell therapy, vaccines, and combination therapy.

Clinical pharmacokinetics of oral drugs in the treatment of multiple myeloma

Treatment of myeloma is a long-term treatment mainly based on all-oral combinations of drugs. Because oral drugs have a more complex pharmacokinetics compared with IV treatments, an appropriate knowledge of the factors that may alter their systemic exposure is of particular clinical relevance. Both drug-drug interactions, food-effect, and dose-adaptation in renal and hepatic impairment may influence the systemic drug levels with a potential impact on drug efficacy or safety. Moreover, a better control of drug exposure may improve the side effect profiles of these treatments with a favourable impact on patient compliance. Furthermore, as long-term treatments, these drugs may also alter the systemic exposure of coadministered medications in these rather old patients. The aim of this review was to identify the factors modifying the systemic exposure of oral drugs used in myeloma by focusing on the pharmacokinetic drug-drug interactions and the effects of renal and hepatic impairment and of food impact.

Emerging Roles of Osteoclasts in the Modulation of Bone Microenvironment and Immune Suppression in Multiple Myeloma

Multiple myeloma (MM) is one of the most common forms of hematologic malignancy resulting from cancerous proliferation of mature malignant plasma cells (MPCs). But despite the real improvement in therapeutics in the past years, it remains largely incurable. MM is the most frequent cancer to involve bone due to the stimulation of osteoclast (OCL) differentiation and activity. OCLs have a unique capacity to resorb bone. However, recent studies reveal that they are not restrained to this sole function. They participate in the control of angiogenesis, medullary niches, and immune responses, including in MM. Therefore, therapeutic approaches targeting OCLs probably affect not only bone resorption but also many other functions, and OCLs should not be considered anymore only as targets to improve the bone phenotype but also to modulate bone microenvironment. In this review, we explore these novel contributions of OCLs to MM which reveal their strong implication in the MM physiopathology. We also underline the therapeutic interest of targeting OCLs not only to overcome bone lesions, but also to improve bone microenvironment and anti-tumoral immune responses.

Safety of ixazomib for the treatment of multiple myeloma

INTRODUCTION

Despite a major positive impact of proteasome inhibitors (PI), such as bortezomib and carfilzomib, on the survival of patients with multiple myeloma (MM) over the last few years, their use in clinical practice is limited by the development of drug resistance, significant side-effects or constraining administration schedules. Ixazomib is the first, and for now the only, oral PI, which was approved by the US Food and Drug Administration in 2015 and by the European Medicines Agency in 2016. Areas covered: In this review, we provide an overview of the preclinical and early-phase studies of ixazomib used as single-agent and in combination. Furthermore, we discuss the results of a recently published pivotal trial, which evaluated the safety profile and clinical benefit of the combination of ixazomib, lenalidomide and dexamethasone versus lenalidomide and dexamethasone alone in 722 patients with relapsed/refractory MM. Expert opinion: Ixazomib combines the comfort of oral administration, substantial clinical efficacy and a good safety profile with manageable side-effects, which mainly comprise low-grade hematological, digestive or cutaneous events, and the agent will therefore play an active part in long-term treatment strategies, both as single agent and as part of combination regimens. Ongoing phase III trials are currently defining its place in first-line, maintenance and relapse settings.

Prognostic value of programmed death-ligand 1 in sarcoma: a meta-analysis

Background

The prognostic role of programmed death-ligand 1 (PD-L1) in sarcoma remains controversial. We performed a meta-analysis so as to investigate the impact of PD-L1 on clinicopathlogical findings and survival outcomes in sarcoma.

Materials and Methods

A comprehensive search in PubMed, Embase and the Cochrane Library was conducted for relevant studies. The odds ratios or hazard ratios, at 95% confidence intervals were used as measures for investigation of the correlation between PD-L1 expression and clinicopathlogical features or survival outcomes.

Results

Fourteen eligible studies comprising 868 patients were selected for analysis. Pooled hazard ratios indicated that the association of PD-L1 expression with overall survival in bone sarcoma (osteosarcoma and chondrosarcoma) patients was statistically significant (1.987, 95% CI: 1.224–3.224, p = 0.005), as was its association with event-free survival in bone and soft-tissue sarcoma patients (3.868, 95% CI: 2.298–6.511, p = 0.000). Additionally, the expression of PD-L1 was positively correlated with the infiltration of programmed death 1 (PD-1) positive T-lymphocytes (OR: 4.012, 95% CI: 2.391–6.733, p = 0.000).

Conclusions

Our meta-analysis indicated that high PD-L1 expression is likely to be a negative factor for patients with sarcomas and that it predicts worse survival outcomes.

Monoclonal Antibodies in Multiple Myeloma: A New Wave of the Future

In 2015, 2 monoclonal antibodies were approved for the treatment of relapsed or refractory multiple myeloma (RRMM), elotuzumab and daratumumab. Elotuzumab is a monoclonal IgG-κ antibody directed against SLAMF7 (signaling lymphocytic activation molecule F7), a cell surface receptor involved in natural killer cell activation. Daratumumab is a monoclonal IgG-κ antibody that binds to CD38, a transmembrane protein found on the surface of myeloma cells and responsible for cellular adhesion and ectoenzymatic activity. Both elotuzumab and daratumumab act through recruitment of the immune system to enhance cellular cytotoxicity directed against myeloma cells. Elotuzumab requires lenalidomide and dexamethasone combined to enhance progression-free survival in patients with RRMM, and daratumumab has both single-agent and combination activity with either lenalidomide or the proteasome inhibitor bortezomib in RRMM. The adverse effect profile of both agents mainly consists of allergic-type infusion reactions. Other considerations for monoclonal antibody use in the treatment of MM include the potential for interference in serum protein electrophoresis testing and cross-reactivity of daratumumab with CD38 present on red blood cells. In the present report, we discussed the clinical development of daratumumab and elotuzumab and newer immunologic approaches to the treatment of MM.

Pembrolizumab, pomalidomide, and low-dose dexamethasone for relapsed/refractory multiple myeloma

Programmed death 1 (PD-1) receptor and its ligand (PD-L1) facilitate immune evasion in multiple myeloma (MM). We hypothesized that pembrolizumab, PD-1-antibody, can enhance antimyeloma cellular immunity generated by pomalidomide, leading to improved clinical responses. In this single-center, phase 2 study, 48 patients with relapsed/refractory MM (RRMM) received 28-day cycles of pembrolizumab, 200 mg IV every 2 weeks, pomalidomide 4 mg daily for 21 days, and dexamethasone 40 mg weekly. Patients had a median of 3 (range: 2-5) lines of therapy, median age 64 (range: 35-83) years, and had received both an immune modulatory drug (IMiD) and proteasome inhibitor: (35 [73%] of 48) were refractory to both; (31 [70%]) had received an autologous transplant, and (30 [62%]) had high-risk cytogenetics. Adverse events grade 3 to 4 occurred in (19 [40%] of 48 patients), including hematologic toxicities (19 [40%]), hyperglycemia (12 [25%]), and pneumonia (7 [15%]). Autoimmune events included pneumonitis (6 [13%]) and hypothyroidism (5 [10%]), mostly ≤ grade 2. Objective responses occurred in (29 [60%] of 48) patients, including stringent complete response/complete response (4 [8%]), very good partial response (9 [19%]), and partial response (16 [33%]); median duration of response was 14.7 months. At median follow-up of 15.6 months, progression-free survival (PFS) was 17.4 months and overall survival was not reached. Analyses of pretreatment marrow samples revealed a trend for increased expression of PD-L1 in responding patients and longer PFS with increased T-lymphocyte infiltrates, irrespective of PD-1 expression. Pembrolizumab, pomalidomide, and low-dose dexamethasone have acceptable safety and durable responses in RRMM patients. This trial was registered at www.clincialtrials.gov as #NCT02289222.

New developments in the treatment of multiple myeloma - clinical utility of daratumumab

Multiple myeloma is a clonal disorder of plasma cells that is currently considered incurable. CD38 is a 46 kDa type II transmembrane glycoprotein that is highly expressed on myeloma cells. Daratumumab is a first in-class human IgG1 monoclonal antibody that targets CD38, and has antimyeloma effects through several mechanisms. Single-agent trials show surprising activity in heavily pretreated myeloma patients. Trials in the relapsed setting, where daratumumab is added to lenalidomide and dexamethasone or bortezomib and dexamethasone, have demonstrated significantly improved progression-free survival with acceptable toxicity. In this review, we discuss the mechanism of action, pharmacology and pharmacokinetics of daratumumab and review the available clinical data in detail. We examine how daratumumab interferes with transfusion testing due to the expression of CD38 on the red blood cells, leading to potential difficulties releasing blood products. Daratumumab also affects disease assessments in multiple myeloma, including serum protein electrophoresis, immunofixation and flow cytometry. Strategies to mitigate these effects are discussed. The optimal use of daratumumab has yet to be decided, and several trials are ongoing in the relapsed and upfront setting. We discuss the potential upfront role of this exciting therapy, which has significant potential for increased minimal residual disease negativity and improved progression-free survival even in high-risk groups.

Multiple myeloma patients in long-term complete response after autologous stem cell transplantation express a particular immune signature with potential prognostic implication

The proportion of multiple myeloma patients in long-term complete response (LTCR-MM) for more than 6 years after autologous stem cell transplantation (ASCT) is small. To evaluate whether this LTCR is associated with a particular immune signature, peripheral blood samples from 13 LTCR-MM after ASCT and healthy blood donors (HBD) were analysed. Subpopulations of T-cells (naïve, effector, central memory and regulatory), B-cells (naïve, marginal zone-like, class-switched memory, transitional and plasmablasts) and NK-cells expressing inhibitory and activating receptors were quantified by multiparametric flow cytometry (MFC). Heavy/light chains (HLC) were quantified by nephelometry. The percentage of CD4⁺ T-cells was lower in patients, whereas an increment in the percentage of CD4⁺ and CD8⁺ effector memory T-cells was associated with the LTCR. Regulatory T-cells and NK-cells were similar in both groups but a particular redistribution of inhibitory and activating receptors in NK-cells were found in patients. Regarding B-cells, an increase in naïve cells and a corresponding reduction in marginal zone-like and class-switched memory B-cells was observed. The HLC values were normal. Our results suggest that LTCR-MM patients express a particular immune signature, which probably reflects a 'high quality' immune reconstitution that could exert a competent anti-tumor immunological surveillance along with a recovery of the humoral immunity.

Network meta-analysis of randomized trials in multiple myeloma: efficacy and safety in relapsed/refractory patients

Despite major therapeutic advancements, multiple myeloma (MM) is still incurable and relapsed/refractory multiple myeloma (RRMM) remains a challenge; the rational choice of the most appropriate regimen in this setting is currently undefined. We performed a systematic review and 2 standard pairwise meta-analyses to evaluate the efficacy of regimens that have been directly compared with bortezomib or immunomodulatory imide drugs (IMiDs) in head-to-head clinical trials and a network meta-analysis (NMA) to determine the relevance of each regimen on the basis of all the available direct and indirect evidence. Sixteen trials were included in the pairwise meta-analyses, and 18 trials were included in the NMA. Pairwise meta-analyses showed that a 3-drug regimen (bortezomib- or IMiD-based) was superior to a 2-drug regimen in progression-free-survival (PFS) and overall response rate (ORR). NMA showed that an IMiD backbone associated with anti-MM monoclonal antibodies (mAbs) (preferably) or proteasome inhibitors had the highest probability of being the most effective regimen with the lowest toxicity. The combination of daratumumab, lenalidomide, and dexamethasone ranked as the first regimen in terms of activity, efficacy, and tolerability according to the average value between surface under the cumulative ranking curve of PFS, overall survival, ORR, complete response rate, and safety. This is the first NMA comparing all currently available regimens evaluated in published randomized trials for the treatment of RRMM, but our results need to be interpreted taking into account differences in their patient populations. Our analysis suggests that IMiDs plus new anti-MM mAb-containing regimens are the most active therapeutic option in RRMM.