Human anti-CD40 antagonist antibody triggers significant antitumor activity against human multiple myeloma

Emerging strategies for targeting cell adhesion in multiple myeloma

Multiple myeloma (MM) is an incurable hematological cancer involving proliferation of abnormal plasma cells that infiltrate the bone marrow (BM) and secrete monoclonal antibodies. The disease is clinically characterized by bone lesions, anemia, hypercalcemia, and renal failure. MM is presently treated with conventional therapies like melphalan, doxorubicin, and prednisone; or novel therapies like thalidomide, lenalidomide, and bortezomib; or with procedures like autologous stem cell transplantation. Unfortunately, these therapies fail to eliminate the minimal residual disease that remains persistent within the confines of the BM of MM patients. Mounting evidence indicates that components of the BM-including extracellular matrix, cytokines, chemokines, and growth factors-provide a sanctuary for subpopulations of MM. This co-dependent development of the disease in the context of the BM not only ensures the survival and growth of the plasma cells but contributes to de novo drug resistance. In addition, by fostering homing, angiogenesis, and osteolysis, this crosstalk plays a critical role in the progression of the disease. Not surprisingly then, over the past decade, several strategies have been developed to disrupt this communication between the plasma cells and the BM components including antibodies, peptides, and inhibitors of signaling pathways. Ultimately, the goal is to use these therapies in combination with the existing antimyeloma agents in order to further reduce or abolish minimal residual disease and improve patient outcomes.

Class-specific effector functions of therapeutic antibodies

Physiology usually combines polyclonal antibodies of multiple classes in a single humoral response. Beyond their common ability to bind antigens, these various classes of human immunoglobulins carry specific functions which can each serve specific goals. In many cases, the function of a monoclonal therapeutic antibody may thus be modulated according to the class of its constant domains. Depending on the immunoglobulin class, different functional assays will be used in order to evaluate the functional activity of a monoclonal antibody.

Emerging targeted therapies for lymphoid malignancies

CONTEXT

Our understanding of molecular events in the pathogenesis of hematologic malignancies has evolved substantially. The research data gathered in the past 3 decades have led to the definition of neoplastic disorders based on specific genetic and molecular alterations, which is reflected in the current World Health Organization's classification of tumors of hematopoietic and lymphoid tissues. Moreover, there have been dramatic successes in the development and implementation of therapies that specifically target the proteins and signaling cascades affected by tumor-specific genetic alterations.

OBJECTIVE

To review the development of select, novel therapies for lymphoid malignancies.

DATA SOURCES

We examine examples from the recent literature in targeting 4 major regulatory pathways: tyrosine kinase activation, transcription factor activity, apoptotic signaling, and histone acetylation in both preclinical models and early-stage (stage 1 and 2) clinical trials.

CONCLUSION

Given the successes of novel compounds that target signaling pathways critical to the growth and survival of lymphoid tumor cells, the routine clinical use of molecularly targeted therapies for the treatment of lymphoid malignancies is likely in the near future.

CD48 as a novel molecular target for antibody therapy in multiple myeloma

Monoclonal antibody (mAb) drugs are desirable for the improvement of multiple myeloma (MM) treatment. In this study, we found for the first time that CD48 was highly expressed on MM plasma cells. In 22 out of 24 MM patients, CD48 was expressed on more than 90% of MM plasma cells at significantly higher levels than it was on normal lymphocytes and monocytes. CD48 was only weakly expressed on some CD34(+) haematopoietic stem/progenitor cells, and not expressed on erythrocytes or platelets. We next examined whether CD48 could serve as a target antigen for mAb therapy against MM. A newly generated in-house anti-CD48 mAb induced mild antibody-dependent cell-mediated cytotoxicity and marked complement-dependent cytotoxicity against not only MM cell lines but also primary MM plasma cells in vitro. Administration of the anti-CD48 mAb significantly inhibited tumour growth in severe combined immunodeficient mice inoculated subcutaneously with MM cells. Furthermore, anti-CD48 mAb treatment inhibited growth of MM cells transplanted directly into murine bone marrow. Finally and importantly, we demonstrated that the anti-CD48 mAb did not damage normal CD34(+) haematopoietic stem/progenitor cells. These results suggest that the anti-CD48 mAb has the potential to become an effective therapeutic mAb against MM.

Polyclonal rabbit anti-murine plasmacytoma cell globulins induce myeloma cells apoptosis and inhibit tumour growth in mice

Multiple myelomas (MMs) are etiologically heterogeneous and there are limited treatment options; indeed, current monoclonal antibody therapies have had limited success, so more effective antibodies are urgently needed. Polyclonal antibodies are a possible alternative because they target multiple antigens simultaneously. In this study, we produced polyclonal rabbit anti-murine plasmacytoma cell immunoglobulin (PAb) by immunizing rabbits with the murine plasmacytoma cell line MPC-11. The isolated PAb bound to plasma surface antigens in several MM cell lines, inhibited their proliferation as revealed by MTT assay, and induce apoptosis as indicated by flow cytometry, microscopic observation of apoptotic changes in morphology, and DNA fragmentation on agarose gels. The cytotoxicity of PAb on MPC-11 cell lines was both dose-dependent and time-dependent; PAb exerted a 50% inhibitory effect on MPC-11 cell viability at a concentration of 200 µg/ml in 48 h. Flow cytometry demonstrated that PAb treatment significantly increased the number of apoptotic cells (48.1%) compared with control IgG (8.3%). Apoptosis triggered by PAb was confirmed by activation of caspase-3, -8, and -9. Serial intravenous or intraperitoneal injections of PAb inhibited tumour growth and prolonged survival in mice bearing murine plasmacytoma, while TUNEL assay demonstrated that PAb induced statistically significant apoptosis (P < 0.05) compared to control treatments. We conclude that PAb is an effective agent for in vitro and in vivo induction of apoptosis in multiple myeloma and that exploratory clinical trials may be warranted.

Monoclonal antibody-based therapy as a new treatment strategy in multiple myeloma

The introduction of autologous stem cell transplantation combined with the introduction of immunomodulatory drugs (IMiDs) and proteasome inhibitors has significantly improved survival of multiple myeloma patients. However, ultimately the majority of patients will develop refractory disease, indicating the need for new treatment modalities. In preclinical and clinical studies, promising results have been obtained with several monoclonal antibodies (mAbs) targeting the myeloma tumor cell or the bone marrow microenvironment. The mechanisms underlying the therapeutic efficacy of these mAbs include direct induction of tumor cell apoptosis via inhibition or activation of target molecules, complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC). The capability of IMiDs to enhance ADCC and the modulation of various important signaling cascades in myeloma cells by both bortezomib and IMiDs forms the rationale to combine these novel agents with mAbs as new treatment strategies for myeloma patients. In this review, we will give an overview of various mAbs directly targeting myeloma tumor cells or indirectly via effects on the bone marrow microenvironment. Special focus will be on the combination of these mAbs with IMiDs or bortezomib.

Treatment options for relapsed and refractory multiple myeloma

Treatment options for patients with relapsed myeloma have benefited from the development of new targeted agents. The use of bortezomib, thalidomide, and lenalidomide have dramatically changed outcomes for patients with relapsed myeloma. New agents are also in development, on the basis of preclinical rationale, as well as combinations of conventional and novel agents. Together each of these treatment approaches are being tested in phase I, II, and III clinical trials, with the goal of prolonged duration of remission and, ultimately, improved overall survival.

Monoclonal antibodies in the treatment of multiple myeloma

Despite recent advances in treatment that have significantly improved overall survival, multiple myeloma (MM) remains incurable. Although rituximab, the first monoclonal antibody (MAb) evaluated in MM treatment, provided only very limited benefit, research is ongoing into a number of other MAbs directed against a variety of MM-related target antigens. Given the inherent immune dysfunction associated with MM, newer strategies that may enhance immune function in conjunction with antibodies may also provide a more fruitful clinical approach. Potential MAb targets in MM include growth factors and their receptors, other signalling molecules, and antigens expressed exclusively or predominantly on MM cells. MAb therapy involves a range of mechanisms, including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, interference with receptor-ligand interactions, and MAb conjugation to radioisotopes or toxins. The antigens currently targeted in MM therapy are discussed, along with the development status of the corresponding MAb therapeutics. Elotuzumab, an anti-CS1 MAb, has recently achieved clinically meaningful responses when combined with lenalidomide or bortezomib in patients with relapsed and relapsed/refractory MM. Other MAbs are also showing early promise. More ongoing clinical research is required to identify optimal combination regimens and biomarkers that may help predict response to specific MAb-based combinations.

Advances in the treatment of monoclonal gammopaties: The emerging role of targeted therapy in plasma cell dyscrasias

The paradigm for the treatment of monoclonal gammopaties has dramatically changed: therapeutic options in multiple myeloma (MM) have evolved from the introduction of melphalan and prednisone in the 1960s, high-dose chemotherapy and stem cell transplantation in the late 1980s and 1990s, to the rapid introduction of small novel molecules within the last seven years. Based on the understanding of the complex interaction of the MM cells with the bone marrow microenvironment and the signaling pathways that are dysregulated in this process, a number of novel therapeutic agents are now available. Specifically, three novel agents with a specific-targeted anti-MM activity, have been FDA-approved for the treatment of this disease, namely Bortezomib, thalidomide, and lenalidomide which are now all playing a key role in the treatment of MM. The success of targeted therapy in MM has since led to the development and investigation of more than 30 new compounds in this disease and in other plasma cell dyscrasias such as Waldenström’s macroglobulinemia and primary amyloidosis, both in the preclinical settings and as part of clinical trials.

Surface molecule CD229 as a novel target for the diagnosis and treatment of multiple myeloma

BACKGROUND

To date, multiple myeloma remains an incurable malignancy due to the persistence of minimal residual disease in the bone marrow. In this setting, monoclonal antibodies against myeloma-specific cell surface antigens represent a promising therapeutic approach, which is however hampered by a lack of appropriate target structures expressed across all pathogenic myeloma cell populations. We, therefore, investigated functionally relevant immunoreceptors specifically associated with myeloma cells as well as their clonogenic precursors.

DESIGN AND METHODS

Potential target proteins were identified using antibody arrays against phosphorylated immunoreceptors with lysates from myeloma cell lines. CD229 expression was confirmed in primary myeloma cells by reverse transcriptase polymerase chain reaction, western blot, fluorescence-activated cell sorting, and immunohistochemistry. Apoptosis, clonogenic growth, and sensitivity to chemotherapy were determined following short-interfering RNA-mediated downregulation of CD229. Antibody-dependent cellular and complement-dependent cytotoxicity were analyzed using a monoclonal antibody against CD229 to demonstrate the antigen's immunotherapeutic potential.

RESULTS

Our screening assay identified CD229 as the most strongly over-expressed/phosphorylated immunoreceptor in myeloma cell lines. Over-expression was further demonstrated in the CD138-negative population, which has been suggested to represent myeloma precursors, as well as on primary tumor cells from myeloma patients. Accordingly, CD229 staining of patients' bone marrow samples enabled the identification of myeloma cells by flow cytometry and immunohistochemistry. Down-regulation of CD229 led to a decreased number of viable myeloma cells and clonal myeloma colonies, and enhanced the anti-tumor activity of conventional chemotherapeutics. Targeting CD229 with a monoclonal antibody resulted in complement- and cell-mediated lysis of myeloma cells.

CONCLUSIONS

Our results demonstrate that the immunoreceptor CD229 is specifically over-expressed on myeloma cells including their clonogenic precursors and contributes to their malignant phenotype. Monoclonal antibodies against this protein may represent a promising diagnostic and immunotherapeutic instrument in this disease.

Pathogenesis of myeloma

Multiple myeloma (MM) is a neoplasm of post-germinal center, terminally differentiated B cells. It is characterized by a multifocal proliferation of clonal, long-lived plasma cells within the bone marrow (BM) and associated skeletal destruction, serum monoclonal gammopathy, immune suppression, and end-organ sequelae. MM is preceded by an age-progressive premalignant condition termed monoclonal gammopathy of undetermined significance. Unlike the genomes of most hematological malignancies, and similar to those of solid-tissue neoplasms, MM genomes are typified by numerous structural and numerical chromosomal aberrations as well as mutations in a number of oncogenes and tumor-suppressor genes, some of which have been linked to disease pathogenesis and clinical behavior. Recent studies have also defined the importance of interactions between the MM cells and their BM microenvironment, dysregulation in signaling pathways and in a specialized subpopulation of cells within the tumor (termed myeloma cancer stem cells) for tumor cell growth and survival, and the development of resistance to therapy.

Advances in the assessment and control of the effector functions of therapeutic antibodies

The Fc (crystallizable fragment) region of therapeutic antibodies can have an important role in their safety and efficacy. Although much is known about the structure-activity relationship of antibodies and the factors that influence Fc effector functions, a process has not yet been defined to clearly delineate how Fc functionality should be assessed and controlled during antibody development and manufacturing. In this article, we summarize the current knowledge of antibody Fc functionality, provide a strategy for assessing the effector functions of different classes of therapeutic antibodies (including Fc fusion proteins) and propose a path for routine testing and controls for manufacturers of antibody products.

Antibody-based therapies in multiple myeloma

The unmet need for improved multiple myeloma (MM) therapy has stimulated clinical development of monoclonal antibodies (mAbs) targeting either MM cells or cells of the bone marrow (BM) microenvironment. In contrast to small-molecule inhibitors, therapeutic mAbs present the potential to specifically target tumor cells and directly induce an immune response to lyse tumor cells. Unique immune-effector mechanisms are only triggered by therapeutic mAbs but not by small molecule targeting agents. Although therapeutic murine mAbs or chimeric mAbs can cause immunogenicity, the advancement of genetic recombination for humanizing rodent mAbs has allowed large-scale production and designation of mAbs with better affinities, efficient selection, decreasing immunogenicity, and improved effector functions. These advancements of antibody engineering technologies have largely overcome the critical obstacle of antibody immunogenicity and enabled the development and subsequent Food and Drug Administration (FDA) approval of therapeutic Abs for cancer and other diseases.

Novel immunotherapies

Multiple myeloma is still a fatal disease. Despite advances in high-dose chemotherapy and stem-cell transplantation and the development of novel therapeutics, relapse of the underlying disease remains the primary cause of treatment failure. Strategies for posttransplantation immunomodulation are desirable for eradication of remaining tumor cells. To this end, immunotherapy aimed at inducing myeloma-specific immunity in patients has been explored. Idiotype protein, secreted by myeloma cells, has been the primary target for immunotherapy as it is the best defined tumor-specific antigen. This chapter focuses on novel immunotherapies that are being developed to treat patients with myeloma. I will discuss potential myeloma antigens, antigen-specific T cells, and their function on myeloma tumor cells, and T-cell-based and antibody-based immunotherapies for myeloma. Furthermore, clinical studies of T-cell-based immunotherapy in the form of vaccination, allogeneic stem-cell transplantation and donor lymphocyte infusions, with or without donor vaccination using patient-derived idiotype, and future application of donor-derived or patient-derived, antigen-specific T-cell infusion in this disease are also discussed. Based on the specificity of the immune effector molecules and cells, immunotherapies with specific T cells or therapeutic antibodies may represent novel strategies for the treatment of multiple myeloma in the near future.

The CD40-CD154 interaction would correlate with proliferation and immune escape in pancreatic ductal adenocarcinoma

BACKGROUND

CD40 and CD154 are associated with lymphocyte signaling pathways and they are also expressed in some malignant neoplasms, but the significance in pancreatic cancer is unknown.

METHODS

Eighty pancreatic cancer specimens were stained immunohistochemically, and the results were correlated with the patients' clinicopathologic features. Subsequently, in vitro analysis of CD40-CD154 signaling was performed.

RESULT

Immunohistochemical analysis of tumor cells showed that 29 patients (36.3%) were positive for CD40, and 17 patients (21.3%) had very high CD154 expression. The survival of patients who had very high CD154 expression was significantly better than that of others (P = 0.0198). Univariate and multivariate analysis revealed that very high CD154 expression in cancer cells was not an independent, favorable prognostic factor (risk ratio, 0.493; P = 0.0224). On in vitro proliferation assay, the growth of PK-45P and KP-4 cells was blocked by CD40 and CD154 blocking antibodies. Moreover, on in vitro cytokine assay, Th-2 cytokines from PK-45P and SUIT-2 were blocked by CD40 or CD154 blocking antibody.

CONCLUSION

These results suggest that the CD40-CD154 interaction would correlate with cell proliferation and secretion of cytokines in PDAC cells, and CD154 overexpression could be a favorable prognostic factor in PDAC patients.

Utility of flow cytometry immunophenotyping in multiple myeloma and other clonal plasma cell-related disorders

In recent years, multiparameter flow cytometry (MFC) immunophenotyping has become mandatory in the clinical management of hematological malignancies, both for diagnostic and monitoring purposes. Multiple myeloma (MM) and other clonal plasma cell-related (PC) disorders should be no exception to this paradigm, but incorporation of immunophenotypic studies in the management of patients with PC disorders is still far from being routinely established in many diagnostic flow cytometry laboratories. For clonal PC disorders, MFC is of clear and established clinical relevance in: (1) the differential diagnosis between MM and other PC-related disorders; (2) the identification of high-risk MGUS and smoldering MM; (3) minimal residual disease investigation after therapy; additionally it may also be useful for (4) the definition of prognosis-associated antigenic profiles; and (5) the identification of new therapeutic targets. In this article, we review the clinical value of MFC in the study of PC disorders, with specific emphasis in those areas where consensus exists on the need to incorporate MFC into routine evaluation of MM and other clonal PC-related disorders.

Humoral immunotherapy of multiple myeloma: perspectives and perplexities

IMPORTANCE OF THE FIELD

Multiple myeloma (MM) is a hematological malignancy still remaining incurable despite the various therapies available, mainly because of the high fraction of refractory/relapsing cases. Therefore, the development of novel therapeutic approaches is urgently needed to overcome conventional treatment resistance.

AREAS COVERED IN THIS REVIEW

In the era of targeted therapies, treatments combining a high specificity for neoplastic cells and the capability to interfere with environmental signals should be regarded as the weapons of choice. Monoclonal antibody (mAb)-based humoral immunotherapy could satisfy both these requirements when applied to MM. Indeed, many of the molecules expressed on MM cells, such as CD38, CD40, CD49d, CD138 and CD162 are involved in the adhesive dynamics regulating the crosstalk between MM and the BM-microenvironment.

WHAT THE READER WILL GAIN

In this study we review those MM-associated molecules that have shown promising antitumor effects as targets of specific mAbs in preclinical settings, thus deserving to be considered for clinical investigation.

TAKE HOME MESSAGE

mAbs directed against MM-associated adhesion markers should be taken into account in clinical practice, since they could possibly represent the best available combination of tumor cytotoxicity, environmental signal deprivation and immune system redirection.

Fc-engineered anti-CD40 antibody enhances multiple effector functions and exhibits potent in vitro and in vivo antitumor activity against hematologic malignancies

CD40 is highly expressed on various B-lineage malignancies and represents an attractive immunotherapy target for neoplastic disease. Previous work showed that engineering the Fc domain of an antibody for increased binding to Fcγ receptors (FcγRs) significantly enhanced Fc-mediated immune effector function and antitumor activity in vitro and in vivo. We developed a humanized anti-CD40 antibody similarly Fc-engineered for increased FcγR binding (XmAbCD40) and compared its efficacy with that of an anti-CD40 native IgG1 analog and the anti-CD20 antibody rituximab. XmAbCD40 increased antibody-dependent cell-mediated cytotoxicity (ADCC) up to 150-fold relative to anti-CD40 IgG1 against B-lymphoma, leukemia, and multiple myeloma cell lines, and significantly enhanced ADCC against primary tumors. XmAbCD40 was also superior to rituximab in enhancing ADCC (both in cell lines and primary tumors) and in augmenting antibody-dependent cellular phagocytosis. XmAbCD40 significantly inhibited lymphoma growth in disseminated and established mouse xenografts and was more effective than the IgG1 analog or rituximab. An anti-CD40 antibody constructed to abrogate FcγR binding showed no reduction of tumor growth, indicating that the in vivo antitumor activity of XmAbCD40 is primarily mediated via FcγR-dependent mechanisms. These data demonstrate that XmAbCD40 displays potent antitumor efficacy and merits further evaluation for the treatment of CD40(+) malignancies.

Adhesion molecules--The lifelines of multiple myeloma cells

Multiple myeloma is an incurable hematological malignancy of terminally differentiated immunoglobulin-producing plasma cells. As a common presentation of the disease, the malignant plasma cells accumulate and proliferate in the bone marrow, where they disrupt normal hematopoiesis and bone physiology. Multiple myeloma cells and the bone marrow microenvironment are linked by a composite network of interactions mediated by soluble factors and adhesion molecules. Integrins and syndecan-1/CD138 are the principal multiple myeloma receptor systems of extracellular matrix components, as well as of surface molecules of stromal cells. CD44 and RHAMM are the major hyaluronan receptors of multiple myeloma cells. The SDF-1/CXCR4 axis is a key factor in the homing of multiple myeloma cells to the bone marrow. The levels of expression and activity of these adhesion molecules are controlled by cytoplasmic operating mechanisms, as well as by extracellular factors including enzymes, growth factors and microenvironmental conditions. Several signaling responses are activated by adhesive interactions of multiple myeloma cells, and their outcomes affect the survival, proliferation and migration of these cells, and in many cases generate a drug-resistant phenotype. Hence, the adhesion systems of multiple myeloma cells are attractive potential therapeutic targets. Several approaches are being developed to disrupt the activities of adhesion molecules in multiple myeloma cells, including small antagonist molecules, direct targeting by immunoconjugates, stimulation of immune responses against these molecules, and signal transduction inhibitors. These potential novel therapeutics may be incorporated into current treatment schemes, or directed against minimal residual malignant cells during remission.

Blockade of the MEK/ERK signalling cascade by AS703026, a novel selective MEK1/2 inhibitor, induces pleiotropic anti-myeloma activity in vitro and in vivo

This study investigated the cytotoxicity and mechanism of action of AS703026, a novel, selective, orally bioavailable MEK1/2 inhibitor, in human multiple myeloma (MM). AS703026 inhibited growth and survival of MM cells and cytokine-induced osteoclast differentiation more potently (9- to 10-fold) than AZD6244. Inhibition of proliferation induced by AS703026 was mediated by G0-G1 cell cycle arrest and was accompanied by reduction of MAF oncogene expression. AS703026 further induced apoptosis via caspase 3 and Poly ADP ribose polymerase (PARP) cleavage in MM cells, both in the presence or absence of bone marrow stromal cells (BMSCs). Importantly, AS703026 sensitized MM cells to a broad spectrum of conventional (dexamethasone, melphalan), novel or emerging (lenalidomide, perifosine, bortezomib, rapamycin) anti-MM therapies. Significant tumour growth reduction in AS703026- vs. vehicle-treated mice bearing H929 MM xenograft tumours correlated with downregulated pERK1/2, induced PARP cleavage, and decreased microvessels in vivo. Moreover, AS703026 (<200 nmol/l) was cytotoxic against the majority of tumour cells tested from patients with relapsed and refractory MM (84%), regardless of mutational status of RAS and BRAF genes. Importantly, BMSC-induced viability of MM patient cells was similarly blocked within the same dose range. Our results therefore support clinical evaluation of AS703026, alone or in combination with other anti-MM agents, to improve patient outcome.

Vaccination with immature dendritic cells combined with CD40mAb induces protective immunity against B lymphoma in hu-SCID mice

Dendritic cells (DCs) pulsed by tumor antigens have been widely used as tumor vaccines to specifically trigger the cytotoxicity of CD8+ T cells. But the tumor microenviroment with enriched immunosuppressants hampered DC maturation and co-stimulation. CD40/CD40L signaling, one of the most important co-stimulatory molecules is capable of effectively skewing the immune response by promoting DCs maturation and co-stimulation. To establish a novel specific immunotherapeutic approach for the use of DC vaccine in the treatment of B lymphoma, hu-SCID mice bearing B lymphoma were vaccinated by different combination of tumor antigen pulsed DC or imDC vaccines and immune-enhancing agencies such as agonist CD40mAb and T cells. The results of immature DCs combined with agonistic CD40mAb were encouraging with achievement of tumor regression and induction of antigen-specific immune responses. These findings demonstrated the potential utility of imDC-based tumor vaccination combining with agonistic CD40mAb in the treatment of malignant lymphoma.

Future directions in immunomodulatory therapy

The role of immunomodulatory-based therapy with thalidomide or lenalidomide is clearly established in the management of patients with myeloma in all phases of their disease. Recent preclinical and clinical works have demonstrated that in addition to combination therapy with dexamethasone, there is significant activity when combined with the proteasome inhibitor bortezomib. More recent clinical studies have also demonstrated significant activity when combined with akt inhibitors, HDAC inhibitors, and even monoclonal antibodies. Further clinical development of immunomodulatory agents should continue to be based on preclinical rationale, which has resulted in a number of promising and clinically active combinations.

CD40 and autoimmunity: the dark side of a great activator

CD40 is a tumor necrosis factor receptor superfamily member expressed by immune and non-immune cells. CD40:CD154 interactions mediate T-dependent B cell responses and efficient T cell priming. Thus, CD40 is a likely candidate to play roles in autoimmune diseases in which activated T and B cells cause pathology. Diseases in which CD40 plays a pathogenic role include autoimmune thyroiditis, type 1 diabetes, inflammatory bowel disease, psoriasis, multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. This review discusses the role of CD40:CD154 interaction in human and mouse autoimmunity, human polymorphisms associated with disease incidence, and disrupting CD40:CD154 interactions as an autoimmune therapy.

Identification, characterisation and regulation by CD40 activation of novel CD95 splice variants in CD95-apoptosis-resistant, human, B-cell non-Hodgkin's lymphoma

CD95 gene and splicing aberrations have been detected in B-cell non-Hodgkin lymphoma (B-NHL) where they are thought to contribute to CD95 apoptosis resistance. To further investigate this, we have performed extensive CD95 transcript sequencing and functional analysis in B-NHL with demonstrated resistance to CD95-induced apoptosis (B-NHLr). Strikingly, instead of showing CD95 mutations per se, B cells from B-NHLr co-expressed wild-type and multiple, normal (CD95nv) and novel alternatively spliced variant CD95 transcripts (CD95av). CD95av were predicted, by sequencing, to encode soluble, potentially apoptosis inhibitory proteins. However, their overexpression, by transfection, in Jurkat cells did not interfere with endogenous CD95 death signalling. Furthermore, CD95av-expressing B-NHLr did not show mutations in CD95 splice-regulatory elements and CD95av expression was 'reversible' by CD40 activation. This, in conjunction with treatment by the protein synthesis inhibitor, cycloheximide, could sensitise a subset of B-NHLr to CD95 apoptosis. In normal and lymphoma B cells, this correlated to increased CD95 membrane expression, enhanced DISC activity and engagement of the mitochondrial death pathway via Bid cleavage, although the latter occurred less efficiently in B-NHLr. Thus, immune modulation of CD95 transcription and alternative splicing combined with enhanced engagement of mitochondrial death signalling offer potential for restoration of CD95 apoptosis sensitivity in B-NHLr.

Combinatorial efficacy of anti-CS1 monoclonal antibody elotuzumab (HuLuc63) and bortezomib against multiple myeloma

Monoclonal antibody (mAb) therapy for multiple myeloma, a malignancy of plasma cells, has not been clinically efficacious in part due to a lack of appropriate targets. We recently reported that the cell surface glycoprotein CS1 (CD2 subset 1, CRACC, SLAMF7, CD319) was highly and universally expressed on myeloma cells while having restricted expression in normal tissues. Elotuzumab (formerly known as HuLuc63), a humanized mAb targeting CS1, is currently in a phase I clinical trial in relapsed/refractory myeloma. In this report we investigated whether the activity of elotuzumab could be enhanced by bortezomib, a reversible proteasome inhibitor with significant activity in myeloma. We first showed that elotuzumab could induce patient-derived myeloma cell killing within the bone marrow microenvironment using a SCID-hu mouse model. We next showed that CS1 gene and cell surface protein expression persisted on myeloma patient-derived plasma cells collected after bortezomib administration. In vitro bortezomib pretreatment of myeloma targets significantly enhanced elotuzumab-mediated antibody-dependent cell-mediated cytotoxicity, both for OPM2 myeloma cells using natural killer or peripheral blood mononuclear cells from healthy donors and for primary myeloma cells using autologous natural killer effector cells. In an OPM2 myeloma xenograft model, elotuzumab in combination with bortezomib exhibited significantly enhanced in vivo antitumor activity. These findings provide the rationale for a clinical trial combining elotuzumab and bortezomib, which will test the hypothesis that combining both drugs would result in enhanced immune lysis of myeloma by elotuzumab and direct targeting of myeloma by bortezomib.

Pleiotropic anti-myeloma activity of ITF2357: inhibition of interleukin-6 receptor signaling and repression of miR-19a and miR-19b

BACKGROUND

The histone deacetylase inhibitor ITF2357 has potent cytotoxic activity in multiple myeloma in vitro and has entered clinical trials for this disease.

DESIGN AND METHODS

In order to gain an overall view of the activity of ITF2357 and identify specific pathways that may be modulated by the drug, we performed gene expression profiling of the KMS18 multiple myeloma cell line treated with the drug. The modulation of several genes and their biological consequence were verified in a panel of multiple myeloma cell lines and cells freshly isolated from patients by using polymerase chain reaction analysis and western blotting.

RESULTS

Out of 38,500 human genes, we identified 140 and 574 up-regulated genes and 102 and 556 down-modulated genes at 2 and 6 h, respectively, with a significant presence of genes related to transcription regulation at 2 h and to cell cycling and apoptosis at 6 h. Several of the identified genes are particularly relevant to the biology of multiple myeloma and it was confirmed that ITF2357 also modulated their encoded proteins in different multiple myeloma cell lines. In particular, ITF2357 down-modulated the interleukin-6 receptor alpha (CD126) transcript and protein in both cell lines and freshly isolated patients' cells, whereas it did not significantly modify interleukin-6 receptor beta (CD130) expression. The decrease in CD126 expression was accompanied by decreased signaling by interleukin-6 receptor, as measured by STAT3 phosphorylation in the presence and absence of inter-leukin-6. Finally, the drug significantly down-modulated the MIRHG1 transcript and its associated microRNA, miR-19a and miR-19b, known to have oncogenic activity in multiple myeloma.

CONCLUSIONS

ITF2357 inhibits several signaling pathways involved in myeloma cell growth and survival.

Growth inhibition of human multiple myeloma cells by an oncolytic adenovirus carrying the CD40 ligand transgene

PURPOSE

The growth-inhibitory activity of recombinant CD40 ligand (CD40L) is well documented in human multiple myeloma (MM). We examined MM-targeted delivery of CD40L by a conditional replicative oncolytic adenovirus, AdEHCD40L.

EXPERIMENTAL DESIGN

The growth-regulatory activity of AdEHCD40L was determined in vitro and in vivo. Differential analysis with AdEHCD40L and parental virus (AdEHNull)-infected cultures allowed the identification of cellular and molecular pathways modulated by the CD40L transgene.

RESULTS

Conditional expression of viral E1A and CD40L transgene was shown in human MM lines RPMI 8226 [interleukin (IL)-6 independent] and Kas-6/1 (IL-6 dependent) under hypoxic conditions commonly found in MM in situ. AdEHCD40L inhibited MM cell growth more effectively than AdEHNull. This enhanced growth-inhibitory activity was abrogated by cotreatment with a CD40L antibody. Chemoresistant MM lines (MR20 and LR5) were similarly susceptible to AdEHCD40L treatment. AdEHCD40L induced apoptosis and S-phase cell cycle blockade while uniquely up-regulating the previously described proapoptotic elements tumor necrosis factor-related apoptosis-inducing ligand, Fas, and IL-8. Intratumoral injections of AdEHCD40L reduced the growth of severe combined immunodeficient/hu RPMI 8226 xenografts by >50% compared with 28% reduction by AdEHNull. Adenoviral hexon and CD40L were detected in AdEHCD40L-treated tumors at day 35 after infection primarily in necrotic areas, suggesting viral replicative activity.

CONCLUSIONS

These findings show that CD40L acts in concert with viral oncolysis to produce MM growth inhibition through activation of cellular apoptosis. The direct growth-inhibitory activity of AdEHCD40L, together with the well-known immune-potentiating features of CD40L, may be clinically applicable for the experimental treatment of MM or plasma cell leukemia.

Preparation and characterization of a novel chimeric antibody against human CD40 with the potential to inhibit Daudi cell proliferation

5C11, a murine monoclonal antibody with a high specificity for human CD40 molecule, is a promising candidate for cancer targeting therapy. We have therefore attempted to construct a humanized antibody of 5C11 to minimize its immunogenicity for potential clinical use. A chimeric version of 5C11 (ch-5C11) was generated by transferring these mouse variable regions onto a human framework. This chimeric antibody retained reactivity to human CD40. In vitro, ch-5C11 could effectively inhibit B lymphoma Daudi cell proliferation, suggesting that it might have the potential to be developed for future clinical use.

The monoclonal antibody nBT062 conjugated to cytotoxic Maytansinoids has selective cytotoxicity against CD138-positive multiple myeloma cells in vitro and in vivo

PURPOSE

We investigated the antitumor effect of murine/human chimeric CD138-specific monoclonal antibody nBT062 conjugated with highly cytotoxic maytansinoid derivatives against multiple myeloma (MM) cells in vitro and in vivo.

EXPERIMENTAL DESIGN

We examined the growth inhibitory effect of BT062-SPDB-DM4, BT062-SMCC-DM1, and BT062-SPP-DM1 against MM cell lines and primary tumor cells from MM patients. We also examined in vivo activity of these agents in murine MM cell xenograft model of human and severe combined immunodeficient (SCID) mice bearing implant bone chips injected with human MM cells (SCID-hu model).

RESULTS

Anti-CD138 immunoconjugates significantly inhibited growth of MM cell lines and primary tumor cells from MM patients without cytotoxicity against peripheral blood mononuclear cells from healthy volunteers. In MM cells, they induced G(2)-M cell cycle arrest, followed by apoptosis associated with cleavage of caspase-3, caspase-8, caspase-9, and poly(ADP-ribose) polymerase. Nonconjugated nBT062 completely blocked cytotoxicity induced by nBT062-maytansinoid conjugate, confirming that specific binding is required for inducing cytotoxicity. Moreover, nBT062-maytansinoid conjugates blocked adhesion of MM cells to bone marrow stromal cells. The coculture of MM cells with bone marrow stromal cells protects against dexamethasone-induced death but had no effect on the cytotoxicity of immunoconjugates. Importantly, nBT062-SPDB-DM4 and nBT062-SPP-DM1 significantly inhibited MM tumor growth in vivo and prolonged host survival in both the xenograft mouse models of human MM and SCID-hu mouse model.

CONCLUSION

These results provide the preclinical framework supporting evaluation of nBT062-maytansinoid derivatives in clinical trials to improve patient outcome in MM.

CS1 promotes multiple myeloma cell adhesion, clonogenic growth, and tumorigenicity via c-maf-mediated interactions with bone marrow stromal cells

CS1 is highly expressed on tumor cells from the majority of multiple myeloma (MM) patients regardless of cytogenetic abnormalities or response to current treatments. Furthermore, CS1 is detected in MM patient sera and correlates with active disease. However, its contribution to MM pathophysiology is undefined. We here show that CS1 knockdown using lentiviral short-interfering RNA decreased phosphorylation of ERK1/2, AKT, and STAT3, suggesting that CS1 induces central growth and survival signaling pathways in MM cells. Serum deprivation markedly blocked survival at earlier time points in CS1 knockdown compared with control MM cells, associated with earlier activation of caspases, poly(ADP-ribose) polymerase, and proapoptotic proteins BNIP3 and BIK. CS1 knockdown further delayed development of MM tumor and prolonged survival in mice. Conversely, CS1 overexpression promoted myeloma cell growth and survival by significantly increasing myeloma adhesion to bone marrow stromal cells (BMSCs) and enhancing myeloma colony formation in semisolid culture. Moreover, CS1 increased c-maf-targeted cyclin D2-dependent proliferation, -integrin beta7/alphaE-mediated myeloma adhesion to BMSCs, and -vascular endothelial growth factor-induced bone marrow angiogenesis in vivo. These studies provide direct evidence of the role of CS1 in myeloma pathogenesis, define molecular mechanisms regulating its effects, and further support novel therapies targeting CS1 in MM.

Human-like mouse models for testing the efficacy and safety of anti-beta2-microglobulin monoclonal antibodies to treat myeloma

PURPOSE

We showed recently that anti-beta2-microglobulin (beta2M) monoclonal antibodies (mAb) have remarkably strong apoptotic effects on myeloma cells in vitro and in SCID-hu mice. However, whether the mAbs will be therapeutic and safe in the treatment of myeloma patients, in whom every tissue expresses low densities of MHC class I molecules and elevated levels of soluble beta2M are present, remains to be determined.

EXPERIMENTAL DESIGN

In this study, human-like myeloma mouse models (HLA-A2-transgenic NOD/SCID mice) were developed, which express mature and functional human MHC class I (HLA-A2 and human beta2M) on murine organs and present high levels of circulating human beta2M derived from human myeloma cells. Myeloma-bearing mice were treated intraperitoneally with anti-beta2M mAbs, and the distribution and effects of the mAbs on normal organs and established tumors were examined.

RESULTS

Our results show that anti-beta2M mAbs were effective in suppressing myeloma growth in treated mice. The therapeutic efficacy of the mAbs in these mice are comparable with those observed in myeloma-bearing nontransgenic NOD/SCID mice in which no human MHC class I is expressed on murine organs. Furthermore, although the mAbs can be detected on different organs, no tissue damage or cell apoptosis was observed in the mice.

CONCLUSION

Based on the antimyeloma efficacy and low toxicity in the mice, our study suggests that anti-beta2M mAbs may be safe and the tissue-expressing and soluble beta2M may not compromise their therapeutic effects in myeloma patients. This study provides further support for the future application of the mAbs as therapeutic agents for multiple myeloma.

Targeted therapies in multiple myeloma

Increasing knowledge of the biology of multiple myeloma led the way for the development of novel drugs that have changed the management of the disease. New treatments target not only to the malignant plasma cell but also target the interactions of myeloma cells with their microenvironment. Several preclinical studies have identified potential targets and drugs are developed that act on pathways crucial for myeloma cell survival, proliferation, migration and drug resistance. The identification of active agents in the laboratory is followed by rationally designed clinical studies that validate these drugs, either as single agents or in combinations with other active drugs. These novel agents may be either small molecules or monoclonal antibodies targeting receptors, kinase activity of receptors or key molecules within critical pathways, intracellular maintenance mechanisms and immune modulation.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

Bone marrow microenvironment and the identification of new targets for myeloma therapy

The development of multiple myeloma (MM) is a complex multi-step process involving both early and late genetic changes in the tumor cell as well as selective supportive conditions by the bone marrow (BM) microenvironment. Indeed, it is now well established that MM cell-induced disruption of the BM homeostasis between the highly organized cellular and extracellular compartments supports MM cell proliferation, survival, migration and drug resistance through activation of various signaling (for example, PI3K/Akt, JAK/Stat-, Raf/MEK/MAPK-, NFkappaB- and Wnt-) pathways. Based on our enhanced understanding of the functional importance of the MM BM microenvironment and its inter-relation with the MM cell resulting in homing, seeding, proliferation and survival, new molecular targets have been identified and derived treatment regimens in MM have already changed fundamentally during recent years. These agents include thalidomide, its immunomodulatory derivative lenalidomide and the proteasome inhibitor bortezomib, which mediate tumor cytotoxicity in the BM milieu. Ongoing studies are further delineating MM pathogenesis in the BM to enhance cytotoxicity, avoid drug resistance and improve patient outcome.

New drugs in multiple myeloma: mechanisms of action and phase I/II clinical findings

The outcome of multiple myeloma has substantially improved over the past decade, mainly due to recently approved drugs, such as thalidomide, lenalidomide, and bortezomib. Nevertheless, most patients still relapse and, therefore, drugs with new mechanisms of action are urgently needed to overcome this resistance. In this Review, we discuss some of the new targeted therapeutic strategies under assessment in preclinical and clinical studies in multiple myeloma. Unfortunately, the single-agent clinical activity of most of these new drugs has been limited; nevertheless, their effectiveness might be enhanced by their rational combination with each other or with conventional agents.

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

Currently, no approved monoclonal antibody (mAb) therapies exist for human multiple myeloma (MM). Here we characterized cell surface CS1 as a novel MM antigen and further investigated the potential therapeutic utility of HuLuc63, a humanized anti-CS1 mAb, for treating human MM. CS1 mRNA and protein was highly expressed in CD138-purified primary tumor cells from the majority of MM patients (more than 97%) with low levels of circulating CS1 detectable in MM patient sera, but not in healthy donors. CS1 was expressed at adhesion-promoting uropod membranes of polarized MM cells, and short interfering RNA (siRNA) targeted to CS1 inhibited MM cell adhesion to bone marrow stromal cells (BMSCs). HuLuc63 inhibited MM cell binding to BMSCs and induced antibody-dependent cellular cytotoxicity (ADCC) against MM cells in dose-dependent and CS1-specific manners. HuLuc63 triggered autologous ADCC against primary MM cells resistant to conventional or novel therapies, including bortezomib and HSP90 inhibitor; and pretreatment with conventional or novel anti-MM drugs markedly enhanced HuLuc63-induced MM cell lysis. Administration of HuLuc63 significantly induces tumor regression in multiple xenograft models of human MM. These results thus define the functional significance of CS1 in MM and provide the preclinical rationale for testing HuLuc63 in clinical trials, either alone or in combination.

The antileukemia activity of a human anti-CD40 antagonist antibody, HCD122, on human chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia (B-CLL) is a lymphoproliferative disorder characterized by the surface expression of CD20, CD5 antigens, as well as the receptor CD40. Activation of CD40 by its ligand (CD40L) induces proliferation and rescues the cells from spontaneous and chemotherapy-induced apoptosis. CD40 activation also induces secretion of cytokines, such as IL-6, IL-10, TNF-alpha, IL-8, and GM-CSF, which are involved in tumor cell survival, migration, and interaction with cells in the tumor microenvironment. Here we demonstrate that in primary B-CLL tumor cells, the novel antagonist anti-CD40 monoclonal antibody, HCD122, inhibits CD40L-induced activation of signaling pathways, proliferation and survival, and secretion of cytokines. Furthermore, HCD122 is also a potent mediator of antibody-dependent cellular cytotoxicity (ADCC), lysing B-CLL cells more efficiently than rituximab in vitro, despite a significantly higher number of cell surface CD20 binding sites compared with CD40. Unlike rituximab, however, HCD122 (formerly CHIR-12.12) does not internalize upon binding to the cells. Our data suggest that HCD122 may inhibit B-CLL growth by blocking CD40 signaling and by ADCC-mediated cell lysis.

Immunotherapy opportunities in ovarian cancer

Ovarian cancer is responsible for the majority of gynecologic cancer deaths and despite the highest standard of multimodality therapy with surgery and cytotoxic chemotherapy, long-term survival remains low. With compelling evidence that epithelial ovarian cancer is an immunogenic tumor capable of stimulating an antitumor immune response, renewed efforts to develop immune therapies to augment the efficacy of traditional therapies are underway. Current immunotherapies focus on varied modes of antitumor vaccine development, particularly with the use of dendritic cell vaccines, effective methods for adoptive T-cell transfer and combinatorial approaches with immune modulatory therapy subverting natural tolerance mechanisms or boosting effector mechanisms. Additional combinatorial approaches include the use of cytokines and/or chemotherapy with immune therapy.

Targeting NF-kappaB in Waldenstrom macroglobulinemia

The nuclear factor-kappaB (NF-kappaB) path-way has been implicated in tumor B-cell survival, growth, and resistance to therapy. Because tumor cells overcome single-agent antitumor activity, we hypothesized that combination of agents that target differentially NF-kappaB pathway will induce significant cytotoxicity. Therapeutic agents that target proteasome and Akt pathways should induce significant activity in B-cell malignancies as both pathways impact NF-kappaB activity. We demonstrated that perifosine and bortezomib both targeted NF-kappaB through its recruitment to the promoter of its target gene IkappaB using chromatin immunoprecipitation assay. This combination led to synergistic cytotoxicity in Waldenstrom macroglobulinemia (WM) cells that was mediated through a combined reduction of the PI3K/Akt and ERK signaling pathways, found to be critical for survival of WM cells. Moreover, a combination of these drugs with the CD20 monoclonal antibody rituximab further increased their cytotoxic activity. Thus, effective WM therapy may require combination regimens targeting the NF-kappaB pathway.

Anti-CD20 monoclonal antibody therapy in multiple myeloma

CD20 is a particularly appealing target that is expressed on the surface of almost all B cells, with no significant shedding, secretion or internalization. In contrast to the demonstrated efficacy of anti-CD20 strategies in various B-cell lymphoproliferative disorders, the role of such therapy in multiple myeloma is undetermined and controversial. The expression of CD20 by myeloma cells is heterogeneous, and can be detected only in 13-22% of patients. However, there is increasing interest in testing anti-CD20 therapy in myeloma because of recent studies suggesting the existence of clonogenic CD20-positive precursor B cells in the disease. This article reviews the rationale, preclinical and clinical activity of anti-CD20 therapy in myeloma. Clinical trials show that anti-CD20 therapy with rituximab elicits a partial response in approximately 10% of CD20+ patients with multiple myeloma. In addition, there is preliminary evidence of disease stabilization in 50-57% of CD20+ patients for a period of 10-27 months. Further large-scale clinical trials are therefore needed to establish the role of this promising strategy in the treatment of myeloma.

Identification of a strongly activating human anti-CD40 antibody that suppresses HIV type 1 infection

We characterized the functional properties of a novel set of human anti-CD40 monoclonal antibodies originating from a human phage display library and identified an antibody that strongly activates cells via the CD40 receptor for potential use in HIV therapy. The anti-CD40 antibodies were converted from a single chain antibody fragment format (scFv) to an IgG format and produced in HEK293 cells, and the binding characteristics were evaluated. Next, their ability to (1) rescue a human B cell line from induced apoptosis, (2) stimulate B cell proliferation, and (3) block the CD40-CD40L interaction was determined. Finally, the most activating anti-CD40 antibody was tested for its ability to block HIV-1 infection in a monocyte-derived cell line. The different anti-CD40 antibodies, A24, B44, E30, F33, and A2-54, displayed a wide variety of binding and functional properties. In particular, B44 showed a very strong ability to activate normal human B cells and, in addition, did not block the CD40-CD40L interaction. This antibody was able to suppress HIV-1 infection in a human cell line (MonoMac 1) and may be a potential therapeutic candidate in HIV infection.

Human monoclonal antibodies from transgenic mice

Since the 1986 regulatory approval of muromonomab-CD3, a mouse monoclonal antibody (MAb) directed against the T cell CD3epsilon antigen, MAbs have become an increasingly important class of therapeutic compounds in a variety of disease areas ranging from cancer and autoimmune indications to infectious and cardiac diseases. However, the pathway to the present acceptance of therapeutic MAbs within the pharmaceutical industry has not been smooth. A major hurdle for antibody therapeutics has been the inherent immunogenicity of the most readily available MAbs, those derived from rodents. A variety of technologies have been successfully employed to engineer MAbs with reduced immunogenicity. Implementation of these antibody engineering technologies involves in vitro optimization of lead molecules to generate a clinical candidate. An alternative technology, involving the engineering of strains of mice to produce human instead of mouse antibodies, has been emerging and evolving for the past two decades. Now, with the 2006 US regulatory approval of panitumumab, a fully human antibody directed against the epidermal growth factor receptor, transgenic mice expressing human antibody repertoires join chimerization, CDR grafting, and phage display technologies, as a commercially validated antibody drug discovery platform. With dozens of additional transgenic mouse-derived human MAbs now in clinical development, this new drug discovery platform appears to be firmly established within the pharmaceutical industry.

From the bench to the bedside: emerging new treatments in multiple myeloma

Within the last decade, several novel classes of anti-myeloma therapeutics have become available. The clinical successes achieved by thalidomide, lenalidomide, and the proteasome inhibitor bortezomib, and in particular the ability of these agents to lead to major clinical responses in patients resistant to conventional or high-dose chemotherapy, have highlighted the importance of expanding further the spectrum of classes of agents utilized for the treatment of myeloma. Herein, we review the current status for the development of novel anti-myeloma agents, with emphasis on classes of therapeutics which have already translated into clinical trials or those in advanced stages of preclinical development. These include second-generation proteasome inhibitors (NPI-0052 and PR-171), heat shock protein 90 (hsp90) inhibitors, 2-methoxyestradiol, histone deacetylase (HDAC) inhibitors (e.g. SAHA and LBH589), fibroblast growth factor receptor 3 (FGF-R3) inhibitors, insulin-like growth factor 1 receptor (IGF-1R) inhibitors, mTOR inhibitors, monoclonal antibodies, and agents specifically targeting the tumor microenvironment, such as defibrotide.

Modulating co-stimulation

The modulation of co-stimulatory pathways represents a novel therapeutic strategy to regulate autoimmune diseases. Auto-reactive CD4+ T cells play a critical role in initiating the immune response leading to inflammation and autoimmune diseases. Blocking co-stimulatory signals prevents T-cell activation, thus diminishing autoimmune responses and possibly preventing the progression of autoimmune disease. Blockade of several co-stimulatory pathways has been investigated in animal models and has led to clinical trials testing specific blocking agents in humans. In this review we will describe the role of co-stimulatory pathways, primarily the CD28-B7 pathway, in autoimmune diseases, and we will present in vivo and in vitro studies supporting the efficacy of co-stimulation blockade in animal models of autoimmune disease. Finally, we will discuss the clinical therapeutic efficacy of blocking monoclonal antibodies in preventing or reducing auto-antigen driven T-cell activation in humans with particular attention to the CD28/B7 pathway. Inhibiting co-stimulatory molecule interactions by using monoclonal antibodies seems to be an original approach to regulate autoimmune diseases in humans.

Building better magic bullets--improving unconjugated monoclonal antibody therapy for cancer

The potential of monoclonal antibodies to effectively treat cancer is beginning to be widely acknowledged. Advances in antibody engineering make it possible to produce various recombinant proteins that exploit the specificity of the antibody-combining site to manipulate tumour-related signalling, and to stimulate anti-tumour immune responses. Future advances in the field will rely on the improved identification of functional antibody targets to perturb cancer-relevant signalling, and by the improved selection of tumours that can be effectively treated. These advances will be complemented by the use of antibodies that induce clinically meaningful host-protective immune responses. But, can we afford this progress?

Understanding multiple myeloma pathogenesis in the bone marrow to identify new therapeutic targets

Multiple myeloma is a plasma cell malignancy characterized by complex heterogeneous cytogenetic abnormalities. The bone marrow microenvironment promotes multiple myeloma cell growth and resistance to conventional therapies. Although multiple myeloma remains incurable, novel targeted agents, used alone or in combination, have shown great promise to overcome conventional drug resistance and improve patient outcome. Recent oncogenomic studies have further advanced our understanding of the molecular pathogenesis of multiple myeloma, providing the framework for new prognostic classification and identifying new therapeutic targets.