Anti-CD40 monoclonal antibody

FcγRs and Their Relevance for the Activity of Anti-CD40 Antibodies

Inhibitory targeting of the CD40L-CD40 system is a promising therapeutic option in the field of organ transplantation and is also attractive in the treatment of autoimmune diseases. After early complex results with neutralizing CD40L antibodies, it turned out that lack of Fcγ receptor (FcγR)-binding is the crucial factor for the development of safe inhibitory antibodies targeting CD40L or CD40. Indeed, in recent years, blocking CD40 antibodies not interacting with FcγRs, has proven to be well tolerated in clinical studies and has shown initial clinical efficacy. Stimulation of CD40 is also of considerable therapeutic interest, especially in cancer immunotherapy. CD40 can be robustly activated by genetically engineered variants of soluble CD40L but also by anti-CD40 antibodies. However, the development of CD40L-based agonists is biotechnologically and pharmacokinetically challenging, and anti-CD40 antibodies typically display only strong agonism in complex with FcγRs or upon secondary crosslinking. The latter, however, typically results in poorly developable mixtures of molecule species of varying stoichiometry and FcγR-binding by anti-CD40 antibodies can elicit unwanted side effects such as antibody-dependent cellular cytotoxicity (ADCC) or antibody-dependent cellular phagocytosis (ADCP) of CD40 expressing immune cells. Here, we summarize and compare strategies to overcome the unwanted target cell-destroying activity of anti-CD40-FcγR complexes, especially the use of FcγR type-specific mutants and the FcγR-independent cell surface anchoring of bispecific anti-CD40 fusion proteins. Especially, we discuss the therapeutic potential of these strategies in view of the emerging evidence for the dose-limiting activities of systemic CD40 engagement.

Novel antibodies targeting immune regulatory checkpoints for cancer therapy

Cancers must evade or suppress the immune system in order to develop. Better understanding of the molecular regulation governing tumour detection and effective activation of the immune system (so called immune regulatory checkpoints) has provided new targets for cancer immunotherapy. Therapeutic monoclonal antibodies against these targets are currently undergoing clinical evaluation with more in pre-clinical development; buoyed by the recent licence approval of the anti-CTLA-4 antibody, ipilumumab, for use in melanoma. This article will review the current status of the various antibodies and target molecules being investigated.

Activation of CD40 by soluble recombinant human CD40 ligand inhibits human glioma cells proliferation via nuclear factor-κB signaling pathway

As CD40 transduces activation signals involved in inflammatory and immune disorders, we explored the expression and response to CD40 engagement in human glioma cell lines in this study. The CD40 expression in BT-325 and U251 cells was flow cytometrically detected. The cells were incubated with srhCD40L for 72 h to assess its effects on cell growth in vitro. TNF-α expression was quantified by real-time PCR, and protein expression was analyzed by ELISA. The I-κb mRNA was detected by RT-PCR. I-κB expression decreased after stimulation with 1 μg/mL srhCD40L, but it was upregulated after the cells were pretreated with CD40 antibody. srhCD40L significantly inhibited the proliferation of the CD40+ human glioma cells. The stimulation of CD40+ glioma cells with soluble CD40L (CD154) up-regulated the expression of TNF-α at both mRNA and protein levels. We are led to conclude that CD40L/CD40 could inhibit human glioma cells through I-κb signaling pathway. Interferon-γ can augment CD40 expression and the inhibitory effect of CD40 ligand on cell growth in vitro. These results suggest that srhCD40L may benefit the therapy strategy of glioma.

New antibody drug treatments for lymphoma

INTRODUCTION

The advent of anti-CD20 monoclonal antibody (mAb) rituximab heralded a new era in the treatment of non-Hodgkin's lymphoma leading to significant improvements in outcome for patients. This unprecedented success has changed the mindset of the clinical community and catalyzed the interest in the pharmaceutical industry to develop the next-generation of antibodies and antibody conjugates in cancer.

AREAS COVERED

There are an ever increasing number of newer generation anti-CD20 and rituximab 'bio-similars' undergoing early phase clinical development. In addition emerging novel therapies including antibody drug conjugates (brentuximab vedotin, SGN-35) and mAb against T-cell lymphomas antigens (e.g., zanolimumab) offer hope of improved outcome for other lymphomas. Bispecific T-cell-engaging antibodies and combination immunotherapy, also provide the promise of further improvements. Radiolabelled antibodies or radioimmunotherapy (RIT) has also demonstrated high clinical activity and two drugs namely 131I-tositumomab (Bexxar) and 90Y-ibritumomab (Zevalin) are licensed.

EXPERT OPINION

Despite the large numbers of new anti-CD20 mAb currently undergoing clinical testing, improving on clinical efficacy of rituximab is a substantial challenge. Further improvements in outcome for patients will require rigorous testing in well designed clinical trials alongside the translation of new insights into mechanism of mAb action that lead to improvements in clinical efficacy.

Activation of tolerogenic dendritic cells in the tumor draining lymph nodes by CD8+ T cells engineered to express CD40 ligand

Tolerogenic dendritic cells in the tumor microenvironment can inhibit the generation and maintenance of robust antitumor T cell responses. In this study, we investigated the effects of local delivery of CD40L by tumor-reactive CD8(+) T cells on dendritic cell activation and antitumor T cell responses in the TRAMP model. To increase the immunostimulatory signal, CD40L was engineered, by deleting the majority of the cytoplasmic domain, to increase its levels of expression and duration on the surface of CD8(+) T cells. Tumor-reactive CD8(+) T cells expressing the truncated form of CD40L stimulated maturation of dendritic cells in vitro and in the prostate draining lymph nodes in vivo. Following dendritic cell maturation, a significantly higher fraction of adoptively transferred, tumor-reactive (reporter) CD8(+) T cells was stimulated to express IFN-gamma and infiltrate the prostate tissue. The antitumor CD8(+) T cell response was further enhanced if TRAMP mice were also immunized with a tumor-specific Ag. These findings demonstrate that augmented T cell responses can be achieved by engineering tumor-reactive T cells to deliver stimulatory signals to dendritic cells in the tumor microenvironment.

Targeting Costimulatory Pathways for Tumor Immunotherapy

Tumor immunotherapy harnesses the potential of the host immune system to recognize and eradicate neoplastic tissue. The efficiency of the immune system in mediating tumor regression depends on the induction of antigen-specific T-cell responses through physiologic immune surveillance, priming by vaccination, or following adoptive transfer of T-cells. Although a variety of tumor-associated antigens have been identified and many immunotherapeutic strategies have been tested, objective clinical responses are rare. The reasons for this include the inability of current immunotherapy approaches to generate efficient T-cell responses, the presence of regulatory cells that inhibit T-cell responses, and other tumor escape mechanisms. The activation of effector T-cells depends on interactions between the T-cell receptor (TCR) and cognate antigen presented as peptides within the major histocompatibility complex (MHC) and costimulatory signals delivered by CD28, which binds to B7.1 and B7.2. More recently, several new molecular receptors and ligands have been identified that integrate into stimulatory or inhibitory activity for T-cells. These signals have been loosely associated with the costimulatory molecules but actually represent a diverse group of molecular pathways that have unique and overlapping functions. This review will focus on these pathways and emphasize their role in mediating T-cell activation for the purpose of enhancing tumor immunotherapy. As we gain a better understanding of the molecular and cellular consequences of T-cell signaling through the costimulatory pathways, a more rational approach to the activation or inhibition of T-cell responses can be developed for the treatment of cancer and other immune-mediated diseases.

Epithelial cells as immune effector cells: the role of CD40

Through the expression of inflammatory mediators and immune-related molecules, epithelial cells function as immune effector cells in a wide variety of tissues; the expression of the CD40 receptor on these cells contributes this role. Engagement of CD40 activates epithelial cells and results in their release of pro- and anti-inflammatory mediators as well as pro-fibrotic molecules. As such, epithelial CD40 has been implicated in the pathogenesis of inflammatory disorders, generation of self-tolerance, and rejection of allografts.

Costimulatory and coinhibitory receptors in anti-tumor immunity

SUMMARY

Despite the expression of antigens by tumor cells, spontaneous immune-mediated rejection of cancer seems to be a rare event. T-cell receptor engagement by peptide/major histocompatibility complexes constitutes the main signal for the activation of naive T cells but is not sufficient to initiate a productive generation and maintenance of effector cells. Full activation of T cells requires additional signals driven by costimulatory molecules present on activated antigen-presenting cells but rarely on tumors. Following the discovery of B7-1 (CD80), several other costimulatory molecules have been shown to contribute to T-cell activation and have relevance for improving anti-tumor immunity. Moreover, increasing the understanding of coinhibitory receptors has highlighted key additional pathways that can dominantly inhibit anti-tumor T-cell function. Improving positive costimulation, and interfering with negative regulation, continues to represent an attractive immunotherapeutic approach for the treatment of cancer. This review focuses upon those pathways with the highest potential for clinical application in human cancer patients.

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.

Levels of CD40 expression on dendritic cells dictate tumour growth or regression

Tumour regression requires activation of T cells. It has been shown that the interaction between T cell-expressed CD40-ligand (CD40-L) and antigen-presenting cell-expressed CD40 plays a crucial role in T cell activation. CD40-L- or CD40-deficient mice are susceptible to tumour growth. CD40-based therapies are also shown to control tumour growth significantly, suggesting that CD40-CD40-L interaction induces anti-tumour T cell responses and tumour regression. We demonstrate that the anti-tumour T cell response can be modulated reciprocally as a function of the levels of CD40 expression. At low expression levels, CD40 promotes tumour growth; at higher expression levels, CD40 induces tumour-regressing T cell response. Dendritic cells (DC) sorted onto major histocompatibility complex (MHC)-II expression are found to be similar in CD40 and CD80 expression. The MHC-II(hi)/CD40(hi) DC induce interleukin (IL)-12-dominated and T helper 1 (Th1)-type response, whereas MHC-II(lo)/CD40(lo) DC promote high IL-10 and Th2-type T cells. The T cells induced by these DC also differ in terms of regulatory T cell markers, lymphocyte activation gene-3 (LAG-3) and glucocorticoid-induced tumour necrosis factor (TNF) receptor family-related gene (GITR). Thus, we report for the first time that CD40-induced effector T cell response depends on CD40 expression levels in vivo.

Immunostimulatory monoclonal antibodies for cancer therapy

Increasing immune responses with immunostimulatory monoclonal antibodies (mAbs) directed to immune-receptor molecules is a new and exciting strategy in cancer therapy. This expanding class of agents functions on crucial receptors, either antagonizing those that suppress immune responses or activating others that amplify immune responses. Complications such as autoimmunity and systemic inflammation are problematic side effects associated with these agents. However, promising synergy has been observed in preclinical models using combinations of immunostimulatory antibodies and other immunotherapy strategies or conventional cancer therapies. Importantly, mAbs of this type have now entered clinical trials with encouraging initial results.

Reduction of plasma sCD40L and stimulated MIP-1-alpha production by in vivo beta-adrenergic stimulation

BACKGROUND

beta-Adrenergic receptor stimulation appears to have contrasting effects on inflammatory processes.

METHODS

In 25 healthy volunteers we examined the effects of a 20-min isoproterenol infusion (20 ng/kg/min) on systemic and peripheral blood mononuclear cell (PBMC) production of LPS-stimulated inflammatory mediators.

RESULTS

Plasma soluble CD40 ligand and stimulated MIP-1alpha production were both reduced (p < or = 0.05) by systemic beta-adrenergic stimulation. Stimulated TNF-alpha production was reduced (p < 0.03) but plasma TNF-alpha was unchanged. In contrast, plasma IL-6 was elevated (p < 0.05) while stimulated IL-6 was unchanged, indicating the main source may not be PBMCs.

CONCLUSIONS

beta-Adrenergic receptor activation leads to a reduction in markers of the early inflammation cascade. Our findings also suggest that adipose tissue is a contributing source of beta-adrenergically stimulated increases in circulating IL-6. Since beta-adrenergic agonists and antagonists are commonly used in the treatment of disease, it is important that we clearly elucidate and contrast their systemic versus cell-specific effects.