Beyond rituximab: The future of monoclonal antibodies in B-cell non-Hodgkin lymphoma

A role for B cells in facilitating defense against an NK cell-sensitive lung metastatic tumor is revealed by stress

Stressors impair immune defenses and pose risks among cancer patients. Natural Killer cells are not the sole immune defense against tumor development. Utilizing an NK-sensitive tumor model, this study evaluated immune effects to stress and determined whether lung metastasis resulted from B cells' inability to augment tumorlytic function. Lung metastasis directly correlated with delayed lung B cell accumulation compared to NK, and T cells. Decreased interleukin-12 cytokine and CD80⁺ molecule expression by B cells correlated with decreased tumor lysis and increased tumor development. Thus, tumor defenses in the lung given stress exposure can depend on the B cell function.

Immuno-pharmacodynamics for evaluating mechanism of action and developing immunotherapy combinations

Immunotherapy has become a major modality of cancer treatment, with multiple new classes of immunotherapeutics recently entering the clinic and obtaining market approval from regulatory agencies. While the promise of these therapies is great, so is the number of possible combinations not only with each other but also with small molecule therapeutics. Furthermore, the observation of unusual dose-response relationships suggests a critical dependency of drug effectiveness on the dosage regimen (dose and schedule). Clinical pharmacodynamic (PD) biomarkers will be useful endpoints for confirming drug mechanism of action, evaluating combination therapies for synergy or antagonism, and identifying optimal dosage regimens. In contrast to conventional PD in which drug action occurs entirely within a single target cell (ie, is self-contained within the malignant cell), immunotherapy involves a complex mechanism of action with sequential steps that propagate through multiple cell types, both normal and malignant. Its intercellular pharmacology begins with molecular target engagement either on an immune effector cell or a malignant cell, followed by stimulatory biochemical and biological signals in immune effector cells, and then finally ends with activation of cell death mechanisms in malignant cells lying within a certain distance from the activated effector cells (immune cell-tumor cell proximity). Evaluating such "trans-cellular pharmacology," in which different steps of drug action are distributed across multiple cell types, requires novel microscopy and image analysis tools capable of quantifying PD-biomarker responses, mapping the responses onto the cellular geography of the tumor using phenotypic biomarkers to identify specific cell types, and finally analyzing the spatial relationships between biomarkers in the context of each cell's biological role. We have termed this form of nearest neighbor image analysis of drug action "proximity PD microscopy," to indicate the importance of the location of the PD-biomarker response within the cellular landscape of a tumor specimen. We discuss herein the major modes of immunotherapy, and lay out a blueprint for using PD assessment to optimize dosage regimens of single agents and guide development of combination immunotherapy regimens, using PD1/PD-L1 immune checkpoint inhibition as a case study.

Future therapies for pemphigus vulgaris: Rituximab and beyond

The conventional treatment for patients with pemphigus vulgaris (PV) centers on global immunosuppression, such as the use of steroids and other immunosuppressive drugs, to decrease titers of antidesmoglein autoantibodies responsible for the acantholytic blisters. Global immunosuppressants, however, cause serious side effects. The emergence of anti-CD20 biologic medications, such as rituximab, as an adjunct to conventional therapy has shifted the focus to targeted destruction of autoimmune B cells. Next-generation biologic medications with improved modes of delivery, pharmacology, and side effect profiles are constantly being developed, adding to the diversity of options for PV treatment. We review promising monoclonal antibodies, including veltuzumab, obinutuzumab (GA-101), ofatumumab, ocaratuzumab (AME-133v), PRO131921, and belimumab.

Epitope interactions of monoclonal antibodies targeting CD20 and their relationship to functional properties

Several novel anti-CD20 monoclonal antibodies are currently in development with the aim of improving the treatment of B cell malignancies. Mutagenesis and epitope mapping studies have revealed differences between the CD20 epitopes recognized by these antibodies. Recently, X-ray crystallography studies confirmed that the Type I CD20 antibody rituximab and the Type II CD20 antibody obinutuzumab (GA101) differ fundamentally in their interaction with CD20 despite recognizing a partially overlapping epitope on CD20. The Type I CD20 antibodies rituximab and ofatumumab are known to bind to different epitopes. The differences suggest that the biological properties of these antibodies are not solely determined by their core epitope sequences, but also depend on other factors, such as the elbow hinge angle, the orientation of the bound antibody and differential effects mediated by the Fc region of the antibody. Taken together, these factors may explain differences in the preclinical properties and clinical efficacy of anti-CD20 antibodies.

Novel CD20 monoclonal antibodies for lymphoma therapy

Rituximab (RTX), a monoclonal antibody (mAb) against CD20, has been widely used for lymphoma therapy. RTX in combination with cyclophosphamide /doxorubicin /vincristine /prednisone (R-CHOP) remains the standard frontline regimen for diffuse large B-cell lymphoma. However, suboptimal response and /or resistance to rituximab have remained a challenge in the therapy of B-cell non-Hodgkin's lymphoma (NHL). Novel agents are under active clinical trials. This review will summarize the latest development in new mAbs against CD20, which include second-generation mAbs, ofatumumab, veltuzumab (IMMU-106), ocrelizumab (PRO70769), and third-generation mAbs, AME-133v (ocaratuzumab), PRO131921 and GA101 (obinutumumab).

Emerging antibody combinations in oncology

The use of monoclonal antibodies (mAbs) has become a general approach for specifically targeting and treating human disease. In oncology, the therapeutic utility of mAbs is usually evaluated in the context of treatment with standard of care, as well as other small molecule targeted therapies. Many anti-cancer antibody modalities have achieved validation, including the targeting of growth factor and angiogenesis pathways, the induction of tumor cell killing or apoptosis, and the blocking of immune inhibitory mechanisms to stimulate anti-tumor responses. But, as with other targeted therapies, few antibodies are curative because of biological complexities that underlie tumor formation and redundancies in molecular pathways that enable tumors to adapt and show resistance to treatment. This review discusses the combinations of antibody therapeutics that are emerging to improve efficacy and durability within a specific biological mechanism (e.g., immunomodulation or the inhibition of angiogenesis) and across multiple biological pathways (e.g., inhibition of tumor growth and induction of tumor cell apoptosis).