The programmed death-1 (PD-1) receptor serves as an immunologic checkpoint, limiting bystander tissue damage and preventing the development of autoimmunity during inflammatory responses. PD-1 is expressed by activated T cells and downmodulates T-cell effector functions upon binding to its ligands, PD-L1 and PD-L2, on antigen-presenting cells. In patients with cancer, the expression of PD-1 on tumor-infiltrating lymphocytes and its interaction with the ligands on tumor and immune cells in the tumor microenvironment undermine antitumor immunity and support its rationale for PD-1 blockade in cancer immunotherapy. This report details the development and characterization of nivolumab, a fully human IgG4 (S228P) anti-PD-1 receptor-blocking monoclonal antibody. Nivolumab binds to PD-1 with high affinity and specificity, and effectively inhibits the interaction between PD-1 and its ligands. In vitro assays demonstrated the ability of nivolumab to potently enhance T-cell responses and cytokine production in the mixed lymphocyte reaction and superantigen or cytomegalovirus stimulation assays. No in vitro antibody-dependent cell-mediated or complement-dependent cytotoxicity was observed with the use of nivolumab and activated T cells as targets. Nivolumab treatment did not induce adverse immune-related events when given to cynomolgus macaques at high concentrations, independent of circulating anti-nivolumab antibodies where observed. These data provide a comprehensive preclinical characterization of nivolumab, for which antitumor activity and safety have been demonstrated in human clinical trials in various solid tumors. Cancer Immunol Res; 2(9); 846-56. Ó2014 AACR.

B-cell maturation antigen (BCMA) is a highly plasma cell-selective protein that is expressed on malignant plasma cells of multiple myeloma (MM) patients and therefore is an ideal target for T-cell redirecting therapies. We developed a bispecific T-cell engager (BiTE) targeting BCMA and CD3ε (BI 836909) and studied its therapeutic impacts on MM. BI 836909 induced selective lysis of BCMApositive MM cells, activation of T cells, release of cytokines and T-cell proliferation; whereas BCMA-negative cells were not affected. Activity of BI 836909 was not influenced by the presence of bone marrow stromal cells, soluble BCMA or a proliferation-inducing ligand (APRIL). In ex vivo assays, BI 836909 induced potent autologous MM cell lysis in both, newly diagnosed and relapsed/ refractory patient samples. In mouse xenograft studies, BI 836909 induced tumor cell depletion in a subcutaneous NCI-H929 xenograft model and prolonged survival in an orthotopic L-363 xenograft model. In a cynomolgus monkey study, administration of BI 836909 led to depletion of BCMA-positive plasma cells in the bone marrow. Taken together, these results show that BI 836909 is a highly potent and efficacious approach to selectively deplete BCMA-positive MM cells and represents a novel immunotherapeutic for the treatment of MM.

The monoclonal antibodies ipilimumab (anti-CTLA-4) and nivolumab (anti-PD-1) have shown remarkable antitumor activity in an increasing number of cancers. When combined, ipilimumab and nivolumab have demonstrated superior activity in patients with metastatic melanoma (CHECKMATE-067). Here we describe the preclinical development strategy that predicted these clinical results. Synergistic antitumor activity in mouse MC38 and CT26 colorectal tumor models was observed with concurrent, but not sequential CTLA-4 and PD-1 blockade. Significant antitumor activity was maintained using a fixed dose of anti-CTLA-4 antibody with decreasing doses of anti-PD-1 antibody in the MC38 model. Immunohistochemical and flow cytometric analyses confirmed that CD3+ T cells accumulated at the tumor margin and infiltrated the tumor mass in response to the combination therapy, resulting in favorable effector and regulatory T-cell ratios, increased pro-inflammatory cytokine secretion, and activation of tumor-specific T cells. Similarly, in vitro studies with combined ipilimumab and nivolumab showed enhanced cytokine secretion in superantigen stimulation of human peripheral blood lymphocytes and in mixed lymphocyte response assays. In a cynomolgus macaque toxicology study, dose-dependent immune-related gastrointestinal inflammation was observed with the combination therapy; this response had not been observed in previous single agent cynomolgus studies. Together, these in vitro assays and in vivo models comprise a preclinical strategy for the identification and development of highly effective antitumor combination immunotherapies.

IntroductionThe induction and maintenance of immune responses to antigens is tightly regulated. Activation of T cells requires the interaction between the T-cell receptor and the antigen presented on the surface of an antigen-presenting cell (APC; first signal) and engagement of CD28 (second signal) by the costimulatory molecules B7-1 (CD80) and B7-2 (CD86). 1,2 Costimulation is particularly important for the initial T-cell response, promoting proliferation and survival. Following antigen stimulation, both CD28 and its negative regulatory, cytotoxic T lymphocyte antigen-4 (CTLA-4), are up-regulated on the cell surface and compete for their ligands, B7-1 and B7-2. CTLA-4 binds to both B7-1 and B7-2 with higher (10-to 20-fold) affinity than CD28, 3,4 and, in contrast to CD28, CTLA-4 suppresses T-cell activation. However, competition with CD28 for the costimulatory molecules is not likely to be the main mechanism responsible for CTLA-4 immunoregulatory activity. [5][6][7] Several lines of evidence suggest that expression of CTLA-4 by CD25 ϩ CD4 ϩ regulatory T (T reg ) cells plays a role in controlling peripheral T-cell tolerance and differentiation. 8,9 T reg cells are CD4 ϩ T lymphocytes that express high levels of the interleukin-2 (IL-2) receptor ␣-chain (CD25), and constitutively express CTLA-4. T reg cells inhibit the proliferation of T cells through contactdependent or cytokine-mediated (IL-10, transforming growth factor-␤ [TGF-␤]) inhibition of T-cell responses. 10 T reg cells can induce activation of the enzyme IDO in APCs via CTLA-4-mediated ligation of CD80/CD86. 11,12 IDO confers immunosuppressive activity to APCs. 11,12 Two mechanisms have been suggested as mediators of the T-cellsuppressive action of IDO 13 : degradation and consequent reduction of tryptophan, an essential amino acid required for T-cell proliferation; and generation of inhibitory tryptophan metabolites. Blocking CTLA-4 signals with monoclonal antibodies may provide an important tool to influence the host immune response in clinical settings. For example, synergy between anti-CD25 and anti-CTLA-4 monoclonal antibodies has been shown to be effective in antitumor therapy. 14,15 T reg cells may suppress a potentially successful adaptive host immune response to a pathogen. [16][17][18][19][20][21] In the case of HIV infection, CTLA-4 expression is higher in patients with advanced clinical symptoms compared with asymptomatic individuals, 22,23 and the frequency of CTLA-4-expressing CD25 ϩ CD4 ϩ T reg cells is increased in lymphoid tissues in untreated individuals infected with HIV-1. 24 Primary infection of macaques with simian immunodeficiency virus (SIV) is associated with an increase in T reg cells, IDO, TGF-␤, and IL-10. 25 Similarly, chronic SIV infection is associated with an accumulation of T reg cells in lymphoid tissues, including the gut, and an increased level of immunosuppressive cytokines (A. B., M. V., A. H., D. F., J. N., Valentina Cecchinato, G. F., G. M. S., and C. C., our unpublished results, October 2006).Here, we examined...

MDX-060 was well tolerated at doses up to 15 mg/kg. MDX-060 has limited activity as a single agent, but the minimal toxicity observed and the significant proportion of patients with stable disease suggests that further study of MDX-060 in combination with other therapies is warranted.