Bispecific antibodies targeting CD40 and tumor-associated antigens promote cross-priming of T cells resulting in an antitumor response superior to monospecific antibodies.

BACKGROUND: Indications with poor T-cell infiltration or deficiencies in T-cell priming and associated unresponsiveness to established immunotherapies represent an unmet medical need in oncology. CD40-targeting therapies designed to enhance antigen presentation, generate new tumor-specific T cells, and activate tumor-infiltrating myeloid cells to remodel the tumor microenvironment, represent a promising opportunity to meet this need. In this study, we present the first in vivo data supporting a role for tumor-associated antigen (TAA)-mediated uptake and cross-presentation of tumor antigens to enhance tumor-specific T-cell priming using CD40×TAA bispecific antibodies, a concept we named Neo-X-Prime. METHODS: Bispecific antibodies targeting CD40 and either of two cell-surface expressed TAA, carcinoembryonic antigen-related cell adhesion molecule 5 (CEA) or epithelial cell adhesion molecule (EpCAM), were developed in a tetravalent format. TAA-conditional CD40 agonism, activation of tumor-infiltrating immune cells, antitumor efficacy and the role of delivery of tumor-derived material such as extracellular vesicles, tumor debris and exosomes by the CD40×TAA bispecific antibodies were demonstrated in vitro using primary human and murine cells and in vivo using human CD40 transgenic mice with different tumor models. RESULTS: The results showed that the CD40×TAA bispecific antibodies induced TAA-conditional CD40 activation both in vitro and in vivo. Further, it was demonstrated in vitro that they induced clustering of tumor debris and CD40-expressing cells in a dose-dependent manner and superior T-cell priming when added to dendritic cells (DC), ovalbumin (OVA)-specific T cells and OVA-containing tumor debris or exosomes. The antitumor activity of the Neo-X-Prime bispecific antibodies was demonstrated to be significantly superior to the monospecific CD40 antibody, and the resulting T-cell dependent antitumor immunity was directed to tumor antigens other than the TAA used for targeting (EpCAM). CONCLUSIONS: The data presented herein support the hypothesis that CD40×TAA bispecific antibodies can engage tumor-derived vesicles containing tumor neoantigens to myeloid cells such as DCs resulting in an improved DC-mediated cross-priming of tumor-specific CD8+ T cells. Thus, this principle may offer therapeutics strategies to enhance tumor-specific T-cell immunity and associated clinical benefit in indications characterized by poor T-cell infiltration or deficiencies in T-cell priming.

Tasquinimod modulates suppressive myeloid cells and enhances cancer immunotherapies in murine models.

A major barrier for cancer immunotherapy is the presence of suppressive cell populations in patients with cancer, such as myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM), which contribute to the immunosuppressive microenvironment that promotes tumor growth and metastasis. Tasquinimod is a novel antitumor agent that is currently at an advanced stage of clinical development for treatment of castration-resistant prostate cancer. A target of tasquinimod is the inflammatory protein S100A9, which has been demonstrated to affect the accumulation and function of tumor-suppressive myeloid cells. Here, we report that tasquinimod provided a significant enhancement to the antitumor effects of two different immunotherapeutics in mouse models of cancer: a tumor vaccine (SurVaxM) for prostate cancer and a tumor-targeted superantigen (TTS) for melanoma. In the combination strategies, tasquinimod inhibited distinct MDSC populations and TAMs of the M2-polarized phenotype (CD206(+)). CD11b(+) myeloid cells isolated from tumors of treated mice expressed lower levels of arginase-1 and higher levels of inducible nitric oxide synthase (iNOS), and were less immunosuppressive ex vivo, which translated into a significantly reduced tumor-promoting capacity in vivo when these cells were coinjected with tumor cells. Tumor-specific CD8(+) T cells were increased markedly in the circulation and in tumors. Furthermore, T-cell effector functions, including cell-mediated cytotoxicity and IFNγ production, were potentiated. Taken together, these data suggest that pharmacologic targeting of suppressive myeloid cells by tasquinimod induces therapeutic benefit and provide the rationale for clinical testing of tasquinimod in combination with cancer immunotherapies.

Monotherapeutically nonactive CTLA-4 blockade results in greatly enhanced antitumor effects when combined with tumor-targeted superantigens in a B16 melanoma model.

Immunotherapy aiming to block immune suppression with anti-cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) monoclonal antibodies is a recently clinically established strategy to enhance immune driven antitumor activities. To be successful, this approach depends on the existence of a suppressed immune response against the tumor that can be released by the treatment or alternatively needs to be combined with an immune-enhancing therapy. A tumor-targeted superantigen (TTS) fusion protein utilizes the strong T-cell activating property of bacterial superantigens in concert with the tumor cell binding capacity in antitumor Fab-fragments. Our purpose was to investigate the feasibility of combining anti-CTLA-4 with TTS therapy against the poorly immunogenic B16 mouse melanoma tumor transfected with the human tumor-associated antigen EpCAM recognized by the C215 monoclonal antibody. B16-EpCAM tumors growing in the lung were completely insensitive to anti-CTLA-4 monotherapy. C215Fab-SEA treatment of the B16-EpCAM tumors induced strong infiltration and targeting of both CD4(+) and CD8(+) T cells. In parallel, Foxp3(+)CTLA-4(high) regulatory T cells accumulated in the tumors. Combining activation with C215Fab-SEA and anti-CTLA-4 showed greatly enhanced antitumor effects and prolonged long-term survival. In parallel, when the expansion of regulatory T cells was inhibited, the number of specific effector T cells was enhanced and the cytotoxic T-lymphocyte activity was significantly improved. Collectively, these data emphasize the potential of combining cancer treatment using anti-CTLA-4 monoclonal antibodies with T-cell activation and directed killing by TTS therapy.

Immunotherapy with tumor-targeted superantigens (TTS) in combination with docetaxel results in synergistic anti-tumor effects.

In this study we explored the possibility of combining immunotherapy against cancer with the well-established cytostatic drug docetaxel. Tumor-targeted superantigens (TTS) utilizes the powerful T cell activating property of a superantigen such as staphylococcal enterotoxin A (SEA) in fusion with an anti-tumor Fab-fragment to target this T cell activity against tumor cells. TTS fusion proteins are efficient in a number of experimental tumor models including the B16 mouse melanoma transfected with a human tumor-associated antigen (GA733-2 or EpCam) recognized by the C215 monoclonal antibody. The distinct mechanisms of action of TTS and docetaxel provide the prerequisites for successful combination treatment. However, as a result of the anti-proliferative properties of cytostatic drugs, chemotherapy may modify TTS induced immune activation during combination treatment. Here we evaluated the anti-tumor effects of combining C215Fab-SEA with docetaxel against B16-C215 tumors growing in the lung of C57Bl/6 mice. Both compounds generated a significant reduction in the number of B16-C215 lung tumors when administered alone. Prior treatment with docetaxel at therapeutic doses did not interfere with superantigen induced T cell activation but rather appeared to enhance the response, while simultaneous treatment was suppressive. Combining TTS and docetaxel significantly improved tumor therapy, further reducing the number of lung tumors as compared to mono therapies. Importantly, the combination treatment at timely settings synergistically prolonged long term survival in B16-C215 tumor bearing mice. The results of this study demonstrate that TTS immunotherapy is highly compatible with docetaxel and suggest a significant potential of the combination for human cancer therapy.

Systemic IGF-I administration stimulates the in vivo growth of early, but not advanced, renal cell carcinoma.

Insulin-like growth factor I (IGF-I) is a potent mitogen and antiapoptotic factor. Although elevated serum IGF-I levels have been associated with increased cancer risk, it is not yet clear whether IGF-I sensitivity is sustained throughout tumor progression. To evaluate the biological effects of IGF-I during renal cell carcinoma (RCC) establishment and progression, we administered recombinant human IGF-I to severe combined immuno-deficient mice bearing early or more established Caki-2 human RCC tumors. IGF-I significantly enhanced the tumor growth 2.4-fold when administered early after tumor inoculation. This IGF-I-induced growth was accompanied with enhanced tumor cell proliferation, tumor vascularization, as well as increased intratumoral insulin-like growth factor binding protein 3 (IGFBP-3) and pSmad2 levels. In contrast, IGF-I administrated to more established RCC tumors showed no effect on tumor growth, with subsequently much lower Ki-67, IGFBP-3 and pSmad2 levels. Taken together, these data suggest that systemic IGF-I has potent actions during early RCC tumor development with a sustained long-term effect on proliferation and neovascularization although with progression, later tumors appear to become desensitized to systemic IGF-I effects.

Combining tumor-targeted superantigens with interferon-alpha results in synergistic anti-tumor effects.

In this study we explored the possibility of improving the anti-tumor potency of tumor-targeted superantigens (TTS) by combination treatment with interferon-alpha (IFN-alpha). TTS utilizes the powerful T cell activating property of the superantigen staphylococcal enterotoxin A (SEA) in fusion with an anti-tumor Fab-fragment to target this T cell activity against tumor cells. TTS fusion proteins have shown anti-tumor efficacy in a number of experimental tumor models including the B16 mouse melanoma transfected with a human tumor-associated antigen recognized by the C215 monoclonal antibody. IFN-alpha is approved for the treatment of solid tumors such as renal cell carcinoma and malignant melanoma and exerts immunomodulatory effects, which make it an appropriate candidate to combine with immunotherapy against cancer. Here we report that daily administration of IFN-alpha (20 000 U i.p.) enhances and sustains CD8+ T cell activation induced by the TTS C215Fab-SEA (10 microg i.v.) in C57Bl/6 mice, as reflected by increased and prolonged cell-mediated cytotoxicity against tumor cells ex vivo as well as by augmented serum IFN-gamma levels. C215Fab-SEA synergized with IFN-alpha in reducing the number of lung tumors in B16-C215 melanoma bearing mice as compared to mono therapy. In a long term tumor survival experiment, the prolonged median survival time of the combination treatment was 3.5 and 7.7 times the prolonged median survival times of C215Fab-SEA and IFN-alpha monotherapies, respectively. Hence, the combination treatment provoked synergistic anti-tumor effects as measured by the number of lung tumors and markedly prolonged survival. The enhanced therapeutic efficacy correlated with a striking and sustained increase of CD8- and perforin-expressing tumor-infiltrating cells. These results suggest significant potential of combining TTS with IFN-alpha for human cancer therapy.