Contributions
Abstract: EP937
Type: E-Poster Presentation
Session title: Myeloma and other monoclonal gammopathies - Biology & Translational Research
Background
Immunotherapy using monoclonal antibodies (mAbs) has improved clinical outcomes of patients with multiple myeloma (MM). Nevertheless, the prognosis of relapsed/refractory MM (RRMM) patients still remains poor probably due to the heterogeneity of myeloma cells, highlighting the need for the development of novel therapeutic approaches. Recently, new antibody-based modalities have been developed, and tested in clinical trials for RRMM. Bispecific T-cell engager (BiTE) which can induce antitumor T-cell responses has a potential to treat RRMM. In contrast, some issues would be raised to improve advantages of this modality. First, BiTE lacks an Fc domain which needs to induce NK-cell responses. Second, BiTE is continuously administered to induce sufficient antitumor effects because of its low molecular weight. Third, BiTE can target an antigen expressed by tumor cells, suggesting the weakness against heterogenous tumors. To overcome these obstacles, we have developed a novel BiTE-based modality, Bridging-BiTE (B-BiTE), which endows a series of clinically available mAbs with both NK-cell and T-cell activation capacity.
Aims
In this study, we have investigated the efficacy, universality, and safety of a mAb armed with B-BiTE for the treatment of MM.
Methods
B-BiTE, which encodes a single chain fragment variable (scFv) specific for an Fc domain and an scFv specific for the CD3ε, was designed. B-BiTE was mixed with a mAb at the molar ratio of 1:1 to generate B-BiTE/mAb complex. Proliferation and cytokine production by human peripheral blood T cells/NK cells for target cells in the presence of B-BiTE/mAb was measured by flow cytometry. Their cytotoxicity against target cells was assessed by 51Cr-release assays. Five-week-old NOG mice were inoculated with MM1S myeloma cells. Then, antitumor effects and overall survivals of mice treated with a mAb alone or B-BiTE/mAb were compared.
Results
Using the CD20-specific mAb, Rituximab as a model, we have demonstrated that B-BiTE/Rituximab successfully bound to both CD20+ tumor cells and human T cells, and activated human peripheral blood T cells as well as NK cells against tumor cells in vitro. Therefore, we applied B-BiTE to the CD38-specific mAb, Daratumumab (Dar) and the SLAMF7-specific mAb, Elotuzumab (Elo) to target myeloma cells. Human peripheral blood CD8+ and CD4+ T cells proliferated, and produced multiple cytokines against both CD38+SLAMF7- and CD38-SLAMF7+ myeloma cells in the presence of B-BiTE/Dar and B-BiTE/Elo without increasing the frequency of regulatory T cells. Moreover, their antitumor cytotoxicity induced by B-BiTE/Dar and B-BiTE/Elo was enhanced when compared with that mediated by Dar/Elo alone in vitro and in vivo. Importantly, human peripheral blood T cells and NK cells obtained from patients with myeloma cooperatively responded to their own myeloma cells in the presence of B-BiTE/mAb. Furthermore, in the presence of polyclonal immunoglobulin, B-BiTE/mAb activated T cells/NK cells for myeloma cells, but did not induce any reactivity to normal cells.
Conclusion
B-BiTE can be a new modality to easily generate stable, safe, and effective bispecific antibodies from clinically available mAbs. This modality can allow us to prepare a panel of next-generation antibodies which induce both T-cell and NK-cell responses, resulting in further advancement of immunotherapy for RRMM.
Keyword(s): Antibody, Bispecific, Immunotherapy, Myeloma
Abstract: EP937
Type: E-Poster Presentation
Session title: Myeloma and other monoclonal gammopathies - Biology & Translational Research
Background
Immunotherapy using monoclonal antibodies (mAbs) has improved clinical outcomes of patients with multiple myeloma (MM). Nevertheless, the prognosis of relapsed/refractory MM (RRMM) patients still remains poor probably due to the heterogeneity of myeloma cells, highlighting the need for the development of novel therapeutic approaches. Recently, new antibody-based modalities have been developed, and tested in clinical trials for RRMM. Bispecific T-cell engager (BiTE) which can induce antitumor T-cell responses has a potential to treat RRMM. In contrast, some issues would be raised to improve advantages of this modality. First, BiTE lacks an Fc domain which needs to induce NK-cell responses. Second, BiTE is continuously administered to induce sufficient antitumor effects because of its low molecular weight. Third, BiTE can target an antigen expressed by tumor cells, suggesting the weakness against heterogenous tumors. To overcome these obstacles, we have developed a novel BiTE-based modality, Bridging-BiTE (B-BiTE), which endows a series of clinically available mAbs with both NK-cell and T-cell activation capacity.
Aims
In this study, we have investigated the efficacy, universality, and safety of a mAb armed with B-BiTE for the treatment of MM.
Methods
B-BiTE, which encodes a single chain fragment variable (scFv) specific for an Fc domain and an scFv specific for the CD3ε, was designed. B-BiTE was mixed with a mAb at the molar ratio of 1:1 to generate B-BiTE/mAb complex. Proliferation and cytokine production by human peripheral blood T cells/NK cells for target cells in the presence of B-BiTE/mAb was measured by flow cytometry. Their cytotoxicity against target cells was assessed by 51Cr-release assays. Five-week-old NOG mice were inoculated with MM1S myeloma cells. Then, antitumor effects and overall survivals of mice treated with a mAb alone or B-BiTE/mAb were compared.
Results
Using the CD20-specific mAb, Rituximab as a model, we have demonstrated that B-BiTE/Rituximab successfully bound to both CD20+ tumor cells and human T cells, and activated human peripheral blood T cells as well as NK cells against tumor cells in vitro. Therefore, we applied B-BiTE to the CD38-specific mAb, Daratumumab (Dar) and the SLAMF7-specific mAb, Elotuzumab (Elo) to target myeloma cells. Human peripheral blood CD8+ and CD4+ T cells proliferated, and produced multiple cytokines against both CD38+SLAMF7- and CD38-SLAMF7+ myeloma cells in the presence of B-BiTE/Dar and B-BiTE/Elo without increasing the frequency of regulatory T cells. Moreover, their antitumor cytotoxicity induced by B-BiTE/Dar and B-BiTE/Elo was enhanced when compared with that mediated by Dar/Elo alone in vitro and in vivo. Importantly, human peripheral blood T cells and NK cells obtained from patients with myeloma cooperatively responded to their own myeloma cells in the presence of B-BiTE/mAb. Furthermore, in the presence of polyclonal immunoglobulin, B-BiTE/mAb activated T cells/NK cells for myeloma cells, but did not induce any reactivity to normal cells.
Conclusion
B-BiTE can be a new modality to easily generate stable, safe, and effective bispecific antibodies from clinically available mAbs. This modality can allow us to prepare a panel of next-generation antibodies which induce both T-cell and NK-cell responses, resulting in further advancement of immunotherapy for RRMM.
Keyword(s): Antibody, Bispecific, Immunotherapy, Myeloma