Bispecific Antibodies Enable Synthetic Agonistic Receptor-Transduced T Cells for Tumor Immunotherapy.

PURPOSE: Genetically engineered T cells are powerful anticancer treatments but are limited by safety and specificity issues. We herein describe an MHC-unrestricted modular platform combining autologous T cells, transduced with a targetable synthetic agonistic receptor (SAR), with bispecific antibodies (BiAb) that specifically recruit and activate T cells for tumor killing. EXPERIMENTAL DESIGN: BiAbs of different formats were generated by recombinant expression. T cells were retrovirally transduced with SARs. T-cell activation, proliferation, differentiation, and T-cell-induced lysis were characterized in three murine and human tumor models in vitro and in vivo. RESULTS: Murine T cells transduced with SAR composed of an extracellular domain EGFRvIII fused to CD28 and CD3ζ signaling domains could be specifically recruited toward murine tumor cells expressing EpCAM by anti-EGFRvIII × anti-EpCAM BiAb. BiAb induced selective antigen-dependent activation, proliferation of SAR T cells, and redirected tumor cell lysis. Selectivity was dependent on the monovalency of the antibody for EGFRvIII. We identified FAS ligand as a major mediator of killing utilized by the T cells. Similarly, human SAR T cells could be specifically redirected toward mesothelin-expressing human pancreatic cancer cells. In vivo, treatment with SAR T cells and BiAb mediated antitumoral activity in three human pancreatic cancer cell xenograft models. Importantly, SAR activity, unlike CAR activity, was reversible in vitro and in vivo. CONCLUSIONS: We describe a novel ACT platform with antitumor activity in murine and human tumor models with a distinct mode of action that combines adoptive T-cell therapy with bispecific antibodies.

Target Expression, Generation, Preclinical Activity, and Pharmacokinetics of the BCMA-T Cell Bispecific Antibody EM801 for Multiple Myeloma Treatment.

We identified B cell maturation antigen (BCMA) as a potential therapeutic target in 778 newly diagnosed and relapsed myeloma patients. We constructed an IgG-based BCMA-T cell bispecific antibody (EM801) and showed that it increased CD3+ T cell/myeloma cell crosslinking, followed by CD4+/CD8+ T cell activation, and secretion of interferon-γ, granzyme B, and perforin. This effect is CD4 and CD8 T cell mediated. EM801 induced, at nanomolar concentrations, myeloma cell death by autologous T cells in 34 of 43 bone marrow aspirates, including those from high-risk patients and patients after multiple lines of treatment, tumor regression in six of nine mice in a myeloma xenograft model, and depletion of BCMA+ cells in cynomolgus monkeys. Pharmacokinetics and pharmacodynamics indicate weekly intravenous/subcutaneous administration.