Key Points• A novel CD33CD123DART agent induces T-cell-target-specific association, activation, and proliferation.• The CD33CD123 DART induces a dose-dependent killing of AML cell lines and primary AML blasts in vitro and in vivo.T-cell-directed killing of tumor cells using bispecific antibodies is a promising approach for the treatment of hematologic malignancies. Here we describe our preclinical work with a dual-affinity retargeting (DART) molecule generated from antibodies to CD3 and CD123, designed to redirect T cells against acute myeloid leukemia blasts. The CD33CD123 DART (also referred to as MGD006/S80880) consists of 2 independent polypeptides, each composed of the V H of 1 antibody in tandem with the V L of the other antibody. The target antigen CD123 (interleukin 3RA) is highly and differentially expressed in acute myeloid leukemia (AML) blasts compared with normal hematopoietic stem and progenitor cells.In this study we demonstrate that the CD33CD123 DART binds to both human CD3 and CD123 to mediate target-effector cell association, T-cell activation, proliferation, and receptor diversification. The CD33CD123 DART also induces a dose-dependent killing of AML cell lines and primary AML blasts in vitro and in vivo. These results provide the basis for testing the CD33CD123 DART in the treatment of patients with CD123 1 AML. (Blood.2016;127(1):122-131)

Many patients with acute myeloid leukemia (AML) will eventually develop refractory or relapsed disease. In the absence of standard therapy for this population, there is currently an urgent unmet need for novel therapeutic agents. Targeted therapy with small molecule inhibitors (SMIs) represents a new therapeutic intervention that has been successful for the treatment of multiple tumors (e.g., gastrointestinal stromal tumors, chronic myelogenous leukemia). Hence, there has been great interest in generating selective small molecule inhibitors targeting critical pathways of proliferation and survival in AML. This review highlights a selective group of intriguing therapeutic agents and their presumed targets in both preclinical models and in early human clinical trials.

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