Targeting CD19 for the Treatment of Autoimmune with a Novel T Cell Engager

Autoimmune disorder, affecting more than twenty million in United States and billions of people worldwide, occurs when human immune system mistakenly attacks its own body. Autoreactive B cells, particularly the autoantibodies they produce, play a critical role in the etiology, progress, prognosis and pathogenesis of multiple autoimmune diseases. While targeting B cells medicines, such as anti- CD19 or anti-CD20 monoclonal antibodies have produced reliable results in both pre-clinic models and some clinic practices, many patients failed to respond, ended less satisfactory outcome, or relapsed to monoclonal antibody therapies. Novel therapies are desperately needed to fight this challenge. In this study, based upon a symmetrical format, namely Fusion of IgG and scFv Technology (FIST), an anti-CD19xCD3 T Cell Engager (TCE) YK012, developed to treat B-cell malignancies such as precursor pre-B Acute Lymphatic Leukemia (ALL) and Non-Hodgkin’s Lymphoma (NHL), was expanded to search the treatment of autoimmune diseases by bringing T cells to CD19 positive B cells, including autoreactive B cell populations. Even as bivalent binding to CD3, YK012 has so significantly reduced binding affinity to T-Cell Receptor (TCR) compared to other TCEs that, free YK012 alone does activate T cells at all. In contrast, in the presence of CD19-expressing Raji target cells and mediated by YK012, T cells can be activated in a dosedependent manner, measured by upregulation of Nuclear Factor of Activated T cells (NFAT)-reporter, CD25, Interferongamma (IFN-γ) and granzyme B expression. Crosslinking of B cell with T cell by YK012, the conjugation elicited T cellmediated potent but mild cytotoxicity only to CD19-positive Raji cells. Additionally, YK012 elicited much reduced cytokines release in vitro compared to that of Blincyto® biosimilar, implying a potentially me-better therapeutics replacement in clinics for B-cell related diseases. In two in vivo pharmacological studies, YK012 alleviated the pathology symptoms of a collagen-induced arthritis model and almost completely depleted the peripheral B cell in human stem cell-transplanted murine model. Keywords Antibody; Bispecific antibody; T cell engager; Cancer; Autoimmune; CD19; CD3