Characterization of anti-CD79b/CD3 bispecific antibody, a potential therapy for B cell malignancies

High rates of relapse and poor prognosis confer an urgent need for novel therapeutic agents for B cell non-Hodgkin lymphomas (B-NHLs). Herein, we describe a human IgG-like anti-CD79b/CD3 bispecific antibody (IBI38D9-L) that selectively depletes antigen-positive malignant B cells as an alternative treatment option for relapsed or refractory NHL patients. The antitumor activity and mechanism of action of IBI38D9-L were investigated in vitro using B-NHL cell lines and human primary effector cells and in vivo using xenograft models reconstituted with human PBMCs (peripheral blood mononuclear cells). Pharmacokinetic (PK) properties and preclinical toxicology were evaluated in cynomolgus monkeys and HSC-NPG mice. IBI38D9-L exerted potent B cell killing as well as T cell activation and proliferation in a tumor cell-dependent manner in vitro and was active against B-NHL cell lines with various CD79b expression levels. Subcutaneous xenograft tumors in NOG mice engrafted with human PBMCs were eradicated by IBI38D9-L treatment. Moreover, IBI38D9-L-treated mice showed a strong infiltration of activated T cells. In HSC-NPG mice, IBI38D9-L resulted in potent B cell depletion in peripheral blood and induced only slight body weight loss and cytokine release syndrome without significant toxicological findings. In cynomolgus monkeys, IBI38D9-L was well tolerated with good pharmacokinetic profiles. Collectively, these preclinical efficacy and safety data provide strong scientific rationales for using anti-CD79b/CD3 bispecific antibody as a promising therapeutic agent for B cell malignancies.