Quantification of bispecific antibody-mediated T-cell activation with engineered CD3 effector and tailored CD19+ target cells

Mayer U, Frier Bovin L, Rodo J, Gobbo E, Ferrando-Miguel R, Lallemand C Svar Life Science AB, Malmö Sweden Bi- and multi-specific modalities, with their numerous formats, are advancing cancer immunotherapy, particularly in hematologic malignancies. Created from components like immunoglobulin half molecules, Fab fragments, or single chain Fvs, they can recruit and activate immune cells or interfere with receptor signalling. Hundreds of such antibodies are in clinical development, demonstrating various modes of action. Blinatumomab, a Bispecific T-cell Engager (BiTE) molecule, targets CD3 and CD19 for Tcell mediated elimination of B-cell malignancies. CD19 is an attractive target because early B-cell malignancies arise from CD20-negative Pro-B and Pre-B cells, unlike Rituximab, which targets CD20. Consequently, blinatumomab was approved for aggressive B-cell precursor acute lymphoblastic leukemias (ALLs), often affecting children. This success has spurred development of other bispecific molecules for hematologic malignancies, with over two-thirds targeting CD19 and CD20 and a mojority targeting CD3 on the effector side. Current analytical methods for T-cell activation have limitations, but our improved bioassay platform using CD3xCD19 offers a more reliable assessment. This approach involves effector T-cells carrying a reporter gene downstream of the CD3 signalling cascade and engineered target cells as antigenpositive or -negative controls. On this poster we showcase the performance of this reporter assay system in the context of Blinatumomab.