Production system establishment and in vitro study of CD19/CD3ε bite antibody secreted from Pichia pastoris

Blinatumomab is an anti-cancer Bispecific T-cell Engager (BiTE) antibody drug approved by the Food and Drug Administration (FDA) for treating acute lymphoblastic leukemia (ALL). It targets CD3ε, which is expressed on T cells and concomitantly targets CD19, an antigen specifically expressed in B-cell leukemia. Blinatumomab-bound T cells are activated to secrete perforin and granzyme, which induce cell death in B-cell leukemia. Blinatumomab is produced in the Chinese hamster ovary (CHO) cell expression system in consideration of post-translational modification (PTM) and immunogenicity. Although the characteristics of CHO cells are similar to those of other mammalian cells, it has low yield and high production cost. In this study, we developed the yeast species Pichia pastoris-produced BiTE antibody targeting CD19 and CD3ε, herein called P. pastoris (p)-blinatumomab, which is in-house produced blinatumomab. Approximately 1.2 mg/L CD19/CD3ε-targeting BiTE antibody (p-blinatumomab) was produced from the P. pastoris by transformation with the pHIL-S1 plasmid vector encoding the sequence of blinatumomab, which was 2.4 times higher than that produced in the CHO cell expression system based on the previous study. Enzyme-linked immunosorbent assay verified that the antigen binding affinity of the purified p-blinatumomab protein for CD19 and CD3ε antigens was 1.86 and 1.43 times higher than that of the commercial blinatumomab, BLINCYTO, respectively. In addition, flow cytometry confirmed that p-blinatumomab had a similar antigen binding affinity to CD19- and CD3ε-overexpressing cells compared to the BLINCYTO. In conclusion, we suggest that P. pastoris is a useful system for expressing and producing BiTE antibody platforms for therapeutic drugs.