Screening of bispecific antibodies during single cell cloning of recombinant Chinese hamster ovary cell lines to improve titer and product quality

Development of therapeutic bispecific antibodies (BsAbs) poses significant manufacturability challenges associated with correct chain pairing and an increased diversity of impurities. Here we address this with a product quality assessment during cell line development (CLD), forgoing the need for genetic characterization during cell line screening. Using Chinese Hamster Ovary (CHO) cell lines expressing a panel of monoclonal antibodies (mAb) and BsAbs, we demonstrate the highly specific binding of SpotLight™ Huλ, Huĸ and HuFc reagents to their target chain isotypes (lambda or kappa light chain and Fc regions) during single cell cloning workflows on a Bruker Beacon® Optofluidic System. We then demonstrate combinatorial use of SpotLight™ Huλ and Huĸ reagents as an early product quality indicator on a CHO cell line expressing a BsAb with dual kappa-lambda light chain configuration. Cell lines presenting equal binding profiles for each SpotLight assay exhibited platform-typical heterodimer levels with an average of 87.26% following fed-batch bioreactor production assessment. Conversely, cell lines biased towards either SpotLight™ assay resulted in lower than desired heterodimer (0%-84.23%) and increased associated impurities. This study demonstrates the application of dual SpotLight™ assays as an identifier of CHO cell lines expressing a kappa-lambda light chain BsAb with a high heterodimer percentage. This allows cell lines with optimal product quality to be identified earlier in CLD, resulting in fewer cell lines being progressed to resource-intensive fed-batch studies and subsequent product quality assessment. Furthermore, this assay provides an opportunity to characterize impurity expression biases prior to developing downstream purification processes.