An efficient and robust strategy for developing cell lines through targeted integration

Reducing the time needed and enhancing predictability of outcomes for cell line development is an ongoing focus of improvement. Targeted integration (TI) where the expression cassettes for a biologic are inserted at a predefined locus, a landing pad, is one of the strategies that is used for this purpose. To be commercially viable the landing pad host cell must support high titers and the transgenes in the landing pad must be highly transcribed. To make such a host TI cell line takes a great deal of time and effort with little guarantee of success. Here we describe a strategy where we converted a stable high-expressing mAb cell line and generated multiple TI host cell lines that are commercially relevant. We routinely generate 6 g/L mAb clones using our platform fit process and 8 to >10 g/L with process optimization that are phenotypically and genetically stable. We also created a duo-landing pad where both landing pads reside in the same locus. This gives the opportunity to simplify the construction of differentially expressed genes since both landing pads are expected to perform equally.