Antibody-membrane switch (AMS) technology for facile cell line development

Generation of high-productivity cell lines remains a major bottleneck in therapeutic antibody development. Conven-tional cell line development often depends on gene ampli-fication methodologies using dihydrofolate reductase or glutamine synthetase. Higher productivity is associated with an increased gene copy number. However, lack of selection pressure under the conditions of large-scale manufacturing leads to clonal instability. We have devel-oped a novel method for cell line development, antibody-membrane switch (AMS) technology, that does not rely on gene amplification. This fluorescence-activated cell sorting (FACS)-based, high-throughput method is facilitated by cell-surface antibody expression to rapidly and efficiently isolate high-producing cells. The switch between mem-brane expression and secretion is achieved by alternative splicing and specific DNA recombination. The antibody of interest is initially displayed on the cell surface to facilitate FACS. Isolated high-producing cells are then seamlessly transformed into production cells after removing the mem-brane-anchoring domain sequence with a DNA recombin-ase. AMS technology has been applied in a number of antibody cell line development projects, which typically last 2–3 months. The top production cell lines exhibit very high specific productivity of 40–60 pg/cell/day resulting in production titers of 2–4 g/l in 10-day batch culture