Bicistornic Vectors + piggyBac = Improved Antibody Cell Line Production

To produce stable cell lines for monoclonal antibody production, manufacturers typically use the piggyBac transposon system. However, for larger, multi-specific antibodies with payloads of three or four cistrons, piggyBac alone is not sufficient. The challenges of multi-cistron vector architecture can lead to issues such as unbalanced ratios of heavy and light chains, chain mispairing, and genetic instability over time, which can slow cell line development and reduce titer productivity.

Scientists at Sanofi's Framingham, MA, site have developed a strategy to address these issues using a modified bicistronic vector system combined with the piggyBac transposon system. This approach has shown significant improvements in titer productivity, with one reported improvement up to six-fold. The modified bicistronic vectors incorporate altered promoter sequences, reporter placements, and cassette configurations to achieve better promoter configuration and cassette topology.

The use of a light-chain-selection marker heavy chain topology configuration has further enhanced pool productivity and reporter expression. The glutamine synthetase selection marker placed between the light and heavy chains improves expression balance and productivity. Under fed-batch conditions, the optimized system exhibited higher productivity, with the best clone producing 9.6 g/L.

This approach simplifies transfection workflows and provides enhanced control of gene expression and stability. The monoclonal and multi-specific antibodies produced using this optimized system are expected to be highly productive, stable, correctly assembled, and faster to develop compared to those produced using standard piggyBac technologies.