Sanofi researchers reported a vector engineering strategy designed to improve stable cell line production for multicistronic monoclonal antibodies using piggyBac transposon technology. The approach targets upstream bottlenecks that can arise from complex vector architectures, including heavy/light chain mispairing and genetic instability that can reduce productivity. The group reported that a coordinated transgene expression design—combining modified bicistronic vectors with piggyBac—improved titer productivity up to six-fold under fed-batch conditions. Specific configurations with a glutamine synthetase selection marker were associated with improved RNA transcript balance for light and heavy chains. The work is an example of how manufacturing innovation is increasingly focused on genetic cassette design to stabilize productivity for larger multi-specific antibody formats.