HIGH-LEVEL EXPRESSION OF THE HUMANIZED MONOCLONAL-ANTIBODY CAMPATH-1H IN CHINESE-HAMSTER OVARY CELLS

We have cloned the light and heavy chain cDNAs for the humanized monoclonal antibody Campath-1H and expressed them in Chinese hamster ovary (CHO) cells using a dihydrofolate reductase (dhfr) amplification procedure. Each cDNA was positioned under control of the strong human beta-actin promoter/polyadenylation signals and used to evaluate alternative vector design and amplification procedures. By employing a dual selection co-transfection strategy, initial transformants accumulated antibody levels of 0.5-mu-g/ml after 4 days continuous culture. When subjected to successive rounds of selection in medium containing stepwise increments in methotrexate (MTX), stable cell lines were obtained that secreted up to 200-mu-g/ml of Campath-1H during the same period. This reflects a productivity of 100-mu-g/10(6) cells/day and demonstrates the potential of engineering CHO cells for the production of recombinant antibodies.