Genetic analyses of Per.C6 cell clones producing a therapeutic monoclonal antibody regarding productivity and long-term stability

ABSTRACT

Genetic characterization of proteinproducing clones represents additional value to cell line development. In the present study, ten Per.C6 clones producing a Rebmab100 monoclonal antibody were selected using two cloning methods: six clones originated from limiting dilution cloning and four by the automated colony picker ClonePix FL. A stability program was performed for 50 generations, including 4 batches distributed along the timeframe to determine specific productivity (Qp) maintenance. Four stable clones (two from limiting dilution and two from ClonePix FL) were further evaluated. The relative mRNA expression levels of both heavy chain (HC) and light chain (LC) genes were verified at generations 0, 3035, and 5055 of the stability program. At generations 0 and 3035, LC gene expression level was higher than HC gene, whereas at generation 5055, the opposite prevailed. A high correlation was observed between Qp and HC or LC mRNA expression level for all clones at each generation analyzed along the continuous culture. The mRNA stability study was performed at steadystate culture. The LC gene displayed a higher halflife and lower decay constant than HC gene, accounting for the higher observed expression level of LC mRNA in comparison to HC mRNA. Clone R6 was highlighted due its high Qp, mRNA expression levels, and mRNA stability. Besides the benefits of applying genetic characterization for the selection of stable and highproducing clones, the present study shows for the first time the correlation between Qp and HC or LC expression levels and also mRNA stability in clones derived from human cell line Per.C6(A (R))