A set of anti-apoptotic genes were over-expressed, either singly or in combination, in an effort to develop robust Chinese Hamster Ovary host cell lines suitable for manufacturing biotherapeutics. High-throughput screening of caspase 317 activity enabled a rapid selection of transfectants with reduced caspase activity relative to the host cell line. Transfectants with reduced caspase 317 activity were then tested for improved integrated viable cell count (IVCC), a function of peak viable cell density and longevity. The maximal level of improvement in IVCC could be achieved by over-expression of either single anti-apoptotic genes, e.g., Bcl-2 Delta (a mutated variant of Bcl-2) or Bcl-XL, or a combination of two or three antiapoptotic genes, e.g., E1B-19K, Aven, and XIAP Delta. These cell lines yielded higher transient antibody production and a greater number of stable clones with high antibody yields. In a 5 L fed-batch bioreactor system, B Delta 31-1, a stable clone expressing Bcl-2 Delta, had a product titer that was 180% as compared to an optimal clone (Con-1) from the control cell line. Although lactate accumulated to more than 5 g/L in the control culture, its concentration was reduced in the anti-apoptotic B Delta 31-1 cultures to below 1 g/L, confirming our earlier findings that cells over-expressing anti-apoptotic genes consume the lactate that would otherwise accumulate as a by-product in the culture medium. To the best of our knowledge, this is the first study to use the high throughput caspase screening method to identify CHO host cell lines with superior anti-apoptotic characteristics. (C) 2010 American Institute of Chemical Engineers Biotechnol. Prog., 26: 1367-1381, 2010