Identifying inhibitory threshold values of repressing metabolites in CHO cell culture using multivariate analysis methods.

Elevation of lactate, ammonia, osmolality, and carbon dioxide to inhibitory levels was reported to have adverse effects on cell growth and protein productivity in mammalian cell culture. Multivariate analysis methods were used to investigate the roles of these repressing metabolites in a fed-batch CHO cell culture for antibody fusion protein B1 (B1) production. Principal Factor Analysis methodology was applied to manufacturing-scale data of 112 cell culture runs, which identified threshold values of four repressing metabolites as follows: (1) ammonium levels above 5.1 mM inhibit cell growth; (2) both lactate and osmolality levels above 58 mM and 382 mOsm/kg affect cell viability; and (3) carbon dioxide levels at or above 111 mmHg reduce protein quality. These threshold values were then verified by simulations using Monod-type equations and Canonical Correlation. These results suggest that adverse effects on cell growth, productivity, and product quality may be minimized under the ideal cell culture condition, in which the peak values of all four repressing metabolites are maintained below the threshold values. This strategy was evaluated in 45 cell culture runs in 50-L bioreactors. Eight out of 45 runs were operated under the ideal condition, while the remaining 37 runs had at least one repressing metabolite with peak value at or above the threshold. In comparison to the remaining runs, the eight cell culture runs under the ideal condition had 17%, 40%, and 11% higher values in peak viable cell density, final B1 titer, and quality attribute, respectively. The unique methodology used in this study may be generally applicable in characterizing cell culture processes.