Modern biologics manufacturing has trended simultaneously towards the use of high density cell culture production and single-use technologies. While this approach often yields high titers and simplifies manufacturing, primary recovery can be severely strained by turbid feed streams and facility limitations as single-use facilities typically do not have centrifuges. In this work, we present the development and scale-up of the cell culture harvest step in a challenging late-stage commercial process. The feed contained over nine percent solids and would foul most depth filters after loading only 50 liters per square meter of filter area. When increasing the harvest footprint was not an option at large-scale, an alternative depth filtration scheme was developed using a scale-down approach. A variety of depth filters were screened at small-scale for high capacity before fouling and turbidity breakthrough. The Millipore Clarisolve 20MS large pore depth filter showed a significant improvement in capacity over the other filters and was taken forward into development. Filter robustness was evaluated using material from batches of varying cell size distributions, peak densities, and viabilities. Pressure and breakthrough trends were consistent between runs. However, a chief concern was the high turbidity of the Clarisolve filtrate, especially from low viability batches. To improve harvest robustness and ensure reasonable 0.2 micron sterile filter area downstream of Clarisolve, secondary depth filters were screened for maximum loading and turbidity reduction. The final two-stage depth filter configuration was scaled up to 500 and 2000 liter scales, conserving performance and meeting manufacturing facility constraints. As biologics production processes continue to run at higher and higher cell densities, we anticipate challenges to established harvest steps. At the onset of filtration challenges, standard pore constriction decay models can also be leveraged with small-scale data to predict fouling behavior of turbid feed streams and performance of new filters.

Dirty harvest: overcoming high cell density depth filtration challenges using a scale-down sizing approach

2019 Spring National Meeting

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