Purification Strategies to Process 5 g/L Titers of Monoclonal Antibodies - Altering the order of operations, using new resins, and increasing dynamic binding capacity can obviate the need for major fa
Once buffer tank volume constraints have been addressed, pool tank volumes can become the next significant bottleneck. Pool
tank constraints can arise during a given step through two mechanisms: a) the volume of the elution pool exceeds the tank
capacity, or b) the pH and/or conductivity adjustments to condition the pool in preparation for the next chromatography step
exceed the tank capacity. Increasing the resin DBC can address the first limitation, but the second limitation requires downstream
unit operations to be investigated. Depending on the elution conditions and the target conditions for the subsequent step,
a large volume of water may be necessary to lower the conductivity to the desired level for optimal antibody binding or impurity
removal.
Cation Exchange Process Optimization for Facility Fit (Process A)
Figure 3
When the cation exchange chromatography step is placed after the Protein A step, specific development considerations are needed
to ensure both acceptable process performance and pool tank fit at different facilities. In some of our facilities, the bottleneck
does not lie in the cation exchange pool tank itself, but rather in the pool tanks of the subsequent viral filtration and
anion exchange steps. The cation exchange elution phase must be optimized to remove host cell protein (HCP), leached Protein
A, and aggregates, while also minimizing pool volume and downstream pool conductivity. The anion exchange step functions to
clear HCP and often requires a low load conductivity for acceptable process performance. The available operating space is
often defined by a combination of factors affecting purity, product quality, product stability, yield, and manufacturing facility
fit, as shown in Figure 3 for a cation exchange process. In this example, facility fit sets the upper limit for salt concentration,
while both yield and purity are constrained by the interactive combination of elution buffer salt concentration and pH. One
approach for debottlenecking the plant fit is to decrease downstream pool conductivities by eluting the cation exchange step
at higher pH, thus lowering the salt concentration, assuming no negative impact on product quality at higher pH conditions.
