Impact of Lot-to-Lot Variability of Cation Exchange Chromatography Resin on Process Performance

A case study to understand the impact of lot-to-lot variability of a cation exchange resin on process performance.
May 01, 2008


Cation exchange chromatography is commonly used as a polishing step in the purification of monoclonal antibodies. Cation exchange resins, however, typically have some lot-to-lot variability, which may result in a visually different elution profile, depending on the conditions used in the chromatography step. Product elution volumes also may be significantly different, depending on the product collection criteria. Despite this, there are no significant differences in the clearance of impurities. Differences in product volume, however, could lead to differences in the pH and conductivity of the product that could have an impact on the subsequent unit operation. This paper will present a case study that shows how the lot-to-lot variability of a cation exchange resin impacts its process performance and the performance of the subsequent process step. The study found that differences in product volume and elution profile were more prominent when resin lots containing larger percentages of smaller particles were used.

(Millipore Corporation)
In a typical antibody purification process (Figure 1), a cation exchange chromatography unit operation is used as a polishing step. Cation exchange is one of the three chromatography steps in the purification process.1 Protein A chromatography is the initial capture step. This is followed by a low pH hold step to inactivate viruses. Anion exchange chromatography, operated in flow-through mode, precedes the cation exchange (CEX) chromatography step. The purpose of this CEX step is to remove process- and product- related impurities such as aggregates, host cell proteins, and DNA. Downstream from cation exchange is the viral filtration step followed by ultrafiltration and diafiltration to concentrate and formulate the product.

Figure 1. Flowchart of an antibody purification process
This paper presents a case study that shows how the lot-to-lot variability of a cation exchange resin impacts its process performance and the performance of the subsequent process step. In the study, all initial cation exchange development runs performed using resin lot A consistently delivered small eluate volumes. Resin lots B, C, and D, however, produced much larger eluates, one of which was almost double the eluate volume from lot A. In a manufacturing setting, unexpected variability in elution volume could be costly if hold tanks are not big enough to accommodate large product volumes. The product may overflow the tanks and have to be diverted to waste. The installation of larger tanks to contain the extra volumes would be expensive in terms of both time and money.

In addition to large elution volumes, significant visual differences in shape of elution profile were observed. These differences included a flat portion followed by a trailing portion on the descending part of the peak, instead of a smooth and relatively rapid fall.

To determine the root cause of the unusually wide elution peaks, bench-scale cation exchange experiments were performed on four columns with unused resins. The first column was packed with lot A, the lot of resin that was used for all the initial cation exchange development work. The remaining three columns were packed with lots B, C, and D, respectively.


Some details relating to materials and methods could not be included because of confidentiality concerns.

Column Packing and Evaluation

Four 1.1-cm diameter Millipore Vanguard columns were each packed with a different lot of cation exchange resin to a height of 20±2 cm. Equilibration buffer was applied to each column. After the columns were equilibrated, approximately 0.25 mL (1.3% CV) M NaCl was injected. The conductivity of the column effluent was monitored. Column performance was evaluated by calculating the asymmetry and the height of a theoretical plate (HETP) from the NaCl chromatogram. Following this, the columns containing lots B, C, and D were also evaluated with a pulse acetone injection. The resulting signal was measured with UV at 280 nm.