Maintaining the supply chain of single-source raw materials is of utmost importance for a biopharmaceutical company's manufacturing operations. As often happens, a supplier will notify its customer of process changes that might affect the quality or properties of supplied materials. Occasionally, a supplier might notify the customer of substitutions in its own supply chain or other changes in the source of its own raw materials. Customers must conduct appropriate testing using the “new” raw material(s) to ensure acceptable comparability, even if the change is only in sourcing and not the process itself.

Here we illustrate one such example in which a supply chain notification (SCN) described a source change in one of our supplier's cellulose-based ion-exchange chromatography media raw materials (cotton linter). Upon receipt of the SCN, chromatography tests were executed in the laboratory using a representative small-scale model of the affected manufacturing process using new and prechange media to test their comparability. Later, the new resin was used in packing studies with radial columns at large scale, and packing differences were observed when the results were compared with historical data. Since then, and with the supplier's support, significant efforts have been made to further understand the implications of this change in chromatography media and prevent negative impact on performance of the biopharmaceutical purification process.

PRODUCT FOCUS: BIOPHARMACEUTICALS

PROCESS FOCUS: DOWNSTREAM PROCESSING

WHO SHOULD READ: MANUFACTURING AND PROCESS DEVELOPMENT

KEYWORDS: CHROMATOGRAPHY, RESIN, VARIABILITY, COLUMN PACKING

LEVEL: INTERMEDIATE

Materials and Methods

Comparability Studies and Pressure Flow Profiles at Small Scale: To evaluate the impact of this change, small-scale (34-mL column bed volume) studies compared the chromatographic performance of new resin lots provided by the supplier against the prechange resin. During these experiments, we compared chromatographic profiles and column performance parameters of the media with two different linter sources. We also generated pressure-flow profiles at small scale to evaluate potential effects on the packing process of the ion-exchange chromatography column resulting from the change (1). For the small-scale experiments, we used XK axial-flow chromatography columns from GE Healthcare (www.gelifesciences.com).

For our comparability studies, we tested three different lots of resin with the new linter and compared the results against a control resin manufactured with the prechange linter. We ran each packed column with a corresponding control on a single ÄKTAexplorer small-scale chromatography system from GE Healthcare to reduce system-to-system variability.

We obtained pressure-flow profiles from columns using two lots of the new and one lot of the prechange linter resin. To monitor pressure differences, we tested six column packs from the new-linter resin and six from the prechange resin using the small-scale chromatography system. To obtain the specific pressure profile for each resin type, we recorded pressure readings at flow rates of 23, 57, 90, 124, 158, 192, and 226 cm/h for each packed column using equilibration buffer. Those flow rates covered the range of roughly zero to the maximum pressure rating for the columns. We subtracted the system pressure contributions by performing the same pressure-flow rate readings with a column filled only with equilibration buffer.

Packing Studies with Radial Columns at Large Scale: To determine whether changes in resin and scale could affect chromatographic pressure and flow dynamics, we performed the same ion-exchange chromatography step at large scale (20-L column bed volume) using a radial-flow column. In such columns, the mobile phase flows in a radial path from the outer column area into the center (Figure 1). Because our small-scale pressure-flow studies used axial-flow columns, it was important to test the packing of the new-linter resin at a larger scale to ensure that hardware differences did not produce dissimilar results from the small-scale studies (2). During execution of the large-scale test run, we packed the column with three new-linter resin lots. After the resin was properly conditioned, the column was packed at a set flow rate to a final target pressure (Figure 2). At this scale, the amount of resin packed is ≥11.3 kg.