Conference Dates

November 1-5, 2015


Novel biopharmaceutical products, such as virus-like particles (VLPs) and viral vectors, constitute a challenging task for downstream processing (DSP). Recoveries achieved to reach required purities are significantly inferior compared to more common antibody and other recombinant processes. Therefore, the biopharmaceutical industry is looking for alternative downstream strategies capable of improving purification yields and decreasing cost while maintaining product quality. One of many possible improvements to DSP is to replace single-column batch operation by continuous, or semi-continuous, multi-column chromatography.

A single-column batch chromatographic operation used for capture is limited by the dynamic binding capacity (DBC) of the target product. For high-value products, chromatographic columns are normally loaded to less than 1% of DBC underutilizing the resin's capacity. Increasing capacity utilization leads to significant resin cost savings, particularly relevant in the case of capture with expensive affinity materials. Multi-column processes have been shown to improve process efficiency and economics, providing a powerful and flexible alternative to conventional batch chromatography. In fact, a simple serial connection of two chromatographic columns, where the effluent of the first column of the train is directed to the inlet of the second column, allows that in a loading step the breakthrough of the first column is captured on the second bed, thus avoiding product loss. After saturation, the first column can be subjected to the normal processing steps of a batch chromatographic operation while loading is resumed in the adjacent bed. Moreover, this simple setup modification allows not only to extend the utilization of the resin’s capacity, overcoming the aforementioned issues, but also to benefit from the counter-current flow between the mobile and the stationary phases, which optimizes the driving force for mass transfer throughout the overall trajectory of the two phases.

We report the development of a continuous chromatographic process for the purification of Hepatitis C VLPs (HCV-VLPs), produced using insect cell-based expression with recombinant baculovirus. A library of novel anion exchange resins with different ligand densities was evaluated for improved binding and release of the target product and impurity clearance in batch operation. A model-based approach for a smooth transition from a single-column batch process to a continuous multi-column operation is demonstrated and the scheduling of periodic events of the process cycle is analyzed. The contribution of column overloading, counter current operation and faster flow rates to recovery improvements compared to batch is discussed. Ultimately, both purification strategies, batch and continuous, are compared not only in terms of volumetric productivity, resin capacity utilization and footprint reduction, but also to indicate whether actual performance can be improved by continuous operation.