No abstract

Significant and continual improvements in upstream processing for biologics have resulted in challenges for downstream processing, both primary recovery and purification ( 1). Given the high cell densities achievable in both microbial and mammalian cell culture processes, primary recovery can be a significant bottleneck in both clinical and commercial manufacturing. The combination of increased product titer and low viability leads to significant relative increases in the levels of process impurities such as lipids, intracellular proteins and nucleic acid versus the product. In addition, cell culture media components such as soy and yeast hydrolysates have been widely applied to achieve the cell culture densities needed for higher titers ( 2, 3). Many of the process impurities can be negatively charged at harvest pH and can form colloids during the cell culture and harvest processes. The wide size distribution of these particles and the potential for additional particles to be generated by shear forces within a centrifuge may result in insufficient clarification to prevent fouling of subsequent filters. The other residual process impurities can lead to precipitation and increased turbidity during processing and even interference with the performance of the capturing chromatographic step. Primary recovery also poses significant challenges owing to the necessity to execute in an expedient manner to minimize both product degradation and bioburden concerns. Both microfiltration and centrifugation coupled with depth filtration have been employed successfully as primary recovery processing steps. Advances in the design and application of membrane technology for microfiltration and dead‐end filtration have contributed to significant improvements in process performance and integration, in some cases allowing for a combination of multiple unit operations in a given step. Although these advances have increased productivity and reliability, the net result is that optimization of primary recovery processes has become substantially more complicated. Ironically, the application of classical chemical engineering approaches to overcome issues in primary recovery and purification (e.g., turbidity and trace impurity removal) are just recently gaining attention ( 4). Some of these techniques (e.g., membrane cascades, pretreatment, precipitation, and the use of affinity tags) are now seen almost as disruptive technologies ( 5). This paper will review the current and potential future state of research on primary recovery, including relevant papers presented at the 234th American Chemical Society (ACS) National Meeting in Boston.

A sterically conservative, neutralizing mutation (glutamic acid to glutamine) in either of two different positions (15 or 48) of the soluble core tryptic fragment of cytochrome b5 results in two proteins with vastly different adsorption propenies. The kinetics of adsorption were measured under well-defined hydrodynamic conditions on a variety of different surfaces, of controlled electrostatic potential. prepared by modifying planar optical waveguides. Repeated measurement of the guided mode spectrum in the presence of protein solution allowed the temporal evolution of the number of adsorbed molecules to be determined. A highly positively charged surface acted as a perfect sink. Le.. adsorption was only limited by transport, adsorption to a highly negatively charged surface was fully reversible, and adsorption to a neuual phospholipid bilayer was very slow and practically irreversible. The macroscopic adsorption behavior can in large part be interpreted in terms of molecular-scale interactions between the protein and the adsorbent surface.

The emergence of monoclonal antibody (mAb) therapies has created a need for faster and more efficient bioprocess development strategies in order to meet timeline and material demands. In this work, a high-throughput process development (HTPD) strategy implementing several high-throughput chromatography purification techniques is described. Namely, batch incubations are used to scout feasible operating conditions, miniature columns are then used to determine separation of impurities, and, finally, a limited number of lab scale columns are tested to confirm the conditions identified using high-throughput techniques and to provide a path toward large scale processing. This multistep approach builds upon previous HTPD work by combining, in a unique sequential fashion, the flexibility and throughput of batch incubations with the increased separation characteristics for the packed bed format of miniature columns. Additionally, in order to assess the applicability of using miniature columns in this workflow, transport considerations were compared with traditional lab scale columns, and performances were mapped for the two techniques. The high-throughput strategy was utilized to determine optimal operating conditions with two different types of resins for a difficult separation of a mAb monomer from aggregates. Other more detailed prediction models are cited, but the intent of this work was to use high-throughput strategies as a general guide for scaling and assessing operating space rather than as a precise model to exactly predict performance.

Considerable resources are spent within the biopharmaceutical industry to perform viral clearance studies, which are conducted for widely used unit operations that are known to have robust and effective retrovirus clearance capability. The collaborative analysis from the members of the BioPhorum Development Group Viral Clearance Working Team considers two common virus reduction steps in biopharmaceutical processes: low-pH viral inactivation and viral filtration. Analysis included eight parameters for viral inactivation and nine for viral filtration. The extensive data set presented in this paper provides the industry with a reference point for establishing robust processes in addition to other protocols available in the literature (e.g., ASTM Std. E2888-12 for low-pH inactivation). In addition, it identifies points of weakness in the existing data set and instructs the design and interpretation of future studies. Included is an abundance of data that would have been difficult to generate individually but collectively will help support modular viral clearance claims.