Impurity Precipitation Strategies for Intensification of mAb Downstream Processes

Next month, CBI will host its Downstream Disruptive Technologies conference in San Diego. This conference promises to highlight exciting new technologies for addressing key pain points in downstream bioprocessing. Platforms and strategies to de-risk innovation, accelerate technology adoption and increase operations efficiency will be discussed. We were fortunate to be able to interview one of the speakers, Anja Trapp, Scientist, Bio Process Science, Rentschler Biopharma SE about her talk, “Intensification of mAb downstream processes using impurity precipitation strategies”.

In her talk, Anja will discuss how:

  • Impurity precipitation can be performed in simple mixed systems followed by precipitate separation by depth filtration
  • Precipitation using caprylic acid provides host cell protein clearance comparable to column chromatography
  • Virus clearance studies show that caprylic acid provide complete inactivation of an enveloped virus contributing to the virus safety of the process

In the interview, we asked Anja if she could share more details about using impurity precipitation and the benefits. We have provided the text of our interview below:

Can you please describe impurity precipitation and how it can be used in downstream processing?

Impurity precipitation is focused on process- and product-related impurities which have to be removed during the downstream process in the manufacturing of therapeutic proteins. Common impurities are host cell proteins, DNA as well as aggregates of the therapeutic protein. Moreover, the purification process must include steps which are able to inactivate or remove viruses to ensure the viral safety of the biopharmaceutical.

The prospected precipitants used in impurity precipitation are molecules that interact selectively with the desired impurities, inducing conformational changes and leading to a precipitation. Caprylic acid is a short chain saturated fatty acid and was found to precipitate plasma proteins in the 1950s and since then it is widely used to isolate immunoglobulins from plasma. We take advantage of this mechanism in monoclonal antibody (mAb) purification to remove process- and product related impurities while leaving the antibody in solution.

What kind of processes is this technology a good fit for?

Especially the purification of mAbs is very suitable for caprylic acid-induced precipitation. The commonly applied low pH virus inactivation step enables a simple integration of a precipitation step. Firstly, it is performed in a stirred tank to ensure homogenization and on the other hand, the subsequent depth filtration step provides a high capacity for the removal of precipitates. Thus, it offers the opportunity to utilize existing tanks and process flows.

Besides the excellent removal of host cell proteins, we showed complete inactivation of enveloped viruses. Moreover, we evaluated the stability of different mAb molecules systematically to gain more insights. As mAbs are relatively basic and non hydrophobic proteins they are mostly less impacted by caprylic acid. Thus, caprylic acid-induced precipitation can be implemented as an excellent alternative to column chromatography to promote two-column downstream processes.

Is this approach scalable?

Regarding scalability of a precipitation step comparable parameters, important in process steps like low pH treatment as well, have to be considered. Mixing studies should provide the data to ensure comparable homogenization of the mixture in different scales. Furthermore, incubation times and hold time stabilities have to be checked in the development phase. As important as the precipitation step itself, the subsequent filtration has to be developed properly. Different depth filters are available on the market to enable a robust and cost-effective process step. Using this knowledge together with process relevant factors enables the design of an economic and intensified mAb purification platform.

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