Precipitation can be a highly effective step in the initial purification of monoclonal antibodies (mAb). High yield of the precipitates can be produced continuously in a tubular reactor using cross-linking and volume exclusion agents. A fully continuous precipitation process has been explored by integrating the precipitation step with hollow fiber microfiltration for dewatering and washing. The objective of this study was to investigate opportunities for increasing the performance of the membrane steps by increasing the critical flux/conversion and reducing the product loss due to re-dissolution of the antibody product. Experiments were performed using human serum Immunoglobulin G (IgG) as a model antibody with 0.2 µm pore size polyethersulfone membranes. IgG precipitates with &gt;99% yield were produced using combinations of zinc chloride and polyethylene glycol in a tubular precipitation reactor with residence time of approximately 30 s. Critical flux experiments were performed using a total recycle system, with the inlet feed flow rate and precipitate concentration varied to determine their effects on the critical flux. Washing experiments were performed using different IgG precipitate concentrations and wash buffer conditions. The overall conversion in the hollow fiber module could be increased by adding a recirculation loop to the membrane module, providing more effective dewatering and washing of the protein product. Model calculations predict that conversion greater than 90% can be achieved with feed IgG concentration of 2.5 g/L, which can provide more than 100-fold impurity (host cell protein, HCP) removal using a single stage wash or more than 900-fold impurity removal after a two-stage counter-current wash step. Pre-concentration of the IgG gave precipitates that were more resistant to product re-dissolution, leading to an increase in product yield. These results provide important insights into opportunities for improving the design and operation of a precipitation – microfiltration process for the initial capture / purification of monoclonal antibody products.

Performance characteristics of hollow fiber microfilters for purification of monoclonal antibodies by precipitation

ACS Fall 2020 Virtual Meeting

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