The fine line between antibody yield and process throughput

The latest research, published as an early view article in the journal Biotechnology Progress​​, describes a computer simulation that aims to aid researchers optimise the operating conditions used for purifying polyclonal antibodies on industrial scale column chromatography systems. The researchers from University College London, UK and biopharmaceutical company Protherics UK developed the model to help bioprocess engineers determine the optimum balance between yield and column throughput during polyclonal antibody purification. One of the major hurdles in designing the production process is maximising the efficiency of the purification process which often use very expensive custom-made affinity matrices to isolate the product specific IgGs (immunoglobulin Gs) from the remainder of the antibody repertoire. Because they are effective against several epitopes of a pathogenic antigen polyclonal antibodies are often preferred to monoclonal antibodies as a treatment for acute infections. One such example are therapeutic antibodies that treat rattlesnake bites, such as Protherics' CroFab. The US market for rattlesnake antivenins is as large as $80m a year. One of the major hurdles in designing the production process is maximising the efficiency of the purification process which often use very expensive custom-made affinity matrices to isolate the product specific IgGs (immunoglobulin Gs) from the remainder of the antibody repertoire. Many of the factors that affect the efficiency of the purification process, including loading range, flow rate and matrix capacity loss during repeated cycles were incorporated into the decision-support software. The researchers write that: "the values of these variables must be chosen carefully so as to achieve yields and throughputs that will satisfy market demand and ensure a financially viable process." ​ The data needed to populate the simulation was generated on scaled-down mimics of the industrial scale processes and was illustrated by application to Protherics' DigiFab, a biotherapeutic used to treat digoxin toxicity. The researchers found that the yield decreases as the flow rate through the column is increased, however, they caution that: "although reducing the flow rate will increase product yield, this may come at the expense of extended processing time and so a lower throughput." ​ An optimal balance of these two factors results in a trade off of both yield and throughput; if both are weighted equally the most favourable conditions were found to occur at a load concentration of 347 mg/ml and a flow rate 70 per cent lower than the base case.