While mammalian cell alternatives to CHO based biomanufacturing are making a case, CHO still remains the most common cell line for best selling biologics on the market today. In a previous blog “CHO Cells the Top Expression System of Best Selling Biologic Drugs,” we discussed the manufacturing cell lines used in the top five best selling biologics of 2010. In 2010, four out of the top five best selling biologics used CHO cells for manufacturing. In 2011, according to Huggett and Lähteenmäki (2012), the top ten best selling biologics were Humira, Enbrel, Rituxin, Remicade, Avastin, Herceptin, Neulasta, Lucentis, Avonex and Rebif. Of these, seven are manufactured using CHO cell lines.

CHO cell line manufacturing has come a long way since Genentech’s Activase, the first product produced in CHO cells (approved in 1987), but that technology was critical in laying the foundation for the kind of biologic manufacturing that exists today. Biomanufacturing has made continual improvements over the years, including advances in equipment, cell line development practices, and media formulation. These improvements have been important to CHO’s long-term success and have kept them as a top choice in manufacturing since the early 1990’s. How long will CHO cells remain the workhorse for the biopharmaceutical industry? With all the biomanufacturing improvements that have already been made, are further improvements possible to improve cost and reduce capital investment? Below are some thoughts on areas where gains can still be made to carry CHO cell line manufacturing into the future.

At the beginning of the bioproduction process, effective gene cloning and clone selection are critical in selecting a CHO cell line that will be a good fit for biomanufacturing. Cell lines must grow well, have high expression, and be stable over time. One technology that provides an alternative to traditional gene cloning is gene synthesis. Gene synthesis offers a way to quickly design and synthesize a gene sequence and that it is ultimately more cost effective than traditional cloning. In addition, gene synthesis provides sequences that are codon optimized for the host cell line, providing higher expression levels and easy protein purification.

Another area for improvement of antibody yield and cost is in adjusting the cell culture media to improve cell performance. Early products produced in CHO cells were cultured in media that almost always contained fetal bovine serum. Serum is undesirable in biomanufacturing because it is undefined and carries safety concerns involving the risk of viral and prion contamination. As a response to these concerns, in the early 1990’s there was a great deal of research being conducted around how to remove serum and other animal products from CHO manufacturing, but yield often suffered. Since then, serum free media has become the norm and now there are new animal-free, defined supplements including recombinant proteins and purified defined plant based hydrolysates that have been shown to improve cell growth, viability, and antibody yield further.

One area where some believe big improvements have been made is perfusion bioreactors. Perfusion bioreactors culture cells continuously, feeding and harvesting for much longer periods (sometimes months) compared with traditional bioreactors which culture cells in batches typically running between 7-21 days. Proponents of perfusion identify many advantages: (1) there is no accumulation of waste products, which is particularly important for proteins that are less stable;(2) because cells in perfusion are bound to a substrate, there is less movement with no mixing necessary. This produces antibodies that are more like the native form and are more consistent resulting in higher final product quality; and (3) perfusion bioreactors are more space friendly in that they can produce the same yield in much less tank space by culturing cells at much higher concentrations. It has been shown that a 50-liter perfusion bioreactor can produce the same yield as a 1,000-liter fed-batch bioreactor. Some have questioned the cost of perfusion bioreactors due to the amount of media used in a continuous system, but estimates show that in large-scale production they should be more cost effective due to a reduction in capital and operating costs. The industry has been a bit slow to warm to perfusion bioreactors, but if manufacturers of these systems are right, it could prove to be a big improvement.

These are just a few examples of work being done to improve cell culture and biomanufacturing, and there are many others. Please share your ideas.

Don’t miss the the latest versions of this information – “Biologics Still on Top in Best Selling Drugs of 2013” and “10 Biologics on Best Selling Drugs List for 2014.”