Process economics of animal cell and bacterial fermentations: a case study analysis of tissue plasminogen activator

One link in the complex chain of medical economics is the cost of bringing new drugs and biologicals to the market. Advances in recombinant-DNA technology permit production of therapeutically active proteins in effectively unlimited quantities. Nevertheless, each expression system has a characteristic influence on the nature of the product produced and the process required to obtain it. In this case study we compare experiences with recombinant-tissue plasminogen activator (rtPA) produced in Chinese hamster ovary (CHO) cells and in Escherichia coli, with the aim of understanding the roles of some of the parameters that affect process economics. tPA belongs to the group of highly specific serine proteases that convert plasminogen to plasmin, which in turn degrades several protein substrates including fibrin, thus making it an effective thrombolytic agent. The treatment of acute myocardial infarction with such thrombolytic agents can result in early discharge of patients and decreased medical costs. However, there are major differences in the prices of the various available agents. The price of the FDA-licensed tPA product is $2,200 per dose or $22,000 per gram. It is believed that a significant portion of this price relates to manufacturing costs. We examine by way of case study illustration the cost breakdown for the two processes, and highlight important process, design and economic considerations that ultimately define a particular protein product.