The Age of Downstream Processing

The Asilomar conference of 1975 has been called the "Woodstock of molecular biology"³⁴ and has served as a questioning reminder of the power of recombinant DNA technology. The conference triggered the first guidelines for research on rDNA³⁵ and marked the beginning of biopharmaceutical regulation in the United States and elsewhere. From 1980 to 1994, 29 new biologic entities (NBEs), including 10 new recombinant entities, were approved, with an average time of 61 months from investigational new drug (IND) to licensure, 38.9 months shorter than for NCEs during the same 15 year period.³⁶ This was the era of molecular biology. Transiently, chromatography became a tool to expedite analysis and product purification of what could be termed "new age" biologics. However, a new discipline of downstream processing was minted, and now biopharmaceutical manufacturing divided into upstream (bacterial and yeast fermentation or mammalian cell culture) and downstream.

In contrast to the early years, new biopharmaceutical approvals currently run at about 40 per year in the US. The Biotechnology Industry Organization cites 254 drugs approved for 385 indications from 1982 to 2005.³⁷ In 2006, CDER approved only four new biological products and CBER approved nine new biological products. The number of products entering clinical trials also has tapered off since 1980. Clinical and approval phase lengths vary widely, with a trend to longer clinical phases. In 2003, the Tufts Center for the Study of Drug Development conservatively projected that more than 30 new biotherapeutics would be successful in the next six to seven years.³⁸

Biopharmaceutical products are subject to downstream processes that are built on process chromatography as the main purification agent and with membrane technologies providing clean feed streams, buffer exchange, product concentration, virus removal, and sterile filtration. As Jungbauer notes: "Bioseparation processes are dominated by chromatographic steps. Even primary recovery is sometimes accomplished by chromatographic separation, using a fluidized bed instead of a fixed bed."²⁷ The expansion of chromatography as the prime tool of downstream processing is manifest in the increase of bioprocess revenues at GE Healthcare's Life Science Division from approximately $36 million in 1986⁴¹ to $461 million in 2006.⁴²

Modernization of Process Chromatography

With the development of bacterial fermentation and mammalian cell culture as the sources for new recombinant products came a standardization of raw feed stocks with manufacturers sharing the same types of problems. The reduction of endotoxin levels from E. coli fermentation or the reduction of host cell proteins and DNA from CHO cell culture products are prime examples. This standardization allowed a more systematic approach to process development and is the underlying reason for the introduction of the capture–purify–polish paradigm, now ubiquitous in downstream process design. Industry developed a new, systematic approach integrating process design, engineering and control, process economics, hygiene, and regulatory issues, summarized by Sofer and Nyström⁴³ in 1989 and followed by a text on validation⁴⁴ in 1991. Bioprocessing systems were introduced and computerized control took over from technologies that were previously dominated by manual operation and therefore subject to operator error.

Focus on Viral Clearance

The transmission to hemophiliacs of HIV by human plasma-derived Factor VIII renewed the focus on viral clearance and methods of virus kill in the plasma fractionation industry. In the recombinant industry, cell cultures need to be protected from adventitious viral contamination by viruses such as virus of mouse (MVM), epizootic hemorrhagic disease virus (EHDV), and reovirus,⁴⁵ which may influence expression of the product by the host machinery. This need led to efforts to eliminate animal-derived raw materials from the process chain and thus improved safety.