Biopharmaceuticals from two different manufacturers cannot be identical, but only similar. Because of product and process complexity, biotechnological products cannot be shown to be equivalent. For this reason there can be no such thing as “biogenerics”, but only “biosimilars”.
Genetically modified cells and cell lines
In order to manufacture human proteins using biotechnological methods, the requisite human genes must first be inserted into appropriate host cells. Most commonly used for this purpose are the bacterium Escherichia coli and eukaryotic CHO (Chinese hamster ovary) cells.
Biotechnologists insert structural and control genes for the production of the desired active agent into cells of these and similar lines.
This creates a recombinant cell line that is a valuable asset to the manufacturer, since it is these cells that will actually produce the biopharmaceutical.
Technically, the process of reproducing these cells is highly challenging, especially when a therapeutic protein has to be produced in mammalian cells. Living cells react sensitively to even the slightest changes in their environment. Many factors and substances – from the nutrient solution to the design of the equipment – play a role. These factors determine not only the yield of active agent, but also the amount of interfering or unwanted by-products and even the structure of the active agent.
For this reason every biopharmaceutical production plant is unique: alteration of any one of the many components can influence the result – and in extreme cases necessitate a whole new marketing authorisation procedure.
Master cell bank
The genetically modified cells are reproduced and stored in a master cell bank at very low temperatures; if prolonged storage is required, cells can be kept almost indefinitely in liquid nitrogen at 196°C. It is from cell banks such as these that cells are taken for drug manufacture. This occurs via the following steps:
Cells are transferred from the deep-frozen cell bank to a liquid nutrient medium and then cultured. As it grows, the cell culture is transferred in a series of steps to larger culture vessels.
The actual production of active agent occurs during this phase. The culture media contain many different components for the manufacture of the desired protein. The precise composition of the medium has to be optimised for each production cell line. Steel containers for large-scale fermentation have a capacity of up to 10,000 litres, the size of the container being limited by factors that are not only technical, but also biological: the larger the fermenter, the more difficult it is to ensure essentially identical conditions for all cells.
Fermentation can be followed immediately by purification. In the simplest case the cultured cells release the product into the surrounding medium (secretion).
The cells are separated from the culture medium by a process of centrifugation or filtration. The molecules of active agent are then isolated from the culture medium via a series of purification steps. On the other hand, if the biosynthesised product is still inside the cells, these must first be lysed. The resulting cell debris and the many other cell components are then separated from the active substance in a multi-stage process.
In order to ensure constant quality, every batch of active substance is tested for purity and other important properties – 99.9% purity being required for marketing authorisation. Only then can the finished product be further processed and dispatched.
Pharmaceutical formulation and bottling
Even the final steps in biopharmaceutical production are challenging. The sensitive proteins have to be put into a stable pharmaceutical formulation and safely bottled, stored and administered. As therapeutic proteins are destroyed by gastric acid because of their sensitive structure and unable to pass through the intestinal wall because of the large size of their molecules, most biopharmaceuticals are administered by injection.
In terms of sales and production capacity, Roche is now the world’s largest biotech company.
The Roche Group operates the following biotechnological production facilities:
|Basel (Switzerland):||Active substances for Avastin and Roferon|
|Penzberg (Germany):||Active substances for Herceptin, NeoRecormon, Rapilysin, Pegasys and in future Mircera, plus enzymes and antibody reagents for diagnostic tests|
|Genentech:||Vacaville (US); Oceanside (US); Singapore (projected)|
|Chugai:||Utsunomiya and Ukima (both in Japan)|
Roche’s largest European biotechnology centre
Roche’s largest biotechnology centre – the Penzberg site in Bavaria – brings together R&D and production facilities for the Diagnostics and Pharmaceuticals Divisions. Enzymes, proteins, monoclonal antibodies and hormones for use in medicine and research are produced at this site, which also has significant mammalian cell culture and bacterial fermentation capacity.