Master and Working Cell Banks

Possible contamination by chemical or biological substances is one of the most important concerns when producing pharmaceutical proteins. Plant cell cultures ensure the production of the desired protein in a controlled, sterile and sealed environment and can be adapted to cGMP conditions. Therefore, the risk of contamination is minimized and the production conditions can be modified more easily in a contained reactor than in the field. Another advantage is the ability to freeze plant suspension cells in liquid nitrogen [66, 67] so that master and working cell banks can be established, a prerequisite for cGMP procedures [68]. 

To guarantee the availability of cells and the maintenance of their characteristics, a sufficiently large quantity of cells is kept in master and working cell banks, as discussed in Chapters 13 and 14. The number of cryotubes containing cells in a working cell bank is calculated to ensure that, for the whole expected lifespan of a product, each production lot will be obtained starting with cells from identical cryotubes. The most widely employed method for the conservation of cell banks is cryoconservation in liquid nitrogen at -196°C, which avoids mutations that could potentially alter cell characteristics. 

The ground rules for cellular characterization were set with human diploid cells and these particular substrates for vaccines are subject to guidelines developed by the WHO (1997). In turn, WHO guidelines have provided the parameters for characterization of heteroploid cells (WHO, 1987). It is therefore a natural progression that this level of characterization should also provide the basis for the characterization of master and working cell banks (see Chapter 1, section 1.3), even though this does present problems. 

As one of the most critical raw materials in production is the cell bank, defined acceptance/rejection criteria and parameters under which the bank will be used are required [55]. Assays are performed on master and working cell banks to demonstrate stability and freedom from adventitious agents. Cells are analyzed both from master/working bank vials as well as from the end of the production run or a few doublings later [55]. 

Cloning, cellbiology Non-GMP process development Master and working cell bank Pilot scale (partially GMP) Process development Preclinical studies (toxicology) Development of formulation Scale-up (fully GMP), validation Clinical studies (Phase I, ll/lll) Work out of the dossier EMEA centralized procedure Product launch... 

Biotechnology feniientation/ cell culture Establishment of master cell bank and working cell bank Maintenance of working cell bank Cell culture and/or fermentation Isolation and purification Physical processing, and packaging... 

Master Cell Bank and Working Cell Bank Origin... 

All containers of master or working cell banks and seed lots should be treated identically during storage. Once removed from storage, the containers should not be returned to the stock. 

CMC information It should contain sufficient detail to assure identification, quality, purity, and strength of the investigational drug. It should include stability data of duration appropriate to the length of the proposed study. FDA concerns to be addressed focus on products made with unknown or impure components, products with chemical structures known to be of likely high toxicity, products known to be chemically unstable, and products with an impurity profile indicative of a health hazard or insufficiently defined to assess potential health hazard, or poorly characterized master or working cell bank. 

Preparation and characterization of the clone master cell bank and working cell bank... 

Fig. 1.3 Diagram of a simple batch (or extended-batch) process with suspension cells. Cells are obtained from a Master- or Working Cell bank (MCB/WCB) and inoculated into spinners for a defined subcultivation period (every 3—4 days, usually for up to 100 days or more). For maintenance purposes of the culture, the cells in the spinner are referred to as the seed train". Cells...

Preclinical development comprises the technical and scientific elaboration of a process to manufacture the desired product on a large scale. Firstly, cell cultures and microorganisms to be used must be established as Master Cell Banks and Working Cell Banks, or as Master and Working Seeds, respectively. These ensure... 

The cell bank s construction design is normally two tiered, consisting of a master cell bank and a working cell bank (Figure 5.6). The master cell bank is constructed first, directly from a culture of the newly constructed production cell line. It can consist of several hundred individually stored ampoules. 

Master and working banks of both the viral vector and the animal cell line will have been constructed during the drug development process (see Chapter 4). Manufacture of a batch of vector, therefore, will be initiated by the culture of packing cells in suitable animal cell bioreactors. The... 

Figure 3.12. The master cell bank/working cell bank system. For simplicity each bank shown above contains only five ampoules. In reality, each bank would likely consist of several hundred ampoules. Working cell bank number 2 will be generated from master cell bank vial number 2 only when working cell bank number 1 is exhausted, and so on...

Production is based on a validated seed-lot system using a host-vector combination that has been shown to be suitable to the satisfaction of the competent authority. The seed-lot system uses a master cell bank and a working cell bank derived from the master seed lot of the host-vector combination. A detailed description of cultivation, extraction and purification steps and a definition of the production batch shall be established. 

In order to prevent the unwanted drift of properties which might ensue from repeated subcultures or multiple generations, the production of biological medicinal products obtained by microbial culture, cell culture or propagation in embryos and animals should be based on a system of master and working seed lots and/or cell banks. 

For vaccines the starting material problem was addressed early, and methods were developed to control the identity and purity of the starting material. These studies often were completed with the aid of, and in the laboratories of, scientists at CBER with the conditions mutually agreed upon at the time of approval. Specifically, the development of master cell bank (MCB) and manufacturers working cell bank (MWCB) concepts helped... 

Once the cell line is selected as a host for production, a cell bank system must be generated to guarantee the availability of an adequate source of equivalent cells to use through the product s lifetime in the market. Usually, the cell bank system consists of two levels a master cell bank (MCB) and a manufacturer s working cell bank (WCB). 

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