To help ensure maximum safety of biopharmaceuticals, several guidelines define international standards. Cell culture processes used in the preparation of biotherapeutics are subject to stringent requirements from official national and international regulatory bodies including the FDA, EMEA, World Health Organization (WHO), and International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). The practice of documenting procedures, cultures, and reagents used is important for promoting high-quality scientific work and was established to apply to cell substrates used in biotherapeutics manufacturing. Such documentation also provides traceability. Not only do you need to document the qualification of cell banks, it is also important to establish the stability of critical culture characteristics upon passage to ensure reliable performance of cells derived from the cell banks.Special Considerations for Continuous Cell Lines
Regulatory standards for characterization of master and working cell banks prepared from engineered cells that express a desired biotherapeutic product are provided in the following documents:
FDA's 21 CFR Part 610.18 (2)
FDA's 1993 Points to Consider in the Characterization of Cell Lines Used to Produce Biologicals (3)
ICH Q7A (4)
ICH Q5D (5).
Regarding quality standards for parental cell lines, section 2.1.3 of ICH Q5D makes the following suggestion:
A crucial step is the choice of a suitable parental cell line. For recombinant products, a parental cell line is typically the untransfected recipient cell line. The use of characterized parental cell banks is suggested, but is not considered essential. A characterized parental cell bank may be of benefit, especially when multiple cell substrates are generated from the same parental cell type, by providing a set of information on which the quality assessment of the Master Cell Bank (MCB) can be based. (5)
Although parental cell lines are not the main focus of that guidance, the regulation suggests that some supporting documentation is necessary to adequately describe the history of the cell line. The level of detail required to satisfy a regulatory agency regarding the development of a parental cell line remains a matter of interpretation. In general, the lineage of a parental cell line should include a description of the cell source, the results of tests for pathogenic agents, the cultivation history of the cells, and a history of any genetic manipulation or selection of the cell line. Table 1 lists studies recommended to fully document a parental cell line.Table 1: Example of master cell bank (MCB) and working cell bank (WCB) characterization according to FDA and EMEA, testing requirements
Considerations for Parental Cell Banks
Current good manufacturing practice (CGMP) refers to regulations that require manufacturers of drugs, medical devices, blood products, and some foods to take proactive steps to ensure that their products are safe, pure, and effective. The word “current” is there to remind manufacturers that they must use up-to-date technologies and systems to comply with these regulations. Systems and equipment that 20 years ago were “state of the art” for preventing contamination and errors may be less than adequate by today's standards.
Regulatory environments are ever-changing; standards are subject to continual revision and vary by country. Commercially available cells are increasingly accompanied by documentation aligned with CGMP requirements for production cell lines, and documentation requirements for parental cell lines may become more stringent. Creating parental cell banks under GMP guidelines requires a significant time investment. You must establish a reliable source of cells and document their history, test results, storage conditions, and chain of custody.
When you obtain CGMP-produced parental cells from an outside source, the ability to incorporate accompanying documentation into your company's specific regulatory submission paperwork is a distinct advantage.Producing Parental Cell Banks
Creation from Research Laboratory Stocks: All too often, lineage documentation of parental cell lines that originate in traditional research and development laboratories is either limited or nonexistent. Because of that lack of documentation, manufacturers using such cell lines have been required to essentially “restart the clock” on the cell line's history. In extreme cases, they may need to select a new clone or adapt their cell line to a new growth medium along with other associated characterization studies. Such activities can be expensive and time consuming, but regulations are clear about the requirement to establish a “clean bill of health” for each parental cell line.
Commercial Parental Cell Lines: Most cell lines available today require costly licenses. These can provide a viable option for some users. Even though licensing costs are often greater than the cost of creating cell banks from research laboratory material, the use of commercially available lines can significantly shorten timelines for developing production cell lines, which may make them more cost-effective.
Parental Cell Lines with Reduced Licensing Burden: One major hurdle in isolating stable, inducible, or constitutive high-level production cell lines is the time-consuming selection process. Given the variation in expression levels of the same construct in individual clones, you may often have to isolate and test hundreds of clones to identify one or more with the characteristics you want. That has led some cell line producers to begin offering cell line development kits. Such kits provide not only CGMP parental cells, but also the components and protocols needed to engineer and select producing clones in a completely serum-free system.
These kits enable biotherapeutics developers to create stable cell lines that express proteins of therapeutic interest. The integrated kit can help reduce the time for development and streamline regulatory documentation — in turn speeding up time to market. For example, Invitrogen offers the GIBCO OptiCHO protein express kit, a Chinese Hamster Ovary (CHO) cell line development kit that includes parental DG44 cells banked under CGMP guidelines and tested to FDA and EMEA requirements. Other examples of cell kits for in house development are those sold for CHO-K1 by Lonza and PER.C6 by Crucell.
With most commercially sold parental cell lines, licensing involves fees for research use in addition to commercial milestones and royalty payments. The level of fees and payments can vary greatly from vendor to vendor based on he level of imbedded technology within the kits and the supplier's business model. Regardless of the differences in fee structures, the level of documentation for the parental line should be consistent with industry best practices to assure quality of the cell substrate.A Potential Solution
As regulatory requirements for biotherapeutics become more stringent, increased reporting standards can be expected from different regulatory agencies throughout the world. Documentation requirements may become more critical for parental cells. Companies must consider licensing and royalty burdens in the total cost of a given parental cell line development option.
Cell line development kits could provide an attractive solution for cash-strapped biotech start-ups and pharmaceutical companies. In addition to cost savings (on licenses, royalties, documentation, and regulatory activities), a kit could also reduce productivity problems and downstream difficulties. This type of platform can provide efficient and cost-effective, stable cell line development with associated CGMP documentation. That in turn could lead to streamlined regulatory filings and thus more rapid commercialization of novel biotherapeutics.