Exploring Options for Optimizing Cell Line Development

Published on: 
Pharmaceutical Technology, Pharmaceutical Technology, September 2022, Volume 46, Issue 9
Pages: 28-29, 56

Biopharmaceutical manufacturers must consider a surprisingly wide range of factors when deciding where to turn for assistance with cell line development.

Biopharmaceuticals are revolutionizing the way the industry prevents and treats a broad spectrum of diseases. Therapeutic recombinant proteins, including monoclonal antibodies (mAbs), bispecifics, and biosimilar molecules, are among the most common biologics developed for therapeutic applications (1). Although versatile and powerful, the living organisms required for the production of therapeutic proteins can be more difficult to control and optimize in a manufacturing setting than chemical compounds.

First, a lead candidate is identified, and, once this happens, an appropriate production cell line is developed before upstream and downstream processes are established and optimized. Although under constant pressure, it is critical that biotherapeutic developers spend time and resources getting the cell line development process right. Without a robust production cell line that yields sufficient titers of a high-quality product, the facility will eventually reach a point where scalability becomes limiting, and commercialization is untenable. Cell line development also offers the opportunity to perform a number of physicochemical analyses and functional assays directly on the therapeutic protein, which will help improve the chances of clinical- and commercial-phase success.

Since cell line development is such a critical part of the drug development process, biomanufacturers should leverage a wide range of solutions to fill the gaps in their internal capacities and capabilities. It is possible to reap new benefits by partnering with experienced cell-line development vendors using optimized protein expression platforms that include the host Chinese hamster ovary (CHO) production cell line, optimized gene expression vectors, cell culture medium, and feed formulations. However, manufacturers may not realize the extent of their options when it comes to developing clonal production cell lines. This article discusses key factors to consider when planning how to accomplish this bioprocessing step.

Outsourcing cell-line development activities

To develop and maintain cell lines at scale throughout a product’s life cycle, manufacturers need to invest in a significant amount of expansion, including increasing facility footprint, equipment, instruments, and personnel hiring and training. Companies must determine whether they have the necessary skills, capacity, and resources to complete cell line development from start to finish or whether they need to outsource some, or all of, the process to save time and costs.

As part of this decision, biopharmaceutical developers also need to consider how many molecules they intend to have in production and carry out a cost/benefit analysis. For a large manufacturer planning to create a multi-product facility, it may be worthwhile to build in-house capabilities as a long-term investment. On the other hand, virtual, small, and mid-sized companies with one or more molecules in their pipeline may lack the necessary cell-line development expertise and internal resources and choose to outsource these activities to an experienced vendor. Nonetheless, some large biopharmaceutical companies still choose to outsource cell-line development requirements based on internal capacity and business objectives. Even after cell line development is complete, companies have the option to scale up and accomplish manufacturing with the help of a contract manufacturing organization (CMO) or other third parties.

Top priorities when selecting a cell line development partner

Success in the biopharmaceutical industry always involves achieving a balance between factors, such as speed, cost, technological advancement, and scale. Whether a developer is outsourcing just a few steps or the entire cell-line development process, it is essential to know which factors to weigh most heavily when comparing options for products and services.

Scientific expertise. Cell line development is a lengthy and complex multi-step process. To produce high-quality molecules on the most efficient timelines, the manufacturer or vendor that performs cell line development needs to gather a team with deep and broad scientific bioprocess expertise. Many stages along the path to produce a new production cell line often require subject matter expertise, including the final transfer step that will bring the cell lines from an external vendor to the intended manufacturing facilities.

Time to clinic is a central concern for all biopharmaceutical developers. To achieve production goals as quickly as possible, scientific operations teams must be intimately familiar with workflows that are both efficient and error-free. This often means avoiding the use of outdated, cumbersome processes (i.e., limited dilution cloning) and eliminating unnecessary stages, such as pool generation. Eliminating pool generation from the cell-line development workflow allows a much shorter timeline from DNA to research cell bank (RCB) generation, often by four to five weeks.

Manufacturers also need an analytical team capable of accurately characterizing the protein product during cell line development stages, particularly at the clone selection stage. Achieving high titers is pointless if the new production cell line produces a deficient molecule incapable of achieving its desired function or mechanism of action. Discovering that the molecule has a sub-par quality target product profile (QTPP) after the cell line has been developed is costly and will cause significant delays in getting the molecule to the clinic. To prevent these risks, the cell-line development operations team must measure certain key characteristics of the protein, beginning with functionality, in a biological assay or binding assay (depending on the protein’s mechanism of action) that determines purity, aggregation potential, product related impurities, and the protein’s likely glycosylation profile. The team must be familiar with high-resolution analytical methods using ultra-high-performance liquid chromatography (UHPLC), liquid chromatography-mass spectrometry (LC-MS), capillary electrophoresis, and other methods, all of which should be incorporated into the cell-line development workflow. With this knowledge, teams can select clones that produce a molecule that achieves the desired product quality attributes. Picking the right clones upfront removes the need to optimize the critical quality attributes post-cell line development.

Regulatory expertise. Because many biologics are relatively new modalities, regulatory agencies demand rigorous quality control. Deviations from biosafety standards can put developers at risk of denied regulatory applications or significant delays resulting from directives to generate new data, which can be laborious.


Scientific and regulatory expertise often overlap because regulatory requirements inform scientific workflows. For example, one dimension unique to biopharmaceutical manufacturing is a manufacturer’s ability to prove that a protein-based biologic was derived from a single clone. Strategies to demonstrate and assure monoclonality could include isolating single clones and capturing photographic images as the cells divides. Tracing the direct path from clone to the final product is essential to cell line development, along with rigorous quality control and risk management.

Four components for a successful cell line development project

Host cell line. Cell line development begins with choosing the right host cell line. Unsuitable cells can produce low titers or a low-quality product, ultimately causing delays and inefficiencies. CHO cell lines are most frequently used as hosts because they have an established, decades-long track record, are easy to grow in suspension at large scales (2000+ L), and possess the cellular machinery required to carry out appropriate post-translational modifications, which can be critical to the function and quality profile of the protein.

Biopharmaceutical developers should look for a vendor whose starting cell lines employ a metabolic selection system (2) rather than a system that involves toxic selection agents, such as methotrexate (MTX) and antibiotics. Such metabolic selection-based systems allow for improved robustness in cell growth and viability properties, reduced risk of genetic instability, and ability to enable high titer production.

Expression vector. After choosing the appropriate host cell line, a good vendor should provide an optimized expression vector capable of expressing high product titers after transfection. Developers need optimized expression vectors to ensure stable expression with minimal secondary effects on the otherwise optimized host cells. Ideally, a single expression vector should show utility for any type of molecule: mAbs, bispecifics, and biosimilars, among others.

Media. A cell line development partner should be able to provide cell culture media and feed that is highly compatible with the host cell line. A secure supply of that same media and feed supplements should be readily commercially available to purchase and use for any further process optimization and development and for good manufacturing practice (GMP) requirements. It is also important to consider the future availability of the cell culture media because assurance of supply is critical as production is scaled up.

Process design. The facility and operations must be configured to enable efficient and easy scale-up of the new production cell line. Streamlined process design involves implementing intelligent, scalable technologies and software to monitor, control, and analyze critical process parameters and product quality attributes. End-to-end solutions with integrated sensors and analytical software can reveal new process insights that can be used to gather information about host cell performance and optimize the cell line development process.

Flexibility and control

Living organisms, fluctuating supply chains, and shifting consumer markets all add variability to the production of biologics. As a result, maintaining flexibility is even more critical to biopharmaceutical experts than to manufacturers in other industries.

In-house manufacturing gives the highest amount of control and oversight for end-to-end bioprocesses, but some vendors offer options that allow for significant freedom while still providing technical assistance. For example, developers often have the flexibility to choose which CMO to work with for production after completing cell line development and optimization and further GMP cell banking (for master and working cell bank production). Some vendors also present multiple options for how each project can be accomplished, which adds transparency and gives developers more control over which strategies and technologies are applied.

Selected vendors also offer technology licensing options to create a middle ground between outsourcing and in-house processes. Through technology licensing, biopharmaceutical organizations can access expert-designed protocols, advanced technology platforms, and optimized materials from a vendor for use within their own facilities with their own team.

It is important to note that some vendors charge licensing fees or milestone payments for using their cell-line development technology. These fees are often based on the molecule’s success as it progresses through the various clinical phases. Other licensing agreements may include royalty fees in which the vendor receives a percentage of the molecule’s annual revenues. Biopharmaceutical developers should consider reliable vendors that operate on a simple fee-for-service model to maximize cost efficiency and retain complete control and ownership of their molecule.

Better cell lines for better therapies

Optimizing bioprocesses at every step, including cell line development, is key to delivering life-saving medicines to patients with maximum speed
and quality at an accessible cost. Biopharmaceutical companies should answer questions about their bioprocess development plans as early as possible, including how they will generate their new production cell lines, rather than devising sub-optimal strategies to solve problems that will undoubtedly arise as a result of poor planning. By dedicating time to taking stock of their own internal capabilities,
exploring options for outsourcing, and weighing the right priorities,
biopharmaceutical developers can give their therapeutic molecules the best chance of remaining viable through every phase of development process, manufacturing stages, regulatory approval, and commercialization.


1. R.M. Lu, et al., Journal of Biomedical Science 7, 1–30 (2020).

2. B. Tihanyi and L. Nyitray, Drug Discovery Today: Technologies 38, 25–34 (2020).

About the author

Jason Martin is regional product manager of Cell Line, Media & Testing Solutions at Sartorius.

Article details

Pharmaceutical Technology
Vol. 46, No. 9
September 2022
Pages: 28-29, 56


When referring to this article, please cite it as J. Martin, “Exploring Options for Optimizing Cell Line Development,” Pharmaceutical Technology 46 (9) 2022.