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Identifying a Quality Cell Line Development Candidate: A Step-By-Step Guide

The development of quality cell lines, especially for the production of therapeutic antibodies, is a critical step in the biopharmaceutical industry. Contract development and manufacturing organizations play a pivotal role in this process. CDMOs partner with drug makers to identify and ensure the development of high-quality and high-titer antibody-producing cell lines — cells that produce the desired antibody in a pure, effective form and in high quantities.

“Keeping commercialization in mind from the start of development generally means maintaining awareness of two important elements: titer and protein quality,” a veteran cell line development scientist at CDMO Samsung Biologics, wrote in a recent white paper.

“Supplemented by the appropriate considerations and relevant expertise, early testing helps biologics developers to plan, mitigate, and resolve open elements. Low titers, meanwhile, can significantly impact cost of goods sold (COGS) by driving up the amount of raw materials necessary to produce the desired product, as well as marring batch-to-batch consistency.”

While the technology used to design cells to produce antibodies has improved dramatically in recent years, there remain obstacles, and pharmaceutical companies both large and small are increasingly turning to CDMOs with the facilities and expertise to ensure the use of the most efficient, high-quality cell lines.

Each CDMO has its own nuanced approach to cell line development, but the goal is the same across the board: developing a quality cell line as soon as possible while avoiding the risks of encountering problems further along in the process. Here’s a step-by-step guide to how these companies approach cell line development.

Step 1: Host Cell Selection

Step one is the selection of the appropriate host cell. The choice of host cell impacts the quality and yield of the produced antibodies. Cells are evaluated for their growth characteristics, genetic stability, and productivity. Developers tend to use Chinese hamster ovary cells, which are both malleable, resilient, and similar enough to human cells to be suited for genetic alterations designed to produce human medications.

Samsung Biologics, for example, uses a proprietary S-CHOice® Chinese hamster ovary platform. The platform leverages a glutamine synthase knockout technology that’s been shown to produce titers reaching above 7 g/L for standard monoclonal antibodies, with enhanced viability of over 90% at day 21 in a fed-batch study.

GS knockout technology can enhance cell line development by simplifying the selection of high-producing cell lines. When the GS gene is eliminated, cells become dependent on external glutamine, ensuring that only those cells that successfully integrate and express both the GS and the gene of interest, in this case an antibody gene, can survive in glutamine-free media.

This process not only selects for cells with stable, long-term expression of the therapeutic protein, but can also increase productivity and improve protein quality due to the efficient selection process.

Step 2: Transfection

Once the host cell is chosen, it is genetically modified, typically through transfection, a laboratory method used to introduce foreign DNA or RNA into a cell. In the case of antibody production for biopharmaceuticals, transfection involves inserting a gene that encodes the desired antibody into the host cell’s DNA.

CDMOs ensure the use of efficient transfection methods and stable expression vectors, specialized tools that contain DNA sequences necessary to drive the production of proteins in cells. The goal is to maximize the likelihood of high-yield antibody production.

“Samsung Biologics performs transient transfection to look for the vector ratios,” read the whitepaper.

“Materials from transient transfection using several vector ratios are subjected to quality analysis. The necessary screening is reduced downstream because the quality of the molecule — the most vital factor in generating a viable bispecific [antibody] — has already been confirmed.”

Step 3: Screening for High Producers

Samsung Biologics deploys high-throughput screening in its cell line development process. This involves subjecting a large number of potential cell lines to simultaneous testing to identify those that best produce a therapeutic antibody.

HTS uses robotics, data processing software, and sensitive detectors to quickly assess the genetic makeup and productivity of thousands of cell variants. This is done to find the few cell lines most efficient at producing the target antibody.

The process is highly automated. Samples from each cell line are placed in wells on a plate, then various assays are performed to test for the presence and quantity of the desired antibody. Automation allows for the rapid processing of many samples, reducing the time and labor involved in traditional methods.

Step 4: Stability Testing and Scale-Up

The selected high-producing clones undergo extensive characterization to evaluate their genetic stability and productivity over time. This step is crucial to ensure that the cell line will maintain its productivity throughout the manufacturing process.

Scaling up the production from a lab scale to an industrial scale is the next critical step. A competitive CDMO like Samsung Biologics would leverage its various sizes of bioreactors from 200 to 15,000 liters to provide an optimal environment for cell growth and antibody production. During scale-up, parameters such as pH, temperature, nutrient supply, and oxygen levels are optimized to ensure maximum antibody yield and quality.

Step 5: Purification and Quality Assessment

The final step is the purification of the antibodies from the cell culture medium. This involves a series of chromatography steps to ensure the purity of the antibody. CDMOs conduct rigorous quality control tests to ensure the antibody meets all regulatory standards for purity, potency, and safety.

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