Mammalian Manufacturing of Biologics

Monoclonal antibodies (mAbs) recognize and bind to specific targets such as antigens on the surface of human cells. Some of the main applications of monoclonal antibodies are:

1. 1. Cancer therapy: monoclonal antibodies can be used to treat cancer by targeting specific antigens on cancer cells, which can help kill the cancer cells or prevent their growth.
   2. Autoimmune diseases: monoclonal antibodies can be used to treat autoimmune diseases, such as rheumatoid arthritis, by targeting specific proteins that contribute to the disease.
   3. Infectious diseases: monoclonal antibodies can be used to treat infectious diseases, such as COVID-19, by targeting the virus or other pathogens
   4. Diagnostics: monoclonal antibodies can be used in diagnostic tests to detect specific proteins or other molecules in blood or other body fluids.

Discover more applications of recombinant monoclonal antibodies in our dedicated blog post: What are monoclonal antibodies and their therapeutic applications?

From a medical point of view, some of the main benefits of developing mAb-based therapies are:

1. 1. Specificity: Monoclonal antibodies are highly specific and can be designed to target a particular antigen or cell type, making them useful in many applications.
   2. Low toxicity: Monoclonal antibodies are generally well-tolerated and have a low risk of side effects compared to traditional chemotherapies.
   3. Long half-life: Monoclonal antibodies have a longer half-life (from few days to several weeks) in the body than traditional drugs, which can reduce the frequency of dosing and improve patient compliance.

Recombinant antibodies are generated in vitro using an expression host (a cell used as a factory) that can yield high quantities. Mammalian systems, particularly Chinese Hamster Ovary (CHO) or human embryonic kidney (HEK) cell lines, are often preferred for producing antibodies. Monoclonal antibodies can be expressed either transiently or stably bythe host cells.

Transient production is useful to obtain small amounts of antibody within short timelines. When large amounts are needed or when a therapeutic application is considered, a stable cell line is developed to ensure reproducible and GMP compliant production of the antibody.

Simply said, the industrial production of recombinant antibodies involves cloning antibody-encoding genes into high-expression vectors, transfecting cells, selecting highly productive and stable clones, and scaling up antibody production.

Transient and stable expression are two methods for producing recombinant proteins, including monoclonal antibodies, using mammalian cell lines as expression systems.

• • Transient expression refers to a short-term process where plasmid DNA containing the gene of interest is introduced into the cells, and the protein is expressed for a limited period, typically a few days to a few weeks. Transient expression is suitable for small-scale production, quick screening of various expression constructs, or producing small amounts of protein for research purposes. mAbs may be expressed using transient expression to perform downstream development while waiting to obtain stable clones with high productivity.
  • Stable expression involves the integration of the gene of interest into the host cell genome, resulting in long-term expression of the protein. A stable cell line can be used for larger-scale production of recombinant proteins, including monoclonal antibodies, for therapeutic or commercial purposes. Developing a stable cell lines requires more time and effort for the selection of the desired cell lines but is compliant with future scale-up and GMP manufacturing of the monoclonal antibody.

There is no ideal monoclonal antibody production system. The answer to this question depends on several factors, such as the production scale, desired antibody properties, and the intended application. Here are some commonly used monoclonal antibody production systems:

• • Mammalian cell culture systems: Mammalian cell lines, such as Chinese hamster ovary (CHO) or human embryonic kidney (HEK) cell lines, are widely used and remains expression system of choice to produce therapeutic mAbs. This expression system allows to perform post-translational modifications and produce correctly folded and functional complete antibodies. However, viral safety must considered while using mammalian cell lines.
  • Bacterial expression systems: Bacteria such as Escherichia coli (E. coli) are commonly used for producing small fragments of antibodies that do not require post-translational modifications. Bacterial expression systems are cost-effective and easy to use.
  • Yeast expression systems: Yeast such as Komagataella phaffii (also known as Pichia pastoris) is often considered as an alternative to bacteria to produce therapeutic antibodies and fragments. mAb fragments are secreted into the culture supernatant while using yeast expression systems. Yeast expression systems offer advantages such as low cost, high yield, and fast production times.