Tag Archive for: Transient Gene Expression

Waving goodbye to antibody engineering and moving your lead candidates into transient protein expression is a big milestone in therapeutic antibody development. Wise developers budget a few weeks into their timelines to invest in a small-scale pilot project before scaling up.

One of the biggest decisions which any company developing biological medicines makes is to move forward to the manufacture of their product.
This can be one of the most costly and complex decisions you take, and it is vital to get this right. What technology should you use, who should you partner with, how long will it take? The first point in the journey to your first clinical batch is the creation of a cell line expressing your product. This cell line will be used to manufacture all the product you will need to support in–vivo demonstration of biological activity, demonstrate safety, set a pharmacological dose, and ultimately treat all your patients. This cell line will likely remain through the whole lifetime of your product, remaining unchanged through clinical trials and onto the market.

However, cell line development is a very specialised and complex activity and it can be difficult to navigate the huge variety of choices available. Your choice of cell line and expression platform will influence the efficacy and safety of your product, the cost of goods and the ease of manufacture.
How do you balance safety, cost of producing your cell line, the commercial cost of your product and time in the race to start clinical trials?
When making this difficult decision we find it useful to focus on what is most important first – namely regulatory acceptance. The regulatory guidelines applying to cell line development are clear and easy to interpret. Regulators expect clearly documented history and testing for cell lines producing biologic medicines – so this should be sought.

The second key focus is to check that the expression level of the cell line is commercially viable. Low cell line productivities become increasing important as you progress through clinical testing. The further you are in the clinical pathway the more expensive and time consuming it becomes to replace your original cell line. Complex bridging studies can be required with no guarantee of product being comparable between cell lines. You should look for expression data for multiple different molecules and ask for detailed examples of success. Aim for at least 3 g/L in your upstream process – preferably higher.

Thirdly the time to construct a cell line should be evaluated as cell line development is almost always on the critical path to the production of your first clinical batch. Six months or less should be easily achievable.
Only finally should you consider cost – cell line development is one of the largest elements in a chemistry, manufacturing, and control (CMC) project and it can be tempting to seek lower cost options. However, ensure that project scopes are comparable between suppliers, ensure that everything you need for your regulatory submission is included and ask for examples from previous projects.

At Fusion Antibodies, we guide our clients through this complexity by ensuring that we offer them confidence and flexibility supporting their clinical development. We are well placed to provide rapid development of well characterized mammalian cell lines with a good clinical record.


Dr Jonathan Dempsey

Jon is the Managing Director of Dempsey Consulting and a founding Partner of Pathway Biopharma Consulting. Jon has a degree in Biotechnology and a PhD from the University of Edinburgh.

With almost thirty years’ experience in the development and manufacture of biologics, with companies such as Lonza Biologics, Cambridge Antibody Technology and Invitrogen, Jon has deep knowledge in the Chemistry, Manufacture and Control for biologics and in the application of innovative technologies impacting this field. Jon also offers specialist expertise in cell line development, upstream process development, process intensification and cell culture medium development.


Therapeutic antibodies have revolutionized the treatment of numerous diseases, but not every antibody has what it takes to become a licensed medicine. Finding a high-affinity antibody that binds to your target is only the first step. The ideal therapeutic antibody must have good efficacy, safety, pharmacokinetics (PK) and stability, and in addition, be easy to manufacture to ensure commercial viability.

Safety first

Safety is the first requirement for any medicine, and this is no different for therapeutic antibodies. Perhaps most importantly, a good therapeutic antibody should bind to its target with high specificity. For example, an antibody that is designed to target tumour cells should ignore healthy cells, as off-target binding might lead to unexpected side effects.

It’s also crucial to fine-tune the antibody’s affinity – how tightly it binds to its target. If the affinity is too low and the antibody binds its target only weakly, the therapeutic effect may not be achieved. Conversely, if the affinity is too high, the antibody dose could be “used up” too quickly, and the likelihood of off-target activity might increase.

Another important step is to minimise the risk of the antibody generating an immunogenic reaction. If an antibody is unstable, it can aggregate, misfold or even give rise to potentially dangerous metabolites such as charge variants (which occur when an amino acid has been oxidised or deaminated). These seemingly minor changes can render an antibody immunogenic, as well as reducing its efficacy.

Optimising efficacy and PK

When it comes to optimising the efficacy of an antibody, one of the major challenges is fine-tuning its affinity. The antibody needs to have sufficiently high affinity to ensure that it works as intended, but not high enough that it binds to off-target molecules and causes unintended side effects. In some cases, reducing the antibody’s affinity might actually increase its functionality, particularly in the case of multi-specific antibodies that bind two or more antigens at once (1).

Therapeutic antibodies also need to be delivered efficiently to where they’re needed in the body, and hang around for long enough to have an effect. At the same time, there should be a focus on minimising the number of doses the patient requires. The PK of the antibody can be optimised by careful screening for liabilities in its sequence that could, for example, make it unstable, meaning greater and more frequent doses are required.

Cost of goods

With increasing numbers of approvals, the therapeutic antibody market is getting crowded and competitive. Healthcare payers need to control costs, a pressure that is passed onto manufacturers. Thus, cost control should be part of every antibody development programme from the beginning.

Optimising antibody expression and considering the “manufacturability” of antibody sequences is fundamental to developing any therapeutic antibody, and ultimately also has an impact on cost. A functionally perfect antibody that becomes overly modified or degraded during large scale manufacture will not make it to the clinic. For example, manufacturability can be affected by free cysteines, formation of interchain disulphide bond formation and aggregation. Less dramatic self-interaction may still only be evident at the high concentrations required for a clinical production batch.

Stability is another cost factor. Optimizing the antibody for longer shelf life and reducing the need for cold storage can help to keep costs down.

Help from a trusted partner

Fusion Antibodies’ rational affinity maturation platform – RAMPTM – produces functional antibodies that are optimised to jump the hurdles littering the path to the clinic, helping to control costs along the way. Rational library design reduces the risk of sequence liabilities and the downstream risks of aggregation and immunogenicity (2). This can increase yield, optimise affinity and promote stability. The best candidates are screened out in silico from the library and expressed in mammalian cells for further characterisation – including manufacturability.


1 Mazor, Y., Sachsenmeier, K., Yang, C. et al. Enhanced tumor-targeting selectivity by modulating bispecific antibody binding affinity and format valence. Sci. Rep. 7, 40098 (2017).

2 Tabasinezhad, M., Talebkhan, Y., Wenzel, W. et al. Trends in therapeutic antibody affinity maturation: From in-vitro towards next-generation sequencing approaches. Immunol. Lett.212, 106–113 (2019).