Antibodies

The goal of the humanisation process is to maximise the retention of antibody activity whilst minimising the non-human content of the antibody.  The final humanised reagent can be indistinguishable from a naturally occurring human antibody, and is suitable for use in patients.

Within UCB, the high-potency antibodies identified by SLAM and originally isolated from animal cells are humanised for therapeutic use. In humanisation the binding regions (CDR's) of the non-human 'donor' antibody are transferred or 'grafted' onto a human antibody 'acceptor' framework.

Antibody protein expression

At UCB there are two alternative ways of producing antibodies. Small antibody Fab' fragments are normally generated in bacterial systems, for example, E.coli, whereas the larger, more complex, whole antibodies are made in mammalian cells.

Bacterial expression of antibody fragments

Antibodies have a modular structure making them amenable to protein engineering. The full length antibody cannot be made efficiently in bacteria, however the smaller Fab' fragment (~50kDa) which contains the antigen (target) binding site can be made in bacteria at industrial scale.

The genes encoding the Fab' fragment can be introduced into bacteria which are then grown in large scale fermentation vessels and 'induced' to produce the Fab' protein. 

Following extraction and purification, these Fab' fragments have a number of advantages including:

• they only have one binding site which means they can have very specific interactions with the target molecule.
• they lack certain regions that could have the potential to modulate functions within the immune system.
• they offer considerable flexibility since two or more Fab' fragments can be linked and cytotoxic drugs or radioactive chemicals attached.
• the Fab' itself has a relatively short half-life in the body but this can be extended by the specific attachment of PEG (polyethylene glycol). PEGylation of proteins increases their molecular size and generally confers increased half-life in the circulation, as well as potentially reducing immunogenicity and increasing solubility.  The half-life of the Fab' fragment can be tailored according to therapeutic need by the addition of different sized PEG moieties.

Mammalian cell expression

Once an antibody gene has been engineered and manipulated to incorporate its best characteristics it is inserted into one of our proprietary expression vectors. These vectors carrying the antibody gene are placed into host cells to form an appropriate cell line. This cell line is chosen to maximise the levels of expression and quality of the final antibody. Following the isolation of the chosen cell line, antibody manufacture can be scaled-up. UCB can manufacture up to a 100 litre scale internally. Supernatants from these cell lines are used to extract and purify the final antibody.

Antibody protein sciences

UCB's selection of antibody-based drug candidates is based upon a variety of biological and biophysical characteristics.

A significant characteristic of a successful biological drug is its ability to remain stable when stored and to retain its qualities. Early in the drug discovery process UCB selects the most appropriate molecule to address these points. Some of the techniques used include a combination of structural biology, X-ray crystallography, high field NMR, with biophysical analyses such as microcalorimetry and fluorescence studies.

BioProcessing

BioProcessing is the science by which novel antibody drugs discovered in the laboratory are made available to patients at the appropriate scale, cost and quality (purity, strength, activity). It includes cell culture, fermentation, purification, formulation and analytical technologies involved in developing manufacturing and testing procedures for the supply of new antibody medicines for non-clinical and clinical studies. These procedures need to be robust, reproducible, and ultimately compatible with large-scale commercial manufacture of the medicine. Therefore, UCB puts considerable effort into optimising its bioprocess platforms (bacterial and mammalian production systems) using in-house facilities up to 300 litres in scale. UCB will then work with contact manufacturing organisations (CMOs) at 1000 to 15000 litre scales for clinical and commercial supply of the antibody drugs.