Dozens of medicines in use today and many more in development are not made by traditional methods. They are not chemically synthesised or fractionated, but produced using mammalian cells. Such medicines include vaccines, hormones, monoclonal antibodies, anticancer agents, growth factors and Factor VIII for the treatment of haemophilia.

The types of cell used in the manufacture of such biopharmaceuticals are derived from many types of mammal, including hamsters, mice, non-human primates and humans. However, a common feature of many cell culture systems is the use of albumin, derived either from humans or cows, due to its ability to mimic the environment these cells originally lived in.

Large market
The market for human and bovine serum albumin is large. Svend Petersen of Biotech Business Development at Novozymes says: “We estimate that tens of tons of bovine serum albumin and human serum albumin are produced annually for use as cell culture ingredients. However, drivers in the market (see below) will gradually force biopharmaceutical companies to move away from these products unless they can be supplied as safe recombinant products, and this is just what we believe we can do.

“Globally more than 500 biopharmaceut­ical products are in the development pipeline, and a substantial number of these may benefit from adding serum albumin to the cell culture medium,” says Svend Petersen.

 

Human serum albumin

Human serum albumin, which is produced in the liver, is the most abundant protein in human blood plasma and fulfils a number of the body’s requirements. These include maintaining the osmotic pressure needed for proper distribution of body fluids, as well as serving as a transport system for other molecules such as hormones, lipids, vitamins and ions. It also has a number of uses as a cell culture medium ingredient; the most important is to bind and stabilise several of the molecules and ions found in such systems. It also acts as an antioxidant and transporter of essential molecules to and from the cells. In addition, it stabilises the products produced and prevents these from sticking to the sides of vessels and other surfaces.

Recombinant technology
It is important to differentiate between the sources of albumin used for cell culture. Traditionally it has been derived from cows or from human plasma that has been donated. However, over the last decade so-called recombinant human serumalbumin (rHSA) has become available.

Recombinant technology is where the gene for a particular protein - in this case human serum albumin - is inserted into a bacterial, yeast, fungal or mammalian cell; by clever genetic manipulation, the cell can be made to primarily express the desired protein in large amounts, which is recovered and purified. rHSA has a number of safety advantages over that derived from animals, particularly that it will be free from potential pathogens such as viruses and prions; prions are the strange infectious agent responsible for brain diseases such as bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease.

By leveraging its experience in the manufacture of industrial enzymes, Novozymes intends to produce rHSA for mammalian cell culture media from Aspergillus.

Novozymes and rHSA
Novozymes took its first steps into the rHSA arena by applying the recombinant technology platform developed for enzyme production to HSA production. The company is now producing rHSA in the fungus Aspergillus at lab scale and the success of this project has led to several other initiatives. These include the acquisition of Delta Biotechnology Ltd (now known as Novozymes Delta Ltd) and the establishment of a partnering agreement with Celliance, in order to provide samples of Novozymes’ in-house rHSA to potential customers.

Charlotte Hummer Vad, also of Biotech Business Development, is involved in the integration of Novozymes Delta Ltd. She says: “Delta Biotechnology is a UK-based technology company that researches, develops and produces microbially produced recombinant proteins. Its lead compound is called Recombumin,® which is a highly purified and FDA-approved form of rHSA.

“The difference between Recombumin and Novozymes’ in-house product is that Recombumin can be used as an excipient whereas Novozymes’ in-house product is intended for use in mammalian cell culture media. An excipient is a molecule that can stabilise the active pharmaceutical ingredient and protect it from degradation. Consequently, adding rHSA to biopharmaceutical products may extend the shelf life of the products and make them work with higher efficacy.”

Excipients have to be very pure, especially when one considers that some bio­pharmaceuticals are infused directly into the circulatory system.

Agreement with Celliance
Celliance is a US-based biotech company with five decades of protein fractionation expertise and a focus on cell culture and diagnostic products. It is the world’s largest producer of bovine serum albumin (BSA) with approximately 60% of the global market. Its BSA product, Probumin,® comes in over 40 different grades. However, the company does not have an rHSA product.

Caspar Foghsgaard, who has been working closely with Celliance, explains the purpose of the agreement: “The collabor-ation will focus on how best to bring rHSA to market. Novozymes intends to upscale the manufacturing of its Aspergillus-based rHSA, while we will be looking to the expertise of Celliance to market the product and provide technical service solutions.”

Charlotte Hummer Vad adds: “The acquisition of Delta Biotechnology Ltd and the alliance with Celliance mean that Novozymes will have a strong presence in the biopharmaceutical ingredients market, being able to provide several different grades of rHSA.”

Market drivers
As previously mentioned, substantial amounts of extracted BSA and HSA are being used as ingredients in cell cultures. However, the concern over the transmission of viruses and prions is driving the desire among these companies to remove BSA and non-recombinant HSA from the cell culture media used in the manufacture of their products.

In the manufacture of Factor VIII for the treatment of haemophilia, for instance, companies have gradually switched from BSA to HSA, and now a number are stabilising the FVIII molecules with sugars such as sucrose.

Caspar Foghsgaard says: “The problem with albumin-free processes is that they are not as good as those containing albumin, but companies have been driven to make this change because of fears over the transmission of pathogens. This is particularly so in areas like haemophilia where the patient population was severely affected by HIV in the 1980s and HCV transmission in the 1990s, although it was not the albumin component that was responsible in these cases.

“The obvious solution for the manufacturers of Factor VIII is to use recombinant HSA both in the cell culture medium and as an excipient. rHSA eliminates the worries over pathogen transmission which affect animal-derived HSA.”

The future
The rapid development of cell culture-based medicines that powerfully target specific diseases is an exciting trend in medical science today. This trend means that development is moving in the direction of personalised medicine, with smaller volumes tailored to specific genetic patient profiles.

Hand-in-hand with this trend has been the development of purer forms of rHSA that provide cell culture media with the necessary ingredient to produce large, complex molecules.