Therapeutic proteins are proteins that have been specifically engineered and produced for pharmaceutical use. The can take many forms, for example: enzymes, clotting factors, hormones, cytokines, antibodies and vaccines. More than 100 such proteins have now been approved for use in human medicine as a treatment of a number of conditions, such as: Cancer, Hemophilia, Anemia, Infectious diseases and Autoimmune diseases. Traditionally they are made in specific host cells (e.g. bacteria, yeast, plant or mammalian) by using recombinant DNA technology. Although successful, the generally low volumes and high costs associated with production does limit the number of proteins that can be produced and successfully sold commercially using this approach. This is particularly true for large and complex proteins that need to be produced in mammalian cells.
For a more than 10 years it has been known that milk or eggs rich in specific therapeutic proteins can be produced by transgenic animals or fowl. Such an approach offers the means to produce higher volumes, reduce costs, and thus open up the possibility of commercially producing a much wider range of therapeutic proteins. Since it was first shown to be possible, the techniques and processes used have been gradually improved. As a result, therapeutic proteins that were produced by a number of different transgenic animal approaches have now been successful in gaining regulatory approval for use in humans in both the European Union and the USA. The first, an antithrombin produced in goats (ATryn™) was first approved in 2006 and 2009 respectively, and since then a further two have also been approved, a C1 esterase inhibitor produced by rabbits (Ruconest™), and an enzyme therapy that is produced in chicken eggs (Kanuma™).
As a result of these successes, an established regulatory framework to approve therapeutic protein produced using transgenic approaches is now in place in both the EU and USA. Researchers at the Roslin Institute have for a number of years being perfecting an approach (originally developed for human gene therapy), to produce transgenic hens that can lay eggs that are rich in a specifically targeted therapeutic protein. Through Roslin Technologies, the approach is being developed as a platform that will offer the means to produce a large number of different proteins, for example a Fc conjugate of colony-stimulating factor (CSF)-1, which is currently in production. The Avian Biopharming platform is based around a process of developing transgenic hens using Lentiviral vectors. Much of the basic research work that underpins its development is still on-going at the Roslin Institute, and uses the resources available at the National Avian Research Facility (NARF). For more information on the underpinning and ongoing research can be found at: http://www.narf.ac.uk/about/index.html