Transgenic Animals in Pharmaceutical Production
Jeroen Breekveldt and Joost Jongerden
||Transgenic animals for pharmaceutical production; Drugs
(human); Vaccines (human); Genetic engineering.
||Breekveldt, J. and Jongerden, J. (1998), "Transgenic Animals
in Pharmaceutical Production." Biotechnology and Development Monitor,
No. 36, p. 19-22.
The production of pharmaceutical human proteins in transgenic animals
is still a minor business, in which only a few companies are involved.
After ten years of research, no product has yet reached the market but
the stewards of this technology hope to achieve this within the next couple
of years. Currently, most research is directed towards products for industrialized
A transgenic animal is by definition an animal whose genetic composition
has been altered to include selected genes from other animals or species
by methods other than used in traditional breeding. In other words, an
animal altered by the introduction of recombinant DNA through human intervention.
The first transgenic animal was a mouse, created in 1981, carrying a gene
which made the animal susceptible to cancer. The first transgenic farm-animal
was a sheep created in 1985. Biotechnology firms and research institutes
involved in pharmaceutical development and production use transgenic animals
for three different ends.
This new branch of transgenic animal production which has emerged in recent
years has a new name: pharming. Pharming is the production of pharmaceutical
human proteins in transgenic farm animals.
As a research model. An example is the modification of the genetic
make-up of an animal in such a way that it develops a disease close to
that of human beings. The animal is thus used as a model to see how a disease
develops and reacts to drugs.
As a test kit. An animal can be genetically modified to make a human
protein. When this protein produced by an external source is applied to
the transgenic animal, the immune response of the animal is an indication
of the purity of the protein to be tested.
As a pharmaceutical production unit. Via transgenic technology such
as micro-injection, genes that code for the production of a human protein
are inserted into the genome of an animal, which in turn produces the human
In most cases of pharming, changing the composition of milk is the
main strategy. Mammary glands of cows produce large volumes of milk, a
protein-rich solution which can be collected non-invasively. In October
1997, Nature Biotechnology reported on the achievement of producing
a biologically active human protein in the milk of a transgenic pig. This
demonstrated the feasibility of producing large and complex proteins in
this way. However, it remains difficult to generate animals which produce
these medical proteins of a consistent quality and in sufficient quantities.
If a successfully engineered transgenic animal can be cloned, and then
bred successfully, it will be possible to create herds of these animals
for pharmaceutical milk products of identical quality.
Research also extends to areas other than milk. The Agricultural
Research Service of the United States Department of Agriculture
(USDA) has developed mice which produce stable amounts of human growth
hormone in their urine. The researchers see some clear disadvantages of
milk based pharmaceutical protein production: firstly, lactation occurs
only in females and is non-continuous; secondly, for cows it takes at least
24 months before lactation starts. Finally, milk is a complex substance
usually containing 3 to 6 per cent total protein and therefore needs extensive
purification to obtain the pharmaceutical protein. Purification of urine
seems to be easier, according to the USDA research.
Old and new transgenic techniques
The first successful pharmaceutical products employing genetically
engineered organisms were protein drugs like human insulin (1982) and human
growth hormone (1987). These drugs are manufactured in cell cultures employing
genetically modified bacteria in bioreactors. However, bacteria and other
micro-organisms cannot produce the more complex human proteins. For this,
higher organisms like mammals are needed.
The use of transgenic livestock in protein production aims at overcoming
several major barriers presented by cell-based systems. Potentially, this
approach could provide large quantities of complex proteins in a cost-effective
way. Compared to the facilities and chemicals required for cell culture
production, capital investment required for animal production facilities
is relatively low. The British company PPL Therapeutics (PPL) estimates
that the basic costs for products developed by transgenic animals are four
to five times lower than cell culture production. However, this does not
take into account development costs. To date, the use of transgenic animals
is developing fast for a range of pharmaceutical products. (see
|R&D of medicine production by transgenic
|alpha1 anti trypsin (AAT)
||deficiency leads to emphysema
|human protein C
|tissue plasminogen activator (tPA)
|GI tract infection,
|antithrombin 3 (ATIII)
|glutamic acid decarboxylase
||type 1 diabetes
|human serum albumin (HSA)
||maintains blood volume
Actors and products
The main actors involved in pharming are three new biotechnology firms:
Genzyme Transgenics Corporation (GTC) in the USA, PPL in the UK
and Pharming Group in the Netherlands. GTC was the first company
that successfully completed a second phase clinical trial for the pharming
drug Antithrombin 3 (ATIII). The drug is used for treatment of thrombosis
and is currently extracted from blood plasma. GTC will produce ATIII using
transgenic goats and sees market opportunities for the protein in many
healthcare areas. GTC expects to market the product by the year 2000.
The first pharming drug expected to be approved for sale, however,
is human alpha glucosidase. This is a drug against Pompe disease,
a rare neuro-muscular disease. It is produced by Pharming Group using transgenic
rabbits. The fact that this drug is expected to be approved before ATIII,
which was developed earlier, is due to the Orphan Drug Act. Orphan Drugs
(OD) are drugs for rare diseases. OD status is granted by the Food and
Drug Administration (FDA). By giving OD status, health authorities
aim to stimulate pharmaceutical development for drugs with small markets.
Although OD need to complete the clinical phase III trials successfully
like any other medicine, these drugs do not have to be tested on thousands
of people. Instead, OD need testing on only several tens of people to receive
market-approval. For starting pharmaceutical companies OD can be a good
opportunity to generate income quickly.
Another promising substance for commercial production by transgenic
animals is Human Serum Albumine (HSA). To serve the world market
of about 5,500 cows would be sufficient to replace the currently plasma-derived
HSA, assuming one cow produces 80 kg of protein a year in its milk, as
However, transgenic cows producing HSA do not exist at the moment.
GTC has developed only transgenic mice producing HSA in their milk. Nevertheless,
GTC initiated a related collaboration with the UK-based company Advanced
Cell Technology (ACT) for the development of cloned, transgenic cows.
GTC has exclusive, worldwide rights to ACT`s cloning technology for the
production of biopharmaceuticals in the milk of transgenic cows. In January
1998 ACT announced it had cloned three transgenic calves using the technique
applied by the Roslin Institute for production of Dolly the
sheep (see box).
Pharming Group was founded by Leiden University in the Netherlands,
which still has shares in the company. Pharming Group is developing several
pharmaceutical proteins. In agreement with the American Red Cross
(ARC), Pharming Group will use ARC’s technology and patents to produce
blood compounds such as factor VIII (hemophilia A), factor IX
(hemophilia B) and fibrinogen (clotting protein) in the milk of
cows and pigs. These plasma proteins are expected to be on the market within
six to seven years.
Within 20 years the whole production of blood products, currently derived
from pooled human blood, might be transferred to pharming production, according
to Pharming Group’s vice president G. van Beynum. Health risks and
accidents caused by the transmission of Human Immunodeficiency Virus
(HIV) and hepatitis have stimulated the search for alternatives. At the
development phase Pharming still requires screening for diseases transferable
from animals to humans. This possibility has become obvious by the outbreak
of diseases like Bovine Spongiform Encephalopathy (BSE).
PPL was established to commercialize the work of the Roslin Institute,
a public pharmaceutical research institute in Scotland. PPL mainly uses
sheep, but goats, cows and recently pigs and rabbits are also used for
pharming. The company produces alpha 1 anti trypsin (AAT) in the
milk of transgenic sheep. The first and best-known sheep to produce pharmaceuticals
is called Tracey (see box), and was bought by
the German pharmaceutical company Bayer for US$ 17 million. Currently
PPL owns a herd of 300 sheep, which are worth over US$ 100 million,
and which produce AAT as a drug against cystic fibrosis. AAT has recently
been granted OD status in the US.
Moreover, PPL holds a patent on the nuclear transfer cloning technique
by which the clone Dolly was made. Although PPL vowed they will never clone
human beings, the patent does not exclude humans. Dolly the sheep is the
first mammal to be cloned from an adult cell. The ability of clones to
produce healthy offspring is important for commercialization of the nuclear
transfer technique which produced Dolly.
Not all new biotechnology firms have the same strategy for commercialization.
PPL, for example, supplies technology to other companies. PPL can be considered
as a technology platform for companies such as Bayer, Boehringer Ingelheim
(Germany), Novo Nordisk (Denmark) and American Home Products
(USA). Pharming Group, on the other hand, intends to become a pharmaceutical
company itself. GTC takes a middle position because it markets some pharmaceuticals
itself, but also contracts partners to market other products.
• Tracey was the first transgenic sheep to produce
human protein in its milk (AAT), PPL produced Tracy in 1991 using
micro-injection for the transfer of human genes.
• Dolly was the first mammal ever to be produced
using a cell of an adult sheep, a technique not considered possible before.
At the Roslin Institute in Scotland, the cell material was extracted from
the udder of a 6-year old sheep and transplanted into an emptied egg cell.
Dolly was born in 1996. In 1998, Dolly gave birth to a lamb called Bonny,
proving that clones are able to produce healthy offspring.
• In 1997, PPL announced that Polly, a genetically
engineered lamb, had been produced by the same method of nuclear transfer
that had produced Dolly. In addition to her usual complement of sheep genes,
she also contained a human gene which had been added to the cells while
they were still a cell culture. Polly produces a pharmaceutical protein
in her milk.
Animal husbandry and welfare
The production of pharmaceuticals by transgenic animals is not likely
to have a big impact on animal husbandry in general. Since the number of
transgenic animals which will provide pharmaceutical proteins for the world
market is limited to several thousands, pharming is expected to become
a separate area of animal production. According to P. Brascamp of
Wageningen Agricultural University in the Netherlands, pharming
will be part of the pharmaceutical production chain.
Animal welfare groups, and those concerned about ethical implications
of biotechnology, question the development and use of transgenic animals.
Cloning can involve invasive procedures to harvest eggs. A number of cloned
animals have developed malformed internal organs. Animal welfare groups
fear that any herd of cloned animals used in agriculture would be vulnerable
to diseases because of the reduced gene pool from which they were drawn.
Animal welfare groups like Compassion in World Farming along with
the British Union for the Abolition of Vivisection therefore have
lobbied the British government to ban animal cloning.
Pharming for developing countries
Most of the pharmaceutical industry’s revenues are derived from sales
of drugs in the industrialized countries. By far the majority of these
drugs are targeted towards "diseases of affluence" such as heart diseases,
ulcers and depression. Could pharming provide treatments for diseases such
as malaria, tuberculosis and cholera? According to the Netherlands’ biotechnology
industry association Niaba, the return of investment for the drug
development of such diseases would be too low, given the low-income markets
for such drugs. On the other hand, if deals could be made between United
Nations (UN) organizations such as the World Health Organization
(WHO) or the United Nations Industrial Development Organization
(UNIDO) and pharmaceutical or pharming companies, drugs could be provided
at lower prices under certain conditions. Such a deal was made between
Glaxo Wellcome (UK) and the Joint United Nations Program on HIV/AIDS
(UNAIDS) to provide the Anti AIDS drug AZT for 30 per cent of the market
price (see Monitor
Perhaps the most promising for developing countries is GTC`s research
on malaria. 300 to 500 million people are infected with malaria and 2 million
people die of this disease annually. GTC developed a malaria antigen, MSP-1,
in the milk of transgenic mice. This was part of GTC’s collaboration with
the American National Institute of Allergy and Infectious Disease
(NIAID) for the production of transgenic recombinant malarial proteins
for use in malaria vaccines.
Jeroen Breekveldt/ Joost Jongerden
Working Group Technology and Agrarian Development, Wageningen Agricultural
University, Nieuwe Kanaal 11, 6709 PA Wageningen, the Netherlands.
E-mail email@example.com firstname.lastname@example.org
press releases Pharming Group
Nature Biotechnology, October 1997
Personal communications with G.M.A. van Beynum (Pharming Group)
and P. Brascamp (Wageningen Agricultural University).
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