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Logo of bmjThis ArticleThe BMJ
BMJ. 2007 June 23; 334(7607): 1294.
PMCID: PMC1895663

Scientists plead for right to create interspecies embryos

A leading body of medical scientists has concluded that the creation of interspecies embryos, which are part human and part animal, is vital in the fight against a wide range of diseases.

The Academy of Medical Sciences says there are no “substantive ethical or moral” reasons why research on human embryos containing animal material should not be carried out under exactly the same regulatory framework that exists for other work with embryos.

This stipulates that no modified embryos should be reimplanted into a woman or animal and that none should be grown in vitro beyond 14 days.

The academy set up a working group of leading doctors and geneticists in March to examine the situation after the government's white paper, which proposed a blanket ban on all interspecies embryo research (BMJ 2007;334:12 doi: 10.1136/bmj.39080.500648.DB), and a public consultation on hybrid research by the Human Fertilisation and Embryology Authority (BMJ 2007;334:925 doi: 10.1136/bmj.39199.669907.DB).

The government later modified its position, in its draft Human Tissue and Embryos Bill, to allow some limited forms of interspecies laboratory work while still opposing the creation of true hybrid embryos, in which human sperm is mixed with animal eggs or vice versa (BMJ 2007;334:1074 doi: 10.1136/bmj.39222.535255.BE).

But the working group sees no reason why this type of research should be banned. Its chairman, Martin Bobrow, said it had found no scientific reason why researchers would need to generate true hybrid embryos.

“However, given the speed of this field of research, the working group could not rule out the emergence of scientifically valid reasons in the future.”

Interspecies research is an increasingly attractive option for many scientists because it overcomes the shortage of human eggs available for research by substituting an animal egg, with its nucleus removed, which acts as host for human cells.

The resulting human-animal embryos are a rich source of stem cells, which can be used to study diseases from developmental abnormalities in young children to cancer and Parkinson's disease as well as to help to develop new drugs.

Two teams of scientists, at Newcastle University and King's College, London, have applied for a licence from the Human Fertilisation and Embryology Authority to fuse animal eggs with human cells to make embryos that would be 99.9% human and 0.1% cow or rabbit.

The report accepts that many members of the public experience a “yuck factor” about interspecies embryos because they think it breaks a fundamental taboo. But this argument is difficult to sustain, it says, noting that many medical advances such as in vitro fertilisation, vaccination, and antibiotics involve manipulation of nature.

The Human Tissue and Embryos Bill is being scrutinised by parliament but is not expected to become law until next year.

The government has reiterated its stand against true hybrid embryo research in its response to the report of the Commons' science and technology committee on regulating interspecies embryo research.

Although the government accepts that some forms of human-animal embryo research should be allowed, it draws the line at true hybrids, in which human sperm is mixed with animal eggs or vice versa. This, it says, is “not acceptable.”

At the same time the government accepts that the draft Human Tissue and Embryos Bill gives parliament the scope to allow the creation of true hybrids through secondary legislation “in the light of evidence that they are necessary.”

In its report in April the science and technology committee called for legislation to allow regulation of research using animal-human hybrid embryos through licensing, warning that vital research work would otherwise be threatened.

Phil Willis, the chairman of the committee, said this week that he was disappointed that the government had not taken a more permissive approach or given a clearer indication of how it would take the matter forward.

He was also concerned that the government had rejected the committee's proposal for a parliamentary standing committee on bioethics, favouring instead a “flexible and future proof” regulatory system combined with some degree of parliamentary involvement.

“There remain issues of principle regarding the role of parliament and the role of the regulator that need to be clarified and we look forward to hearing from the government on how it intends to do that,” he said.

“Until we have such clarification there can be no certainty for scientists that they will be able to apply for licences for this vital work.”

An all party parliamentary committee, also chaired by Mr Willis, is scrutinising the draft bill and is due to report back by 25 July.


The academy's report is available at

The full text of the government's response is at

Articles from The BMJ are provided here courtesy of BMJ Publishing Group