Regulators in Europe have ruled against permitting a patent on developing human embryonic stem cells (hESCs), a move which could represent a major blow to companies working commercially in this area.

An appeals board at the European Patent Office has upheld a decision made in June to reject a patent application regarding the use of stem cells filed by the Wisconsin Alumni Research Foundation in 1995. The office confirmed that “European patent law prohibits the patenting of human stem cell cultures whose preparation necessarily involves the destruction of human embryos”.

The European Patent Convention (EPC), the legal basis for the EPO, already has a ban in place on the patenting of inventions “whose commercial exploitation would be contrary to public order or morality”, and specifically prohibits patents on uses of human embryos “for industrial or commercial purposes”.

The EPO ruling could apply to as many as 200 similar inventions pending in Europe, though the agency noted that the decision “is not concerned with the general question of human stem cell patentability”. As such, the ruling is being regarded as damaging only to WARF, which said that it is “considering various options in response”. However WARF noted that the decision does not affect its patents in the USA, which were upheld in March by that country’s Patent and Trademark Office.

The EPO decision prompted a response from the USA’s Geron Corp, which is also active in the stem cell field. The firm’s chief patent counsel, David Earp, said that “while this result is not unexpected given the language of the EPC rule, given the narrow basis for the decision, it should have very limited impact on Geron’s ability to protect our hESC technologies in Europe”.

He added that “the facts underlying the decision are specific to the WARF patent application and, importantly, the EPO did not rule that hESC technologies in general are not patentable in Europe. Mr Earp concluded by saying that “e are optimistic that the EPO will now move to allow the backlog of Geron’s European patent applications that have been on hold pending this decision”.