hES cell patents in Europe – the inescapable Brustle trap?

The patentability of inventions relating to human embryonic stem cells (hES cells) is currently an area of controversy in Europe. This article examines which hES cell claims the European Patent Office (EPO) is prepared to grant, with reference to a recent decision from the EPO Opposition Division on the Brustle patent.

Inventions which use human embryos for industrial or commercial purposes are considered unethical and so are not patentable in Europe. The controversy lies in whether inventions which use hES cells obtained from established cell lines are patentable. It is important to understand that at least until recently, the process of making an hES cell line involved the destruction of a human embryo to obtain the originator hES cells. Industry generally believes that inventions involving hES cells from established hES cell lines should not be excluded from patentability because they do not involve further destruction of a human embryo. 

The European Court of Justice's (ECJ) decision in the now infamous Brustle case, handed down in October 2011, disagreed. This indicated that an invention is excluded from patentability: “where the technical teaching which is the subject-matter of the patent application requires the prior destruction of human embryos… whatever the stage at which that takes place.” This has been interpreted as meaning that use of hES cells from established cell lines obtained by so-called “destructive methods” is not patentable. 

It is now possible to obtain hES cells without destroying human embryos. Non-destructive methods are described in Chung’s 2008 paper (Cell Stem Cell, Volume 2, Issue 2, 113-117, 7th February 2008), and possibly were available as early as 2006 (Klimanskaya, I et al, Nature, 2006, 444:481-485). However, the EPO is currently using the 2008 cut-off date, and whether a patent was filed pre or post-Chung is decisive in determining patentability at the EPO.

So what type of claim is the EPO willing to grant for hES cell inventions? In some pre-Chung patent applications, EPO examiners have asked for the removal of excluded subject matter from the claims by inserting a disclaimer along the lines of “with the proviso that [the invention] does not use hES cells that have been obtained by destruction of a human embryo”. 

However, doubt has now been cast on the disclaimer approach for pre-Chung cases by the EPO Opposition Division’s decision on the Brustle patent handed down in June 2013. By way of background, Brustle is trying to claim methods of generating neuronal cells starting from mammalian ES cells, which may be hES cells. The patent was filed in 1998 so the originator hES cells were produced by the destruction of a human embryo. During prosecution at the EPO, Brustle amended the claims at the Examining Division’s request to include a disclaimer excluding methods involving the destruction of a human embryo. The patent granted, but the claims were opposed post-grant. 

The EPO found that the disclaimer was bad because it added matter, and so revoked the patent. The disclaimer meant that insofar as the claim related to hES cells, it now related solely to hES cells produced by non-destructive methods. This resulted in an added matter rejection because:

• This was a new sub-group not disclosed in the application as filed, contrary to Decision G2/10 of the EPO Enlarged Boards of Appeal.
• This new sub-group could not be obtained at the filing date without an inventive step, and so the disclaimer was relevant to sufficiency and inventive step, contrary to Decision G1/03.     

There is a suggestion that the EPO considered that a disclaimer was not necessary at all in the Brustle patent. Referring again to G1/03, the EPO indicated that a disclaimer is inappropriate in situations where the application discloses suitable and enabled alternatives over the claimed range. It viewed ES cells from mice, rats and hamsters disclosed in the patent as suitable alternatives and stated that the claimed subject matter is sufficiently disclosed because the examples demonstrate that the claimed methods can be carried out using ES cells from mice. The EPO appears to be suggesting either that the patent should have been limited to these alternatives rather than introducing a disclaimer or, more interestingly, that the broad mammalian claims could stand, although it is not entirely clear which.

The EPO Opposition Division’s decision represents an interesting interpretation of G1/03, and to an extent G2/10, and other EPO Opposition Divisions and Examining Divisions are not bound to follow it. Brustle has until September to appeal; if this happens, more definitive case law will be formed by the EPO Board of Appeal. 

If this decision is followed, it is bad news for pre-Chung EPO hES cell patents which have been amended to include undisclosed disclaimers to hES cells made by destructive methods. The problem is that any patents which grant or have granted with such a disclaimer may be caught in an inescapable trap if the disclaimer is found by the EPO to add matter but it is not possible to remove it without extending the scope of protection post-grant. Such patents would be invalidated before the EPO. A different outcome may be obtained if the patent gets past its European opposition period, and is instead litigated in the national courts. For example, in Germany, the Federal Court of Justice has found that the disclaimer added in the pre-Chung Brustle patent does not add matter. The UK courts, however, are increasingly looking to EPO case law to make their judgments and so may be more likely to follow EPO decisions in this regard.   

It is less clear whether the EPO’s added matter rejection would be raised against a disclaimer that has been added in a post-Chung case. Interestingly, in some post-Chung patent applications, the EPO examiners have not asked for a disclaimer to be inserted into the claims; instead, claims are merely required to specify that any examples that relate to hES cells obtained by destructive methods are reference examples. This approach is apparently deemed acceptable because non-destructive methods of producing hES cells were available at the filing date of post-Chung cases and so hES cells were not “exclusively” obtainable by destructive methods. Therefore, it is safest to leave disclaimers out of both pre and post-Chung cases.

However, the question remains: can a patent holder actually stop a third party from using hES cells, or is there freedom to operate in Europe?